The End of Cosmology

[modest]

I read this:

 

http://arxiv.org/PS_cache/arxiv/pdf/0704/0704.0221v3.pdf

 

a while ago. Seems to be a leopard of the same spots.

 

I think it'd be better called, the end of evidence of the big bang - but that wouldn't catch as much attention I suppose.

 

-modest

[Mike C]

I read this:

 

http://arxiv.org/PS_cache/arxiv/pdf/0704/0704.0221v3.pdf

 

a while ago. Seems to be a leopard of the same spots.

 

I think it'd be better called, the end of evidence of the big bang - but that wouldn't catch as much attention I suppose.

 

-modest

 

I accessed that article and it quickly changes to an encoded scrap text.

Does that happen to you?

 

Mike C

[Little Bang]

I think Hydro brings up an interesting point. If the local galaxies in say a 100 million light year sphere are showing any signs of contraction why wouldn't I assume that the rest of the universe is acting the same way?

[jackson33]

I think Hydro brings up an interesting point. If the local galaxies in say a 100 million light year sphere are showing any signs of contraction why wouldn't I assume that the rest of the universe is acting the same way?

 

BBT only suggest space is expanding, the internal volume of the Universe. Regardless where an object is (Earth), the further from that object the greater the increase of space between objects. That object, its host (Milky Way) and components in its cluster, though expanding in space between, would be proportionately less, than distant objects and there formations.

No doubt each cluster of matter and there objects, even under BBT, act much the same as ours.

 

In 100 billion years, more or less, if BBT is correct and we were around (won't be), the night sky would still have stars, much like today. Again if expansion is a correct theory, that expansion works against gravity...an extra force to maintain that free fall into or toward other objects...

[CraigD]

I think Hydro brings up an interesting point. If the local galaxies in say a 100 million light year sphere are showing any signs of contraction why wouldn't I assume that the rest of the universe is acting the same way?

In a sense, astrophysicists such as Krauss do assume this. In their description, clusters of galaxies throughout the universe will form “supergalaxies” (since a typical cluster has only a few large galaxies, its supergalaxy won’t be greatly bigger than an ordinary galaxy, on the order of a few hundred thousand LY) in about 100 billion years, while the increasingly rapid metric expansion of space redshifts the light from beyond into undetectability.

 

Although local clusters of galaxies appear to be gradually contracting in this manner, there’s strong evidence that distant galaxies can’t gravitationally interact with enough force to do the same. As Expansion increase the distance between them at an increasing rate, the gravitation force between bodies in distant galaxies becomes even less. So while cluster of galaxies can form supergalaxies, these supergalaxies can’t form super-super-galaxies.

In 100 billion years, more or less, if BBT is correct and we were around (won't be), the night sky would still have stars, much like today.

In a sense, the Krauss and Scherrer article agrees. To a naked human (won’t be any ;)) eye, or a low-resolution telescope, the night sky won’t look much different than at present, because observed in this way, it’s lit mostly by nearby (within 1000 LY) stars, of which there’ll be roughly the same number in 100 billion years as now.

 

A big difference, visible only to instruments capable of “deep field” observations, is that when the dimmer areas between stars are examined, they won’t be found to contain many dim, distant galaxies and individual stars. Unlike today, as smaller areas of the sky are surveyed, a point will be reached where no stars appear in them. Assuming about [math]10^{12}[/math] stars in the predicted supergalaxy, this will happen at about 1.4 arcseconds, within the capability of present day instruments like the Hubble, which has better than a 0.1 arcsecond pixel size for deep field observations. A deep field observation will show none of the complicated shapes we currently see, because only individual and chance conjunctions of stars will be visible. This difference would be visible even using 19th century telescopes, which were capable of detecting that some astronomic objects were not perfect points.

[LaurieAG]

I have just finished reading the print article and thought that it revealed a couple of important things worth looking into in further detail.

 

First Hubble showed that galaxies were so far away that they really were independent collections of stars, just like our own galaxy. Second, he discovered a simple relation between the distances to galaxies and their velocities. The velocity was directly proportional to its distance from us: a galaxy twice as far away as another was moving twice as fast. This relation between distance and velocity is exactly what happens when the universe is expanding.

 

Would we have an expanding universe if a galaxy twice as far away from us as another galaxy and the other galaxy were both actually moving at the same velocities as us with a similar orbit around their respective galactic centers? Are we the center of the universe or what?

 

Our own experience demonstrates that even when we have data, the correct cosmological model is not so obvious. For example, from the 1940's to the 1960's, with the edifice of observational cosmology resting on Hubble's discovery of the expanding universe, some astrophysicists resurrected the idea of an eternal universe: the steady state universe, in which matter is created as the universe expands, so that the universe as a whole does not really change with time.

 

An expanding steady state universe? Pardon me but isn't that what is supposed to happen around the event horizon of a black hole or even in a vacuum under quantum theory etc?

 

If density = mass/volume and energy=mass*c^2 then volume = energy/(density*c^2).

 

With c and energy constant:

 

Volume increase = density decrease.

Volume decrease = density increase.

 

If the volume increases and the density decreases then mass doesn't just pop out of the air to make up the difference.

 

If the volume decreases and the density increases then mass doesn't just disappear into thin air.

 

Y'know, I feel kinda safe living in an eternal steady state universe that will never allow anybody to build a time machine in all eternity, let alone a 100 billion years.

[jackson33]

Under BBT; Space is expanding, opposed to matter moving away. The closer you are to that expansion, the quicker the appearance of movement (proportionate). If a center, in theory, there would then be no movement other than natural velocity. Our Galaxy is thought to travel 300-600 m/p/s, the Universe expanding 30k m/p/s if C and much more per other estimates.

 

Fred Hoyle, generally regarded as the 'Father' of modern Steady State theory (1949), in an attempt to explain the appearance of expansion, came up with inflation or a forced increase in the cube space for matter. He felt or thought matter (hydrogen) could form naturally in empty space. One atom per billion years and from a cubic foot or so of space. Assuming this where true and had been going on forever, trillions of trillions of years and with no beginning and that space itself had no end, your going to have problems...IMO.

 

Most that oppose BBT today or feel the Universe or eternal in existence, feel matter simply replaces itself, or is in an eternal regeneration. Stars are born from dead or extinct star material, go through existence, die and the process unending. Where hydrogen is coming from, the problem for this as some of the stars does fuse into the other, heavy elements not capable of being used in star formation or combustion into fusion. My opinion, is this comes from the formation process of the star itself. The reverse of BBT, when the original elements where mostly Hydrogen and basically a reverse process to 'nucleosynthisis'.

 

I certainly wouldn't concern myself with safety, under any theory. You, our planet, our solar system and everything in the Universe today will pass on many times under the generation process many times, before any end.

[CraigD]

First Hubble showed that galaxies were so far away that they really were independent collections of stars, just like our own galaxy. Second, he discovered a simple relation between the distances to galaxies and their velocities. The velocity was directly proportional to its distance from us: a galaxy twice as far away as another was moving twice as fast. This relation between distance and velocity is exactly what happens when the universe is expanding.

Would we have an expanding universe if a galaxy twice as far away from us as another galaxy and the other galaxy were both actually moving at the same velocities as us with a similar orbit around their respective galactic centers?

The Hubble Flow motion that Krause and Scherrer are describing is in a direction parallel to a line between observer and observed, not at a right angle to it.

 

This is what is predicted to be observed in any system of bodies that once occupies a small volume, then expands to a much larger volume, via ordinary mechanical effects, provided attractive forces between the bodies are not significant on a large scale. It’s also what’s predicted if the space expands – the “metric expansion of space” of conventional cosmology, which alternately could be described as a standard “measuring stick” unit contracting. It’s predicted with any combination of these two effects.

 

Consider the speed of bodies each with the mass [math]m[/math] of a typical galaxy ([math]10^{42} \,\mbox{kg}[/math]) separated by a distance [math]d[/math] in circular orbits about a common center, [math]v_O = \sqrt{\frac{mG}{d}}[/math], and the outward speed given by the Hubble flow [math]v_H = H d[/math] for various distances:

                                   Speed (m/s)
                    Distance (m)    Orbit   H Flow
Nearest dwarf galaxy     2.365e20  5.322e5  5.440e2
Andromeda galaxy         2.365e22  5.322e4  5.440e4
Local group              6.172e22  3.295e4  1.420e5
Virgo supercluster       1.892e24  5.951e3  4.352e6
1/10th visible universe  3.086e25  1.473e3  7.098e7
Visible universe         3.086e26  4.659e2  7.098e8

Note that at the scale of a group of galaxies (ours, the Local Group, contains about 40 galaxies), Hubble flow and orbital mechanics are of similar significance, but that at larger scales, orbital mechanics are insignificant.

 

Also note that this comparison naively ignores the gravitational effects of “dark matter”, which most astrophysicists believe constitute 95% or more of the mass of the universe, and significant simultaneity issues due to the great distances involved. I think it shows, however, that the Hubble flow dominates the mechanics of the universe at scales larger than clusters of a few tens of galaxies.

Are we the center of the universe or what?

IMHO, this question is at the hear of one of the major sources of misunderstanding and miscommunication about cosmology.

 

Almost any person with a decent astrophysics education will unsually answer this question something like: “everywhere in the universe is the center of the universe”, to which a person with a sound understanding of language-based semantics will reply “that’s by definition impossible!” To the best of my understanding, this confusion stems from an astrophysicists desire to avoid the misconception the larger universe appears of effects a point in any galaxy differently than one in any other. If the universe is of finite mass, as its believed by nearly all physicists to be, it does have a center, but, as the usual answer attempts to explain, this location isn’t observably any different from any other with similar local conditions (eg: within or outside a galaxy, solar system, body, etc.)

 

This is true because of the insignificance of gravity (and, generalizing, any interaction to which an inverse-square law applies) at very large scales that I attempted to illustrate in the first part of this post.

 

The best short answer to the question “are we at the center of the universe?”, IMHO, is to go with the most likely correct answer “no”, simply ducking potentially confusing issues above.

An expanding steady state universe? Pardon me but isn't that what is supposed to happen around the event horizon of a black hole or even in a vacuum under quantum theory etc?

There’s a lot of reasonable and interesting speculation that the very strong gravity near the event horizon of a black hole might allow the virtual particle-antiparticle pairs described by quantum physics to become actual particles, and that real particles may, very, very rarely, just “pop into existence” in gravitationally flat space.

 

I can’t do the detailed calculations necessary to make theoretical predictions of these kinds (which require assumptions of great uncertainty even among people who can, as this 2008 popular science paper by John Baez summarizes), but my impression is that these effects are much too small to produce matter at the rate required by the Steady State Theory referred to by Krause and Scherrer.

[LaurieAG]

I certainly wouldn't concern myself with safety, under any theory. You, our planet, our solar system and everything in the Universe today will pass on many times under the generation process many times, before any end.

 

Hi jackson33,

 

I was just making the point that time travel will not exist in an eternal solid state universe. The water and oxygen (along with almost everything else) gets recycled on this planet, that's got nothing to do with time travel allowed by exotic theories.