Shabbat 39a says: "With regard to heating food in the sun itself, everyone agreed that one is permitted to place food in the sun to heat it, as it is certainly neither fire nor a typical form of cooking".
However, today we know that sun and fire, from physics point of view, are actually quite similar (they consist of matter in form of plasma). So the statement "it is certainly not fire" can be questioned. That brings me to the following question:
Can halacha be changed/adjusted, if a scientific research shows that some of the argumentation behind it was actually not valid? Has it happened, does anyone know some examples?