In 1912, Charles Steinmetz published an article in the General Electric Review titled "The Second Law of Thermodynamics and the 'Death' of Energy, with Notes on the Thermodynamics of the Atmosphere." In the article, Steinmetz outlined a very simple argument against the second law of thermodynamics.
The second law of thermodynamics states that without expenditure of some other form of energy, heat only flows from higher to lower temperature. Steinmetz offers a counter-example: the Earth's atmosphere. In order to reach escape velocity from the Earth's gravity, the velocity of a molecule would have to be 11,000 m/s or 60,000 °C. Steinmetz explains that "by the escape of these molecules heat energy flows from the temperature of the earth, 10 °C., into a temperature of 60,000 °C."
Crookes' vacuum tubes are another example of a system that appears to break the laws of thermodynamics. The rarefied molecules within a vacuum tube behave as individual particles rather than as a gas obeying the laws of thermodynamics. Specifically for this reason, Crookes proposed treating rarefied gas as a fourth state of matter.
To summarize the argument:
In order for the second law of thermodynamics to be universally true, without expenditure of some other form of energy, heat must only flow from higher to lower temperature.
In a gravitational field, as well as in a vacuum tube, heat (kinetic energy of particles) can flow from a region of lower temperature to higher temperature without an external expenditure of energy.
Therefore, the second law of thermodynamics is not universally true.
Unless gravity can be interpreted as an expenditure of energy, the second law of thermodynamics appears to be flawed, not only on the scale of individual particles, but also on a cosmic scale.