Kids' Science Challenge #9 Challenge Question: As you know, the planet Earth is warmed by radiant heat that comes from our local star, the Sun. This knowledge might or might not help you to answer the following question: When you climb a mountain on Earth you are moving (very slightly) closer to the Sun; does the air temperature get warmer or colder as you climb higher and higher? Answer: COLDER The heat from the sun is radiant heat that does not warm up the air as it passes through the atmosphere to reach the surface of Earth. The Sun's rays warm up the surface of the Earth which in turn warms up the air that is in contact with the ground. The sides and top of a mountain also are warmed by the sun but the temperature there is already colder than at the foot of the mountain (because of a natural process called adiabatic cooling). Measurements have shown that air cools 5 degrees Fahrenheit for every 1000 feet that it rises (or 1 degree Celsius for every 100 meters). This has to do with a loss of heat as the air molecules move apart from each other at higher altitudes where gravity and air pressure are less than at ground level -- at "sea level" that is.