alt Hacker NewsI was just thinking about this earlier today when washing my hands in the sink.
When you first turn on the hot water tap in most homes, the water that comes out is cold. After some period of time, hotter water starts to come out. My mom used to describe this as "waiting for the water to warm up".
For decades, I didn't consider the mechanism behind this. That is that there is water in the pipes between the home water heater and the tap. That water can't retain its heat without any further heat input, and gradually loses heat and comes into near-equilibrium with the temperature of the rest of the house. The hot water inside the water heater tank, on the other hand, is constantly being reheated as necessary by a heating element.
When you turn on the tap, after not having used it for some time, you're waiting for cold water from the pipes to be flushed out through the tap and be replaced with freshly heated water from the tank. Once this happens, the water coming out of the tap will be hot because it's been heated recently enough.
I probably didn't realize this until I was about 30 years old, and then I thought of Feynman's anecdote of his students not connecting their theoretical knowledge to understand the mechanism of a real physical situation. It seems I wasn't curious enough as a child to apply my own knowledge to the mechanism of the hot water tap!
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Weirdly enough, this is not the case in the former Soviet Union. Because there's always a reverse pipe ("obratka") that has hot water constantly circulate and the only part that cools down is the small portion of pipe between "obratka" connection and the faucet, so "heating up" takes a second tops.
It's puzzling why no one in the civilised world adopted this idea :/
Many things are told about emigres being constantly homesick etc., and i believe this is largely bullshit, but this is the only thing i really miss from my Soviet past.
One of the best ways to learn to think Scientifically i.e. in terms of Physics/Chemistry/Mathematics/Biology is to start with the classic Soviet era books by Yakov Perelman - https://mirtitles.org/?s=yakov+perelman
Specifically; start with the 2-vol Physics for Entertainment (the breadth of coverage is really good) followed by Mathematics can be Fun, Algebra can be Fun etc.
Note: Do not be misled by the words "Entertainment"/"Fun" etc. in the title. As is typical of Soviet era books these are serious works with precise, succinct and focused topics quite unlike most current "pop science" books.