Starship Asterisk*

Maybe we have just located the Center of the Universe ?

I have always imagined that if Big Bang occurred, then all matter would depart the center in a spherical shape and thus leave a void behind so that in fact the Universe would be a hollow sphere ! ..................and that we are located in some part of the shell ,,,,,,or were there some secondary Bangs also ? 8)

Brian in Fife

I'm not sure "matter" is what banged at the big one, at least not immediately, but the question is interesting. Where are all the cosmologists? We want opinions!

brianclark wrote:Maybe we have just located the Center of the Universe ?

I have always imagined that if Big Bang occurred, then all matter would depart the center in a spherical shape and thus leave a void behind so that in fact the Universe would be a hollow sphere ! ..................and that we are located in some part of the shell ,,,,,,or were there some secondary Bangs also ? 8)

Brian in Fife

Cosmologists are of the opinion that there is no center and no edge to the universe and that the term "Big Bang" is misleading and confusing to lay people. It gives people an impression that the universe came into existence in an explosion, hence there should be a center of the explosion. I am having a hard time trying to visualize how the universe could come into existence without a center. The best I can come up with is a sheet of infinite size that suddenly popped into existence and expanded outward, but this would still give the universe two edges.

Oh, my aching head...anyone got a better idea?

You cannot use general physic or general relativity to create a visual representation of the history of the universe. Space/time is interdependent to mass/gravity in our four dimensional universe - no mass, no gravity = no space, no time. Prier to the BB there was no mass, equating to, no time.


The description I use to help visualize the "edge" of the universe (in 4D) - it is a single point that take forever to cross. There is no space, time, mass or gravity at the universe's end.

The universe became transparent (visible light) when it was 10^6 years old, the dark patch is in an area much younger.

Regarding Brian's suggestion that the hole in the universe is actually the center of the universe, I would have thought the the big bang would have eventually resulted in enough turbulence and diffusion, that after 13.7 billion years, some galaxies would eventually fill in the void, or at the very least, blur the edges of the void.

According to an article by Robt Britt (http://www.space.com/scienceastronomy/m ... 40524.html) apparently space expanded (inflated) rapidly after the big bang to create a universe that has an astonishing "diameter" of somewhere between 78 and 156 Gly (billion light years). Our galaxy is located somewhere in this "diameter" but we have observed objects only within a 12 Gly bubble nearest to us. There really is not enough information available to say with any accuracy whether the big bang occured within our observable bubble. Statistically, it did not, so we would have no way of observing the big bang. It would be outside of our observable horizon. And we have no basis to comment on whether we are at the center or the edge of a 156 Gly universe.

Our observation point from earth is even further distorted by the fact that as we peer around our bubble, we cannot see the present state of affairs, but only the state of objects in the past. So even within our 12 Gly bubble of observation, let us say we spy an object 5 Gly away. We are seeing it as it was before our solar system even existed, and have no way of finding out about it's fate today.

starnut wrote:Cosmologists are of the opinion that there is no center and no edge to the universe

That is mainly based on the Cosmological Principle: "On large spatial scales, the Universe is homogeneous and isotropic".
This 'hole' seems to challenge that.

starnut wrote:Cosmologists are of the opinion that there is no center and no edge to the universe and that the term "Big Bang" is misleading and confusing to lay people. It gives people an impression that the universe came into existence in an explosion, hence there should be a center of the explosion. I am having a hard time trying to visualize how the universe could come into existence without a center. The best I can come up with is a sheet of infinite size that suddenly popped into existence and expanded outward, but this would still give the universe two edges.

Oh, my aching head...anyone got a better idea?

Cosmologists don't say that the Universe has no center. What they say is that the Universe has no three-dimensional center. I find that the famous balloon analogy is a big help. It considers the view of 3D universe as seen by 2D creatures. From our viewpoint, the balloon is a 3D object with a center. Its surface expands outward from that center. But for 2D creatures living on the balloon, there is no center. "Up" and "down" are not directions they can perceive. To them, they are living on an infinite surface. If they travel far enough in one direction, they come back to where they started. They can even do clever experiments, such as measuring the summed angles of triangles, and figure out that their universe is spherical in 3D. But they can still never see its center.

To see the center of our 4D universe, you'd need to be a 4D creature living outside of it. As 3D creatures embedded in our 4D universe, we only see the surface- a 3D section. The "center" lies in a direction that we can't perceive, but which we can understand mathematically. We can do the same sort of triangle measuring experiments to figure out the 4D shape- in fact, such experiments are planned (they need to be done in space, over vast distances).

The shape of the Universe shouldn't be confused with the shape of the observable Universe. The latter is spherical in 3D, and has a center- the observer. We are each the center of our own observable Universe.

I guess I understand the 4D universe concept as well as anybody, which is to say zero equals zero. I am very suspicious of any concept not based on observation, and this one is by definition not observable.

And the Big Bang is based on the assumption that only gravity powers the universe. As soon as you consider any other force that might be in operation the Big Bang concept no longer applies.

SmartAZ wrote:I guess I understand the 4D universe concept as well as anybody, which is to say zero equals zero. I am very suspicious of any concept not based on observation, and this one is by definition not observable.

I guess it depends on what you mean by "observable". By your definition, perhaps you don't believe in electrons, quarks, or even other galaxies. These are all observed indirectly. Likewise for the geometry of the Universe. It is described by General Relativity, a theory that accurately predicts many, many things (all observed in one manner or another).

It can be a real challenge to figure out if something has been observed or not. It is very common to compute what something ought to be and then go looking for it. There is a very real tendency to see what you are looking for even if it's not really there. And after seeing this face in the clouds there is a tendency to apply the same process to compute something else that you can't actually see.

This process sometimes fails the first time you actually see something. The first clue that this has happened is usually a line in a news story like "Scientists were stunned" or "Nobody expected that." At that point we must make a decision. Some people decide to defend their assumptions and they make up ever more fanciful explanations for what they see. Some decide to make up some new math process that may or may not relate to reality. And some decide to do whatever will get them a research grant.

Hello All

Matter in the universe tends to cluster together and in so doing you will get great voids.

Personally I hold the opinion that gravity is an observed effect of perturbations in the time continuum. Time is slowed by concentrations of mass. Mass, in turn, tends to concentrate because of gravity, with matter tending to fall into "time wells" where time passes more slowly. Does time utterly stop, or even reverse, in a black hole? Conversely, does time run fastest in a cold, empty area in space with the littlest possible mass concentration? Is time perturbation resposible for gravitational lensing?

One of these days I'll get my head around this.

Perhaps we are all part of some grand computer simulation, and the processing becomes more intense where there is a concentration of mass so that the simulation runs more slowly.

Knock knock, Neo.

-Noel

Here is one example of an observation that disproves a common notion.

Many people speak of space "curving back on itself" somehow. If there were any such effect we would see every star in the universe in every direction we look. In other words, space would be uniformly white. We observe that space is uniformly black beyond the stars we can see. So space does not curve back on itself. (It also does not go on forever. Or at least there is a limit to the number of stars out there.)

SmartAZ wrote:Here is one example of an observation that disproves a common notion.

Many people speak of space "curving back on itself" somehow. If there were any such effect we would see every star in the universe in every direction we look. In other words, space would be uniformly white. We observe that space is uniformly black beyond the stars we can see. So space does not curve back on itself. (It also does not go on forever. Or at least there is a limit to the number of stars out there.)

That observation proves nothing of the kind. It is possible that the Universe itself is smaller than the visible Universe, in which case what we see in one direction would be similar to what we would see in the opposite direction (i.e. space curved back on itself). CMB measurements have mostly, but not 100% ruled out this possibility. And the fact that we don't see a uniform white background doesn't mean the Universe doesn't go on forever, nor that there can't be an infinite number of stars. Regardless of the size of the Universe, we don't see every star because the finite age of the Universe limits the number we can possibly see. The fact that the sky is mostly dark is observational evidence in support of the Big Bang, and therefore also in support of a four-dimensional Universe.

It is possible that the Universe itself is smaller than the visible Universe,

Say what? That didn't come out right. What was that supposed to say?

SmartAZ wrote:Here is one example of an observation that disproves a common notion.

Many people speak of space "curving back on itself" somehow. If there were any such effect we would see every star in the universe in every direction we look. In other words, space would be uniformly white. We observe that space is uniformly black beyond the stars we can see. So space does not curve back on itself. (It also does not go on forever. Or at least there is a limit to the number of stars out there.)

Space "curving back on itself" is a 3D analogy for a non-3D solution. Regardless which direction is traveled in a straight line, the "termination point" will be at the end of the universe - a single point where space/time no longer exists. Quite like an inverted singularity. Because I don't believe in infinity, the "end of the universe" would be one Planck Length (1.6 ^ 10−35 meters) that would take a photon 46B years to cross.

SmartAZ wrote:

It is possible that the Universe itself is smaller than the visible Universe,

Say what? That didn't come out right. What was that supposed to say?

It was supposed to say just what it did. The actual Universe can be smaller than the observable Universe. Sounds odd, but nothing in theory precludes it. If, in fact, it's true, then we should see photons from some distant objects mirrored on opposite sides of the sky. That's because if the Universe is smaller than the observable Universe, there will have been enough time for some light to have made it across and to wrap around and reach us.

Researchers have looked for this mirror image effect, mainly in CMB data, but also I think with a few quasars. It hasn't been seen, leading most to believe that the Universe is bigger (probably much bigger) than the observable Universe. But the matter hasn't been conclusively settled.

starnut wrote:Cosmologists are of the opinion that there is no center and no edge to the universe

At least some cosmologists are also of the opinion the universe is expanding. That would imply to me that everywhere in the universe is receding from ??? the center of the universe ???

Dr. Skeptic wrote:Because I don't believe in infinity, the "end of the universe" would be one Planck Length (1.6 ^ 10−35 meters) that would take a photon 46B years to cross.

I understand that the classical concepts of gravity and space time cease to exist at distances this small, but Planck Time (the time reqired for one photon to cross a Planck Length) is defined as 5.3912×10-44 seconds not 46B years.

bystander wrote:At least some cosmologists are also of the opinion the universe is expanding. That would imply to me that everywhere in the universe is receding from ??? the center of the universe ???

That's true. But the center is a point in spacetime, not a three dimensional point that we can observe. There is no center or edge to the three dimensional universe, anymore than there is a center or edge to the circumference of a circle that is expanding in diameter. If your universe is that circumference, you can figure out that it is expanding even though you can never see from where (except mathematically).

bystander wrote:

Dr. Skeptic wrote:Because I don't believe in infinity, the "end of the universe" would be one Planck Length (1.6 ^ 10−35 meters) that would take a photon 46B years to cross.

I understand that the classical concepts of gravity and space time cease to exist at distances this small, but Planck Time (the time reqired for one photon to cross a Planck Length) is defined as 5.3912×10-44 seconds not 46B years.

Relativity! If the photon has eyes, it would take 5^-44s to "cross" (quantum mechanics makes it more of a jump) the Planck Length. As an observer relative to the Earth, it would take the entire distance of the expanding universe (46 billion light years) for that photon to make the quantum jump.

eg - To an observer approaching a black hole or a singularity, their rate of time relatively decreases . To an observer approaching the edge of the universe (no gravity) the rate of time approaches ∞. From time relative to Earth where we see the universe as 46 billion light years across, and, where space/time ends (lets say as a single point), space≂ 1/∞, and time≂∞.

But the center is a point in spacetime, not a three dimensional point that we can observe.

That is where the disconnect occurs. I took a science class once and they taught me that step #1 of the method was, "Observe a phenomenon."

Because of the warping (and creating) of space/time by gravity, plus the effects of relativity, all points in the universe are of equal distance to its edge.

SmartAZ wrote:

But the center is a point in spacetime, not a three dimensional point that we can observe.

That is where the disconnect occurs. I took a science class once and they taught me that step #1 of the method was, "Observe a phenomenon."

Precisely. We have observed the structure of the Universe, and developed a theory that explains what we see. GR fits the bill beautifully, and has held up to many independent tests.

Good science doesn't depend on directly observing everything. There are lots of things we have never observed, such as the electron shell structure of atoms. But, like the geometry of the Universe, we observe other things that let us make inferences about things we can't see directly.

Chris Peterson wrote:Good science doesn't depend on directly observing everything. There are lots of things we have never observed, such as the electron shell structure of atoms. But, like the geometry of the Universe, we observe other things that let us make inferences about things we can't see directly.

Correct. The problem arises when we start to think those inferences are basic principles, forgetting that someone made them up. For example, curved space is only needed to explain an expanding universe, which is based on the hypothesis that red shift directly relates to distance, which is based on some assumptions about brightness and sizes of observed stars. If those assumptions were wrong then the hypothesis is wrong, the universe is not expanding, and space is just the way it looks. But the red shift/distance thing is now regarded as a basic principle so the underlying assumptions and hypotheses are not examined much any more.