View Full Version : The velocity of light
I'm not sure what you mean by "seeing the event of B before A". I presume you mean that the moving observer "sees" the light from B before the light from A. But that depends on: When the light pulses were emitted and where the moving observer is, as well as the speed of the moving observer.
Einstein said in his 1916 book:
”If an observer sitting in the position M1 in the train did not possess this velocity, then he would remain permanently at M, and the light rays emitted by the flashes of lightning A and B would reach him simultaneously, i.e. they would meet just where he is situated. Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A.”
What Einstein means by “he is hastening towards the beam of light coming from B” is that the light beam from the flash at B is converging on the observer that is moving toward B at the relative velocity of c + v, with v being the velocity of the observer toward B. What he means by “he is riding on ahead of the beam of light coming from A” means the light from the A flash is converging on the observer at the velocity of c – v.
This is very simple. The observer-relative speed of the light, relative to the moving observer is NOT “c”, it is NOT constant. It is c + v in one direction and c – v in the other direction.
This is why the earth sees a blueshift in the light of the star the earth is moving toward in its revolution around the sun and this is why the earth sees a redshift in the light of a star the earth is moving away from during its revolution around the sun. This is caused by the Second Cause of the Doppler effects that I told you about earlier. This is a Doppler Law of Physics. It can not be revoked.
David - I do not think your conclusions about what Einstein was saying are consistent with SR - it is true that signals sent from sources you are approaching and those sent from sources from which you are receding will arrive at different times if they are sent when you are midway between them, you would nonetheless in SR measure both signals to have the same relative velocity c with respect to you according to SR.
That you may doubt whether SR is correct in making that postulate is another question - these were Einstein's conventions - but this particular "one way isotrophy" convention does not get tested in most experiments - what we test is over and back effects - the transformation that leads to one way isotrophy (the vx/c^2 term) doesn't appear in the interval - and it is the constancy of the interval that we commonly use to calculate time dilation, length contraction, mass increase etc. The interval can be arrived at without the one-way isotrophy postulate (for example the light clock which we have just rambled through on another thread gives you the (1-v^2/c^2)^1/2 directly, so therefore it is not inconsistent to believe in all the the successes of SR and still have doubts about the necessity and correctness of the second postulate.
Regards. Yogi (One of the cranks)
Note that Einstein is describing things from the point of view of someone on the embankment!
No need to play around with word games or tricky thought experiments with me. That type of stuff doesn’t work on me. I’m talking about “physics”, not “science fiction stories”. And this is a “physics” board, not a “Si-Fi” board.
The reason the guy on the moving train will see the B flash first is because he is moving toward B and thus he and the light beam from B are converging on each other at the additive light-speed velocity of c + v. That’s a basic law of physics and of nature, and it’s a basic Doppler Law. That’s why the guy on the train will see the light as blueshifted, even though the waves of light are not “compressed” in the space between B and the moving observer.
selfAdjoint
May14-04, 03:53 PM
I’m talking about “physics”, not “science fiction stories”.
Good for you.
The reason the guy on the moving train will see the B flash first is because he is moving toward B and thus he and the light beam from B are converging on each other at the additive light-speed velocity of c + v. That’s a basic law of physics and of nature, and it’s a basic Doppler Law.
Oops, you just slid into sci-fi. Your "basic law of physics" is only an approximation, valid at low speeds.
Oops, you just slid into sci-fi. Your "basic law of physics" is only an approximation, valid at low speeds.
Max Born, Nobel Prize winner, writing in “Einstein’s Theory of Relativity”, 1962 edition:
“The fact that the observed frequency of a wave depends on the
motion both of the source of light and of the observer, each with
respect to the intervening medium, was discovered by Christian
Doppler (1842), The phenomenon may easily be observed in the
case of sound waves. The whistle of a locomotive seems higher when
it is approaching the observer and becomes deeper at the moment of
passing. The rapidly approaching source of sound carries the
individual phases of the waves forward so that the crests and hollows
succeed each other more rapidly. The motion of an observer to-
wards the source has a similar effect; he then receives the waves in
more rapid succession.
Now the same phenomenon must hold in the case of light.”
(snip)
Born continues:
"This relation between the frequencies f and f’ shows how the frequency is diminished when the observer has a velocity v in the direction of the light. From (40) and (41) one obtains the obvious result
c’ = c – v"
Born knew this and I know this. All the scientists of the 19th Century and during the first 60 years of the 20th Century knew this.
This is why the earth observes a redshift in the light coming from a star that is fixed relative to the sun, when the earth is moving away from the star as the earth revolves around the sun.
This is a completely different reason than the reason why the earth observes a redshift when the star itself is moving away from the earth. The first reason I gave is due to the c – v effect, as explained by Max Born, the Nobel Prize winner. The second reason is due to the starlight wavelength being physically stretched out in space. Unfortunately, only one reason or cause for the Doppler effects is taught in school today, while the other reason is ignored.
ahrkron
May14-04, 06:11 PM
Born knew this and I know this. All the scientists of the 19th Century and during the first 60 years of the 20th Century knew this.
Some things have happened since then, one would expect.
Born continues:
"This relation between the frequencies f and f’ shows how the frequency is diminished when the observer has a velocity v in the direction of the light. From (40) and (41) one obtains the obvious result
c’ = c – v"
How convenient that you stopped quoting at this point! :rofl:
Just two sentences later, Born goes on to say (emphasis mine):
"But we have chosen a method using the invariance of the number of waves becaused they can be used later in the theory of relativity. There we will see that the relations c' = c - v and λ' = λ are not at all self-evident but are actually replaced by others."
Stop playing games. The section you are quoting is Born's treatment of the classical pre-relativity Doppler effect. Why not read the section where he treats it relativistically? :rolleyes:
Just two sentences later, Born goes on to say (emphasis mine):
"But we have chosen a method using the invariance of the number of waves becaused they can be used later in the theory of relativity."
If you choose a method of “using the invariance of the number of waves”, then you are being misleading, because the number of waves per second (ie the “frequency” shifts) are caused by two different reasons, as I’ve explained. Of course, you can ignore the reasons if you wish.
Doc,
So, if you ignore the two different reasons, and if the standard model of a redshift caused by a star that is moving away from the earth is due to a "physical lengthening" of the wavelengths of the light coming from the star, then how would you use SR theory to explain the redshift observed at the earth and caused by the earth moving away from a star that is fixed relative to the sun?
If you choose a method of “using the invariance of the number of waves”, then you are being misleading, because the number of waves per second (ie the “frequency” shifts) are caused by two different reasons, as I’ve explained. Of course, you can ignore the reasons if you wish.
David, you are the one quoting Nobel-prize winner Max Born. If you disagree with what he's saying, why quote him?
It is quite sad that you repeatedly attempt an argument from authority by quoting Einstein and Born--as if those guys didn't understand relativity and would agree with your misconceptions.
David, you are the one
Doc, et al,
How would you use SR theory to explain the redshift of starlight observed at the earth as the earth revolves around the sun, and caused by the earth moving away from a star that is fixed relative to the sun?
How would you use SR theory to explain the redshift of starlight observed at the earth as the earth revolves around the sun, and caused by the earth moving away from a star that is fixed relative to the sun?
Here's the relativistic Doppler formula:
\nu_{observed} = \nu_{source}\sqrt{\frac{1 + \frac{v}{c}}{1 - \frac{v}{c}}}
Where v is the relative speed of the source and observer: v is positive when the source is approaching the observer. In the case you mention, v is negative, thus a "red shift" is observed.
For a derivation, check Born's book.
Here's the relativistic Doppler formula:
\nu_{observed} = \nu_{source}\sqrt{\frac{1 + \frac{v}{c}}{1 - \frac{v}{c}}}
Where v is the relative speed of the source and observer: v is positive when the source is approaching the observer. In the case you mention, v is negative, thus a "red shift" is observed.
For a derivation, check Born's book.
My question was, “How would you use SR theory to explain the redshift of starlight observed at the earth as the earth revolves around the sun, and caused by the earth moving away from a star that is fixed relative to the sun?”
I didn’t ask you for the amount of redshift.
Your equation gives the amount of shift, but where in the equation does it reveal if the shift is caused by a wavelength change or an observer-relative light velocity change?
You will recall that there are two separate causes of Doppler shifts: 1) wavelength change (moving emitter), 2) observer-relative wave speed change (moving observer).
Since the star is fixed relative to the sun, that leaves out a wavelength change. Where in your equation does it say that Doppler Cause #2 is the one that causes the shift when the earth is moving relative to the star?
Doppler Law provides a definite answer to this question.
Once again, realize that there is no inertial frame in which light is at rest. From the light's point of view--there is no distance! Everything shrinks to zero.
You make this stuff up faster than anyone can refute it.
From the light’s point of view, there is always distance. That’s why it takes light time to get from one place to another. Light doesn’t have a personal opinion, it just moves, and it moves over a great distance to get from star to star. Light and radio waves wouldn’t have “wavelengths” if there was “no distance” from the light’s point of view.
But the premise of your thought experiment is flawed. As soon as you say "I am in a spaceship leaving earth at the speed-of-light" you have violated SR, since no inertial frame (material body) can move at that speed with respect to anything!
Oh, come on! Many distant galaxies exhibit redshifts that indicate they are moving away from the earth at 2, 3, 4, and 5 c.
The Davis-Lineweaver paper tells how their light reaches us from the superluminal galaxies.
You are living in the past. This is not 1905, this is the 21st Century. You are just posting 100 year old rumors, superstitions, and urban legends.
Oh, come on! Many distant galaxies exhibit redshifts that indicate they are moving away from the earth at 2, 3, 4, and 5 c.
The Davis-Lineweaver paper tells how their light reaches us from the superluminal galaxies.
Yes, interesting stuff! Note that the authors claim no contradiction with SR, since those galaxies are outside our inertial frame. I am not qualified to provide a detailed analysis of that paper, since I am no expert on general relativity. (Perhaps an expert can comment?) But I believe it is commonly understood that the cosmological redshift can only be understood via general relativity: special relativity cannot be applied on a cosmological scale. You cannot interpret the cosmological redshift as a relativistic doppler shift --- or any kind of doppler shift.
You are living in the past. This is not 1905, this is the 21st Century. You are just posting 100 year old rumors, superstitions, and urban legends.
Well, I don't know about that. It seems that you're the one who hasn't yet caught up to special relativity. You still cling to the quaint pre-relativistic "Doppler Law". :smile:
Oh, come on! Many distant galaxies exhibit redshifts that indicate they are moving away from the earth at 2, 3, 4, and 5 c.
The Davis-Lineweaver paper tells how their light reaches us from the superluminal galaxies.
You are living in the past. This is not 1905, this is the 21st Century. You are just posting 100 year old rumors, superstitions, and urban legends.
This is due to general relativity which hasn't been mentioned so far, you have to realize that special relatvity is the special case of general relatvity. The reason why it hasn't been mentioned so far is the fact that in all the examples given there's been no reason to assume any significant deviation from the Minowski metric, so only the special case needs to be considered.
It is wrong to call these galaxies superluminal as it implies something that's not happening as their local coordinate velocity is still less than c in all (local, obviously) inertial rference frames. The red shift isn't due to relative motion between the two objects but the expansion of space.
It is wrong to call these galaxies superluminal as it implies something that's not happening as their local coordinate velocity is still less than c in all (local, obviously) inertial rference frames. The red shift isn't due to relative motion between the two objects but the expansion of space.
Look, when you run away from me at 5 mph, you are “moving” away from me.
If you get in a car and move away from me at 60 mph, you are still “moving” away from me, even though you can say you are being “carried along” by the car.
The fact is, Lorentz invented the “speed limit” in 1895, and it was his limit for the speed of “ponderable bodies” through the “universal ether”. Einstein adapted it in 1905 to be the “speed limit” for “space”.
All the astronomy books, going back to the early 1930s, said the galaxies were “moving through space”, right up until the 1980s or ‘90s, when the first astronomer found the first superluminal galaxy, then all of a sudden the “expanding space” idea was invented. Now none of the galaxies are “moving” but are being “carried along” by “expanding space.”
Look, I’m an older guy. I’ve learned in life why some people in some fields tell one story for 50-60 years, then all of a sudden they change the story. This galaxy-motion story was changed in the 1990s in an attempt to try to salvage the 1905 “constancy” postulate, after superluminal galaxies were finally discovered.
And let me tell you something else. When I studied astronomy in 1956, when I was in junior high school, and when I built a 6 inch telescope, and when I saw Mars during its close approach that year, all the astronomy books and school science textbooks I could find said there were “green plants” growing all over the surface of Mars. This story had been told for more than a hundred years, until we finally sent a rocket to Mars and saw no “green plants” growing on it. Turns out the “green” was just an optical illusion, with green being the negative of red (reddish orange) and so the dark areas of the reddish Martian desert looked a little greenish through earth-based telescopes. So I feel I have the right to challenge any unreasonable theory, such as the “expansion of space” theory that is supposed to "carry along" the "unmoving galaxies", which is new and is just used as a device to salvage the “constancy” postulate, since superluminal galaxies were finally discovered.
Now, if you apply this information to the basic Lorentz theory, what do you have? How can you relate what we observe to the original Lorentz concept of a “speed limit”. Think of what he originally said, think of the limit to how fast we can push particles here on earth, and how fast the distant galaxies are moving, and what do you have? The implication is very important, but no one has written any science papers about it yet.
Yes, interesting stuff! Note that the authors claim no contradiction with SR, since those galaxies are outside our inertial frame. I am not qualified to provide a detailed analysis of that paper, since I am no expert on general relativity. (Perhaps an expert can comment?)
LOL, yes, D&L were very diplomatic! They basically disproved the SR “constancy” postulate, but they said they didn’t contradict SR. Very clever. Maybe I should take that approach.
Did you like the part of their paper where they said that newly-emitted photons in superluminal galaxies are traveling backwards, away from the earth, for thousands of years, then the photons finally slow down their backward movement and gradually start traveling toward the earth? I just loved that part.
But I believe it is commonly understood that the cosmological redshift can only be understood via general relativity: special relativity cannot be applied on a cosmological scale. You cannot interpret the cosmological redshift as a relativistic doppler shift --- or any kind of doppler shift.
Nope, it's a Doppler shift.
Well, I don't know about that. It seems that you're the one who hasn't yet caught up to special relativity. You still cling to the quaint pre-relativistic "Doppler Law". :smile:
SR originally was supposed to apply to a cosmological scale, but Einstein later realized it didn’t.
I think it would help you if you read some of his other papers, other than the few that were published in “The Principle of Relativity”. His earliest papers are the most interesting, but some of them contained stuff that he later changed and amended. Like any scientist, he learned more the older he became, and the older he became the more he learned.
There are certain things about the Doppler Law that can not be changed. The TWO fundamental reasons for the shifts, for example.
What Lorentz did was ADD some quantum electrodynamics stuff to the Doppler Laws, regarding oscillating atoms moving through fields. Lorentz was the one who invented the “relativistic” Doppler shift, which includes the two Doppler Laws, plus the electrodynamic effects on oscillating atoms moving through fields. At first, in 1905, Einstein mistook the electrodynamical effect for a “kinematical” effect, but he later realized his error and made changes accordingly, such as in his 1911 and 1916 papers. Those papers do consider the Lorentzian electrodynamical effects on moving atoms. In fact, the “Electrodynamic” part of the 1905 paper considers those effects, but the “Kinematical” part does not. I can explain the difference in the two parts if you would like for me to. :smile:
DrChinese
May17-04, 09:35 PM
... So I feel I have the right to challenge any unreasonable theory, such as the “expansion of space” theory that is supposed to "carry along" the "unmoving galaxies", which is new and is just used as a device to salvage the “constancy” postulate, since superluminal galaxies were finally discovered.
Now, if you apply this information to the basic Lorentz theory, what do you have? How can you relate what we observe to the original Lorentz concept of a “speed limit”. Think of what he originally said, think of the limit to how fast we can push particles here on earth, and how fast the distant galaxies are moving, and what do you have? The implication is very important, but no one has written any science papers about it yet.
What you are saying is reasonable on the surface, but...
If science is doing its job, then we will converge on a progressively better set of theories to describe nature. This appears to be happening - we are moving forward, not backward. Lineweaver and Davis, as strange as it is (and it certainly is strange to me), is not actually violating anything we had set in stone for decades anyway. After all, the expansion of space (Guth's inflation) was postulated a long time ago, so evidence confirming it shouldn't be a total surprise. (Even if it is weird. Not any weirder than QM, think?)
So it is not really a strong argument to point out past errors in scientific history and try to extrapolate from those. The CMBR was discovered around 1965, QM in 1927 and GR in 1915. There is a lot explained by these big 3.
Clearly the special relativistic formulas have been tested many times, including frequency shift due to relative motion. Not sure how you can argue that point. If two objects were each approaching a common midpoint at a substantial percentage of the speed of light, they will in fact approach each other faster than the speed of light measured by some observers. But light they emit cannot be measured to have a speed of any other value than c by any observer. Do you dispute that?
Lineweaver and Davis, as strange as it is (and it certainly is strange to me), is not actually violating anything we had set in stone for decades anyway. After all, the expansion of space (Guth's inflation) was postulated a long time ago, so evidence confirming it shouldn't be a total surprise. (Even if it is weird. Not any weirder than QM, think?)
Actually it was Newton who first suggested the expansion of the universe and the big bang theory. He called it a “projectile impulse”. He proposed 4 possible conditions of the universe: 1) contraction, 2) expansion, 3) infinite, 4) rotation.
He was right about two of those; rotation on a local scale and expansion on the large scale.
The Davis Lineweaver paper is essentially a “local ether” theory, with their term local “comoving space” acting as the “ether”, although they don’t define what gives local comoving space ether-like qualities.
What I find most amusing about their paper is when the light from a distant superluminal galaxy moves backwards away from the earth before it moves forwards toward the earth.
Clearly the special relativistic formulas have been tested many times, including frequency shift due to relative motion.
Apparent frequency shift due to relative motion is a Doppler effect, explained by Doppler in 1841.
The oscillation rate slow-down in atoms moving through fields is an electrodynamics effect, explained by Lorentz in 1895.
There is no “wristwatch” or “balance clock” slow-down due to “relative motion” as “predicted” in SR theory, because “relative motion” does not cause balance wheel wristwatches or balance wheel clocks to slow down.
Look, when you run away from me at 5 mph, you are “moving” away from me.
If you get in a car and move away from me at 60 mph, you are still “moving” away from me, even though you can say you are being “carried along” by the car.
The fact is, Lorentz invented the “speed limit” in 1895, and it was his limit for the speed of “ponderable bodies” through the “universal ether”. Einstein adapted it in 1905 to be the “speed limit” for “space”.
All the astronomy books, going back to the early 1930s, said the galaxies were “moving through space”, right up until the 1980s or ‘90s, when the first astronomer found the first superluminal galaxy, then all of a sudden the “expanding space” idea was invented. Now none of the galaxies are “moving” but are being “carried along” by “expanding space.”
Look, I’m an older guy. I’ve learned in life why some people in some fields tell one story for 50-60 years, then all of a sudden they change the story. This galaxy-motion story was changed in the 1990s in an attempt to try to salvage the 1905 “constancy” postulate, after superluminal galaxies were finally discovered.
And let me tell you something else. When I studied astronomy in 1956, when I was in junior high school, and when I built a 6 inch telescope, and when I saw Mars during its close approach that year, all the astronomy books and school science textbooks I could find said there were “green plants” growing all over the surface of Mars. This story had been told for more than a hundred years, until we finally sent a rocket to Mars and saw no “green plants” growing on it. Turns out the “green” was just an optical illusion, with green being the negative of red (reddish orange) and so the dark areas of the reddish Martian desert looked a little greenish through earth-based telescopes. So I feel I have the right to challenge any unreasonable theory, such as the “expansion of space” theory that is supposed to "carry along" the "unmoving galaxies", which is new and is just used as a device to salvage the “constancy” postulate, since superluminal galaxies were finally discovered.
Now, if you apply this information to the basic Lorentz theory, what do you have? How can you relate what we observe to the original Lorentz concept of a “speed limit”. Think of what he originally said, think of the limit to how fast we can push particles here on earth, and how fast the distant galaxies are moving, and what do you have? The implication is very important, but no one has written any science papers about it yet.
I'm sorry but you really couldn't be more wrong:
Friedmann Lemaitre cosmology has been around since the 1920's and was taken up after Hubble found the redshift in the 1940's, so basically it's always been the case that redshift has been attributed to the expansion of space.
What you also don't underdstand is that red shift can't be attributed to any superluminal velocity in special relativity as the equation is:
\frac{\lambda}{\lambda_0} = z + 1 = \sqrt{\frac{c+v}{c-v}}
In the case where v > c you find that \lambda is an imaginary quantity! Let me tell you that the wavelengths that we measure from these galaxies with superluminal recession velocity are NOT imaginary.
It's only when you take into account the fact that space is expanding and use general relativity that you find that galaxies may have superluminal recession velocities.
DrChinese
May18-04, 08:39 AM
Actually it was Newton who first suggested the expansion of the universe and the big bang theory. He called it a “projectile impulse”. He proposed 4 possible conditions of the universe: 1) contraction, 2) expansion, 3) infinite, 4) rotation.
He was right about two of those; rotation on a local scale and expansion on the large scale.
The Davis Lineweaver paper is essentially a “local ether” theory, with their term local “comoving space” acting as the “ether”, although they don’t define what gives local comoving space ether-like qualities.
What I find most amusing about their paper is when the light from a distant superluminal galaxy moves backwards away from the earth before it moves forwards toward the earth.
I specified I was discussing Guth's inflationary scenario, not the general expansion of space.
Yes, I agree with you about D&L: at first it seems counterintuitive that the light gets farther away before it finally begins to get closer. However, after I thought about it a while, I realized that something like what they describe must occur if we can see older galaxies at all.
Assume NO ongoing superluminal expansion/inflation: Suppose you had a galaxy emitting light at T=1 billion (years after BB). If we are now at T=13.7, we would have to be exactly 12.7 billion years away from it to see it now if there were no ongoing inflation. But at T=1 billion we couldn't have been far enough away from that galaxy for it to take more than a couple of billion years for that light to arrive. Something had to have slowed it down for us to see it today. Either that, or our calibration of the age of universe/our position and velocity through space/etc. are WAY off.
DrChinese
May18-04, 09:05 AM
Friedmann Lemaitre cosmology has been around since the 1920's and was taken up after Hubble found the redshift in the 1940's, so basically it's always been the case that redshift has been attributed to the expansion of space.
What you also don't underdstand is that red shift can't be attributed to any superluminal velocity in special relativity as the equation is:
\frac{\lambda}{\lambda_0} = z + 1 = \sqrt{\frac{c+v}{c-v}}
In the case where v > c you find that \lambda is an imaginary quantity! Let me tell you that the wavelengths that we measure from these galaxies with superluminal recession velocity are NOT imaginary.
It's only when you take into account the fact that space is expanding and use general relativity that you find that galaxies may have superluminal recession velocities.
Well said. As you point out, it is easy to confuse SR scenarios with GR scenarios.
Davis & Lineweaver does not introduce any new physics that I am aware of. I think it is really putting everything together in a package that ties it all together nicely. So I don't agree with David's dismissal of their content. The fact is that superluminal (high redshift) galaxies have been observed, and that renders most objections moot. D&L explain why this is consistent with both SR and GR.
Davis & Lineweaver does not introduce any new physics that I am aware of. I think it is really putting everything together in a package that ties it all together nicely. So I don't agree with David's dismissal of their content. The fact is that superluminal (high redshift) galaxies have been observed, and that renders most objections moot. D&L explain why this is consistent with both SR and GR.
SR doesn’t apply. Its “speed limit of c” is not correct, and its constancy postulate is not correct.
The classical Doppler redshifts indicate that the distant galaxies move much faster than c relative to the earth and their light takes so long to reach us because it is first moving at an average of c relative to the galaxy that emits the light but at – c relative to the earth. Light gradually slows down the negative speed as it travels through space and it gradually speeds up in the direction of the earth.
So, the D&L paper reveals that the speed of light is not “constant”, the galaxies don’t have any “speed limit” relative to the earth, and some kind of “local ether” regulates the speed of light in space, which is what I’ve been saying all along. GR theory originally said the universe was not “expanding”, so Einstein had to modify GR to make it fit observation. So regarding both SR and GR, Einstein was wrong. He had to change his incorrect theories to match observation.
Peterdevis
May18-04, 11:08 AM
Dear David,
I've posted ti before, you don't understand anything of the paper of Davis & Lineweaver .
I think it's better you just study general relativity. Before you do that , study first differential geometry (you can find a lot of good lectures on the net).
Assume NO ongoing superluminal expansion/inflation: Suppose you had a galaxy emitting light at T=1 billion (years after BB). If we are now at T=13.7, we would have to be exactly 12.7 billion years away from it to see it now if there were no ongoing inflation. But at T=1 billion we couldn't have been far enough away from that galaxy for it to take more than a couple of billion years for that light to arrive. Something had to have slowed it down for us to see it today. Either that, or our calibration of the age of universe/our position and velocity through space/etc. are WAY off.
Sure, because the light was moving backwards and away from the earth during much of that time, while the distant galaxy was moving at 4 or 5 c away from the earth. This is explained by a moving medium in classical Doppler theory, 1842. There is no “relativity” involved with this phenomenon.
Einstein’s own incorrect relativity ideas kept him blind to this phenomenon and the expansion of the universe. He had to alter his theories after Hubble made his announcement.
It was Newton who first proposed the BB theory, and he turned out to be right.
There are three relative speeds of a photon: 1) its speed relative to the medium through which it travels, 2) its speed relative to its emitter, and 3) its speed relative to an observer. These speeds change as the photon moves through space.
Dear David,
I've posted ti before, you don't understand anything of the paper of Davis & Lineweaver .
I think it's better you just study general relativity. Before you do that , study first differential geometry (you can find a lot of good lectures on the net).
I knew the DL conclusions before they even wrote their paper. I figured it out in the early 1990s.
I knew we could not see the light from a high-c galaxy until that light got out of the local propagating medium of that galaxy and entered the propagating media of other galaxies that were not moving as rapidly away from the earth. Finally the light enters our galaxy and is regulated to “c” at the surface of the earth.
D&L made this quite clear in their paper when they said:
“The relevant quantity for understanding this behaviour is the total velocity of a photon that is heading towards us: vtot = vrec - c = HD - c = axy - c. The total velocity of distant photons is not constant because it is the sum of the distance-dependent recession velocity (vrec) and the constant peculiar velocity, c. When axy > c the distance between us and the photon increases.”
The only way they got their paper published was by praising Einstein and by pretending that Einstein predicted this.
Actually, Doppler predicted this with a moving medium, but a physics theorist today generally has to have his papers cleared and approved by Einstein cultists before the paper can be published.
russ_watters
May18-04, 11:58 AM
...but a physics theorist today generally has to have his papers cleared and approved by Einstein cultists before the paper can be published. You're going further and further into the deep end with every post, David.
And of course, as you've been told several times, Einstein may have thought up the theory that bears his name, but it has grown far beyond his contribution to it.
SR doesn’t apply. Its “speed limit of c” is not correct, and its constancy postulate is not correct.
The classical Doppler redshifts indicate that the distant galaxies move much faster than c relative to the earth and their light takes so long to reach us because it is first moving at an average of c relative to the galaxy that emits the light but at – c relative to the earth. Light gradually slows down the negative speed as it travels through space and it gradually speeds up in the direction of the earth.
So, the D&L paper reveals that the speed of light is not “constant”, the galaxies don’t have any “speed limit” relative to the earth, and some kind of “local ether” regulates the speed of light in space, which is what I’ve been saying all along. GR theory originally said the universe was not “expanding”, so Einstein had to modify GR to make it fit observation. So regarding both SR and GR, Einstein was wrong. He had to change his incorrect theories to match observation.
SR applies locally still, indeed SR always applies locally in GR. Of course in the case of recession velocites we are not dealing with the Minowski metric, so we cannot look at just the special case we have to look at the general case (think of it this analogy: SR is like the generalized form of the equation of a circle and GR is like the generalized form for the equation of an elipse, of which the circle is a special case). The local coordinate velcoity of light is still always c in GR (this should be obvious as the spaces are described are still manifolds), but the remote coordinate velocity isn't always c.
Now we never use the non-relativistic formula for redshift in this situationas we know that it is only an approximation valid when c >> v and doesn't take into account the curvature of spacetim or it's expansion.
GR does say that the universe is expanding, indeed it comes naturally out of the theory, rmemebr that the Friedmann-Lemaitre cosmolocal model was entirley based on GR and this was before any evidence was observed for an expanding universe.
GR does say that the universe is expanding, indeed it comes naturally out of the theory, rmemebr that the Friedmann-Lemaitre cosmolocal model was entirley based on GR and this was before any evidence was observed for an expanding universe.
No, that is not true. If GR said “the universe is expanding,” then Einstein would have said, “the universe is expanding” in 1916. But he specifically said the universe was “fixed”.
GR was specifically designed to keep the universe from either expanding or contracting.
All of this goes back to the question that Newton and others asked, “If the gravity of all astronomical bodies ‘pulls’ on each of the bodies, then why does the universe not collapse in on itself, due to all the gravitational pull?”
Newton suggested four possible solutions to that question: 1) maybe it is collapsing but we just don’t notice it; 2) maybe it is expanding but we just don’t notice it; 3) maybe the universe is infinite and all gravity ‘pulls’ cancel each other out in all directions; 4) maybe the whole universe is rotating.
Turns out that he was right about #2.
Turns out that Einstein was wrong and the universe was not “fixed”. He wrote a paper about this in 1932, in which he retracted his “curved space” idea and his cosmological constant. So, he not only didn’t “predict” the expansion, he was caught off-guard by it and had to change his GR theory to accommodate the expansion. Here are some excerpts from his 1932 paper:
”In a recent note in the Göttinger Nachrichten, Dr. O. Heckmann has pointed out that the non-static solutions of the field equations of the general theory of relativity with constant density do not necessarily imply a positive curvature of three-dimensional space, but that this curvature may also be negative or zero.
There is no direct observational evidence for the curvature, the only directly observed data being the mean density and the expansion, which latter proves that the actual universe corresponds to the non-statical case. It is therefore clear that from the direct data of observation we can derive neither the sign nor the value of the curvature, and the question arises whether it is possible to represent the observed facts without introducing a curvature at all.
Although, therefore, the density corresponding to the assumption of zero curvature and to the coefficient of expansion may perhaps be on the high side, it certainly is of the correct order of magnitude, and we must conclude that at the present time it is possible to represent the facts without assuming a curvature of three-dimensional space. The curvature is, however, essentially determinable, and an increase in the precision of the data derived from observations will enable us in the future to fix its sign and to determine its value.”
Full title of the paper: “On the Relation between the Expansion and the Mean Density of the Universe” Albert Einstein and Wilhelm de Sitter, Proceedings of the National Academy of Sciences 18, 213-214. Reproduced in “A Source Book in Astronomy and Astrophysics, 1900 – 1975”, published by Harvard University Press, Cambridge, MA, and London, England, 1979. Edited by Kenneth R. Lang and Owen Gingerich.
What started the new renewed interest in the possibility that the universe was “expanding” was Sliper’s work early in the 20th Century, and especially his 1917 paper, “A Spectrographic Investigation of Spiral Nebulae,” Proceedings of the American Philosophical Society 56, 403-409 (1917). He said in his paper that his spectrographic evidence revealed that the majority of spiral galaxies he examined were moving away from the earth at high speeds, at speeds much faster than the speeds of the motions of the stars. So it was his work that told physicists as early as 1917 that the universe certainly was not “fixed” and that it seemed to be expanding. 10 years later Hubble confirmed Sliper’s findings. Five years after Hubble’s announcement, Einstein retracted his “universal curved space” idea and his “cosmological constant”.
You need to go back and read the original papers and original books. You can’t rely on information published in modern books and magazine articles, written by science writers who haven’t conducted the proper historical research. What they often do is merely copy two or three other recent articles they’ve read. I was in the magazine business, and I know how it works. Writers grab urban legends from other recent magazine articles and books, and they pass the legends along without conducting any in-depth research of their own.
No, that is not true. If GR said “the universe is expanding,” then Einstein would have said, “the universe is expanding” in 1916. But he specifically said the universe was “fixed”.
GR was specifically designed to keep the universe from either expanding or contracting.
All of this goes back to the question that Newton and others asked, “If the gravity of all astronomical bodies ‘pulls’ on each of the bodies, then why does the universe not collapse in on itself, due to all the gravitational pull?”
Newton suggested four possible solutions to that question: 1) maybe it is collapsing but we just don’t notice it; 2) maybe it is expanding but we just don’t notice it; 3) maybe the universe is infinite and all gravity ‘pulls’ cancel each other out in all directions; 4) maybe the whole universe is rotating.
Turns out that he was right about #2.
Turns out that Einstein was wrong and the universe was not “fixed”. He wrote a paper about this in 1932, in which he retracted his “curved space” idea and his cosmological constant. So, he not only didn’t “predict” the expansion, he was caught off-guard by it and had to change his GR theory to accommodate the expansion. Here are some excerpts from his 1932 paper:
”In a recent note in the Göttinger Nachrichten, Dr. O. Heckmann has pointed out that the non-static solutions of the field equations of the general theory of relativity with constant density do not necessarily imply a positive curvature of three-dimensional space, but that this curvature may also be negative or zero.
There is no direct observational evidence for the curvature, the only directly observed data being the mean density and the expansion, which latter proves that the actual universe corresponds to the non-statical case. It is therefore clear that from the direct data of observation we can derive neither the sign nor the value of the curvature, and the question arises whether it is possible to represent the observed facts without introducing a curvature at all.
Although, therefore, the density corresponding to the assumption of zero curvature and to the coefficient of expansion may perhaps be on the high side, it certainly is of the correct order of magnitude, and we must conclude that at the present time it is possible to represent the facts without assuming a curvature of three-dimensional space. The curvature is, however, essentially determinable, and an increase in the precision of the data derived from observations will enable us in the future to fix its sign and to determine its value.”
Full title of the paper: “On the Relation between the Expansion and the Mean Density of the Universe” Albert Einstein and Wilhelm de Sitter, Proceedings of the National Academy of Sciences 18, 213-214. Reproduced in “A Source Book in Astronomy and Astrophysics, 1900 – 1975”, published by Harvard University Press, Cambridge, MA, and London, England, 1979. Edited by Kenneth R. Lang and Owen Gingerich.
What started the new renewed interest in the possibility that the universe was “expanding” was Sliper’s work early in the 20th Century, and especially his 1917 paper, “A Spectrographic Investigation of Spiral Nebulae,” Proceedings of the American Philosophical Society 56, 403-409 (1917). He said in his paper that his spectrographic evidence revealed that the majority of spiral galaxies he examined were moving away from the earth at high speeds, at speeds much faster than the speeds of the motions of the stars. So it was his work that told physicists as early as 1917 that the universe certainly was not “fixed” and that it seemed to be expanding. 10 years later Hubble confirmed Sliper’s findings. Five years after Hubble’s announcement, Einstein retracted his “universal curved space” idea and his “cosmological constant”.
You need to go back and read the original papers and original books. You can’t rely on information published in modern books and magazine articles, written by science writers who haven’t conducted the proper historical research. What they often do is merely copy two or three other recent articles they’ve read. I was in the magazine business, and I know how it works. Writers grab urban legends from other recent magazine articles and books, and they pass the legends along without conducting any in-depth research of their own.
As I saidn expansion comes naturally out of GR, but if you assume a certain value for the cosmological constant then you get a steady state. this is all Einstein did.
One should recall that when Einstein was deriving his field equations, he was distressed to find that they predicted an expanding universe.
So he went back to a previous step where he had performed integration. His original derivation had assumed the constant of integration was zero, so he removed that assumption. That constant of integration is what we now call the cosmological constant, and can yield a steady state model when set to the right value. Einstein was happy.
Later, when it was shown the universe is expanding, Einstein said that dismissing GR's prediction of said fact was the greatest blunder of his life.
As I saidn expansion comes naturally out of GR, but if you assume a certain value for the cosmological constant then you get a steady state. this is all Einstein did.
No, “collapse” comes naturally out of any gravity theory. That’s why he added the cosmological constant, to keep the universe from collapsing. The constant served his purposes to keep the universe from contracting or expanding. This was due to an ideological belief of his, which you can read about in chapter 30 of his 1916 book:
http://www.marxists.org/reference/archive/einstein/works/1910s/relative/ch30.htm
He didn’t want the universe to be either contracting or expanding. It’s unfortunate when scientists allow their ideological beliefs to interfere with their science research.
Later, when it was shown the universe is expanding, Einstein said that dismissing GR's prediction of said fact was the greatest blunder of his life.
LOL, show me the original Einstein document that quote is in! Your version is new. That’s not what I’ve been reading in books and magazine articles for the past 20 years.
He was embarrassed for not in any way predicting the expansion, and he was embarrassed because Newton did predict it 235 years earlier.
Here’s what Einstein actually said in his 1917 paper, “Cosmological Considerations on the General Theory of Relativity”:
“From this it follows in the first place that the radiation emitted by the heavenly bodies will, in part, leave the Newtonian system of the universe, passing radially outwards, to become ineffective and lost in the infinite. May not entire heavenly bodies fare likewise? It is hardly possible to give a negative answer to this question. For it follows from the assumption of a finite limit for Φ at spatial infinity that a heavenly body with finite kinetic energy is able to reach spatial infinity by overcoming the Newtonian forces of attraction. By statistical mechanics this case must occur from time to time, as long as the total energy of the stellar system – transferred to one single star – is great enough to send that star on its journey to infinity, which it never can return.”
Here he is merely speculating that “from time to time” some stars might escape a spherical Newtonian universe, and he is certainly indicating here that he has no idea that a mass “expansion” of stars and galaxies was taking place.
He went on to say,
“These differences must really be of so low an order of magnitude that the stellar velocities generated by them do not exceed the velocities actually observed.”
He is talking here about the very low speeds of stars, which is all he knew about at that time. He didn’t even know then, in 1917, that galaxies were collections of stars outside our own galaxy, and he was not yet aware of Sliper’s work regarding the high-speed motion of the galaxies.
It is attributed to Einstein by George Gamow in "My World Line". I find it difficult to believe that you have spent 20 years researching the topic without ever having encountered the phrase; it appears in just about every non-technical article about the cosmological constant.
I find it curious that the only two references I could find to "projectile impulse" in reference to an expanding universe was this post (http://www.metaresearch.org/msgboard/topic.asp?TOPIC_ID=481) by, well, you.
But in any case, I just don't see the point of your post, David. Democritus believed matter was made up of atoms, but we can hardly attribute to him the atomic theory of matter. Supposing Newton did consider the idea that all mass did originally have a "projectile impulse" that has not yet been overcome by gravitational attraction, such a theory bears no resemblence to big bang theory. (Though it is somewhat similar to the popular misconceptions of BBT)
russ_watters
May18-04, 10:02 PM
It is attributed to Einstein by George Gamow in "My World Line". I find it difficult to believe that you have spent 20 years researching the topic without ever having encountered the phrase; it appears in just about every non-technical article about the cosmological constant. Here are 3,570 references.... http://www.google.com/search?hl=en&lr=&ie=UTF-8&q=cosmological+constant+einstein+blunder (here's one):Einstein's original cosmological model was a static, homogeneous model with spherical geometry. The gravitational effect of matter caused an acceleration in this model which Einstein did not want, since at the time the Universe was not known to be expanding. Thus Einstein introduced a cosmological constant into his equations for General Relativity. This term acts to counteract the gravitational pull of matter, and so it has been described as an anti-gravity effect. In addition to this flaw of instability, the static model's premise of a static Universe was shown by Hubble to be incorrect. This led Einstein to refer to the cosmological constant as his greatest blunder, and to drop it from his equations.
The gravitational effect of matter caused an acceleration in this model which Einstein did not want, since at the time the Universe was not known to be expanding.
Uhh, excuse me, but the “gravitational effect” doesn’t cause masses to fly apart. It causes them to collapse in on each other.
I find it curious that the only two references I could find to "projectile impulse" in reference to an expanding universe was this post (http://www.metaresearch.org/msgboard/topic.asp?TOPIC_ID=481) by, well, you.
Oh, you’ve searched all the books of the world?
You’ve searched through all my books?
Or did you just do a quick Google?
Quick Googles are bringing ignorance to the world of science.
Here, try this search engine and go find yourself some real books:
http://www.trussel.com/f_books.htm
It is attributed to Einstein by George Gamow in "My World Line". I find it difficult to believe that you have spent 20 years researching the topic without ever having encountered the phrase; it appears in just about every non-technical article about the cosmological constant.
The most published phrase has been, “the cosmological constant was my worst mistake”. It had absolutely nothing to do with Einstein’s equations claiming the universe was “expanding”. His equations did not show that, and he did not believe that.
Just like with any gravity theory, a spherical universe will collapse, not expand, unless someone adds something like the “cosmological constant” or hypothesizes a “projectile impulse” at the beginning. Neither Einstein nor his equations “predicted” the Big Bang.
Do you understand? Gravity attracts. He thought the universe would collapse if he didn’t add the “cosmological constant”. It didn’t occur to him that it might be “expanding”. The combined gravity fields of the universe would have had a natural “collapsing” effect, not an “expansion” effect. So he added the constant to keep it from collapsing and also to keep it from having a center.
What you said here was wrong:
One should recall that when Einstein was deriving his field equations, he was distressed to find that they predicted an expanding universe.
Later, when it was shown the universe is expanding, Einstein said that dismissing GR's prediction of said fact was the greatest blunder of his life.
His equations DID NOT predict an expanding universe, and that’s not why he added the “cosmological constant”.
Quick Googles are bringing ignorance to the world of science.
You're right, I suppose I should've consulted the vast collection of books on the history of science that I have on my bookshelf. How silly of me.
(allow me to point out that there is a lot of good information available on the internet if one knows how to look and how to sort the good from the bad)
(And, for the record, "projectile impulse" did appear in a Google search, but aside from your post, the term is not in reference to an expanding universe)
(And, incidentally, I did a bit more than a quick search)
Anyways, it would tend to be customary in this situation for you to provide a specific reference, rather than deride others for not finding it.
I've since come across the text of four of Newton's letters to Bentley. Nowhere in them appears the word "projectile", let alone "projectile impulse", nor do they seem to contain any content resembling what you ascribe to Newton. (Though I will admit it's past midnight and I'm sleepy, so I may not have been 100% thorough in browsing them, so if you still stand by your assertion, maybe you could point out just where it appears)
Just like with any gravity theory, a spherical universe will collapse, not expand, unless someone adds something like the ?cosmological constant? or hypothesizes a ?projectile impulse? at the beginning.
I did some checking, and every reference I encountered confirms what I remember. Solutions with Λ = 0 all have decreasing rates of expansion (negative expansion = contraction). Among possibilities are (this list may be exhaustive, given reasonable constraints on matter): an ever contracting universe, an ever expanding universe, and a universe that starts off expanding but eventually contracts.
In any case, Λ = 0 cannot yield a static universe, thus Einstein introduced it (said it was nonzero) to enable a static universe.
For the record, references I did find to "projectile impulse" suggest the idea of some object physically imparting momentum to the other object to propel it (or parts of it) into an interesting trajectory. (e.g. Godwin's "Essay XXI of Astronomy") This is unsatisfactory for the concept of an expanding universe since there was no external object to impart said momentum. Furthermore, I even think it's nonsensical to suggest that the net expansion of space-time could be caused by any sort of collision. (But, alas, I don't know enough about GR to be sure of this last claim)
You're right, I suppose I should've consulted the vast collection of books on the history of science that I have on my bookshelf. How silly of me.
(allow me to point out that there is a lot of good information available on the internet if one knows how to look and how to sort the good from the bad)
I agree with that, Hurkyl, and I use Google all the time, but I’ve never told anyone that such and such is not true because I couldn’t find it on Google. That’s the danger of Google and the internet. There are things in books that are not on the internet and not indexed by Google.
I’m older than you. We didn’t have Google most of my life. We had “books”. Things made out of ink and paper, cardboard and leather.
Here is a quote from an 1803 book that I have in my library. This information comes from Newton’s letters to Bentley. I don’t have time to type up all my books and put all their text on the internet.
“Natural Theology”, by William Paley, 1803, page 276:
“But many of the heavenly bodies, as the sun and fixed stars are stationary. Their rest must be the effect of an absence or of an equilibrium of attractions. It proves also that a projectile impulse was originally given to some of the heavenly bodies, and not to others. But further; if attraction act at all distances, there can be only one quiescent center of gravity in the universe: and all bodies whatever must be approaching this center, or revolving around it. According to the first of these suppositions, if the duration of the world had been long enough to allow it, all its parts, all the great bodies of which it is composed, must have been gathered together in a heap round this point.”
Here are a few comments by Newton about the “big bang”, which he simply attributes to a “Deity”, since he couldn’t figure out how all the stars got distributed around space. As he points out, gravity should have been pulling all the stars inward, and there was no physics mechanism to account for the projectile motion of all the stars. In fact, today there is STILL no physics mechanism that can account for the projectile force that started the Big Bang.
“I would now add, that the Hypothesis of Matter’s being at first evenly spread through the Heavens, is, in my Opinion, inconsistent with the Hypothesis of innate Gravity, without a supernatural Power to reconcile them, and therefore infers a Deity. For if there be innate Gravity, it is impossible now for the Matter of the Earth and all the Planets and Stars to fly up from them, and become evenly spread throughout all the Heavens, without a supernatural Power; and certainly that which can never be hereafter without a supernatural power, could never be heretofore without the same Power.”
Here he is basically saying that God must have been responsible for the expansion of the universe and the even distribution of matter. This was written in one of his letters to Bentley, dated Feb. 11, 1693. His personal opinions about theological causes were generally restricted to his letters to Bentley, since Bentley was a preacher. Also keep in mind that in the old days the term “supernatural power” also meant a “natural power” that was “super” but “unknown.” In other words, not “magic”, but just an unknown natural power that was not understood yet. That was sort of like Einstein’s term, “God does not play dice with the universe.” In other words, God designed nature to work by “laws”, even if we don’t know yet what all those laws are. This excerpt is from the book “Isaac Newton Papers and Letters on Natural Philosophy,” edited by Bernard Cohen and published in 1958. You won’t find this stuff on Google. You have to get it from books. You can order a copy of this book from AbeBooks for as little as $15.
I did some checking, and every reference I encountered confirms what I remember. Solutions with Λ = 0 all have decreasing rates of expansion (negative expansion = contraction). Among possibilities are (this list may be exhaustive, given reasonable constraints on matter): an ever contracting universe, an ever expanding universe, and a universe that starts off expanding but eventually contracts.
In any case, Λ = 0 cannot yield a static universe, thus Einstein introduced it (said it was nonzero) to enable a static universe.
I know that. That’s what I said. You said he introduced it to keep the universe from expanding, but I told you that he introduced it to keep the universe from contracting.
With gravity, the universe should contract, not expand, and since he didn’t know of any evidence of the radial motion of the galaxies, he added the constant to explain why it was not contracting.
But a myth has grown up in recent years that says he added it to keep the universe from “expanding”. That is silly and it is just one of the many Einstein urban legends that have grown up in the past 30 years.
And as I said, Newton went over all of this very same stuff with Bentley and others 300 years ago.
I know that. That’s what I said. You said he introduced it to keep the universe from expanding, but I told you that he introduced it to keep the universe from contracting.
With gravity, the universe should contract, not expand, and since he didn’t know of any evidence of the radial motion of the galaxies, he added the constant to explain why it was not contracting.
But a myth has grown up in recent years that says he added it to keep the universe from “expanding”. That is silly and it is just one of the many Einstein urban legends that have grown up in the past 30 years.
And as I said, Newton went over all of this very same stuff with Bentley and others 300 years ago.
David, it depends on the parameters whether or not the unieverse will exopand in general relativity, but an expansion phase is a feature of realistic models.
David, it depends on the parameters whether or not the unieverse will exopand in general relativity, but an expansion phase is a feature of realistic models.
This is nothing new. With all the gravity in the universe, the only thing the universe can naturally do is “contract”, unless we add some kind of “cosmological constant” to keep it steady, or imagine some kind of “projectile force” to cause it to expand fast enough so that the expansion counter-acts the gravity. This has been known for hundreds of years. Einstein studied Newton’s stuff. He knew this. His personal preference was for a “static” universe because all the astronomy books he had read at the time said the universe looked “static”, so he designed the GR theory around that concept.
If he had preferred a “collapse”, he would have left out the constant. If he had preferred an expansion, he would have added an initial “projectile force” to his theory.
You need a 'projectile force' in GR as spacetime containing energy expands naturally (countered by gravity). Of cousre for ceratin densities to acheive certain rates of exapnsion some sort of force is needed (i.e. dark energy)
DrChinese
May19-04, 10:54 AM
... This is explained by a moving medium in classical Doppler theory, 1842. There is no “relativity” involved with this phenomenon.
Einstein’s own incorrect relativity ideas kept him blind to this phenomenon and the expansion of the universe. He had to alter his theories after Hubble made his announcement.
It was Newton who first proposed the BB theory, and he turned out to be right.
David, your abuse of history is even worse than your abuse of physics. All physicists consider many ideas and concepts during their liketime. To say that Newton invented or was a strong proponent of the BB is ridiculuous. It is just as absurd to say that Einstein created GR to justify a static universe, or that he was opposed to the BB.
And if you know of somewhere an observer can measure the speed of light to be different than c, well, please enlighten us. If you know of a way to accelerate an object above c, please enlighten us on that as well. Your Nobel awaits.
P.S. How could I have overlooked Doppler's contributions to photon theory, seeing instead Einstein's undeserved contributions? I guess it is that scientific conspiracy thing. Einstein would be amused to find that he was the beneficiary of that conspiracy.
russ_watters
May19-04, 11:32 AM
Uhh, excuse me, but the “gravitational effect” doesn’t cause masses to fly apart. It causes them to collapse in on each other. ?? It doesn't say anything in that quote about masses flying apart. What are you talking about? Just like with any gravity theory, a spherical universe will collapse, not expand, unless someone adds something like the “cosmological constant” or hypothesizes a “projectile impulse” at the beginning. Neither Einstein nor his equations “predicted” the Big Bang. So you're saying that its natural to assume that the universe is infinitely old and has been collapsing for an infinite amount of time, but has a finite amount of life left before collapsing completely? Doesn't that seem a little absurd to you (there are a large number of reasons why that is absurd)? Your intuition is pretty much opposite of what physicists have theorized, and for good reason: it leads to an absurd conclusion.
At one time, it was believed that the unvierse was eternal and static. But throwing gravity into that universe would indeed cause contraction: therefore the universe cannot be static. It must either be expanding or contracting. Gravity causes an acceleration that either slows expansion or causes contraction after an expansion phase (or both).
Since the universe cannot be infinitely old, contraction must have been preceded by expansion. And as it turns out, we're still in the expansion phase and we aren't yet sure if it will ever contract again (though its looking like no).And, for the record, "projectile impulse" did appear in a Google search, but aside from your post, the term is not in reference to an expanding universe My guess would be you didn't find it because "projectile impulse" implies to me an explosion, the usual misunderstanding/mischaracterization of the Big Bang
David, it appears I gave you too much credit before in assuming you were just arging points you knew to be wrong for fun: you appear now to have some major gaps in your knowledge/understanding and a simple unwillingness to learn. Though it may be more pathological: you abuse/distort/misrepresent/mischaracterize to cover your unwillingness to learn. Disappointing, actually.
russ_watters
May19-04, 11:38 AM
And if you know of somewhere an observer can measure the speed of light to be different than c, well, please enlighten us. If you know of a way to accelerate an object above c, please enlighten us on that as well. Your Nobel awaits. He has quite a lot actually - all based on the same type of abuses (or, to be fair, common misconceptions). A good one is the "acceleration" of light around a star through gravitational lensing and gravitational doppler shift being a variable C phenomenon.
The most common though I guess is his abuse of frames of reference such as in his statements about >C expansion of the universe.
russ_watters
May19-04, 11:42 AM
Among possibilities are (this list may be exhaustive, given reasonable constraints on matter): an ever contracting universe, an ever expanding universe, and a universe that starts off expanding but eventually contracts. For my own personal enlightenment, is that a reasonable possibility? I know it doesn't fit with what we observer our own universe to be doing, but hypothetically, could a unverse be eternally contracting? It doesn't seem to me that it would be.
DrChinese
May19-04, 04:15 PM
He has quite a lot actually - all based on the same type of abuses (or, to be fair, common misconceptions). A good one is the "acceleration" of light around a star through gravitational lensing and gravitational doppler shift being a variable C phenomenon.
The most common though I guess is his abuse of frames of reference such as in his statements about >C expansion of the universe.
What I meant was:
SR is a theory. All theories have a scope of applicability. So trying to apply it outside of that scope may provide non-sensical results.
SR does say that an observer cannot create an experiment in which the speed of light is measured as other than c. SR does say that you cannot accelerate a galaxy faster than c. However, SR does not say that galaxies cannot be measured to recede from each other faster than c. That is in fact an application of SR outside of its scope.
That is why I said "if you know of somewhere an observer can measure the speed of light to be different than c, well, please enlighten us." This is in response to David's comment against SR: "Its 'speed limit of c' is not correct, and its constancy postulate is not correct." Even if the value of c changed over time, SR would still be correct. Because it is not a postulate of SR that the value of c has always been the same throughout the history of the universe. Just as it is not a postulate of SR than space cannot expand.
Here are a few comments by Newton about the ?big bang?, which he simply attributes to a ?Deity?,
http://vms.cc.wmich.edu/~mcgrew/Bent3.htm (Just so others have a reference; you want the other 3 letters, just change that '3' to a '1', '2', or '4')
Here he is basically saying that God must have been responsible for the expansion of the universe and the even distribution of matter.
I can see how the letter could be interpreted as expansion, though it seems a big stretch. In particular, because this phrase appears to be elucidating the statement "... the Hypothesis of Matter?s being at first evenly spread through the Heavens ..." (boldface mine)
But I cannot see how this could be reasonably described as projectile impulse because not only does the deity have to be responsible for the "flying up", but responsible for keeping them falling back down.
I don?t have time to type up all my books and put all their text on the internet.
I'm not asking you to do so; I do have access to a library that might have these things, should I know for what I'm looking. (though I admit it is awfully nice to quote passages; one reason why I strongly prefer internet resources in these debates is so that everyone has access to the references)
With gravity, the universe should contract, not expand
No; you're mixing up first and second derivatives. The rate of growth is what is required, by gravity (and Λ=0), to be decreasing.
Even Newtonian gravity has examples of eternal universal expansion.
But a myth has grown up in recent years that says he added it to keep the universe from ?expanding?. That is silly and it is just one of the many Einstein urban legends that have grown up in the past 30 years.
The focus is on the expansion because, of the cases with Λ=0, that is the one that turned out to be right.
I will note that you do need Λ>0 in order for expansion to be accelerating, a key ingredient of BBT.
but hypothetically, could a unverse be eternally contracting?
Einstein's field equations are symmetric under time reversal, aren't they? If they admit an eternally expanding solution, they must also admit an eternally contracting solution. (Of course, this doesn't suggest that there aren't other reasons why an eternally contracting universe is unreasonable. Boy, lots of negatives in that statement :smile:)
Yes they are time symmetric, but I don't think it necessarily follows from time symmetry that if in one model there has a certain state at t = 0 and and anothe rat t =infinity then there exists another model that has the same state that the first one had at t = infinity at t' = 0 and the same state as the first one had at t = 0 at t' = infinity because basically the first universe will never be in state t = infinity. Infact I think you find that at t' = 0 you have a universe that is in equilibrium, neither contracting nor expanding,
pallidin
May19-04, 11:48 PM
For the record, references I did find to "projectile impulse" suggest the idea of some object physically imparting momentum to the other object to propel it (or parts of it) into an interesting trajectory. (e.g. Godwin's "Essay XXI of Astronomy")
(Emphasis mine) Hurkyl, perhaps this is not relevant to this discussion, but you statement prompted me to offer this info.
Impulse force propagation does not behave in the same way as non-impulse.
It is very curious that this is the case, and it is not well understood by those researching it(NYU, NASA and others)
Apparently, constant force applied on object contact effects a generally linear propagation(we all know that), whereas the same force, segmented as an impulse, does not do this, rather exhibiting a non-linear contact propagation characteristic.
In general, an object hit by an quick impulse will experience a non-linear, spherical wave propagation of the force imparted to it.
This can lead to somewhat bizzare effects, especially if other "objects" of differring dimensions are involved in the contact scenario.
How this might relate to cosmological influence is unknown(to my knowledge), but certainly worthy of further inquiry.
russ_watters
May20-04, 01:03 PM
What I meant was... We're on the same page.
Michael F. Dmitriyev
May20-04, 02:49 PM
The velocity of light is unique, absolute and SINGLE speed existing in the nature.
So you're saying that its natural to assume that the universe is infinitely old and has been collapsing for an infinite amount of time, but has a finite amount of life left before collapsing completely?
No.
I never said that.
At one time, it was believed that the unvierse was eternal and static. But throwing gravity into that universe would indeed cause contraction: therefore the universe cannot be static. It must either be expanding or contracting. (or both).
Newton had two other suggestions:
Rotation or infinite.
We see that he was right about “rotation” on the local level, since the galaxies and solar systems rotate.
He was also apparently right about the expansion too.
David, it appears I gave you too much credit before in assuming you were just arging points you knew to be wrong for fun: you appear now to have some major gaps in your knowledge/understanding and a simple unwillingness to learn. Though it may be more pathological: you abuse/distort/misrepresent/mischaracterize to cover your unwillingness to learn.
LOL, you are the guy who told me that Lorentz and Einstein couldn’t have been talking about atomic clocks in their early papers, because you said atomic clock weren’t invented until the 1950s. Then I told you about Maxwell’s mention of natural atomic clocks in 1873.
geistkiesel
Jun6-04, 08:46 PM
Einstein said in his 1916 book:
”If an observer sitting in the position M1 in the train did not possess this velocity, then he would remain permanently at M, and the light rays emitted by the flashes of lightning A and B would reach him simultaneously, i.e. they would meet just where he is situated. Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A.”
What Einstein means by “he is hastening towards the beam of light coming from B” is that the light beam from the flash at B is converging on the observer that is moving toward B at the relative velocity of c + v, with v being the velocity of the observer toward B. What he means by “he is riding on ahead of the beam of light coming from A” means the light from the A flash is converging on the observer at the velocity of c – v.
This is very simple. The observer-relative speed of the light, relative to the moving observer is NOT “c”, it is NOT constant. It is c + v in one direction and c – v in the other direction.
This is why the earth sees a blueshift in the light of the star the earth is moving toward in its revolution around the sun and this is why the earth sees a redshift in the light of a star the earth is moving away from during its revolution around the sun. This is caused by the Second Cause of the Doppler effects that I told you about earlier. This is a Doppler Law of Physics. It can not be revoked.
I agree David. Instead of using light use crawling ants for the photons. Einstein would still come up with a loss of simultaneity as he concluded the loss of simultaneity as perceived by the observer on the moving platiofrm was the detection of the ant coming toward him from the front and then the ants comin toward him from the rear, and this is it!.
Of course you will need to restrict your speed to a constant values less than that of the ants so as not to embarrass Professor Einstein, graduate advisor to a host of SR theorists.
Tom Mattson
Jun6-04, 10:26 PM
Of course you will need to restrict your speed to a constant values less than that of the ants so as not to embarrass Professor Einstein, graduate advisor to a host of SR theorists.
There's no need for anyone to restrict the speed to something less than the Lorentz invariant speed. Nature will take care of that for you.
geistkiesel
Jun7-04, 12:15 AM
I’m talking about “physics”, not “science fiction stories”.
Good for you.
The reason the guy on the moving train will see the B flash first is because he is moving toward B and thus he and the light beam from B are converging on each other at the additive light-speed velocity of c + v. That’s a basic law of physics and of nature, and it’s a basic Doppler Law.
Oops, you just slid into sci-fi. Your "basic law of physics" is only an approximation, valid at low speeds.
Oh so SR theory gets to corrupt the basic laws of physics? I thought that even in SR theory the laws of physics were equivalent in all inertial frames.
Prove that what is observed to be true, is false.
Prove that a postulate, a mental arrangement, is superior to a direct observation such as described by David.
Let me see , your proof will start out as "SR theory says . . . ", What was the comment? " ..ooops" , wasn't it?
geistkiesel
Jun7-04, 12:17 AM
There's no need for anyone to restrict the speed to something less than the Lorentz invariant speed. Nature will take care of that for you.
Tom
I was referring to the substitution of moving ants for the photons, this is why I suggested the volunteered slowing to a speed lless than the ants.
Tom Mattson
Jun7-04, 03:47 AM
Oh so SR theory gets to corrupt the basic laws of physics?
No, it does the opposite. It says that the basic laws of physics are the same everywhere, everywhen, for everyone. That stands in stark contradiction to your crackpot idea that the laws of physics in our Earthbound frame are special and somehow Divine.
I thought that even in SR theory the laws of physics were equivalent in all inertial frames.
Now yer getting it.
Prove that what is observed to be true, is false.
That's your objective, not ours.
Prove that a postulate, a mental arrangement, is superior to a direct observation such as described by David.
If you think that David's thought experiment is a "direct observation", then you are just as stupid as he is.
Let me see , your proof will start out as "SR theory says . . . ", What was the comment? " ..ooops" , wasn't it?
No. The proof will start out as, "SR theory says.....and let's see what real experiments say in support or denial of that"
That's what all scientists do. You would do well to follow that example, as you don't seem to care if an experiment is real or imagined. All you seem to care about is whether the experiment agrees with your preconceived notions.
edit: fixed a quote bracket
geistkiesel
Jun7-04, 05:46 AM
No, it does the opposite. It says that the basic laws of physics are the same everywhere, everywhen, for everyone. That stands in stark contradiction to your crackpot idea that the laws of physics in our Earthbound frame are special and somehow Divine.
So if an observation that two photons are emitted simultaneously in a stationary frame and a moving frames say from A and B where M is the midpoint of A and B, just at the instant that identical points on the moving frame are such that A = A', B = B' and M = M' that this simultaeous event in both frames is not a simultaneous event?
I know I have crackpot ideas, WYSIWYG, but the earth bound frame is an inertial frame is it not? And is not the earth bound frame a part of the "everywhere" you refer to above?
I would never utter any statement that something is "somehow Divine". If I mentioned anything regarding 'divinity' I might say something "is Divine" and I might say that the laws of physics are Divine, whereever encountered, as in everywhere, but I fail to see any logical thread or relationship, relevance is what I am discussing, that justifies your use of words as you expressed them above.
Is it an old intuitive threat to professional security considerations that motivates your rather unscientific mode of response?
Special relativity is your mantra isn't it?
If you think that David's thought experiment is a "direct observation", then you are just as stupid as he is.
The experiments being discussed are as real as Einstein's when he presented his gedunkens. I would rather be as stupid as David than to be as stupid as you. his mind seems to work as a mind. It has the characteristics of being free, or working to that end. I don't recognize the characteristics of mind iassociated with your post. Brat robot is more what I observe.
quoting geistkiesel
No. The proof will start out as, "SR theory says.....and let's see what real experiments say in support or denial of that"
That's what all scientists do. You would do well to follow that example, as you don't seem to care if an experiment is real or imagined. All you seem to care about is whether the experiment agrees with your preconceived notions.
edit: fixed a quote bracket
So one gedunken cannot be used to counter another gedunken? That is the scientific rule where you come from? I would do well to follow that example?
So David's and Geistkiesel's observations don't wash in a mind soaked in SR theory? That doesn't sound like a Divine situation to me. I am going to speak to someine in authority about that, as soon as I can get 'his' attention, if you know what I mean. I'll get back to later on this.
When you wake up Tom everything will seem like a bad dream, but the bogie man will be gone, the things that go bump in the night will be no more and you can begin to live again, free at last.
russ_watters
Jun7-04, 07:29 AM
The experiments being discussed are as real as Einstein's when he presented his gedunkens. Tom pointed this out, but didn't explain (it really should be self-evident). Einstein's thought experiments were conceived as hypothetical examples in order to explain his theory, just as yours and David's are. The difference is that since it was concieved, Relativity has been substantiated by mountains of real, scientific evidence. Your ideas, on the other hand, exist only in your mind.So one gedunken cannot be used to counter another gedunken? That is the scientific rule where you come from? I would do well to follow that example? That's correct. Since a thought experiment isn't real, it doesn't prove or disprove anything.
Tom Mattson
Jun7-04, 11:25 AM
So if an observation that two photons are emitted simultaneously in a stationary frame and a moving frames say from A and B where M is the midpoint of A and B, just at the instant that identical points on the moving frame are such that A = A', B = B' and M = M' that this simultaeous event in both frames is not a simultaneous event?
You're asking me if a statement if the form, "If p, then p" is true. Of course it is, because it is an empty tautology.
I know I have crackpot ideas, WYSIWYG, but the earth bound frame is an inertial frame is it not? And is not the earth bound frame a part of the "everywhere" you refer to above?
The Earthbound frame is not inertial, but it is close enough. And yes, it is part of "everywhere".
I would never utter any statement that something is "somehow Divine". If I mentioned anything regarding 'divinity' I might say something "is Divine" and I might say that the laws of physics are Divine, whereever encountered, as in everywhere, but I fail to see any logical thread or relationship, relevance is what I am discussing, that justifies your use of words as you expressed them above.
You fail to see a lot of things.
Insisting that the laws of physics take their "textbook form" on Earth and insisting that the Lorentz transformation is wrong is logically equivalent to insisting that the laws of physics are the way we know them only on Earth.
Is it an old intuitive threat to professional security considerations that motivates your rather unscientific mode of response?
Just how would you even know what a scientific mode of response is? You don't even know the difference between a thought experiment and a real experiment.
Special relativity is your mantra isn't it?
No, physics is.
The experiments being discussed are as real as Einstein's when he presented his gedunkens.
Well, we agree on that much: Neither one is real at all.
I would rather be as stupid as David than to be as stupid as you.
Suit yourself. Suffice it to say that you got your wish.
his mind seems to work as a mind. It has the characteristics of being free, or working to that end.
Yes, his mind is "free" alright. It is so "free" that it is unconstrained by logic, science, mathematics, or evidence.
I don't recognize the characteristics of mind iassociated with your post. Brat robot is more what I observe.
Your vision is obviously clouded then. As I said, there is a difference between real experiments and thought experiments, which you don't see.
So one gedunken cannot be used to counter another gedunken? That is the scientific rule where you come from? I would do well to follow that example?
You say that to mock me, but the statement is correct. Thought experiments cannot disprove theories. Period.
Scientific theories are deductive arguments built up from statements which are the conclusions of inductive arguments. Those inductive arguments are based on experimental evidence. Given that, you can disprove a theory in one of two ways:
1. Show that the theory is not deductively valid.
2. Show that one or more of the premises is false.
#1 can be done with mathematics and #2 can be done with evidence. Neither can be done with a thought experiment.
So David's and Geistkiesel's observations don't wash in a mind soaked in SR theory?
What observation????
That doesn't sound like a Divine situation to me. I am going to speak to someine in authority about that, as soon as I can get 'his' attention, if you know what I mean. I'll get back to later on this.
Don't bother. It won't be worth reading anyway.
When you wake up Tom everything will seem like a bad dream, but the bogie man will be gone, the things that go bump in the night will be no more and you can begin to live again, free at last.
Get a clue. You haven't referred to a single real experiment. All you have referred to are thought experiments, which you falsely believe are just as good. They aren't.
You know, you and David would both do well to read posts from people such as Wisp and Yogi. They aren't convinced of SR either, but they refer to real, actual, factual experiments that have taken place in the physical world, not in warped minds. While I don't agree with them, it's not as though I dismiss anti-SR posts out of hand. I don't. I acknowledge that there are competent critics of SR out there.
You and David just aren't among them. :frown:
Michael F. Dmitriyev
Jun7-04, 10:48 PM
Velocity of light is absolute and SINGLE velocity existing in the universe at microlevel.
Relativity appears at macrolevel.
but he's talking about some superluminal things emitting light back to earth, which i find intriguing
if something going 4c to the left "emits" a photon to the right isn't that photon still going 3c to the right?
this slowing down to 0 speed then accelerating towards the left until it hits c in that direction is just odd
i don't think i can buy that
how about the one theory where light has a wave component and a matter component? Using that one the matter part could be emitted to the left at c, but the wave part is stretched to the magnitude of 3c to the right (redshifting) due to superluminal emitter...
this seems consistant
btw: i believe in einstein's setup he WAS referring to doppler shift, not relativistic observation. it seems way more simple than relativity.
geistkiesel
Jun8-04, 06:19 AM
Velocity of light is absolute and SINGLE velocity existing in the universe at microlevel.
Relativity appears at macrolevel.
Michael,
I have a problem. I am under the belief that an electromagnetic sphere whose radius is expanding at velocity c will have a diameter of 2c after 1 second. This sounds suspiciously close to the statement that the photons moving in opposite directions to each other are expanding at a rate of 2c. I was told in no uncertain terms that I erred, but I ws not given any direction to solving my dilemma.
I want to beleive llike everybody else. What is the rroof? That the sphere is expanding at a rate of 2^1/2c?, which is what I was told. Do you know?
Michael F. Dmitriyev
Jun8-04, 08:12 AM
A photon being a bit of matter can be rewriting at a new place with the maximal speed.
The particles, as a words, sentences and the combination of words and sentences demands a greater time of rewriting according to their length. It is a most simple way to understand why any material object cannot exceed the velocity of light.
Michael F. Dmitriyev
Jun8-04, 08:27 AM
Michael,
I have a problem. I am under the belief that an electromagnetic sphere whose radius is expanding at velocity c will have a diameter of 2c after 1 second. This sounds suspiciously close to the statement that the photons moving in opposite directions to each other are expanding at a rate of 2c. I was told in no uncertain terms that I erred, but I ws not given any direction to solving my dilemma.
I want to beleive llike everybody else. What is the rroof? That the sphere is expanding at a rate of 2^1/2c?, which is what I was told. Do you know?
Relativity cannot be applied to the light.
I have a problem. I am under the belief that an electromagnetic sphere whose radius is expanding at velocity c will have a diameter of 2c after 1 second. This sounds suspiciously close to the statement that the photons moving in opposite directions to each other are expanding at a rate of 2c. I was told in no uncertain terms that I erred, but I ws not given any direction to solving my dilemma.
As I mentioned in another thread, there is no problem whatsoever in having someone observe two photons separating at a rate of 2c. In fact, if the photons are moving in opposite directions, relativity insists that this be the case. :smile:
Note that the observed speed of each photon is still c.
russ_watters
Jun8-04, 09:04 AM
As I mentioned in another thread, there is no problem whatsoever in having someone observe two photons separating at a rate of 2c. In fact, if the photons are moving in opposite directions, relativity insists that this be the case. :smile:
Note that the observed speed of each photon is still c.Note also that an observer traveling just behind one of those photons, just under C, still sees each photon traveling at C.
"Separation velocity" isn't a velocity that has any SR implications. Its just geometry.
If I may change the thought experiment slightly to make it resolvable...
Take 3 observers, x, Y, & Z starting out next to each other:
XYZ
X and Z move away from Y at just under the speed of light.
X<----Y---->Z
Observer X measures both Y and Z to be moving away from him at just under the speed of light - Z is just a little closer to the speed of light than Y. Observer Z measures the same thing about X and Y. Observer Y measures both to be just under C.
Geometrically adding the speeds gives X and Z a "separation velocity" of just under 2C from the frame of reference of Y. But that doesn't in any way imply that Z or X will measure their own velocity with respect to each other at just under 2c.
"Separation velocity" isn't a velocity that has any SR implications. Its just geometry.
Right. Don't confuse this "separation velocity" with a relative velocity.
As another example: Someone (observer A) observes two rockets (B and C) traveling in opposite directions, each with speed 0.9c. The "separation velocity" of the two rockets, as observed by A, is 1.8c. But the speed of C as observed by B (the velocity of C with respect to B) is only 0.994c.
Note also that an observer traveling just behind one of those photons, just under C, still sees each photon traveling at C.
Einstein revoked his “constancy” postulate in 1912. Why don't you know this? Haven't you read his 1912 papers?
Right. Don't confuse this "separation velocity" with a relative velocity.
As another example: Someone (observer A) observes two rockets (B and C) traveling in opposite directions, each with speed 0.9c.
Lorentz said that based on electrodynamics, there is a “speed limit” in local gravity fields. You can’t accelerate a rocket in the solar system to .9c. What you are posting here is urban legend. Why does Bernhardt Media promote urban legends?
Michael,
I want to beleive llike everybody else.
You want to be brainwashed about relativity “like everybody else”??
Go out and by the complete 8 Volume set of “The Collected Papers of Albert Einstein”, Paperback English edition, Princeton Press, and you will see that these “mentors” don’t know what they are talking about.
Einstein revoked his “constancy” postulate in 1912. In 1907 he said that objects really don’t “geometrically” contract due only to “relative motion”. The distant galaxies exhibit redshifts that indicate they are moving at 2c and 3c relative to the earth. What these guys here are pushing is a bunch of rumors and urban legends suitable for teenagers.
I agree David. Instead of using light use crawling ants for the photons. Einstein would still come up with a loss of simultaneity as he concluded the loss of simultaneity as perceived by the observer on the moving platiofrm was the detection of the ant coming toward him from the front and then the ants comin toward him from the rear, and this is it!.
Of course you will need to restrict your speed to a constant values less than that of the ants so as not to embarrass Professor Einstein, graduate advisor to a host of SR theorists.
When Einstein said, “Events which are simultaneous with reference to the embankment are not simultaneous with respect to the train, and vice versa (relativity of simultaneity).”
But everybody knew that already. This is why the railroads divided the country up into four time zones in the 19th Century, to try to bring some simple form of “simultaneity” to the rail system. Before then, everybody was using local time set at noon by sundials in every city, and railroad conductors had to convert railroad time into local time, because the two lacked “simultaneity”.
In 1916 he said, “Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A.”
Everybody knew that already too. That’s about as obvious as saying, “The front of the train will arrive at the station before the rear of the train.”
If we are closer to one of two simultaneous events, we will receive light or sound signals from the closest event first. If we are right in between the two simultaneous events, we will receive light or sound signals from both events at the same time. Doh. People have known this for thousands of years. People have known that all kinds of clocks slow down due to different natural effects, and they've known that for thousands of years.
This Einstein stuff is over promoted by guys who like to think they are "as smart as Einstein". It's a cult.
This reminds me of the movie, “Being There”. Review comments: “It is hysterically funny to see how the always immaculately dressed, in formal attire, Chance rises to national prominence, due to people reading more into his stated "few simple truisms," and then giving the credit of a deep thinker to Chance, who is simply stating what he understands, in a calm, confident, positive, reassuring manner.”
“Benjamin Rand takes a shine to the person he believes is "Chauncey Gardner;" a simpleton he takes as an enigmatic and deeply contemplative thinker. Rich and powerful Ben introduces him to the President, to whom Chance makes cryptic comments that the president takes as a wise analogy of the seasons and the economy. A national TV appearance spreads "Chauncey's" fame. The only person who knows him, the "old man's" kindly maid, sizes up Chance's words: gobbledygook. The rich and powerful assume "Chauncey's" simple words imply great intelligence. Ben's doctor suspects that Chauncey may in fact have a child's mind, but is not certain.”
There's no need for anyone to restrict the speed to something less than the Lorentz invariant speed. Nature will take care of that for you.
Hey, Mr. X-Ray, look at this:
“Thus for the largest known redshift of z=6.3, the recession velocity is not 6.3*c = 1,890,000 km/sec. It is also not the 285,254 km/sec given by the special relativistic Doppler formula 1+z = sqrt((1+v/c)/(1-v/c)). The actual recession velocity for this object depends on the cosmological parameters, but for an OmegaM=0.3 vacuum-dominated flat model the velocity is 585,611 km/sec. This is faster than light.”
http://www.astro.ucla.edu/~wright/doppler.htm
Hey, the 99 year old hoax is over.
. In fact, if the photons are moving in opposite directions, relativity insists that this be the case.
No it doesn’t. Read Einstein’s 1911 and 1916 papers. Read his 1912 papers. He said light speed is slower than “c” inside a gravity field. He said that light speed is NOT “constant”.
Look, you’ve got to spend more money on relativity books than you spent on the two $9.95 books, “The Principle of Relativity” and “Relativity: The Special and General Theory”.
You’ve got to read some of Einstein’s subsequent papers. You’ve got a $19.90 “relativity” education, and it shows.
ahrkron
Jun20-04, 11:54 PM
Hey, Mr. X-Ray, look at this:
“Thus for the largest known redshift of z=6.3, the recession velocity is not 6.3*c = 1,890,000 km/sec. It is also not the 285,254 km/sec given by the special relativistic Doppler formula 1+z = sqrt((1+v/c)/(1-v/c)). The actual recession velocity for this object depends on the cosmological parameters, but for an OmegaM=0.3 vacuum-dominated flat model the velocity is 585,611 km/sec. This is faster than light.”
http://www.astro.ucla.edu/~wright/doppler.htm
Hey, the 99 year old hoax is over.
The same page, from UCLA, has a link from the phrase "faster than light" that takes you to an explanation of why this does not violate SR. You just chose not to see it.
For others that may wonder how that works, here (http://www.astro.ucla.edu/~wright/cosmology_faq.html#FTL) is the link.
ahrkron
Jun21-04, 12:20 AM
No it doesn’t. Read Einstein’s 1911 and 1916 papers. Read his 1912 papers. He said light speed is slower than “c” inside a gravity field. He said that light speed is NOT “constant”.
Even assuming that you were not quoting papers from the time GR was under development, nowhere near its final form, where did Doc Al or geistkiesel mention anything about GR, or a gravity field?
Also, you would be much better off dropping your "$9.95" argument. As some of us have pointed out to you already, getting a real education on current physics takes quite a bit more (money, time and effort) than those involved in buying and reading the collected papers of AE, who died in 1954.
And, as you say, it shows.
russ_watters
Jun21-04, 12:22 AM
Einstein revoked his “constancy” postulate in 1912. Why don't you know this? Haven't you read his 1912 papers?
What does this discussion have to do with Einstein? He's dead. :wink:
ahrkron
Jun21-04, 12:27 AM
When Einstein said, “Events which are simultaneous with reference to the embankment are not simultaneous with respect to the train, and vice versa (relativity of simultaneity).”
But everybody knew that already. This is why the railroads divided the country up into four time zones in the 19th Century, to try to bring some simple form of “simultaneity” to the rail system. Before then, everybody was using local time set at noon by sundials in every city, and railroad conductors had to convert railroad time into local time, because the two lacked “simultaneity”.
Wow!! This is just beautiful. I'm sorry David, but as I said, "it shows". You do not seem to understand what the issue with simultaneity is.
ahrkron
Jun21-04, 12:44 AM
In 1916 he said, “Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A.”
Everybody knew that already too. That’s about as obvious as saying, “The front of the train will arrive at the station before the rear of the train.”
If we are closer to one of two simultaneous events, we will receive light or sound signals from the closest event first. If we are right in between the two simultaneous events, we will receive light or sound signals from both events at the same time. Doh. People have known this for thousands of years.
Again, as you did with your quote of UCLA's page, you are stopping just before things get interesting.
Of course people knew about sound arriving first from the closest source. The thing that changes all else is the fact that, unlike sound, light will be measured to have the same speed by both observers. From there, a little algebra takes you to Lorentz transformations, showing, along the way, their logical linkage to a measured phenomenon (the constancy of the speed of light).
People have known that all kinds of clocks slow down due to different natural effects, and they've known that for thousands of years.
Sure, but nobody before the uderstanding of Lorentz Transformations was able to correctly predict the slowing down caused by relative motion.
Your (failed attempt of a) rebuttal is akin to this:
[someone] Mr. X has discovered that gene Y is the cause of cancer.
[you] Nay! People have known that all kinds of persons die due to different natural effects, and they've known that for thousands of years.
geistkiesel
Jun21-04, 06:16 AM
David said:
In 1916 he said, “Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A.”
Everybody knew that already too. That’s about as obvious as saying, “The front of the train will arrive at the station before the rear of the train.”
If we are closer to one of two simultaneous events, we will receive light or sound signals from the closest event first. If we are right in between the two simultaneous events, we will receive light or sound signals from both events at the same time. Doh. People have known this for thousands of years.
Again, as you did with your quote of UCLA's page, you are stopping just before things get interesting.
Of course people knew about sound arriving first from the closest source. The thing that changes all else is the fact that, unlike sound, light will be measured to have the same speed by both observers. From there, a little algebra takes you to Lorentz transformations, showing, along the way, their logical linkage to a measured phenomenon (the constancy of the speed of light).
I agree with David!
The Einstein Train gedanken from another view. Read at your peril.
______________________________________________
All moving frame values are non-primed with the exception of M’, the consistent location of the observer O in the moving frame.
At no time is there an inference that M’ was at the midpoint of the A and B photons emitted in the stationary frame.
To demonstrate the following:
Einstein’s moving train calculation indicating when the oncoming B photon is detected at t1 the A photon was located at a position consistent with –t1. Said in other words, as t1 is determined from t0 which locates M’ at t0, the A and B were equidistant to M’(t0) when t = t1.
Proof:
A moving observer located at M’ on a moving frame passes through the midpoint M of photon sources located at A and B in the stationary frame just as A and B emit photons. M’ is moving along a line connecting A and B, toward B.
At this instant the moving source t = t0. Later the moving observer detects the photon from B at t1, and later the photon from A at t2. The observer has measured her velocity wrt the stationary frame as v. Determine the position of the A photon at tx in terms of t0, t1, t2, and v when the B photon was detected at t1.
The photon from A must reach the position of M’ when t = t2. Therefore, the distance traveled by the A photon during Δt = t2 – t1, is Δtc. This is equal to the distance cΔt = vΔt + vt1 + vtx . Now we rearrange somewhat to arrive at, vtx = vΔt – cΔt + –vt1. Now as vΔt - cΔt is just -vtx - vt1
vtx = -vtx - vt1 – vt1
2tx = -2t1
tx = -t1
Therefore, in the moving frame the photon from A and the photon from B were equidistant from M’(t0) at t1.
Ingvar Astrand
Jul12-04, 08:33 AM
“Thus for the largest known redshift of z=6.3, the recession velocity is not 6.3*c = 1,890,000 km/sec. It is also not the 285,254 km/sec given by the special relativistic Doppler formula 1+z = sqrt((1+v/c)/(1-v/c)). The actual recession velocity for this object depends on the cosmological parameters, but for an OmegaM=0.3 vacuum-dominated flat model the velocity is 585,611 km/sec. This is faster than light.”
To David (I like your energy) and other interested.
Redshift is not a recession velocity question. The kinematic mechanism behind is the entropy-effect that Clausius coined for the notion he invented when he searched the cause and reason to why heat-radiation moved to equilibrium.
Planck and his colleagues found the cause and reason but didn’t understand how to interpret the constant fractional increasing change between the electrodynamical wave-units. Desperate Planck tried to interpret the value that was measured as differences between wavelengths as continuing change in energy. To do so he inverted the fractional value to the temperature’s change over the frequency spectrum. Wien and Stefan–Boltzmann laws have showed that there is a relation between temperature and wavelengths, but Planck had got lost in his derivation. Einstein later suggested (postulated) that this mathematical artifact “must” be interpreted as quantum-unit.
Planck’s measured value 6.626 x 10^-34 tells us how much an electrodynamical wave is extended from wave to wave or proportional to the distance. This is the simple formula (redshift = constant x distance). So the distance to this 6.3 (6.28) quasar that is redshifted from (1216 to 7636 Angstrom) is: (6.420 x 10^-10 km) / (6.626 x 10^-34) = 9.7 x 10^23 km. The distance defined as light-years -- that is 0.95 x 10^13 km per light-year -- to this 6.28-quasar is near 1000 billion light years.
A quasar’s energy that we receive is proportional to the redshift (energy = z^4). So this 6.28 quasar emits at the wavelength 1216 Angstrom 1555 times more energy than we receive at 7636 Angstrom. This energy drives the light (waves) forward.
When electrodynamic waves increase their lengths their velocities also increase to this simple formula [c + (2c x redshift)^-2]. So the 6.3 quasar’s wavelength of 7636 Angstrom that we receive moves [(2 x 3 x 10^5 x 7.636^-10)^-2] km/s = 0.045 km/s faster than c.
The light-spectrum that we se as stroboscope-frozen moves at the velocity of light, but we can not see that the waves increase their speed with their wave-displacement. But we can understand it when we see the increasing wavelengths between the water-rings from the pebble that is thrown in the water.
Ingvar Astrand, Sweden
terrabyte
Jul14-04, 12:16 AM
Note also that an observer traveling just behind one of those photons, just under C, still sees each photon traveling at C.
"Separation velocity" isn't a velocity that has any SR implications. Its just geometry.
If I may change the thought experiment slightly to make it resolvable...
Take 3 observers, x, Y, & Z starting out next to each other:
XYZ
X and Z move away from Y at just under the speed of light.
X<----Y---->Z
Observer X measures both Y and Z to be moving away from him at just under the speed of light - Z is just a little closer to the speed of light than Y. Observer Z measures the same thing about X and Y. Observer Y measures both to be just under C.
Geometrically adding the speeds gives X and Z a "separation velocity" of just under 2C from the frame of reference of Y. But that doesn't in any way imply that Z or X will measure their own velocity with respect to each other at just under 2c.
Hmm?
Assuming a start of:
XYZ
and then a process of:
X<------Y------>Z
given 1 second with seperations speeds of c all around X is 300,000 from Y which is 300,000 from Z.
i'm not seeing how you're saying from X's perspective Y is 290,000 from X and Z is 300,000 from X :|
are you sure you know what you're doing?
zoobyshoe
Jul14-04, 12:47 AM
Einstein revoked his ?constancy? postulate in 1912. In 1907 he said that objects really don?t ?geometrically? contract due only to ?relative motion?.
David,
If you could quote these two things verbatim for us, I think it would be of great interest to everyone.
Were these published statements, or things he said in letters, or just things he had in his notes?
russ_watters
Jul14-04, 09:38 AM
given 1 second... 1 second according to whom? X,Y, and Z will not agree on when that second has passed.
And those distances: according to whom? X,Y, and Z will not agree on the distances traveled.
Hey, Mr. X-Ray, look at this:
“Thus for the largest known redshift of z=6.3, the recession velocity is not 6.3*c = 1,890,000 km/sec. It is also not the 285,254 km/sec given by the special relativistic Doppler formula 1+z = sqrt((1+v/c)/(1-v/c)). The actual recession velocity for this object depends on the cosmological parameters, but for an OmegaM=0.3 vacuum-dominated flat model the velocity is 585,611 km/sec. This is faster than light.”
http://www.astro.ucla.edu/~wright/doppler.htm
Hey, the 99 year old hoax is over.
It's this kind of buffonery that makes it obvious, that it's you're understanding of special relativity not special relativity itself that is flawed. Notrice that the special relativistic interpreation gives an answer of below c, in fact it is impossible using purely special rleatyivity to interpet a redshift as a relative velocity of above c, if this is the case you start to get imagibnary numbers for physical quantities that can be directly observed.
The effect is general relativistic
terrabyte
Jul14-04, 10:39 AM
...that doesn't sound very convenient at all.
supposing we have a "stationary" length of matter. 600,000 km long with huge metal plates on either end. we have a light source at the midpoint Y. given 1 second "according to Y" will the light have reached both the plates on either ends 300,000 km distant? (for simplicity assume 300,00km/s is light speed)
supposing we have a "stationary" length of matter. 600,000 km long with huge metal plates on either end. we have a light source at the midpoint Y. given 1 second "according to Y" will the light have reached both the plates on either ends 300,000 km distant? (for simplicity assume 300,00km/s is light speed)
Observers in the Y frame (who are at rest with respect to those metal plates) would say yes. So, according to Y frame measurements, the light arrives at each plate simultaneously. Of course, observers in other frames (that are moving with respect to Y) will measure the light to arrive at each plate at different times according to their clocks.
terrabyte
Jul14-04, 12:34 PM
so you're saying the moving people's clocks are screwed up, but in reality the light does reach the plates in 1 second...
so you're saying the moving people's clocks are screwed up, but in reality the light does reach the plates in 1 second...
Not at all. Everyone is perfectly entitled to view themselves to be at rest and the others as moving. No one is entitled to say that they are the one who is really at rest. Measurements of time, length, and simultaneity are frame-dependent. Measurements made by X or Z are just as useful and valid as any made by Y.
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