I was wondering, is the center of the universe located where the Big bang took place? Is it like tossing a pebble in a pond and having the ripples wave out evenly in all directions?

 

In going back through your other posts, I notice a familiar trend.

Allow me to ask whether you have read any of the books or articles suggested previously ... ? If not, I suggest you read either Joseph Silk or Simon Singh on the Big Bang theory. Either would answer the questions you've raised in the cosmology topic areas.

The short answer to your question is "everywhere" ... there is no "center" as in the place in a pond from which ripples flow out after a stone plops into it.

Remember there was no pre-existing "space" for the universe to "expand into" ... there was no pond there for the stone to plop into ...I know it's hard to envision, but that's the theory.

If you assume:

• that the creation of the universe took place everywhere at once
• that it happened as Big Bang theory suggests
• that the universe continues to expand

 then you end up with a view that matches what we see today:

• there does not appear to be a "center"
• from any given point you would see almost all other points receding from you
• the fabric of spacetime itself seems to be stretching
• the afterglow of the Big Bang appears red-shifted into the microwave region

I have skimmed articles from time to time but sometimes it's nice to get a quick answer from the experts. I may check out those authors now that you've mentioned..

I did read in another post that the the Universe is 13.7 B LY in all directions from us. What does this say about a center? It would imply that we are at the center? I know this not to be true. And where is the afterglow located?

It's hard to assume the creation took place everywhere at once when at the time there was NO anywhere.

star_struck:

I have skimmed articles from time to time but sometimes it's nice to get a quick answer from the experts. I may check out those authors now that you've mentioned..

I think you would enjoy them!

I did read in another post that the the Universe is 13.7 B LY in all directions from us. What does this say about a center? It would imply that we are at the center? I know this not to be true.

Yes, from our viewpoint it would appear that we are at the center. However, adopt any other viewpoint and you'd come to the same conclusion. How can this be? This is what you would expect if there were no "center" and every point were expanding away from every other point.

And where is the afterglow located?

It is everywhere, as you'd expect from the Big Bang and expansion. One way to envision it is to think of being in a fog. Since the fog obscures your view, all you know is that there are these little particles of fog everywhere (the afterglow) -- in any direction you look. The cosmic microwave background radiation is the glow of the Big Bang red-shifted into the microwave frequency band.

If you could magically look back toward the moment the universe was created, you'd eventually encounter an era before photons decoupled from the fireball ... beyond that point you'd be looking at an opaque universe (a "fog" of particles and sub-particles so hot and so dense that photons can't escape) ...

It's hard to assume the creation took place everywhere at once when at the time there was NO anywhere.

I agree it's a difficult concept to envision. That is why I suggested you think forward rather than backward: begin with the propositions posited by Big Bang theorists and see what you end up with -- it resembles our current view of the universe very accurately. If you try to think backwards, you inevitably are limited by your pre-existing notion of a cosmic "explosion" (everything moving outward from a central point, as in the more-familiar case of a stick of dynamite exploding). The difference is that IF there was nowhere other than the singularity, THEN if you assume the Big Bang model and move forward in time you will end up with a universe like the one we see. The Big Bang literally created what we see today -- all of it (from whatever "point" from which it expanded).

 

"I did read in another post that the the Universe is 13.7 B LY in all directions from us. What does this say about a center? It would imply that we are at the center? I know this not to be true. "

 

"Yes, from our viewpoint it would appear that we are at the center. However, adopt any other viewpoint and you'd come to the same conclusion. How can this be? This is what you would expect if there were no "center" and every point were expanding away from every other point."

 

did it maybe say the "observable" universe is 13.7B LY?

if the creation event occured 13.7B years ago, then light from any point more distant than 13.7B LY could not reach us by this time.  anything further would hence be unobservable. right?

 

This graphic might help:

It is a "map" generated from a supercomputer simulation of the portion of the large-scale structure of the universe within the set of superclusters of galaxies of which our own Virgo Cluster is a part -- the graphic represents the structure of the universe for 500 million light years centered on our location.

So, from our perspective, this is what we see. Now, imagine moving instantly from the Virgo Supercluster to, say, the Hydra Supercluster. How would the view change? It would look very much the same! Now, imagine that you had such a map for the entire universe ... the change would be very much smaller. This is why it's hard to envision a "center" to the overall universe ... it looks very much the same in all directions.

Not EXACTLY the same, to be sure, but so much the same as to make little difference where you stand when you look.

Another way to think of it is to suppose you have a very large bath sponge (the structure of the universe at large scales is very similar, with matter such as galaxies and stars and dust clouds where the spongy bits are and voids where the "holes" in the sponge are). Forget for the moment that you know anything about how sponges grow -- you just have this very large spongy thing to look at.

Now, how do you find the center? If the sponge is small enough to hold in your hand, it's easy -- well, it's easy to find the "centroid" (the geometric central point), or, perhaps, the "center of mass" (the point at which if you pivoted the whole structure on that point it would not "fall over" if you let it go).

But if the spong is very much larger than you are, how can you tell where the center is?

Furthermore, assuming you can find some "central point" in the mass, how can you tell that it grew from that central point?

This is a lot like the problem we face when we look outward from the Earth at the universe.

The Millenium Simulation Web Site (click here) has some additional graphics and movies that might help you understand, as well.

MoFoYa:

... if the creation event occured 13.7B years ago, then light from any point more distant than 13.7B LY could not reach us by this time.  anything further would hence be unobservable. right?

Yes, that would be the "observable horizon" effect ...

I've always wanted to take a trip through the Universe, now I can but later when I access some big bandwidth. I see your point that we are so small that no matter where we position ourselves, the universe will look about the same. This brings to mind a point or 2. This is true as long as we're not placed on the edge of the Universe akin to the diff of being in the middle of Lake Superior rather than on the shoreline and looking toward the beach. Who can imagine what the edge would look like?  I guess we would be unable to determine the center of Creation since we are part of it and have no frame of reference in observing it from a distance.  Has it been theorized that there is a finite amt of matter? If so, that would mean there would be an edge.

 

Yes. One leading theory holds that the universe is finite, but unbounded ...meaning spatially unbounded (not unlimited as to time). An example of a finite but unbounded surface is a sphere: If you were an ant crawling on the surface of a sphere (inner or outer), you would never reach an edge.

So, if the "outermost region" of the universe were strongly curved, you could never reach an "edge". This is rather difficult for us to imagine. It's something like the curvature of space being so "strong" in the vicinity of a black hole that you (or light) couldn't crawl out of it. What happens to time in that case? Black Hole theory states that time stops for an observer beyond the event horizon (although the observer can't exist in his/her former condition at that point, much less "report" any such condition to observers outside the event horizon). Still, a force strong enough to "blast" the universe into existence certainly could provide enough energy to warp space at its boundaries ... so I suppose it's possible.

However, since we can't physically reach the boundary, it should forever remain beyond our grasp or view.

Another problem with conditions at the edge is that if matter as we know it (atoms, elements, molecules, etc.) did not exist in its current form for some considerable time after t=0, then the "outward edge of expansion" would be in some weird state we can only guess. So, following the earlier analogy about what we'd see if we could "look back" toward the beginning, the forward-most edge of the universe might be something like that cosmic fog, or "quark soup" -- only cooled well beyond its original temperature. What that would be like I cannot imagine. Perhaps, like the quantum effect which allows subatomic particles to come and go "as they please", any particles "out there" would have dissipated into nothingness (whatever "the other side" of the quantum universe" might be ...). Whether that would "leave behind" any afterglow of spacetime is not something I can answer.

I'm going to change the ant on a sphere (Thanks, chipdataJeffB!) to an amoeba on a ping-pong ball.  The amoeba can crawl all over the entire surface of the ping-pong ball, but it will never encounter a center or an edge to that surface - because there is none.  Now if you make that ping-pong ball inflatable and start inflating it, that helps give an idea of how the surface can expand all over at the same time without there being any center to the expansion, nor any edge.

The big difficulty with this analogy is that the surface of the ping-pong ball is a two-dimensional analogy applied to a three-dimensional space, and it is therefore inherently limited.  If you think about the third-dimensional center of the ping-pong ball, you're cheating.  You have to think only of the surface on which the amoeba can crawl.  For us, all three dimensions of space are expanding, with the expansion having no edge and no center.

Ed Cannon - Austin, Texas, USA

The ant or amoeba has another problem, but the analogy still works:

• If they are able to determine there is a depth, or thickness, to the surface and can get in there and measure and/or observe (the ant can burrow and the amoeba can float/swim), then they'll be able to find the third dimension.
• However, there will be a "horizon" in that direction (two actually, one for each surface).
• If the surface plus its thickness is their whole universe, they won't be able to sense anything beyond the horizons (toward or away from the direction of expansion of the sphere). Looking outward, they would encounter nothingness; looking inward they would encounter a "boundary" which we see as the cosmic fog of the Big Bang -- beyond which we can't see because that boundary is opaque.

The fog analogy is better because it simulates our situation more fully: when we're "in" the fog we can see the individual bits nearest us, but we can't determine the overall shape of the fog from its droplets and we can't see beyond it because it's opaque. Now, imagine you have two areas of fog: the one you're in is relatively transparent and you can see through it to notice bits of the other area, which is very opaque. If the opaque area is "further back in time" then theoretically anyone in any part of the transparent area can see back to it, but not through it or beyond it.

In such a case, you can tell that your lookback time can give you a "distance" from the opaque fog boundary, but you can't convert that to an age of the universe based solely on observation (since you don't know how much fog lies beyond what you can see). But, if you can make assumptions about its composition (based on your knowledge of physics, particularly nuclear and quantum physics, you can extrapolate backwards in time from that point and at least estimate conditions within the fog at various times based on its expansion rate.

When cosmologists probe the earliest eras of the universe, they do exactly that: they run computer simulations backwards in time to determine where parameters are needed, they estimate those parameters, then run the simulations forward in time to find out whether the universe that results matches what we see today.

The main problem with these analogies is they involve our having some kind of model we can hold in our hands and look at from outside. We can readily envision ourselves in any particular location within that model we want to choose. That's not the correct way to think about it because we can infer a direction in space from which the expansion is proceeding. Instead, we must think about a direction in time only (since we can't tell from observations which is the "correct" physical direction to "look").

I like the sponge analogy because it mimics the structure we actually can map, and because if we're an observer within the sponge we can't hope to identify the "beginning point" or any "edge" as "special" -- and that mimics reality.

That's a great graphic of the universe out to 500 M light years, I've never seen that one before.  I rather like the fog analogy also.  I rather think the inflationary expansion of the universe continues apace in regions that we will never directly experience.  I sometimes think the universe before the big bang was a sort of supercooled state, and at the moment of the big bang this fog that is us and all that we see around us dropped out of the supercooled state to become what we experience as reality, and that this process still continues...   

Sometimes I think the big is bang like one of those carnival tricks where the lady climbs into a coffin filled with dynamite, closes the lid, and sets it off.  I realize the explosion analogy is not a good one, but you can bet as far as the lady is concerned the explosion took place everywhere all at once.  

"Where did the Big bang take place?"

In your mind. The universe is IN YOUR MIND

 

In talking about being on the edge, or boundary of the universe, kind of like being on the edge of a shoreline, you also have to take into account it's growth rate. How quickly is the universe expanding? From our point of view the lake is expanding faster than the fish can swim. The expansion rate is very fast. The further away we look the faster that objects appear to be moving away from us, as the whole universe is continuing to expand. This brings us to a secondary type of horizon. One in which objects are expanding away from us at faster than the speed of light. This second type of visual horizon is very close to the distance that our observable horizon is at. This rate of expansion continues to increase with distance, which is why they say that the most distant objects we can see from 13 or so billion years ago, are now about 47 billion light years away. Let's say that the universe is 150 plus billion light years across and expanding. How quickly is it's boundary expanding? It is expanding at much faster than the speed of light. Because of it's speed then, we would not be able to determine it's edge, as we cannot see anything traveling at faster than light speed. It's sort of like saying that Guth's hyper inflation at the very beginning of the Big Bang never really stopped. It's just that as the universe continued to expand, the smallest regions inside the universe continued to slow in their growth and to fall to speeds below the speed of light, and these regions grew over time. Hyper inflation is still be happening.

The big bang didn't happen somewhere in the universe.

 It's more like the whole universe coming into existence at the same time.

 

Does that answer your question?

 I have never been able to get a satisfactory answer either but I will give you my view as I understand it and maybe somebody can put me right.

 When we talk about speed of light it is often thought about as being similar to the speed of sound. With the speed of sound if you see two blocks being clapped together the sound takes say one second. If you see them being clapped and head away from the sound it will take longer for the sound to reach you. If on the other hand someone fires a laser at you it will not take longer for the light to reach you if you move away. In fact you will not be struck more quickly if you move towards the laser.

This effect means that everywhere appears to be at the centre of the universe. I have heard people state that there is a part of the universe that we cannot see (not the outerverse the meaning of which is in my other post/s). I have to assume by this that the mean light that has not yet reached us but which is of late production ie comes from in excess of half the way through the life of the universe.

I am sure someone may put me right but this is my working assumption.

Ed Joyce

 

 

 

 

Light and sound do behave in similar fashion.    The further away you are from it's source, the longer it takes to reach you.  Light from our sun takes about 8 minutes to reach us, and it would take less time if you were on Mercury.   It takes time for light to travel.   How much time do we have to look with?  If the universe is about 13 billion years old, then that means that we will only be able to see light that is at the most, about 13 billion years old.    We don't know where the center of the universe is, because it is so big.  We cannot see all of it, and light from farther than 13 billion light years away has not had time to reach us.  This is a very simplified explanation, and there are other reasons for our not being able to see farther, but this reason is still a very valid one. Where did the Big Bang take place?  Picture a pipe at the bottom of an ocean.  Now picture that at one time in the distant past, there was no ocean.  There you are standing in a dry deep desert.  Now somebody has turned on the water and you are standing and looking at the very birth of this new ocean.  When the ocean was big enough, and safe enough then that same somebody, put some fish in there.  Some of the fish were smart.  They said.  "Hey this ocean looks new."  One fish looked down and saw the pipe, and then he asked.  "Hey, what part of this ocean do you think was once in the center of that pipe?" Answer.  It all was.  Everything around us.  This galaxy, that galaxy, and all of the other galaxies came out of the Big Bang, or the creation of the universe, however you want to put it. If all of the universe swelled from that one small beginning, then how about now?  Is there a center to our universe now?  Is there a center point to the oceans?  There could be depending on how you want to define "center".  Maybe there is a center to our universe, but we are like the fish.  We're not going to find it any time soon.  We just can't see enough for right now.

Standby. Incoming spanner.  Ok guy's, how long is it going to take before everyone stops following the sheep? Use your inner mind and instinct. Tune in to the cosmos if you can. You can not get something from nothing. Something can not dissapear. Time can not start or stop, speed up or slow down, because time does not exist. Time is our perception of change. Nothing more, nothing less. We use that perception to calculate. The universe, that is to say everything that exists, is infinite and alway's has been and alway's will be. It has alway's existed. The Big Bang is a theory, repeat. A Theory, for people who have a difficulty with infinite. The universe is not expanding. Black holes do not exist. Wormholes? Rubbish. Space curving back on itself? I've never heard such a load of crap. If you start with an untruth theory, you have to think up more untruth theories to relate to the first. Lies begat more lies. The truth is they can't even calculate the dimensions of a sphere or a circle. A digital mathamatical system is inherently flawed. The universe is anologue.

The truth is within all and through all. I wish you all in understanding all that is true.

dalli:

... You can not get something from nothing. Something can not dissapear.

How then to explain what is happening when we observe particles appearing and disappearing in accelerator experiments.

Time can not start or stop, speed up or slow down, because time does not exist.

You could hardly call Einstein a sheep-follower, yet he explains time-dilation effects in relativity (at relativistic velocities). These not only exist, they have also been measured.

... The universe, that is to say everything that exists, is infinite and alway's has been and alway's will be. It has alway's existed.

There is no empirical evidence for the above assertions. It seems to be a reasonable conjecture, but there is no hard evidence for it.

The Big Bang is a theory, repeat. A Theory, for people who have a difficulty with infinite.

A scientific theory is not just someone's crackpot idea: it's one or more hypotheses that are testable, that have been tested, and that have been demonstrated to work by passing those tests. The Big Bang Theory is our current standard model because it has been tested and verified and/or modified for many decades, surviving scientific rigor to reach its current state. Is it perfect? Hardly. Is it "good"? In the scientific sense, Yes. It is the best we currently have.

The universe is not expanding.

Where do you get that idea? There is empirical evidence to support it, going all the way back more than 50 years. The evidence is that not only is it expanding, but that also its expansion is accelerating.

Black holes do not exist.

Well, something very, very massive lurks at the center of the Milky Way. Stars orbiting this object -- which is invisible at X-ray and infrared wavelengths -- which is quite a range! -- do so in periods measured at less than a decade or two. How else would you explain that? Let's see: the object is very massive (hundreds to thousands of solar masses), it is very compact (apparently not more than a few solar radii), it is invisible at every wavelength we've tried, and it dramatically affects the orbits of nearby stars. Sounds like the description of a black hole to me!

Wormholes? Rubbish.

Okay, I'm sorta with you there. Seems fantastic to me. Although particle physicists may actually demonstrate them with the LHC soon (or not).

Space curving back on itself?

Why not? It would explain much about black holes. It works mathematically, even though it's hard to envision. I'm open-minded about it.

... The truth is they can't even calculate the dimensions of a sphere or a circle.

What? You lost me.

A digital mathamatical system is inherently flawed.

So, computers don't work, either?

The universe is anologue.

We'd like to think so ... of course, how then to explain some of the behavior of photons and other particles?

Sorry if I seem combative, but throwing a spanner is apt to provoke such a response.

dalli:

The truth is they can't even calculate the dimensions of a sphere or a circle.

whats this?

A three-dimensional figure with all of its points equidistant from its center.

Radius: r      Diameter: d      Surface area: S      Volume: V           S = 4 Pi r2 = Pi d2           V = (4 Pi/3)r3 = (Pi/6)d3