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No Time Travel, Sorry
MOBE2001 writes "The bad news is that time does not change. Spatial velocity is given as dx/dt. Velocity in time(dt/dt) is nonsensical. As simple as that. In other words, no time travel to the past or the future, no motion in space-time, no wormholes and no hanky-panky with your great, great grandmother. There is only the changing present, aka the NOW. The good news is that distance is an illusion and we'll be able to travel instantly from anywhere to anywhere."
But in all my readings, I have learned one thing about physics. Nothing is "as simple as that".
"That's weird because I could have sworn when I went to bed last night it was yesterday and now its today."
Not really. Now it's now, and that's all that is. You remember yesterday, but that is a memory occuring now. The past doesn't physically exist. Nor does the future. The only real (i.e. existing physically) part of our time perception is now.
Computers are useless. They can only give you answers.
-- Pablo Picasso
Spatial velocity is given as dx/dt. Velocity in time(dt/dt) is nonsensical.
That would be a lovely argument if changes in position were measured in velocity.
You describe spacial travel as the dx, not the dx/dt. It stands to reason that you would describe time travel with the dt, not as some rate of travel we haven't come up with yet.
You are wrong.
Mach is the ratio of two speeds. Doing such produces a number in which the units cancel out. Speed/Speed = dimensionless. This also brings up another property of a dimensionless number, in that the value *does not change* in any unit of measurement. Mach 1.5 is the same in SI, FPS, or any other system.
Don't believe me? Here. "As it is defined as a ratio of two speeds, it is a dimensionless number." I'd hate to think you believe what you said... as others are taking you seriously.
Please don't respond back... I don't want to debate this further and you are most utterly wrong. I hope you don't work on... anything.
Why is motion in spacetime impossible? It has to do with the definitions of space and time and the equation of velocity v = dx/dt. What the equation is saying is that, if an object moves over any distance d x, there is an elapsed time d t. Since time is defined in physics as a parameter for denoting change (evolution), the equation for velocity along the time axis must be given as v = dt/dt which is self-referential. The self-reference comes from having to divide dt by itself. dt/dt always equals 1 because the units cancel out. This is of course meaningless as far as velocity is concerned.
Does the impossibility of motion in spacetime invalidate Einstein's relativity? The answer depends on whether one takes spacetime to be physically existent (as relativists do) or as an abstract, non-existent, mathematical construct for the historical mapping of measured events. If one chooses the former, one is obviously a crackpot or a fraud, or both. If one chooses the latter, then general relativity is to be seen as a mere math trick: the physical mechanism of gravity is still out there and it is incumbent upon physicists to find it.
This guy seems like an idiot to me. If you make the step to say that this is a mathematical construct that best describes our limited understanding of reality, which I believe to be true, you'll never be able to describe OR refute a more complete understanding of reality using that construct. You often need to discard and rethink the original concept or adapt it for it to improve. None of our knowledge, scientific or otherwise, is fully and completely right. Not one bit, it's just the best abstract model we've got. Everything we know will eventually be demonstrated to be incomplete, inconsistent or wrong. Which means you can't use any existing models to refute a new one. You can use them as a guide, you can say that the old and the new are inconsistent, but to refute them you need to go to the real world.
-1 Uncomfortable Truth