system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why it is hard to reach -273 Celsius but easy to reach 273?
gpt
You can't make cold, you can only move heat.

As you get colder, it gets increasingly difficult to remove heat because the removal process itself *must* generate heat and heat spontaneously flows towards cold regions.  As you approach -273, you're reaching the limit where you're removing every last joule of available heat from a system, and even the tiniest leak or inefficiency will pump heat back in.

Making heat is easy, you can get to 273C with any crude fire pit.