Name the force which is holding the atmosphere to the earth.

Gravity:

1. It is defined as that force by which a planet or other body draws objects toward its centre.
2. The force of gravity keeps every planet in orbit around the sun.
3. The acceleration of gravity on earth at sea level is $9.8\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s^2$}\right.$
4. We humans and other objects will become weightless without gravity.
5. If we have no gravity force, the atmosphere would soon disappear into space, the moon would collide with the earth, the earth would stop rotating, etc.

Thus, Gravity holds down our atmosphere and the air we need to breathe and keeps it from drifting into space.