I understand that the sun gives energy primarily in the form of sunlight, which contains various wavelengths of electromagnetic radiation. If the earth absorbs some of the energy, does the earth’s “total energy” accumulate?
In: Planetary Science
Yes, the earth does accumulate the solar energy that hits the earth.
But also yes, the earth does lose some energy to space. It does not reflect ALL the sunlight back into space. But it does reflect some of the light that hits it back into space. And it also does lose some energy to space in the form of radiation. With “black body” heat radiation radiate off the planet
I think it accumulates because I’m pretty sure that is the whole premise behind global warming due to GHGs.
It eventually loses all heat, but not all by reflection. Some heat is absorbed, and then eventually radiated into space, though that rate of radiation is dropping due to the presence of greenhouse gases trapping heat.
Toward the end of the sun’s life, the input energy will become so great that the planet is destroyed by it (probably by being swallowed by it) and then whether or not that counts as losing that heat (as opposed to accumulating it) is just a semantic consideration
Earth reflects part of the energy through ice and clouds and warms up through the remaining energy that it receives from the Sun. This heat is then again emitted as infrared light, because the received energy is distributed over a large volume, so the energy density is not high enough to emit visible light.
The ratio of light that something reflects vs absorbs is called its “albedo.” An albedo of 1 means it is 100% reflective, an albedo of 0 means it absorbs 100%. For visible light, lighter colored things have a higher albedo – that is what it means for something to be lighter colored.
The albedo of the Earth overall is about 0.3, which means it absorbs about 70% of sunlight and reflects about 30%.
However, that solar energy that is absorbed doesn’t stay here. It is re-emitted back into space. The energy that the Earth emits is *almost exactly* the same as the energy that it absorbs. When these two are even very very slightly out of balance, the temperature of the Earth changes. Which is why for example having a bit too much carbon dioxide in the atmosphere causes global warming, because it very slightly reduces the energy that escapes.
If the Earth were in equilibrium, the energy radiated into space would equal the energy received. However, the Earth is significantly out of balance, sending less energy into space than is received. The extra energy accumulates as heat in the land, air, and especially the oceans.
[https://mynasadata.larc.nasa.gov/basic-page/earths-energy-budget](https://mynasadata.larc.nasa.gov/basic-page/earths-energy-budget)
most of the energy is radiated away as heat, but more is comming in than leaving, hence why the earth is warming.
all forms of energy on earth eventualy dissapate as heat and radiate away, there is no magically accumulaying thing like you are thinking with waves/wind
(Almost*) All of the energy the earth receives is eventually radiated away. There has to be an equilibrium, else the planet will heat up or cool down until there is an equilibrium again.
*Of course, a small, small portion of the energy gets captured as chemical energy by photosynthesis and stored as plant and animal matter gets buried under sediments, but that amount is negligible compared to the total insolation.
Also with the current greenhouse gas crisis, Earth is radiating less than it receives and is heating up. But if we ever stop releasing CO2, the Earth will eventually reach an equilibrium again, as the hotter something is, the more energy it radiates.
there was a veritasium video about this that i would love to link to you, but somehow i’m not finding it.
no, the earth doesn’t accumulate energy from the sun. all the energy that the sun provides is eventually radiated back into space. if that wasn’t the case, than you can imagine that the earth would gradually become hotter and hotter, and by now would have probably evaporated.
this doesn’t mean that all the energy is reflected immediatly. as someone else said, some is reflected, and some is absorbed, the ratio betweeen those being the albedo. earth’s albedo is around 0.3, so it absorves around 70% of the light that hits it. but the energy that this light carries is then radiated away, in the form of infrared radiation, back into space.
it’s what happens between the absorbion of the energy from the sun by the earth and it being radiated back into space that is interesting. this is the energy that plants use, by converting water and CO2, into their mass, that later animals eat, that later die and are decomposed by microbes, and so on. it is also the energy that powers our climate, driving winds, creating rain, etc. what the sun provides to the earth, rather than just “energy”, as that would mean that the earth would get ever-increasing hotter, is “usable energy”, or in other words, entropy.
if you imagine the earth as a closed system, with the same amount of energy as the earth currently has, being provided from the sun, eventually all this energy would spread evenly, and there wouldn’t be no source to power anything (powering something means having energy flow through it; having a source of energy means that somewhere the energy is more concentrated, so it may flow somewhere, powering it). what the sun does is provide a source of concentrated energy, that then is able to flow around the earth, powering our climate and the biosphere.
Yes and no. The sun gives light/radiation. It’s not like a bonfire in which the space around it is hot – because heat/cold are a product of the movement of molecules.
However, infrared radiation *does* heat up molecules, and we got plenty of those on Earth. Our atmosphere captures a good amount of it – probably too much nowadays due to humans churning out greenhouse gasses like no one’s business.
But an essential function of energy reflection makes life on the surface of earth possible: our magnetic field reflects a bunch of harmful radiation from the sun. We can see this in auroras (Northern Lights). The ozone layer of our atmosphers also reflects (mainly) ultraviolet radiation, hence our international effort to ban things like CFC’s (common in refrigerants).
We should also take into account that we have a bunch of organisms such as plants, algae, etc. That photosynthesize, meaning they convert sunlight into energy. This energy, in turn, is consumed by herbivores, then those herbivores get consumed by carnivores (of course, there’s a loss in energy the higher up the food chain you go) but the point is that the sun fuels surface life.
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