[Grando Calrissian]

It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them. 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 may meet from time to time are merely the products of a deranged imagination.

[RightWhale]

There is an obvious question that needs to be asked. If another earthlike planet is found, what will happen here on earth? Will some social groups become disfunctional? Will the people of earth unite in a common cause of some kind? Will there be mass panic and looting? What is the range of liklihoods?

[Boiler Plate]

How could it be possibly be "Known" that there is infintite anything? The only way to know would be to count or measure the item in question and only when you couldn't count due to it being infinite could it then be known. Of course you have an infinite amout of time and counters to try and accomplish the task.

[donh]

imply because there is an infinite amount of space for them.

By our current lights, this is not the case. The universe is finitely bounded by the expanding envelope started by the Big Bang.