Dark matter and Dark energy

robinson said:
Forget the "fact" it doesn't emit, adsorb, or re-radiate any form of EM,
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Neither do neutrinos.

it also doesn't attract either matter, or itself,
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Not so. That's rather the whole point: we can detect its presence because it does attract matter.

nor does it form structures,
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What scale are you talking about? On a small scale, neither do neutrinos. And on a large scale, it most certainly does.
 
sol invictus said:
Yes it is, but the coloring in that image corresponds to the density of dark matter as reconstructed via its gravitational lensing effects. It's roughly analogous to using sonar to determine the location of an object underwater - it might be much too far away or too dark to see, but you can use sound instead to detect it and reconstruct an image of it.
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Thanks but I was under the impression that this was in the x-ray spectrum.
 
DanishDynamite said:
I've recently read somwhere that at most 4% of our Universe consists of regular matter as we know it. Some 26% consists of Dark Matter and some 70% consists of Dark Energy.

A) How are these numbers arrived at? How is the "Dark Energy" converted to matter?

B) What ever happened to the question of where all the anti-matter went?
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These are make-believe things because scientists do not like not knowing and much more so do not like admitting that they don't know.
 
sol invictus said:
No - read the caption here:

http://chandra.harvard.edu/photo/2006/1e0657/

The colors correspond to matter as detected with lensing. Pink coincides with ordinary matter emitting in X-ray, but blue (which is most of the mass) isn't emitting anything.
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I did before. I never was quite clear on it until I focused on the little word...COMPOSITE.

Just figured since it was on Chandra's website...well you know :)
 
JEROME DA GNOME said:
Nope, but it is not a picture of dark matter.

Dark matter is inferred because we have no explanation for many things observed.

One can not take a picture of an inference.
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So what caused all the gravitational lensing in the blue parts of the image?
 
JEROME DA GNOME said:
Nope, but it is not a picture of dark matter.

Dark matter is inferred because we have no explanation for many things observed.

One can not take a picture of an inference.
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So if the picture isn't fake and we can't photograph an inference, what is it?
 
~enigma~ said:
You deny the existance of black holes?! Can someone please explain why we are wasting time and energy with this guy.
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Haha, good question. I have him on ignore, but similar posters keep popping up and spouting nonsense.

It's a pretty entertaining game of whack-a-woo.
 
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robinson said:
My point stands. Plasma is a conductor of electricity. Gas and dust clouds don't glow, emit EM radiation of all kinds, or allow electric currents to flow for millions of miles through them. Plasmas do.
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Neon isn't a gas nor a conductor? What planet you from?

 
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I heard on the Starstuff podcast recently that there's a new idea about dark energy.

You know how time dilation works in relativity, right? The presence of a gravitational field warps spacetime and makes time run more slowly.

Well, apparently someone much better at maths than I am has run some numbers and come up with the idea that the time dilation caused by the presence of galaxies causes there to be a significant difference between time measured in galaxies, and time measured in intergalactic voids. According to this theory, dark energy is an artifact caused by our viewpoint within the time-dilated gravitational field of our galaxy. It's the difference in the passage of time between in-galaxy points of view and extragalactic points of view which makes it appear that the expansion of the universe is accelerating.

Interesting, no?
 
arthwollipot said:
I heard on the Starstuff podcast recently that there's a new idea about dark energy.
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If you're talking about the idea it sounds like you're talking about, it doesn't work. In fact I had a hand in debunking it myself.

But you might be talking about something else.

JEROME DA GNOME said:
Dark matter and dark energy are scientific discoveries?


Please present the scientifically measurable characteristics of these discoveries.
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First of all, dark energy is much more speculative and less well-understood than dark matter. The fact they both have "dark" in their names doesn't mean they're identical.

Dark matter is certainly a discovery, yes. The bullet cluster observations you had so much cognitive dissonance over just now are a direct observation of it, confirming many of the characteristics which were already known from many other independent measurements. Off the top of my head those characteristics include its mass, its distribution around galaxies, its temperature, bounds on its lifetime, its interactions, and probably more.
 
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