Subzero temperatures don't pose a problem for heat pumps. The refrigerants used in the heat exchanger, which transfers heat from outside a building to inside, have an extremely low boiling point below minus 40 C. That means even when it's very cold, a heat pump can absorb ambient heat from the outside air and use it to warm a building.
In terms of making things happen, energy is an indispensable consideration. Systems spontaneously tend towards the lowest-energy state. When a system reaches equilibrium, no further energy can be extracted. That maximum entropy, lowest energy state is the inevitable end-state of the Universe. But until that moment arrives, reactions of all kinds will occur, continuing to liberate energy. In our bodies, chemical bonds break and reform: releasing energy.
Current energy prices, including the rising cost of electricity, mean that homeowners may experience higher heating bills by replacing their current heating systems with heat pumps-at least in some regions of the country. Heat pumps, which use electricity to move heat from the outside in, are used in only 14% of U.S. households. They are common primarily in warm southern states such as Florida where winter heating needs are relatively low.
I don't know who invented this crazy challenge, but the idea is to put someone in a carved-out ice bowl and see if they can get out. Check it out! The bowl is shaped like the inside of a sphere, so the higher up the sides you go, the steeper it gets. If you think an icy sidewalk is slippery, try going uphill on an icy sidewalk. What do you do when faced with a problem like this? You build a physics model, of course.