luc

The article is here for free

http://www.sciam.com/article.cfm?chanID=sa006&articleID=1356B82B-E7F2-99DF-30CA562C33C4F03C&pageNumber=1&catID=2

Interesting, I thought that the Milky way, along with the rest of the Local group would end up absorbed by the Virgo cluster, though the article says that due to the effect of Dark Energy, that won't happen.

. This is only possible if strings exist.

Nevr heard about that constraint, as quantum states of some particles have yet been teleported, and string are still a hypothesis.

Voyager 1 recently crossed the Termination shock, and is currently in a zone called the heliosheath. Its next goal is to cross the heliopause (it will cross it in about 10 years), and then it will go on forever gosh knows where. A true adventurer

I'd be happy if some expert could estimate the volume of a closed Universe (we all agree that a closed universe has a finite volume). I've spent the last months trying to find this information, to no avail.

The possibility of a closed and finite Universe is exciting, I wonder if we could ever find a way to map it in its totality. (I mean, create a map containing the localization of each galaxy in the whole Universe). If the expansion continues its accelerated pace this would be impossible, but if the Universe starts to contract, then maybe...

Who is Chris Vale?

aguy2

According to this page is a graduate student at California-Berkeley

http://astron.berkeley.edu/people.html

Is the man appearing in the article that bascule posted. He thinks that gravitational lensing caused by a gigantic concentration of mass (the example offered is the Shapley supercluster), can explain the coincidences in the disposition of the multipoles. It would save the face of the Lambda-CDM model, that it seems to be attacked by Magueijo, that suspects that the data may indicate a universe that has a preferred direction

I find utterly curious that the dipole should be at a right angle with the axis of evil. Then again, I'm no expert in gravitational lensing, so maybe Chris Vale is correct

i find the crystal model fascinating, but it seems that it will be inaccurate, given that recently it was found that the Perseus arm is twice as close as was previously believed. but I could be wrong, becuase I don't know when the artwork was finished

Nonetheles, the model is surely a magnificent gift for this christmas

What's the primordial atom?

It reminds me to Lemaitre's "Cosmic egg". It's the thing that you had in mind?

Do remember that in Big Bang theory, atoms were not created until 380000 years after Big Bang, during an epoch called "recombination"

What does quintessence mean?

quintessence is the other major candidate for dark energy. It's possible that the energy density of dark energy is not constant, but shows time dependence. Then the cosmological constant wouldn't be appropriate, because its energy density is constant. Quintessence is an hypothetical scalar field proposed by Steinhardt, and has an energy density that is not constant.

There's an article in wikipedia about quintessence

http://en.wikipedia.org/wiki/Quintessence_%28physics%29

From what I gather (from Wikipedia ) the main (and first) evidence for the existence of dark matter was gathered by measuring the light emitted from galaxies compared with their rotational speed. There was so little visible matter in the galaxies that with their high spin rate' date=' they should not stick together but fly apart from centrifugal force, according to standard theories of gravitation.

 

Well my theory is that the dark matter is simply black holes. We have strong evidence that massive black holes exist at the center of our Galaxy and others. They are invisible, and they are what holds the galaxies together. Any cosmologists here that can check my theory?[/quote']

 

 

No, the first evidence for DM came from the observation by Zwicky of the movement of galaxies in the Coma cluster. He observed galaxies moving so fast that ought to have escaped the cluster, so he suggested the existence of some unseen matter that was holding the cluster together

RyanJ' date=' the text from wikipedia you are quoting refers to dark matter but not to dark energy.

 

In cosmology the content of the universe is modelled as a perfect fluid with an equation of state p = w d relating pressure p and density d. Dark energy is supposed to be something that permeates space homogeneously and exerts a negative pressure acting against gravitation of matter (or energy densities). This means that w < 0. One can see that this may lead to an accelerated expansion of space when inserted in the corresponding Friedmann equation.

 

The WMAP first year data suggest that -1.3 < w < -0.7. If w < -1 then the dark energy is called phantom energy and it violates some energy conditions. If w = -1 and constant in time it is usually refered to it as the cosmological constant.

That's right. Indeed recent observations seem to reinforce the idea that Dark energy is the Cosmological constant. In that case Einstein equations should add a term involving the Cosmological constant (that term was rejected by Einstein, after having introduced it himself)

I have a question: I know the form of the Einstein equations if dark energy turns out to be the Cosmological constant, but what's the form of the equations if it turns out to be, say, quintessence?

I'm thinking about the possible messages that "God" could have written in the CMB

One obvious would be: "The answer is 42"

Other possibles:

-Sorry for the inconvenience

-Hey, how are you doing?

-I want to have a conversation with you (that would let us bewildered because we couldn't know how to answer!)

-Be good

-I'm watching you

etc.

actually, if a creator exists, can't be so mischievous to scare the hell out of us with a cosmic message. Leaving aside the fact that I don't believe in any creator

Blimey! This is the same Anton Zee that wrote my appreciated book "Quantum Field theory in a Nutshell". I think that is time to eat that book

There're a lot of good candidates, but if a cosmologist win, I will be happy. Maybe Alan Guth?

bump

I see constantly written that the gauge group of the SM is SU(3)XSU(2)XU(1), but what operation is that represented by X? Given that all the 3 terms are Lie groups, I think that is possible that is Group Direct Product?

Oh, if comets could speak... they possibly would tell this tale:

http://www.americanscientist.org/template/AssetDetail/assetid/22746/page/2

But unfortunately, they are only stupid and mute balls rushing through space

The book can be read here

http://www.gutenberg.org/catalog/world/readfile?fk_files=98461

I'm reading it, and I'm now in the part where the cylinder has just opened and everybody is waiting on pins and needles to see what thing comes out from it.

Comets have indeed 3 tails, the dust tail, the ion tail and the hydrogen tail

how can 0 expand into any finite length?

Imagine that you are in the origin of the real line. You can run either in the positive or negative direction, but you always will be over a real number, you can never achieve infinite, this is analogous to the volume of the Universe

i know very well what's inflation. i don't know though how it permits that an Universe emerging from a point can have today infinite volume. Can you explain?

inflation, what?

Actually is thought that the Universe is flat and of infinite volume. How could then have emerged from a point? A point, in the finite time since the Big Bang, 13.7 billion years, couldn't have grown to an universe of infinite volume. Pure logic, people

The Big Bang theory' date=' derived from Hubble's original hypothesis regarding red-shift, states that the Universe is expanding. Hubble's hypothesis was effected by Einstein's observations of light (c is constant) and by Doppler's experiments and statement of the "Doppler Effect". The three fundamental supporting pillars for the "Big Bang" are:

[list']

[*]redshift interpreted as the Doppler Effect

[*]the abundance of light elements in the visible Universe

[*]cosmic background radiation interpreted as remnant heat

 

The problems with these pillars (and I've always had this issue) is that the theoretical logic is exceptionally circular and affected by the "culture of the times." The observations support "Big Bang" only if you assume the observations support "Big Bang". The Big Bang theory cannot be deduced from the observations in a provable way.

 

Because experimental evidence and observations have cast much doubt on the original hypotheses of the Doppler qualities of the light, the Big Bang theory itself has been revised innumerable times. Most recently something like 23 competing theories of Universal Expansion were tested against WMAP observations and revealed that only one theory held . That theory provided unknowns on both the matter and energy sides of the general relativity equation (dubbed "Dark Matter" and "Dark Energy" respectively). These observations and verifications also upheld that the Universe was "flat" (neither open nor closed).

 

If, for the sake of proof by contradiction, one were to assume that there was no Big Bang (heresy, I realize) then we can assume no mysterious initial "explosion" to propel the expansion and resulting redshift, yet we cannot dismiss the observational existence of the three pillars above.

 

Since we cannot, without assumption, assume the redshift is caused by recession (Doppler) we must find another explanation. By Occam's Razor, we would look to the next logical candidate (one we don't fully understand mind you). My own conclusion is that the redshift is due to "expansion" which is occuring only within gravitational fields.

 

For instance, when we look at the core of our own galaxy (of which we simply don't do enough, IMHO), we would "measure" the diameter from our own relative perspective. However, if we resided in the core, the curvature of space due to gravitation would be such that the distances are actually much larger.

 

The preponderence of light elements such as Hydrogen, Deuterium, Helium, can be easily explained by known processes such as star formation, nuclear fusion and fission, and especially major phenonmena such as galactic collisions.

 

The background radiation itself cannot be explained without a better understanding of the nature of light itself and its interaction with gravity. For instance, if one were to assume that the microwave radiation was nothing more than the resonance of fully formed galaxies throughout the Universe, on a scale heretofore unimagined, the observations (fuzziness, equal proton/neutron distribution) would not contradict that assumption. After all the parallax of particles at that enormous (unknown) distance could very well prevent the resolution of a single photon and instead result in "summing" of photons of extremely high wavelength. Because matter consists of equal parts photons and neutrons, then the apparition of deuterium spectra would not be a surprise at all.

 

The two most critical things to consider, if assuming there is no Big Bang, are the facts that we observe nothing but light in some wavelength. Secondly, that the observation of light may have an inherent "limit" due to the field natures of light and gravity and the enormous distances light must travel. The assumption that the light does nothing but redden across a distance as enormous as 15 billion light years (perhaps much further) cannot be proven. Nor do we have any decent models of what extremely distant light would look like to someone in the center of a massive gravitational field that increased in strength over time.

 

Consider that if Big Bang were not assumed, then we might conclude something completely different about the light we view and might have predicted the following before the observations were made:

1. The Hubble Telescope's observations of innumerable fully formed galaxies at previously unpredicted distances.
   
2. The WMAP observations that the CMB is not homogenous.
   
3. Chandra observations of thousands of black holes in the core of the Milky Way.
   

 

Further (and finally) if we were to stop assuming a "beginning" and take into account that QM delayed-choice experiments point to the possibility that our own perception of time's arrow may be nothing more than a multi-dimensional vector, then we might conclude that the other physical evidence supporting the notion of an explosion might be better related to Gamma Ray Bursts and galactic collisions than one single universal phenomenon.

 

My point is that the Big Bang theory cannot be easily proven by contradiction, and furthermore that the assumption of "no Big Bang" does not contradict the known observations and experiments. We simply don't know because we ourselves are within a gravitational field we don't fully understand, nor do we fully understand the nature of consciousness and observation itself, as the current state of QM demonstrates. (Sorry for the touch of meta-physics but I think it drives the point home.)

The redshift is not interpreted as a Doppler Effect. Is interpreted as having a cosmological origin, so is called "Cosmological Redshift". The contribution of Doppler Effect to the observed redshift is very small

The initial singularity of the Big Bang does not need to be a point.