Answer
Energy and momentum are conserved, but the second law of thermodynamics is not conserved.
Work Step by Step
In simple terms, conservation of energy means that in an event, initial energy equals final energy. Conservation of linear momentum means initial momentum equals final momentum.
The initial energy of an event in the original film becomes the final energy of the event in the time-reversed film, and the final energy in the original film becomes the initial energy in the time-reversed version. But energy is still conserved. Similarly, final and initial momentum swap places. But momentum is still conserved.
But time-reversed film violates the second law of thermodynamics. As an example, we consider in the original film that heat flows spontaneously from a hot object to a cold object without any external work done. In the time-reversed film, heat will flow spontaneously from the cold to the hot object without any external work input. This is against the second law of thermodynamics. Thus, the second law of thermodynamics is not conserved.
