Which gas comprises the majority of the Earth's atmosphere today?

The majority of the Earth's atmosphere today is comprised of nitrogen. Nitrogen makes up approximately 78% of the atmosphere by volume, while oxygen, which is the second most abundant gas, accounts for about 21%. The other gases, such as carbon dioxide and hydrogen, are present in much smaller amounts.

Nitrogen is a relatively inert gas, which means it does not readily react with other substances, making it stable in the atmosphere. This stability is a significant factor in its abundance, as it does not easily undergo changes that would reduce its concentration. Understanding this composition is essential for comprehending various processes in the atmosphere and their impact on life and environmental systems.