Dark Matter: What Is It & How Was It Formed?

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SUMMARY

Dark matter is a form of matter that cannot be detected through emitted radiation, but its presence is inferred from gravitational effects on visible matter, such as stars and galaxies. The discussion highlights that the rotational speeds of galaxies cannot be explained solely by visible mass, leading to the hypothesis of dark matter. Candidates for dark matter include massive remnants like white dwarfs and neutron stars, as well as particles such as neutrinos and WIMPs (Weakly Interactive Massive Particles). The Bullet Cluster study serves as a significant indirect proof of dark matter's existence, demonstrating a spatial offset between the total mass and baryonic mass in a galaxy cluster.

PREREQUISITES
  • Understanding of gravitational effects on celestial bodies
  • Familiarity with particle physics concepts, including neutrinos and WIMPs
  • Knowledge of galaxy rotation curves and their implications
  • Basic comprehension of the Bullet Cluster study and its significance in astrophysics
NEXT STEPS
  • Research the properties and behavior of neutrinos in astrophysics
  • Explore the implications of WIMPs as dark matter candidates
  • Study the Bullet Cluster and its role in dark matter evidence
  • Investigate current technologies and methods for dark matter detection
USEFUL FOR

Astronomers, astrophysicists, and students interested in cosmology and the fundamental nature of the universe will benefit from this discussion on dark matter and its implications for our understanding of the cosmos.

  • #31
ranrod said:
I have an admittedly uninformed question about this...
My question is this: Why not just say, "there's an unknown force or error in our understanding of the universe?" Why make it a definite object? Making it an object seems like a narrow-minded way of approaching an unknown problem and assumes too much.

You're right. Your question is uninformed, and calling scientists "narrow-minded" based on your own ignorance says rather more about you than them.

As it happens, there is a theory, called MOND, which attempts to explain galaxy rotation curves by changing the gravitational force law (which is equivalent to adding another force). This theory has its proponents, but is not very popular. One problem is this theory is that different galaxies seem to have different proportions of dark matter. This is natural if dark matter is a substance, but it is decidedly unnatural - and hard to explain - if one tries to explain dark matter as MOND. MOND would suggest a universal curve, and that's not really what's seen.
 
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  • #32
Vanadium 50 said:
You're right. Your question is uninformed, and calling scientists "narrow-minded" based on your own ignorance says rather more about you than them.

I'm afraid I did sound rather disrespectful phrasing it that way, sorry about that. I was saying it's odd that the standard response is not, "we don't know", but instead, "it's this object we just made up called dark matter that we can't find". I got to learn how to rite more better & articulate me thoughts more proprly.

Even if it was a tremendously large concentration of WIMPS, for instance, wouldn't it be just as puzzling to figure out why they're hanging out around the halos of a galaxies?
 
  • #33
I think dark matter/dark energy is a frustrating thing for lay people. The way its presented in popular science might have something to do with it. "Here is this stuff that comprises most of the universe, but there's no way to see it or detect it, and it doesn't interact with anything except by way of gravity."

I remember getting excited when it occurred to me that if the universe was spinning from the moment of the big bang, maybe it was just centrifical force. But I realized that if that were the case, somebody a lot smarter then me would have thought of it already.

While people without backgrounds can certainly question things, there are generally good reasons when physicists achieve some consensus, especially since its such a competitive field. I don't "like" dark matter either, but I realize I don't have the necessary background to form a coherent criticism.
 
  • #34
Galteeth said:
While people without backgrounds can certainly question things, there are generally good reasons when physicists achieve some consensus, especially since its such a competitive field. I don't "like" dark matter either, but I realize I don't have the necessary background to form a coherent criticism.

Thanks Galteeth. I want to apologize once again for sounding condescending. That wasn't my intention, and I'm sorry it came off that way. I meant it when I said I need to work on my writing skills. The work physicists do on this subject is amazing and I didn't mean to be dismissive.

I was trying to express surprise at the prevalency of the physical object "dark matter" theory as an explanation for things, and seeing if anyone would explain more background on that. I think I came off as condescending, criticizing and seemed to be offering crack-pot theories. Although I must say, I got a warm smile when I read Galteeth's idea about it :) I've had similar feelings before about other things, and it reminded me of it.
 

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