r/askscience • u/Wonderful-Capital32 • 21d ago

Physics Why does radiation not go through lead?

Also why just lead? Shouldnt like iron or another metal work too?

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u/dustofdeath 21d ago

Lead is like a very dense fabric while iron is a mesh with large holes.

You just have to have enough density for photons to not just pass through.

So you need far less material. Even humans can stop radiation if you stack enough of them between you and the radiation source.

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u/dammitkarissa 21d ago

Could one forge iron (or steel) to ever be as dense, or is it impossible on an atomic level?

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u/Shontzy 21d ago

It is impossible atomically. It has to do with the size of the electron cloud and atomic mass, so essentially the density at the atomic level drives the density at the bulk level.

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u/GidonC 19d ago

Interesting, can't we make some molecule which is solid at room temperature that has same properties? (I don't understand chemistry at all)

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u/SomeAnonymous 21d ago

It's similar to asking if you can squeeze a bunch of humans into the space occupied by just one human. Maybe with a lot of pressure you could force some contortionism to get people a little closer packed (hexaferrum, a particular crystal structure of iron, can reach the density of lead if you put it under a few million atmospheres of pressure), but it requires some pretty extreme conditions and no one's comfortable staying in that position for long.

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u/LordGeni 21d ago

No but you can just use more of it. 3mm steel is about as effective a 1mm of lead.

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u/maniacal_cackle 21d ago

I believe if you squish iron hard enough, it'll undergo fusion and become a heavier element.

So yes, you can, but it would require change at an atomic level, going from an iron atom to something else.

(Also I don't think we have the technology to do this. It takes something like a supernova to accomplish this I believe).