Measuring The Relative Velocity Of Light

[grounded]

No it is not because accelartion is npot relative in the same way asvelcotiy is relative you can't transform an accelarated frame into an inertail frame in special relatvity.

Is not the change in distance between the observer and the source (at any point) the same to the observer as is it is to the source?

 

[grounded]

According yo you: true wavelength is 1 km, but true frequency is still 600,000 Hz

True frequency is measured while at rest relative to the source.

While in motion, the frequency is relative. Traveling towards the train will increase the number of boxcars that are passed and it will increase the relative speed between the observer and the train, but it will not change the length of the boxcars.

Frequency is relative
Speed is relative
Wavelength is NOT relative

 

[jcsd]

Is not the change in distance between the observer and the source (at any point) the same to the observer as is it is to the source?

The instanateous relativce velcoities are the same, but the accelartions are different.

 

[grounded]

The instanateous relativce velcoities are the same, but the accelartions are different.

I see what you mean, and I agree, if you mean that one will feel the change in velocity and the other will not.

 

[ram1024]

to say that a wavelength <of light> is not relative must mean that everything you can measure it with is not realative as well. ie> length contraction does not exist.

i don't think it exists either, but maybe you have a different explanation?

 

[wespe]

I say I am extremely interested in learning about a real world experiment such as you described, minus the spaceship. Remember, it must be done while in motion relative to the source. A link describing the details of the experiment would be appreciated.

Grounded...

I am simply saying that by "correcting" the measured wavelength, you are creating a paradox.

Please do consider:

Assume, once again, according to the light source: the frequency is 300,000 Hz and wavelength is 1 km.

Assume, the approaching observer measures: frequency as 600,000 Hz and wavelength as 0,5 km

You say: "Current measurments of frequency already include the distance the observer has traveled relative to the source"
So, we will NOT correct the measured frequency, right? So we have this number: 600,000 Hz

You say: "We do not include it when measuring wavelength"
So, we WILL correct the measured wavelength, right? So we get this corrected number: 1 km

Now, how will we calculate the relative speed of light wrt us? By multiplying the wavelength by frequency, right?
So we calculate 600,000 Hz x 1 km = 600,000 km/sec, right?

You say we think relative speed never changes, because we don't correct the wavelength, right? So, when we use the corrected wavelength, we find 600,000 km/sec. OK?

Now, I am telling you that the relative speed can be measured directly, without measuring wavelength or frequency, just by timing the passage of light over a distance. And, this directly measured relative speed is ALWAYS equal to 300,000 km/sec. This is confirmed by REAL experiments.

Therefore, the calculated relative speed with the "corrected" wavelength" is WRONG.
The calculated relative speed without any corrections to wavelength is CORRECT.
Therefore, correcting wavelength as you want is WRONG.

Now please just tell me which argument above you think is faulty.

Is it only the "This is confirmed by REAL experiments" part? Will you be convinced if there were such real experiments?

 

[wespe]

True frequency is measured while at rest relative to the source.

While in motion, the frequency is relative. Traveling towards the train will increase the number of boxcars that are passed and it will increase the relative speed between the observer and the train, but it will not change the length of the boxcars.

Frequency is relative
Speed is relative
Wavelength is NOT relative

What you are saying is approximately correct for slow trains. But if you increase the relative speed of a train close to the speed of light, it isn't correct anymore.

Because, as the speed increases, length contraction effect becomes more, and the length of the train cars are no longer measured the same; it is measured much less.

And when you reach exactly light speed (not possible for trains), the relative speed becomes constant, wavelength and frequency becomes variable [for light] *

So is it just that you don't buy length contraction? What about time dilation?

Edit:
* I'm not so sure about this part. Here's what I thought: Suppose a rocket is launched from Earth and achieves a relative speed of 299,000 km/sec wrt earth. Then, a second rocket is launched in the same direction and achieves a relative speed of 298,000 km/sec wrt earth. What is the relative speed between the rockets as measured by the rockets?

http://math.ucr.edu/home/baez/physics/Relativity/SR/velocity.html
The formula at the end of the page is:
w = |ux - vx| / (1 - ux vx/c2)

I calculated it will be around 100,000 km/sec. So I thought: as the speed of the first rocket approaches 300,000 km/sec, this value will also approach 300,000 km/sec, and at the limit it will be constant just like light.

 

[David]

Because, as the speed increases, length contraction effect becomes more, and the length of the train cars are no longer measured the same; it is measured much less.

snip

So is it just that you don't buy length contraction? What about time dilation?

“Assertions about the shape of a body in nonaccelerated motion therefore have a direct meaning. The shape of a body in the sense indicated we will call its ‘geometric shape.’ The latter obviously does not depend on the state of motion of a reference frame.” A. Einstein, 1907 Vol. 2 of Collected Papers.

He backed down on length contraction. He changed his mind. Read his own papers and stop believing internet rumors posted on websites like this one.

 

[David]

By 1911-12, Einstein retracted his light speed “constancy” postulate. For example, in the 1912 paper, “The Speed of Light and the Statics of the Gravitational Field,” he said:

“But at the same time it turned out that one of the basic principles of that theory, namely, the principle of the constancy of the velocity of light, is valid only for space-time regions of constant gravitational potential. Even though this result rules out the universal applicability of the Lorentz transformation, it should not frighten us away from the further pursuit of the path we have taken...”

And in the 1912 paper, “Relativity and Gravitation”, he says:

“Abraham notes that I have delivered the coup de grace to the relativity theory by abandoning the postulate of the constancy of the velocity of light and by the therewith connected relinquishment of the invariance of the systems of equations with respect to the Lorentz transformations.”

This was in response to statements that Max Abraham published in the Annalen der Physik:

“Already before a period of one year, A. Einstein, by accepting an influence of the gravitation potential on the speed of light, gave up the postulate of the constant speed of light essential for his earlier theory 1); in a work appeared recently 2)...”

So, the famous “constancy” postulate of the 1905 SR theory did not exist after 1912, and it doesn’t exist today.

In the 1912 paper, “Theory of Relativity”, as published in “Physik”, Emil Warburg, Leipzig, 1915, he said this about the SR theory:

“Finally, one more important question: Does the theory of relativity possesses unlimited validity? Even the supporters of the theory of relativity have different views on this question. The majority are of the opinion that the propositions of the theory of relativity – especially its conception of time and space – can claim unilmited validity.

However, the writer of these lines is of the opinion that the theory of relativity is still in need of a generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned.”

Stop believing rumors and urban legends.

 

[wespe]

“Assertions about the shape of a body in nonaccelerated motion therefore have a direct meaning. The shape of a body in the sense indicated we will call its ‘geometric shape.’ The latter obviously does not depend on the state of motion of a reference frame.” A. Einstein, 1907 Vol. 2 of Collected Papers.

He backed down on length contraction. He changed his mind. Read his own papers and stop believing internet rumors posted on websites like this one.

I don't know if he changed his mind, maybe while developing the theory? I don't know. But please see:

http://www.bartleby.com/173/10.html

"Thus the length of the train as measured from the embankment may be different from that obtained by measuring in the train itself"

Isn't this book dated 1920?

 

[wespe]

“Already before a period of one year, A. Einstein, by accepting an influence of the gravitation potential on the speed of light, gave up the postulate of the constant speed of light essential for his earlier theory 1); in a work appeared recently 2)...”

So, the famous “constancy” postulate of the 1905 SR theory did not exist after 1912, and it doesn’t exist today.

Well you got me there; I don't know much about GR.

But, I thought speed of light is measured constant even under the influence of gravity.

Are you sure these aren't out-dated historical records?

What do you say about that 1920 book?

 

[ahrkron]

David,

It is a well known fact that AE tried various models before arriving to what we now know as GR, aknowledged and understood both by biographers, like Abraham Pais, and by those who study the origins of relativity, like John D. Norton. It is not new (or any kind of "big secret") that there were contradictions in his papers from that period. You are precisely choosing papers from before 1916, which is roughly when he arrived to the theory's final form.

If you are going to put so much weight on AE own words, why don't you at least use the version that he regarded as the best way to put things together? otherwise, you seem to be trying to advocate for the ideas that AE, and many others now, understood to be faulty.

 

[swansont]

While in motion, the frequency is relative. Traveling towards the train will increase the number of boxcars that are passed and it will increase the relative speed between the observer and the train, but it will not change the length of the boxcars.

Frequency is relative
Speed is relative
Wavelength is NOT relative

Argument by analogy is a dangerous thing, because if you take the analogy too far you can reach erroneous conclusions. Consider the possibility that light and trains might behave differently.

 

[grounded]

Argument by analogy is a dangerous thing, because if you take the analogy too far you can reach erroneous conclusions. Consider the possibility that light and trains might behave differently.

It’s not that they behave differently, it’s that we calculate them differently.

If you measure the train like we measure the light, then the speed of the train will never change.
If you measure the light like we measure the train, then the length of the boxcar will never change.

What are your thoughts on post #141?

 

[reilly]

Reilly, I don't know if you have read all of the posts Grounded has made in this thread, but a cursory examination will show you that he making a most robust effort to teach you something, but your instincts seem to be to throw the dust of whatever subtle discouragement you have to the man. Condescending, superior intelligence, education and wit you know the attitue, don't you?. When you understand what he is saying, meaning you have to read it of course, you can understand his tenacity he has built into the model he his presenting.

Again, Reilly. he is teaching you something. Physics isn't so difficult, but useless phyiscs is very difficult, don't you agree?.

With all due respect, there's a cottage industry, almost 100 years old, devoted to proving Einstein wrong. I've been familiar with this industry about 40 years, so, in fact, I've encountered arguments like yours and Grounded's numerous times. They don't change much from year-to-year, and they virtually all attempt to prove that the basic Einstein description of space time via the Lorentz transformation is wrong. After all, there are only so many ways to attack the Lorentz transformation in its space-time version. Physics departments around the world every week get many letters outlining ideas like your and Grounded's. Nonetheless SR is alive and well in its world of inertial frames.

One difference between the anti-Einstein folks and the standard physics community is that the history of standard physics is recorded and open to all. There appears to be little or no extant history of the anti-Einstein movement, so people keep doing the same things over and over and over, never learning from their forbearers, and seldom learning the true extent of SR in physics today. Those who neglect history are doomed to repeat it.

I've seen a few attempts to get at E=mc**2, but not many. I've never encountered an attack on, say, the successful use of SR in accelerator design, or the relativistic description of electron-proton scattering, or the Thomas precession, and on-and-on. What the anti-Einstein folks don't realize is that SR is fundamental to physics in thousands of ways, and has been 'verified' thousands of times -- if SR were wrong, physics today would be very different than it is.

Those of you who, for one reason or another, choose to attack SR would be well advised to develop a good sense of the myriad ways in which it has been tested - and SR has yet to fail. The freshman physics version of SR is fallow territory. The vulnerabilities, if there are such, are in the far more difficult, albeit subtle parts of physics, like providing a rigorous formulation of the relativistic dynamics of a gas, in either classical or quantum form. Perhaps the difficulties of quantum field theory might be another point of attack.

Relativistic kinematics is, in my judgment, the bedrock of experimental tests of SR. Pauli's successful conjecture of the neutrino depended totally on the validity of SR. Key experiments like the discovery of the Omega minus particle, which confirmed the correctness of an important SU3 multiplet, the experiments elucidating the K meson system, and all the experiments demonstrating the correctness of the quark hypothesis require the utility and correctness of SR.

If, after 40 years of perusing anti-SR arguments, I have anything to learn it is first, why do people go after Einstein? Why do they not learn from history? And why do they not attack relativistic kinematics? -- remember that there is a strong duality in both classical and quantum physics between position and momentum, time and energy. Enough.
Regards,
Reilly Atkinson

 

[russ_watters]

If, after 40 years of perusing anti-SR arguments, I have anything to learn it is first, why do people go after Einstein? Why do they not learn from history? And why do they not attack relativistic kinematics? -- remember that there is a strong duality in both classical and quantum physics between position and momentum, time and energy. Enough.

I have wondered this too (though only for about 2 years ). The best I can think of is that Einstein's Relativity is the first thing they hear about that they can't get their arms around - and they never get past it. They simply can't accept reality at face value.

 

[Nereid]

I have wondered this too (though only for about 2 years ). The best I can think of is that Einstein's Relativity is the first thing they hear about that they can't get their arms around - and they never get past it. They simply can't accept reality at face value.

But why aren't there similar or greater volumes of attacks on QFT/QM? That's surely far weirder (is that a word?). Maybe it has something to do with AE vs a big mob (Heisenberg, Dirac, Pauli, Schrödinger, Bohr, ...)?

 

[wespe]

But why aren't there similar or greater volumes of attacks on QFT/QM? That's surely far weirder (is that a word?). Maybe it has something to do with AE vs a big mob (Heisenberg, Dirac, Pauli, Schrödinger, Bohr, ...)?

Being one of them myself formerly, I guess, quantum theory talks about small intangible things and people can't think of counter examples for them. Not so when you talk about trains, lightenings, twins..

 

[swansont]

It’s not that they behave differently, it’s that we calculate them differently.

Really? Trains follow Maxwell's equations?

If you measure the train like we measure the light, then the speed of the train will never change.
If you measure the light like we measure the train, then the length of the boxcar will never change.

What are your thoughts on post #141?

I think that if you look carefully you'll see that you aren't comparing the same thing. x₂ also represents where you are, but that isn't apparent in your equation. If you are moving, x₂ will be different, and so will t₂, for the car example.

 

[russ_watters]

But why aren't there similar or greater volumes of attacks on QFT/QM? That's surely far weirder (is that a word?). Maybe it has something to do with AE vs a big mob (Heisenberg, Dirac, Pauli, Schrödinger, Bohr, ...)?

I agree that they are weirder (yes, that's a word), but most people never learn that those things are weird. The double-slit experiment doesn't become weird until you quantize light and you don't really start digging into that in high school physics. They say there is a wave-particle duality in high school and they explore the wave and particle properties, but they don't mix them - they don't address (or even make you aware of) the contradictions that arise from them.

I first read "A Brief History of Time" in high school and that was my first real exposure to non-Newtonian physics. Its mostly Relativity, but it touches on QM. I didn't dig any deeper into QM though, until much later (though I picked up bits and piece here and there).

Then again, it may just be that Einstein was a cult-of-personality like no other scientist before or since.

 

[Nereid]

Being one of them myself formerly, I guess, quantum theory talks about small intangible things and people can't think of counter examples for them. Not so when you talk about trains, lightenings, twins..

Cats? Surely people can relate to the angst of Erwin's moggie?

 

[swansont]

It was actually Mrs. Schroedinger's cat.

 

[grounded]

I think that if you look carefully you'll see that you aren't comparing the same thing. x₂ also represents where you are, but that isn't apparent in your equation.

x₂=Location of car on x-axis at time t₂

t₂=Time of detection

x₂ is where you and the car will be at t₂ (you are the detector, you detect it when you run into it)

If you are moving, x₂ will be different, and so will t₂, for the car example.

x₂ and t₂ is simply the place and time you run into (or detect) the car. If you are moving towards the car, then the distance the car has to travel before hitting you is decreased since you are closer to it, and since the distance is decreased so is the amount of time it takes the car to travel that distance. 60 MPH is the same thing as 30 Miles Per 1/2 Hour.

If you are traveling away from the car, the car will have to travel a further distance from x₁ to run into you (x₂ - x₁). Since it travels a further distance, it will take more time to run into you (t₂ - t₁). The relative speed never changes.

Is that how you see it?

Post #141

 

[David]

I don't know if he changed his mind, maybe while developing the theory? I don't know. But please see:

http://www.bartleby.com/173/10.html

"Thus the length of the train as measured from the embankment may be different from that obtained by measuring in the train itself"

Isn't this book dated 1920?

Yes, you’re right. The problem is, he lied in some of his books and papers. He flip-flopped many times on many issues, saying one thing in one paper and the opposite in a different paper. The book you are talking about was published in Germany in 1916, and many German physicists were mad at him because of his lying and deceptions.

I’ve been investigating this for years, and I’ve got a lot of his early papers that not too many people know about.

He got many of the ideas for his SR theory from the 1895 Lorentz electrodynamics theory. It was Lorentz who invented time dilation, length contraction, the speed limit of c, mass increase with motion, the relativistic Doppler effect, and the Lorentz transformation equations.

Here is a list of a few things he said in different books and papers:

Einstein first said in 1905 that “light is always propagated in empty space with a definite velocity c”.

Then in 1911 and his 1916 paper he said that light speed was not constant because it slowed down in a gravity field.

In his 1916 book he said it was constant (in the first few chapters), then in a later chapter he said it wasn’t constant.

In 1916 he said all galaxies and stars were “fixed”, then in a 1932 paper he said the galaxies were moving radially at high speeds.

He said in 1916 the universe was not expanding, then in 1932 he said it was.

In 1916 he said large-scale universal space was “curved”, but in 1932 he said it wasn’t.

In 1916 he said that a “cosmological constant” kept all the stars from collapsing in on themselves, then in 1932 he said there was no such thing as a cosmological constant.

In 1905 he said that only one of two relatively moving clocks could slow down due to the relative motion, but in 1918 he said that both of two relatively moving clocks would slow down due to the relative motion.

In 1905 he said there was “no ether”, but in 1918 and 1920 he said there was an “ether.”

In 1905 he said that relative motion caused geometric “length contraction”, then in 1907 he said that relative motion could NOT cause geometric length contraction. Then in 1916 he again said that it could cause length contraction.

For several years he told newspaper reporters that he invented the special relativity theory, but in 1920 he told a New York Times reporter that he and Lorentz invented it.

In 1905 he had “balance-wheel” clocks slowing down due only to “relative motion”, but in 1918 he had to use atomic clocks, acceleration effects, and gravity fields to try to “resolve” his 1905 clock paradox.

In 1905 he said that both the K and K’ systems in his SR theory were non-accelerating Galilean inertial systems, but in 1918 he said that the K’ system in the SR theory was NOT a Galilean inertial system and was accelerated.

In 1916 he said that the SR theory did NOT consider gravitational fields, but in 1918 he said that the SR theory DID consider gravitational fields.

Newton, not Einstein was the first to propose that light would bend when it passed the sun and other bodies. He said this in the 1704 edition of his “Optics”.

Newton, not Einstein or Hubble was the first to propose the fundamental “big bang” hypothesis. He called it a “projectile force” or “projectile impulse” that set all the astronomical bodies flying apart. He said this in some of his letters to Bentley.

Einstein's cult of followers are trying to cover up his errors and lies. That’s why I am banned from posting anything on the relativity sections on this board.

 

[David]

David,

It is a well known fact that AE tried various models before arriving to what we now know as GR, aknowledged and understood both by biographers, like Abraham Pais, and by those who study the origins of relativity, like John D. Norton. It is not new (or any kind of "big secret") that there were contradictions in his papers from that period. You are precisely choosing papers from before 1916, which is roughly when he arrived to the theory's final form.

Your moderator Russ claims the "constancy" postulate is still in effect.

 

[David]

David,

If you are going to put so much weight on AE own words, why don't you at least use the version that he regarded as the best way to put things together? otherwise, you seem to be trying to advocate for the ideas that AE, and many others now, understood to be faulty.

Then why can’t this be discussed on this board’s SR pages? The management says we can’t post anything that challenges the validity of the 1905 paper. I got banned from those pages because I proved that Einstein changed his mind and corrected some of the errors of the SR theory, but management here is pretending there are no errors in SR and that Einstein never made any changes in it.

The Einstein cult that runs the board doesn’t want anyone to quote any later papers in which Einstein changed his mind about things he said in the SR theory. These guys are essentially carrying out a hoax, pretending that there are no flaws in SR theory and that Einstein never made any changes in it.

This is part of the political promotion of Einstein as the “world’s smartest man”. It’s a hero-worship cult. I run into this on other message boards too.

 

[wespe]

Yes, you’re right. The problem is, he lied in some of his books and papers. He flip-flopped many times on many issues, saying one thing in one paper and the opposite in a different paper. The book you are talking about was published in Germany in 1916, and many German physicists were mad at him because of his lying and deceptions.

I’ve been investigating this for years, and I’ve got a lot of his early papers that not too many people know about.

Well, okay, let's say he took ideas from other people and he changed his mind a few times, etc. But it would be wrong to say his contribution was null. I think he was the only one to combine all the ideas and dismiss aeather. Also he got nobel prize for explaining photoelectriic effect. I may be wrong in these. Anyway, that's history. The important thing is that there is currently a standard theory. There may be textbooks with erros, even professors may disagree with each other. It's not like a holy book you know. In the end it is the experiments that decide what is right and what is wrong. Therefore, in my opinion, your attacks on a dead man is not too beneficial.

[
sorry if I sound cocky.
regards.
]

 

[David]

Well, okay, let's say he took ideas from other people and he changed his mind a few times, etc. But it would be wrong to say his contribution was null. I think he was the only one to combine all the ideas and dismiss aeather. Also he got nobel prize for explaining photoelectriic effect. I may be wrong in these. Anyway, that's history. The important thing is that there is currently a standard theory. There may be textbooks with erros, even professors may disagree with each other. It's not like a holy book you know. In the end it is the experiments that decide what is right and what is wrong. Therefore, in my opinion, your attacks on a dead man is not too beneficial.

[
sorry if I sound cocky.
regards.
]

You don't sound cocky at all.

Of course his contributions were not “null”.

In my opinion his best work was in early atomic physics. His early atomic papers are absolutely brilliant. This is actually what he was famous for in the physics community and why he received the Nobel Prize. I don’t have any problem with that. He was quite smart about atomic physics.

What I have a problem with is all the Einstein-worship websites and books that say there are no flaws in SR theory, and so many cultists on the internet teaching teenagers the wrong physics information based on SR theory.

There is no current “standard theory” because it keeps changing. For example, just 10 years ago universities taught that the most distant galaxies were not moving at faster than the speed of light relative to the earth, but now many of the universities are teaching that they do move faster than light relative to the earth.

A type of “ether” theory has been re-introduced to astronomy with “co-moving local space” acting as a “local ether”.

It is not good in any science field when someone is banned from science forum topics because they point out that the SR theory contains errors and that Einstein himself corrected some of the errors.

This is not “science”, this is a “science cult”. The quest is not for “truth” or “knowledge”, but to promote the Holy Worshipped One. This is pseudo science masquerading as mainstream science.

My “attacks” are not on the dead man. If he were alive today he would be astounded at the amount of false information being spread on the internet in his name. He would be outraged.

He didn’t have the benefit of certain astronomical information we have today, so he had to guess about a lot of stuff a hundred years ago. He thought the universe was not “expanding” because virtually all the astronomers in the 1916 era said it wasn’t expanding. If he were alive today there would be plenty of things he would clear up about his early time and motion papers, because at last he would have the necessary observational information to make some final decisions. He flip-flopped on some issues a hundred years ago, but so did other physicists. But for Einstein cultists today to claim that he was always perfect, never flip-flopped, never fibbed or fudged, then that is just gross “hero worship”, which has no place in physics or science. It’s like Elvis worship. But Elvis worship does not belong in science.

 

[Hurkyl]

Gasp, Einstein didn't come out of the womb already knowing the form of GR and SR we use today? My entire worldview has been shattered.


If I may hazard a guess, the reason you are banned from the relativity forums because your topic is Einstein, not relativity. Worse, you have this nasty habit of hijacking threads to start this discussion, instead of giving it its own thread.

 

[swansont]

x₂=Location of car on x-axis at time t₂

t₂=Time of detection

x₂ is where you and the car will be at t₂ (you are the detector, you detect it when you run into it)

OK, thanks for clarifying. I wasn't sure you were actually measuring the car by collision - now I am.

x₂ and t₂ is simply the place and time you run into (or detect) the car. If you are moving towards the car, then the distance the car has to travel before hitting you is decreased since you are closer to it, and since the distance is decreased so is the amount of time it takes the car to travel that distance. 60 MPH is the same thing as 30 Miles Per 1/2 Hour.

If you are traveling away from the car, the car will have to travel a further distance from x₁ to run into you (x₂ - x₁). Since it travels a further distance, it will take more time to run into you (t₂ - t₁). The relative speed never changes.

Is that how you see it?

Post #141

I think I understand your point. But x₂ is where I am, so it's actually fixed in my coordinate system. If you want to look at it from another point of view, you have to properly transform everything.