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      CommentAuthorAngus
    • CommentTimeJan 31st 2012
     
    Many people find dark energy to be repulsive, so are we any further ahead?
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      CommentAuthorTrim
    • CommentTimeJan 31st 2012
     
    Well one very, very big mystery to just a very big mystery, progress maybe?
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      CommentAuthorAngus
    • CommentTimeJan 31st 2012
     
    I make it one unproven idea to two unproven ideas. That's regress.
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    Go ahead, work out the consequences of a repulsive mode of gravity. It's actually very interesting and leads to all kinds of things you might not expect at first.

    (Things, by the way, that nobody has ever observed anywhere, but that doesn't seem to stop the speculators.)

    The Real Scientists that I know all seem to believe that gravity can never be repulsive, and that antimatter will be "normal" in its gravitational effect and response to other masses, matter or antimatter notwithstanding.
    • CommentAuthortensor
    • CommentTimeJan 31st 2012
     
    It would certainly be revolting....um, er...revolutionary.
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      CommentAuthorAngus
    • CommentTimeJan 31st 2012 edited
     
    I used to be a real scientist and I am racking my branes to figure out what would be the difference, except for the fact that orbits wouldn't work and the universe would fly apart and there would be thermodynamic consequences...
    - but - if you assume that antimatter ATTRACTS antimatter, and repels matter - then it seems like a possible explanation of why there is no antimatter to speak of around here...
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    Posted By: Angusif you assume that antimatter ATTRACTS antimatter, and repels matter


    F=mA, remember? Now give the m a negative sign. Now... attach a rope and pull on your antimatter.
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      CommentAuthorAngus
    • CommentTimeFeb 1st 2012
     
    I didn't say antimatter has negative mass (putatively). I said the gravitational force between terrene and contraterrene could be repulsive.

    -F =G m(terrene) M(contra) / r^2
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      CommentAuthorTrim
    • CommentTimeFeb 1st 2012
     
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      CommentAuthorTrim
    • CommentTimeFeb 1st 2012
     
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      CommentAuthoralsetalokin
    • CommentTimeFeb 1st 2012 edited
     
    Posted By: AngusI didn't say antimatter has negative mass (putatively). I said the gravitational force between terrene and contraterrene could be repulsive.

    -F =G m(terrene) M(contra) / r^2

    Yes, I do know what you said.

    F=G(mM)/r^2, right? We seem to agree on that in a non-MONDian regime anyway. I'd feel more comfortable if this relation held no matter matter or antimatter, and it seems a lot more easy to reverse the sign of one of the masses than to postulate some other "g" that is negative and that somehow comes into play when two positive masses, one antimatter, interact.
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      CommentAuthorAngus
    • CommentTimeFeb 1st 2012
     
    Aesthetically, I agree. And since aesthetics seems to be important in these things I expect we will find that antimatter has positive gravitational attraction to matter.
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      CommentAuthorTrim
    • CommentTimeFeb 1st 2012
     
    Soon, they will have enough antimatter to do the gravitational experiment.
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      CommentAuthorTrim
    • CommentTimeFeb 14th 2012
     
    • CommentAuthortensor
    • CommentTimeFeb 15th 2012
     
    Why can't it be just a lot of plain old ordinary matter, that's not all clumped together into galaxies?
    Or a lot of old black holes or neutron stars?
    Why does it have to be mysterious dark matter?
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      CommentAuthoraber0der
    • CommentTimeFeb 15th 2012
     
    Posted By: tensorWhy does it have to be mysterious dark matter?

    My AVON consultant told me last week that dark matter, or MiB, is a placeholder for a unknown cause of an observable effect. According to him, we shouldn't call it a bunch old black holes until we are certain.
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      CommentAuthorTrim
    • CommentTimeFeb 15th 2012
     
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      CommentAuthorTrim
    • CommentTimeMar 6th 2012
     
  3.  
    Posted By: aber0der
    Posted By: tensorWhy does it have to be mysterious dark matter?

    My AVON consultant told me last week that dark matter, or MiB, is a placeholder for a unknown cause of an observable effect. According to him, we shouldn't call it a bunch old black holes until we are certain.
    Preacher man taught us that such placeholders are an offense to God.
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      CommentAuthorTrim
    • CommentTimeApr 18th 2012