David Kipping

fly through the clouds of Venus or you could just do these enormous jumps on these small moons where you can essentially jump as high as a skyscraper and traverse the moon.

So there's all sorts of wonderful ice skating on Europa might be fun.

So don't get me wrong, I love the idea of us becoming interplanetary.

I think it's just a question of time.

Our own destructive tendencies are

as you said earlier, are at odds with our emerging capability to become interplanetary.

And the question is, will we get out of the nest before we burn it down?

And I don't know.

Obviously, I hope that we do, but I don't have any special insight that... There is somewhat of a...

annoying intellectual itch I have with the so-called doomsday argument, which I try not to treat too seriously, but there is some element of it that bothers me.

The doomsday argument basically suggests that

you know, you're typically the mediocrity principle, you're not special, that you're probably going to be born somewhere in the middle of all human beings who will ever be born.

You're unlikely to be one of the first 1% of human beings that ever lived and similarly the last 1% of human beings that will ever live, because you'd be very unique and special if that were true.

And so by this logic, you can sort of calculate how many generations of humans you might expect.

So if there's been, let's say, 100 billion human beings that have ever lived on this planet,

then you could say to 95% confidence, so you divide by 5%.

So 100 billion divided by 0.05 would give you 2 trillion human beings that would ever live.

you'd expect by this argument.

In general, the planet has a 10 billion population, so that would be 200 generations of humans we would expect ahead of us.

And if each one has an average lifetime of, say, 100 years, then that would be about 20,000 years.