# Light Speed, Are We Talking Relativity?

Light speed relativity

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### #18 Mattzy

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Posted 30 May 2019 - 03:04 AM

You're in a sealed train. You can't tell if you're moving or not. At the other end of the train, a light goes on and reaches you at a velocity c = length of train/time it takes to cross the train. Since light's propagation velocity is independent of the train's velocity (light's propagation velocity is relative to its medium), the light will always have that train's length to cross in the same time. But let's say you have two light detectors at your end, one outside the train and the other inside. You have two sources of light, outside and inside,  that go on together when they're side by side. If the train is moving toward the light you'd expect the outside light to hit the outside detector first because the train's motion has shortened the distance the light has to travel compared to the inside light which always has to traverse the full length of the train. Remember, the train's motion does not affect the speed of light inside the train or the distance that light has to traverse. The problem is the MMX proved that the light outside the moving train hits the end simultaneously on the outside as the inside light  does. This makes no sense from a standard definition of relative velocity. The train's velocity has no effect on the light speed and the light is traversing two different distances in the same time. So Einstein copied Lorentz and said the train must contractinside to match its length outside. Of course this is nonsense. What is happening is the time inside the train is slowed relative to the time outside the train allowing the light more time to cover the greater distance so it can arrive simultaneously with the light covering the shorter distance  outside the train. I hope you can see how wrong Enistein was in his crazy assumption about how the length of the train inside contracted while the outside remained the same.

Now relativists will lie to you and say light travels as a photon and not a wave. The photon as bullet would be affected by the movement of the train. It's not because a wave propagates at a velocity relative to its medium. But since light's medium is electromagnetic and not material (it's a vacuum) The vacuum inside the sealed train can't be pushed relatively to the vacuum outside the train. If the medium can't be moved, and the relative velocity of the light to the medium can't be changed, then the relative velocity of the light to the train can't be changed by the train's movement. The MMX verified the earth registers no velocity relative to light's medium whatever its nature.

Yes ralfcis, thanks as always for the great  discussion on this leads to more and more questions without perfect answers. At the time of the MMX there was more adherence to the idea of aether - I read that the Lorentz invariances were better proof of isotropics. Victoremedvil was talking earlier about dark energy (I haven't heard much about anti matter recently) Others can talk about all that but I'm going to have to simply accept the isotropic nature of light and read your relativity algebra to see if that helps.

I have also been wondering if redshift only applies to universal expansion measurements and not to a local experiment- but that is another topic.

Talking of vacuums and ether, I have been wondering about transparency and how light travels through glass - but not less dense materials such as cardboard. It is thought to slow down as it passes through!! - and of course speeds up as it passes back outside - so much for isotropics! Maybe space is an ether and glass too!

Question: (I may post this one too to see what comes back)

If two flash light beams are shone towards each other from opposite walls of a room, the photons will pass each other going in opposite directions. An observer standing next to the beams at the centre of the room would measure photon speed in both directions at light speed at the same time. What would be the relative speed of said photons?

### #19 exchemist

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Posted 30 May 2019 - 03:11 AM

exchemist, yes I'm sure you're right on the money there. I noted your post 3 at the time. Getting a grasp of it is going to be fun. falfcis has something to say too!

Victor

exchemist, yes I think you are right on the money there, and I have noted your post 3 (I sometimes forget who said what while I'm replying though). Clearly that is what I'm going to have to struggle with.

Victormedvil talked of the redshift in measuring universal expansion and the theory of dark energy, that makes me wonder if redshift is only a phenomena in universal expansion. Maybe redshift doesn't occur in local movements or experiments (or across a solar system at right angles to universal expansion) if so, I suppose that would support the dark energy theory. I must check that out!

No it's universal. You always have the Doppler effect, which applies to any wave, but modified to take account of the special property of light that it requires no medium and has this speed independent of motion of source and receiver.

The Wiki article on the relativistic version is here: https://en.wikipedia..._Doppler_effect. It involves this β term, which you do not get in the regular non-relativistic version for waves (sound, water etc) that have a speed defined relative to the medium in which they occur.

The regular version is here: https://en.wikipedia.../Doppler_effect

The cosmological red shift is not a Doppler shift, though, as it is due to the expansion of the metric rather than relative motion between source and receiver.

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### #20 ralfcis

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Posted 30 May 2019 - 06:21 AM

What would be the relative speed of said photons?

See the waves an relative velocity thread. You mean what is the relative speed of the photons to each other. It's c due to the relativistic combo law. What is the speed as seen from a 3rd party observer from a perpendicular perspective? It's 2c but this is not a relative velocity vector but a scalar speed.

Also in that thread you will see the existence or not of a medium for light is irrelevant. Here's a nice short  link.

Light's medium is electromagnetic in nature so why did the MMX prove matter can't have a relative velocity to the medium? I said you can't lock the medium up in a bottle and not have the electromagnetic nature of the medium outside the bottle permeate inside the bottle. But a faraday cage can isolate the medium inside the cage from the one outside the cage. So why couldn't you launch a faraday cage and detect a difference in light's velocity inside from outside. The answer isn't in the relative velocity between the inside and outside medium, it's in the relativistic velocity combo law. No relative velocity can exceed c so even if the two mediums are separated from each other, they still can't have a relative velocity to each other because not only do they bump up against the max speed limit of the universe but the cage is material and it can't register a relative velocity to either the inside or outside medium.

You will discover the squawking parrots on here have no ability to reason and can only repeat what is posted in wiki articles so according to those articles light has no medium which is false.

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### #21 exchemist

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Posted 30 May 2019 - 07:19 AM

No it's universal. You always have the Doppler effect, which applies to any wave, but modified to take account of the special property of light that it requires no medium and has this speed independent of motion of source and receiver.

The Wiki article on the relativistic version is here: https://en.wikipedia..._Doppler_effect. It involves this β term, which you do not get in the regular non-relativistic version for waves (sound, water etc) that have a speed defined relative to the medium in which they occur.

The regular version is here: https://en.wikipedia.../Doppler_effect

The cosmological red shift is not a Doppler shift, though, as it is due to the expansion of the metric rather than relative motion between source and receiver.

I see some others are talking about a medium (an aether) for light. There cannot be a medium in the usual sense because of the (observed) independence of its speed from that of source and receiver. But the speed of light, c, does depend on the dielectric permittivity, ε,  and magnetic permeability, μ,  of the vacuum: c =1/√(εμ). So the speed of light depends on what are effectively properties of the vacuum.

The idea that the vacuum has physical properties is somewhat curious, when you stop to think of it. In this sense, and this sense only, the vacuum can perhaps be thought of as a kind of medium for EM radiation.

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### #22 Mattzy

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Posted 30 May 2019 - 07:22 AM

Thanks exchemist and ralfcis. I will now go quiet for a few days while I read your links. I should be well armed when I return! Hopefully with some understanding of the relativistic combo law!

### #23 sluggo

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Posted 30 May 2019 - 11:37 AM

ralf#16;

Duplicating the emitter-detector setup outside makes no difference. The setup is physically attached to the train, thus has the speed of the train. If a clock is located with each detector, both will run slower by a factor of 1/g(amma) compared to one on the platform. The train will also contract by the same factor 1/g. The passenger biological clock will also slow by 1/g, therefore he concludes (x/g)/(t/g)=x/t=c (light speed).
The train is contracted as seen by an outside observer, while the passenger is not aware, and cannot detect it since his ruler is contracted by the same factor!

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### #24 ralfcis

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Posted 30 May 2019 - 12:48 PM

You're not understanding because your brainwashing prevents you from reading what I wrote. The outside emitter is not attached to the train while the inside is. The inside length from the inside perspective is fixed. The outside length from the outside perspective shortens not due to length contraction but simply due to the forward velocity of the train relative to the platform's fixed emitter. There is no relative velocity to the light inside the train because that's a stationary frame but there is relative velocity to the light outside the train. Yes or no.  Relativity then dictates the inside length must length contract so that the inside and outside light simultaneously hit the back of the train. From inside the train, the light hits both front and back simultaneously but from outside (the platform perspective) the front and back are not hit simultaneously. The inside and outside light does hit each end simultaneously even though each end is hit at different times by the inside and outside lights. Every word I write counts towards the meaning I am trying to convey. Do not selectively ignore the words that don't fit your narrative of what you think I'm saying. I am really done with that.

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### #25 sluggo

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Posted 30 May 2019 - 01:50 PM

Maltzy#5;

w=wave length, f=frequency, c= light speed
wf=c,
Photon of one cycle is emitted at the origin.

A converging with the light, absorption time < emission time.
B at rest relative to the source, absorption time = emission time.

C diverging with the light, absorption time > emission time.
Doppler effect depends on relative velocity. There would also be effects of time dilation, but shows the principle effects.

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### #26 Mattzy

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Posted 31 May 2019 - 01:59 AM

I'm liking all of what you have both said. It's of great value to me. I'm going to have to think hard about all of it for a while and study those links. I'm beginning to see light at the end of the tunnel - excuse the pun! I'll be back soon - when the next station stops at this train!

Mattzy.

### #27 sluggo

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Posted 31 May 2019 - 09:46 AM

ralf#12;

photon as bullet would be affected by the movement of the train. It's not because a wave propagates at a velocity relative to its medium.

[A water wave is a composition of water atoms. Consider a light 'wave' a composition of photons. Einstein won a Nobel prize for his paper on the photoelectric effect, based on a discrete packet of em energy, labeled a photon.]

photon as bullet would be affected by the movement of the train. It's not because a wave propagates at a velocity relative to its medium.

[Only things with mass acquire the speed of a composite object with mass. Since light has no rest mass, it does not acquire the speed of the emitter. That's the basis for postulate 2 to include 'light speed is independent of its source]
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### #28 sluggo

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Posted 31 May 2019 - 09:48 AM

ralf#16;

Duplicating the emitter-detector setup outside makes no difference. The setup is physically attached to the train, i.e. an extension of the train. If a clock is located with each detector, both will run slower by a factor of 1/g(amma) compared to one on the platform. The train will also contract by the same factor 1/g. The passenger biological clock will also slow by 1/g, therefore he concludes (x/g)/(t/g)=x/t=c (light speed).
The train is contracted as seen by an outside observer, while the passenger is not aware, and cannot detect it since his ruler is contracted by the same factor!
The moving observer has the option of assuming a rest frame, as you said, he can't detect his motion.

### #29 VictorMedvil

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Posted 31 May 2019 - 02:07 PM

exchemist, yes I'm sure you're right on the money there. I noted your post 3 at the time. Getting a grasp of it is going to be fun. falfcis has something to say too!

Victor

exchemist, yes I think you are right on the money there, and I have noted your post 3 (I sometimes forget who said what while I'm replying though). Clearly that is what I'm going to have to struggle with.

Victormedvil talked of the redshift in measuring universal expansion and the theory of dark energy, that makes me wonder if redshift is only a phenomena in universal expansion. Maybe redshift doesn't occur in local movements or experiments (or across a solar system at right angles to universal expansion) if so, I suppose that would support the dark energy theory. I must check that out!

Redshift happens in local movement too with the doppler effect like exchemist applies but also it happens with Dark Energy and Gravitational fields too. You can have Black holes that redshift, Universe Expansion that redshift, and the Doppler Effect that redshifts. There is not just one phenomenon that causes it. Redshift due to doppler effect is local and caused by the source object's movement, while Dark Energy happen universally as space is moved through that is expanding, Gravitational is local and universal as every object redshifts or blueshifts the object but the intensity is based on their local field strength and the amount of lorentz contraction of the space universally. So, needless to say it is a complex system to pin down to a sentences, words, and equations, but here is a rule of thumb if the object releasing a wave is moving or space is compressed/expanded it will redshift or blueshift the wave the amount of movement or warping of space will show the intensity of the redshift/blueshift. This is all covered in Special and General Relativity along with Quantum Mechanics and Quantum Field Theory being subject to all the 4 theories of modern physics.

Dark Energy (Expansion) Redshift equation.

Doppler Redshift(Movement/Acceleration) and Gravitational(Contraction) Redshift Equations.

Edited by VictorMedvil, 31 May 2019 - 02:37 PM.

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### #30 ralfcis

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Posted 31 May 2019 - 02:27 PM

OK sluggo I'll decouple the outside detector from the train onto the platform such that it receives the outside emitter's light at the same point on the platform as  it hits the outside back of the train simultaneously from the platform's perspective. To you this must semantically and dogmatically mean a world of difference but it makes no difference to the point I'm making. The clock is not the detector just like the back of the train is not the clock, it is a detector. One clock is from the platform's perspective of what time the outside light hits the back of the train and the other clock is from the train's perspective of what time the inside light hits the inside back of the train which is in the same spot as the outside back of the train. Why do I need to go down to this level of explantion? Are you now going to slink away and just repeat your last post ignoring any of this dialogue? I could go back and tear apart every point you've made but it's a huge waste of time for me if you can't acknowledge whether you agree or disagree and just parrot your dogma instead.

Edited by ralfcis, 31 May 2019 - 02:36 PM.

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### #31 Mattzy

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Posted 01 June 2019 - 08:59 PM

I was intrigued by sluggo's inclusion of the passengers biological clock. I read that indeed Einstein said absolutely everything is effected. That brings another question to my simple mind.

Regarding the slowing of the passengers' electro chemistry (proportional to relative speed) - (I like this because he doesn't have to use his eyes as detectors to look at a clock). Let sluggo stay with his view of the passenger in relation to the station platform, ralfcis does a calculation for said passenger in relativity with another train traveling in the opposite direction and exchemist does a calculation for some other moving object (say) an aircraft.  So we have three different perspectives.  Do we now have three different results for the same passenger? If the biological clock (or his watch if you like) is proven to slow down or speed up by the same measure in each calculation then have we proved the theory?  If the results are different then have we disproved the theory? What is the reality for the passenger? He can only experience one reality.

### #32 ralfcis

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Posted 02 June 2019 - 09:03 AM

Everyone experiences time pass for themselves at the same universal normal rate of time. Even if relative motion makes it appear the one they're observing is going through time at a different rate, it's only an illusion of perspective, time still passes for both at the same normal rate with only 2 exceptions. If you're at a different gravitational potential or change your velocity relative to someone else, you will be going at a different rate of time (undetectable to you) at the DSR rate during the time it takes for the news of your change to reach the observer. These are the facts and relativity can't disprove them. Relativity has a different interpretation of these facts but my math will arrive at the same results as relativity's math except that

1. Relativity's math is far more complex with a lot of arbitrary spacetime path rules to follow.

2. My math applies to all changes of velocity not just the ones that end in re-unification of the two parties. Hence there is a possiblity of experimentally falsifying relativity's math as being incomplete.

Yes there is only one reality. Einstein almost understood what that was but he fell short and declared all perspectives were equally real. However, he did acknowledge one was more equal than others: co-location. Even though two parties can have a non-zero relative velocity as they whizz past each other, for a split second, at their closest, they are co-located in a present that is independent of anyone's perspective. What he didn't realise is the instantaneous present reality that supercedes all perspective realities does not depend on co-location. Causal time joins all proper times of all frames into a universal single present reality that we can only experience during co-location but can be calculated otherwise.

So could the greatest scientific minds of all time have been totally wrong for the last 114 years? I'm sure a similar question applied when Aristotle was being overturned and the answer is yes because the evidence stands on its own even if no one wants to look at it.

Edited by ralfcis, 02 June 2019 - 09:34 AM.

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### #33 Mattzy

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Posted 03 June 2019 - 12:12 AM

ralf#12;

[A water wave is a composition of water atoms. Consider a light 'wave' a composition of photons. Einstein won a Nobel prize for his paper on the photoelectric effect, based on a discrete packet of em energy, labeled a photon.]

[Only things with mass acquire the speed of a composite object with mass. Since light has no rest mass, it does not acquire the speed of the emitter. That's the basis for postulate 2 to include 'light speed is independent of its source]

I was going to ask about this very subject while I'm still going with relativity. Re. goldilocks frequencies. I want to know about the relationship between the transmission frequency of (say) a microwave oven and the frequency of the packets (or parcels or bullets or photons - whatever). As I understand it the wavelength of a microwave photon is around 2.4 inches. This is why it won't penetrate a 1mm hole in the screen we look through. But the waves of zillions of photons are being transmitted at a much lower frequency. When telecom techs talk about the goldilocks frequencies, I think they are referring to transmission frequencies that penetrate building materials - not the frequencies of the photons themselves. So radio transmitters may send waves of photons many metres apart, but the photons carry their own frequency. Is the photon frequency relative to the power at the antenna / magnetron? Are the two frequencies somehow relative?

### #34 Mattzy

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Posted 03 June 2019 - 12:57 AM

Everyone experiences time pass for themselves at the same universal normal rate of time. Even if relative motion makes it appear the one they're observing is going through time at a different rate, it's only an illusion of perspective, time still passes for both at the same normal rate with only 2 exceptions. If you're at a different gravitational potential or change your velocity relative to someone else, you will be going at a different rate of time (undetectable to you) at the DSR rate during the time it takes for the news of your change to reach the observer. These are the facts and relativity can't disprove them. Relativity has a different interpretation of these facts but my math will arrive at the same results as relativity's math except that

1. Relativity's math is far more complex with a lot of arbitrary spacetime path rules to follow.

2. My math applies to all changes of velocity not just the ones that end in re-unification of the two parties. Hence there is a possiblity of experimentally falsifying relativity's math as being incomplete.

Yes there is only one reality. Einstein almost understood what that was but he fell short and declared all perspectives were equally real. However, he did acknowledge one was more equal than others: co-location. Even though two parties can have a non-zero relative velocity as they whizz past each other, for a split second, at their closest, they are co-located in a present that is independent of anyone's perspective. What he didn't realise is the instantaneous present reality that supercedes all perspective realities does not depend on co-location. Causal time joins all proper times of all frames into a universal single present reality that we can only experience during co-location but can be calculated otherwise.

So could the greatest scientific minds of all time have been totally wrong for the last 114 years? I'm sure a similar question applied when Aristotle was being overturned and the answer is yes because the evidence stands on its own even if no one wants to look at it.

Fantastic answer ralfcis! I doubt that I'll do better than that. I had been thinking - as I think you are saying - that we are explaining and measuring the illusion of perspectives - so I wonder the study of relativity it will ever have any practical use - I stand to be corrected. When we start talking of double special relativity I am reminded that Steven Hawking said that increasing complexity in a theory is a bad sign for it! Not that he was the first of course.

The concept of "the normal rate of time" is something else on which I shall have to do some reading. I have often wondered about that too. And I want to post a question on the use of timelines. I think your very concise answer on photons moving in opposite directions being measured as 2c on on a scalar measurement and c on a relativistic measurement was very close to the nub of the issue. I know what Aristotle would have asked - "why?" (only joking, all your answers have been great, thanks again ralfcis).