2 ms·

We all travel through time at varying speeds all the time: There are two twin brothers. One brother goes on a space journey traveling at 99% of the speed of li

by maeon3 16y ago

We all travel through time at varying speeds all the time: There are two twin brothers. One brother goes on a space journey traveling at 99% of the speed of light. The space traveler stays on his journey for one year, whereupon he returns to Earth. On Earth, however, seven years have elapsed, so his twin brother is 7 years older at the time of his arrival. This is due to the fact that time is stretched by factor 7 at approx. 99% of the speed of light, which means that in the space traveler’s reference frame, one year is equivalent to seven years on earth. Yet, time appears to have passed normally to both brothers. Question: Did the traveler go forward in time or did the Earthbound brother go backward in time when they meet up later? Question: How is it possible that one of the brothers shifted 7 years and yet they can meet in the same universe?

Nick_C 16y ago
Are you asking to learn, or to provoke others to think? If you were asking, reply and I'll dig up some links about how c is the speed of the universe and equals 1, spacetime and mass, and how velocity changes the relationship of time in spacetime.
- maeon3 16y ago
  I'd rather you answer the first one, how a person can move forward in time while staying in visual contact of the person staying behind. If you can answer that and prove it, then you will have made an amazing contribution to the understanding of the universe. Two kids are on a merry go round, one in the center, one on the edge, the edge is traveling at .99 speed of light, when they communicate via cellphone, one voice sounds very deep and low, the other sounds fast like a chipmunk. Yet if you were to sample the sound relative to each point, you would hear a normal voice, because of some bizarre principle.
  - Nick_C 16y ago
    (I have to make some assumptions about your understanding of relativity.) The big breakthrough that Einstein made in general relativity was the 'relative' bit. There is no absolute thing of 'time', no universal tick of a clock. There is the time as experience by the traveller and the time as experienced by the brother. So there is no discontinuity that has to be merged when they meet. It seems to me your question makes an implicit assumption that there is a universal tick that is thrown out of whack when the brothers meet. But there isn't, so the question is invalid. I wonder if perhaps you regard space as one thing and time as a separate thing. It might help to throw that out and regard it as a four-dimensional object called spacetime. For the merry-go-round, I'm not sure why you say one voice sounds low and the other high. They won't. Einstein's big thought experiment was to realise that the speed of light is constant no matter the speed of the observer. As an aside, it is an unfortunate historical artifact that we call c the speed of light. It isn't. C is the "speed" of any massless particle in spacetime; it is unitless and equals 1. Photons are massless so they travel at c. http://www.reddit.com/r/askscience/comments/g6zbd/if_we_depart_earth_at_the_speed_of_light_and/ http://www.reddit.com/r/askscience/comments/g6zbd/if_we_depa... http://www.reddit.com/r/askscience/comments/fu5io/help_me_understand_time/ http://www.reddit.com/r/askscience/comments/fu5io/help_me_un...

by maeon3 16y ago

Nick_C 16y ago

Are you asking to learn, or to provoke others to think? If you were asking, reply and I'll dig up some links about how c is the speed of the universe and equals 1, spacetime and mass, and how velocity changes the relationship of time in spacetime.

maeon3 16y ago
I'd rather you answer the first one, how a person can move forward in time while staying in visual contact of the person staying behind. If you can answer that and prove it, then you will have made an amazing contribution to the understanding of the universe. Two kids are on a merry go round, one in the center, one on the edge, the edge is traveling at .99 speed of light, when they communicate via cellphone, one voice sounds very deep and low, the other sounds fast like a chipmunk. Yet if you were to sample the sound relative to each point, you would hear a normal voice, because of some bizarre principle.
- Nick_C 16y ago
  (I have to make some assumptions about your understanding of relativity.) The big breakthrough that Einstein made in general relativity was the 'relative' bit. There is no absolute thing of 'time', no universal tick of a clock. There is the time as experience by the traveller and the time as experienced by the brother. So there is no discontinuity that has to be merged when they meet. It seems to me your question makes an implicit assumption that there is a universal tick that is thrown out of whack when the brothers meet. But there isn't, so the question is invalid. I wonder if perhaps you regard space as one thing and time as a separate thing. It might help to throw that out and regard it as a four-dimensional object called spacetime. For the merry-go-round, I'm not sure why you say one voice sounds low and the other high. They won't. Einstein's big thought experiment was to realise that the speed of light is constant no matter the speed of the observer. As an aside, it is an unfortunate historical artifact that we call c the speed of light. It isn't. C is the "speed" of any massless particle in spacetime; it is unitless and equals 1. Photons are massless so they travel at c. http://www.reddit.com/r/askscience/comments/g6zbd/if_we_depart_earth_at_the_speed_of_light_and/ http://www.reddit.com/r/askscience/comments/g6zbd/if_we_depa... http://www.reddit.com/r/askscience/comments/fu5io/help_me_understand_time/ http://www.reddit.com/r/askscience/comments/fu5io/help_me_un...