Heat Is the Hardest Energy to Tame

You can turn motion into heat very easily. But turning heat back into useful work faces strict limits, especially in repeating machines like engines.

Why Heat Limits Machines and the Universe

Why Perfect Engines Do Not Exist

In real heat engines, some energy must leave as waste heat. That limit comes from the second law of thermodynamics, not just from bad engineering.

Why Heat Limits Machines and the Universe