No seriously. Well, progress sort of. Theoretical progress, at any rate, and still hinging on one monster of a caveat: that spacetime is curved appropriately.
A group of researchers led by Amos Ori at the Technion in Israel has developed a theoretical model that overcomes a major hurdle in the current time travel theory. First of all, time travel requires the existence of closed timelike curves (CTC, aka closed timelike loops). In relativity theory, every particle has a worldline that describes its position in space and time throughout its existence. If the particle is in orbit around a mass of very high density that is greatly curving spacetime, it is possible that the worldline of this particle curves back on itself not only in space, but in time. The major hurdle in current theory is that for a time machine to exist, it would have to have negative density (another interesting topic, but I’ll have to save it for some other time). So according to Ori’s new theory, all that is needed is for gravity to have already begun curving spacetime appropriately and then for us to create “a vacuum space that contains a region field with standard positive density material.”
I believe it was Stephen Hawking who once said that time travel is not possible, because if it were, we would have already been visited by tourists from the future. Of course, there have been a multitude of objections to this, and it appears that Hawking has reversed his position, now calling time travel “impractical”. Among the objections to this are that the visitors could have sufficiently concealed themselves to avoid our detection (perhaps through invisibility cloaks, courtesy of the Department of Mysteries at St. Andrews College). Or perhaps whenever we travel back in time, we create a new timeline that branches off from our own and we are currently on the main trunk of the timeline tree. Of course, all of this is speculation, but the really interesting part is that Ori’s theory gives a solid answer to Hawking’s objection. The CTC cannot exist until an area of space that warps time has been built. As Ori puts it:
“The machine is spacetime itself. Today, if we were to create a time machine – an area with a warp like this in space that would enable time lines to close on themselves – it might enable future generations to return to visit our time. We, apparently, cannot return to previous ages because our predecessors did not create this infrastructure for us.”
So perhaps one reason we have never been visited by the future is because we have not yet built the time machine that will allow it. Here’s my prediction for what will happen.
- time machine is brought online
- 10 seconds later a mouse steps out
- 1 minute later a cat steps out
- 10 minutes later a dog steps out
- 1 hour later a monkey steps out
- the scientists study these animals for weeks
- not knowing what to do with them, and being scientists, they send the animals back into the time machine
- the world ends, but this is only a coincidence. The actual cause was the Large Hadron Collider producing a glob of strange matter that began rapidly converting the entire planet.