Good morning. Today is primidi, the 11th of Frimaire, Year CCXXXI. We celebrate la cire, an organic substance that handles heat and moisture beautifully.
Lava lamps don't really have lava in them, of course. If you buy a new one, what's floating around in there is a not-so-carefully guarded secret (it's ferromagnetic fluid), but the original invention from way back in CLXXI (1963) contained a wax compound suspended in oily water.
But the thermodynamics of the wax inside – it loses density when encountering the heat lamp at the bottom, causing it to rise, then cools at the top, causing it to sink – pale in comparison to the stories of those who have manufactured these perennial den ornaments.