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Physics, Astronomy & Cosmology / Re: If I moved backwards at the speed of light holding a torch, what would happen at the start of th
« on: 22/11/2017 16:17:56 »Quote from: Jeffrey
In a universe containing only one object with the only two states the object has are constant velocity and straight line motion and that is the only thing observable then how would the passage of time be marked?
In it's own inertial frame of reference nothing is happening.
Indeed, how would space or motion be measured.
I found this in my notes from a few years ago, when I was struggling with some basic ideas.
I remind others that I write my notes as though I were trying to explain a point to someone with even less knowledge than I might have, so anything that sounds patronising is not intended as such.
“Imagine you are in a space craft at the “centre” of an infinite, void. Nothingness stretches infinitely in every direction. You perceive yourself as being stationary, but suppose you engage your engine and travel at fractionally below light speed for five seconds, then stop. You review your position; are you 1,500,000 kilometres away from where you started? Is there now more nothingness behind you than there is in front? On reflection you conclude that there is still an infinity of nothingness in every direction. There is in fact nothing to which your motion can be relative. You have “moved”, but you are still in the same place - in the “centre” of an infinity of nothingness - your movement has no real meaning.
You can argue that if you use your engine to propel your craft forward you will be able to detect your motion, as you will be accelerating, and accelerated motion can be felt by the person doing the accelerating. Undoubtedly this is so, but as you had no way of telling if you were in motion or not before you engaged your engine, you cannot tell if you have moved off from a standstill, if you have simply increased the speed at which you were already travelling, or if you have decreased your speed; which would be the case if you had already been travelling “backwards” without being aware of that fact.
However, because no matter how far you move, you will still perceive yourself as being in the same place, the whole question of how far you might have travelled, and at what speed, is purely academic.”
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