James Arthur was some sort of amateur scientist – I don't know what his history was – but anyway he endowed these lectures at NYU which have to given in... every year; he endowed them with a substantial sum of money, and the lectures have to be given on time and its mysteries, so every year they have to find somebody to talk about time and its mysteries. So I was invited to do that. It was a wonderful opportunity then to talk about wild stuff, and so I talked about the future of the universe and the question, essentially, whether life could survive for ever in an expanding and cooling universe, and the answer is yes. I mean that was sort of surprising but it turned out to be positive; that as far as the laws of physics and information theory are concerned, a cold universe actually is favourable to life. Life doesn't depend on absolute quantities of energy, life depends on signal to noise ratio; that, you've got to be in a situation where the signals are larger than the noise, so cold is actually more favourable to life than hot. So as the universe gets colder the quantities of energy available are smaller, but the demands become smaller even more rapidly, so actually you win as the universe gets colder. And it turns out, if you take a finite store of energy and if life is able to adapt itself toward colder temperatures, you can actually continue forever staying alive, processing more and more information on a finite store of energy. The process converge... the energy demand integrated to infinity converges, even though the amount of information diverges to infinity. So that's sort of neat, and so in principle there's... there's no automatic death as the universe gets cold.
[Q] And expands – this is for an open universe which keeps on expanding.
Which is now probably confirmed by the observations. I mean the observations have always been sort of wavering between flat and open. Now the observations point pretty strongly to the universe being open, so it will continue to expand for ever and it will cool off. And so this is good news if you want to survive for ever. And I think that this maybe actually not just a game, I mean it may really have some substance to it. And the other question which I looked at, which was also interesting, was how well you can communicate over huge distances, again in a cooling universe with limited supplies of energy, and it turns out there also that you never need lose touch with your neighbours, you can continue communicating by radio.
[Q] It can take a long time.
It takes an enormous time, of course, and the message, the bit rate, gets less and less, but the time available is infinite so that you can afford to wait. So the universe can in fact maintain communication over these enormous distances and times as long as you want.
