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# c: an obstacle of our own creation?

#### ThePromenader (878501) writes | more than 3 years ago

2

I must admit that it was difficult to wrap my layman head around the idea of 'time travel'. My reading (and watching, thanks to an online friend of mine who will know who he is should he read this) involved many presentations involving metre sticks, clocks, pythagorean triangulation and space travel - or in other words, 'time dilation'. I get the concept, but there's something about the theory's point of view, if not its motivation, that bothers me.

I must admit that it was difficult to wrap my layman head around the idea of 'time travel'. My reading (and watching, thanks to an online friend of mine who will know who he is should he read this) involved many presentations involving metre sticks, clocks, pythagorean triangulation and space travel - or in other words, 'time dilation'. I get the concept, but there's something about the theory's point of view, if not its motivation, that bothers me.

The base of Einstein's concept is: light always travels at the same speed relative to the observer. He explained his theory, in a thought experiment sometimes called "Einstein's mirror", by imagining himself in a train travelling at a speed of light while looking at a mirror: would he see a reflection? His conclusion was 'yes'.

The most common presentation explaining time dilation I saw was one involving two parallel mirrors and the behaviour of light between them if one was moving. True, the beam of light between the originating mirror at its beginning state, the 'immobile' mirror and the originating mirror at its end state is 'longer' than a line between two immobile mirrors, but scientists have seemed to conclude that, since there is no speed faster than light, it must be time that is changing. Something bothers me about this - to no end.

It was the 'speed relative to the viewer' part that intrigued me the most, and I went to bed with my thoughts full of spaceships, trains and mirrors. If I were (in bed) watching Einstein speeding away from me on a light-speed travelling train with a mirror in front of his face, with himself still able to see his own reflection because light was being reflected relative to his own position and speed, what would be the speed of his reflection according to me? My repeated conclusion was: his reflection, at least in the light being sent towards his mirror, would have to be travelling twice the speed of light. But nothing can travel faster than the speed of light (according to 'our' point of origin), right? If relativity really does hold true, wrong.

If I reduce the Einstein mirror example to two stars hurtling away from each other at light speed (which one is 'still' is irrelevant), the photons emitted from opposing sides of the stars at any given point of time would be travelling three times the speed of light relative to each other. Yet modern physics insists on adding time into the equation, and tells us that it is time that is changing, not the light speed. Either I am missing something, or there is so much wrong with this.

The obstacle we are facing is our own concept of 'light speed' and use of 'light year' in our calculations. If light is indeed an independent electromagnetic wave that always travels at the same speed from its point of origin, and if that 'point of origin' can be travelling at any speed at all, what is there to say that travel of light speed 'is not possible'? The problem here is that although we have no measure above the speed of light with which to compare things, that doesn't mean that anything beyond the limit of our measure can't exist. From our present point of observation, in a universe that originated most probably at the same point in time, we just can't see it, or haven't seen it yet.

To take this thought to its full extent, imagine a space ship accelerating away from earth (to some unknown destination). From a point of rest near earth, imagine that it maintains a continued state of acceleration (let's leave time out of the equation for now) and that it achieves the speed of light. Now, let's imagine the environment in and around that spacecraft at that precise point in time.

First off, what is that 'speed of light' velocity the spaceship is at? That 'speed' is measured relative to its, or our own, point of rest. If relativity holds true, and there is no limiting 'ether', any physical phenomena created by that spaceship at that speed would have that speed and position as its point of origin; for the calculation of any physical occurrences on that spacecraft, our position or point of reference doesn't matter to any equation of events onboard. A nuclear reaction on that spaceship would occur exactly in the same way as it would on earth (if the spaceship somehow had a 'false gravity' equalling earths), and any outward-going force, such as thrust (into a vacuum), should react in the same way at its speed as it would in ours. All anyone onboard would feel is the force of the ship's acceleration - in fact, without any point of reference to see outside of the ship's porthole, they would have no idea at all about the speed at which they were travelling; should the ship shut down its engines, with no drag to slow it down, it would maintain its 'velocity' (in relation to 'us'), yet it would seem to those onboard that the ship was at a total standstill. If the core idea behind relativity holds true, it can't be any other way.

Our problem today is that we are using the speed of light as a barrier in addition to its use as a unit of measure. Just because we have not yet been able to accelerate any object near/past the speed of light doesn't mean it's not possible; once we do make it there, any electromagnetic wave phenomena we create at that velocity will occur, if we still insist on using ourselves as a point of reference, at twice the speed of light in the direction away from us.

The reason we remain stuck in this reasoning is probably a) the universe itself has a single point of origin (the Big Bang), and everything we see is 'relative' to that moment; b) all the universe's mass, and what little of it we have been able to move ourselves, moves at a speed only a fraction that of the speed of light. Still, according to relativity, the light shining forward from a projected "flashlight bullet" should travel at a velocity to its own (light speed) plus the bullet's velocity at the time it was emitted. Even a bullet's speed is minuscule compared to that of light: I wonder if today we have the tools to test this sort of theory.

So, to sum up: just because we ourselves are unable to see or measure any velocity above or relatively close to the speed of light (velocities created outside our, or the big bang's, point of reference), doesn't mean that nothing beyond hasn't, won't, or can't, occur. I don't yet understand the motivation behind the mathematical acrobatics of 'time dilation' just to preserve a threshold at/below the speed of light; were we to maintain time as a constant in both sides of its equation, or remove it entirely, the result would be a speed faster than the speed of light - or the speed of light plus the 'terminal speed' of the mirror capturing the returning light ray, and I don't see anything wrong with this.

'Bending time' is much like trying to measure a rod with a shorter string by bending the rod; if the string is our largest known velocity (the speed of light) and the rod the real velocity, than that rod has a velocity is greater than any we know, or has a velocity greater than any we can measurably create today, and I don't see any reason why we can't just accept this.

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### C-max (1)

#### JWSmythe (446288) | more than 3 years ago | (#35009186)

Nice writeup.

It reminds me of a conversation I've had with people regarding the fact that we are always exceeding the speed of light. I've proven (on scratch paper, without astrophysicists handy), that there are plenty of examples of how we exceed the speed of light daily.

Consider this. The "Big Bang" occurred, and all matter exploded away from the center of the universe at a high rate of speed. That speed can be anything greater than 0.5*C, but is estimated to be closer to 1*C. At that moment, any two objects now flying in opposite directions at greater than 0.5*C would have a relative speed greater than 1*C. We would never see the objects traveling in the opposite direction, since the light only travels at 1*C. It would be like two aircraft traveling apart at Mach 0.6 in opposite directions. They'd never hear each other, although their sound is traveling at Mach 1 in all directions.

Another interesting tidbit is if you consider the orbital velocities of satellites. That's natural objects, not those chunks of metal we've put in orbit. If you consider the orbital speed of the galaxy, and the orbital speeds of the the solar system within it, you can easily see speeds of in excess of -1C (two points moving apart faster than the speed of light), and greater +1C (two points moving together faster than the speed of light). We can observe objects closer to our own speed with redshift and blueshift. Other objects may be outside of our perception due to their speeds being well beyond what we currently have the technology to observe.

### TIME OUT! (1)

#### mcgrew (92797) | more than 3 years ago | (#35009482)

You have to remember that these theories are mostly mathematical constructs. Einstein said "if you put your hand on a hot stove, a minute lasts an hour. If you're having a nice conversation with a pretty girl, an hour lasts a minute. That's relativity.

It was the 'speed relative to the viewer' part that intrigued me the most, and I went to bed with my thoughts full of spaceships, trains and mirrors. If I were (in bed) watching Einstein speeding away from me on a light-speed travelling train with a mirror in front of his face, with himself still able to see his own reflection because light was being reflected relative to his own position and speed, what would be the speed of his reflection according to me? My repeated conclusion was: his reflection, at least in the light being sent towards his mirror, would have to be travelling twice the speed of light. But nothing can travel faster than the speed of light (according to 'our' point of origin), right? If relativity really does hold true, wrong.

The light will reflect off the mirror n nanoseconds after it leaves his face, so no matter where you are relative to him, the reflection will be n nanoseconds behind reality.

If I reduce the Einstein mirror example to two stars hurtling away from each other at light speed (which one is 'still' is irrelevant),

You won't have two stars moving away from each other that fast. The faster you go, the more mass you have and the slower time appears to go. At the speed of light, anything that has mass would have mass equal to the mass of the entire universe, unless I'm misunderstanding it. So in practice, the actual top speed you could travel would be much less than the speed of light.

If light is indeed an independent electromagnetic wave that always travels at the same speed from its point of origin, and if that 'point of origin' can be travelling at any speed at all, what is there to say that travel of light speed 'is not possible'?

I read recently that a physicist surmised that Star Trek warp drive could in fact be possible, as long as it was spacetime itself that was moving (a "warp bubble" if you will.

As to the "bending time", I have my doubts about time being a real dimention. Yes, time as a dimention works cleanly in the mathematical constructs, but unlike the other three dimentions, there is only one way. Horizontal: left and right. Vertical: Up and down. Distance: forward and backward. Time: Forward; there is no backwards.

However, Stephen hawking (who's WAY smarter and more knowledgeable than me) disagrees: (this is a link, but you wouldn;t know it from /.'s new design) STEPHEN HAWKING: How to build a time machine [dailymail.co.uk] "All you need is a wormhole, the Large Hadron Collider or a rocket that goes really, really fast"

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