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I have read Brief History of Time in which he has wonderfully described the formation of universe. What is the frame of reference from which we are viewing the big bang? What is the frame of reference from which we are seeing the events associated with the big bang? Where is this frame situated?

Edit The frame of reference cannot be same as the one we have now, right? Because physical laws break when we are witnessing BB. So this frame should be different somehow, right?

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Possibly related: physics.stackexchange.com/q/2378/2451 – Qmechanic♦ Oct 7 '11 at 8:29
Also see my related question: physics.stackexchange.com/questions/11633/… – AlanSE Oct 7 '11 at 14:27
The frame of reference cannot be same as the one we have now, right? Because physical laws break when we are witnessing BB. So this frame should be different somehow, right? – Mahesh M May 9 '12 at 7:29
It's not clear to me why witnessing the big bang breaks any physical laws. – Mark S. Everitt May 9 '12 at 7:44

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If you are asking "where is the Big Bang origin now", its x,y,z coordinate, the answer is that every point in the universe was at the origin of the Big Bang, thus every x,y,z point now can be considered as the origin of the BB.

The analogy of the two dimensional surface of an expanding balloon maybe helps. At t=0 all surface points were putatively at the origin, then the balloon expands and all points on the surface recede from each other, and any one of them can be considered as the origin of the expansion in the two dimensional surface.

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This is the exact analogy that I have heard. But when we look at baloon we are not on baloon.so when we watch big bang or (as some say its not possible theoratically for us to be at t=0) if we are watching few nanoseconds after big bang, where are we? are we inside the space-time that has just been created or watching it from "outside"??!!! – Mahesh M Oct 5 '11 at 4:21
And yeah, I am not asking about current x,y,z of big bang's origin. – Mahesh M Oct 5 '11 at 4:23
In the ballon analogy, we are a point , on the surface of the balloon. That is why it is a fair analogy. In our three space plus one time dimensions, our observation point is within these dimensions, and there is no point :) in asking where the origin of BB was, as it would be for a two dimensional citizen on the surface of a spherical radially expanding balloon. It is where we are as far as our observations can tell. – anna v Oct 5 '11 at 4:35
"Our observation is within these dimensions" :) We have freezed the time. We are trying to measure the width of the universe from "within the universe". How wide will it be? :) – Mahesh M Oct 5 '11 at 8:58
as an additional point, the balloon analogy is only true for a 2-D universe, where the universe is situated only on the surface. – Vineet Menon Oct 5 '11 at 9:58
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We are discussing the big bang from a reference frame rigidly fixed with earth unless you are an alien ;-).

On a serious note, according to the general theory of relativity, every frame of reference is equally suitable to express the physical laws. So even if you are situated in a different rotating galaxy all the laws of physics of the origin of the universe should be the same!

A better question would have been why we say the age of the universe is such and such (we don't say with respect to us) when time is not an absolute quantity. The reason is the large scale homogeneity and isotropy of the universe which provides a lucky symmetry which enables us to describe the age of the universe in an absolute term.

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But when we are talking about big bang can the reference be still earth? I mean can we watch how food digests by being the food ourself? – Mahesh M Oct 20 '11 at 5:48

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