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Space Science

Imaging Dark Matter With Gravity 14

Posted by timothy from the bringing-us-together-and-the-universe-apart dept.
Phase Shifter writes: "I was looking at Lucent's website when I found a link to this article about how a dim galaxy cluster was discovered by its gravity instead of its light. They say the same technique could be used to determine the distribution of dark matter in the universe."
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Imaging Dark Matter With Gravity More

Imaging Dark Matter With Gravity

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  • Will look for gravity waves and such too (little more direct then the gravity lenseing effect): http://www.ngst.stsci.edu/ [stsci.edu]
  • This reminds me of the first detections of extrasolar planets, which have been found by the eccentricity (or "wiggle" if you want to be cute) in the position of their star they cause with their gravitational pull as they orbit the star.

    Of course, gravity is notoriously weak and therefore difficult to use as an accurate measurement tool. I could be wrong, but I think they're starting to spot extrasolar planets by other means that are more satisfactory. Maybe they'll find something similar for dark matter.

  • Basically, scientists think there is this stuff we can't see called "dark matter" because their theories' predictions about the amount of matter in the universe are *WAY* off. I think it would be more "scientific" to modify the theories to fit the evidence. Atleast that's what they taught me in school.
    • There are fine reasons to think there is about 10 times the matter out there than can be seen, such as galaxies could not rotate as they do without more mass. Theory my ass, it's standard calculations, nothing tricky. in fact, one could even go so far as to say that EVIDENCE requires the extra mass, and they are bending theories to fit the evidence.
    • But then what you are left with is a strict definition of dark matter, not a theory about space in general. Theories by definition are universal, and to "modify" these theories to fit one piece of evidence causes other aspects to go out of whack. When you empirically alter theories to fit data, you describe a one-case scenario. In other words, you have a model, such as the model of the moon that is mentioned in another article here. Now, if you could sit down and point out flaws in the equations and theories that would case this discrepancy, then great, but I don't think you can, and neither can I.
    • You are SO right! What a silly idea. That there might be stuff out there, like dust and planets and particles and things, that doesn't give off it's own light. That's the last time I listen to scientists.
  • Future scientists will conclude that Matt Groening was right: dark matter is basically cute alien shit.

  • I'm wondering if this method of finding objects by mass instead of light (using a nifty property of physics called "gravitational lensing") is in any way related to finding black holes by their gravitational pull or the electromagnetic emissions? In a way, both methods find things by indirect measurement because you don't have to see it to know it's there. You can simply measure the object's effects on everything else around it (e.g. black holes pulling in stars and other matter that generates electromagnetic radiation).

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