Final answer:
Air density, also referred to as air thickness, is determined by the weight of air in a cubic meter and decreases with increasing altitude.
Step-by-step explanation:
Air density, also known as air thickness, is measured by the weight of the air in a cubic meter of space. Air density is heaviest at ground level and decreases as altitude increases. For instance, a cubic meter of air at sea level weighs about 1.29 kg, but the same volume of air at the top of Mount Everest, approximately 8,828 meters high, would weigh only 0.023 kilograms. The decrease in air density with altitude is why mountain climbers often need oxygen tanks to reach high peaks.