How does the Earth and its various spheres lose heat?
This has stumped me since high school physics. I have an elementary understanding of how my coffee cup for radiates heat. However, I’ve always imagined that the vacuum of space would insulate the planet, or anything, like an invisible Yeti cup.
So, where does the heat go, and how does it get there?
In: 0
The Earth, like all objects, emits light based on its temperature. This radiation, called [thermal radiation](https://en.wikipedia.org/wiki/Thermal_radiation), is what makes the Sun glow white, hot metal glow red, or your body glow in the infrared. At Earth’s typical temperatures, the glow is mostly in the infrared.
Since the light emitted contains energy, emitting it tends to cool an object.
You’re correct that the vacuum of space acts as an excellent insulator at Earth-like temperatures. At Earth’s temperature, conduction (warm and cold objects in contact with one another exchanging heat) and convection (movement of fluids based on temperature differences) are much more efficient ways to transfer heat than radiation is. But radiation still matters, and it’s the means by which the Earth releases heat into space.
At higher temperatures, radiation – which scales up faster than the other forms of heat transfer – is more efficient. For example, a fire in a fireplace heats the room mostly by radiation, which is why it warms the room even though the air it’s heating up escapes up the chimney (i.e., it cannot transmit its heat by convection or, mostly, by conduction). It’s also why the Sun can heat Earth efficiently: the Sun is much hotter than Earth and therefore radiates much more efficiently.
Latest Answers