Why do vacuums help insulate so well?



Wouldn’t it be the opposite? Because with nothing to impede the heat dissipation, wouldn’t it dissipate faster instead of slower?

In: Physics

Heat is energy, the energy needs matter to pass through, vacuumed remove to matter which I needed to pass energy along more efficiently, thus providing insulation.

There are a few ways that heat can be transferred from one place to another. By far the fastest is direct contact of materials in convection and conduction. Vacuums completely eliminate these.

Also worth noting is that insulating material doesn’t stop radiation any more than a vacuum does.

Edit: I just realized that the OP didn’t use the word radiation so I should explain what it means. Radiation is the process by which particles with a lot of heat energy turn some of that energy into photons which can travel through space and heat something else up. Radiation is the only way to transfer heat through a vacuum, and is much slower than direct contact of materials where photons aren’t needed at all.

Because heat is the measure of the average kinetic energy of the molecules in a substance.

The best way for them to lose that energy is to bump into something else and transfer it to that substance (so long as what it is bumping into has less energy). In space there is nothing for the molecules to bump into, so they can’t transfer the energy. The only other method they have to lose the energy is to radiate it away as light. This removes the energy at an extremely slower rate than physically bumping into something else.

Heat is basically the random kinetic energy of a substance. This is much more easily transferred if one substance can physically impact the other, compared to relying on electromagnetic emissions to carry it away.

Of the three forms of heat transfer, two require matter to transfer heat: conduction and convection. The last form, blackbody radiation/thermal radiation, transfers much more slowly, but happens independent of matter. So removing as much matter as possible between your heat source and sink significantly reduces the heat transfer that can occur.

When you get down to brass tacks, heat the measure of how fast molecules vibrate or move. Add heat energy to a thing and you make the molecules that compose that thing move faster. That’s what is actually happening.

Heat transfers by one molecule bouncing into another molecule. Just like a pool ball hitting another, one ball bounces off the other, slows down a bit equal to how much speed it imparts to the other ball that now starts moving. This is how heat transfers, “convection”.

If you have a bowl of cold water that’s a bowl of water molecules that are moving slowly. You also have a jug of hot water and that’s a jug of water molecules that are moving quickly. Add the jug to the bowl and the hot molecules bounce off the cold ones and impart part of their movement speed to the cold ones and the molecules start moving at the average speed of both, this is the heat equalizing.

A vacuum means there are no molecules there. If there are no molecules there, there’s nothing to bounce off. This means heat doesn’t transfer. Heat transfer is one molecule bouncing off another and averaging their speeds together, in a vacuum there are no molecules to bounce like this so heat doesn’t transfer.

Heat can be transferred in 3 ways: conduction (solid – to – solid contact), convection (circulation of air or liquid), and radiation.

Radiation is less effective than the other two methods for transferring heat. In using a vacuum thermos or by putting a vacuum between a hot object and a cold environment, the only way for the heat to escape is radiation.

Heat transfer through a vacuum is only possible through radiation which is the slowest and least effective mechanism for heat transfer.

Heat, conductivity etc. are all properties of matter whereas a vacuum by definition is the absence of matter