Why is the Speed of Light Constant in All Inertial Frames?

[David]

Originally posted by chroot
Seems we're all on the same page, it's just a matter of wording

The way you state it is good, but I think you need to add the atomic clock to your statement, and I think you need to be specific about the photons being at the clock at the time of measurement. We need to get rid of the old misconception that “the speed of light is always constant everywhere”, since that is not accurate and it is very misleading. Even if we change it to, “the speed of light is constant and is always measured by all observers, everywhere, to be c,” this is misleading too. I know it’s misleading because I see all different kinds of versions of that statement on the internet, and when I tell people that light photons slow down when they pass near a massive body, they argue with me and say that photons never slow down under any circumstances, which is incorrect.

When I try to explain to people the new Davis-Lineweaver way of thinking about photons reaching us from a distant high-z galaxy by gradually speeding up, relative to the earth, as they travel through deep space, a lot of people deny that, because they’ve been erroneously taught in high school and at universities that “the speed of light is constant everywhere”. When I ask them what they think about the Davis-Lineweaver paper, they go, “doh?” I asked a young guy who has a new PhD in astronomy what he thought of the Davis-Lineweaver paper and he went, “doh?” too. It’s a shame that our universities are so far behind in teaching this stuff correctly.

 

[David]

Originally posted by chroot
Seems we're all on the same page, it's just a matter of wording

Ok, let me ask you this. What do you think of this statement:

“According to General Relativity, the wavelength of light (or any other form of electromagnetic radiation) passing through a gravitational field will be shifted towards redder regions of the spectrum. To understand this gravitational redshift, think of a baseball hit high into the air, slowing as it climbs. Einstein's theory says that as a photon fights its way out of a gravitational field, it loses energy and its color reddens. Gravitational redshifts have been observed in diverse settings.”

http://216.239.57.104/search?q=cach...ent+light+speed+redshift+tower&hl=en&ie=UTF-8

 

[StarThrower]

David, a few questions if you don't mind.

A photon of mass m is moving through a gravitational field, caused by a star of mass M. Let the force on m exerted by M be given by:


F = GMm/r^2

Where r is the distance from the center of mass of the star, to the photon. Let us presume that the mass of the star is just right, to cause this photon to travel around the star in a perfect circle. Please calculate the tangential speed of the photon. Presume the star is at rest in an inertial coordinate system.

 

[yogi]

David - my person feeling is that the speed of light is affected by gravitational fields - as you know or course, the traditional relativity interpretations relate the gravitation red shift to a change in photon frequency due to the energy associated with the gravitational potential - rather than a change in velocity - I am also convinced that the velocity of light has varied temporally - starting out at what could be said to approach infinity as time is wound backward - some years ago I derived some equations that showed the velocity of light is determined by the rate of expansion rather than vice versa - these same derivations also suggested that the expansion rate was variable (approaching infinity as t approached zero). If the new observations survive scrutiny - it will be most gratifying personally. The operative word here is "IF."

 

[russ_watters]

Originally posted by chroot
Seems we're all on the same page, it's just a matter of wording.

I'm not so sure, since he's using that as the basis of an argument that C isn't constant.

“Time” depends on how fast things move, vibrate, or oscillate, when compared to the motion, vibration, or oscillation rate of something else. Time is a kinetic energy/motion phenomenon, and different kinds of “clocks” speed up and slow down at different rates in the same places and under the same conditions. Anything that moves, vibrates, oscillates, or hums is a “clock”. An atomic clock doesn't represent all of "time". It only represents internally vibrating atom rates.

According to SR, time itslf is a varible. You are indeed correct that different types of clocks are affected differently by their environment. However, every clock is also affected in exactly the way Einstein predicts in SR/GR - because time itself is variable.

Ok, let me ask you this. What do you think of this statement:

...baseball hit high into the air, slowing as it climbs.

Thats fine as long as you realize its not an exact analogy. A photon doesn't slow down as it leaves a gravitational field. Both the baseball and the photon lose energy, but that is manifest in different ways.

Russ’ less specific statement could include “local” observers observing the motion of distant photons moving from one distant place to another.

No. This is sora a catch-22, since you can't "observe the motion of distant photons."

Because a local observer at the Earth will measure a slowdown in the speed of light as it passes near the sun...

How exactly would you do that? Again, catch-22.

 

[David]

Originally posted by yogi
David - my person feeling is that the speed of light is affected by gravitational fields - as you know or course, the traditional relativity interpretations relate the gravitation red shift to a change in photon frequency due to the energy associated with the gravitational potential - rather than a change in velocity -

Seems to me that Einstein said the light is emitted at a lower frequency because the harmonic oscillation rate of an atom slows down in a stronger gravitational field, thus atomic clocks “tick” more slowly in a stronger gravitational field. That's basically what the atomic clock guys at Boulder told me.

When did this idea that “light “struggles” to “climb out” of a gravitational field and “loses” some of its frequencies” begin to enter physics?? Einstein specifically said the light does not change frequencies after it is emitted.

 

[David]

Originally posted by russ_watters
I'm not so sure, since he's using that as the basis of an argument that C isn't constant. According to SR, time itslf is a varible. You are indeed correct that different types of clocks are affected differently by their environment. However, every clock is also affected in exactly the way Einstein predicts in SR/GR - because time itself is variable.

“Time itself” is based on things oscillating, vibrating, and moving. There is no “time” without motion.

How are you defining “time itself”?

Have you ever found a pendulum clock to slow down in a higher gravitational potential just as atomic clocks do and at the same rate? Pendulum clocks actually speed up in a higher gravitational potential.

Why did he say in 1911 that we couldn’t use atomic clocks in part of his thought experiment, because we had to use different kinds of clocks that weren’t affected by gravitational potential??

Originally posted by russ_watters
Thats fine as long as you realize its not an exact analogy. A photon doesn't slow down as it leaves a gravitational field. Both the baseball and the photon lose energy, but that is manifest in different ways. No. This is sora a catch-22, since you can't "observe the motion of distant photons." How exactly would you do that? Again, catch-22.

A photon loses frequencies? But Einstein said they don’t. He didn’t say they slow down when the leave a gravitational field, he said they speed up. The “baseball analogy” isn’t anywhere close to the correct analogy. That analogy implies that black holes are filled with bright white light that “struggles” to get out and then just gives up and turn around and go back to the center of the black hole.

Originally posted by russ_watters
This is sora a catch-22, since you can't "observe the motion of distant photons." How exactly would you do that? Again, catch-22.

Sure we can. When we see photons that have passed near the sun, we “observe” that the photons slowed down and changed directions when they went past the sun at close range.

 

[yogi]

David - As to Gravitational red shift - there are two common approaches to the red shift - one is that the photon frequency is lowered as it climbs out of the gravitational field - there are many books that take this approach - but there is also the view that the wavelenght is modified at the out set by the gravitational field - and that the photon frequency does not change - so I would imagine all that is left is the photon velocity that can slow - However, an example of the apparent frequency of the photon changing can be found in the cosmological red shift due to spatial expansion - as space stretches, we observe the Hubble red shift ... an effective change in the photon wavelength due to spatial distension during the period from emission to reception.

 

[David]

Originally posted by yogi
David - As to Gravitational red shift - there are two common approaches to the red shift - one is that the photon frequency is lowered as it climbs out of the gravitational field - there are many books that take this approach - but there is also the view that the wavelenght is modified at the out set by the gravitational field - and that the photon frequency does not change - so I would imagine all that is left is the photon velocity that can slow - However, an example of the apparent frequency of the photon changing can be found in the cosmological red shift due to spatial expansion - as space stretches, we observe the Hubble red shift ... an effective change in the photon wavelength due to spatial distension during the period from emission to reception.

Thanks for the info. I think some of this stuff is pretty silly. I don’t know who invented the “space is expanding” idea. Einstein attributed it to Friedman. How can space “expand”? That’s ridiculous. Space is three-dimensional “nothing”, filled with moving bodies and their fields. Distance is expanding because the galaxies are moving through space away from one another. When you drive away from New York, you don’t say that “space is expanding” between you and New York. I think it’s nonsense to say that space is expanding. Funny how it expands only between the galaxies but not within them. Funny how M-31 is coming toward us but they don’t say that the space in between us and M-31 is “shrinking”.

One persistent problem they’ve had for years is trying to hold on to Einstein’s “constancy of the speed of light postulate” when it really doesn’t apply to nature. The authors of all the latest physics papers feel that they have to always agree with Einstein and pretend he never made any mistakes in the SR theory. They also have to pretend there is no “light propagating medium”, because “Einstein said so.” Modern cosmology is warping and distorting its theories while trying to explain observational results but without ever admitting Einstein made errors in his SR theory.

 

[chroot]

Looks like this thread is heading to theory development...

- Warren

 

[David]

Yogi,

Look at the Harvard Tower experiment. Radiation emitted at ground level was of a lower frequency than radiation emitted at the top of the tower. Just what Einstein said in 1911, and I believe that theory was correct. But people try to explain it as light being emitted at a normal rate, then the light “struggles” to climb out of the gravity well. While it struggles, it somehow loses frequencies. The atoms are supposed to emit more frequencies at the bottom of the tower than were received at the top of the tower. So where do those lost frequencies go? If we consider them to be waves, then where do the lost waves go? No, the better explanation is that the atoms emit light of a lower frequency from the beginning. And also, the light starts out slightly slower at the bottom and speeds up a little as it leaves the stronger area of the gravitational field. But that speed change wouldn't cause a redshift at the receiver. It would only cause a slight delay in the initial light reception time at the top of the tower.

The speed change is why light slows down when it passes the sun. It doesn’t “lose” frequencies at the sun and then “gain them back” when it gets away from the sun. The light just slows down as it passes the sun. We seen only bending of the light at the earth. We don’t see a redshift of the light.

What a lot of physicists don’t seem to want to admit that it is not “empty expanding space” that regulates the speed of light, but evidently it’s the fields in the space that do it, and they, in effect, are the local “ethers” of space... the fields. In my opinion.

 

[yogi]

David - Roberson was the first to suggest spatial expansion as the cause of the red shift (Robertson of the Robertson/Walker metric). Almost every cosmologist takes the view that the galaxies are not traveling with respect to space - but with it. There are some profound reasons for that view.

There are many so called accepted truths that are copied and endorsed in the physics community that need to be overhauled in the light of new discoveries. - - But in many cases there will be conflicting data and inconsistent interpretations - For example, I do not believe the issue of light velocity can be settled for or against SR based upon our present knowledge - just as in Einstein's 1911 paper to which you have referred - there were errors (Einstein had incorrectly determined the deflection angle of light by the Sun) - It is great to advance new ideas, but beware of rashness - its been my experience that when someone is absolutely sure they are right - they are usually wrong.

 

[David]

Originally posted by yogi
David - Roberson was the first to suggest spatial expansion as the cause of the red shift (Robertson of the Robertson/Walker metric).

Just plain motion through space can cause both the redshifts and blueshifts. Doppler predicted this with starlight in 1832. This is a common phenomenon within our own galaxy, and it has been understood for the past 171 years. Some of these modern ideas are going against common sense and observation because they are very insistent on not using an “ether” theory. There is no observational evidence that “space is expanding”. It is “distance” that is expanding, and that causes “gravitational fields in the space between the galaxies to thin out” as the galaxies separate in deep space. The gravitational field potentials apparently serve as an “ether”, which regulate the local speed of light. People can call this “space”, but it’s not “empty space”, it’s space filled with local field potentials

 

[yogi]

The cosmological red shift due to expansion and the redshift (or blue shift) due to the local motion of the galaxies (called the peculiar motion by cosmologists) are two different phenomena. M31 is blue shifted - it is a member of the local group - and it is not far enough away to be predominately governed by Hubbles law (exhibit a greater expansion redshift that the blue shift that is consequent to its motion due to gravitational forces between it and the other members of the local group including our own Milky Way)- we say that such entities are gravitational bound - like the distance between the Earth and the moon - this doesn't negate conventional wisdom. The galaxies at greater distances - like those in the Virgo cluster - all exhibit red shifts. Bodies with large masses will require a greater separation distance before the influence of expansion swamps out the affects of gravitational attraction.

 

[1100f]

Originally posted by Kannan Kailas
Thanks for the replies,

But if we say E=hu, or F=GMm/r2 ,the constants here is not making any kind of nonsense to us.

But the consistancy of the velocity of light is TRUE, but still it remains to be a nonsense.

Why is it a nonsense?

 

[1100f]

Originally posted by TheAtheistKing
the following:
Now, suppose that initially he was moving away at a speed of 29979458 meters per second from the emitting body. Common sense tells you that the photon should never reach him, that the distance between him and the photon should remain constant. Again relativity says that not only will the photon pass him, but it will pass him at a speed of 299792458 meters per second, simply because he is in an inertial reference frame.

The above conclusions show why the assumption that the speed of light is the same in ALL inertial reference frames is nonsensical.

If you want to find flaws in the theory of relativity, please use what relativity says, not what your "common sense" says. Relativity says that you cannot suppose that initially he was moving away at a speed of 29979458 meters per second from the emitting body. So pleas don't start with that assumption to find flaws in SR.