Better shelve that plan for a timehopping cultural tour of Renaissance Venice; physicists from the University of Hong Kong are convinced they’ve shown time travel to be impossible.
The possibility of time travel was raised 10 years ago when scientists discovered superluminal – or faster-than-light – propagation of optical pulses in some specific medium, the team said. It was later found to be a visual effect, but researchers thought it might still be possible for a single photon to exceed light speed. Du, however, believed Einstein was right and determined to end the debate by measuring the ultimate speed of a single photon, which had not been done before.
“The study, which showed that single photons also obey the speed limit c, confirms Einstein’s causality; that is, an effect cannot occur before its cause,” the university said.
I’ll give it a maximum of two years before someone has a counter-theory that makes it possible once again…
Well obviously these hacks at Hong Kong aren’t familiar with the flux capacitor, Delorean, or police boxes….both of which are not around anymore! THINK ABOUT IT.
Someone in the future will figure out and go back in the past and prove these idiots wrong, and then this whole discussion will never have happened.
It seems to me that they only determined that light (presumably in a vacuum) can’t go faster than light.
I can live with that…
Time travel is still theoretically possible. Before this work was done there were AFAIK 4 possible mechanisms for time travel allowed by the current state of the Theories of Relativity; this removes one of them. The ones that are left are:
1. Creation of closed timelike geodesics with Tipler Machines or hypermass black holes. AIUI there’s a lot of skepticism about this alternative, because it might require infinite masses or infinite dimensions, but I don’t believe that’s yet been proved.
2. Creation of wormholes with lengths shorter than the normal space distance between mouths, followed by moving one mouth at relativistic velocities to make its proper time fall behind the proper time of the stationary mouth. The consensus these days is that it isn’t possible to hold a wormhole open while sending something through it, but since we’ve never seen a wormhole I think the jury’s still out on this.
3. If tachyons exist, and if interactions between tachyons and tardyons are possible (not considered likely by most physicists), then it’s possible to at least send signals to the past, and possibly to send objects.
Oh, there’s also Gödel’s discovery that closed timelike geodesics are possible in a rotating universe, but there’s no evidence that our universe is rotating, so I don’t hold much hope for this.
In other words, don’t sell your tickets to Renaissance Italy just yet, but dont make any immediate plans for the trip.
Do you think it might be linked to this?
http://www.metro.co.uk/news/861018-china-bans-time-travel-on-tv-and-at-the-cinema