In 1867 HTD (Historical Terran Dating), Terran physicist James Clerk Maxwell articulated a thought experiment that described a whimsical method of violating the Second Law of Thermodynamics. In this thought experiment, an imaginary container was divided into two parts by an insulated wall. In the wall was a door that could be opened and closed by a “finite being.” This “finite being” would only allow “hot” (fast) molecules to pass through the door to one side of the wall, and would only allow “cold” (slow) molecules to pass through the door to the other side of the wall. The end result would be that the container on one side of the wall would always be hot, and the container on the other side would always be cold.
Under the Second Law of Thermodynamics, the expected result would be that there would be an equal number of “hot” and “cold” molecules on both sides of the container. “Maxwell’s Demon,” as the “finite being” eventually came to be called, actively prevented this by forcing hot and cold molecules to remain on specific sides of the wall.
Eventually, someone came up with a way to project a field that would block specific types of molecules from passing through it. This field technology is often used in medical settings as a method of decontamination. It is also used on the flight decks of very large starships, allowing them to have flight decks that open directly into vacuum without losing oxygen. Any device using this field technology is unofficially referred to as a “Maxwell” in recognition of the Terran physicist whose thought experiment first described this effect.
Taken from An Informal Guide to Known Space, Edition XVI, McPherson/Sovitt Publications.