So, as we approach Earth Day on April 22, spare a thought for our planet's mortality.
Ignore all the fake theories of doom, there is only one guaranteed doomsday approaching, and unfortunately (or fortunately, depending on which way you look at it), there will unlikely be anyone to see it happen.
What am I waffling on about? The sun? Eating the Earth? Yes. When the sun runs out of fuel in 4-5 billion years' time, things are going to get a little ... toasty.
For starters, our sun is a "main sequence" star. It burns hydrogen in its core, generating energy and fusing it to make the heavier element helium. It has been doing this for the last 5 billion years or so, providing the Earth with the necessary energy for life to thrive.
Eventually, though, like all main sequence stars, it will run out of its hydrogen fuel. And herein lies the problem.
As the rate of fusion reactions in the core begins to slow through lack of hydrogen - much like your car's engine spluttering as it runs out of petrol - there is less outward radiative pressure countering the sun's gravity. The core will therefore shrink, forcing helium atoms closer together. At a certain point, helium will start to fuse, creating even heavier elements like carbon and oxygen.