Answer:
Explanation:
First of all, we need to understand what gravity is. Gravity in its simplest form can be best visualized as a force of attraction, that pulls all objects that have a mass towards itself.
It is usually exerted by an object with a larger mass and felt by objects with smaller masses.
Putting this into context, the earth exerts a gravitational pull on all substances with masses, which are around it. This includes the oceans, birds, airplanes, clouds, and even gasses in the atmosphere. The atmospheric gasses may be light enough to float, but they can't go very far, since gravity is constantly tugging at them. This keeps the gasses that make up our atmosphere, within a reasonable radius, which is very close to the earth. In a nutshell, gravity prevents them from floating away into outer space.
