It takes energy to forget
Information theory has maintained that it does not necessarily take energy to create information, but it takes energy to delete it. This article at Science News.
According to the article, the discovery confirms a 1961 prediction by IBM physicist Rolf Landauer. It links information and heat flow in ways that keep the universe from breaking the second law of thermodynamics. Landauer was investigating Maxwell’s thought experiment about a “demon” who, according to Maxwell:
… if we conceive of a being whose faculties are so sharpened that he can follow every molecule in its course, such a being, whose attributes are as essentially finite as our own, would be able to do what is impossible to us. For we have seen that molecules in a vessel full of air at uniform temperature are moving with velocities by no means uniform, though the mean velocity of any great number of them, arbitrarily selected, is almost exactly uniform. Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the slower molecules to pass from B to A. He will thus, without expenditure of work, raise the temperature of B and lower that of A, in contradiction to the second law of thermodynamics….
Landauer calculated that erasing a bit of information always releases at least a tiny amount of heat — no less than 3 billionths of a trillionth of a joule (at room temperature).