THE ARROW OF TIME ~ 2

 

HEY THERE !! This blog is the continuation of the previous one which I ended up with suspense of 'why does the disorder increase in the same direction of time as that in which the universe expands?' So, let's scratch it up to find the answer. But to understand the solution to this query, you need to visit the previous blog.

Before reading further, you must  know the meaning of the following:

NO BOUNDARY PROPOSAL - In the 1980s, Stephen Hawking and James Hartle put this proposal, which states that the universe has no initial-boundary conditions on either time or space. Or it simply states that asking what came before the big bang is meaningless like asking what is south of the south pole because there is no notion of time available to refer to. The concept of time only exists within our universe.

WEAK ANTHROPIC PRINCIPLE - It is the truism that the universe must be found to possess those properties that are necessary for the existence of observers. It is not a theory of physics. Rather, it is a methodological principle.

Let's keep these two principles in mind while moving forward. 

Returning to our question that why do we observe that the thermodynamic and cosmological arrows point in the same direction? 

According to no boundary proposal, the universe has started in a very smooth configuration or with low entropy (disorder) and according to the second law of thermodynamics entropy always increases. This implies that if the universe has started with low entropy it would increase till its saturation. The universe will be in a complete disorder means all the stars will have burned out, black holes will evaporate and everything will be in its complete chaos. It also implies that our existence will also disappear. However, this is not what we see!! We are alive! This implies that we are in the middle of the process leading to complete chaos. 

What we have observed so far is that our universe is expanding that is the cosmological arrow of time is increasing. Why is it so? This can be explained by the weak anthropic principle that the condition of expansion of the universe is suitable for the existence of intelligent beings. If it would not be the case we would have observed the universe to be contracting but this is not true.

To survive, human beings have to consume food, which is an ordered form of energy, and convert it into heat, which is the form of a disorder of energy. This intelligent life could not exist in the contracting phase of the universe. This explains why we observe that the thermodynamic and cosmological arrows of time point in the same direction. It is not that the expansion of the universe causes disorder to increase. Rather, it is that the no boundary condition causes disorder to increase and the condition to be suitable for intelligent life only in the expanding phase. 

Hope you all got your answers😊

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