|American mechanical engineer Bill Nye explaining, in his 1993 Disney science education book Bill Nye the Science Guy’s Big Blast of Science, that people have used the laws of thermodynamics to explain why people fall in love. |
In technical language, the state of behavior characterized by the term "falling in love" refers the process in which two previously unattached people, collide in time, surmount the activation energy barrier to reaction, and slide down into the free energy stability range on the potential energy surface (below relationship equilibrium level), and fall into the confines of a paired human molecular bond, in the unified structure of a dihumanide molecule.
Scientists, according to the views of American mechanical engineer Bill Nye, have been using thermodynamics to explain how people fall in love since before 1993.  It is puzzling, however, as to who Nye is referring to?
|The process of falling in love is best visualized by plot of the potential energy surface of the reactants (unpaired individuals) on going to reactants (relationship). The plot above shows the free energy versus extent of reaction, showing various hypothetical final states, in various stabilities (A≡B, A≡D, A≡C, begin stable products; A≡X being an unstable product) above and below thermodynamic equilibrium.|
In the 1993 book Bill Nye the Science Guy’s Big Blast of Science, a Disney-version science book, in the section on thermodynamics, American mechanical engineer Bill Nye comments that someone previous to him has used thermodynamics to explain why people fall in love.
A pre-1993 reference to someone who used thermodynamics to explain “why people fall in love” is puzzling? He could be making a reference to German polymath Johann Goethe, and his 1809 human elective affinity work, but this was not pure thermodynamics, but rather pre-thermodynamics (in the sense that affinity was precursor to free energy); and it is doubtful that Nye knew at this time that affinity equates to free energy change, a fact that only people with a chemistry background or interest know about this factoid.
It is possible, however, that Nye is making reference to Tom Stoppard’s play Arcadia, a modern-day remake or twist on Goethe’s Elective Affinities, in which Stoppard uses the second law concepts, such as heat death and sexual heat, in discussions of human passions and love. Arcadia premiered on April 13th, 1993, and Nye’s book was published on Sep 21, 1993, so it is possible Nye could have either saw the play or read a review.
To give an example summary of Stoppard’s use of thermodynamics in his play, writer Katherine Kelly summarizes in her 2001 Cambridge Companion to Tom Stoppard that the part in the play when Septimus quotes the tomb inscription ‘Et in Ardccadia Ego’, in Poussin’s celebrated seventeenth-century painting, to mean ‘even in paradise there is death’, that Thomasina knows about the second law and how the “entire universe is dying, inevitably heading towards an entropic dead end”, expressed as “heat goes to cold” as Valentine explains to Hanna. In another instance “It’s a one-way street … It’ll take a while but we’re all going to end up at room temperature”. In this scene, Kelly explains that: 
“Thomasina refuses to give in into despair. She is thinking of heat in more than one sense: not just the heat of thermodynamics but the heat of Eros. For she is falling in love with Septimus, and begs him to teach her to waltz.”
1. Nye, Bill. (1993). Bill Nye the Science Guy’s Big Blast of Science (pg. 50). Basic Books.
2. Naumann, Earl. (2001). Love at First Sight – the Stories and Science Behind Instant Attraction, (ch. 2: “The Chemistry of Love”, pgs. 23-42 ). Naperville, IL: Casablanca Press.
3. Kelly, Katherine E. (2001). Cambridge Companion to Tom Stoppard (pg. 189). Cambridge University Press.