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10 Comments

1. 1. JRWermuth 05:37 PM 8/14/12

   Damn, SA videos too often fail to play even with my very-fast cable connection. Time to increase broadband?

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2. 2. jtdwyer 01:33 AM 8/15/12

   Great! Dark matter simulations that almost look real...

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3. 3. scientific earthling 07:42 PM 8/15/12

   The more I think of it the more dark matter seems to the the source of our universe, no singularity, no big bang, just some dark matter failing to annihilate itself and matter and anti-matter flying off and simply existing. So where is all the anti-matter?
   
   Matter and anti-matter do not have to have similar opposite properties, perhaps anti-matter has stronger gravitation (is gravity a true force?) and all the anti-matter clumps together more than matter does. Then I think of the black holes at the centre of every galaxy; an anti-matter star with two event horizons one on the antimatter side and one on ours, in-between matter & anti-matter annihilation. Maybe the temperatures of anti-matter stars are measured in millions of degrees kelvin on the negative side of the temperature scale. I like scalars, there so much simpler than vectors and convey the message.
   
   
   

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4. 4. voyager 12:18 AM 8/18/12

   A layman's plea for a lead to a good online guide to supposed/proposed relations between matter, anti-matter, and dark matter. Specific questions: the video says dark matter is invisible because it doesn't absorb light. But wouldn't absorbing light make it invisble, and reflecting light make it visible? Reflection isn't mentioned.
   
   Second, not seeing it is one thing, but how does its ability to affect "our" matter gravitationally square with the apparent mutual inability of the two to interact physically in the hard-nose sense, WHAM! with one another?

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5. 5. jtdwyer in reply to voyager 03:59 AM 8/18/12

   I'm just a lay person also, but I can say that these 'matters' are subject to a great deal of speculation, especially in the media. For a tutorial, I suggest you begin by reading the easily accessible:
   http://en.wikipedia.org/wiki/Dark_matter
   http://en.wikipedia.org/wiki/antimatter
   They also contain links to many related topics...
   
   Be careful not to confuse the two, since they are completely unrelated. In fact, you bring up an interesting question, since there should be dark anti-matter, or anti-dark matter, but I've not seen any mention of it before...
   
   Very generally, though, the presence of dark matter is only inferred by the identification of gravitational effects that seem to exceed those that could be produced by the estimated mass of the visible matter present. These conditions only occur for very large aggregations of massive objects (i.e., galaxies & galaxy clusters) - which would be the case if the methods for estimated masses for enormous compound objects of mass inherently produced underestimations. They could also occur if the evaluation of gravitational effects were improperly overstated (too complex to go into here).
   
   At any rate, dark matter cannot be illuminated by an external light source, since it does not reflect or absorb/re-emit light or electromagnetic energy: it is perfectly transparent. It also cannot (often) interact with other matter. These properties are similar to neutrinos, except that neutrinos have nearly zero rest mass and therefore continuously linearly self-propagate through spacetime. Dark matter must be undetectable yet hang around large configurations of ordinary matter, significantly increasing total mass (by up to a factor of 10).
   
   In order to produce its required gravitational effect on galactic rotation, dark matter must extend far beyond the visible boundaries of a galaxy. Some people like to think that dark matter might be tiny primordial black holes & such, but it's hard to understand why they wouldn't all collapse into the center of a galaxy, and they are thought to be generally short-lived.
   
   Antimatter is naturally produced by beta decay and interactions between matter and gamma rays. Matter has certain properties such as a specific rest mass and electric charge state. Antimatter has the equal electrical charge quantity but the opposing polarity (+/-). When two otherwise identical matter/antimatter elements interact, their equal but opposite charge polarities cancel out, releasing all of their mass-energy.
   
   I do like your idea of anti-dark matter annihilation!

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6. 6. voyager 10:40 AM 8/18/12

   JT, thanks for the generous time spent on sorting things out for me, an English major. The one element unaddressed in all the online info I can understand, not all that much, is the relation, if any, between dark matter and anti-matter.
   
   And I still think dark matter proponents are getting away with something when they endow their darling with gravitational consequences and at same time deny it any other features of matter. I see them and their dark energy cohorts like a bunch of medieval Ptolemaics: "A new orbital perturbation in Mercury? Throw another epicycle on the model." Blacking out all knowable features of the dark matter model a priori looks like a preventive and therefore a particularly shameless epicycle. To a layman, anyway.
   
   I don't deserve your compliment re: the anti-dark matter annihilation; that was Scientific Earthling's idea. But I like it.

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7. 7. jtdwyer in reply to voyager 01:00 PM 8/18/12

   Ah, yes! Kudos to scientific earthling!
   
   I'm still hoping to help annihilate the the whole dark matter business. If you like, please see my earlier essay and/or a more recent commentary posted at
   http://www.sciencewithoutfiction.com/Articles_Essays.html
   
   BTW, my sister has taught high school English and French for many years, but has no idea about (or interest in) any scientific stuff, so you're doing quite well - best wishes!

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8. 8. scientific earthling 04:03 AM 8/22/12

   Sorry guys I did not tick the box to get an email when someone posted a comment her.
   
   jtdwyer: Been to your site and hey I'm 4 years older than you. I knew you would like this idea, even though you did not like my idea time was not a dimension, I now accept time as a dimension, because it takes time for information to travel. We know Betelgeuse in Orion is ready to pop, hey it may have already, only we don't know yet. However no-one can travel back & forth in time to re-experience the past or glimpse the future.
   
   Well my understanding of dark matter is: In the almost nothingness of space-time, matter and anti-matter spontaneously appear and normally annihilate each other almost instantaneously; thereby leaving nothing where there was nothing. Remember matter and anti-matter are just energy, Higgs boson imparts mass to the particles. (don't like using the word particle, the are energy quanta) We are now almost certain it or a similar Wimp (weakly interactive massive particle) exists.
   
   We must also thank Vera Rubin for our understanding of the universe. She told us the mass of our universe was wrong, it could not explain the orbits of the stars in galaxies especially if Kepler got it right. Me, I think the weak force "gravity" is what we got wrong, it is probably a pseudo-force. Accelerating in a spaceship creates a gravitational force experienced by those in the spaceship. That is why the space-station in "2001 A space odessy" was like like a large wheel, spinning to generate centrifugal force that acted like gravity.
   
   Now to explain thing (Vera threw a cat amongst the pigeons)scientists determined that the total dark matter (even though it exists for a very short time) in the universe, at any instant is enough to account for the shortfall. It did account for a fair bit, but things still did not add up. Then they come up with dark energy, no one has proved it, it is a kind of anti-gravity pushing all matter apart.
   
   Me I wanted things simple, so, first get rid of the singularity, then the big bang, then accept dark matter, then imagine its properties. What I came up with is my first post. Cant for the love of me figure out why someone else had not thought of this before.
   
   Another though: The weak force is just the electro-magnetic force experienced in the nuclease, so why not dump it too.

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9. 9. jtdwyer in reply to scientific earthling 05:52 AM 8/22/12

   Well, I just like the idea of dark matter annihilating itself!
   
   As for Vera Rubin, she (and many others) made the fatal error of improperly presuming that stars in the disks of spiral galaxies must independently rotate just like planets in the Solar system (they do look like planetary systems). The only Galaxy Rotation Problem was that each star within a galactic disk gravitationally interacts with hundreds of billions of other galactic objects, not just a dominating central mass... Without exception, galaxies are not planetary systems...

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10. 10. scientific earthling in reply to jtdwyer 05:49 AM 8/23/12

    jtdwyer: I did click the link "Reply" but get "you are commenting to null's comment", probably ghostery to blame, on this Mint Maya operating system computer.
    
    In my last response I left-out my conclusion about gravity, I posted the idea that gravity could be a pseudo force and acceleration causes a force similar to gravity to. But now let me clarify.
    
    We need dark matter and dark energy to explain the accelerating expansion of our universe. Clusters of galaxies are flying apart at increasing speeds, they are accelerating. So could gravity we experience be a result of this acceleration, the graviton has never been found. What I am suggesting is we experience gravity because the universe is expanding at an accelerating rate.
    
    Now to come to the stars revolving around the central black hole.
    
    Revolving around a central massive object is the result of the revolving object falling towards the central massive object, but its horizontal velocity (perpendicular to the falling direction) is just sufficient to keep it in orbit around the object pulling it. If we conclude that gravity of the other stars in the galaxy neutralise the pull of the black hole we should not have stars revolving around the centre of the galaxy.

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