Oldest Material on Earth Discovered | Hacker News Reader

Oldest Material on Earth Discovered

bbc.com

49 pointsHooke10 comments

> "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?

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?

>> 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.

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.

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.

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."

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.

How do they know that the material they discovered is the "oldest material on earth"?

Not a hint of the chemical composition in the article, or did I miss it?

How much neon is there? If there is too much new element formation I'm not sure what the chemical composition would mean.

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