How big is the universe?

[webolife]

I am one of the more vocal proponents of the finite universe around these here parts.
I first began to ponder this when I learned as a middle schooler [60's] that Einstein had computed the number of atoms in the universe to be in the order of 10^80... at first hearing, I was surprised and somewhat annoyed. Redshift reconsiderations that I began to ponder as far back as '81 [when I met RA Smith] made me more comfortable with the idea that the universe may just not be "so big", which has been significantly reinforced with my being introduced 5 or so years ago to Halton Arp and the EU. Considerations of the fractality and holographic nature of the universe can lead in either direction, it seems to me. On the one hand, "scalability" suggests there is no need for a largest scale, but that also leads to no smallest scale. Neither of these seems to fit the observations of physics.
The steady state view of Fred Hoyle which has been largely adopted by EU folks here no more confirms an infinite amount or extent of material in the universe, than the BB theory proves a beginning! Neither view, nor any view, can conclusively answer either the questions, "What if the universe has a boundary?", or "What if there is an infinite amount of matter?" As a mathematics teacher I try to help kids see both the continuity and density of numbers as being "infinite", but this is an abstraction that need not [and cannot be proven to] apply to the actual universe. In some important ways, "infinite mass" is an oxymoron... regardless of the many ramblings on the "What is Mass?" thread, it is virtually impossible to define "mass" without visualizion of a boundary. It is ultimately a philosophical question, and not the least bit analogous to a "flat earth", IMHO.

[junglelord]

How big is the universe?>
So big no one knows for sure.

[Harry Costas]

G'day

Years gone, people thought that the universe was just our Milky Way. Now with deep field images we can see over 13 billion Gyrs with a rough count of over 300 billion galaxies. Thats observable.

Try putting a boundary on that.

[webolife]

You just did.

[Harry Costas]

G'day


No I did not. You read my words out of context.

My words imply that with better tools we will see further and further and thus the boundary observable is restricted by our tools.

The universe is infinite:

The question is:

Is it the same as the observable?

[webolife]

The extent and supposed age of the universe are built on faulty [IMO] assumptions regarding redshift and Hubble's [not-so-]constant. I'm quite cognisant of observational limitations and the implications thereof. There is simply no evidenciary reason to believe the physical universe is infinite... it is strictly a philosophical stand. Now if you consider the realms [or fields?] "beyond" the physical universe, I would be the first to agree that those realms are infinite. I actually visualize the physical universe as an atom. It's a philosophical thing.

[jjohnson]

It is a philosophical thing, or possibly a metaphysical thing, because we are not dealing with sufficient evidence to prove or disprove either idea. Just because we can't see past what is observable (by definition, just as we can't "see" dark matter) does not mean that there is nothing more to see and that's all there is. It also does not mean that it goes on infinitely farther, either. Why doesn't it? Because there is no evidence to support either hypothesis. Logic, faith, philosophy and metaphysics do not constitute evidence, just thought processes.

I personally prefer to say that the universe is singular, and of indefinite extent and age. It is larger and older than I can come close to comprehending, and I feel as if I am not putting my time to good use arguing about whether it is infinite and bounded, or closed and finite. I do think it is conservative and nothing leaves it or can come into it because it, by definition, has and keeps it all. I believe all this, I suppose, because I am very comfortable with the stability of an environment that is long-lasting, big enough to play in for all time, and reasonably predictable yet surprisingly unpredictable for variety and interest.

Remember the roots of the word universe - all turned or combined into one. i.e. not many. Of course, words and roots of words don't necessarily make them real or the actuality of what they purport to define.

Jim

[webolife]

I appreciate the subtle distinction between indefinite and infinite. One pictures our human limitations, the other pictures inherent limitlessness. I also appreciate the vastness of the universe and all it contains, and look forward to the millenia of searching to comprehend what is found in it. I argue the point when challenged by one who says not to believe is analogous to being a flat-earther... but I also challenge the idea that physical matter and energy are "eternal". I have great respect for those who differ from me on this point, eg. most of the EU gurus and the contributors to this forum, but we can't all agree on everything...that would be no fun

[Harry Costas]

G'day

The following link is of interest and in no way do I think it is right or wrong in other words my opinion should not influence yours.

Extending the WMAP bound on the size of the Universe
Apr-07
http://adsabs.harvard.edu/abs/2007PhRvD..75h4034K
http://adsabs.harvard.edu/cgi-bin/nph-d ... db_key=AST

The topology of the Universe can leave an imprint on the cosmic microwave background (CMB) radiation. Clues to the shape of our Universe can be found by searching the CMB for matching circles of temperature patterns. A full sky search of the CMB, mapped extremely accurately by NASA’s WMAP satellite, returned no detection of such matching circles and placed a lower bound on the size of the Universe at 24 Gpc. This lower bound can be extended by optimally filtering the WMAP power spectrum. More stringent bounds can be placed on specific candidate topologies by using a combination statistic. We use optimal filtering and the combination statistic to rule out the suggestion that we live in a Poincaré dodecahedral space.

[Harry Costas]

G'day

Maybe some of the terms need explaining.

Homology sphere
http://en.wikipedia.org/wiki/Homology_sphere

Poincaré homology sphere
The Poincaré homology sphere (also known as Poincaré dodecahedral space) is a particular example of a homology sphere. Being a spherical 3-manifold, it is the only homology 3-sphere (besides the 3-sphere itself) with a finite fundamental group. Its fundamental group is known as the binary icosahedral group and has order 120. This shows the Poincaré conjecture cannot be stated in homology terms alone.

[edit] Construction
A simple construction of this space begins with a dodecahedron. Each face of the dodecahedron is identified with its opposite face, using the minimal clockwise twist to line up the faces. Gluing each pair of opposite faces together using this identification yields a closed 3-manifold. (See Seifert-Weber space for a similar construction, using more "twist", that results in a hyperbolic 3-manifold.)

Alternatively, the Poincaré homology sphere can be constructed as the quotient space SO(3)/I where I is the icosahedral group (i.e. the rotational symmetry group of the regular icosahedron and dodecahedron, isomorphic to the alternating group A5). Less technically, this means that the Poincaré homology sphere is the space of all possible orientations of an icosahedron. One can also pass instead to the universal cover of SO(3) which can be realized as the group of unit quaternions and is homeomorphic to the 3-sphere. In this case, the Poincaré homology sphere is isomorphic to S3/Ĩ where Ĩ is the binary icosahedral group, the perfect double cover of I embedded in S3.

Another approach is by Dehn surgery. The Poincaré homology sphere results from +1 surgery on the right-handed trefoil knot.

[edit] Cosmology
In 2003, lack of structure on the largest scales (above 60 degrees) in the cosmic microwave background as observed for one year by the WMAP spacecraft led to the suggestion, by Jean-Pierre Luminet of the Observatoire de Paris and colleagues, that the shape of the Universe is a Poincaré sphere.[1][2] In 2008, astronomers found the best orientation on the sky for the model and confirmed some of the predictions of the model, using three years of observations by the WMAP spacecraft.[3] There is as yet no strong support for the correctness of the model, however.

[webolife]

This reminds me of the remarkable COBE picture of the cosmic dipole.
I first saw it on APOD here:
http://antwrp.gsfc.nasa.gov/apod/ap030209.html
If the universe is infinite, how could we possibly be moving toward one side of it?

[webolife]

I am reminded also of a picture I first saw here:
http://www.welcomethelight.com/wp-conte ... luster.jpgof the double octahedron structure of the local supercluster of galaxies.

[Harry Costas]

G'day

Most of the APOD images are in fantasy land

[jjohnson]

Harry: I like to look at the (usually very nicely done) APOD images and think about the EU explanation, if one is indicated, and then read the fantasy land descriptions below it. The ideas about the images is where we and the conventional astronomers differ, usually sharply. The fable about the blind men and the elephant is revealing. To draw the analogy, I think the EU crowd are the story-teller, and the blind men are Those Whose Names Shall Not Be Spoken...

[Harry Costas]

G'day JJ

We are at the steps of research and it is a mistake to ear mark any model to be correct.

There is one model that has to go and that is the BBT, it has slowed down research and directed it into la la land.

As for the EU it has potential.

NASA assuming that the BBT is correct has placed itself in a funny position, having thousands of comments that hang on the BBT and they are worried big time since alot of their cash flow was on the BBT and many scientists that did not think along the BBT were given the boot.