Where in the world is earth?

I had posted a quick comment here about where the earth's relationship is to the recent GRB (gamma ray burst) labeled 080319B.

Briefly, it stated that it was the largest release of energy ever observed in the entire universe with the naked eye, and it occurred half way across the universe.

Considering the big bang probably is a sphere, I asked whether that meant the earth is in the center of this sphere and we are observing the light from the GRB at the edge of the big bang, or if the earth is at the edge of the big bang and this GRB is in the center of the universe. No one answered this question to my satisfaction so I emailed the primary investigator on the Swift mission team at NASA and got a response, much to my surprise.

Here is what Mr. Neil Gehrels said about the earth in relation to GRB 080319 in his email response. You decide if it says where we are inside the big bang:

Dear Mr. XXXXXXXXX,

The universe is isotropic with every point equivalent. So Earth is not
at the center. You can picture the universe as being the surface of a
ball and Earth is a point on it, the same as any other point. Since the
universe is expanding, envision the ball being inflated as time goes
on. The GRB happened when the ball was smaller and its light has been
traveling to us as the ball inflated. The light travel time was about 7
billion years and the light travel time to the other side of the ball
emitted when it first started inflating is 13.6 billion years. That is
an approximate analogy.

Sincerely,
Neil Gehrels

I'm still kind of scratching my head. I know that the big bang is expanding, and this occured at the half way point in time and space, but where does that leave us??

I think its a fancy way of saying that they don't know the exact dimensions of the universe, thus making it impossible to say where Earth is in it. The explanation of the Gamma Ray Burst seems to be that it took longer then it should have for the light to reach us because the intervening space kept getting larger.

Maybe he believes that everything in the Big Bang was the same as it is now, only smaller and it has been expanding into a magnified form. It would do a lot to explain why atomic structures and celestial mechanics appear very similar.

Well, don't they measure distances by red-shift and they have found that its the same all over? How can that be unless we are generally in the center?

If we were lets say midway across the universe, we would notice a shift in radiation one way in one direction and the same amount in the opposite direction the other way.

I really felt like the guy gave me either a kindergarten answer or he told me some cryptic truth that we are on the surface of a balloon like expansion about to come out of it or something.

The balloon is the classic analogy of why other galaxies move away from our galaxy. There is no center of expansion. The big bang is a point in time, the beginning of everything, not in space.

Well, don't they measure distances by red-shift and they have found that its the same all over?

Red shift is the result of the Doppler effect. If measures relative speeds. The ratio speed / distance is nearly a constant, the Hubble constant. Nearly because galaxies also have their own random speed vector, that has nothing to do with expansion. The red shift gives a good indication of the galaxy's distance, except for the nearest ones.

How can that be unless we are generally in the center?

Every galaxy is receding from every other galaxy, generally. That's expansion.

If we were lets say midway across the universe, we would notice a shift in radiation one way in one direction and the same amount in the opposite direction the other way.

There is no center, no midway (that we know of). The shift is the same in every direction. Imagine a 2D being on the inflating balloon. We're 3D and the balloon is the universe.

To answer your main question I think "half way across the universe" means "half way across the observable universe". The observable universe is limited, as the speed of light is finite. The universe, OTOH is possibly infinite.

This is one of those ideas that takes some time to get your head around. The short answer is, we really do not know exactly where we are in respect to the 'center' of the universe. It really does not matter.

Think of it this way: At one point in time, we were crushed up against every other piece of matter in the universe. There was no space around us. Then everything started moving apart, even us. That means that it does not matter if we're halfway across, a fourth of the way across, etc. Everything is moving away from us, and the farther it is from us, the faster it appears to move.

There is no blue shift, because nothing is moving closer to us. There may well be as many blue-shifts as red-shifts, except for the fact that we are moving with the expansion as well.

The balloon analogy is pretty apt, and it was what helped me to understand the concept, but maybe my explanation along with it will help you. Just think on what has been posted for a while; chances are it'll sink in like it did with me. Might want to put some eyeglasses on, just in case your eyes decide to start spinning around when you understand it completely.

TheRedneck

Well, after reading these posts, I think I got it, but I still have a couple questions.

If it is analogous to a balloon, then the center or origin does contain anything. We would be a point on the surface and can observe all other points as roughly moving apart at the same rate. I got that so far.

Here's a couple things I don't understand. The view of the inside or outside of the surface of the balloon. If we viewed toward the center of the balloon, would we see anything or would that area be blackness, or shouldn't we see stuff on the other side of the balloon? Wouldn't that be moving away from us?

Looking the direction away from the center, wouldn't there be also nothing to see but whatever is outside the big bang? It too should be relatively void of material after a much less shorter distance than say looking sideways.

reply to post by ben91069

The balloon analogy is 2D, while we live in a universe that is (at least) 3D.

There is no center. If you take a balloon that is perfectly spherical, is there a left or right side? Up or down? No, unless you arbitrarily define a point as such. So every point can be considered as a 'center'. The same thing happens with a big bang universe. Everything is in the 'center'. The only way a center like you are thinking could exist is with an arbitrary definition of one point as 'This is our center'.

Now you should be seeing why I suggested sunglasses.

TheRedneck

Originally posted by TheRedneck
reply to post by ben91069

 

The same thing happens with a big bang universe. Everything is in the 'center'. The only way a center like you are thinking could exist is with an arbitrary definition of one point as 'This is our center'.

Now you should be seeing why I suggested sunglasses.

TheRedneck

You know that makes no sense to me at all, and I have no way to grasp it. I cannot conceive an explosion without a center. That just makes no sense and I don't even see how science can accept it as fact.

I agree that this is difficult to understand. From reading the e-mail reply it sounds like he is saying we are on the edge of one side of the universe, and the GRB occurred on the other? Considering that the age of the universe is 13.8 billion years, and the GRB happened 7 billion years ago. If the Big Bang Theory is right, and everything expanded from a single origin, then that would mean that 7 billion years ago the universe was a little more than half the size it is today, Right? That would be 13.7/2 or the size of the universe at that time was roughly 7 billion years wide. So at that time, if the GRB was 7 billion light years away from us that would put us near one edge of the universe, and the GRB near the opposite edge. You have to remember that the speed of light is not relative and does not take longer to get here from an object that is moving away from us.

That doesn't make sense because the background microwave or WMAP is somewhat uniform around us. This is the after glow of the Big Bang which appears to me to be the same all around, which one might think that would put is near the center of the universe. The recently released image of the Two Micron All Sky Survey in the Astronomy Magazine article 1.5 million Galaxies Revealed also shows a uniform distribution of other galaxies around us, which also supports that.

This is enough to make your head hurt thinking about it, but all I know is that we are probably NOT near one of the edges of the universe and it would be presumptuous to think we are at the center of the universe. Good topic though.

reply to post by ben91069

Eh, sorry. I'll give it another go. It really is a difficult concept until you grasp it.

When you think of an explosion having a center, that's because you are standing outside the explosion, looking into it. In that context, there is a center. There is a single point that rapidly expands outward in all directions.

In the big bang, we are no longer outside looking in. WE are the explosion. There is no outside (that we know about) to look inward from. So from our point of view, since everything is at the 'center', there is, in effect, no center.

Try thinking of it as relative.

edit to add:

Originally posted by Hal9000
This is enough to make your head hurt thinking about it, but all I know is that we are probably NOT near one of the edges of the universe and it would be presumptuous to think we are at the center of the universe. Good topic though.

Agreed, excellent topic. Worthy of a flag, come to think of it.

TheRedneck


[edit on 1-4-2008 by TheRedneck]

Originally posted by ben91069

Originally posted by TheRedneck
reply to post by ben91069

 

The same thing happens with a big bang universe. Everything is in the 'center'. The only way a center like you are thinking could exist is with an arbitrary definition of one point as 'This is our center'.

Now you should be seeing why I suggested sunglasses.

TheRedneck

You know that makes no sense to me at all, and I have no way to grasp it. I cannot conceive an explosion without a center. That just makes no sense and I don't even see how science can accept it as fact.

Ok, imagine you have a perfectly spherical balloon. Now, look at the surface. Where is the center of that surface? Not the center of the balloon, but the center of the surface of the balloon skin. There isn't one, unless you put some sort of a mark on the balloon, and say "There's the center." But that's not really the center, because what makes that point you chose different from any of the other points on the balloons surface?

WE are inside the explosion but it would have to have an origin. Do scientists know generally which direction that came from?

It would seem that if they knew that then they could tell young stars would be in one direction and older ones would be in another.

reply to post by TheRedneck

No, I understand that relative to our position, everything will appear to be moving away from us due to the expanding universe. That isn't what I had a problem with. What I was saying was that the light from the GRB took 7 billion years to reach us, and occurred 7 billion years ago, when the universe was smaller. Where I made my mistake was that I was assuming that the universe could not be more than 13.7 billion light years across because that would mean things were moving faster than the speed of light. Under that assumption, 7 billion years ago the universe had a size of 7 billion light years, which would mean the GRB was near one edge, and were were near another. I also didn't consider that 13.7 billion years is a radius so you would double it for the entire size.

Anyway, I found the answer to my problem in this article Universe Measured: We're 156 Billion Light-years Wide! which helps explain a lot. According to the article the speed of light is cumulative as the universe also expands.

I looked around for more info on where the Milky way is located in the universe, but there isn't much there. I did find this article.

It is difficult to say where in relation to the universe the Milky Way is located since we don't think that the universe has a centre, and that (on large enough) scales it is completely homogeneous and isotropic.

Where, in relation to the entire universe, is the Milky Way located?

Maybe this is what you (TheRedneck) were referring to about not having a center?

reply to post by Hal9000


Interesting articles! But they don't tell you it's the size of the observable universe, not the real size of the universe. The volume of the universe may be infinite - by current theories. No one knows, actually, because we don't have any information about the shape of the hypersurface we call the universe. The curvature of space defined by General Relativity is irrelevant. A 2D analogy: a piece of paper with zero curvature (flat), still has zero curvature when crumpled in your pocket. Curvature is intrinsic to the space it describes, it does not help imagine what's outside the universe, or even if there's anything at all. So take the balloon analogy with a grain of salt, the universe is not a hypersphere.

Originally posted by ben91069
WE are inside the explosion but it would have to have an origin. Do scientists know generally which direction that came from?

There is no direction. It's not only matter that originates in the big bang, but space itself. The balloon in the analogy is the universe, not the matter (hundreds of billions of galaxies) in it.

Okay stupid question here... if we let allthe air out of the balloon and wad it up in a little ball, we have the original singularity, right? Then we fill it up with air (the big bang). Is there anything inside the balloon and wouldn,t the center of the universe be the center point INSIDE the balloon? Maybe I just don't get it.

reply to post by MsSmartypants


As I already said, the balloon is a simple analogy, not a correct interpretation beyond the inflating, increasing its surface (analogy to volume in 3D). The universe is not a hypersphere. No one knows what's outside the universe, or even if there is anything.

reply to post by nablator

I agree that no one knows for sure what the shape of the universe is, and from the article I posted they are calculating the size of the universe from measurements taken from the WMAP, which is the most distant object seen. So you are right, that it is the size of our observable universe, but since the microwave background radiation occurred 300,000 years after the BB, we are looking back in time to the beginning and there could not be much more beyond that in our universe. What could be beyond that is anyone's guess. I think that it would also be presumptuous to think ours is the only universe.

The article I posted also said that they also determined that the universe is "flat" based on the WMAP. I think this is misleading because "flat" does not mean flat as in a piece of paper. My interpretation is that when they say it is flat, it means it is not curved as you said, or if you look out into space, our line of sight is straight and does not bend. So when you look out into space you are looking at the edge of the universe no matter what direction you look. In other words, space does not curve around and an object would physically be closer to us than how they appear from our line of sight. I just don't see how you can say space is not curved, and use the analogy of crumpled paper, because that sounds like curved space to me.

Here is another explanation of a "flat" universe.

IMHO, the universe would have to be in the shape of a sphere, because it is "flat" or not curved, started at a single point of origin and has expanded in all directions from that point. At least that's my interpretation at this point and may be wrong. In fact I just read another article from Astronomy Magazine called What is the shape of our universe? and if you look at the image on the front cover, that is the shape of the universe including other dimensions or manifolds. This is way above my understanding, but thought it was interesting.

[edit on 4/2/2008 by Hal9000]