Why does time go forward? How does Entropy relate to the direction of time? What really is time, and what gives it a direction? The Arrow of Time.
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We all think of time as having a direction. Yesterday is the past, tomorrow is the future. But what if I told you that none of the equations that govern our universe have anything to do with the direction of time. So what gives time its direction?
The arrow of time is given purely by the second law of thermodynamics. The second law of thermodynamics says that the ENTROPY of the universe is always increasing. Entropy is the measure of randomness and disorder of a system. One day our universe will reach a point of maximum entropy, and time as we know it will cease to exist. There will be no distinction between past, present and future. This one aspect of our universe (entropy) is what gives time its arrow. In the past there was lower entropy than now, and in the future there will be higher entropy.
So why is Entropy always increasing? Well, disorder is more likely than order. There are plenty of ways to be in a disordered state, while there are very few ways to be in an ordered state. Disorder is more probable than order.
The real question is, why was entropy ever low in the first place? It seems kind of strange that such an unlikely event should happen. This question is one of the biggest unsolved mysteries in physics. One theory is that we live in a multiverse, where baby universes are being born all the time. The baby universe start with low entropy, but the entropy of the entire multiverse increases.
If physicists manage to crack that one, all questions will be answered, we'd be able to understand the mysteries of our universe and the Arrow of Time.