[HN Gopher] Oldest Material on Earth Discovered ___________________________________________________________________ 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." ___________________________________________________________________ (page generated 2020-01-19 23:00 UTC)