#physic # [[Epistemic status]] #shower-thought # Second law of thermodynamics #todo [[Information]] in a [[Physic/System/System|system]] is always growing >The two key ideas underlying this novel proposal are a penetrating analysis of the Second Law of thermodynamics-according to which the 'randomness' of our world is continually increasing-and a thorough examination of the light-cone geometry of space-time. Penrose is able to combine these two central themes to show how the expected ultimate fate of our accelerating, expanding universe can actually be reinterpreted as the 'big bang' of a new one. >~ [[Roger Penrose]] >the Second Law of thermodynamics is not an equality, but an inequality, asserting merely that a certain quantity referred to as the entropy of an isolated system-which is a measure of the system's disorder, or 'randomness'-is greater (or at least not smaller) at later times than it was at earlier times. Going along with this apparent weakness of statement, we shall find that there is also certain vagueness or subjectivity about the very definition of the entropy of a general system. Moreover, in most formulations, we are led to conclude that there are occasional or exceptional moments at which the entropy must be regarded as actually (though temporarily) reducing with time (in a fluctuation) despite the general trend being that the entropy increases. >~ [[Roger Penrose]] ## [[The asymmetry of second law of thermodynamics]] >The irreversibility requirement of the second law brutally clashes with the laws of motion ruling the elementary constituents of matter. Remember? I said in chapter 4 that the laws of quantum theory are reversible: if they allow for a transformation, the reverse transformation must also be possible. The laws of general relativity (the other most accurate description of physical reality we possess) are reversible, too. If there is a trajectory that takes a system from A to B, there must also be one that takes it from B to A. Microscopic constituents of matter must operate in this reversible manner because they obey these laws of motion. The problem, then, is: How can the second law require that some energy transfers are irreversible and be compatible with the reversibility of the laws of motion? >~ [[Chiara Marletto]] ![[Pasted image 20220828085229.png]] # External links