# Radioactive glow **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [December 6, 2012, 1:41am UTC](https://boards.straightdope.com/t/radioactive-glow/643144 "2012-12-06T01:41:40Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Mike\_Woodhouse](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@Mike\_Woodhouse](https://boards.straightdope.com/u/Mike_Woodhouse)\ **Post date:** [December 6, 2012, 1:41am UTC](https://boards.straightdope.com/t/radioactive-glow/643144/1 "2012-12-06T01:41:40Z")
Actinium glows blue without needing other phosphorescent materials around. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [December 6, 2012, 1:48am UTC](https://boards.straightdope.com/t/radioactive-glow/643144/2 "2012-12-06T01:48:53Z")
Are you referring to [this](http://www.straightdope.com/columns/read/1320/if-you-were-radioactive-would-you-glow)? If you are, the point that Cecil is making is that it’s the passage of the radiation that causes a glow; the material being passed through doesn’t need to be phosphorescent. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [December 6, 2012, 3:20am UTC](https://boards.straightdope.com/t/radioactive-glow/643144/3 "2012-12-06T03:20:45Z")
According to [Wikipedia](http://en.wikipedia.org/wiki/Actinium#Properties): > [@](#): > > Owing to its strong radioactivity, actinium glows in the dark with a pale blue light, which originates from the surrounding air ionized by the emitted energetic particles. I am not sure whether that makes Cecil right, or **Mike Woodhouse** right, maybe both of them. It does make me a bit suspicious of Cecil’s explanation of the glow of radium reported by Madame Curie, however. As I recall the story, she reported seeing a glow from what was, by then, fairly pure radium chloride, recrystallized from solution. That glow seems more likely to have been from ionized air than from remaining fluorescent mineral impurities, as Cecil claims. (Also, I am not entirely sure if this is one of the places where Wikipedia is to be trusted. The cite it gives does talk about a radioactive glow caused by air ionized by intense radioactivity, but it does not specifically mention actinium, and is probably a secondary or tertiary source, at best.) ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [December 6, 2012, 7:15pm UTC](https://boards.straightdope.com/t/radioactive-glow/643144/4 "2012-12-06T19:15:04Z")
Actinium doesn’t glow by itself if the air around it is what is glowing; put a piece in a vacuum and you’ll see no glow. ---
**Author:** ![bintang](https://avatars.discourse-cdn.com/v4/letter/b/8edcca/32.png) [@bintang](https://boards.straightdope.com/u/bintang)\ **Post date:** [December 6, 2012, 7:44pm UTC](https://boards.straightdope.com/t/radioactive-glow/643144/5 "2012-12-06T19:44:25Z")
Could it be that it does glow, just not within our visual spectrum? ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [December 6, 2012, 8:24pm UTC](https://boards.straightdope.com/t/radioactive-glow/643144/6 "2012-12-06T20:24:25Z")
> [@Michael63129](#): > > Actinium doesn’t glow by itself if the air around it is what is glowing; put a piece in a vacuum and you’ll see no glow. That was my point. > [@bintang](#): > > Could it be that it does glow, just not within our visual spectrum? No. Not directly as an aspect of its radioactivity, anyway. None of its isotopes produce gamma rays (which would indeed be electromagnetic radiation, like light, but outside of the region of the spectrum our eyes can detect). There will be infra-red heat radiation, but anything above absolute zero is going to give off some of that. I suppose, actinium will give off a bit more than most things around it, though, because it will be heated up by its own radioactivity. I suppose if it got hot enough (maybe a big enough lump could) it might visibly glow red hot. I don’t think that is the radioactive glow that people are talking about, though. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [December 6, 2012, 11:04pm UTC](https://boards.straightdope.com/t/radioactive-glow/643144/7 "2012-12-06T23:04:06Z")
Are there _any_ radioactive isotopes that give off visible light photons when they decay? ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [December 7, 2012, 12:06am UTC](https://boards.straightdope.com/t/radioactive-glow/643144/8 "2012-12-07T00:06:11Z")
> [@ZenBeam](#): > > Are there _any_ radioactive isotopes that give off visible light photons when they decay? I don’t think so. It is typically α, β, (both particulate) and γ (high energy photons, way beyond the visible spectrum). I think there may be a few exotic cases where other particles such as positrons are emitted, and there may be neutrinos, but not low energy photons. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [December 7, 2012, 4:22pm UTC](https://boards.straightdope.com/t/radioactive-glow/643144/9 "2012-12-07T16:22:52Z")
> [@ZenBeam](#): > > Are there _any_ radioactive isotopes that give off visible light photons when they decay? By direct emission of decay products, no. However, if you insulate a chunk of Plutonium-238 (or one of its compounds, notable PuO2), it builds up heat from decay and begins to glow visibly. From heat, not direct radiation emission, but it is [glowing](http://en.wikipedia.org/wiki/File:Radioisotope_thermoelectric_generator_plutonium_pellet.jpg) nonetheless. Cecil didn’t mention that, because it’s kind of cheating: it’s not specifically the radiation that’s causing the glow, it’s the heating. Heat up any chunk of metal to the same temperature and you’d get the same glow. It’s just that in this case, the heating is directly caused by the radiation (something about alpha particle emission within the material itself; I guess the particles smacking into adjacent molecules would heat the plutonium by kinetic energy absorption.) So, yes, some radioisotopes glow because they’re radioactive. But what you’re seeing in that case isn’t a direct emission of the decay process. So it doesn’t really count as “glowing” the way that pop culture depicts it. Pop culture was wrong. Who knew?