Episode Details

It doesn't know anything. It just blocks every road heat can travel, and there turn out to be two kinds of road: one you can block by taking stuff away, and one that doesn't need any stuff at all.

The flask is a heat-blocking checklist. The vacuum stops the two particle routes, and the shiny walls fight the route that needs no particles. That is why it works both ways: it doesn't care which direction the heat is going.

Sources:

• https://en.wikipedia.org/wiki/Vacuum_flask
• https://www.scienceabc.com/innovation/thermos-flask-keep-hot-things-hot-cold-things-cold
• https://www.docbrown.info/ephysics/wavesaaer-3.htm
• https://en.wikipedia.org/wiki/Leslie_cube

Source: Episode 15 - Physics Level 8, Heat on the Move (15/17)
Style: Exam prep
Length: 978 words, 6 min target
Generated: 2026-10-25