# Why is the speed of light independent of a frame of reference?

Try and see it from the photon's point of view:
Its entire mass is dependent on it's velocity.
If it had a different relative speed, it would also have a different mass, and masses can't really change or appear/diappear.
Thus the speed HAS to C, in order to maintain it's mass.
Then forget about the space reference or third party point of view, because he and space CAN observe two particles meeting each other at the speed of C+C=2C.

Thus remains only the contradiction between the photon receiving parties's measurements, and the third party observers observation (which can only be an observation and not a direct measurement).

I think it's easier to see the difference this way.

/Best regard

Henrik

I understand the Michelson–Morley experiment and its result; but what I don't know yet is the REASON.
Example:
A torch in free space is moving at a velocity [v] w.r.t me. Considering the material nature of light, shouldn't the speed of photons emitted from the torch be [v+c] w.r.t ME?
According to the experiment, it's not so.
I'm wondering about that one too. You could assume that it a direct result of SpaceTime existing, maybe? That anything 'existing' needs a metronome, and the best metronome we have is light. The arrow of time we refer to macroscopically 'ticks', to me that is, with the speed of light :) Plank time is often said to be the limit for any observations that makes physically sense to us, and the way we defined it, or Plank defined it, is that one Plank time is the time it takes for light to travel in a vacuum, one distance of Planck length.

It seems as a natural choice for the arrow to me. If it is so then it follows that for this to work over a whole SpaceTime you will need light to behave exactly as it does. Giving you the same 'speed' locally in all 'frames' possible. That means that although you will find other frames of reference change relative you (mass, energy, gravity), the 'frame' you define by existing, never change intrinsically. Meaning that if you had a life defined in yards, and we agreed on it being ten yards, you would nowhere find those yards to 'change', measuring it by your own yardstick.

Often the idea of 'clocks' is used to describe different 'frames of reference'. Those 'clocks' will vary with the gravitational potential ('static' as on a planet) and with motion and invariant mass. Then you have the idea of 'energy' as a process too, but that one is defined by 'interactions', so I will just mention it as a possible interference. There has been simple experiments done with extremely sensitive 'atomic clocks' where you have two synchronized on a table and then by moving one to the floor desynchronizing them, elegantly showing that there are no 'frames of reference' that can be said to be the exact same. This is more of a assumption from my side as they were synchronized on the table, but I would expect all positional points inside SpaceTime to differ slightly, which in a way makes it rather hard to define where that own 'frame of reference' should be situated. But we all have one as I think of it, even if it's only conceptual.

And as far as I know this is correct. The time 'measured out' for you, in your own 'frame of reference', where and whatever that may be, does not change. What changes is the relations you have, relative all other 'frames of reference', and that it do with gravity, invariant mass and motion (and 'energy' as an idea). And acceleration is a 'must' for any motion to exist, as far as I know, so that assumption is sort of 'baked in' into any motion defined, relative something else.

But there is also the fact that all uniform motions in a sense (black room scenario) is equivalent, meaning that there is no experiments you can do in there defining that 'motion', no matter what 'speed' you believe yourself to have relative some origin. All uniform motions can be seen as being 'at rest' relative 'gravity' giving you a geodesic. If we would find a possible definition of being 'still' relative SpaceTime, all of this would be wrong though but as it is any uniform motion, including a uniform constant acceleration becomes ambivalent phenomena, and only a non-constant acceleration will prove to you that it is you 'moving' without doubt in Einsteins universe.

If you use the definitions full out then all invariant masses, as planets and suns, are, as far as I can see, gravitationally 'accelerating phenomena, giving 'motion' a whole new meaning to me :)

Although, this is how I see it. And even though I believe it to 'fit' with the theory of relativity there might be others that see those clocks in another way. In a accelerating frame you can use those 'clocks' to define light as having different speeds by setting them up inside that spacecraft accelerating and then measure the 'time' the light takes from A to B and then from B to A. But that is all about the equivalence of acceleration with 'gravity' to me, and as we all know that light always take the path of least (no) energy expenditure that is no proof to me of different 'speeds'.

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There is one definition of being 'still' that one could consider though. The one in where you find no 'gravity', being 'at rest' with it as you are in a geodesic. Einstein defined 'gravity' as the metric of SpaceTime as I understand it. And then, if we define uniform motion as being of 'no gravity', the metric could be seen as 'gone'. But as uniform motion will take you from A to B that can't be correct.

Which leads me to my other notion. that this in fact, is a somewhat roundabout proof for his idea of space needing gravity to 'exist'. Because we know that, even though falling of a ladder on earth becomes a momentarily geodesic, that doesn't mean that 'gravity' as such stopped to exist. It just mean that you're 'at rest' relative it, for that short moment.

So Space is defined by 'gravity' to me. That doesn't state that 'invariant mass' and uniform constant accelerations is what 'gravity' must be. It is two properties we know of that according to Einstein can be seen as equivalent with a 'gravity', including the concept of 'energy' too as a guess :)

There might also be a possibility of the coupling to be more of SpaceTimes restricting than 'creating' gravity, as another wild guess :)
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But, in a very weird way, I can't help but wonder about if you could use this being 'at rest' versus 'gravity' as a definition of a 'null speed'? I'm actually considering it, which proves me to be slightly wacky I'm afraid. Then again, if Einstein was right? 'Motion' becomes a very wacky phenomena too :)

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