Waar komt het symbool ° vandaan die gebruikt wordt om graden weer te geven? Bijvoorbeeld 20 °C.

Het symbool is van oorspron een kleine nul:

"The first recorded modern use of the degree symbol in mathematics is from 1569[1] where the usage clearly shows that the symbol is a small raised zero, to match the symbols for minute, second, third, i.e. prime ′ (U+2032), double prime ″ (U+2033) and triple prime ‴ (U+2034), which originate as small raised Roman numerals for 1, 2, 3. Even finer subdivisions of degrees are also possible, though not common."