We stay warm enough by capturing energy from the Sun in a planet-wide greenhouse. This is possible because the greenhouse gasses let the sunshine through, but they hold on to the infrared energy coming back to space from the Earth. Let’s expand these statements.
A bit of theory goes a long way. Heat is total energy of all molecules in an object; more heat is more energy. Agitate water enough and it boils. Rub your hands together and they get warmer. The same is true on an atomic level – transfer of heat makes atoms more vigorous, literally.
You don’t need physical contact to make something warmer. God configured the nature in a way that all warm objects emit light, and that includes the Sun. Essentially light waves give energy to “compatible atoms and molecules. Light is like a wave in the ocean with atoms are ships in that ocean. Stronger waves bounce ships more vigorously, just like more intense light makes atoms move faster.
Heat is also exchanged by convection. In a fluid – air also qualifies as a fluid – warmer stuff move towards cooler stuff, and vice versa. This fantastic feature unlocks clouds and hot air balloons.
Life without the greenhouse
The Sun on average gives us (radiates) 340 Watts of energy per square meter, which is approximately how much power you need for a gaming computer. About a third of the sunshine is reflected right back to space. Icy and cloudy areas reflect sunlight better, water and bare rick reflect worse, but on average it’s 30%. The rest is absorbed into the earth, the earth gets warmer, and emits infrared light, because all warm objects emit light.
Remove the atmosphere and average temperature of the Earth drops from 14 to minus 18 degrees, which is about the same as in a freezer. NASA knows all of these energy flows better. What I know is that I wouldn’t like living in my freezer. It’s hard to imagine any life when everything is frozen solid.
Life with the greenhouse
Greenhouse gasses are quirky. As we already know, earth surfaces radiate (emit) infrared light (heat), and that light has various wavelengths. Some of those wavelengths resonate well with certain molecules, and make them bounce and spin. It’s not enough to bounce and spin to be called a greenhouse gas, though.
When a molecule bounced and spins, and wobbles asymmetrically, then it emits infrared light itself, and that light comes back to the surface and warms us to the nice and toasty 14 degrees C. Those wobbling molecules are the greenhouse gasses, and they do the heavy lifting.
That’s it!
Will update this post once and if I feel enough inspiration for this.