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?
I’m guessing the tragedy of the radium girls had something to do with the association.
https://timeline.com/radium-girls-kate-moore-2bc5746f9a6b
ETA: I’m not sure it’s actually mentioned in the article, but radium paint glows green.
I’m almost certain this is it.
Most people’s experience in the early days with “glowing radioactive stuff” would have been radium paint, which glows green.
Normal people wouldn’t have seen Cherenkov radiation (blue glow)
Edit: just to make it clear, stuff painted with radium paint was not uncommon decades ago
Source: I’m gettin kinda oldTritium glows bright green and is used in a lot of consumer products, specifically gun sights and watches. Uranium glass also glows bright green.
Maybe people think radioactive things glow green because… they often do glow green.
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.
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)
There’s a bit of miscommunication here.
Nothing travels faster than c, or the speed of light within a vacuum.
The speed of light within a medium (like water) is not c. It is less.
When a particle is traveling at c and slams into a medium like water with enough force it will continue traveling faster than light normally would in that medium, and give off that radiation as it does.
But it is not traveling faster than light as you emphasized. It is traveling at nearly c and getting slowed down. It is often referred to a “light based sonic boom” though because that makes sense. But only when you consider the transition from vacuum to a medium or medium to medium.
Protip: anytime someone points out a thing is traveling faster than light they’re wrong because really: nothing does ever. It isn’t physically possible and the smartest minds on the planet have tried to reason how it might be for nearly a century now, with no progress at all. There are workarounds but they don’t involve “travel” in the real sense, more like displacement.
I’m aware, and that was the point I was trying to make - but clearly ineffectively. Thank you for the extra clarifications.
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 masscan’t really do according to our current models.Which particles can’t really do according to our current models.
Particles without rest mass can only move at c, not faster than c.
(Sorry for the nitpick)
I stand nitpicked and corrected. :)
That was my point, but clearly not well formulated - thank you for clarifying.
They used to have radioactive decoder rings and other toys that glowed green in the dark. They also used to paint all sorts of things with radioactive paint to glow in the dark like instrument panels.
Interesting I just assumed they did that in cartoons like how you see a skeleton when someone gets electrocuted.
I just checked it out, and it looks cooler, than the green glow.
Artists need to change the nuclear glow in their work into blue.
Some possible factors, from reading similar discussions:
-
Tritium paint is radioactive and produces a pale green fluorescence on watches.
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The Simpsons had a glowing green fuel rod in the opening. The rod would not have glowed green in reality.
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Uranium glass fluoresces green under UV light
since 1) and 3) are things that maybe 10 people in the world even know about, it’s probably the Simpsons yeah
In 2023, yeah, but remember that it isn’t in 2023 that the association was made.
Tritium watches used to be a much bigger deal some decades back, as you could actually use the thing in the dark. Subsequent to that, battery-powered digital watches with a light became common, and then a lot of people just moved to using a cell phone to know the time.
As the linked WP article details, uranium glass also used to be more-common prior to the government locking up a lot of supplies of uranium. I’ve only seen uranium glass in person in museums, and in general, plastic has displaced a lot of glassware today.
Tritium is also still very popular for firearm night sights. And I’m sure some radium painted one used to be as well. The night sights on my SKS may have been radium paint or just regular phosporescent paint, or may have had tritium vials that fell off.
For a while there was a full set of uranium glassware in my local antique mall for sale but I think someone bought it.
I have a small tritium light source on each of my key chains. Extremely useful!
They come in various colors, even. I use blue for car keys, yellow for house keys, red for bike keys.
You really think only ten people in the world know about those? Maybe closer to one in ten.
-
I’m having a feeling it’s a combination of other stuff mentioned here like radium, which was then put on The Simpsons and then that’s what everyone got the idea from. They made nuclear waste a green liquid and that’s the cultural zeitgeist there, probably.
The blue glow, Cherenkov radiation, is something that happens underwater, though. It’s not really a drop-in replacement for, say, a puddle of radioactive waste.
I think that the problem is more that artists just want a way to indicate that something is radioactive, but we can’t see radioactivity, so they had to seize on some sort of convention that deviated from the real world. It doesn’t really need to reflect reality to work, just as long as the convention holds. And the practice of doing that in art isn’t that new, either – think of the halo, which serves a similar purpose:
https://en.wikipedia.org/wiki/Halo_%28religious_iconography%29
A halo (from Ancient Greek ἅλως (hálōs) ‘threshing floor, disk’; also called a nimbus, aureole, glory, or gloriole) is a crown of light rays, circle or disk of light that surrounds a person in art. It has been used in the iconography of many religions to indicate holy or sacred figures, and has at various periods also been used in images of rulers and heroes. In the religious art of Ancient Greece, Ancient Rome, Christianity, Hinduism, and Buddhism among other religions, sacred persons may be depicted with a halo in the form of a circular glow, or flames in Asian art, around the head or around the whole body—this last one is often called a mandorla. Halos may be shown as almost any colour or combination of colours, but are most often depicted as golden, yellow or white when representing light or red when representing flames.
