I have a plethora of questions regarding thermodynamics and all of them came to my mind while I was thinking about how the greenhouse effect actually works. (hence the title)
The sun emits radiation, which after 8 minutes hits the surfaces on planet earth. Here this radiation is reflected OR absorbed and turned into thermal energy.
Now from my understanding, thermal energy is kinetic energy on the particle level. For this form of energy to be transferred or absorbed, the particles would have to hit less energetic particles and thus energize them, which then would make them “warm” right?
Assuming that my explanation is mostly correct, why does space around us not heat up? By that logic, the particles in an imperfect vacuum would have to be highly energetic because of constant unshielded exposure to the light of millions of stars.
Would that also mean that sunlight consists of extremely fast particles that energize surfaces when they hit them? (If not, how does sunlight energize particles.
Why exactly does the thermal energy not just escape into space? Earth seems to be more energetic than space around us. Normally two asymmetric thermodynamic systems would balance out.
Sorry if I’m way off. I’m merely an ignorant student.
In: Physics
The phenomena you are missing is called black body radiation. The particles that transport electromagnetic radiation is called photons and does not have any mass. So they can be created or destroyed as needed. When you have particles that have thermal energy they sometimes spontaniously create such a photon and give it energy. So hot things emit light. The frequency and intensity of this light depends on the temperature. Colder things only emit a small amount of infrared radiation but hotter things emit more radiation and starts to glow red. The hotter an object is the color changes from red to yellow to white and then mostly ultraviolet. The surface of the Sun is in the last category so the Earth gets radiated with lots of ultraviolet light from the Sun which does heat up the Earth as it absorbs the energy. However even though it is relatively cold on Earth the surface still emits black body radiation, but in the infrared spectrum. Because the Sun is so far away and appears so small in the sky we only get a tiny bit of its radiation. However the Earth emits a great bit of radiation in all directions. The temperature have equalized such that the Earth emits just as much radiation as we absorb from the Sun and thereby maintaining a constant temperature.
The issue with the greenhouse effect is that carbon dioxide absorbs infrared radiation but not ultraviolet or visible radiation. So the light comming inn from the Sun goes straigh through the carbon dioxide in our atmosphere and heats up the surface of the Earth. However the radiation from the surface of the Earth is infrared and will therefore be absorbed by the cabon dioxide in our atmosphere. And thus the Earth receives more energy from the Sun then we emit and the temparatures increase.
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