What is perpetual motion? – The Hindu

What is perpetual motion? – The Hindu


A sinking bird toy, December 28, 2011.

A sinking bird toy, December 28, 2011. | Photo credit: Robinlecester (CC BY-SA 3.0)

Nothing lasts forever. This is good advice for life, and it's also an important feature of our physical universe.

Natural philosophers considered and rejected the idea of ​​'perpetual motion' a long time ago. The basic premise of perpetual motion is that it should be possible for a system to operate without a power supply. We know from daily experience that this cannot be true: for example, the battery on your phone will drain to zero when you use it without charging it.

In the language of physicists, perpetual motion violates the law of conservation of energy. The first and second laws of thermodynamics also dictate that anything that provides power must also release heat. If there were an infinite power supply, there should also be an infinite heat release. Not so.

But this simple explanation has not stopped some people from wondering whether perpetual motion machines could exist.

A simple example of this is the dunking bird toy. It moves forward and backward using the temperature difference between the top and bottom of the bird. In very simple terms, as it moves forward, its beak sinks into a glass of water that flows underneath the bird, and the weight causes the bird to move backward.

This drowning bird toy can work like this for a long time, but it cannot go on forever: it will stop when the temperature difference between the top and bottom of the bird is over.

Karthik Vinod is a Trainee Hindu,


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