Here's a question that was asked of me today that I had absolutely no idea how to answer....


Assuming one could produce stable, non-interacting particles of Anti-Uranium.... what effect would the anti-radiation have on you? Or is radiation its own anti, like Photons?

Radiation isn't homogeneous. It's mainly alpha particles (helium nuclei), beta particles (electrons), neutrons, gamma rays (high energy photons), and neutrinos. Anti-uranium would produce anti-matter versions of this. You'd take far more damage from the anti-matter hitting you than you would from the radiation from a like amount of normal uranium.

Uranium can decay by alpha emission or spontaneous fission. Smack it with a slow neutron, and you get two smaller (and probably unstable) nuclei, gammas, neutrinos, and some more neutrons. Reverse the sign on everything if it's anti-uranium and an anti-neutron.

Fred

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To sum up, if I understand correctly that is... antiradiation isn't the issue, because the antimatter that carries the radiation would be far more dangerous than the antiradiation itself.

There wouldn't be a way for regular matter to carry antiradiation, because I'm a moron and couldn't put 2 and 2 together.

Just a small clarification: You would reverse the sign on everything except the photons.

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The Leif Ericson Cruiser

I'm not sure what you mean by "antimatter that carries the radiation." Break up an anti-uranium nucleus, and it's going to throw off antimatter fragments, gammas, and neutrinos. Now, true, pound for pound, anti-uranium 235 is going to be more hazardous than regular uranium 235, but either one could ruin your day.

Not quite true - there are ways for "regular" matter to produce antiparticles. For instance:

http://en.wikipedia.org/wiki/Positron_emission

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The Leif Ericson Cruiser

Is everybody overlooking the fact that an anti-uranium atom is surrounded by positrons, which will quickly react with the electrons of the surrounding medium, leaving a bare anti-uranium nucleus!

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T. Anderson

Yes, but say you found this hunk of anti-uranium adrift in outer space. Surrounding it would be slightly more pure vacuum from the interactions with it and the interplanetary medium.All spectrographic tests show it to be uranium. You reach out and grab it with your canadarm-type astrocrane when. . .

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This is somewhat along the lines of the conversation I was having...

It was very, very loosely based on science.

I'm sure everyone has had one of those "what if..." conversations with friends!

A clue to watch out for in interstellar hunks of uranium would be that it might have a pitted, spongy look from long term bombardment with positive atoms. Also, would you, if you scanned it long enough, pick up occasional anomalous readings as an atom of the interstellar medium annihilate itself with a uranium atom? Would that be visible?

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Doesn't Antimatter and matter anihilation result in Gamma Radiation?

The anomalous 511 keV gamma from positron annihilation would stand out like a sore thumb. The even higher energy gamma would be common from interstellar medium interactions also.

Larry Niven wrote a short story called Flatlander where they come across this sort of thing.

It was a whole planet, though, iirc. I love Niven's stuff, but one thing that bothered me about stories like this one and the one about flying around a neutron star is that it seemed like folks form the future seemed to forget a lot of basic science that was available to us now.

Nick

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Nick Theodorakis

Some of that was that no one knew it, part of it was that a science writer may not know enough to know it was missing.

Actually, Niven has written that he did get the neutron star story wrong.

Since photons are their own antiparticle, the EM of whatever energy would interact with you in any event.

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So what would the explosive yield be of a critical mass of uranium combining with the same mass anti-uranium?

E=mc^2

just like any antimatter bomb.