Heating and Cooling

We need heat for cooking, engines, extracting metals, and thermonuclear fusion. We need to make things cold for preserving food, making ice cream and constructing the superconducting magnets for hospital scanners. As we increase the temperature we go back towards the beginning of time when the universe was incredibly hot just after the Big Bang. As we lower the temperature we go forwards to the end of time when the universe will have run down and everything will be uniformly cold close to absolute zero.

Hospital scanner magnets use liquid Helium at about three degrees above the absolute zero of temperature. They need this low temperature to make the coils of the magnet superconducting. At superconducting temperatures the resistance of the coils becomes zero. The current can then be made be made very large in order to create the intense magnetic field needed.

Both heating and cooling require the transfer of energy and the more efficiently we can do this the better. Fuels to generate electrical energy and to heat are becoming more expensive and we have to start thinking carefully about the best way to keep things like food cool in our homes.