Center of the Universe?

[Cmac22]

This has been bugging me lately. I was trying to find where the center of the universe is. I was dissapointed to find out that, as far as i have learned, there is no center. I have a little bit of understanding but need some help

 

I remember something about the Big Bang occuring everywhere in space or time or whatever, and that in such extreme environments, the laws of the normal world might not hold, hence the uniform dispersion of heat.

 

I have also read about the "ballon" metaphore used for the expansion of the universe. But it still doesnt make sence to me. If the universe is indeed expanding, in the sence that i understand it is(which may be wrong), then by going back in time it was once infinately small, bringing us to the big bang. so this infinately small whateveryouwanancallit must have been where the universe started, and should still exist?

 

Someone please help me understand, im sorry if i was unclear. there is a lot of mixed info in there and most of it i dont fully understand

[ecoli]

space is relative.

 

Do you want to know center as in the point that is equidistant from the "edges" of the universe? But, if something has an edge, that implies there is space beyond the edge, so does that mean the universe is expanding within a different medium?

[Cmac22]

sorry, im very young and have a very limited understanding. but yes, i suppose i would be refering to the point that is equidistant from the "edges". i dont know if that would imply something beyond the edge. so, are you saying there is no edge to the universe and therefor no center?

i was assuming that, if the universe is 14 billion years old, then light could only travel 14 billion years from whatever point it came from, and therefor that point would be the center and the extent of the light the "edges".

 

i dont care about the exact point of the center of the universe. but as i understand it, one galaxy must be closer to the "edge" or unknown or undiscovered area of the universe, or the area that light has not yet reached. so, if you apply that in all directions shouldnt there be a general central area to the universe, the center of the area that light has expanded out to?

[CaptainPanic]

I'll try to rephrase Cmac22's question (and he should correct me if I did wrong here).

 

At which place in the universe did the big bang take place?

 

After the big bang, everything started to expand, in every direction.

 

It's like a firecracker... the firecracker is the center of its own explosion, but after it exploded the little pieces are all over the place, but they are distributed in a circle (or sphere) around the place where the firecracker originally was.

 

I personally believe that there was space at the moment of the big bang. An infinite space around some sort of mega-supermassive black hole. The big bang was nothing but a black hole which spit out all its matter.

According to my view, there is a center, namely where the supermegamassive heavy black hole was when it blew up. (Sorry for inventing my own words here).

 

Undoubtedly others have a more complex view. I'm a chemical engineer, and I think of the world and universe as a thing you can touch, and as a place which works according to our earthly laws of physics (those laws you can see with your own eyes and feel with your hands).

[ydoaPs]

At which place in the universe did the big bang take place?

Everywhere

[Klaynos]

Everywhere

 

He mentions he's heard that before and was looking for clarification...

[Cmac22]

I'll try to rephrase Cmac22's question (and he should correct me if I did wrong here).

 

At which place in the universe did the big bang take place?

 

After the big bang, everything started to expand, in every direction.

 

It's like a firecracker... the firecracker is the center of its own explosion, but after it exploded the little pieces are all over the place, but they are distributed in a circle (or sphere) around the place where the firecracker originally was.

 

Thank you. yes this is what i was trying to say, and yes i view it similar to the fire cracker.

 

if, as someone else mentioned, the Big Bang happened "Everywhere" then how could the universe be expanding? becuase if the Big bang happened "everywhere"...and it is expanding then there must be somewhere other than "everywhere" for it to expand into, right? and so...if this is the case i guess this "everwhere" would be more or less the center of the universe, and it would be expanding from there? no?

 

if you got ideas on this please put them in, im not gonna be offended.

[Martin]

Thank you. yes this is what i was trying to say, and yes i view it similar to the fire cracker.

...

 

that is not how professional cosmologists view it.

 

here's an illustration from a Scientific American article by one of the world's top observational cosmologists

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p39.gif

 

Links to the whole article (Misconceptions about the Big Bang) and links to four or five other sidebars and illustrations are available here if you want

 

http://www.scienceforums.net/forum/showthread.php?p=384716#post384716

[Cmac22]

Thanks a lot martin. that is what i didnt understand.

[Martin]

...

 

It's like a firecracker... the firecracker is the center of its own explosion, but after it exploded the little pieces are all over the place, but they are distributed in a circle (or sphere) around the place where the firecracker originally was.

 

I personally believe that there was space at the moment of the big bang. An infinite space around some sort of mega-supermassive black hole. The big bang was nothing but a black hole which spit out all its matter.

According to my view, there is a center, namely where the supermegamassive heavy black hole was when it blew up. (Sorry for inventing my own words here).

...

 

That is your own private concept, unlike anything I'd call science.

 

Everybody should be able to make up their own story and believe what they want. But what about the young impressionable people like Cmac who hear some line of baloney and accept it as if it were the mainstream picture?

 

They get misled and it becomes harder for them later on to get their head around the conventional view when they go to college.

 

How about this, Mr. Panic. As you say, you are a chemical engineer and so must know the importance of getting basic science down right---and knowing the standard version of stuff so everybody can be more or less on the same page.

 

How about you study Lineweaver's March 2005 SciAm article which attempts to combat some of the worst popular misconceptions about expansion cosmology (including the bomb or firecracker in empty space picture)?

http://www.scienceforums.net/forum/showthread.php?p=384716#post384716

 

So then, even if you want to go on spreading your own personal ideas it will be clear that they are, from a normal cosmology point of view, misconceptions---running counter to the general professional consensus.

 

don't get me wrong. I don't say the standard cosmology view is true and yours is false, or that opposing views shouldnt be presented. Having an open forum is great. We have a high tolerance for private theories and such.

Maybe the scientists are wrong, and the big bang was like a firecracker in an empty room.

But if you are going to present a fringe picture that is in conflict with the mainstream at least first learn the basics of the mainstream so you know how you are leading the listener away from it.

 

thanks

[Cmac22]

alright. i think im starting to get the idea. but im definatly concidered a beginer in this whole subject. so i have a few questions that i could probably go around serching for the answers to but i have school work to do so help would be nice

 

so....there is no edge to the universe, what does that mean, it goes on forever? and what is it that goes on forever? heres 2 more specifide questions

 

1. is there a point or an "edge" i suppose where there is no more "matter" or whatever past? like no more galaxies and stars, just...space i guess?

 

and 2. if the universe is roughly 14 billion years old does that mean that we can only see things 14 billion lightyears away, and that there might be other things farther away but their light hasnt reached us yet?

 

or is it a combo of the two?

 

thanks

[Edtharan]

so....there is no edge to the universe, what does that mean, it goes on forever?

Yes, as far as we know and according to the models (which match very closely to the observed universe), the Universe has no edge.

 

And, no, it does not mean that space is infinite.

 

To explain better: Where is the edge of the surface of the Earth?

 

In fact, there is no edge of the surface of the Earth, yet, would you say the surface of the Earth is infinite in size?

 

No, the surface of the Earth is not infinite in size, and it has no edge.

 

If the Universe wraps around in on it's self (and not just in a sphere, it could be like a doughnut or other weird shape) then it can be without an edge adn finite in size.

 

Also, at which point in the surface of the Earth is the centre of the surface of the Earth?

 

Again, this is a trick question. There is no centre to the surface of the Earth.

 

No, the surface of the Earth is only 2 dimensional, but the Universe is 4+ dimensions, so these examples will not give you an exact image of how it really is, but if you can begin to understand how a surface of a shpere has no edges, is infinite in size and has no centre, then you are on your way to understanding more about how our universe (appears) to be.

 

:confused:

Now, may peopl do get confused about the above examples and will say something like: "But we know there is a centre of the Earth. And yes, they are right. But...

 

I did not ask where the centre of the Earth is, I asked where the centre of the surface of the Earth is.

 

Actually, lets, use this centre of the Earth mistake and make it right.

 

We know that there is a centre of the Earth. Now, in my examples above, I was only looking at the surface, a 2D simplification of 3D space. Well, there is also a dimension of Time, the 4th dimension.

 

In our example with the Earth, if space is the 2D surface, then we can use the distance from the centre to represent Time.

 

So, if we now imagine that the Earth is infinitely small, then this is the singularity at the start of the Universe. At this point the surface of the Earth would be 0, so there is no space, or we could say that all of space is in the same place.

 

Then as we expand the Earth up, we move forward through Time, and the Universe gets bigger. We call this the Big Bang!

 

Because everything that has expanded all started from the same point, then whatever caused that expansion to start (the big bang) must have occurred at all points after that expansion simply because all the points were all at that point when the big bang occurred.

 

And the next question that everyone asks is: But what is it expanding into?

 

The answer: The future.

 

remember, the distance from the centre is supposed to represent Time, so the Expansion is away form the centre so it must be expanding into time, that is: The future.

[Cmac22]

thanks that helps some. but im still confused, i know the earth metaphor isnt perfect and all but i dont understand how the universe can be similar to a 2D serface like the earth... does this mean that space doesnt go off in every direction, or that if i go far enough one way i might end up at the same point? i know that sounds rediculos but its confusing

 

and i understand the expansion of time part but isnt it also expanding physicly as well? and what does that mean anyways, that simply ratios between point a and b ar farther apart but relative to everything else its all the same? zzz so confusing!

 

===========================

 

another thing i was reading one of the articals Martin posted:

 

"the universe is self-contained. It needs neither

a center to expand away from nor empty space on the

outside (wherever that is) to expand into. When it expands, it

does not claim previously unoccupied space from its surroundings."

 

so how can it expand but not occupy new space? does this man its getting "bigger" in whatever way...yet still the same size or same amount of space????

[CaptainPanic]

Martin, thanks for pointing out that I should have written the phrase "I believe" 2 lines earlier, so that it included my entire post. Apologies for letting a simplified metaphor and an opinion seem like a fact.

 

At least I think I expressed a common misconception so that others knew better what to explain. I think this thread has some good explanations now (although I am certain that they would have been given also without my post).

[thedarkshade]

Cmac, universe has no center, and the strange stuff is that you can put anything or anyone you want in the center!

 

Look at this! it is useful and easy to find out why!

[Martin]

... I think this thread has some good explanations now...

 

I owe you special thanks for putting energy into the discussion and getting the talk rolling. Also my apologies for being short-tempered in this case. I usually manage to be more laid back, I think.

 

General appreciation should go to everybody involved in the lively and thoughtful posting in Astro/Cosmo subforum these days.

 

...

so how can it expand but not occupy new space? does this man its getting "bigger" in whatever way...yet still the same size or same amount of space????

 

there is something nontrivial to understand here and you are right to be asking!

 

also be sure you read the whole article by Lineweaver in the March 2005 SciAm. It is only 4 or 5 pages, if I remember. and has 4 or 5 useful illustrations.

 

There is another pedagogical article about this by four other astronomers just this past year about how the public misunderstands the phrase 'expanding space' and how professionals can communicate expansion cosmology ideas better.

If you like the SciAm article, i can get a link to the new article.

 

I'm glad to talk about it, but I want you to have other sources to rely on.

Astronomers are concerned by popular misconceptions and trying to do something about it. they are realizing they have to be more clear with the words they use to describe the mathematical models.

 

What expands is the metric.

(the metric is the distance function that tells how many million years it will take light to go from one object to another)

 

Einstein GR tells us that distances SHOULD change. It is not in the nature of distance to stay the same unless stabilized by a web of force---we should not expect distances to remain constant.

 

Space is not a substance. Space is a word. It is misleading to say "space expands" because it gives listeners the impression of a substance, like a piece of metal expanding when heated.

What GR deals with is a metric. Only relationship between events is meaningul. Points of spacetime lose meaning in GR (something Einstein himself pointed out as early as 1916).

 

The basic equation of cosmology is an equation about the metric.

 

It is distances that expand.

 

In cosmology there is an idea of something being stationary in the space around it, you can tell if you are stationary for example if the CMB has no doppler hotspot ahead of you and coldspot behind you. then you are stationary with respect to the CMB. Hubble actually discovered the idea of being stationary in the 1930s---even before the Background was observed people would say stationary with respect to the expansion, or stationary with respect to the Hubble flow. The words don't matter, there are various ways to tell when you are stationary with respect to the universe.

 

the Hubble law says that distances between stationary objects increase and the rate of increase (called 'recession speed') is proportional to distance. so it is a percentage expansion. Larger distances expand more.

 

The ultimate justification is the amazing accuracy with which it fits the data.

If you model the universe with Einstein 1915 GR (as specialized by Friedmann and others around 1923) then when a small number of parameters are adjusted you get this amazing fit. And as more data comes in the fit gets better and better.

 

And that involves accepting certain realizations. Like what matters is the metric. the particular form of metric is called Friedmann metric and it changes according to Friedmann equation (1923). It is a simple equation. You can find it in the Astro sticky thread (the reference library of links) or many other places, or just ask for a copy-paste.

Another realization is the model has no boundary or wall to space.

Another is that expansion speeds are larger than c (for any distance 14 Gly or larger)

Another is that the metric can expand without any surrounding metric---it's distances just have to get larger according to the Einstein equation of GR!

Or the simplified Friedmann version.

 

If you picture space as a substance you get all kinds of confusion

[Foolstoe]

I thought a sector was in the center of the universe. I saw a picture of the universe and the middle had a giant big yellow thing in it.

[thedarkshade]

I thought a sector was in the center of the universe. I saw a picture of the universe and the middle had a giant big yellow thing in it.

I think what you have seen seems to be a picture which is often used to show the expansion of the universe, or better say the evolution of universe. I have seen such pics too and they usually progress at one side (which I don't understand)! And the "big yellow thing", I suppose (i'm not sure since I haven't seen what you have) refers to the Big Bang. But one thing you must get straight is that Big Bang was not an explosion, because it is often called the ancient explosion that created everything. So what is Big Bang? Well, it is the creation of everything from nothing all at once!

[Cmac22]

Sorry, i have been sick for a while.

 

alright this stuff (that martin has posted) has helped some. but there are still some unanswered questions, and i apologise. i understand that it is a hard subject to understand and you are doing your best and i appreciate it very much!

 

So, distances between stationary objects, are expanding. and i think, correct me if im wrong, were talking superlarge scale here, stationary objects being galactic clusters. lets see....im forming new understanding right now as im typing so its hard to figure out what i dont understand haha.

 

one quick question about expansion speeds. if distance A gives expansion speed B then does distance 2A give expansion speed 2B?

 

thats kinda leading to my question about something martin said, "expansion speeds are larger than c (for any distance 14 Gly or larger)"

 

is the reason for this the age of the universe? and what does this mean? if things 14 billion lys away are expanding faster than the speed of light does that mean we will never be able to see them?

 

and another thing i still dont understand (and maybe im not supposed to understand just accept) is still about the ?edge? of the universe and the lack there of. if everything is "expanding" in every direction, then the universe must be getting bigger. i dont even know what im trying to ask here since i dont understand heh. i mean, if you looked at the universe as a whole, even though thats not possible since there is no edges (right?) then if you looked the next second, because of expansion, the universe must be the whole +1, in the sence of size.... i guess....

 

i dunno if any of this stuff that i have said/asked makes any sence. i know it doesnt to me haha. i think i need to read up on those other form topics the poll thread martin posted about expansion and so on. but if anyone could help it would be nice i gotta go to class now

[foodchain]

in reply to Cmac22

 

Yes, but in all reality direct observation is a physical process. So if expansion means that its expanding faster then the speed of light this does not for instance in time stop light. So the big question to me is where is the light from the edge so to speak?

 

Maybe its just not around anymore or it has simply not made it to earth for any various reason?

 

For it to have no edge I think would imply that its infinite also. Then again if I understand general relativity at all would that not simply imply just that, motion or that observation is a relative process? In that how can you guarantee distances and time to 100%, I just that what would imply some absolute frame of reference then also?

[Martin]

one quick question about expansion speeds. if distance A gives expansion speed B then does distance 2A give expansion speed 2B?

 

That's right.

In fact that sums up Hubble's law.

which says

v = H D

 

H is the current value of the Hubble constant, estimated to be

71 km/s per Megaparsec

and v is the expansion speed at this moment, and D is the current distance.

 

Whatever the distance to the thing is, today, you multiply that distance by H and you get what the recession speed is, today.

That's actually the correct form of the law. You may hear it paraphrased differently---there are some misconceptions floating around about what it says.

 

do the speed is proportional to the distance

 

it turns out to boil down to one percent expansion every 140 million years.

 

If you solve v=HD for v=c, you get that the distance D is 14 billion LY.

The fact that this resembles the age of the universe is a COINCIDENCE. they are actually two different numbers.

 

this 14 billion LY is what you get if you solve c = HD

for the distance at which recession speeds equal c.

 

============================

thats kinda leading to my question about something martin said, "expansion speeds are larger than c (for any distance 14 Gly or larger)"

 

is the reason for this the age of the universe? and what does this mean? if things 14 billion lys away are expanding faster than the speed of light does that mean we will never be able to see them?

 

It is a coincidence, the 14 billion. Actually light from more than 14 billion LY away can still reach us because of a neat fact which involves the Hubble parameter changing. At first it may be swept back, so to speak, but later (if it hasn't been swept back too much) it will be able to make it.

Lineweaver explained that in a SciAm article.

 

 

 

and another thing i still dont understand (and maybe im not supposed to understand just accept) is still about the ?edge? of the universe and the lack there of. if everything is "expanding" in every direction, then the universe must be getting bigger.

 

it could already be infinite. distances can still increase inside an infinite space.

 

it could also be boundaryless like the surface of a balloon, and still distances in the edgeless boundaryless space could be expanding.

 

you can get confused if you try to imagine getting outside the space we know and looking at the sum total of space as an object, as if you were the great higherdimensional wizard who brought it into being.

 

Since we don't know of any higherdimension surroundings, I think it is better to keep your imagination from an inside perspective. there is only this space. it has no edges. distances increase within it.

anyway that's my advice on how to picture it

[lucaspa]

one quick question about expansion speeds. if distance A gives expansion speed B then does distance 2A give expansion speed 2B?

 

thats kinda leading to my question about something martin said, "expansion speeds are larger than c (for any distance 14 Gly or larger)"

 

is the reason for this the age of the universe? and what does this mean? if things 14 billion lys away are expanding faster than the speed of light does that mean we will never be able to see them?

 

I can't emphasize this enough: go read the Scientific American article! It should be in your public library. If not, PM me and I'll send you a PDF copy of the article.

 

The answers to all your questions are in the article. AFTER you read the article, if you don't understand parts of it and need clarification, then come back and ask your questions. The short answer to your question is: yes, we will be able to see them.

 

 

and another thing i still dont understand (and maybe im not supposed to understand just accept) is still about the ?edge? of the universe and the lack there of. if everything is "expanding" in every direction, then the universe must be getting bigger. i dont even know what im trying to ask here since i dont understand heh. i mean, if you looked at the universe as a whole, even though thats not possible since there is no edges (right?) then if you looked the next second, because of expansion, the universe must be the whole +1, in the sence of size.... i guess....

 

It's difficult to explain these things. Think of being an ant on the earth. All you know is the 2 dimensions of the earth: length and width. Start walking in one direction. Eventually you will go "around" the earth and be back where you started. Does the earth have an "edge" for the ant? No.

 

When we say "space" we mean the 3 dimensions of space (length, width, and height) and time (which is a dimension).

 

We are so used to things happening in spacetime where we are that we have trouble thinking about the universe (all of spacetime) as a whole. What we can try to do for you is give analogies. The universe is like an ant on the earth. The expansion is like a balloon being blown up. But all those analogies are imperfect, because they all happen in spacetime and we get to look from "outside". In the case of the universe, there is no "outside" for anyone to look from.

[Martin]

I think the SciAm article that Lucaspa just referred to is this:

 

http://www.astro.princeton.edu/~aes/AST105/Readings/misconceptionsBigBang.pdf

 

That is a nice PDF version that they have at a Princeton website. Or there is this HTML version at the SciAm website.

http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0009F0CA-C523-1213-852383414B7F0147

 

The article was called Misconceptions about the Big Bang. It was by Lineweaver and Davis, in the March 2005 issue. It had some very useful SIDEBARS giving pictorial diagrams with a question together with right and wrong answers explained. For easier access, here are links to individual sidebars.

 

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p39.gif

What kind of explosion was the big bang?

 

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p40.gif

Can galaxies recede faster than light?

 

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p42.gif

Can we see galaxies receding faster than light?

 

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p43.gif

Why is there a cosmic redshift?

 

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p44.gif

How large is the observable universe?

 

http://www.sciam.com/media/inline/0009F0CA-C523-1213-852383414B7F0147_p45.gif

Do objects inside the universe expand, too?

[Genecks]

This has been bugging me lately. I was trying to find where the center of the universe is. I was dissapointed to find out that, as far as i have learned, there is no center. I have a little bit of understanding but need some help

 

I remember something about the Big Bang occuring everywhere in space or time or whatever, and that in such extreme environments, the laws of the normal world might not hold, hence the uniform dispersion of heat.

 

I have also read about the "ballon" metaphore used for the expansion of the universe. But it still doesnt make sence to me. If the universe is indeed expanding, in the sence that i understand it is(which may be wrong), then by going back in time it was once infinately small, bringing us to the big bang. so this infinately small whateveryouwanancallit must have been where the universe started, and should still exist?

 

Someone please help me understand, im sorry if i was unclear. there is a lot of mixed info in there and most of it i dont fully understand

 

I'm not really sure where the center is. I'm sure we could all make assumptions, theories, and etc. but I'm thinking the human race doesn't know. If any of you could can prove it to me beyond a doubt, beyond 90%, then I might take it into consideration.

 

For now, I will argue consciousness.

 

You are the center of the universe.

 

I'm against doing metaphysical assumptions, but when we're talking theoretical stuff such as shapes, that's because we've come to consider them within our mind. The word "center" can be argued and is a contestable term. I say consciousness, because if the universe infinitely expands, then the middle would be your point of consciousness at all times. It does make solipism seem more like a reality, though.

 

I can't emphasize this enough: go read the Scientific American article! It should be in your public library. If not, PM me and I'll send you a PDF copy of the article.

 

Holmes, I'm pretty sure you're not suppose to be sending PDF copies of the articles unless they are free or you are transferring the rights of your digital copy to someone else. Correct me if I'm wrong, though, because there have been plenty of research documents I've wanted to send to the moderators around here from time to time because they requested information.

[mooeypoo]

Question:

 

I am not sure, but I think we might be better off defining things as "Rapid Expansion" instead of Explosion. It may sound redundant, but I personally think this is a big part of the misunderstanding of the process.

 

I won't lie, I'm not 100% well versed in the Big Bang theory, but from what I've learned and read, a lot of scientific sources make that distinction.

 

I even heard, once, that the analogy is more like "Patty doe" than a 'bomb' -- as if it's a raisin bread patty, expanding simultaneously all over --> more "doe" in between the raisins means, technically, that the individual "raisins" are "moving" apart --> but they're not really MOVING... space expands in between, making the appearance of 'moving'.

 

Okay, my explanation is shakey but.. Martin, you're a physics expert --> is this right? and if so, isn't the definition "expanding" much better than "explosion"?

 

~moo