Here are 5 reasons why life as a human being is possible on Earth:
1. Atmospheric composition - Earth's atmosphere contains the right balance of gases like nitrogen, oxygen, and trace amounts of carbon dioxide and water vapor that make breathing and metabolism possible.
2. Temperature regulation - Factors like the greenhouse effect, ocean currents, and Earth's axial tilt help regulate temperatures within a range that allows liquid water to exist and biological processes to function properly.
3. Liquid water - The presence of abundant liquid water on Earth's surface and in its crust acts as a solvent for chemical reactions and provides a medium for transporting nutrients and waste products in living organisms.
4. Protection from radiation - Earth's magnetic field