Einstein's Fridge: How the Difference Between Hot and Cold Explains the Universe

by Paul Sen

Tyndall discovered something quite extraordinary. Infrared radiation was barely affected by nitrogen and oxygen, the gases that make up 99 percent of the atmosphere. But when the same radiation passed through air containing water vapor or carbon dioxide, even though these gases are present in tiny amounts, the thermometer registered a fall in the temperature reading. The only explanation, argued Tyndall, was that the presence of these gases increases the air’s ability to absorb infrared radiation by a factor of about fifteen. Tyndall had discovered what we now call the greenhouse effect. Water vapor and carbon dioxide in our atmosphere trap some of the sun’s energy. Effectively, they provide a warming blanket around our planet. Without these gases in our atmosphere, the earth’s temperature would plummet and would be well below zero even at the equator.