[dfa0]

We don't know how much oil exists,but we do know it is finite.

The sun's energy will out last us all, millions of times over. Plants have it figured out. We should ask them.

Plus what happens when we are ready to leave Earth? Surely we'll need a way to feed off of the stars then anyway, so why not start now.

[sliverstorm]

The supply of sand is also finite, but we aren't likely to run out any time soon.

Just because the supply is finite, doesn't automatically mean we will exhaust it.

[byroot]

Actually, as stupid as it sounds, we do start to run out of sand to make concrete in some areas.

A quick search about "sand shortage" will show you.

[ShirtlessRod]

True, but I would guess that oil is used at a much higher rate than sand, especially considering the relative availability of each.

[mistermann]

The question is whether we will use it all up before renewables become cheaper though.