Are we located at the core of the Universe?

[Mordred]

Try reading the articles I wrote first. Pay attention to the detail on light paths

The curvature is part of the FLRW metric. Each scenario is part of the equations. However the Universe is so dang big it is tricky to isolate a precise curvature constant. It's taken over 50 years of data to fine tune the value we have today.

 

You keep expecting exact answers that's rarely the case on cosmological scales.

The universe is so big it's highly possible we may never know if it's finite or infinite. Not with 100% certainty

 

 

Think of a flea sitting on a beachball from its view point the ball is flat.

 

Could very well be the same case for the curvature. We could be in such a small portion that all measurements give the appearance of flat

Edited March 10, 2016 by Mordred

[Strange]

However - 92 billion Ly diameter sphere is a limited number.

So, what the observer might see at the end of those 92 billion Ly?

 

According to our current best theories, we expect they would see pretty much the same as we see. A universe of 92 bilion yerars diameter with everythign moving away from everything else.

 

Hence, do you agree about the following?[/size]

"The Universe has only three dimensions, it is finite but it has no edge"

 

I agree it is one possibility.

 

Do you agree that if we go at one direction all the way, then at some point we will get to an end?

 

Not necessarily. Consider the analogy of the surface of a sphere. It has a finite area but no edge. If you travel in s straight line you will get back to where you started (I don't think that is true for all topologies).

I assume that this is a pure theory.

Is it correct?

If so, please try to distinguish between theory and evidence.

Please stop trying to dismiss things you don't like (and don't understand) as "just theory". The only reason we have theory is because of the evidence. As your personal opinions are not based on evidence, you are in no position to make these demands of others.

[David Levy]

Not necessarily. Consider the analogy of the surface of a sphere. It has a finite area but no edge. If you travel in s straight line you will get back to where you started (I don't think that is true for all topologies).

 

As I have already stated, it is perfectly O.K. to use the analogy of the surface of a sphere.

Therefore, yes - we can assume that the universe acts as as surface of a sphere.

However, if it is a surface of a sphere then everything should react on the same basis.

Hence, If the light goes as in a surface of a sphere, then also the expansion should work under the same conditions.

So, how could it be that we assume that the light goes in some sort of loop, while the expansion goes straight on?

Isn't it the same universe?

Thanks Mordred.

 

I will read the article.

 

 

Think of a flea sitting on a beachball from its view point the ball is flat.

Could very well be the same case for the curvature. We could be in such a small portion that all measurements give the appearance of flat

 

Yes, fully agree.

 

We can choose any point of view.

 

However, it must work for all. - Light and Expansion.

 

Hence, if there is a curvature in light, then there must be a curvature in the expansion.

 

Therefore, if this is correct, than we need to adjust all our calculations about the expansion.

 

Do you agree?

 

Edited March 10, 2016 by David Levy

[Mordred]

If you study the article you will note how thermodynamics, mainly energy/density works with geometry. I think the difficulty you might be having is thinking the curvature is on a particular orientation.

 

It isn't you will have the same curvature regardless of direction.

 

Remember the cosmological principle.

There is no preferred direction or location. Homogeneous and isotropic.

 

So yes the Universe geometry is also involved in expansion, The light rays path is a consequence of the geometry.

 

We don't need to adjust our thinking on this aspect as the energy/density relations used in expansion already determine the null geodesic aspects via the Einstein field equations for the path of light.

 

(As I know you aren't strong on the EFE equations you'll have to accept my word on that). Trying to explain the principle of least action and spacetime hydrodynamic relations with the FLRW metric is an extremely lengthy and math intense subject.

 

Far more than can be done in a forum

Edited March 10, 2016 by Mordred

[Strange]

Yes, I fully understand.

But we can't say again - "sorry we don't know, however, based on what we don't know, it is clear that what you say is incorrect".

Yes we can. We might not know what the right answer is, but that doesn't stop us eliminating a lot of wrong answers.

[Mordred]

Lets put it this way. One of the methods we used to determine our geometry was to look for distortions in the CMB measurements. As the thermodynamic properties determine our overall geometry and affects light paths. Those distortions become apparent when you have curvature. As we see an extremely small distortion we can tell our universe is flat. (The CMB is all around us so you can't look in one direction to see the entire CMB you must measure every direction and orientation)

Yes we can. We might not know what the right answer is, but that doesn't stop us eliminating a lot of wrong answers.

That's a highly accurate way of describing the problem.

 

Prior to WMAP you would be amazed at the number of geometry shapes were theorized to describe the Universe.

 

Donut, torus, saddle, klien Gordon bottle etc.

 

The WMAP and Planck data eliminated hundreds of models that were running around. I recall being on Space.com back when it had a forum in the 80s arguing alternative geometry models.

 

Lol Minkowsii metric was the big thing back then. Now it's not so practical except as introductory to GR. Lol the quintessence and MOND arguments were extreme

(Ps yes I'm old but not that old I started studying cosmology when I was in my teens. Right after Allen Guth proposed inflation)

 

Just a side note if the Planck datasets continue in the direction it's going the number of viable inflation models will reduce to 7 out of 76.

 

The preference to observation being single scalar to low kinetic term models

@David the above should indicate that science is a process of elimination.

Most ideas presented on speculation have been presented before (if feasible) and already eliminated.

 

Granted most speculative ideas on a forum aren't even feasible.

Edited March 10, 2016 by Mordred

[sunshaker]

With more and more scientists believing in multiverses, I do not see why their is still so much negativity/venom against "our universe" having an outer edge.

 

 

These so-called 'bubble universes', which are expanding within the multiverse, bumped into each other as they expanded after the Big Bang, leaving an imprint on each other's outer surface.

Read more: http://www.dailymail.co.uk/sciencetech/article-3295063/Have-scientists-spotted-parallel-universe-Bright-spots-Big-Bang-universe-bumping-own.html#ixzz42UiuSwxQ

[Mordred]

Multiverse theories don't mean our universe is finite.

 

You can devide an infinite universe an infinite number of times and each universe would still be infinite

[sunshaker]

Multiverse theories don't mean our universe is finite.

 

You can devide an infinite universe an infinite number of times and each universe would still be infinite

I agree, I believe in multiverses, but also believe our universe is infinite, Infinite by being part of a multiverse.

But it still leaves the possibility that our local universe has an "outer edge", that expands into the multiverse.

[Strange]

With more and more scientists believing in multiverses, I do not see why their is still so much negativity/venom against "our universe" having an outer edge.

 

Because even in multiverse theories, the universe can still be finite but unbounded. (Or, as Mordred says, infinite.)

 

The negativity isn't against the universe having an edge; after all, it is possible that a future scientific theory will suggest that is the case. The negativity is about wilfully ignorant people insisting that their half-formed opinions must be correct.

But it still leaves the possibility that our local universe has an "outer edge", that expands into the multiverse.

 

Not in any model I am aware of. Perhaps you can provide a reference to support this?

[swansont]

 

 

Well I agree that an observer outside the Universe might see it differently from us.

But, a 46 billion LY radius sphere is a 92 billion Ly diameter sphere.

However - 92 billion Ly diameter sphere is a limited number.

So, what the observer might see at the end of those 92 billion Ly?

 

It's not outside the universe. That's a nonsensical statement. It's just someone at a different location.

 

Someone 92 billion LY away would see their own visible part of the universe, 92 billion LY in diameter. But they would not see any stars that we can see, since our visible part of the universe would not overlap with theirs.

[sunshaker]

 

Not in any model I am aware of. Perhaps you can provide a reference to support this?

There are many models, Bubble universes being but one.

 

 

Physicist Alexander Vilenkin of Tufts University explains eternal inflation and "bubble universes"

http://tuftsdaily.com/features/2016/02/01/tufts-institute-cosmologys-research-points-possibility-multiverse/

 

chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://arxiv.org/pdf/1512.01819v1.pdf

Edited March 10, 2016 by sunshaker

[Strange]

Neither of those appear to say that the universe has a boundary.

[Phi for All]

Please stop trying to dismiss things you don't like (and don't understand) as "just theory". The only reason we have theory is because of the evidence. As your personal opinions are not based on evidence, you are in no position to make these demands of others.

 

There seems to be a strong correlation between those who misuse the term "theory", and those who rail against mainstream science. My guess is they consider their own ideas to be "theories", and they know they are all based on guesswork with little evidence and no maths, so that's what they assume real scientists are doing, just making it up and then reverse engineering it to see if it's "true". They have little grasp of all the mountains of testing, evidence, and review a true scientific hypothesis has to go through before anyone calls it a theory.

[David Levy]

Try reading the articles I wrote first. Pay attention to the detail on light paths

The curvature is part of the FLRW metric. Each scenario is part of the equations. However the Universe is so dang big it is tricky to isolate a precise curvature constant. It's taken over 50 years of data to fine tune the value we have today.

 

Thanks for the articles.

With regards to the curvature;

http://cosmology101.wikidot.com/universe-geometry

 

It is stated:

"In a flat curvature the three angles of a equilateral triangle will add up to 180⁰. A positive curvature will add up to greater than 180⁰, a negative curvature will add up to less than 180^0"

 

Please advice if you agree with the following:

In a flat curvature - The Universe has only three dimensions.

In a positive/negative curvature - The Universe has more than three dimensions.

 

Now, on what kind of curvature our mathematics had been developed for.

In other words, could it be that Einstein' and Friedman' equations had been developed only for a flat curvature Universe?

If so, does it mean that new/updated formulas should be used for any type of curvature which is not flat (positive/negative curvature)?

Edited March 10, 2016 by David Levy

[Strange]

Please advice if you agree with the following:

In a flat curvature - The Universe has only three dimensions.

In a positive/negative curvature - The Universe has more than three dimensions.

 

No. Why do you think that?

 

In all cases the universe has four dimensions (three spatial, one time).

 

 

In other words, could it be that Einstein' and Friedman' equations had been developed only for a flat curvature Universe?

 

No, they are completely generic. They describe that universe as a pseudo-Riemannian manifold, which can have any type of curvature.

[MigL]

David has no clue what the distinction is between universe and observational/causal universe, and how one is a subset of the other.

He keeps on asking what's at the edge of the observational universe. Its simple, more universe, except its not observational to us being at the center of that sphere. But it is to other observers who may be closer to the 'edge' of our sphere.

 

That same question is important when one asks about a flat, finite universe, or expansion within a 'multiverse'.

What is at the 'edge' or boundary ? How could it have arisen ? What is it expanding into ? Etc ?

And, most importantly, why do we not see any effects of this ?

 

Almost everyone ( except David ) agrees. An infinite universe must either be flat or of negative curvature ( where a triangle is <180 deg ). While a bounded or finite universe has to have a positive curvature ( where a triangle has >180 deg ). The best reduced dimensionality analogy for a positively curved universe is a sphere where the 2d surface of the sphere represents our 3d universe ( but minus one dimension ). WE consider the surface curving because we have no way of picturing ( other than mathematically ) how a volume curves.

This curvature is also intrinsic, such that there is no inside or outside ( of the spherical analogy or actual universe ), and it also applies to other possible geometries such as toroid ( or 2,3,4... hole topologies ).

David freely admits he has limited if any understanding of certain subjects but then goes on to make assumptions and draw conclusions based on his flawed understanding of that subject matter.

It is very difficult to 'pull' him back to real physics and math since he keeps going further and further down the rabbit hole.

[David Levy]

No. Why do you think that?

In all cases the universe has four dimensions (three spatial, one time).

 

Well, please look at the picture when Ω = 1 (Flat)

Instead of universe we can think about a flat paper with only two spatial.

 

However, If Ω is different than 1, then it is like we band this paper. Therefore, instead of two spatial we actually get three spatial. (So, instead of a flat shape we get a volume – or some sort of a ball)

Even if you think about the surface of that paper, it is not the same. We have got totally different shape as we add one more spatial.

Hence, If Ω is different than 1, by definition we add one more spatial.

So, if the Universe has three spatial, this banding activity should add one more spatial.

Please advice why you disagree?

Edited March 10, 2016 by David Levy

[MigL]

Again, you have a limited understanding of the subject, and are running away with your misconceptions.

 

You can curve the paper INTRINSICALLY, without the need for above or below it.

Look up the mathematical definition.

[Strange]

So, if the Universe has three spatial, this banding activity should add one more spatial.

Please advice why you disagree?

 

Please learn to ask questions instead of making ignorant assertions: http://mathworld.wolfram.com/IntrinsicCurvature.html

http://mathpages.com/rr/s5-03/5-03.htm

[David Levy]

Again, you have a limited understanding of the subject, and are running away with your misconceptions.

 

You can curve the paper INTRINSICALLY, without the need for above or below it.

Look up the mathematical definition.

 

Sorry, that is totally incorrect.

 

Think about paper and a surface of basketball. is it the same?

 

Can you use the same mathematics formulas to both cases (even if both represent only a surface)?

[Strange]

Sorry, that is totally incorrect.

 

Please provide a mathematical proof or a reference to a credible source that confirms this.

[David Levy]

 

Please learn to ask questions instead of making ignorant assertions: http://mathworld.wolfram.com/IntrinsicCurvature.html

http://mathpages.com/rr/s5-03/5-03.htm

 

Sorry, it is stated clearly:

"The curvature of a two-dimensional curve is related to the radius of curvature of the curve's osculating circle. Consider a circle specified parametrically by…"

So, actually, as I have already stated, a two dimension had been converted to three dimensions radius of curvature.

So why you disagree?

Please also look at the mathematics. It is totally different than a simple formulas for two dimension flat paper.

How can you explain it?

Edited March 10, 2016 by David Levy

[Strange]

 

Sorry, it is stated clearly:

"The curvature of a two-dimensional curve is related to the radius of curvature of the curve's osculating circle. Consider a circle specified parametrically by…"

So, actually, as I have already stated, a two dimension had been converted to three dimensions radius of curvature.

So why you disagree?

 

Where does that say anything about 3 dimensions? (Note that all the equations for the 2D curve are in terms of x and y, not z.)

 

BTW: I assume you are referring to this page: http://mathworld.wolfram.com/GaussianCurvature.html

 

Please also look at the mathematics. It is totally different than a simple formulas for two dimension flat paper.

How can you explain it?

 

Because it is talking about curvature, not plane surfaces.

Edited March 10, 2016 by Strange

[dimreepr]

 

Sorry, it is stated clearly:

"The curvature of a two-dimensional curve is related to the radius of curvature of the curve's osculating circle. Consider a circle specified parametrically by…"

So, actually, as I have already stated, a two dimension had been converted to three dimensions radius of curvature.

So why you disagree?

Please also look at the mathematics. It is totally different than a simple formulas for two dimension flat paper.

How can you explain it?

 

 

Think of it as a mobius strip.