Liquidrage

The cosmic microwave background has a temperature of 2.73 Kelvin
These are the leftover photons from the Big Bang.

For when you ask about the Big Bang I'll respond a quantum vacuum. Going beyond that gets a little sketchy.

Christopher Lord

Heat in general is just particles in motion. electromagnetic 'heat' is just an energy source for excitation, excitation causes motion, which is heat. This is how a microwave works, and its why you feel warm in the sun and cool in a shadow. nothing more than photons bumping into atoms.

So 'Where does heat come from' translates directly into 'where does motion come from'. The two terms are exactly equal.

could you rebase your question with this knowledge, since surely your not asking such a general question as 'where does motion come from'

Starspun

I found this while checking out gravitational forces during galaxy formation:

<a href="http://www.damtp.cam.ac.uk/user/gr/public/cmbr_temp.html" target="_blank">http://www.damtp.cam.ac.uk/user/gr/public/cmbr_temp.html</a>


Measurements of the cosmic microwave background radiation allow us to determine the temperature of the universe today. The brightness of the relic radiation is measured as a function of the radio frequency. To an excellent approximation it is described by a thermal of blackbody distribution with a temperature of T=2.735 degrees above absolute zero. This is a dramatic and direct confirmation of one of the predictions of the Hot Big Bang model.

The COBE satellite measured the spectrum of the cosmic microwave background in 1990, showing remarkable agreement between theory and experiment. The diagram below shows the results plotted in waves per centimeter versus intensity. The theoretical best fit curve (the solid line) is indistinguishable from the experimental data points (the point-size is greater than the experimental errors).

ishalon

"By what mechanism has heat been generated in the Universe?"

ishalon

Yes but it has to melt again doesn't it?

ishalon

I wasn't, but don't you think that by explaining how motion creates heat, you have explained where heat comes from? I do.

But you also made me wonder why some light doesn't create heat; although just from thinking about it i guess its because it does but just not a significant amount.

Christopher Lord

Motion is heat. Motion does not cause heat.

Heat is the sensation of atoms bouncing against the atoms in your heat-sensitive nerve cells.


The reason some light causes more heat than others (IE: Infrared vs. blue visible) is that certain wavelengths of light are well-sized to excite certain atoms.

For example, Microwaves are well-sized to bounce water molicules around, but pass right through things made of other materials without causing heat.

Well-modulated light can even cause cooling, by pulsing the beam at the inverse rate the atoms are vibrating. Experiments involving Bose-Einstein condensate are cooled this way.

Coragyps

Nope. The Earth is slowly (very damn slowly!) cooling, and the solid core is growing. Another few billion years and the core and mantle will all be solid, with no significant magnetic field. Mars is to that state now.

tronvillain

ishalon:
No. Eventually the core will solidify.

ishalon

thank you