
A bicycle pump or other type of air pump warms up when the air is compressed.
A spray can or propane cylinder cools off when the gas inside it is released.
Plug the two together in a loop, put some coils on either side so that heat (or lack thereof) can be easily exchanged with the space, and you have a heat pump.
A heat pump doesn’t generate heat, it just moves it using the physics of pressure and state changes of a fluid (refrigerant). Moving heat in this manner uses less electrical energy than would be used generating heat from that electricity.
Heat pumps are very common. Refrigerators would be the most ubiquitous (heat pumped from inside to outside), but there are AC units, of course, and also clothes dryers and water heaters that are available.
A 30 year old friend of mine didn’t know about incognito mode. A certain subreddit popped up, on his projector screen, as a recommendation when we were searching for a sports stream to watch. I don’t think anyone else noticed or would really know what the sub was, but I later casually mentioned this really cool browser feature to use in case you need to search something weird.
I learned one shouldn’t assume that everyone is familiar with all the digital tricks to hide what they’d prefer others not see.