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Comment by melloclello | Hacker News Reader

Doesn't the interstellar medium effectively turn into alpha radiation at significant percentages of the speed of light?

http://www.antipope.org/charlie/blog-static/2016/08/san-trom...

No, particles don't change their nature depending on their speed. Furthermore, you realize that speed is always relative to something (especially in open space, when there's no conventional reference system as it happens in day-to-day talking on Earth)? So, would you say that a particle can be a neutrino w.r.t. a galaxy and an alpha particle w.r.t. another remote galaxy?

Or that it can be an electron w.r.t. a star and a beta particle w.r.t. another? ;-)

> we have a technical term for an ionized helium nucleus travelling at roughly 2% of the speed of light—6000km/sec—we call it an alpha particle.

Technically, an helium nucleus is an alpha particle, independent of its speed.

Edit: an helium nucleus with two neutrons is an alpha particle. An helium nucleus can exist with just one neutron.

I thought that was a pretty choice line. Relax, I think we both know what Charlie actually means.

Yes, but Charlie got the math wrong. It's a lot less than he suggests.

See: https://news.ycombinator.com/item?id=12329322

In addition, if we are talking "gram sized" projectiles, they likely have a front cross sectional area on the order of 10^-4 m^2 or less. That means that we are talking about 16 milliCuries or so. That's about the amount of radiation in a single medical imaging dose, or as much alpha emission as 1000 smoke detectors.

This is what I was wondering. Thanks!

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