How Dark Matter Interacts with the Human Body

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Magical Realist, Sep 16, 2013.

  1. Magical Realist Valued Senior Member

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    "Dark matter must collide with human tissue, and physicists have now calculated how often. The answer? More often than you might expect.

    One of the great challenges in cosmology is understanding the nature of the universe’s so-called missing mass.

    Astronomers have long known that galaxies are held together by gravity, a force that depends on the amount of mass a galaxy contains. Galaxies also spin, generating a force that tends to cause this mass to fly apart.

    The galaxies astronomers can see are not being torn apart as they rotate, presumably because they are generating enough gravity to prevent this.

    But that raises a conundrum. Astronomers can see how much visible mass there is in a galaxy and when they add it all up, there isn’t anywhere enough for the required amount of gravity. So something else must be generating this force.

    One idea is that gravity is stronger on the galactic scale and so naturally provides the extra force to glue galaxies together.

    Another is that the galaxies must be filled with matter that astronomers can’t see, the so-called dark matter. To make the numbers work, this stuff needs to account for some 80 per cent of the mass of galaxies so there ought to be a lot of it around. So where is it?

    Physicists have been racing to find out with detectors of various kinds and more than one group says it has found evidence that dark matter fills our solar system in quantities even more vast than many theorists expect. If they’re right, the Earth and everything on it is ploughing its way through a dense sea of dark matter at this very instant.

    Today, Katherine Freese at the University of Michigan in Ann Arbor, and Christopher Savage at Stockholm University in Sweden outline what this means for us humans, since we must also be pushing our way through this dense fog of dark stuff.

    We know that whatever dark matter is, it doesn’t interact very strongly with ordinary matter, because otherwise we would have spotted its effects already.

    So although billions of dark matter particles must pass through us each second, most pass unhindered. Every now and again, however, one will collide with a nucleus in our body. But how often?

    Freese and Savage calculate how many times nucleii in the average-sized lump of flesh ought to collide with particles of dark matter. By average-sized, they mean a 70 kg lump of meat made largely of oxygen, hydrogen carbon and nitrogen.

    They say that dark matter is most likely to collide with oxygen and hydrogen nuclei in the body. And given the most common assumptions about dark matter, this is likely to happen about 30 times a year.

    But if the latest experimental results are correct and dark matter interactions are more common than expected, the number of human-dark matter collisions will be much higher. Freese and Savage calculate that there must be some 100,000 collisions per year for each human on the planet.

    That means you’ve probably been hit a handful of times while reading this post.

    Freese and Savage make no estimate of the potential impact on health this background rate of collisions might have. That would depend on the energy and motion of a nucleus after it had been hit and what kind of damage it might wreak on nearby tissue.

    It must surely represent a tiny risk per human but what are the implications for the population as a whole? That would be an interesting next step for a biological physicist with a little spare calculating time."---http://www.technologyreview.com/view/427461/how-dark-matter-interacts-with-the-human-body/

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  3. Magical Realist Valued Senior Member

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    New Kind of Dark Matter Could Form 'Dark Atoms'

    by Charles Q. Choi, SPACE.com Contributor | June 10, 2013 05:32pm ET

    A new type of dark matter that forms “dark atoms” may clump into flat disks around galaxies, physicists suggest in a new theory called the double-disk dark matter model.

    The mysterious dark matter that makes up most of the matter in the universe could be composed, in part, of invisible and nearly intangible counterparts of atoms, protons and electrons, researchers say.

    Dark matter is an invisible substance thought to make up five-sixths of all matter in the universe. Scientists inferred the existence of dark matter via its gravitational effects on the movements of stars and galaxies.

    Most researchers think dark matter is composed of a new type of particle, one that interacts very weakly at best with all the known forces of the universe save gravity. As such, dark matter can almost never be seen or touched, and rarely even collides with itself. [Gallery: Dark Matter Across the Universe]

    This might not hold true for all forms of dark matter, though. Now, some researchers suggest a new kind of dark matter could exist, representing about one-fifth of all dark matter in the universe, making it potentially as plentiful as conventional matter.

    Dark atoms

    "There is no good reason to assume that all the dark matter in the universe is built out of one type of particle," study author Andrey Katz of Harvard University told SPACE.com.

    These new dark matter particles would essentially consist of heavy "dark protons" and light "dark electrons." They would interact with each other far more than other dark matter particles to form "dark atoms" that use "dark photons" to interact through a sort of "dark electromagnetism," much as regular protons and electrons interact through photons in conventional electromagnetism to build the atoms making up the stuff of everyday life. If dark atoms are possible, they could react with each other for dark chemistry, much as regular atoms interact chemically.

    "The dark world might even be as diverse and interesting as the visible world," Katz and his colleagues wrote May 23 in the journal Physical Review Letters.

    The interactions between dark protons and dark electrons could make them lose energy over time. As such, they might slow down enough to clump into flat disks around galaxies, just like regular matter does. In contrast, most dark matter apparently forms roughly spherical haloes around galaxies, stars and planets.

    This concept means galaxies would have two disks, one made of regular atoms and one of dark atoms, which is why the investigators call their idea the double-disk dark matter model.

    "The double-disk dark matter idea is a novel twist on an intriguing concept — that the physics of dark matter might be as complicated and interesting as the physics of ordinary matter is known to be," said theoretical physicist Sean Carroll of the California Institute of Technology, who did not take part in this study.

    Carroll and his colleagues had earlier suggested "the basic possibility of a dark force very similar to electromagnetism — a long-range force with positive and negative charges," he said. "Such a model implies dark radiation, dark magnetic fields, and a host of other interesting phenomena. But we only had one kind of dark-matter particle in our model; to go to the world of dark atoms and dark chemistry requires more kinds of particles. That's the direction the new papers are taking."

    The gravitational effects of a dark atom disk on stars in galaxies could eventually be detectable via the European Space Agency's Gaia space observatory scheduled to launch in October, which aims to map the movement of approximately 1 billion stars in the Milky Way.

    "This is how we might first detect this dark disk," Katz said.

    Moreover, since this novel form of dark matter is expected to be much slower on average than regular dark matter, it should be more susceptible "for capture by the Earth, by the sun, or other heavy celestial objects," Katz said. "Annihilation of this dark matter captured by the sun can result in neutrino fluxes, which can be measured directly by the IceCube Neutrino Observatory on the South Pole."

    In addition, the dark electrons and dark protons the scientists propose might also have antimatter counterparts — dark anti-electrons and dark anti-protons. When these particles collide with their counterparts, they would release gamma rays, the most energetic form of light, which telescopes should be able to spot. Furthermore, dark atoms might also have formed clouds of dark plasma, ripples in which might have influenced the formation of the early universe and thus have visible effects on large-scale cosmic structures that exist nowadays.

    "Theories of dark matter with new forces provide a wonderful playground for theorists to develop new models of particle physics," Carroll said. "The hard part will be getting the astrophysics right — how does the dark matter evolve and cluster? In the observable world, the presence of electromagnetic fields makes that a very hard problem — when you add dark electromagnetism to the mix, it will only get harder!"---
     
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  5. AlphaNumeric Fully ionized Registered Senior Member

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    Dark matter interacts with the human body via gravity and the electroweak force. Precisely as neutrinos do. Trillions of neutrinos pass through your body every second, right now as you're reading these words. Maybe one every few days will actually hit a particle in your body, the rest will not even notice you're there.
     
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  7. common_sense_seeker Bicho Voador & Bicho Sugador Valued Senior Member

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    @ MR: Nice picture, where's it from? I'm a MOND + exotic matter person, so I'm more interested in "How Exotic Matter Interacts with the Human Body". This will be the biggest topic of discussion in the near future imo.
     
  8. Magical Realist Valued Senior Member

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    So when a dark matter particle collides with an atom in our body, is that a gravitational interaction or an electroweak interaction? Or something else?
     
  9. Magical Realist Valued Senior Member

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  10. common_sense_seeker Bicho Voador & Bicho Sugador Valued Senior Member

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    A simulation then. I read this and laughed:

    Dark matter mainstreamers REALLY can't the wood for the trees can they!
     

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