|Q2: if no one from the future has yet come to visit us, who from the present has travelled furthest into the future?
A: Sergei Krikalev, a Russian cosmonaut (dubbed the last Citizen of the USSR for when he was in space the Soviet Union collapsed) holds the world record for time travel by a human being; he orbited for 803 days, 9 hours and 39 minutes on board the MIR space station and the ISS and in so doing travelled around 0.023 seconds or 23 milliseconds into the future.
If you want precise figures, the MIR travels at 17,885mph and the ISS 17,210 mph and so over his 803 days Krikalev travelled around 0.023535 seconds into the future (as in, he was existing around 23 milliseconds in advance of life of earth).
Krikalev also holds the record for the most time spent in space by any human being.
He took the record for both time traveling and most time spent in space off the hands of Sergei Avdeyev who orbited for 748 days onboard the Mir space station travelling at 17,885mph and so experienced time dilation of about 0.022951 seconds, just a little less than Krikalev.
This mini-time traveling is a result of Einstein's theory of special relativity; the closer someone travels to the speed of light, the slower their clocks beat when compared with someone at rest. In fact, your time runs slightly slower than mine whenever you are moving and I am still, but usually the difference is so tiny that we cannot detect it. However, astronauts travel at great speeds for long periods of time, so these travellers experience an extra couple of milliseconds to the rest of us; two years on earth for us was two years and around two milliseconds for Krivalev.
It is more obvious if you imagine this all in larger quantities; if an astronaut were to travel near the speed of light, it might take him one minute to reach the nearest star. This one minute would equate to say, four years on Earth; in which case it is possible to say he would have travelled four years into the future, as experienced here on Earth.
An interesting paradox in the field of time travel is the grandfather paradox, first described by the science fiction writer René Barjavel in his 1943 book "Le Voyageur Imprudent". The paradox is this: suppose a man travelled back in time and killed his biological grandfather before the latter met the traveller's biological grandmother. As a result, one of the traveller's parents (and by extension, the traveller himself) would never have been conceived. This would imply that he could not have travelled back in time after all, which in turn implies the grandfather would still be alive, and the traveller would have been conceived, allowing him to travel back in time and kill his grandfather. Thus each possibility seems to imply its own negation, a type of logical paradox. This is discussed in the field of time travel a fair bit, there is no law of physics to suggest time travel is impossible, so how to get around things like the Grandfather Paradox? There are three ways of looking at it, the most interesting it that there are parallel universes, so if you did travel back you could kill someone who was identical to your grandparent but was, in this parallel existence, NOT your grandparent, who would still exist elsewhere on in another parallel universe.
S – Physics of the impossible by Michio Kaku.
Last edited by Molly Cule on Sun Apr 27, 2008 12:11 pm; edited 1 time in total