I’ve been critical of multiverse pseudo-science because it doesn’t make any testable predictions, but it seems that tonight there really is one. According to this new preprint, multiverse arguments guarantee that time will end, with the expected amount of time left before the end about 5 billion years and
There is a 50% chance that time will end within the next 3.3 billion years.
The argument seems to be that multiverse arguments require introducing an artificial cut-off to get finite numbers, so the cut-off must be there and we’re going to hit it relatively soon on cosmological time scales. The age of the universe is about 13.75 billion years, but we’re getting near the end, already entering late middle-age to senior-citizen time-frame. One interpretation given of this result is that:
we are being simulated by an advanced civilization with a large but finite amount of resources, and at some point the simulation will stop.
It turns out that you don’t even need the whole apparatus of eternal inflation to see that time is going to end. All you need to do is to think about sleeping and waking up, which, according to the paper, leads to the “Guth-Vanchurin” paradox:
Suppose that before you go to sleep someone flips a fair coin and, depending on the result, sets an alarm clock to awaken you after either a short time or a long time. Local physics dictates that there is a 50% probability to sleep for a short time since the coin is fair. Now suppose you have just woken up and have no information about how long you slept. It is natural to consider yourself a typical person waking up. But if we look at everyone who wakes up before the cutoff, we find that there are far more people who wake up after a short nap than a long one. Therefore, upon waking, it seems that there is no longer a 50% probability to have slept for a short time.
How can the probabilities have changed? If you accept that the end of time is a real event that could happen to you, the change in odds is not surprising: although the coin is fair, some people who are put to sleep for a long time never wake up because they run into the end of time first. So upon waking up and discovering that the world has not ended, it is more likely that you have slept for a short time. You have obtained additional information upon waking – the information that time has not stopped – and that changes the probabilities.
However, if you refuse to believe that time can end, there is a contradiction. The odds cannot change unless you obtain additional information. But if all sleepers wake, then the fact that you woke up does not supply you with new information.
Update: Lubos doesn’t think much of the paper:
But holy crap, if physicists don’t lose all of their scientific credit by publishing this pure garbage and nothing else for years, can they lose their credibility at all? Does the institutionalized science have any checks and balances left? I think that all the people are being bullied into not criticizing the junk written by other people who are employees of the academic system, especially if the latter are politically correct activists. And be sure, some of the authors of this nonsense are at the top of it.
This is just bad. I urge all the sane people in Berkeley and other places to make it very clear to Bousso et al. – and to students and other colleagues – that they have gone completely crazy.
Update: In other pseudo-science news, the latest Scientific American features a piece by Hawking and Mlodinow based on their recent book.