If the Van Allen Radiation Belt reaches temperatures of 35,000C, How is it possible to go through them when the craft has a boiling point of 4000C? [closed]

Question

Van Allen Radiation Belt = 35,000C

Boiling point of carbon fiber = 4200C

Boiling point of Aluminum = 2470C

Answer 1

Temperature is only a measure of how fast the particles are vibrating, but on its own, it doesn't tell us much about how much heat energy there is in the environment. The density, heat capacity, and heat transfer matter a lot!

Some materials have a high heat capacity, meaning you have to dump a lot of energy into it to raise its temperature, but that means it stays at that temperature very effectively too -- water has an incredibly high heat capacity, which means you have to dump a ton of energy in to get it hot, but then it'll stay there pretty effectively, which is why it's useful for cooking. Heat capacity is sometimes called thermal inertia because it acts like physical inertia does with movement. Heating up a tank of water is like getting a semi truck moving, slow to start but unstoppable, where something like aluminum or copper is more like a motorcycle.

As an example of how this works in normal life, you can easily stick your arm in an oven where the air is at 400 F without harm (provided you don't touch anything but air), but water that's nearly 200 degrees cooler is still more than capable of seriously burning you. The water is much more dense and contains a lot more heat energy than the air does.

In part, heat capacity is determined by the substance itself (some molecules can simply contain more heat energy than others), but density plays a big part in it too. Heat capacity is partially informed by simply how many particles are packed into the space. Of course a million atoms at 10,000 degrees contain a lot more energy than two atoms at the same temperature. That's part of what gives ambient air such a low heat capacity: there's fewer particles in a volume of air than the same volume of liquid or solid.

And that's largely what's going on in space. The Van Allen belts or other areas in space may reach enormous temperatures if you examine how fast the particles are vibrating, but if there's only a handful of particles per cubic meter, there's barely any energy there to transfer into your spacecraft. It's kind of the heat equivalent of having gold dust sprinkled on your head -- gold is very dense, very heavy, so how can you possibly survive? Well, there's not enough of it to hurt you, there's hardly any mass there to hit you.

Technically, that low density is how those particles can reach such insane temperatures. One of the reasons it won't happen on Earth is because a particle that gets so ridiculously hot will immediately bounce off other particles around it and give up most of that heat, spreading it out. In space, where there's pretty much nothing for a particle to bounce off of, the interactions that generate those high temperatures can continue to happen without the energy getting bled off into a larger mass of air.