What is physics all about? One could say it is a discipline of sciences that includes the study of laws of nature;In fact Physics is a very wide branch including the study in very minutest regimes such as that of Quarks which are the basic constituents of the elementary particles such as electron ,protons,neutrons,and other anti particles ; to the farthest of the universe where one’s imagination cannot even reach. These regimes of physics are described in quantum physics, theory of relativity,cosmology,laws of thermodynamics and string theory.First I would like to write something about laws of thermodynamics and out of the four laws of thermodynamics the law which interests me and many other a lot is the Second law of thermodynamics. It can be stated as “Entropy of the universe always increases”. Entropy is a quantity that assigns a particular direction to all the laws of nature.For example consider a glass filled with water kept on a table ,suppose the glass falls down ,for this phenomena there might be some quantity that governs the fall of glass in direction in which the glass falls, why the glass breaks and why doesn’t the phenomena occur in the reverse order ,this is only due to increase in the entropy of universe.Events may happen in reverse order only during the big crunch. Every physics learner with keen interest in astrophysics knows that since big bang universe is expanding.This expansion depends on a certain critical density.During the big crunch the universe contracts, event occurs in reverse index order, In such a contacting universe one might die first and the born.The universe would contract till the Planck length before the big bang. It seems that the big crunch violates the second law of Thermodynamics as the disorder decreases in this case .One of the other thought experiment violating the law of Thermodynamics was first proposed by Maxwell as “Maxwell’s demon”. Consider a room which is divided by a partition wall with a small gate,suppose the part A of the room is at a higher temperature and part B is at lower temperature,on microscopic scale the average momentum distribution molecules in A is more than that in B, now suppose a demon sits on the gate controlling it such that as a molecule having higher momentum from part B reaches near the gate ,the demon opens the gate and allows it to move in A,and also when a low molecular momentum particle moves towards B the gate is opened by the demon and it allows the particle to move in B.After some time average molecular momentum of A would be so high that its temperature would increase which is against the law of thermodynamics.But the demon might have to do some work which might increase the entropy more than the decrease in above paradox and so ultimately the entropy of universe increases .This is some like how the physics takes us to the frontiers of universe and back to a glass of water.PHYSICS IS INTERESTING