Interview: Time Travel and the Speed of Light

In case you missed it (which is likely since it was on in the middle of the night), I was interviewed on “Overnight America with Jon Grayson.” Jon and I talked about a press release put out by a team of Hong Kong scientists who claimed that, even including quantum effects, light can’t travel faster than c, which they claimed meant that time travel was impossible.

It was an interesting chat, and Jon is a great interviewer, but:

  1. It would have been really nice if Dr. Du (the PI on the experiment) had actually put the preprint up on the arxiv before sending out press releases. I, and everybody else commenting on this, had no way of knowing what he actually did.
  2. Photons don’t need to locally exceed the speed of light to make a time machine. There are plenty of GR related time machines (wormholes, cosmic strings, rotating black holes, etc.) which do not require quantum effects to work (but which may be impossible for completely different reasons). Putting the detail about this experiment “disproving time machines” was pretty blatant, quite unnecessary, and wrong.

    The experiment, as near as I can tell, was quite elegant, and the result was significant. While it wouldn’t have made the same splash, simply describing the results would have been much better, scientifically.

Jon was a real pro. I especially liked near the end when he asked where else people can learn more. “Seriously?”, I answered. “How about here?”.


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