Hubble - peering back in time

[Bazile]

I think I am correct in saying that the Hubble telescope has allowed man to look back in time to billions of years ago , because the light from the period soon after the big bang , has been travelling for that amount of time across the universe , to reach us .

My question is , how is the earth AT this ernormous distance away from the source of the big bang , in the first place - for the light to have been travelling from it's source for billions of years , to reach us ?

The earth wasn't in existence before the big bang and then there was the big bang at a point billions of light years from the location of the earth ?

I hope you can understand the question I am trying to ask

[mibn2cweus]

The entire universe is a product of the Big Bang. We are surrounded by it in every direction. In observing the microwave remnant of the Big Bang we are looking at evidence of what happened when it happened but not where it happened as the where always did and always will envelope us.

The velocity of light does not restrict the expansion of space itself. The current size of the universe is much larger than the distance that light can travel in the time frame of the universe since the Big Bang and continues to expand at a currently accelerating rate. Because of this we do not now observe a Bang but rather an expanding glow that will recede and persist until it fades into obscurity.

[Clanad]

A key phrase in your question concerns the Earth's distance "away from the source of the Big Bang"... A difficult concept to grasp, at least for me, is th efact that there is or was no center of the phenomena. One physicist describes the event as "happening everywhere at the same time". In attempting to draw any semi-relevant word picture for you constraints are immediately encountered. The fact is though, that an observer on a distant planet would have only the same frame of reference that we do as to speeds, and vectors all of which produce the concept of time.
The time worn analogy of an inflating balloon fits as well as anything. As seen from any one spot on the balloon's surface, all other spots rush away from it as the balloon is inflated. There is no one center to the expansion on the surface of the balloon that is singled out as the center of the Big Bang. One site says "The center of the Big Bang was not a point in space, but a point in time! It is a center, not in the fabric of the balloon, but outside it along the 4th dimension...time. We cannot see this point anywhere we look inside the space of our universe out towards the distant galaxies. You can't see time after all! We can only see it as we look back in time at the ancient images we get from the most distant objects we can observe. We see a greatly changed, early history of the universe in these images but no unique center to them in space".
OK, it's not far from this attempt at describing the Big Bang (which wasn't initially very big and certainly wasn't a bang) to the shape of the universe, which most astro-physicists see as more sheet like than round as our balloon example. That is, it's not very thick in comparison to it's other dimensions.... Check here for a better visual example of the expansion: http://edu-observatory.org/eo/cosmology.html

[Bazile]

I don't think I am quite getting over the question I am trying to answer .

Purely for illustration purposes - say the big bang happened last Tuesday and the earth was formed today this tuesday , then surely the light from soon after the time of the big bang would have gone before the earth was formed .

So how can this same light soon after the big bang be only just reaching us now ?

[mibn2cweus]

When you look at a map of the CMB remember that this is only a two dimensional representation of the direction from which each photon is now arriving in our view. These CMB photons permeate the universe not only in all directions but at various distances as well and so arrive at any given location one at a time in a continuous stream from all directions.

What they are and where they come from:
The relic radiation of the big bang we now observe was originally scattered throughout the early universe and once free to roam it accompanied the expansion of the universe that now surrounds us.

I hope you will keep asking 'til someone "gets it right"!

[jake-the-peg]

Bazille, there are a couple of concepts that you are confusing.

Firstly when we look at the light from a distant galaxy that light has taken billions of years to reach us and hence we are seeing it as it was then.

Secondly the big bang was not some huge sun that exploded into empty space - space was actually created in the big band and (this will mess with you head) time was created then too. Space and time expanded taking galaxies and matter along for the ride like currents in a bun that expands in the oven.

When the big bang happened the entire (although tiny) universe was flooded with energy - as the universe expanded that energy got more dilute and "cold" and you were left with the background radiation that we can now detect.

Crucially this is more or less the same whichever direction you look.

[Bazile]

Please bear with me a bit longer - even though you may have already answered my question , and I just cannot see it .

Perhaps if I make the following statement which may be totally ridiculous , you can see the question i'm attempting to ask.

The big bang formed the universe - the universe and the matter in it ( which eventually made the planets and stars) then expanded to an enormous size , at a pace far in excess of the speed of light ,for a tiny part of a second

The earth was then formed at a distance , billions of light years from the point of the big bang - therefore the light from the big bang is only now reaching us having travelled for billions of years across space , to reach the location in the universe where the earth is

[dawkins]

Bazile

I think (and I may be wrong) that you are confusing two different things:

1. The cosmic background radiation which is all around us, fills the entire universe this is the relic that shows the basic homogeneity of the universe some 13-15 billion years ago and is evidence that everything was on top of each other around that time. So the CMB shows that if we rewind the universe we end at a singularity

2. light from galaxies, say, 13 billion years old really did set off from a distance 13 billion light years from the earth to reach us. These galaxies would now be 10s of billions of light years away if they still survive today. In other words, the visible universe was in excess of 13 billion light years across when the light left these galaxies about 700 million years after the big bang. It is upwards of 75 billion light years across today.

Dawkins

[jake-the-peg]

There was no point where the big bang happened.

Physical space came into being at the big bang and was entirely filled with energy the universe expanded and the energy and matter was taken with it.

You cannot point to a spot and say this is where the big bang happened any more than you can point to a spot on the earth and say this is where the earth came into being

[mibn2cweus]

Although the photons of the CMB that we now observe have traveled some 13 billion light years to reach us today the Universe was much smaller when those photons were first liberated from the dense clouds of matter that first scattered them throughout the then much smaller universe. The reason we observe a number of the photons of the remnant on any given day is that those particular photons were headed in our direction and have just now caught up to the current position of the Earth in the continually expanding universe.

When you are able to grasp an understanding of the answer to your question I would be interested to see your explanation of this in your own words?