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There goes the neighborhood. Shutterstock

When astronaut Jim Lovell saw Earth outside his window during Apollo 8, the moment forever changed him.

"People often say, 'I hope to go to heaven when I die,'" Lovell previously told Business Insider. "In reality, if you think about it, you go to heaven when you're born."

Lovell was referring to the humbling truth about our fragile existence: Life exists here only because it teeters in a delicate and truly improbable balance. Our atmosphere, proximity to the sun, and countless other beautiful coincidences not only permit living things to survive and evolve, but also to thrive.

And yet, here we are, sitting at desks and in coffee shops and walking down the street like it isn't some kind of extraordinary miracle.

But all good things must come to an end.

One day Earth will be inhospitable to anything resembling life as we know it.

The life on this planet likely won't cease until billions of years from now. But, depending on how the stars align — in some cases, literally — it could also happen tomorrow or anytime in between.

Here are the many ways scientists believe the Earth as we know it could die.

This story was originally published on March 30, 2016 at 8:55 a.m. ET and updated with new information.