# Frame of reference and big bang

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?

• Possibly related: physics.stackexchange.com/q/2378/2451 Oct 7 '11 at 8:29
• Also see my related question: physics.stackexchange.com/q/11633 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? May 9 '12 at 7:29
• It's not clear to me why witnessing the big bang breaks any physical laws. May 9 '12 at 7:44

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 two dimensional surface of an expanding balloon may help. 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.

• 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"??!!! Oct 5 '11 at 4:21
• And yeah, I am not asking about current x,y,z of big bang's origin. 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. 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? :) 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. Oct 5 '11 at 9:58

There is no reason why we could not be viewing the BB in our frame. We can only view anything from our position in space-time, and in our frame. We don't see the whole BB 3-sphere, just that 2-sphere section of it which is located at just the right distance that light can reach us in the time that has since elapsed. That's why what we see is spread over a 2-sphere with us at the center, and at the end of our line of sight in all directions.

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.

• 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? Oct 20 '11 at 5:48

I share the OP's concern. I think the question here is one of the most important in physics. The idea of "frame" has to be abandoned or one is left with an eternity of infinite space and time sloshing about like a river or sea. It is becoming clear that things do not operate like that.

Einstein had the best stab at eliminating Newton's absolute space and time. Alas wrapping them up together and with the introduction of Minkowski space we are left with the problems of time in-variance, "rubber sheets" and still the need for some blackboard on which the fate of the universe is sketched.

For example if one considers that space and time are simply the effect of energy existing, and matter, then relativity can paint a slightly different picture. A bang in no space or time, even with infinite speed and energy, has a relative motion of zero. All directions are the same, so speed and acceleration are the same. Recent experiments have shown that at high temperatures quantum systems "lock" as degrees of freedom are limited and the system behaves as if extremely cold. Surely in the early Big Bang free from absolute space the degrees of freedom would be such that the event would be "cold" in the same way an aerosol spray freezes moisture out of the air? There is no observer or observer frame to be heated.