If gravity were somewhat stronger or weaker, stars wouldn't exist, and neither would you. And the same can be said of other constants of physics. Several have to be 'just right.'

Five centuries ago, Copernicus upset humanity's applecart with the news that the Earth is not the center of the cosmos. It could be that, before you've paid off your house, we'll learn that the universe is not the center of the universe, either!

'Eternal inflation,' as it's called - the endless generation of new universes - may be a hyper-cosmic imperative. It seems that it must happen.

Seth Shostak Quotes