[poseid]

thanks, i see... i read about travels to Egypt, and then curiosity on heat transport. back in that time, heat was understood differently than today, but interesting to see how the fluctuations in temperature of day/night of month/year follow a bit of sinusoidal pattern indeed. do you recall what those basic heat equations were back in that time, and why it was different from theories back then? just in case you have some more time to write on this.... thanks!

[yorwba]

The Wikipedia article on the heat equation has a section on using Fourier series: https://en.wikipedia.org/wiki/Heat_equation#Solving_the_heat...

I assume that except for the adaptation to modern notation, the general idea of the argument has been preserved.

Note that sinusoids are only used because they make the calculations convenient, and not because of the day/night cycle or actual sinusoidal heat distributions empirically observed in nature.