# When sailboats sail faster than the wind, why are they not violating the 2nd Law of thermo?

There is a related question here, but it doesn't explain the implications of / on the 2nd Law of Thermo.

One of the effects of the 2nd Law of Thermo is that no matter how many zillion particles travel with a velocity of X they cannot collaborate together to propel even one tiny particle one tiny bit faster than X. So how can air molecules traveling at e.g. 18mph push a sailboat 20mph?

• The thermodynamics system that powers the sailboat is the sun-Earth-space thermal gradient. Since the sun's temperature is approx. 5800K and the temperature of space is 2.7K, the resulting Carnot efficiency is approx. 99.95%. Do you have examples of sailboats exceeding that efficiency limit? Mar 10, 2016 at 6:21
• @Curious. The sailboat and the wind comprise an an isolated system for this question unless you're telling me that some energy other than the wind is propelling the sailboat. Mar 10, 2016 at 13:25
• "The sailboat and the wind comprise an an isolated system for this question [...] " No. They don't. The wind is maintained by contact (energy input) with the wider environment so the system is not isolated. Mar 10, 2016 at 16:41
• @JoeC, the energy available to the sailboat comes from the speed difference between the wind and the water. The keel and the sail work together to extract that energy. Mar 10, 2016 at 16:52
• You can always beat thermodynamics by choosing non-physical system boundaries. That, of course, is not something that mother nature actually cares about. She "knows" where the real thermal baths are. Mar 10, 2016 at 23:20