The Doppler Effect and the Velocity of Light in Einstein's Theory

[David]

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 possesses 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.

 

[yogi]

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)

 

[David]

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]

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.

 

[David]

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]

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.

 

[Doc Al]

Read the relativity section! - LOL

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?

 

[David]

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.

 

[David]

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?

 

[Doc Al]

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]

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?

 

[Doc Al]

relativistic Doppler formula

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.

 

[David]

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.

 

[David]

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.

 

[David]

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.

 

[Doc Al]

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".

 

[jcsd]

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 relativity 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.

 

[David]

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.

 

[David]

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".

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.

 

[DrChinese]

... 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?

 

[David]

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.

 

[David]

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.

 

[jcsd]

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]

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]

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.

 

[David]

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]

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).

 

[David]

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.

 

[David]

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]

...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.

 

[jcsd]

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.

 

[David]

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.

 

[jcsd]

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.

 

[Hurkyl]

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.

 

[David]

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.