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Why do we associate nuclear radiation with a green glow? (kbin.social)

submitted 2 years ago by VoxAdActa@kbin.social to c/askscience@kbin.social

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So I just saw the YouTube video someone posted that showed nuclear reactors starting up, and the first thing I noticed was that they all glowed a very bright, pretty blue. I'm probably an idiot, but I was honestly expecting green, because of many years of dramatized depictions in popular media.

These are probably dumb questions, but:

Why is it blue? As in, what's actually glowing in there, and why do we see it that way?

and

Why do all the movies and comic books and video games go with green instead? Where did that come from?

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[–] pacology@lemmy.world 29 points 2 years ago (10 children)

The blue hue is called Cherenkov radiation. It happens when a particle moves through a medium early fast, leading to light being released. It’s like a sonic boom but for light.

As for the green glow, maybe it’s due to uranium glass glowing green unused UV light.

[–] vegivamp 22 points 2 years ago (6 children)

Really fast

Well that's the understatement of the week 🙂

When a photon (a light particle) enters a medium, it's speed drops somewhat. Lightspeed-the-universal-constant, however, is unchanged; so at that point it becomes possible for another particle in that medium to go faster than light.

When that happens, you get Cherenkov radiation.

"Really fast" indeed 😁 (i assume you know this, but I found it worthwhile to add a little clarification that it's not formula-1-really-fast)

[–] Peruvian_Skies@kbin.social 5 points 2 years ago* (last edited 2 years ago) (3 children)

Not really "faster than light", but faster than light in that medium. The phrase "faster than light" normally refers to moving faster than c, which particles ~~with rest mass~~ can't really do according to our current models.