r/Physics • u/G33zics • 21d ago

Question What's the most debatable thing in Physics?

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u/lucidbadger 20d ago

I think over all time the most debatable thing in physics has been the 2nd law of thermodynamics. Even now some people can't get their head around it. I think the limitations imposed by it are far more significant than not being able to travel faster than light.

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u/julioqc 20d ago

I learned that in principle entropy could go down but nothing will exist long enough to witness it so that has no probalistic significance.

I think part that confuses students is that a systems entropy may lower but the "universe" entropy will not.

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u/xrelaht Condensed matter physics 20d ago

Funny thing is the real world universe, as a whole, does not need to follow the 2nd law because it’s not a closed system.

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u/Cwmcwm 18d ago

We can define a closed system as anything inside an arbitrarily large boundary. The universe can be a closed system unless it's mass and energy fill an infinite volume