Eli5: if the space is a vacuum, why doesn’t it suck out all the air from earth

Question

As far I understand gravity holds the air back down, but surely it isn’t like a seal where air can’t escape

In: Planetary Science

Answer 1

A vacuum doesn’t suck, it’s the pressure of the air surrounding the vacuum that tries to expand to fill the available volume. But the reason the atmosphere doesn’t just expand into space is because gravity holds it down.