Dark Matter: Anything Practical About It?

Posted by Ethan on April 15, 2008
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Yesterday, my good friend (and SWAB reader) Brian wrote a great comment about the practical reasons to explore space, where he talked about the overall economic impact that Space Exploration has had on the economy, as well as the impact it has had on our knowledge and understanding of the Earth, its environment, and how to manage/mitigate the threats to it. And that’s wonderful for exploring our Solar System and others.

But what do I do in the meantime? After all, this isn’t what I study or explore. So I asked this:

The practical arguments as to why exploration of space is worthwhile certainly hold a lot of water! But by that argument, the stuff that I do — looking for dark matter, trying to figure out dark energy, galaxy formation, the fate and birth and evolution of the Universe, etc. — is completely worthless. I agree that understanding the Universe helps us to understand our place/role in the Universe, but is there then a practical argument for understanding the stuff that is unrelated to us?

And so I thought about it: long-term, is there anything practical about studying dark matter? Well, the most abundant and efficient source of energy in the Universe is nuclear fusion, such as what goes on in our Sun: 4 Hydrogen nuclei fuse into one Helium nucleus, emitting about 25 MeV of energy per Helium nucleus. That’s about 0.7% efficient: for every kilogram of hydrogen that you fuse, 0.7% of that mass becomes pure energy. Is there anything more efficient than that? Sure: if you collide a hydrogen nucleus (a.k.a. a proton) with its anti-matter counterpart (an antiproton), that is 100% efficient!

Well, this happens to all particles and antiparticles: you run them into one another, and what you get out is 100% pure energy. There’s very little anti-matter in the Universe, and most of it would be very very detrimental to a spaceship, as it would annihilate with whatever it came into contact with first!

But dark matter, which we know doesn’t interact much with (and certainly doesn’t annihilate) normal matter, is very special. Because all realistic models of dark matter that we have consist of a very special property: Dark Matter is its own antiparticle! The Universe is also full of dark matter. So, if we could figure out how to collect and collide dark matter particles, we would have a 100% efficient source of energy that would virtually be unlimited. Because finding dark matter is 5 times easier than finding normal matter in the Universe.

Is this a long way off? You bet. But is this, long-term, the most efficient source of energy imaginable? Well, let’s see, at 100% efficient? You bet. And that’s the most practical thing I can think of about dark matter. All it’ll take, I’m sure, are some good sci-fi writers to put this in the public’s imagination!

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Comments

  1. #1 benhead
    April 15, 2008

    It may be best not to think too much about whether the pure science you’re studying has any practical application, because honestly, you just can’t know at this point. You don’t even know what dark matter is, so figuring out how to put it to use is a practical impossibility.

    Back in the 1920s, scientists discovering quantum mechanics figured it had no practical use whatsoever. Some decades later, your blog (along with a sizable chunk of everything we do) relies upon modern electronics, which couldn’t be designed without a deep understanding of QM.

    You put the research in research & development. :P

  2. #2 Vanamonde
    April 15, 2008

    okay, but…I have never heard of any evidence of dark matter in our solar system. I have always heard about dark matter perhaps in the halo of the galaxy or some thousands of light years away. So before we collect any, there is the small problem of intragalactic travel that will not be solved anytime soon.

  3. #3 ethan
    April 15, 2008

    We’ve got dark matter in our solar system — no need to worry about that. Dark matter is in our galaxy, our solar system is in our galaxy, so not to worry. Moreover, we can calculate just what the density of dark matter is in our solar system. Turns out it’s about one-tenth the density of normal matter in our part of the galaxy. That’s still a lot; about 10-25 grams per cubic centimeter. But it could be a lot more, depending on gravitational effects. I’m working on figuring that one out, actually. Ask me again in a couple of months…

  4. #4 Cable
    November 20, 2008

    there are at least 2 great applications. One is, since the world is made up of matter and has gravity that anti-matter will create anti-gravity(hovercrafts). Second, matter(gravity) affects light traveling(bends it toward it over distance) where darkmatter(anti gravity) would bend light away from it causing the antimatter to be invisible to sight. If the repulsion is great enough you could hide other objects that are within the lines of antimatter flux field.

  5. #5 ethan
    November 20, 2008

    Well, the problem is that both dark matter and anti-matter have *normal* gravity, not anti-gravity. If there were anti-gravity, we would have applications for it, to be sure. But as far as we’ve observed, we don’t.

    Unfortunately.

  6. #6 Cable
    November 20, 2008

    If dark matter has normal gravity then wouldn’t it collect debree(dust,rocks) that we would be able to see instead of a void and a magnetic field? I am sure the dark matter chunk would have to be big enough. But there should be all sizes.