But, after all, who knows, and who can say,
Whence it all came, and how creation happened?
The gods themselves are later than creation,
so who knows truly whence it has arisen?

-         - Nasadiya Sukta, Rigveda (1700-1100 BC)

There are fierce debates over existence of God going on all over internet. At occasions, I have myself got into these arguments and each time I wished I shouldn’t have. In these debates, there were topics which would keep coming up again and again. Big bang and beginning of time is one of such topics.

Time line of Universe
As for the topic regarding ‘Big Bang and Beginning of Time’, it is generally understood and accepted that big bang is the origin of current universe. In the development of this universe, big bang is the first ‘incident’ in itself and also the root cause of universe. Being first incident, obviously time is measured from this incident. Technically, in the context of our universe, there is no point saying that time has no beginning. In debate over existence of God, atheists take this notion of time rather too literally. (On the other hand, theist’s position is even more pathetic.)  While debating, they themselves don’t offer any rationale. Instead they cite numerous scientific resources. Their statements go like this, “But Hawking himself had said this.” Or like this, “But it is scientifically established that time has no beginning.”  Clearly, debating this way is merely being evasive and believing ‘literally’ what have been said in science literature. (Science is the belief in the ignorance of experts. - Feynman) Interestingly, at many occasions I’ve been told that big bang can be demonstrated. I don’t know what it really means. The thing is: big bang model answers as many questions as it asks.


But in a more sophisticated (or rather philosophical) way, it is incorrect to say time began at big bang. Time indeed has no ‘beginning’ on abstract level. The state at t=0 (that is the instant of big bang) must have existed for some time before big bang. If not, something must have happened before big bang which is beyond the understanding of physics. As such, it is suggested whatever happened before big bang wouldn’t have caused any effect on what happened after big bang for laws of physics governing our universe had itself no meaning at the big bang and were evolved only after big bang. In my (limited) understanding, the notion of beginning of time has a context and this context is ‘our current universe’. Time has a beginning in the context of our universe. Any event which happened in the lifetime of our universe can only be measured from big bang because our knowledge about pre big bang era is zero. May be big bang had erased all the information about anything which preceded it. Sometimes I wonder we have to go back into pre big bang era to have complete idea about universe (or multiverse.)

In addition to what I have said above, we also need to understand that big bang is the farthest point in the history of universe which science (as we know it today) is able to predict. In fact, we know more about what happened after big bang rather than big bang itself. It is simply for this reason that we can, in no way, know about big bang or any event before it.  Laws of physics just don’t permit us. The similar argument has been made by Stephen Hawking in ‘A Brief History of Time’ -

“The general Theory of Relativity, on its own, cannot explain these features or answer these questions because of its prediction that the universe started off with infinite density at the big bang singularity. At the singularity, general relativity and all other physical laws would break down; one couldn’t predict what will come out of the singularity. As explained before, this means that one might as well cut the big bang, and any events before it, out of the theory, because they can have no effect on what we observe. Space-time would have a boundary-a beginning at the big bang.”

Considering the instant of big bang, the status quo at big bang must have existed for the time unknown before this (though we cannot know anything about it). Although, it is to be noted that big bang is a theory which has been supported by plethora of evidences such as cosmic microwave background. In fact, we don’t know anything about big bang itself as has been noted by B. Greene is his wonderful book ‘The Fabric of the Cosmos’. He writes:-

"A common misconception is that big bang provides a theory of cosmic origins. It doesn’t. The big bang is a theory that delineates cosmic evolution from a split second after whatever happened to bring the universe into existence, but it says nothing at all about time zero itself."

Space-time is meaningful only in the context of current 4-dimensional universe. Can it be said that before big bang, there was only one dimensional existence i.e. that of time? I really don’t know. Any discussion which entails pre big bang era has more of metaphysical leanings and justifiably so. We can ask questions while answers may elude for centuries.  

It is like the analogy of a chicken coming out of a hatched egg. In our case, chicken is the universe and hatching of egg is big bang. A seven year old kid who only watched chicken coming out of egg is clueless about what went on before egg was hatched. For him, chicken was born in one instant. Our position as compared to that kid is worse. Of course, let me admit, this analogy has its own shortcomings. But it does illustrate my point as Bertrand Russell noted in ‘ABC of Relativity’:-

“All this is rather speculative; it is very likely that the universe evolved from a highly condensed state, and it is even more likely that such a highly condensed state represents the earliest time about which there will ever be any scientific information. Whether such a state actually occurred is not at present under dispute. Unfortunately, some people are inclined to refer to the highly condensed state as ‘the beginning of the universe’ or ‘the time when universe was created’ or something of that kind. These phrases mean no more than ‘the earliest time about which there is ever likely to be any scientific information’, and it is better to avoid them, because they carry undesirable metaphysical implications.”

Apparently, there is a theory proposed by Wun-Yi Shu which in essence does away with this big bang model altogether. One ramification of his theory is that time indeed has no beginning and big bang really never happened. This theory claims to solve the problems posed by big bang model such as horizon problem. I don’t happen to know the current fate of this theory and chances are that some serious flaws might have been found in this theory. There are other speculative theories of multiverses. In the context of multiverse theory, concept of beginning of time becomes much hazier. In eternal inflation model, there are multiple pocket universes which are disconnected to each other and these pocket universes has their own history and possibly different set of physical laws. (Read this BBC article.) Big bang model attempts to answer questions based on numerous evidences but it doesn’t explain everything. There are many questions which big bang model fails to answer and which motivate us to go beyond this model (Read here.) In fact, Martin Bojowald has tried to delve into pre big bang era through the model of loop quantum gravity. Certainly not every physicist think big bang marks the ‘absolute’ beginning of time. Origin of time is not a settled issue. There are multiple theories and models about big bang and pre big bang history. The biggest problem with pre big bang models is testability. At present, any model dealing with pre big bang incidents cannot be tested. A theory is accepted only when predictions made by it are in conformity with evidences. Obviously, a theory dealing with pre big bang era has to make predictions which are to be confirmed in this universe and we know this is, for all practical reasons, impossible. I hate to use this ‘impossible’ word and would love to be proved wrong. Tricky situation, isn’t it? 

Whether or not these theories are plausible, this confirms one thing: We are far, very very far from the truth. Our universe being 14 billion years old and spanning more than 94 billion light years of space, who knows if it is the part of some even larger incomprehensible scheme. We’d be lucky, extremely lucky, if we get answers in our own life time. Perhaps I am being too optimistic. We’ll see. And yes, I didn’t intend to propose anything about existence of God. Whether or not there is a thing called God, event like big bang in no way supports or denies his existence as Pope Pius XII tried to prove in the light of big bang in 1951 that Creator exists. Big bang is still too deep a mystery to make any conclusion out of it. If there is really a god, big bang only shows he was wrongly (or naively) imagined or depicted by religions. Let me quote Feynman here:- 

 "It doesn't seem to me that this fantastically marvelous universe, this tremendous range of time and space and different kinds of animals, and all the different planets, and all these atoms with all their motions, and so on, all this complicated thing can merely be a stage so that God can watch human beings struggle for good and evil — which is the view that religion has. The stage is too big for the drama" 

In my view, while proving or disproving existence of god, arguing over big bang is merely a futile exercise resulting out of desperation. Two hundred years, or may be more, down the  line, picture of universe will be more clear. We should wait till then. God has waited long enough.
 
At first there was only darkness wrapped in darkness.
All this was only unillumined water.
That One which came to be, enclosed in nothing,
arose at last, born of the power of heat.

-       -   Nasadiya Sukta, Rigveda (1700-1100 BC)