Attempts to invent a perpetual motion machine began in ancient times. Researchers and inventors of all stripes have tried to create a mechanism that works without an external source of energy. Centuries passed, Leibniz discovered the law of conservation of energy as early as 1686, however, attempts are still being made to create a perpetuum mobile (lat.). There are so many projects from home-grown inventors that the US Patent Office has not issued patents for them for over a hundred years.
However, some projects are not devoid of elegance and may well work, seemingly without energy consumption. One of them is the "drinking duck" or "Hottabych bird".
How it works
A thin glass cone with a horizontal axis in the middle is soldered into a small container. The free end of the cone almost touches its bottom. A little ether is poured into the lower part of the toy, and the upper, empty, is pasted over from the outside with a thin layer of cotton wool. A glass of water is placed in front of the toy and tilted, forcing it to “drink”. The bird begins to bend over two or three times a minute and dip the head into the glass. Time after time, continuously, day and night, the bird bows until the glass runs out of water.
Why is it not a perpetual motion machine
The head and beak of the bird are covered with cotton wool. When the bird "drinks water", the cotton wool is soaked in water. When the water evaporates, the temperature of the bird's head decreases. Ether is poured into the lower part of the bird's body, above which there are ether vapors (the air is pumped out). As the bird's head cools, the vapor pressure in the upper part decreases. But the pressure at the bottom remains the same. Excessive ether vapor pressure in the lower part raises the liquid ether up the tube, the bird's head becomes heavy and bends towards the glass.
As soon as the liquid ether reaches the end of the tube, vapors of warm ether from the lower part will enter the upper one, the vapor pressure will equalize and the liquid ether will flow down, and the bird will again raise its beak, while capturing water from the glass. The evaporation of water begins again, the head cools down and everything repeats. If the water did not evaporate, the bird would not move. To evaporate from the surrounding space, energy is consumed (concentrated in the water and the surrounding air).
A "real" perpetual motion machine should work without the expenditure of external energy. Therefore, the bird of Hottabych is not really a perpetual motion machine.