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Imagine two people. One leaves Earth on a spaceship to travel at high speed around the solar system. When he returns he would be younger than the person that he left behind?
In traveling he has travelled into the future whilst the person he left behind has travelled back in time? If time is a dimension does that mean that space has expanded in his travels for the person he left behind but not for him?
Simplified, You are right. Travelling at or close to the speed of light which requires a lot of energy and at the speed of light mass becomes infinite (mathematically speaking ). Gravitational field increases with mass and therefore increases with speed, the greater the gravitational field the slower time passes for the traveler with respect to a still observer. In short we can slow our ageing and isolate ourselves so that when we return say to earth, we have thus jumped to the future in a manner of speaking. Travelling back in time is a different question and thus far only has theories to describe and is far less realistic an option than jumping to the future via dilation. My personal opinion is that time is connected to the movement of space so moving forward is easy (by isolating yourself via time dialation) but moving backwards would require manipulating the entire space around you for which you want to travel back (example would be winding a video tape backwards in that you need control of the whole system or space) and thus far far harder.
What I was trying to determine in my first posting was the following.Is the movement of matter through spacetime at differing speeds giving us the impression that spacetime is expanding?
"During October, 1971, four cesium atomic beam clocks were flown on regularly scheduled commercial jet flights around the world twice, once eastward and once westward, to test Einstein's theory of relativity with macroscopic clocks. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40+/-23 nanoseconds during the eastward trip and should have gained 275+/-21 nanoseconds during the westward trip ... Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59+/-10 nanoseconds during the eastward trip and gained 273+/-7 nanosecond during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks."J.C. Hafele and R. E. Keating, Science 177, 166 (1972)
What one might ask though, is if that rocket accelerated at a perfect one G at all times? Would that then be equal to being on Earth? And also, would the Twins age differ after the traveling Twin returned?You might use this as a proof that a uniform acceleration and Gravity isn't exactly equivalent as there would be a age difference observed? but as long as we are thinking of it in form of energy expended I expect my argument to hold water any which way I've never really felt that to be the best definition though, to me it's uniform motion and 'free falling' so called 'inertial frames of reference' that seems the real 'equivalence' in SpaceTime. so thinking of it, the equivalence between a rocket moving at a constant one G and Earths gravity will only hold true as long as the 'frames of reference' don't join a common origin in the end, as we otherwise will see different effects. But taken in a black box, and measured only there, without any 'history' I expect it to be impossible to differ that rockets gravity from Earths. It's all about 'frames of reference'. And only when we introduce the 'history' of it will we be able to differ between the rocket uniform acceleration and Earths gravity, but, not while inside that rocket uniformly accelerating.
Now?Would that be me or Einstein?Both
if that rocket accelerated at a perfect one G at all times? Would that then be equal to being on Earth?