MCQ Detailed View

The Earth is surrounded by a layer of gases called the atmosphere. This layer contains nitrogen, oxygen, carbon dioxide, argon, and other gases. A natural question is: why does this atmosphere stay with the Earth instead of drifting away into space? The answer is the force of gravity. Gravity is the fundamental force that attracts every object with mass towards the center of the Earth. Because gases also have mass, gravity pulls the molecules of the atmosphere and keeps them bound to the planet.

The strength of gravity depends on the mass of the planet and the distance from its center. Earth has enough mass to generate strong gravitational attraction. This pull prevents atmospheric gases from escaping into outer space. Without gravity, Earth would not be able to hold on to its air, and life as we know it could not exist.

Pressure of the planet is not responsible for holding the atmosphere. Pressure results from the weight of air molecules being pulled down by gravity, not the other way around. Similarly, the electric charge of the planet does not have a significant role in keeping the atmosphere attached. Heat of the planet also does not hold gases; in fact, too much heat can give gas molecules enough energy to escape Earth’s pull. For example, smaller planets with weaker gravity, such as Mercury, cannot retain a thick atmosphere because gases escape more easily when heated by the Sun.

Therefore, gravity is the only correct explanation. It acts continuously, balancing against the motion of gas molecules, and ensures that Earth retains the protective blanket of air necessary for weather, climate, and breathing.