In the Dark on Dark Matter

I think I need someone far cleverer than me to explain this to me. Dark Matter [wiki]…

 

In astronomy and cosmologydark matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable byemitted or scattered electromagnetic radiation.[1] Its existence was hypothesized to account for discrepancies between measurements of the mass of galaxiesclusters of galaxies and the entire universe made through dynamical and general relativistic means, and measurements based on the mass of the visible “luminous” matter these objects contain: stars and the gas and dust of the interstellar and intergalactic medium.

According to observations of structures larger than galaxies, as well as Big Bang cosmology interpreted under the Friedmann equations and the FLRW metric, dark matter accounts for 23% of the mass-energy density of the observable universe. In comparison, ordinary matter accounts for only 4.6% of the mass-energy density of the observable universe, with the remainder being attributable to dark energy.[2][3] From these figures, dark matter constitutes 80% of the matter in the universe, while ordinary matter makes up only 20%.

Dark matter was postulated by Fritz Zwicky in 1934 to account for evidence of “missing mass” in the orbital velocities of galaxies in clusters. Subsequently, other observations have indicated the presence of dark matter in the universe; these observations include the rotational speeds of galaxiesgravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies.

Dark matter plays a central role in state-of-the-art modeling of structure formation and galaxy evolution, and has measurable effects on the anisotropies observed in thecosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than that which interacts with electromagnetic radiation. The largest part of dark matter, which does not interact with electromagnetic radiation, is not only “dark” but also, by definition, utterly transparent.[4]

As important as dark matter is believed to be in the cosmos, direct evidence of its existence and a concrete understanding of its nature have remained elusive. Though the theory of dark matter remains the most widely accepted theory to explain the anomalies in observed galactic rotation, some alternative theoretical approaches have been developed which broadly fall into the categories of modified gravitational laws, and quantum gravitational laws.[5]

Look, I jut don't get it. I mean I do get it in that I understand the basic concept – when we look at the universe and see all the stuff that we can see we end up with a real problem, that all the observable material around us only accounts for 20% of the matter that should be there if our current understandings of gravity etc are correct.

Is it me, or does that not make you want to argue that either we're very bad at just looking for stuff or maybe our current theories just aren't up to scratch at all? The wiki article goes on to present that latter choice as one possible alternative:

One group of alternative theories to dark matter assume that the observed inconsistencies are due to an incomplete understanding of gravitation rather than invisible matter. These theories propose to modify the laws of gravity instead.

But again, is this just me or doesn't this just all boil down to the fact that really, for all our claims to cleverness and despite all the incredible discoveries we've made about the Universe, we just still don't have a clue?

I have an alternate explanation for why we're still nowhere near close to having anything like a Theory of Everything. Some of you aren't going to like it,

Hebrews 1:3 The Son is the radiance of God's glory and the exact representation of his being, sustaining all things by his powerful word

Now that is really going to mess up any theory built on materialism.

Now, can someone let me know if I'm just getting this hopelessly messed up or is all of this dark matter stuff really an exercise in trying to explain away our ignorance?

(image from ScienceBlogs.com)

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3 comments on “In the Dark on Dark Matter

  1. Hi David,

    I have to admit, I don’t understand all the details either. But I think you’ve got the gist.

    I think it’s just an obvious example of how great science is when it sticks to its purpose; and how useless science is when people try to push it beyond its purpose.

    If science is understood as the constant quest to understand more about the physical universe, premised on the assumption that we don’t know everything, then dark matter is a particularly striking example of the huge potential of science. The ignorance we have w.r.t. dark matter is similar to the kind of ignorance that preceded other great leaps forward in scientific knowledge of the universe (e.g. inexplicable black body spectra preceding quantum theory; observations about the non-existence of the ether leading to relativity, etc.). Dark matter has the potential to turn our understanding of the physical universe on its head, because it forces people to posit creative new theories that can explain it. That’s exciting for most real physicists.

    But when science is (wrongly, but popularly) understood as some kind of settled body of knowledge that can currently explain everything about the physical universe without the need for any further explanation, dark matter is a striking example of how very silly that understanding of science actually is.

  2. Hi David,

    Dark matter. I agree with you the term is not much more than a trekky sounding place-holder for something we don’t know much about. But considering how big and diffuse the universe is I am amazed we can see visible 4%! To the best of my knowledge (which isn’t much) everything we know about the matter outside our atmosphere comes from parts of it having smashed into us (meteroites, etc) or from light that has travelled from it to us (we either see it if it emits light, passes in front of something that emits light, or is near enough to have a gravitational pull on something that emits light).

    Not sure who you have been speaking to, but all of the academics I know in physics and chemistry would agree with you in that science is very much incomplete. Even if it were complete, to say so would kind of jeopardise your chances of getting a grant to study it. Are we just bad at looking at stuff, or are our current theories not up to scratch? Both! There is no point to experimental or theoretical work if you deny the great big yawning chasm between what we do know and what we don’t.

    It think its HOW we go about addressing “the unknown” that gets us into trouble. E.g. Was the universe created? Is stem cell research ok? Can I do what I want if I don’t hurt anyone? People might offer science-based answers for these, but at the end of the day its a question of who and what you trust.

    I guess what I am trying to say here is that dark matter is one of MANY examples of things we don’t fully understand. Its up there with “black hole” and “LGM” (little green men – the original name given to a pulsar when it was first discovered). Some people might use scientific facts as a prop for materialism but surely there is much more going on in their minds.

  3. Thanks Joe, Lots to chew on there. I particularly liked this,

    Even if it were complete, to say so would kind of jeopardise your chances of getting a grant to study it

    which suddenly makes my awe of your own phd slightly diminished wink

    More seriously, you comment,

    Some people might use scientific facts as a prop for materialism but surely there is much more going on in their minds.
    I think it works the other way around. There’s a large segment who approach the facts with the assumption of materialism, and that causes them to skew their interpretation of the data.

    At the end of the day, I’m just struck with how much we don’t know.

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