✔ 最佳答案
In the old day, people do use Fahrenheit (F) as unit of temperature, later they need to use a new scale, so they use the freezing point and boiling point of water as the reference, that is 0 and 100 degree Celsius (C).
Please remind that the freezing point and boiling point of water is pressure dependent, that is for a higher pressure, the freezing point and boiling point of water will be higher, and vice the verse.
The new standard is using the triple point of the water as the reference, for more information, go to search in web or wiki for the phase diagram of water. The triple point is the equilibrium of 3 phases of water, the gases (vapour), liquid (water) and solid (ice).
