Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space
The Guide[src]

Space is big.

Space is one of the most basic and most important components of the Hitchhiker's Guide series. It is what Arthur Dent and Ford Prefect are launched into after enduring Vogon poetry. It is what is traversed by the Heart of Gold. It is what is left of Earth, along with many particles of dust, when it is destroyed. It is also infinite. It is constantly expanding. Because of this fact, "it is known that there is an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you meet from time to time are merely the products of a deranged imagination."


The Earth seen from space.

The Guide also says that "If you hold a lung-full of air, you can survive in the total vacuum of space for about 30 seconds. But with space being really big and all, the chances of being picked up within that time are 2 to the power of 2,079,460,347 to 1 against, which by a staggering coincidence is also the telephone number of the Islington Flat where Arthur went to a fancy dress party, and met a very nice young woman whom he totally blew it with."