Time flies like an arrow
Fruit-flies like a banana!
A funny quote indeed. But why does time fly like an arrow, always in the same direction? From past to future. Or does it?
I have been curious about this time ever since I read A Brief History of Time while in high school.
There is no law in physics which mandates the direction of time except for the second law of thermodynamics. If not for this law, physics doesnt mind things traveling back in time! Age/Time is a question of mind over matter, if you dont mind it doesnt matter!
But what about causality which says cause should come first and then the effect should follow it. Suppose I drop down a glass and it breaks. The action of dropping down is the cause and the breaking of the glass is the effect. Now if we reverse the reel, then the broken glass will come together into a single glass and will come up into my hand!
Doesn’t it look strange? Or is it just because we are not used to it?
Whats the problem if broken glass comes together to form a complete glass? Well, second law of thermodynamics says entropy/disorder of an isolated system always increases with time. Entropy isn’t what it used to be
But some say that the time will be reversed when the universe undergoes a big crunch later and collapses into a singularity. The second half of Brahma’s life ?
So how will be the reversal of time? Will it be like a reversal of entire movie or will it be a reversal of individual character roles? Second law of thermodynamics then would state that Entropy decreases with time! OR will it be that Entropy increases with time locally, but decreases with time globally?
Feynmann’s diagrams say that antimatter particles are nothing but normal matter particles except that they are traveling back in time! So if there is a part of this universe made up of anti matter and a civilization there where all the people are made up of antimatter, will they be traveling back in time? Does it mean that those humans will remember tomorrow and their astrologers there will be predicting yesterdays? Future will be taught as history, and past will be predicted!
Is that the reason why matter-antimatter meetings result in annihilation? Because nature does not want information to be transferred between past and future, so that the thrill of living in the present is maintained? I think we exist only because of the mercy of anti-matter .
Theory of relativity says time is just another dimension of space-time. So, if both space and time are same well, we can see in space, can we see in time? We can look left and right, front or back, up or down and see beyond where we are currently standing in space. Similarly can we see beyond our present time? Can we look into the next hour or the previous hour? Was this what the yogis of ancient India were doing when they said that one has to close the eyes and look within oneself to peep into the future? Invoking a inner sense via yoga to look beyond current time? Is there a hidden sense in us for an out of body time travel?
In space I can easily increase or decrease the speed of my motion. But can we do that in time? Can I decide that I will move only 10 seconds in the next one hour, or that I will move 10 hours in the next one hour? Probably yes, using high gravity fields like that of neutron stars I can slow down my local time and hence jump into the future. But can the direction be reversed? A rotating black hole or a worm hole used as a time machine? Thanks to the field equations of general relativity !
Or does multiple time lines exist where, whenever there are multiple possible outcomes of an event the universe splits into multiple universes, each containing an unique outcome? So if I throw a coin, universe splits into two, where in one universe the coin will fall with heads up and the other will have tails up! Even my self consciousness will be split and will enter both the universe as separate consciousness!
So do parallel universes coexist where each possible history version exists! Like in our universe India got independence from Britain in 1947, where as in another parallel universe Britain got independence from India in 1947! Does that mean History in all these parallel universes is just a set of permutations and combinations splitting on every occasion?
Or is time just an illusion created because of motion. As some great philosopher once said, will time still move if everything in the universe comes to a standstill?
To see the world in a grain of sand,
to see heaven in a wild flower,
to hold infinity in your hand,
and eternity in an hour