system
Given the following post, respond as if you're commenting on Reddit:
human
How does heat propagate in a vacuum if there are no particles for it to move through?
gpt
Mostly by radiation. There are some particles but the density is so low that conduction is extremely, extremely ineffective.

The reason the Earth is warm is because the Sun is shining on it. The Sun is particularly hot but it is no special case, anything with a temperature above absolute 0 radiates, and that radiation can travel freely through a vacuum. When that radiation is absorbed by something else then it heats up and that is how heat is transferred through space.