The conversation between human and AI assistant.
If perpetual motion machines don't exist, what's this?
Well, there are some machines that claim to have perpetual motion, even though it violates the laws of thermodynamics.
Ah, I understand now. Those machines are often classified as either perpetual motion machines of the first kind, which violate the first law of thermodynamics, or perpetual motion machines of the second kind, which violate the second law of thermodynamics.