Can We Determine the Center of the Universe Using Comet Orbits?

In summary, the conversation discusses the concept of a center to the universe and whether it is meaningful to talk about such a center. The idea that the universe began as a single point and expanded from there is debated, with some pointing out the logical inconsistencies in this theory. The analogy of a balloon is used to explain the curvature of the universe and the fact that there is no center point. Ultimately, the approximate center of the observable universe is wherever the observer is, due to the homogeneity of the universe.
  • #1
shivakumar06
69
0
can we find the center of the universe by measuring the deviation from theoretical value of the shape of comet's orbit when compared to real shape of comet's orbit.
 
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  • #2
There is no center to the universe.

The OBSERVABLE universe has a center, and you are it.

EDIT: you would likely find it informative to read the FAQ in the cosmology section
 
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  • #3
phinds said:
There is no center to the universe.

The OBSERVABLE universe has a center, and you are it.

EDIT: you would likely find it informative to read the FAQ in the cosmology section

Are we moving relative to the observable universe?
 
  • #4
Hetware said:
Are we moving relative to the observable universe?

Wherever you are, you are the center of the observable universe, so no, we are not by definition.

EDIT: you would likely find it informative to read the FAQ in the cosmology section
 
  • #5
we know that universe was created after big bang occured. then the universe would have been a point and started expanding in all direction then it have looked like a spherical ball whose surface is expanding a center. so it is meaningful to talk of center of universe isn't it
 
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  • #6
shivakumar06 said:
we know that big bang occured. then the universe would have been a point object. so then the universe would have had a center.
Where's the center of a point?
 
  • #7
Jimmy said:
Where's the center of a point?

sorry. i have edited my posting now.
 
  • #8
shivakumar06 said:
we know that universe was created after big bang occured. then the universe would have been a point and started expanding in all direction then it have looked like a spherical ball whose surface is expanding a center. so it is meaningful to talk of center of universe isn't it

Absolutely not. The big bang was most emphatically NOT a point. It happened everwhere and there is no center and no edge.

This is a bit hard to get your head around when you first hear it, but it is the case. You should read more cosmology. Try the FAQ in the cosmology section.
 
  • #9
The premise the universe began as an infinitesimal point is illogical on two counts:
1] If the universe is infinite, it was infinite from the beginning. Only the observable universe would be point-like at its inception.
2] Unless the big bang occurred in some kind preexisting space, the size of a point is undefined in the absence of external spatial coordinates.
 
  • #10
Chronos said:
The premise the universe began as an infinitesimal point is illogical on two counts:
1] If the universe is infinite, it was infinite from the beginning. Only the observable universe would be point-like at its inception.2] Unless the big bang occurred in some kind preexisting space, the size of a point is undefined in the absence of external spatial coordinates.

I agree w/ what you are saying, except that I see the bolded statements as mutually contradictory. If the current observable universe started off as a dimensionless point, then it seems to me that so would have the entire universe. The observable universe likely started off REALLY small, but not as a point. Perhaps that's what you intended by "point-like" ?
 
  • #11
Maybe it would help to think of the universe as a big balloon. Right now we think the balloon is about ~50 billion LY 'across'. Now, going back in time, the universe gets progressively smaller and so does the balloon. The thing is, we have to think of ourselves as being on the surface of the balloon so we don't really have a center, do we? But as the universe goes back further in time, at some point in time it was say, 1 cm across. It is still that same balloon and on the surface that same point looks the same as it does if it is 50 billion light years across, the angles all go out at exactly the same angle from a point on the surface, so it doesn't matter if the universe were one micron across or 50 billion LY across, we are still on the surface so there is no center we can find.

The idea of the balloon shows us the universe has a curvature so if we had a spacecraft that could do say a trillion times the speed of light and travel in what we think is a straight line, we would come back to the same place after X amount of time, whatever that is, say at one trillion c, assuming the universe is actually 50 E9 ly across, we would come back to our solar system in about 20 minutes even though we thought we would be traveling in a straight line. Our straight line is really a very slow curve not even noticeable if we only went from here to the closest star, Alpha Centauri or thereabouts.
 
  • #12
phinds said:
Wherever you are, you are the center of the observable universe, so no, we are not by definition.

EDIT: you would likely find it informative to read the FAQ in the cosmology section

I had this conversation with John Archibald Wheeler. How would you determine the center of mass of the observable universe, at least approximately?
 
  • #13
phinds said:
I agree w/ what you are saying, except that I see the bolded statements as mutually contradictory. If the current observable universe started off as a dimensionless point, then it seems to me that so would have the entire universe. The observable universe likely started off REALLY small, but not as a point. Perhaps that's what you intended by "point-like" ?
That is essentially the issue addressed by my second assertion. An infinite ensemble of infinitesimal points would collectively, and individually, be spatially undefined.
 
  • #14
Chronos said:
That is essentially the issue addressed by my second assertion. An infinite ensemble of infinitesimal points would collectively, and individually, be spatially undefined.

Ah ... an interesting way to look at it. I had not considered it that way before. Thanks for the clarification.
 
  • #15
Hetware said:
I had this conversation with John Archibald Wheeler. How would you determine the center of mass of the observable universe, at least approximately?

The approximate center of mass of the observable universe is wherever you are. Given homogeneity, I'd say the approximation is quite accurate.
 
  • #16
shivakumar06 said:
we know that universe was created after big bang occurred. then the universe would have been a point and started expanding in all direction then it have looked like a spherical ball whose surface is expanding a center. so it is meaningful to talk of center of universe isn't it

Not really. You are imagining the universe as an expanding ball, which is probably in error. The Poincare Conjecture yields possible hints about the topology of our universe. You would be better off imagining our universe mapped to the surface of a ball, like the surface of the earth. Some people used to think Vatican City, Rome, was the center of the world. Others thought it was in Ireland. Bad points could be made for either. If the Earth were a perfect sphere, no matter where you were the horizon would appear equidistant in all directions, giving you the illusion you were at the center. But if you were to travel far enough in a straight line, you would return to your starting point.

The topology of our universe is probably much like that. Also, as the sphere expands, objects appear to recede from you--just as they do in our universe at large. No point on the surface of this sphere may rightly be considered the center. But we COULD possibly use the word "center" to describe a point in time, roughly 13.7 billion years ago...
 
  • #17
This is a good explanation supplemented with a visual example: (Skip to 8:20)https://www.youtube.com/watch?v=3pAnRKD4raY
 
  • #18
FreeMitya said:
This is a good explanation supplemented with a visual example: (Skip to 8:20)


https://www.youtube.com/watch?v=3pAnRKD4raY

Nicely done video but I am at a complete loss to see how it has ANY bearing on this thread. What am I missing?
 
  • #19
phinds said:
Nicely done video but I am at a complete loss to see how it has ANY bearing on this thread. What am I missing?

Admittedly, I was responding less to the original post and more to the first post (your post) about how wherever one is in space, one is always at the centre of the universe, and I thought a visual example of the Cosmological principle would be helpful to laymen like myself. Did you skip to 8:20?
 
  • #20
FreeMitya said:
Admittedly, I was responding less to the original post and more to the first post (your post) about how wherever one is in space, one is always at the centre of the universe, and I thought a visual example of the Cosmological principle would be helpful to laymen like myself. Did you skip to 8:20?

I watched the whole thing, thought the emphasis on black holes made it irrelevant to this thread even though there was some discussion about the center.
 
  • #21
phinds said:
I watched the whole thing, thought the emphasis on black holes made it irrelevant to this thread even though there was some discussion about the center.

No worries, it's completely understandable.
 
  • #22
There is a set of non-intersecting world lines, each one at rest relative to the the observable universe. In an expanding universe these world lines move farther apart. Relative rest with respect to the observable universe can be determined by measuring the Doppler shift of the most distant radiation sources.

If an observer is moving relative to the center of mass of the observable universe he will observe a blue shift in the direction toward which he is moving, and a red shift in the opposite direction.

I originally stated this with respect to the cosmic background radiation. That statement is probably still valid, but there's a little catch, that I'm not certain of.
 
  • #23
phinds said:
The approximate center of mass of the observable universe is wherever you are. Given homogeneity, I'd say the approximation is quite accurate.

Isn't the center of mass the sum of the moments divided by the sum of the masses? Surely that location is not following me around. If I step on the gas, the center of mass of the observable universe is not accelerating with me.
 
  • #24
Thermate said:
Isn't the center of mass the sum of the moments divided by the sum of the masses? Surely that location is not following me around. If I step on the gas, the center of mass of the observable universe is not accelerating with me.

Do you really think your mass, or the distance you can travel, makes anything other than an infinitesimal difference, compared to the mass of the observable universe and the distance from you to its edge? I stand by my statement.
 
  • #25
phinds said:
Do you really think your mass, or the distance you can travel, makes anything other than an infinitesimal difference, compared to the mass of the observable universe and the distance from you to its edge? I stand by my statement.

So are you, or are you not moving relative the the center of mass of the observable universe?
 
  • #26
Thermate said:
So are you, or are you not moving relative the the center of mass of the observable universe?

Of course you are moving with respect to the center of mass of the OBSERVABLE universe. Just keep in mind that your observable universe changes as you move.
 
  • #27
Thermate said:
So are you, or are you not moving relative the the center of mass of the observable universe?

As Drakkith said, yes you are, but I would add that

1) Your observable universe is being constantly redefined due to motion
2) this is far more due to the movement of the earth/sun/galaxy than to anything you personally can do here on Earth
3) the distance to the edge of your observable universe is about 47 billion light years and all of the motion in #1 is trivial by comparison.
4) Even a much faster motion would not change the fact that the center of mass of your observable universe, due to homogeniety, pretty much follows along with you (the light-cone center is always exactly where you are, by definition)
 
  • #28
phinds said:
3) the distance to the edge of your observable universe is about 47 billion light years and all of the motion in #1 is trivial by comparison.

Please provide the sound and valid reasoning that concludes that my observable universe is about 47 billion light years. Does that mean I can see back before the big bang?
 
  • #29
Thermate said:
Please provide the sound and valid reasoning that concludes that my observable universe is about 47 billion light years. Does that mean I can see back before the big bang?

That is the radius of the observable universe. The universe has expanded over the last 13.7 billion years and is now the observable universe is much bigger than the 13.7 billion light years one might expect.
 
  • #30
Drakkith said:
That is the radius of the observable universe. The universe has expanded over the last 13.7 billion years and is now the observable universe is much bigger than the 13.7 billion light years one might expect.

This may be some kind of gravitational lensing effect. I will grant that the entire concept of time becomes a bit nebulous in this context; nonetheless, one would expect that the observable universe is no larger than the distance light could travel in the age of the universe.

I am aware that there are three 3-planes of simultaneity with respect to the local universal rest frame. Perhaps one of them will account for your ~47 billion year observable scale. I would like to see your sources on this.
 
  • #31
Thermate said:
This may be some kind of gravitational lensing effect.

HUH? I'd say you don't understand gravitational lensing. Certainly it has nothing to do with this discussion.

I will grant that the entire concept of time becomes a bit nebulous in this context; nonetheless, one would expect that the observable universe is no larger than the distance light could travel in the age of the universe.
If the universe were totally static, you would be rigth, but it isn't, so you are wrong. It's expanding.

I am aware that there are three 3-planes of simultaneity with respect to the local universal rest frame. Perhaps one of them will account for your ~47 billion year observable scale. I would like to see your sources on this.
I have no idea what you mean by this. As for a reference of the 47 billion years, get any Cosmology 101 text.
 
  • #32
phinds said:
HUH? I'd say you don't understand gravitational lensing. Certainly it has nothing to do with this discussion.


If the universe were totally static, you would be rigth, but it isn't, so you are wrong. It's expanding.


I have no idea what you mean by this. As for a reference of the 47 billion years, get any Cosmology 101 text.


Please provide a specific reference. ISBN and page number.
 
  • #33
OK. I see cosmology has finally caught up with what I was saying decades ago. You are talking about the Universe as treated as simultaneous with the local center of mass of the observable universe. Congratulations to the scientific community! You finally caught up with a high school dropout. As I said, this is a "lensing" effect. One plane of simultaneity is the time that all observers will agree upon when they look at their watches and measure their own time lines relative to the big bang.
 
  • #34
phinds said:
HUH? I'd say you don't understand gravitational lensing. Certainly it has nothing to do with this discussion.

Really? Has the global curvature of the universe changed in the past 13 billion years?

If the universe were totally static, you would be rigth, but it isn't, so you are wrong. It's expanding.


I have no idea what you mean by this. As for a reference of the 47 billion years, get any Cosmology 101 text.

Another second plane of simultaneity is what actually hit's our eyes. The further back in space you look. the further back in time you see.


Those are the easy ones. Sorry. I can't give you a reference on this, because I only have it as an immediate thought. I don't know that it is written down anywhere.
 
  • #35
Thermate said:
Please provide a specific reference. ISBN and page number.

Offhand you could google "Lineweaver expanding confusion"
or google "Lineweaver inflation cosmic microwave background".

You will get some links that say "arxiv". this is a free archive of scientific articles. Lineweaver is a top cosmologist and a good writer. He explains things clearly. I think
Figure 1 in either of those papers would show the particle horizon to be around 46 billion LY.
this is how far away TODAY the most distant matter is that we could in principle be getting a signal from.
this is normally what people mean by the radius of the observable region.

Of course that matter was much closer when it emitted the light, and the light has had to contend with expansion so it has taken some 13 billion years to get to us. But the matter which emitted the light is NOW about 46 billion LY away, because of expansion.

So that is the present distance of the most distant stuff we can see, and it is the radius of the observable. the figures here are estimates. Something around 46, maybe 47, as was said earlier. Can't be too exact.

I have figure 1 from one of Lineweaver's articles in my signature. You could check the figure without even having to go fetch the article from arxiv. If you want.

You can see where the lightcone touches down, around 46 Gly (billion ly). You can see in the figure how it touches down a little over halfway between the 40 Gly mark and the tick for 50 Gly. So it is roughly 46. Also this is where the particle horizon line crosses the level marking present time.

Googling you get the arxiv copies of both articles and both have the same figure 1 in them. It is basic.
 
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<h2>1. What is the center of the universe?</h2><p>The center of the universe is a theoretical point that is believed to be the origin of the Big Bang, the event that created the universe. However, since the universe is constantly expanding, there is no specific point that can be identified as the exact center.</p><h2>2. Can we determine the center of the universe?</h2><p>Currently, we do not have the technology or knowledge to accurately determine the center of the universe. The concept of a center point is also debated among scientists and there is no consensus on its existence.</p><h2>3. How do comet orbits help in determining the center of the universe?</h2><p>Comet orbits can provide valuable information about the structure and movement of the universe. By studying the trajectories of comets, scientists can gain insights into the gravitational forces and distribution of matter in the universe, which can help in understanding the overall structure and potentially the center of the universe.</p><h2>4. Are there any other methods for determining the center of the universe?</h2><p>There are various theories and methods proposed by scientists, such as studying the cosmic microwave background radiation or using the redshift of galaxies. However, none of these methods have been proven to accurately determine the center of the universe.</p><h2>5. Why is it important to determine the center of the universe?</h2><p>Determining the center of the universe can help us better understand the origins and evolution of the universe. It can also provide insights into the fundamental laws of physics and potentially lead to new discoveries and advancements in our understanding of the universe.</p>

1. What is the center of the universe?

The center of the universe is a theoretical point that is believed to be the origin of the Big Bang, the event that created the universe. However, since the universe is constantly expanding, there is no specific point that can be identified as the exact center.

2. Can we determine the center of the universe?

Currently, we do not have the technology or knowledge to accurately determine the center of the universe. The concept of a center point is also debated among scientists and there is no consensus on its existence.

3. How do comet orbits help in determining the center of the universe?

Comet orbits can provide valuable information about the structure and movement of the universe. By studying the trajectories of comets, scientists can gain insights into the gravitational forces and distribution of matter in the universe, which can help in understanding the overall structure and potentially the center of the universe.

4. Are there any other methods for determining the center of the universe?

There are various theories and methods proposed by scientists, such as studying the cosmic microwave background radiation or using the redshift of galaxies. However, none of these methods have been proven to accurately determine the center of the universe.

5. Why is it important to determine the center of the universe?

Determining the center of the universe can help us better understand the origins and evolution of the universe. It can also provide insights into the fundamental laws of physics and potentially lead to new discoveries and advancements in our understanding of the universe.

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