[HN Gopher] Oldest Material on Earth Discovered
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       Oldest Material on Earth Discovered
        
       Author : Hooke
       Score  : 34 points
       Date   : 2020-01-19 06:33 UTC (16 hours ago)
        
 (HTM) web link (www.bbc.com)
 (TXT) w3m dump (www.bbc.com)
        
       | yborg wrote:
       | What I found to be the most interesting observation is that the
       | majority of the grains found have an age very close to the
       | assumed age of the Sun itself. This kind of implies that the the
       | cloud that the Solar System formed from was mostly seeded by the
       | event that began cloud collapse.
        
       | ur-whale wrote:
       | Not a hint of the chemical composition in the article, or did I
       | miss it?
        
       | leeoniya wrote:
       | > "I compare this with putting out a bucket in a rainstorm.
       | Assuming the rainfall is constant, the amount of water that
       | accumulates in the bucket tells you how long it was exposed,"
       | said Dr Heck.
       | 
       | does this imply that cosmic rays have been constant for half the
       | age of the universe? or at least have a predictable decay rate?
       | or is this just a weak analogy?
        
         | cobbzilla wrote:
         | I wondered this as well.
         | 
         | Also, even if the rate of cosmic rays has been constant, would
         | it make sense that the impact of said rays on any body would be
         | perfectly uniform? Wouldn't it follow a normal/gaussian
         | distribution, such that some parts of the meteorite received a
         | bit more cosmic rays, and some a bit less? Do the "ages" they
         | found follow such a distribution?
        
           | sandworm101 wrote:
           | >> such that some parts of the meteorite received a bit more
           | cosmic rays, and some a bit less?
           | 
           | Everything in space spins, from the smallest speck of dust to
           | entire galaxies. Put a stationary object in space, in light,
           | and that light will start it spinning. So we would expect
           | cosmic rays to be uniform across the surface.
        
             | BurningFrog wrote:
             | True, though they spin around one fixed axis.
             | 
             | So if there is a big radiation source due "north", there
             | should be less radiation received on the "south" side.
        
             | cobbzilla wrote:
             | Thank you, I hadn't considered a spinning effect to achieve
             | uniformity, nor that the presence of light could induce
             | spin. Good food for thought.
        
         | pacala wrote:
         | The rainfall over very long periods of time is not constant.
         | From boring relative position to the nearby star, to the
         | activity of said star, to more exotic
         | https://en.wikipedia.org/wiki/Gamma-ray_burst and God knows
         | what else.
         | 
         | A more honest statement: "We measured Ne-21 in meteorite
         | minerals in higher concentration than on similar Earth
         | minerals. We think it's caused by cosmic rays. We have no clue
         | where the cosmic rays came from or when."
        
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       (page generated 2020-01-19 23:00 UTC)