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Thread: Quanta: using rocks as DM detectors

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    Default Quanta: using rocks as DM detectors



    i'm skeptical. this is an old technique that is being recycled. i remember from the 1970s that there was a claim to detect the track of a magnetic monopole in mica. that didn't hold up well. rocks are a messy laboratory for 'not geology'.

    https://www.quantamagazine.org/why-t...rock-20190107/
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    Default Re: Quanta: using rocks as DM detectors

    I wonder if density of dark matter in our place in Milky Way is known? Is this negligible value?
    Greg

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    Default Re: Quanta: using rocks as DM detectors

    Quote Originally Posted by greqmaa View Post
    I wonder if density of dark matter in our place in Milky Way is known? Is this negligible value?
    It's known from the Milky Way rotation curve in terms of total mass density. Particle number density is unknown only because the masses of DM particles are not known.
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    Default Re: Quanta: using rocks as DM detectors

    Ok. I've done some google/wikipedia "resarch" and I found article (link below) where local DM density is estimated to 0.5 GeV cm^-3 what is equivalent in mass to about half of proton or neutron per cm3.
    Big or small value - I have no idea.

    https://arxiv.org/abs/1501.01788v1
    Greg

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    Default Re: Quanta: using rocks as DM detectors

    Quote Originally Posted by greqmaa View Post
    Ok. I've done some google/wikipedia "resarch" and I found article (link below) where local DM density is estimated to 0.5 GeV cm^-3 what is equivalent in mass to about half of proton or neutron per cm3.
    Big or small value - I have no idea.

    https://arxiv.org/abs/1501.01788v1
    It's a reasonable value.
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    Default Re: Quanta: using rocks as DM detectors

    I made calculation to show how much DM could "live" in our vicinity (in more friendly units):

    There is about 10^13 kg of DM in sphere of radius 1 au.
    Big or small: assuming rock density 3000 kg/m3 it is equivalent to rock ball with radius 1 km.

    Sorry nFA for hijacking thread!
    Greg

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    Default Re: Quanta: using rocks as DM detectors

    Quote Originally Posted by greqmaa View Post
    I made calculation to show how much DM could "live" in our vicinity (in more friendly units):

    There is about 10^13 kg of DM in sphere of radius 1 au.
    Big or small: assuming rock density 3000 kg/m3 it is equivalent to rock ball with radius 1 km.

    Sorry nFA for hijacking thread!
    Was the thread hijacked? I didn't notice. That's not a lot, not too little.

    Actually, it's a reasonable approach you've taken. On one occasion a person tried to argue that there was 5 times the mass of the Sun that should be inside the 1 au sphere about the Sun. They argued this because there is 5 times as much dark as baryon matter in the universe. That approach is, of course, wrong since astrophysical processes can cause differences in local concentration of one type of matter versus another.

    So, you did the calculation right: start from an observed local density.
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