Voiding the Cosmic Void: We're not at Center of the Universe After All

Dec 10, 2008

Models of the universe that place us near the center of a large, sparse region don't jibe with astronomical observations. Cosmologists at the University of British Columbia reached the conclusion through a new analysis that reaffirms the presence of a perplexing dark energy.

In recent years many studies have indicated that the expansion of the universe is accelerating, which may be due to a mysterious form of dark energy that makes up most of the contents of the universe.

Alternative interpretations have suggested that the accelerated expansion may be merely an illusion, if we happened to live near the center of an enormous cosmic void, empty of most matter.

The researchers examined the latest data, in particular subtle features in the cosmic microwave background radiation (the afterglow of the Big Bang) and ripples in the large-scale distribution of matter. They found that void models, unlike standard dark energy models, do a very poor job of explaining all of the latest data, taken together.

The new study helps to solidify our place in the Universe as a completely typical and unremarkable one. It also reaffirms that most of the stuff in the universe is far from ordinary: the dark energy remains as enigmatic as ever.

Article: J. P. Zibin, Adam Moss, and Douglas Scott, Physical Review Letters(forthcoming)

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User comments : 23

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theophys
3.7 / 5 (6) Dec 10, 2008
Yay dark energy!
Yes
2 / 5 (6) Dec 10, 2008
Dark energy and dark matter probably in the end turns out to be somehow light:)
theophys
4.6 / 5 (10) Dec 10, 2008
Dark energy and dark matter probably in the end turns out to be somehow light:)


Yeah, dark light. It's like light, but totally not.
schultz911
1.5 / 5 (2) Dec 11, 2008
Dark Matter.....cool....now i have something to write my thesis on :D
thales
2.3 / 5 (3) Dec 11, 2008
Apparently the choice is between the Void and the Dark Side. More proof that cosmologists are grown-up sci-fi nerds.
Honor
1 / 5 (2) Dec 11, 2008
maybe a brane in a high dimension is pushing everything apart. or maybe the cosmic background radiation is just the energy vacuum
Noumenon
4.5 / 5 (53) Dec 11, 2008
If you can't detect it, taste it, and pass it through your intestine, then don't give it a name as if it exists as a thing.
Noumenon
4.6 / 5 (53) Dec 11, 2008
Is dark energy the 'duck tape' of modern cosmology?,... stay tuned.
D666
5 / 5 (5) Dec 11, 2008
Apparently the choice is between the Void and the Dark Side. More proof that cosmologists are grown-up sci-fi nerds.


You needed proof??!?!?!
Avitar
1.8 / 5 (4) Dec 11, 2008
If you can't detect it, taste it, and pass it through your intestine, then don't give it a name as if it exists as a thing

Our Galaxy orbits around some thing we can not see or taste and how would we know if it is passing through our intestines? The idea that gravity constant is multi-dimensional may be correct. "Feeling" dark mater just around the "dimensional corner" from us may be future physics.
Roach
2.3 / 5 (3) Dec 11, 2008
Unnamed poster who does not exist,
From my present location I cannot detect you, taste you, nor do I think I can get you to pass through my small intestine. But I can see a post which had to come from somewhere, logic tells me some one or something wrote it. Most input in these boards is via a keyboard, so probably something with fingers, Since you didn't write an infinite number of post to get your post right I'd assume not a monkey, so I'm guessing you are a Human with a Screen name of Avitar.

We can't see something out there, but we can see stuff not doing what it's supposed to something is probably affecting that, Do you want every theoretical substance to be named "that thingy" until we can get a picture of it?
deatopmg
1 / 5 (1) Dec 11, 2008
could these questionable "dark" things really be evidence of a particulate aether as predicted by the full solution to Dirac's equation but thrown out by the Danish don in '32?
NeptuneAD
not rated yet Dec 11, 2008
Whats those comments about Dark Matter being some form of light, I thought light had zero mass.
theophys
not rated yet Dec 11, 2008
Whats those comments about Dark Matter being some form of light, I thought light had zero mass.


You would be correct. Hence, "It's like light, but totally not." My lame sense of humor.
physpuppy
5 / 5 (1) Dec 11, 2008
Whats those comments about Dark Matter being some form of light, I thought light had zero mass.


Very interesting concept - the simplest answer is that the photon has zero ***rest*** mass - since all photons are on the go, they have momentum and thus mass (but see last reference below).

You know that famous equation E=MC^2 - actually the "M" term refers to "rest mass" - and thus the equation is an approximation - when something is moving (and there is always some sort of motion - hence my comment saying "approximation") That famous equation actually has another term - there is a momentum term to the equation.

Here is a nice link that explains it better than I could ever:

http://www.physli...e180.cfm

http://math.ucr.e...ass.html

http://www.newton...0332.htm

http://www.aip.or...5-2.html
physpuppy
not rated yet Dec 11, 2008
Oops - physorg somehow munged the links to photon "mass".

Here they are, tinyurl'ed:
http://tinyurl.com/pmasssans
http://tinyurl.com/bjmuy
http://tinyurl.co...ssnewton
http://tinyurl.com/pmassslow

NeptuneAD
5 / 5 (1) Dec 11, 2008
Thanks for fixing those links, still one link not working though, the following comments were written before those links were fixed.

One question though, if all photons are on the go and (according to your comment), therefore have mass, how does light go so fast, the mass is meant to increase to infinity, also I thought that if a photon has zero mass at rest then if you multiply zero by anything you still get zero, or is there another rule that momentum can multiply a zero value into a larger than zero value.

Following on from that, if I take it that the maximum speed of light is due to its mass, then if one could remove mass from the equation it would possible to travel faster than light.
Roach
5 / 5 (1) Dec 11, 2008
Neptune, good question, the reason a Photon is assumed to have 0 mass is because at speeds of c and at sizes below that of quarks, the differance is moot, matter is energy and in the case of a photon it's all energy. Easy way to observe is in the case of gamma radiation if you force it to stop you result in an electron and a positron. Push them back together and you have a photon on the Gamma wavelength again. That's the only one I memorized. They actually sell little toys which utilize light to spin a vane in a glass tube. Kinda cute, useless, but cute.

Basically it all falls back on e=mc^2 is not an equation, it's a conversion factor between different forms of measurement like KW to HP or gallons to cubic millimeters only it's the equivalency between a said amount of matter and it's equivalent amount of energy.
NeptuneAD
5 / 5 (1) Dec 11, 2008
Right, I get it now, the conversion equation E=MC^2 implies that photons have mass (M) because they have energy (E), but in effect they don't need to have mass since they are constantly on the move they give the same result as if they were stationary with mass (M) without actually having mass (M), I think?

I apologize for moving this discussion away from the topic, so to correct that...

I think it was naive to think we were at the center of the universe in the first place or for that matter in any special place in the universe, but mind you there were times when we thought the earth was flat, sure glad I didn't live in those times, no Google back then.
Roach
5 / 5 (1) Dec 12, 2008
It wasn't naive of you, they just haven't finished carrying out the equations, the earth isn't the center of the universe. I am. :)
physpuppy
not rated yet Dec 13, 2008
Sigh - the URL that got messed up the second time:

http://tinyurl.com/dssb9
physpuppy
5 / 5 (1) Dec 13, 2008
...They actually sell little toys which utilize light to spin a vane in a glass tube. ...


Just a friendly correction:

Those toys do not convert photon momentum - the vanes move because of differential heating of the dark & light parts - its residual air bouncing off faster due to the dark side getting slightly hotter than the light side.

If you put the vanes under a very good vacuum, light doesn;t cause the vanes to move. (would have been nice if momentum of light was the cause...)

physpuppy
4 / 5 (1) Dec 13, 2008
Some references to my last comment concerning vanes of radiometers:

http://tinyurl.com/622rph
http://tinyurl.com/6nwu4g
Alizee
Dec 13, 2008
This comment has been removed by a moderator.
Alizee
Dec 14, 2008
This comment has been removed by a moderator.