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The Search for Dark Matter and Dark Energy

Posted by ScuttleMonkey on from the someone-needs-to-turn-on-a-light dept.

mlimber writes "The New York Times Magazine has a lengthy article on dark matter and dark energy, discussing the past, present, and future. 'Astronomers now realize that dark matter probably involves matter that is nonbaryonic ["meaning that it doesn't consist of the protons and neutrons of 'normal' matter"]. And whatever it is that dark energy involves, we know it's not 'normal,' either. In that case, maybe this next round of evidence will have to be not only beyond anything we know but also beyond anything we know how to know.'"

8 of 212 comments (clear)

  1. Can dark matter just be.. by Wah · · Score: 4, Interesting
    ...big black holes that have already eaten everything around them? (i.e the "edges" of the universe)

    ..."in-transit" energy from 100,000,000,000 stars?

    ...large amounts of completely non-reflective dust and asteroids?

    ...a side effect of over-estimating the size of the universe? (i.e. stars like our 5 billions light years away don't exist anymore)

    /real questions
    //just curious..

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    1. Re:Can dark matter just be.. by rasputin465 · · Score: 3, Interesting

      So there are at least two completely different, totally unrelated dark matter problems.

      You're right that the universal baryon density doesn't specifically constrain galactic dark matter. But Occam's Razor suggests there is only one dark matter problem. Besides, you would have to explain why galaxies would have one type of dark matter while galaxy clusters have a completely different kind (and we know intra-cluster dark matter is non baryonic). It's much easier to explain the dark matter evidence at all scales by postulating just one culprit.

  2. "Dark energy" by omnilynx · · Score: 2, Interesting

    At this point, dark energy is really nothing more than a fudge factor. It's certainly nothing like the normal concept of energy. We don't even know if it's a cosmological constant or if it varies over time and space, let alone whether it's a property of spacetime or some form of particle. So far, I'm still unconvinced that it actually exists: it seems more likely to me that the current theories are simply slightly off in their formulas, and can be resolved without recourse to another of Occam's entities.

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    1. Re:"Dark energy" by Anonymous Coward · · Score: 1, Interesting

      Dark matter in some varieties has been observed. Asteroids, dust clouds, neutrinos, brown dwarfs. It refers to matter which observationally almost certainly must exist unless gravity behaves radically differently, which there's precious little basis for believing. But this matter is inconvienently not lit up. Which is sort of a pain in the ass for our insturments which near completely on electro-magnatism. That so much of this dark matter must be something exotic is a statistical inferance, it's a huge budget short fall, which isn't covered by even the error bars on the probable occurance of observed dim objects. So Occam's much overused razor leads us to believe that if it must exist, and it's probably not "normal", that as unlikely as it would have been to posit this from the outset, it must be very odd indeed.

      Dark energy is similar. Fact: the matter in the universe is accelerating apart. This takes energy. As it turns out, a fantastic amount. Why can't we see this energy? It's there, in fact in quatities that it makes up most of what we percieve as the universe. And yet it's thus far resisted out investigations. It's presence isn't up for debate. Where it chooses to hide itself, that's the mystery.

  3. Re:How about ... by Biogenesis · · Score: 2, Interesting

    I thought this too for a long time, but it seems that the only evidence for dark matter isn't just galactic rotation curves. I'm having trouble finding it through Google, but while I was studying astrophysics last year we were shown an image of a gravitationally lensed quasar, but without any visible foreground stars. The lensing may have been caused by a clump of baryonic matter that just happened to be cold and not emitting much light, but it may also be dark matter. So unfortunately it's not quite as simple as, say, using general relativity to calculate a galactic rotation curve.

    Personally I'm still hopeful that Newtonian gravity doesn't work at large distances, someone discovering some new gravitational physics (like, working out a quantum model for gravity is a good start) would be more exciting to me personally than just knowing that there's something that's mostly undetectable floating around in the universe.

    Oh, and very large bodies also obey the laws of quantum physics, just taking them into account is a waste of time as the effects are insignificant. AFAIK there isn't a situation where QM doesn't apply correctly. In the same way as you can take special relativity into account when you're driving in your car, the maths works and it's correct but the effect is so small it is truly insignificant.

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  4. Funny you should say that... by Anonymous Coward · · Score: 1, Interesting

    Because "knowing how to know" is what the word Scientology means.
    And on that note, no, I'm not a Cult of Scientology member :)

  5. Re:Travel and other considerations? by monster811 · · Score: 2, Interesting

    If it doesn't interact by the electromagnetic force, it cannot affect anything chemically. If it doesn't interact by the strong force, it cannot cause nuclear reactions. Even if it interacts by the weak force, the effect would be equivalent to the neutrinos already coursing through us. To my understanding, it's an explanation for effects specifically by gravity, which we already are experiencing.

  6. Re:Not really... by antonyb · · Score: 2, Interesting

    Dark matter seems like far from settled science to me. But it always does amaze me how dark matter proponents tend to treat it's existence just like the followers of intelligent design treat God.

    See also: String Theory proponents.

    ant.