Big Bang - why can we only look "out"?

[benny]

Right - apologies in advance for any abject stupidity evidenced here. I am not a scientist.

I saw the new hubble photos released today of the farthest reaches of the universe. Nice pics.

This got me thinking. Telescopes look "out" at the universe and see light from billions of years ago, expanding outwards into the void (and for that matter so do I when I look at the stars). Why can't we look back in - that is, into the epicentre of the "bang". Everywhere we look, stars are travelling away from us. Surely if we are travelling in a straight line, we should be able to look back at where we've come from - is there not a stationary "starting point".

I have searched for this and found nothing. Apolgies again for any ignorance.

[rsa]

Short answer is that there is no central point from which the universe expanded. The universe is all there is, so there is no "void" for it to expand into. Every point in the universe is growing more distant than every other point (on large scales).

We can look back into time because of the time that the light from those old galazies took to reach us. There beccomes a point however when the universe was so dense that is was opaque to light, so we can never look all the way back to the big bang.

[Q.E.D.]

A good analogy is the surface of a balloon. If you draw dots all over it, then blow it up, you'll be able to see each dot moving away from every other dot, yet there is no center.

Rsa, the universe became transparent to light about 300,000 years after the Big Bang, IIRC. So, as you said, that's as far back as we can observe.

[David Simmons]

Right - apologies in advance for any abject stupidity evidenced here. I am not a scientist.

I saw the new hubble photos released today of the farthest reaches of the universe. Nice pics.

This got me thinking. Telescopes look "out" at the universe and see light from billions of years ago, expanding outwards into the void (and for that matter so do I when I look at the stars). Why can't we look back in - that is, into the epicentre of the "bang". Everywhere we look, stars are travelling away from us. Surely if we are travelling in a straight line, we should be able to look back at where we've come from - is there not a stationary "starting point".

I have searched for this and found nothing. Apolgies again for any ignorance.

In a sort of way scientists can look at the "bang," or what is left of it.

In 1948 scientists George Gamow and Alpher (whose first name escapes me) made some reasonable assumptions about the initial temperature of the big bang and computed what the temperature of the big bang radiation should be now. This resulted in the prediction that there should be a relatively uniform frequency of background radiation in the microwave frequency region. In 1965 such background radiation was found by Penzias and Wilson. The best present explanation for this radiation is that it is a remnant of the "big bang" after having cooled off for 13 billion years.

[David Simmons]

The theory of which the original computions was a part was credited to Alpher, Beta, and Gamow.

Gamow, who was a well know wit, asked Bethe to add his name (for a minor suggestion he had made) to the theory so that it could be Alpher, Bethe, Gamow or alfa, beta, gamma.

After some hesitation Bethe agreed although he protested that he hadn't really participated in the theory's formulation.

Later on the theory ran into some difficulties in some of its parts, not the background radiation but elsewhere, and Gamow wrote that Bethe then said to him, "I wish now that my name had been Schmidt."

[aerodave]

Check out this bit of mind-bending logic. It's so simple, but when I first wrapped my mind around the idea, it gave me definite pause.

From The Elegant Universe, p. 346:

You don't have to search far to locate where the big bang occurred, for it took place where you are now as well as everywhere else; in the beginning, all locations we now see as separate were the same location.

So, the location of the big bang is everywhere at the same time! No matter which direction we choose to look, we are by definition looking toward the big bang (and away from it at the same time).

Every point in the universe is the location of the big bang. I find that incredibly fascinating.