Where is the center of the universe?

[ynot1]

Dave, I say that things are difficult to imagine, but I never intended to be understood that I doubt its existence. For me the two are separate. I just can't imagine anything infinite.

Actually the biggest reason I have for suspecting the Universe is spatially finite is that it is temporally finite. Again no proof just a hunch.

Good hunch I believe. As I recall Einstein the finite unbounded universe is fundamental to relativity.

 

[Tanelorn]

When I try to visualize what a finite Universe would look like I see something like this except 10^30 times the size of our observable universe.
The vast voids between clusters of galaxies are somewhat represented as well as a spatial void beyond.
I think many cosmoligists also visualize a finite Universe as one in which the large spatial dimensions curve back around on themselves


http://www.wikinfo.org/upload/0/0a/Crab.nebula.arp.750pix.jpg

 

[ynot1]

I'd argue that science is no better position than imagination regardless of how either are compiled.

Infinity is, itself, a millenia old imagined concept.

Humbling. Certainly science, particularly cosmology, is an aid to our imagination, as well as our earthly endeavors. That is we can use it to test our ideas. Some philosophers, maybe what they call relativists, argue that the universe exists only in our perception of it. So the more telescopes or other space probes we build the larger the universe becomes.

 

[Tanelorn]

OK I would like to remove all instances of imagine from my posts on this thread and instead use terms like visualize.
I agree that infinity cannot be visualized - except by a mind of infinite size taking an infinite time! Other good words are thought experiment, postulate, speculate, premise, conjecture etc.
Terms like imagination are not very acceptable even if you are using a little!

 

[ynot1]

OK I would like to remove all instances of imagine from my posts on this thread and instead use terms like visualize.
I agree that infinity cannot be visualized - ecept by a mind of infinite size taking an infinite time! Other good words are thought experiment, postulate, speculate, premise, conjecture etc.
Terms like imagination are not very acceptable even if you are using a little!

There's a strange story about this. Imaginative mathematicians actually deal with infinities as at http://en.wikipedia.org/wiki/Hilbert's_paradox_of_the_Grand_Hotel. Now actually there's a gentleman named Hilbert who owned a huge mansion bought by the Lucas Oil Stadium family. Complete with a replicated IU gymnasium. It was on the market for years until Lucas picked it up for a song - about $3.5 million.

 

[Tanelorn]

Well I thought you or the others were having a dig at me for using the term imagination in a science related discussion.

I don't think I would want to manage a Hilbert's grand hotel, it would mean an infinitely bad headache every time a new guest walks in. Is the Universe actually a Hilbert Hotel? Its giving me a headache :)

 

[ynot1]

Well I thought you or the others were having a dig at me for using the term imagination in a science related discussion.

I don't think I would want to manage a Hilbert's grand hotel, it would mean an infinitely bad headache every time a new guest walks in. Is the Universe actually a Hilbert Hotel? Its giving me a headache :)

I'll admit it would have to have a rather large parking lot. But I don't think the universe is really infinite like a Hilbert hotel. More like finite unbounded. Maybe a regular hotel with no borders around it? <[:>)]

 

[Tanelorn]

Its all good.

This JWST should help answer a few questions and maybe raise a few more.
I discovered this FAQ which shows how well it is expected to perform. Just have to still be around in 5-10 years to see the results:

http://www.jwst.nasa.gov/faq.html#howlong


I wonder if a future successor to the JWST might benefit from being beyond the solar system completely?

 

[ynot1]

OK I would like to remove all instances of imagine from my posts on this thread and instead use terms like visualize.
I agree that infinity cannot be visualized - except by a mind of infinite size taking an infinite time! Other good words are thought experiment, postulate, speculate, premise, conjecture etc.
Terms like imagination are not very acceptable even if you are using a little!

Terms like imaginary, as in imaginary numbers, do seem to get into the lexicon.

 

[Drakkith]

I wonder if a future successor to the JWST might benefit from being beyond the solar system completely?

Other than reduced heating by the sun, which is worked around by cooling the telescope, I don't really see any benefit. It would be far more expensive to send it beyond the solar system than to just load it up with coolant. Plus once it's beyond about Mars or Jupiter solar panels are no longer an effective means to provide power, meaning you need an Radioisotope Thermoelectric Generator. Also you would have to increase the size and power requirements of the antennas in order for the signals to be sent and received between Earth and the telescope.

 

[phinds]

So the more telescopes or other space probes we build the larger the universe becomes.

So you think if we build more and bigger and better telescopes, the observable universe will become bigger? Or is it that the entire universe will become bigger? I don't get how our building telescopes has any effect on either.

 

[Drakkith]

So you think if we build more and bigger and better telescopes, the observable universe will become bigger? Or is it that the entire universe will become bigger? I don't get how our building telescopes has any effect on either.

I think he means that in the view of whatever philosophers he was referring to, the more we see the more exists. Not in the sense that the diameter of the observable universe becomes larger, just in that the more we look at the more exists and the more detailed it becomes. But this would raise a million more questions in my mind, so I don't agree with it.

 

[Genx63]

first you say the universe spread out from a single point and then you say that point don't exist. I don't buy the balloon analogy. That would indicate that all matter is spreading out on a 2 dimensional plane. When a star goes supernova does the star all of a sudden not exist? Why is everyone so dead set against a point of origin for the universe? Maybe it's because it would punch too many holes in your theories. I'm no genius I'm not even very smart but even your balloon theory has a center.

 

[minio]

Balloon analogy is called analogy because it is not exact description. For start try to imagine that balloon has 3D surface and its expadnig in 4D space.

 

[Spourk]

first you say the universe spread out from a single point and then you say that point don't exist. I don't buy the balloon analogy. That would indicate that all matter is spreading out on a 2 dimensional plane. When a star goes supernova does the star all of a sudden not exist? Why is everyone so dead set against a point of origin for the universe? Maybe it's because it would punch too many holes in your theories. I'm no genius I'm not even very smart but even your balloon theory has a center.

Do a google search for Hypersphere. You're not quite grasping the balloon analogy the way it's meant to be presented, if you are still trying to say there is a center of the balloon. A hypersphere is a little easier to look at and see how you can actually travel and never reach a center, or an edge, it just keeps looping back on itself in higher dimensions.

Try this thought experiment: If you were 1 dimensional, and lived on the outside of a circumfrence of a circle, where would the center be? As a 1 dimensional being, you can only traverse the line on the outside of the circle, you'd never be able to reach the "Center" because that is in the 2nd dimension. You could go forward, or back, nothing else. Where is the center?

That being said, how well did the "Earth is the center of the universe" theory work out for Cosmology?

(Forgive me if this has all been presented to the OP already)

 

[Drakkith]

first you say the universe spread out from a single point and then you say that point don't exist. I don't buy the balloon analogy. That would indicate that all matter is spreading out on a 2 dimensional plane.

Of course. That's why it's and analogy. Extrapolating the same principles into 3 dimensions instead of two would give us a hypersphere. Currently the standard model doesn't care whether we are on an actual hypershpere or not, it simply says the universe is expanding.

When a star goes supernova does the star all of a sudden not exist?

The material that made up the star still exists. Whether you could call it a star or not is debateable.

Why is everyone so dead set against a point of origin for the universe? Maybe it's because it would punch too many holes in your theories.

You are correct. A point of origin for the universe would be a big glaring hole in our current model of the universe. A model which is the best fit to observations and theoretical work by far. Punching holes in the theory is akin to not believing gravity exists and saying that fairies hold everything together. You would have to make up stuff that isn't even observable in both cases.

I'm no genius I'm not even very smart but even your balloon theory has a center.

It isn't a theory, it's an analogy. A way to visualize and a tool to help people understand the basic concepts. Don't take it for more than it is. Arguing against it is like arguing that students shouldn't start learning physics with blocks sliding on frictionless surfaces because they don't exist. They do that because it's easier to learn the basics that way.

 

[ynot1]

So you think if we build more and bigger and better telescopes, the observable universe will become bigger? Or is it that the entire universe will become bigger? I don't get how our building telescopes has any effect on either.

Yes the observable universe becomes bigger. Point being you can observe more with better telescopes. Why would the universe get bigger, except for expansion?

 

[Drakkith]

Yes the observable universe becomes bigger. Point being you can observe more with better telescopes. Why would the universe get bigger, except for expansion?

The observable universe wouldn't increase in diameter no matter how many telescopes we built or how big we built them. We simply can't see past a certain point because there isn't anything to see.

 

[ynot1]

The observable universe wouldn't increase in diameter no matter how many telescopes we built or how big we built them. We simply can't see past a certain point because there isn't anything to see.

Certainly. I should have said the observed universe. Maybe a distinction without a difference?

 

[ynot1]

would it be that there is no center or that every point is the center? Or is there a difference between those two?

I can define the center of a circle - every point on the circle is equidistant from the center - pick the closest one. I presume such can be said of a sphere except you only have one choice. But there is no point equidistant from every point on the surface of the earth, as well as the universe, ergo the Earth and the universe technically have no center according to my understanding of the definition of center. This assumes the universe has a surface, but that is debatable.

 

[Drakkith]

Certainly. I should have said the observed universe. Maybe a distinction without a difference?

Certainly as we get more telescopes and they get bigger and better we will be able to see dimmer objects or get better resolution, but I wouldn't say the observed universe becomes "bigger". But I'm not one of those philosophers you were talking about either.

 

[ynot1]

Certainly as we get more telescopes and they get bigger and better we will be able to see dimmer objects or get better resolution, but I wouldn't say the observed universe becomes "bigger". But I'm not one of those philosophers you were talking about either.

I meant the telescopes get bigger, not the universe.

 

[phinds]

Yes the observable universe becomes bigger. Point being you can observe more with better telescopes. Why would the universe get bigger, except for expansion?

So, you figure that when folks learned how to sail around the world, and could therefore see more of it, it got bigger?

I think you misunderstand the term "observable universe". It is NOT based on what we CAN see, it is based on what we COULD see, and it is at present 13.72billion light years in radius and if we had the most amazingly wonderful telescopes that could possibly be built, and that could see throughout the electormagnitic spectrum, it would STILL be 13.72 light years in radius.

 

[Fredrik]

So, you figure that when folks learned how to sail around the world, and could therefore see more of it, it got bigger?

I think you misunderstand the term "observable universe". It is NOT based on what we CAN see, it is based on what we COULD see, and it is at present 13.72billion light years in radius and if we had the most amazingly wonderful telescopes that could possibly be built, and that could see throughout the electormagnitic spectrum, it would STILL be 13.72 light years in radius.

That's the number of years that the oldest light has been traveling towards us, but due to the expansion of the universe, the actual radius in significantly larger. I don't remember exactly, but I think it's about 45 billion light-years.

 

[phinds]

That's the number of years that the oldest light has been traveling towards us, but due to the expansion of the universe, the actual radius in significantly larger. I don't remember exactly, but I think it's about 45 billion light-years.

Yes, I agree, and I knew that but got sidetracked by the silliness of the concept of the OU getting bigger because of telescopes so I fixated on the photon age, not the current diameter (which of course IS getting bigger, but not because we have better telescopes)

 

[ynot1]

That's the number of years that the oldest light has been traveling towards us, but due to the expansion of the universe, the actual radius in significantly larger. I don't remember exactly, but I think it's about 45 billion light-years.

So our telescopes only show us the universe in its past. Wouldn't it be nice if we could see the present? In fact we're building them right now - the gravitational interferometers. But you say even gravitational waves take time to propagate, so we really couldn't see the present even if we wanted to. Yes unfortunately this planet is being accelerated so we can't see anything in the present. However we sure could see a lot more considering all matter created during inflation is now in gravitational communication since the universe was very small at that time. The trick is when objects accelerate the changes in their gravitational fields propagate only at the speed of light. However note static gravitational fields are in instantaneous gravitational communication.

 

[Cosmo Novice]

So our telescopes only show us the universe in its past. Wouldn't it be nice if we could see the present? In fact we're building them right now - the gravitational interferometers. But you say even gravitational waves take time to propagate, so we really couldn't see the present even if we wanted to. Yes unfortunately this planet is being accelerated so we can't see anything in the present. However we sure could see a lot more considering all matter created during inflation is now in gravitational communication since the universe was very small at that time. The trick is when objects accelerate the changes in their gravitational fields propagate only at the speed of light. However note static gravitational fields are in instantaneous gravitational communication.

Yes it would be nice if we could see the present but unfortunately we cant, the Universe speed limit forbids it. There is no such thing as instant gravitational communication on a static field, this is more to do with observation than instantaneous propogation, in fact gravity propogates at the speed of light.

Please see a relevant wiki extract:

The consequence of this, is that static fields (either electric or gravitational) always point directly to the actual position of the bodies that they are connected to, without any delay that is due to any "signal" traveling (or propagating) from the charge, over a distance to an observer. This remains true if the charged bodies and their observers are made to "move" (or not), by simply changing reference frames. This fact sometimes causes confusion about the "speed" of such static fields, which sometimes appear to change infinitely quickly when the changes in the field are mere artifacts of the motion of the observer, or of observation.

In such cases, nothing actually changes infinitely quickly, save the point of view of an observer of the field. For example, when an observer begins to move with respect to a static field that already extends over light years, it appears as though "immediately" the entire field, along with its source, has begun moving at the speed of the observer. This, of course, includes the extended parts of the field. However, this "change" in the apparent behavior of the field source, along with its distant field, does not represent any sort of propagation that is faster than light.

 

[ynot1]

Yes it would be nice if we could see the present but unfortunately we cant, the Universe speed limit forbids it. There is no such thing as instant gravitational communication on a static field, this is more to do with observation than instantaneous propogation, in fact gravity propogates at the speed of light.

Please see a relevant wiki extract:

The consequence of this, is that static fields (either electric or gravitational) always point directly to the actual position of the bodies that they are connected to, without any delay that is due to any "signal" traveling (or propagating) from the charge, over a distance to an observer. This remains true if the charged bodies and their observers are made to "move" (or not), by simply changing reference frames. This fact sometimes causes confusion about the "speed" of such static fields, which sometimes appear to change infinitely quickly when the changes in the field are mere artifacts of the motion of the observer, or of observation.

In such cases, nothing actually changes infinitely quickly, save the point of view of an observer of the field. For example, when an observer begins to move with respect to a static field that already extends over light years, it appears as though "immediately" the entire field, along with its source, has begun moving at the speed of the observer. This, of course, includes the extended parts of the field. However, this "change" in the apparent behavior of the field source, along with its distant field, does not represent any sort of propagation that is faster than light.

Good quote. Note static gravitational fields do not propagate.

 

[Drakkith]

Good quote. Note static gravitational fields do not propagate.

True, but a static field permits no communication either.

 

[ynot1]

True, but a static field permits no communication either.

A logical necessity since if you tried to send some type of gravitational signal you would no longer be a static field. However moving static fields allow the precise determination of their position, mass, velocity, and direction of travel, assuming you can track the magnitude of the field at different positions and times. That way you can get out of the way of that big boy before it comes crashing in. It wouldn't do much good to try and communicate with an asteroid anyway. Note the shape of the object from your perspective, even if it passes, could theoretically be calculated. If the object had spin you could even get a 3d profile. I am wondering if the resolution of the measurements would be limited by the zero point energy on the interferometer reflecting surfaces. I believe there is however a logical question if non-symmetrical rotating objects generate a static field.

 

[Drakkith]

I'm not sure a massive object coming towards you is an example of a static gravitational field.

 

[ynot1]

I'm not sure a massive object coming towards you is an example of a static gravitational field.

If it's not accelerating or rotating I think it would have to be. Else you would have to pick a preferred initial frame of reference (namely yours).

 

[bmehmud]

Some questions do not have logical answers. We should consider the universe is created as it is and expanding rather considering it originated from a center point. Every point in the universe if a creation point and further looking for logical answers would confuse the physical theories itself.

 

[ynot1]

Some questions do not have logical answers. We should consider the universe is created as it is and expanding rather considering it originated from a center point. Every point in the universe if a creation point and further looking for logical answers would confuse the physical theories itself.

Don't forget - those who have all the answers also have all the questions. So further looking wouldn't be helpful.

 

[phinds]

Some questions do not have logical answers. We should consider the universe is created as it is and expanding rather considering it originated from a center point. Every point in the universe if a creation point and further looking for logical answers would confuse the physical theories itself.

Uh ... HUH ?

Is there any physics in whatever it is you just said?