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Thread: 5% what?

  1. #1 5% what? 
    Forum Bachelors Degree Demen Tolden's Avatar
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    Hello.

    I've been learning a bit of particle physics lately and I keep hearing a statement that goes something like "we know a lot about a small part of everything there is. From cosmology we have learned that all the stars, planets, and the matter we know about only make up about 5% of everything that exists." Would someone be so kind as to further explain this idea. I'd look for it myself, but the only real hint I can find is cosmology, and that sounds much to broad a search to find the answer.


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  3. #2  
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    Do a search on dark matter.


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  4. #3  
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    Ah dark matter, the nice commodity that quantum physiscts have come up with to explain Einstein's cosmological constant. It's just as funny as when they say 'exotic matter' exisits too, what's next? Doesn't matter for irrelevant scientific problems? Dark matter would not exist or have been theorised about if it were not for the cosmological constant, remeber though that dark matter is a quantum way of looking at the cosmological constant, relativity has a different idea and so does string theory. So you'll have to choose which one you want. At the moment there is as much evidence for one and the other to prove or disprove each other, so you've nothing to lose really. But also remember that dark matter is another theory-too many believe it to be fact and that leads to all new theories based on that 'fact' whcih end up igglydy piggdly. Dark matter is the same as when you're are child and your parent tells you to do something. "Why?" the child says. "Because I said so" replies the parent. Something you never understand until you reach a level of understanding to understand it-the same applies with understanding dark matter if it exists. Everything is relative to the observor.
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  5. #4  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Actually, the cosmological constant is more akin to dark energy. The 5% things comes from taking the known behavior of the universe and calculating that that implies a certain amount of mass. Then looking at a statistical sum of the visible universe, you get somewhere around 5% of that. I forget how they calculate the ratio of dark matter to dark energy though.

    As an aside, I remember a picture that compared the visible signature of two galaxies coliding to the gravimetric signature. The fact that they differed in almost exactly the way the matter/dark matter ratio would predict was interesting evidence that dark matter might not be just an idea. (Of course, I probably explained that poorly.)
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  6. #5  
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    there is a 5% chance I hit the same key twice.

    (5 & %).

    What if I wrongly used a sift key????
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