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It Doesn’t (Dark) Matter…

October 10, 2005

Back during my days as a freshman at Vanderbilt, I took a course on astronomy.  And I actually enjoyed it, which is more than I can say of pretty much every other science course I took in the span of my academic career.

Sometime near the end of the semester, we came to the subject of dark matter.  Allow me to explain.  Physics dictates the movement of things.  The ballistic trajectory of a cannonball, the orbit of a planet, the rotation of a galaxy.  Only…galaxies rotate faster than their mass suggests they should.  To explain this faster-than-expected rotation, astronomers and astrophysicists came up with the concept of dark matter – matter than cannot be seen, detected, or measured in any way, but that somehow adds mass to the galaxy, thus making it rotate faster.

When I heard this in class, my hand shot up.  I didn’t buy it.  I mean, seriously, which is more likely?  That galaxies rotate faster than they should because of some mysterious, undetectable "stuff"?  Or that our physics is wrong?  It wouldn’t be the first time.

The professor came back with the whole "it’s too complicated" routine…but I never have been able to swallow the dark matter Kool-Aid.  In the years since, I’ve stood by my opinion.  There is no dark matter.  It’s the science that is flawed.

So you can imagine my mild exhuberance to come across THIS PAPER, which states that, "using general relativity in place of Newtonian gravity, [there is] no need to assume the existence of a halo of exotic dark matter to fit the observed rotational curves".

In other words, the physics was flawed, and dark matter is crap.

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8 Comments leave one →
  1. Tim permalink
    October 10, 2005 9:05 pm

    Are “dark matter” and anti-matter the same thing?

    Just asking because I’ve seen multiple proofs of anti-matter — including the actual production of anti-matter as part of the super-collider experiments right there in Texas.

    So while I also don’t buy the “dark matter” explanation of galatic spin speed, I don’t think it makes the existence of anti (dark?) matter crap. Too much proof it exists.

    Sounds more likely that your prof was full of crap — just an old school linear Newtonian physicist who hadn’t kept up with his studies. Newtonian physics only work when speeds and mass levels are pretty much in a range with what we experience every day. As soon as you get to very high speeds or very large masses (or very small masses, like in quantum physics), Newton goes out for a smoke and Einstein takes over the DJ booth.

    Prof should’ve known better. Probably not used to having people actually think about what he was saying. Heh.

  2. October 11, 2005 6:15 am

    Dark matter and anti-matter are two completely seperate things.

  3. Tim permalink
    October 11, 2005 12:15 pm

    Thanks for clarifying.

    Still sounds like it was your prof that was full of it — the idea that Newtonian physics don’t sufficiently explain things like galaxies isn’t new. Surprised that nobody pointed out that relativity-based physics explained galactic motion before now.

    Impressed that you managed to find that paper in the big haystack that makes up the web.

  4. October 11, 2005 2:36 pm

    LOL – “Newton goes out for a smoke and Einstein takes over the DJ booth.” Hee!

  5. October 11, 2005 9:53 pm

    If Dark Matter = Crap, then that explains what happens after I would drink a lot of cheap beer in college. I’m still stcuk on the whole butt smugler thing. I’ll bet that they believe in Dark Matter.

  6. October 12, 2005 5:32 pm

    In response to all that stuff Matt said, and all that stuff Tim said I say simply:

    “Yeah…all that stuff….that’s what I was going to say!”

    LOL. No I’m totally out my league on this one…Physics beat the hell out of me at GHS. Only reason I passed is because we had Amanda Thomas’ dad build our hovercraft for us and we got an A.

    Ok you brainiacs, so what’s the physics behind tripping on my shoelaces all the time growing up?

    I remember that Torque = Mass multiplied by something or other. Do I get points for that?

  7. Tim permalink
    October 13, 2005 8:44 pm

    After reading JB’s explanation, I’ve now reversed my position. Dark matter is crap, and I must certainly admit that it DOES exist.

    Must be a lot of cheap beer in the galaxy to slow it down that much.

  8. November 3, 2006 5:31 pm

    I know I’m posting this a year after the original post came up, but….

    The arguments for dark matter are many and varied. The GR paper that said that just GR can explain rotation curves was flawed.

    The real question was between dark matter and so-called MOND, or “MOdified Newtonian Dynamics.” The idea is that we don’t fully understand gravity on the largest scales. It’s a mater of taste whether modifying gravity or whether introducing unknown dark matter is a bigger tooth fairy. Most of us preferred dark matter for a lot of reasons, including that it fits with a lot of other observations. However, what really decides isn’t taste, but data…..

    There is now unambiguous evidence that dark matter must exist. A post on my own blog about the matter:

    http://brahms.phy.vanderbilt.edu/~rknop/blog/?p=90

    Here’s a post from Cosmic Variance on the matter:

    http://cosmicvariance.com/2006/08/21/dark-matter-exists/

    Your professor (was it Weintraub? Saumon? Heiser? Hall? Gotta be one of those guys back then) wasn’t full of it, nor was dark matter crap. He was telling you the best explanation astronomers have. Now, years later and with more evidence in hand, it’s clear from direct evidence as well as the many lines of indirect evidence we had previously that dark matter does indeed exist.

    -Rob

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