10 Small Details You Missed In Tenet
4. The Doppler Theory And Maxwell's Demon Thought Experiment
Tenet is not going to be lauded any time soon for its scientific accuracy, but it can act as an entry point to various scientific principles and concepts such as entropy, the laws of thermodynamics and paradoxes (which will be touched upon later).
Two less obvious ideas posited in the film's runtime that have an impact are The Doppler Theory and Maxwell's Demon Thought Experiment. To sum it up, the latter concept was designed with the intent of exploring the violation of the second law of thermodynamics, essentially reversing entropy in a manner similar to inversion.
The experiment's demon door functions in a similar manner as the turnstiles featured in the film, letting various particles through a door that reverse their entropy. The film's use of red and blue may be an example of the Doppler Effect, where light from an incoming object experiences blueshift and as the object recedes in the distances the light off it experiences redshift.
The blueshift may represent how inverted objects are moving back towards the present and the redshift may represent objects following the natural order of entropy.