Earth is surrounded by thick layer of gases, called the atmosphere. These gases protect Earth from the Sun’s rays, keeping temperatures on our planet at a comfortable level. Earth’s atmosphere is divided into a number of distinct layers. At the outer edge of the atmosphere, there is no clear boundary. It just fades into space.
Earth’s atmosphere is about 300 miles (480 kilometers) thick, but most of it is within 10 miles (16 km) the surface. Air pressure decreases with altitude. At sea level, air pressure is about 14.7 pounds per square inch (1 kilogram per square centimeter). At 10,000 feet (3 km), the air pressure is 10 pounds per square inch (0.7 kg per square cm). There is also less oxygen to breathe.
Picture Credit: Google