How do we know the ultimate fate of Earth?

Hello Dr Chris!

I am thoroughly enjoying listening to the last several years' podcasts during my Ferry Commute and every other reasonable solitary moment I have in the car, during a run or on a walk.

Here's my question... I've heard the story that in 2 billion years, the oceans will evaporate, and in another 7 billion years the sun will swell into a red giant and swallow up the earth... Sounds like a definitive end.... as with any fortune telling, I suspect there is some level of uncertainty with this... How was this predicted and how certain is the science community that this is our ultimate demise??

Sincerely,
Scientist-wannabe……凯文Krumwiede(专业nounced "crumb-weedy"... at least by the vulgar American descendants of the family)