If you have been a little careful while dealing with the fundamental equations of classical physics you would have noted that they seems to be symmetric w.r.t. time. In other words they involve second order differentials w.r.t. time so that replacing ‘t’ with ‘-t’ would not make any change. But the thing is that when you look at various phenomenon occurring naturally you will find that they proceed in only one direction contrary to what expected from theoretical arguments. But one could argue that law of entropy of thermodynamics says that the total entropy of the universe is always increasing( in layman’s words!). So we could say (possibly) that entropy is proportional to time as both seems to have an identical direction or in other words time increases in the direction of increasing entropy. So if we agree with this we could say that reversing the time is prohibited by thermodynamics and hence is in harmony with what we observe in nature. But wait…imagine a container in which gases of two types are mixing together and thus as time goes on the container become more and more disordered. System as we would rightly guess is irreversible and as time moves forward it would only become more and more disordered. Now if you follow the particles in the system individually and make them trace their path by reversing the time (somehow!) we could no longer say that the motion is forbidden by the laws of physics. In other words, the microscopic world is ‘reversible in time’.
A very curious thing is that a white hole could be considered as a ‘time reversed effect’ of black hole although it’s a theoretical thing it suggest that there is a relation between antimatter and time reversal. It gives a us a way to handle theoretically an antimatter as a ‘time reversed’ effect of matter or in layman’s language a matter moving away from you could be same as an antimatter coming towards you. Well that explains a lot. But am i giving a double meaning to the concept of time reversal? Well if you think so then that would be a near yes. Now i am going to extend and stretch it further until it breaks down! Consider a state of universe where all the matter ( and of course antimatter!) were crushed down to a tiny state so that the universe is only microscopically small ( i am deliberately avoiding a singularity). At this stage all nature would have no discrimination between matter and antimatter or in other words they be present in equal amounts. But universe could not continue in this state for long and would ‘decide’ to proceed forward and symmetry between matter and antimatter breaks down at this instant and matter starts to dominate ( choice of calling one antimatter and another matter is our choice).
A very curious thing is that a white hole could be considered as a ‘time reversed effect’ of black hole although it’s a theoretical thing it suggest that there is a relation between antimatter and time reversal. It gives a us a way to handle theoretically an antimatter as a ‘time reversed’ effect of matter or in layman’s language a matter moving away from you could be same as an antimatter coming towards you. Well that explains a lot. But am i giving a double meaning to the concept of time reversal? Well if you think so then that would be a near yes. Now i am going to extend and stretch it further until it breaks down! Consider a state of universe where all the matter ( and of course antimatter!) were crushed down to a tiny state so that the universe is only microscopically small ( i am deliberately avoiding a singularity). At this stage all nature would have no discrimination between matter and antimatter or in other words they be present in equal amounts. But universe could not continue in this state for long and would ‘decide’ to proceed forward and symmetry between matter and antimatter breaks down at this instant and matter starts to dominate ( choice of calling one antimatter and another matter is our choice).
The very observation that matter dominates seems to explain why the universe is one sided in the direction of time. But then you will say no that’s not a good reason, you have left the microscopic property. Hey! there is some complexity arising here. The fundamental laws of physics is the same for matter and antimatter (as far as we know) , then it would be no surprise to claim that the laws must be time symmetric and indeed it is. Then a particle obeying such a law would surely would follow a ‘time symmetric path’.
But you would then ask why the universe selected matter over antimatter or why we does not see a universe dominated by antimatter rather than matter. Well i would have to add some remarks. Firstly, choice of calling something antimatter and another matter is a choice that is entirely our own and nature doesn’t have anything to do with naming system. Secondly, the very reason or cause of domination of one over another in the present universe is still an open question!
But you would then ask why the universe selected matter over antimatter or why we does not see a universe dominated by antimatter rather than matter. Well i would have to add some remarks. Firstly, choice of calling something antimatter and another matter is a choice that is entirely our own and nature doesn’t have anything to do with naming system. Secondly, the very reason or cause of domination of one over another in the present universe is still an open question!
(Note:The contents in this article are only my ideas and opinions and should not be considered too seriously. Any comments and corrections about the articles present in this blog are welcome.)
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