In about a billion years the sun will exhaust enough nuclear fuel to cool and expand, boiling the oceans, blowing off our atmosphere, and turning Earth back into a sterile rock.
It's predicted by astronomers and physicists who study stellar evolution.
antisthenes|8 years ago
The Sun will gradually keep getting hotter and slightly more luminous up to that point.
Earth will be a desert long before the Sun exhausts nuclear fuel to start expanding and becoming a red giant.