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Dark Energy - important new information

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Bikerman
Dark-energy has long been a mystery in physics and much research has been devoted to explaining it (Cosmological Constant, Quintessence et al).
A new paper challenges the whole concept and appears to show that Dark Energy is not necessary to explain the observable universe.
http://www.abc.net.au/science/articles/2007/12/21/2124258.htm?site=science

This is very interesting stuff and well worth a look.
newolder
http://eclipse2006.bikerman.info/iPMBBCR42008.htm#darkness

discusses where David is wrong here. The accelerated expansion of the universe clearly shows up in WMAP &c where the CMBR is red-shifted more after it passes through a void, not less as he reportedly writes (i.e. it would be less in any expanding circumstance other than accelerated expansion.) . ed.
Bikerman
Excellent. I'll take some time to read through this later.
Thanks ed.
HamsterMan
I'm still sceptical about the whole dark energy thing, and also quantum physics.

Alot of the things they claim just doesn't make much sense, and seems to just be there to explain something that might be explained in a much simpler way.

Like this guy that claimed that humanity could possibly have shortened the life span of the universe by observing dark energy (according to quantum physics). That it has to be conscious observer for the state to change just makes me very sceptical about the very idea.

Oh, and I know nothing about physics. Razz
Bikerman
HamsterMan wrote:
Oh, and I know nothing about physics. Razz

Err..so you are sceptical based on ignorance? Perhaps the solution would be to learn?
HamsterMan
Bikerman wrote:
HamsterMan wrote:
Oh, and I know nothing about physics. Razz

Err..so you are sceptical based on ignorance? Perhaps the solution would be to learn?

Well, not really. I do know the very basics of quantum physics and why the dark energy theory exists.
Bikerman
HamsterMan wrote:
Bikerman wrote:
HamsterMan wrote:
Oh, and I know nothing about physics. Razz

Err..so you are sceptical based on ignorance? Perhaps the solution would be to learn?

Well, not really. I do know the very basics of quantum physics and why the dark energy theory exists.

OK well why do you not 'believe' quantum theory? Are you aware that it works? When I say it works I mean it really, really works to an astonishing degree of accuracy. I suspect your problem might be with the interpretations that are applied to quantum theory (ie trying to explain the theory in terms of things we are more familiar with). This is inherently problematic and has troubled many great minds. It does not mean that quantum theory is wrong, it simply means that we have no adequate way to explain it in terms of 'it's like....', largely because it isn't 'like' anything we have experience of.
newolder
HamsterMan wrote:
I'm still sceptical about the whole dark energy thing, and also quantum physics.


The story of dark energy really began in 1998:: http://physicsworld.com/cws/article/print/19419

Quote:

Alot of the things they claim just doesn't make much sense, and seems to just be there to explain something that might be explained in a much simpler way.


A lot?

Quote:

Like this guy that claimed that humanity could possibly have shortened the life span of the universe by observing dark energy (according to quantum physics). That it has to be conscious observer for the state to change just makes me very sceptical about the very idea.


Do you have a reference for this?

Quote:

Oh, and I know nothing about physics. Razz


That's how we came to build t'internet and then moved on to Grids of varying dimension: it's all 'out there': go figure or ask questions... Very Happy ed.
HamsterMan
Quote:
Do you have a reference for this?

Yepp, here.
http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/11/21/scicosmos121.xml
Bikerman
I think the important passage is :
Quote:
And Prof Krauss stresses that resetting the cosmic clock was not something we have done to the universe but rather what our cosmologically observations may imply about our knowledge of the cosmic clock: "I did not mean to imply causality - namely that our measurement itself reduces the lifetime of the universe - but rather that by being able to make our measurement we may thus conclude that we may not be in the late decay stage."
newolder
Bikerman wrote:
I think the important passage is :
Quote:
And Prof Krauss stresses that resetting the cosmic clock was not something we have done to the universe but rather what our cosmologically observations may imply about our knowledge of the cosmic clock: "I did not mean to imply causality - namely that our measurement itself reduces the lifetime of the universe - but rather that by being able to make our measurement we may thus conclude that we may not be in the late decay stage."


The stress is due to Krauss, the HamsterMan seems to have mis-interpreted. But it is "The Telegrope", not known as a science journal around here but who knows?

Quote:
"cosmologically observations"
and i thought it was an English language comic.
Rolling Eyes ed.

Last edited by newolder on Tue Jan 22, 2008 9:37 pm; edited 1 time in total
Bikerman
True enough. The article was pretty badly (sensationalistic) put together and obviously sought to make a splash headline where non really existed.
bloodtiger10
does dark matter / is dark matter real i mean come on just so they think they can capture it how does it really excist!!!
Bikerman
Don't confuse dark matter and dark energy. Dark matter is the stuff which needs to be there in order to explain how galaxies hold together but which we cannot, at the moment, detect because it doesn't reflect radiation sufficiently to be observed.
The main evidence for the existence of Dark Matter is indirect (eg calculations of the kinetic energy present in Galaxies which exceeds the gravitational binding energy which would hold them together).
According to a paper in 2006, however, Dark energy has been observed directly.
http://astro.berkeley.edu/~mwhite/darkmatter/dm.html
http://en.wikipedia.org/wiki/Dark_matter
EanofAthenasPrime
HamsterMan wrote:
I'm still sceptical about the whole dark energy thing, and also quantum physics.

Alot of the things they claim just doesn't make much sense, and seems to just be there to explain something that might be explained in a much simpler way.

Like this guy that claimed that humanity could possibly have shortened the life span of the universe by observing dark energy (according to quantum physics). That it has to be conscious observer for the state to change just makes me very sceptical about the very idea.

Oh, and I know nothing about physics. Razz


So you base your skepticism of quantum physics on a Frihoster...
DoctorBeaver
I read a paper recently about MOND (MOdified Newtonian Dynamics) which tries to explain the acceleration in the expansion of the universe without resorting to dark energy. I have to admit that I didn't understand it all, but the originator (Moti Milgrom) puts a cohesive, well-considered argument in favour of it.

I've always been a bit wary of dark energy theories, so I suppose my bias draws me towards theories such as MOND.

Here's a good site for reading about it http://www.astro.umd.edu/~ssm/mond/
Bikerman
Here is an interesting conversation on the matter:
http://onpointradio.org/shows/2007/05/20070531_b_main.asp

(link provided by Newolder in another place).

Also well worth a watch is Penrose's lecture on the BB
http://real.bnl.gov/ramgen/bnl/penrose.rm
newolder
DoctorBeaver wrote:
I read a paper recently about MOND (MOdified Newtonian Dynamics) which tries to explain the acceleration in the expansion of the universe without resorting to dark energy. I have to admit that I didn't understand it all, but the originator (Moti Milgrom) puts a cohesive, well-considered argument in favour of it.

I've always been a bit wary of dark energy theories, so I suppose my bias draws me towards theories such as MOND.

Here's a good site for reading about it http://www.astro.umd.edu/~ssm/mond/


It is an interesting observation that maths can be twisted to fit any observation set.

I have found no predictions from this theory. If it doesn't predict supersymmetry (massless fermions interacting with massive bosons) AND supersymmetry is shown to exist in nature, can we bin it then, please? Very Happy
Bikerman
The answer must surely be yes. Any 'theory' which does not predict observable phenomenon within the scope of that theory must surely be relegated to hypothesis (assuming that such a theory did have observational/experimental support to start with). If such a 'theory' actually does not allow for an observable phenomenon then the relegation must be, not to hypothesis, but to fantasy.
newolder
Quote:
The character table for E8
or
how we wrote down
a 453060 x 453060 matrix
and found happiness
David Vogan
Department of Mathematics, MIT


http://math.mit.edu/~dav/E8TALK.pdf

Will take a bit of time to soak-in, i fear...

Great times! Cool

This is page 224 of 224 in the pdf minus a picture... Why it calls itself 'p. 33/32' is way beyond me. Silenced

Quote:
In Which we Come to an Enchanted Place. . .
1/8/07 9 A.M. Finished writing to disk the character table of E8.
Fokko du Cloux
December 20, 1954–November 10, 2006
The character table forE8 – p. 33/32

Here's an image of Fokko du Cloux
DoctorBeaver
newolder wrote:
DoctorBeaver wrote:
I read a paper recently about MOND (MOdified Newtonian Dynamics) which tries to explain the acceleration in the expansion of the universe without resorting to dark energy. I have to admit that I didn't understand it all, but the originator (Moti Milgrom) puts a cohesive, well-considered argument in favour of it.

I've always been a bit wary of dark energy theories, so I suppose my bias draws me towards theories such as MOND.

Here's a good site for reading about it http://www.astro.umd.edu/~ssm/mond/


It is an interesting observation that maths can be twisted to fit any observation set.

I have found no predictions from this theory. If it doesn't predict supersymmetry (massless fermions interacting with massive bosons) AND supersymmetry is shown to exist in nature, can we bin it then, please? Very Happy


As I said, I don't really understand MOND that well but I don't see the connection between it and supersymmetry. MOND is about motion - in particular, acceleration - rather than particle physics, is it not? Why should such a theory predict supersymmetry? It would be akin to expecting a theory of fluid dynamics to predict that your head would hurt if you banged it against a brick wall.
nisibdv
All this thing about dark energy and dark energy is very very similar and bring us strong remembrences of what occurred not so long ago in the history of physics with the ether thing. I suppose something similar will happen with this dark energy matter thing. A great theory by a great mind wil come and destroy all this ad-hoc supositions of the existance of dark things. Don't you think that?
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