Several different sources online state that the average temperature of interstellar space (or the universe in general) is around 2-3K.
I learned that temperature is basically the wiggling of matter, and I find it somewhat counterintuitive that the wiggling of so few particles can cause a temperature of 2-3K. Is there a (order-of-magnitude) calculation which can show that this average temperature estimation is correct, using an estimation of the average density of interstellar space (or the universe in general)?
Answer
Temperature in a gas is the average kinetic energy per particle. As an intrinsic property its value is entirely decoupled from how much stuff has the property. Whether there are 100 particles per cubic centimeter or only 1 particle per cubic meter, the temperature can be anything.
The coldest parts of the ISM are about 3 K, and getting colder than this is difficult, because the entire universe is bathed in a sea of 3 K photons. But some parts of the ISM are much, much hotter. The diffuse gas filling the space between galaxies in galaxy clusters can be hundreds of millions of degrees. This just means each particle is whizzing about very fast.
No comments:
Post a Comment