Basically, all legal free speech is allowed. We will assist the authorities in dealing with illegal speech. You are each other’s moderators. Have fun. And don’t forget to MAGA at nuclear levels.
Citizen U
Day 63 – EUROPIUM.
OPEN THREAD 20200108
Published
The U Tree 
If anyone has been noticing a gradual deterioration in my mental state, along with odd shifts in my hours of activity, the Qtree KAGA thread has an explanation. And, BTW, that’s probably why I’m a bit headache-y and whiz ten times a day.
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Hope you feel better coothie.
I enjoy your posts… Very educational!
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Europium is another lanthanide rare earth. It’s about as common in the earth’s crust as tin.
(Woke up with this on my screen from last night.)
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OK, let’s get moving….
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Europium is the least dense of the lanthanides, and has the second-lowest melting point. It is also the most reactive of the rare earths, “rusting” in air so fast that it is almost impossible to see it as a metal. It’s special magic is (no surprise) optical — it is used as a phosphor in various sorts of light production, and can be used to dope lasers.
Interestingly, the word “fluorescence” is somewhat derived from europium, though they didn’t know it at the time…..the phenomenon was named after fluorite (CaF2) deposits near the city of Weardale in northern England in 1852….well before Europium was isolated in 1901. Only after europium was “outed” was it realized that the fluorite found there was fluorescent because it was naturally doped with europium.
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As an aside, coming up with the “as common in the earth’s crust” things is non-trivial. Wikipedia helpfully provides five different estimates at https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust .
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A newlywed husband is discouraged by his wife’s obsession with mathematics. Afraid of being second fiddle to her profession, he finally confronts her: “Do you love math more than me?”
“Of course not, dear – I love you much more!”
Happy, although sceptical, he challenges her: “Well, then prove it!”
Pondering a bit, she responds: “Ok… Let epsilon be greater than zero…”
(My parents met in the undergraduate math program at CSULB, have five STEM degrees between the two of them, and mom was a professor of mathematics.)
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To show you how STEM-corrupted I am, I read this and thought “I don’t get it. Where’s the punch line? The post must be cut off – there’s nothing inherently funny about epsilon or starting a proof in this manner.
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