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
Light impacting the surface does indeed create kinetic energy. But the material affected doesn’t just sit there being warm. That material conducts heat to everything it touches and radiates some of it in the form of deep infrared light.
The atmosphere is not perfectly transparent and absorbs different wavelengths of light to varying degrees. Small molecules like oxygen (O2) and nitrogen allow most long wavelengths pass. But larger molecules, such as carbon dioxide, methane and water vapour catch and absorb more of the light’s energy, especially at low wave lengths.
The result works much like the glass in a greenhouse (hence the name). The atmosphere intercepts very little visible light and a little bit of the infrared. The remaining light eventually hits the surface. Some is reflected while some is absorbed and then radiated away as heat. Some of that heat/infrared is able to escape Earth again. How much escapes and how much gets caught by the atmosphere depends on the abundance of greenhouse gases. More CO2 means more heat gets caught while incoming and more gets caught on its way out.
To make matters worse, that world wide increase in average temperature also means more water evaporating from the oceans, making the air warmer, more humid and even better at trapping radiated heat. Warmer oceans also means the release of more methane from undersea clathrate deposits. Small changes in the levels of one greenhouse gas increases the levels of other greenhouse gases. It’s a positive feedback loop.
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