UCSB Science Line

Hi! I recently watched a you tube video titled: Discovery - world's first time machine. In the video, a scientist by the name of Ronald Mallett discusses how the bending of space-time around a black hole could send a craft back in time without violating the light speed barrier.

Wouldnt this suggest that one could use gravity to send a craft back into time ("exceeds the speed of light from an observers point of view)? Could you explain to me a little bit on the physics of the situation that Ronald Mallett was discussing, and exactly how an object could be considered to be going back in time in the situation that was discussed in the video? (The first 1 minute and 19 seconds of the video) Are there any formulas that I could use from Einsteins theories to calculate or to mathematically verify Ronald Mallett's conclusions?

I'd very much like to have a mathematical understanding of how Ronald concluded that an object in such a situation (or a situation like it) would go back in time according to Einsteins theories. Thank you so much for your help!

Question Date: 2010-04-10

Answer 1:

I think I can confidently say that the answer is no: you cannot verify Mallett's conclusions using Einstein's theories. The fundamental problem is this: Einstein's theories consist entirely of classical gravitation. Any looping of space time around a black hole would depend upon quantum gravitation (and the engineering considerations of designing a craft that could survive that are probably unsolvable), something that has been proposed post-Einstein. Quantum gravitation has to date not been observed, so theories about it are impossible to test. I guarantee you that whoever finds evidence for that is going to get the Nobel Prize.

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