I’m listening to an interview on KQED’s forum (local NPR station’s call in show) with science journalist Timothy Ferris. Apparently he just wrote a new book about amateur astronomy which I don’t doubt is well researched and accurate but as people called in he apparently felt the need to opine on time travel and quantum mechanics ‘scientific’ matters and I was appalled. Since he’s also written a book called “The Whole Shebang” his misleading answers can’t be explained as mere failure to research. However, I’m inclined to think that in this case the fault lies with the physicists themselves (either for doing bad philosophy or using mislead metaphors.

It started with someone bringing up the Fermi paradox (why haven’t advanced alien civilizations contacted us yet). The host then steered the question towards whether this was an argument against time travel as well (failure to see time travelers). Timothy Ferris replied that he didn’t find it very compelling because he expects time will be lack a deck of cards so that if you go back in time of forward in time you end up in one of many possible pasts or many possible futures. While he admitted it was just his expectation he clearly conveyed the sense that it was a possibility that experts would take seriously.

I happen to think the very idea of something being time travel requires that we go back into the past not merely enter some universe that looks like the past.¹ However, let’s set this point aside. I suspect the journalist was referencing some approaches to quantum mechanics that go by the name of sum over histories or multiple histories. Possibly he meant to refer to many minds or many worlds theories. The problem is that traveling to an ‘alternate’ past doesn’t even make sense in any of them. Supposing it was true and even meaningful that we have multiple histories in this QM sense we would have multiple presents as well. What the hell would it even mean for a person, who is really a superposition, to visit one component of a prior superposition? Pure many worlds theories only really make sense² if we understand them as collapsing down to a many mind’s theory and it certainly isn’t clear what it would mean for a mind that rides atop the superposition to time travel by itself, certainly not in the sense of some dude from the future appearing.

That’s confused and I was annoyed that he said it with such apparent authority but what really got my goat was when he talked about how interesting it would be if we ended up with quantum computers since we couldn’t explain their processing power with just one universe and would have to say that they use other universes to do their computations. This is just a lie that is being pushed on the public. The fundamental laws of nature could just offer us an oracle that computer anything we wanted as fast as we want. For all we know there is some special experiment we can do that reveals the true bits of 0′ (the set of the halting problem). Worse this is certainly not anything scientists have or can test. It is purely unjustified bad philosophical speculation that misleads the public.

I’m not sure whether to be mad at the people who promote this crap or applaud the physicists for great PR. Maybe we should just adopt this for math. Push the whole confusion about Godel’s theorem a bit more and try selling the Banach-Tarski paradox as a proof that “space is an illusion.”

Bit about quantum computer