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
Let me start at the beginning. The sun is very hot. Objects at all temperatures emit electromagnetic radiation also known as light. This is called black boy radiation. The peak energy or color of this light depends on the temperature of the object. The sun is hot enough to emit what we call visible light. That light travels through space to reach Earth.
Our atmosphere is made of many gases that absorb specific wavelengths/energies/colors of light. These gases mostly allow visible light through (like from the sun) but absorb lower energy light we call infrared. Some still gets out but you can think of these gases as allowing heat in but not out, like a greenhouse.
The Earth is also relatively warm. It emits light but at much lower energies/colors in the infrared range. The earth is warm because of the light that hits it from the sun. All the energy that reaches the earth is eventually radiated back into space in all directions. Otherwise, Earth would heat up a lot and very quickly.
The light leaving earth is infrared which is partially blocked and prevented from leaving by the gases in our atmosphere. Earth will heat up as it retains heat and emits more and more light until enough emitted light energy leaves through the atmosphere as what comes in from the sun. This is the stable temperature.
To your questions:
1) yes
2a) space does not heat up because heat is something that objects aka matter have. the definition of space is basically a place that (mostly) lacks matter. It therefore cannot be hot.
2b) The few particles in space do not heat up to infinity for the same reason that the earth does not, they emit black body radiation. eventually they reach a stable “temperature”
3) the photons that makeup sunlight can be considered particles and they do indeed heat up a surface when it is hit and absorbs them.
4a) Thermal energy does escape into space as radiation as explained in my paragraphs above.
4b) Earth and space do not balance out for the same reason that your warm house and the cold air outside in winter do not balance out. Earth (like your house) is constantly being heated and there is insulation to prevent this heat from leaving until a particular temperature is reached. Also, the cold receiving end is so much larger than the warm end that you wouldn’t notice any change there.
I hope that answered everything.
Latest Answers