Arbitran, on 08 May 2012 - 12:00 AM, said:
I will say it again: the 'area' by which velocity is measured is any given object's shifting position, relative to every other object in the universe. The 'area' by which one can measure speed is the universe itself. And I must say I'm very puzzled that you don't find space-time to be a tangible, real concept. What do you propose the universe is composed of, I wonder, if not space, time, and all that entails? Perhaps a good way to explain it all is to bring it back to Einstein, who determined that gravity is not true force, as Newton had speculated, but an effect caused by the distortion of space-time in the presence of mass-energy. The amount of density or mass which an object possesses in space determines its gravitational field, which warps the very real, tangible system called space-time in such a way as to produce the effect which, for example, keeps us all on the ground. As I have explained, if a region of space (or theoretically even a parallel universe with inverse mass-energy laws) could contain objects of negative density or energy, then super-luminal velocities could possibly be attained, for the simple reason that under the set of dynamical mechanics which our universe operates, the ultimate speed which an object of standard mass or energy can attain is the speed of light: this is because photons possess zero mass, being pure energy. Therefore, it is not too hard to work out that the only possibly means of attaining a superior velocity would be with the introduction of a completely alien, negative-density object. And even that is purely theoretical, as to date there is no direct evidence of any such objects. In essence, to answer your question more accurately, the medium under which velocity is finally restricted is mass, or gravity.
"The" velocity of every object is relative specifically to every other specific object in the universe. To things at rest on the surface of the Earth they are usually at rest relative to other things that are at rest relative to the surface of the Earth, except in cases where the surface of the Earth is in motion relative to other parts of the surface of the Earth. The velocity of the moon is different relative to the sun, relative to the Earth, relative to Sirius, relative to Saturn, relative to every man made satellite, relative to you, etc. I find it hard to believe and very disappointing that you of all people don't seem able to appreciate the significance of this, but if xts are going from star system to star system I'm convinced that they appreciate it, and even the lowly humans who bring human space vehicles back to the planet must be able to appreciate it too.
I don't believe that "space" exists but instead there is nothing. In some places the nothing contains matter and in other places it doesn't. Since I don't believe anything we know of is truly at rest the parts of the nothing that contain matter in one instant are likely not to soon after because things keep moving. In order for "space" to exist that means it should have an end at some point, but the only place the nothing or space does end is where it's occupied by something else. If space were to have a true "end", then something would have to replace it. That's why I believe it doesn't exist. The same is true of time, plus the fact that if time did "exist" and have influence on things then it would have to influence all things in the universe simultaneously and for eternity and would require tremendous ammounts of energy, but if there is no time then the questions about how it could exist and be supplied by the necessary energy are answered by its nonexistence. That also would explain why it has never been detected, and why humans can make up pretty much whatever they want to about it.
Edited by nopeda, 08 May 2012 - 11:21 PM.