1
$\begingroup$

After seeing the James Webb space picture, in which a tiny sliver of the sky the size of a piece of rice from our perspective here on Earth was examined and revealed contain, as expected, an abundance of galaxies and stars, I am wondering how this confirmation coincides with the Big Bang theory and the concept that Earth is in a non-privileged location in the Universe.

A common line NASA uses regarding the Webb telescope is that "looking into space is like looking back in time", which is true, for it take time for light from those distant objects to reach us. So, by examining far enough into a region of space, we are able to "wind back the clock" to see early galaxies now long dead and some of the earliest stars in the history of the Universe. What seems odd to me is that we see the same things at roughly the same distance from every direction in space.

If Earth was located in an unprivileged spot, anywhere but the center of the Universe, then some of the space around us should go "farther back" than others.

I understand that we are limited in the amount of light we are able to see. An apt comparison would be that we are in a sort of bubble isolated from the rest of the Universe and can only a uniform distance back in all directions. But this doesn't explain why each direction contains roughly the same timeline of events. We can see back a uniform distance, but the fact that this uniform distance seems to reveal the same information in all direction is confusing to me.

It won't do just to say the Universe had no "point" in which is started - the BB should be thought of as a sort of circle, the center of which all events spread uniformly from. We are just one event way off in a region of that circle necessarily closer to some part of the circumference than others, since our galaxy did not exist at the beginning of the Universe. So, we should be able to look one way and see nothing beyond galaxies roughly our own age and no early stars, and look the exact other way and see a much richer history, with more early stars and galaxies layered atop one another. But this is not the case - we see the same "density" of events from all directions. Unless, in some way, we are also seeing future events in some direction? Not sure how that would work.

Improve this question
$\endgroup$
2
  • 1
    $\begingroup$ Maybe I'm misunderstanding your model of the cosmos. I don't get why you say "the BB should be thought of as a sort of circle, the center of which all events spread uniformly from". Standard cosmology says that the BB happened everywhere, at the same time, so there's no center or circle (or sphere) of events. $\endgroup$
    – PM 2Ring
    Jul 13, 2022 at 13:09
  • $\begingroup$ Could just be I don’t know how to conceptualize this. The BB was the origin on spacetime, so it didn’t “happen” anywhere, but as a result, what it expanded as is the physical Universe. My idea is like similar to a 3D plus 1D time model I guess where the BB is that origin dot and as a circle expands from that origin, so the universe expands - the larger the circumference as you expand is indicative of the rate of expansion. So, the Universe starts, time goes by, and our field of vision likewise expands around our later-formed position in space. A circle within a circle. $\endgroup$
    – Jack Casali
    Jul 13, 2022 at 22:41

2 Answers 2

Reset to default
3
$\begingroup$

Assuming, as you seem to do, that there is an edge of the universe, what if we were very far from the edge, so that the part we can observe (the observable universe) is a very small circle inside the big circle of the universe? Do you agree that in that case we would see the same amount of history in every direction?

This is a semplification, of course. The universe is not a circle, it doesn't have an edge. A better shape to imagine the universe is the surface of a ball. If the universe were an expanding ball and we and all the galaxies were on its surface. Then, wherever you stand on the ball, wherever you look, you see the same amount of history, in the same way that a person standing on the surface of Earth sees the same amount of land/sea in every direction.

Improve this answer
$\endgroup$
1
  • 1
    $\begingroup$ Yeah, you hit the nail on the head with the big circle/little circle comparison. I think you answered my question. Every “spot” in the Universe acts as it’s own center of expansion. All things move away from “that spot” at the same rate they would move away from any other spot. I’m still having a hard time grasping why every direction looks the same, but your explanation does make enough sense to me that I kind of see where I am mistaken. $\endgroup$
    – Jack Casali
    Jul 13, 2022 at 22:32
3
$\begingroup$

If Earth was located in an unprivileged spot, anywhere but the center of the Universe, then some of the space around us should go "farther back" than others.

This is not the case, at least not if cosmologists have anywhere close to the correct concept of the universe. It is far better to view the big bang as an explosion of space rather than an explosion in space.

What this means is that regardless of location in space, all of space appears to be expanding centralized on that location. What we see from Earth is distant galaxies retreating from us, regardless of direction. What some alien species in a galaxy far far away sees is that all galaxies that are distant to them are retreating from them, regardless of direction.

Improve this answer
$\endgroup$
3
  • $\begingroup$ Is there any simple explanation as to why the contents of what they “see” are the same, though? Like I do understand that space is expanding proportional to the distance a thing is from another things location, but I don’t quite see how this explains that everyone “sees” the same stuff. I am imagining that some galaxies formed later than ours are so distant they cannot see early stars, but they do see fully formed galaxies. Similarly, the universe, while expanding from us at a constant rate, should have “more” in one direction than another, since we are not located at the origin. $\endgroup$
    – Jack Casali
    Jul 13, 2022 at 22:36
  • 1
    $\begingroup$ There is no origin. Maybe this will help - imagine a flat, infinite sheet of rubber with dots equally spaced on it. Now stretch that sheet of rubber in X and Y dimensions so that the sheet grows. From the perspective of any dot on that sheet, all the other dots are moving away from it. The furthest dots will have moved the most. But there is no 'center of expansion' - just a uniform growing of the spaces between everything. $\endgroup$
    – Dan Hanson
    Sep 3, 2022 at 22:06
  • $\begingroup$ @DanHanson I would assume you were directing your comment to Jack Casali (the OP) rather than to me. $\endgroup$
    – David Hammen
    Sep 4, 2022 at 0:34

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .