Nothing is more troubling than the concept of existence. Not: "Why am I here?" or: "Why is anything here?" (those both of those are troubling), but: "If none of us were here how could anything be said to exist?"

One can reason thus: "If I am not here to experience the world, how can it be said to exist?" On the face of it, it's absurd. The universe did not vanish when Julius Caesar died and was no longer there to experience it. The universe did not vanish when William Shakespeare died and was no longer there to experience it. The universe will not vanish when I die and am no longer there to experience it.

But what if everyone died? In what sense could the universe be said to exist? The argument that there is other life in our universe to experience things if the human race blows itself up--that argument won't do.

Scientists say it took eight billion years to create the elements necessary for life to exist. That means that for eight billion years there was no one around to experience the universe. Did the universe not exist during that time?

Similarly when the universe can no longer sustain life, the universe will not wink out in an instant. It will be a long, painful death stretching over billions of years.

So, yes, if there is no life whatsoever, the universe will still exist. It must.

You know what that implies: if there are other universes, universes we cannot perceive and which are not perceivable because they are devoid of life--their existence will never be known, will never have been known.

Think about this long enough and your head will begin to spin.