Do we know where the center of the universe is?

[SeanDamnit]

Just a random thought - if we know the universe is expanding - that things in the universe are moving away from each other - do we know the physical location where it all originated? Like, was there a specific point where it all began and expanded away from?

Disclaimer: I may not fully understand the things I am asking. I couldn't find any information on the subject in a Google search.

[Fredrik]

Depending on taste, you can say that there is no such center, or that every location is that center. There was another thread about this recently, so maybe you should search this forum.

[Tubbythin]

Yes. Everywhere. Its space itself that is expanding so the point at which the universe started is now spread out over the whole universe.

[ravdin]

It's like asking where the center of the earth's surface is. It can be anywhere you care to define it- such as the spot you're standing on right now.

[ksbluesfan]

That confuses me. If the universe is exanding like a balloon that is being blown-up, there should be a center, right? If our galaxy is at a certain point, some points will be moving in the same relative direction, though still getting farther away, while other points are moving away from us.

[SeanDamnit]

It's like asking where the center of the earth's surface is. It can be anywhere you care to define it- such as the spot you're standing on right now.

I've decided the center of the universe is wherever I am. How do I go about letting everyone know this from now on?

[Tubbythin]

The universe in this analogy is the surface of the balloon. The surface of a balloon has no centre.

[SeanDamnit]

I did end up finding some articles on this that explained it adequetly. The balloon analogy was helpful demonstrating the concept to me.

[Loss Leader]

That confuses me. If the universe is exanding like a balloon that is being blown-up, there should be a center, right? If our galaxy is at a certain point, some points will be moving in the same relative direction, though still getting farther away, while other points are moving away from us.


The universe is expanding like the skin of a balloon that's being blown up. There is no center of the surface of a balloon.

[ksbluesfan]

The universe is expanding like the skin of a balloon that's being blown up. There is no center of the surface of a balloon.

Huh? Even if that is the case, the skin of the balloon on the far side is moving away at a different rate than the skin of the balloon on the same side, isn't it?

[Fredrik]

The search feature of this forum is just unbelievably bad. 90 seconds, wtf!? I'm pretty sure the title of the other thread was "where is the center of the big bang universe?", but I can't find it.

Consider a grid of lines in an infinite plane, such that the distance between any two nearby lines is R. Suppose now that that distance depends on time, e.g. as R(t)=kt, where k is just a constant. Now imagine that we are watching this plane while letting t decrease towards 0. Does this give a special significance to any of the points in this plane? Absolutely not. Does R(t) go to 0 when t goes to 0. Yes, definitely.

Think of the big bang as t=0. At any t>0, the plane is infinite. At t=0...well, there isn't really a t=0, because we don't even have a "space" at t=0. So the big bang is not an event in space-time. It's just a name for the limit t ---> 0.

[ksbluesfan]

The search feature of this forum is just unbelievably bad. 90 seconds, wtf!? I'm pretty sure the title of the other thread was "where is the center of the big bang universe?", but I can't find it.

Consider a grid of lines in an infinite plane, such that the distance between any two nearby lines is R. Suppose now that that distance depends on time, e.g. as R(t)=kt, where k is just a constant. Now imagine that we are watching this plane while letting t decrease towards 0. Does this give a special significance to any of the points in this plane? Absolutely not. Does R(t) go to 0 when t goes to 0. Yes, definitely.

Think of the big bang as t=0. At any t>0, the plane is infinite. At t=0...well, there isn't really a t=0, because we don't even have a "space" at t=0. So the big bang is not an event in space-time. It's just a name for the limit t ---> 0.

Does that hold for 3 dimensions?

Sorry, I'm dense. I drove my physics teacher crazy in college.

Edit: Nevermind. It took me a while, but I get it now.

[Fredrik]

Huh? Even if that is the case, the skin of the balloon on the far side is moving away at a different rate than the skin of the balloon on the same side, isn't it?
Yes, it is. If it wasn't, it wouldn't be a very good model of the expansion of the universe, since galaxies that are far away from us are moving away faster than galaxies that are closer.

[ksbluesfan]

Isn't Andromeda moving toward the Milky Way? I'm so confused.

[Tubbythin]

Yes. Because the balloon analogy isn't perfect.

[Fredrik]

That confuses me. If the universe is exanding like a balloon that is being blown-up, there should be a center, right? If our galaxy is at a certain point, some points will be moving in the same relative direction, though still getting farther away, while other points are moving away from us.
The center of the balloon is the big bang in this model. It's not a point in space. It's the limit the universe is heading towards as the time goes to zero. At any t>0, the universe is a sphere, but there's no universe at all at t=0.

[ksbluesfan]

Yes. Because the balloon analogy isn't perfect.

I guess gravity might be a factor as well.

[Tubbythin]

Yup.

[godless dave]

There is also motion going on in addition to the expansion of spacetime; Andromeda heading towards the Milky Way is one example of this motion.

[Hellbound]

ksbluesfan:

The movement of Andromeda is local: it is moving towards us. Think of the balloon analogy again, but instead of thinking of galaxies as being dots drawn on the balloon, think of them as being ants crawling on the balloon. A couple of ants may be crawling towards each other faster than the balloon is expanding; but the overall view would still clearly show the expansion.

Now hopefully that's not more confusing :)

[Fredrik]

Isn't Andromeda moving toward the Milky Way? I'm so confused.
Yes. The galaxies are actually moving on the surface of the balloon (or in the plane I described), at small speeds in random directions. Two nearby galaxies can move towards each other if the random velocity overcomes the expansion, but if they are far apart, the expansion always wins.

Edit: Three people writing pretty much the same thing at the same time...:)

[Tubbythin]

ksbluesfan:

The movement of Andromeda is local: it is moving towards us. Think of the balloon analogy again, but instead of thinking of galaxies as being dots drawn on the balloon, think of them as being ants crawling on the balloon. A couple of ants may be crawling towards each other faster than the balloon is expanding; but the overall view would still clearly show the expansion.

Now hopefully that's not more confusing :)

That's also good because the ants don't expand with the balloon (like the galaxies don't expand with the universal expansion) where as the dots would.

[ksbluesfan]

Thanks for the answers folks. I don't know why, but it's hard for me to get my mind around astronomy and physics.

[Whiplash]

Wait a minute.. so then the Earth is the center of the universe after all! Thiests were right!

Or, for egomaniacs, you yourself are the center of the universe after all. How does that feel?

[~enigma~]

Just a random thought - if we know the universe is expanding - that things in the universe are moving away from each other - do we know the physical location where it all originated? Like, was there a specific point where it all began and expanded away from?

Disclaimer: I may not fully understand the things I am asking. I couldn't find any information on the subject in a Google search.
Technically, I am the center of the universe.

[tomwaits]

All I know is that if there's a bright center to the universe, you're on the planet that it's furthest from.

[Thanz]

I've decided the center of the universe is wherever I am. How do I go about letting everyone know this from now on?
You do realize that your profile has a "Location" field, right? That's how I let everyone know...

[Lanzy]

Sorry folks, but from my son's actions, I'm pretty sure everything revolves around him.

[steve s]

Thanks for the answers folks. I don't know why, but it's hard for me to get my mind around astronomy and physics.

If you think that's bad, wait till you start reading about Membrane Theory and its eleven-dimensional multiverse. I get a headache just thinking about it.

Steve S.

[steve s]

All I know is that if there's a bright center to the universe, you're on the planet that it's furthest from.

Nice to see a fellow Star Wars geek on the board.:D

Steve S.

[portlandatheist]

I would recommend this:
http://www.astronomycast.com/astronomy/ep-77-where-is-the-centre-of-the-universe/

[fuelair]

The search feature of this forum is just unbelievably bad. 90 seconds, wtf!? I'm pretty sure the title of the other thread was "where is the center of the big bang universe?", but I can't find it.

Consider a grid of lines in an infinite plane, such that the distance between any two nearby lines is R. Suppose now that that distance depends on time, e.g. as R(t)=kt, where k is just a constant. Now imagine that we are watching this plane while letting t decrease towards 0. Does this give a special significance to any of the points in this plane? Absolutely not. Does R(t) go to 0 when t goes to 0. Yes, definitely.

Think of the big bang as t=0. At any t>0, the plane is infinite. At t=0...well, there isn't really a t=0, because we don't even have a "space" at t=0. So the big bang is not an event in space-time. It's just a name for the limit t ---> 0.I was about to mention that when I read yours above. you are definitely correct about it being very recent (2-3 weeks) and roughly the title of it! Now, once Search begins working again...... You know though, if you wrote anything in that one you can likely find it by going to your member location.

[Reality Check]

The other thread on this topic is Where Is The Center of the Big Bang Universe (http://forums.randi.org/showthread.php?t=108379).

[G-K-4]

And here is a link to a video by Phil Plait, well-known astronomer and skeptic. He answers this very question in his usual capable way, and made the video quite recently.

http://www.badastronomy.com/bablog/2008/05/02/where-is-the-center-of-the-universe/

[davefoc]

The search feature of this forum is just unbelievably bad. 90 seconds, wtf!? I'm pretty sure the title of the other thread was "where is the center of the big bang universe?", but I can't find it.

...



The search feature of this forum is usually pretty bad. A recent notice said something about it not working at all right now. When I tried it recently it acted like it was searching but didn't find anything. Altogether, a really annoying problem given that it takes 90 seconds before you can initiate another useless search.

Google and maybe yahoo work pretty well to search the forum when you restrict the search to the JREF forum domain.

[davefoc]

And here is a link to a video by Phil Plait, well-known astronomer and skeptic. He answers this very question in his usual capable way, and made the video quite recently.

http://www.badastronomy.com/bablog/2008/05/02/where-is-the-center-of-the-universe/

I watched that video, but as a person who as thought about this for awhile I don't think I learned anything.

He touched on what is one of my thought experiments about this. What happens if you just keep going in one direction? Do you eventually get to places you've been to before. If you don't does that imply an infinite universe?

Another permutation of that question: What does an observer on a galaxy that is 13 billion years away from us see when he looks towards us? What does he see when he looks away from us? Does he see a completely different part of space than is visible to us or does he see some of the space that is visible to us when we look away from him?

OK, one last question here: Are there people that understand the nature of the geometry of the universe or is it just beyond the human mental processes to understand the geometry of the universe?

[Stir]

Don't know if this will help or not:

Picture a universe consisting of a circle whose radius is increasing, inhabited by one dimensional creatures who perceive only the circle (they are unaware of a 2nd dimension). They could be aware of the expansion (every point is moving away from every other point) but the center of expansion would not be in their universe.

Or 2 dimensional creatures inhabiting the surface of an expanding sphere, unable to perceive the dimensions perpendicular to that surface, aware of the expansion, but the center not in their universe.

These two cases we can see clearly since we can perceive 3 dimensions. But now think about 3 dimensional creature (us) on the surface of an expanding 4 dimensionsal sphere (a hypersphere). The surface would have 3 dimensions, and we could perceive correctly that every point is moving away from every other, but the center of expansion would not be in our universe or our sense perceptions. Don't try to mentally picture this case ... it can't really be done by us poor limited 3D folk!

[Stir]

I
Another permutation of that question: What does an observer on a galaxy that is 13 billion years away from us see when he looks towards us? What does he see when he looks away from us? Does he see a completely different part of space than is visible to us or does he see some of the space that is visible to us when we look away from him?

OK, one last question here: Are there people that understand the nature of the geometry of the universe or is it just beyond the human mental processes to understand the geometry of the universe?

First question: they would see exactly the same sort of thing we do: universe that is (relatively) homogeneous in all directions, and looking much the same as what we see.

2nd question: yes, there are people who thoroughly understand the geometry, but only with the aid of mathematical tools. Some people do claim to be able to mentally picture four spatial dimensions (and not just a 3D view of the four) but I continue to believe that that is not actually possible.

[davefoc]

First question: they would see exactly the same sort of thing we do: universe that is (relatively) homogeneous in all directions, and looking much the same as what we see.



That was not exactly the answer to the question I intended. My question was when they look away from us do they completely unique stuff or do they see stuff we can see if we look in the right direction.

If they see completely unique stuff and the people that are 13 billion light years away from them in a direction away from us see completely unique stuff then it begins to sound like a chain that implies an infinite universe. If they don't see completely unique stuff it sounds like the universe curves back on itself in some way.

[Viper Daimao]

I seem to remember some theory that the universe was donut shaped (maybe this was confined to m-theory). So theoretically if you kept going in one direction, could you end up back where your started?

[GreyICE]

About two feet above my chair.

[Hellbound]

About two feet above my chair.

So the center of the universe is a black hole?

;) (Sorry, the set up was too good to pass on!)

[Stir]

davefoc: sorry to have misunderstood your question.

I don't think you can be sure whether what they would see is unique or not in a finite universe ... in a large enough finite universe, they may be seeing things we do not, while in a smaller universe, they might see the same objects but 'from the other side'. Note that it would not be simple to confirm that second case since, among the objects we view from 'opposite sides' the ones they see as most remote (and therefore seeing the oldest light) are the ones nearest to us.

[FramerDave]

Thanks for the answers folks. I don't know why, but it's hard for me to get my mind around astronomy and physics.

Don't feel bad. A lot of astronomy and physics involve numbers that are so incredibly large or so incredibly tiny that it's hard to get a grasp of them. Add to that the weird things that happen at the quantum level and it's a wonder that anyone at all understands it.

I'm just happy to understand what little of it I do and that there are far more brilliant minds out there than I.

That's probably why the woos and religious nutballs have had such success in appropriating them for their purposes.