Is it agreed my physicists that time is an emergent property resulting from the 2nd law of thermodynaimcs? The universe started from very low entropy and entropy increased from there and will keep on increasing. The result of its increase is heat flow which basically means chagne at all scales in the constitiuents of matter. It is the change in matter flow that has enabled the universe to be what it is and the change will continue as long as entropy is not maximised. This change has produced us in the universe and we observe this change and create an an entity called time to explain this change. As if time allows things to change. But really it is the second law at work and change will stop when entropy is maximum. When the universe achieves this state, time as we know it will also have stopped. In this way it is the second law which creates the effect of the existence of time. Time is an artificial quantity just like the x,y,z spatial coordinates in that it isn't a fundalmental law of physics. I have been very unsepcific but is it basically correct? If so then the idea of going back in time is nonsense because to do so would mean violating the 2nd law of thermodynamics. This is consistent with SR where in that theory it also argues that travelling back in time is physically impossible. It's good to see two theories giving the same results. However, they both are classical theories applied to macroscopic objects. I am aware some individual atomic entities can travel back in time. I have heard that the 2nd law can also explain why a ball falls to the ground when released from a distance from the bottom of the ground. I thought it was because of gravity although time is recquired for gravity to do work on the ball. Is the need for time how the 2nd law comes into it? i.e. the entropic state when the ball was realsed was lower than after it collided with all the air molecules. After the ball collided with the molecules and also the molecules on earth which it would touch when on the ground, entropy has increased which is explained by the 2nd Law. That's why it falls. It seems like gravity isn't needed to explain why a ball falls?! Is gravity an emergent property of the 2nd law? I see a connection in that far away where matter density is low, gravity is low. So the change in entropy after letting go of the ball would be lower than on earth hence it dosen't move as fast which is consistent with the 2nd law.