Longest Running Thread EVER

[aylwin13]

Unless you're speaking to someone who doesn't know.

[Cancer]

I need an energetic proton source to spall pieces off the nuclei so I can transmute lead into gold.

[L. Marcus]

You brute.

[Pariah]

I'm pretty sure it's easier (and cheaper!) just to find gold.

[L. Marcus]

But is it as fun?

[Pariah]

Depends on where you look. (And with whom.)

[Bazza]

There's an asteroid zipping along out there called 391257 Wilwheaton. Wil Wheaton is the actor who brought Ensign Wesley Crusher to life on "Star Trek: The Next Generation." The announcement showed up on Twitter Wednesday from NASA's Ron Baalke, who describes himself as a "space explorer at the Jet Propulsion Laboratory."

[Bazza]

Astrology is a science: Bombay HC
http://timesofindia.indiatimes.com/india/Astrology-is-a-science-Bombay-HC/articleshow/7418795.cms

[Old Man]

[L. Marcus]

Astrologynomy, perhaps. But that would sort under the Humanities.

[Cancer]

Astrology is a science: Bombay HC

http://timesofindia.indiatimes.com/india/Astrology-is-a-science-Bombay-HC/articleshow/7418795.cms

Considering the idiocy (or perhaps idolatry) reigning in this country, all thst does is supply the cold comfort of noting that imbeciles in very high government positions are not restricted to the US and North Korea.

[Cancer]

Putting this follow-up to the Great Books thread here, because this is a statement about me and my biased perspective more than the book.

 

Ted Gray's Elements ... I have two comments about.

 

I tend to think about the elements in two contexts. Neither have much, if anything, to do with chemistry.

 

One is their spectra: how their spectra appear in stellar atmospheres of about the Sun's temperature and cooler. Lots of them don't appear at all (the halogens and the inert gases other than helium, in general, don't make absorption lines in the visible part of the spectrum at those temperatures). The lanthanides do, though finding clean lines in a stellar spectrum is hard. The alkali metals have distinctive spectra and after potassium they are beastly hard to see. The representations of the elemental spectra in the book are arc spectra -- emission lines! -- and not very useful from my perspective.

 

The second is the elements' nuclear properties, or origins, or other miscellany. Lithium stands out here. So does europium (which is the only pure r-process element with spectral lines accessible in the visible). A few elements (calcium, zirconium, barium, etc.) have lots of isotopes because they have magic neutron numbers; a few have lots of isotopes because they have magic proton numbers (tin is the prime example here).

 

Technetium (which has no stable isotopes, something Gray mentions) is produced in stars, and is seen spectroscopically in some AGB stars, a fact that was the first proof that nuclear reactions occur in stellar interiors. Chlorine has two stable isotopes, of crucial importance because one (37Cl) has a larger-than-usual cross-section for absorbing a neutrino, which makes it convert to an unstable isotope of argon, a fact that allowed Ray Davis and John Bahcall to detect neutrinos from the solar interior back in the 1960s, and demonstrate that something was wrong with them (there were -- are -- too few for standard particle physics).

 

Speaking of argon, though it makes up about 1% of Earth's atmosphere, the stuff we have is a rare isotope in terms of what is found through the universe. Ours is argon-40, which is a radioactive decay product of potassium-40. Most of the argon in the universe is 36Ar or 38Ar, but (being inert chemically) little of those were trapped in the forming Earth at the beginning of the Solar System. The argon we have now was all potassium at the time of Earth's formation. Helium is largely the same way: all our helium is the result of alpha-decay of a number of different things in Earth's interior over the history of the planet.

 

Carbon's two stable isotopes (12C and 13C) get shuffled in the CNO cycle, as do nitrogen's two stable isotopes (14N and 15N). The carbon isotopes can be measured fairly easily in stellar spectra using diatomic molecules (though the chemists will primly call them free radicals), CO, CH, CN. Oxygen's three stable isotopes get shuffled in some higher-temperature side branches of the CNO cycle; those can be measured in the CO vibration-rotation bands out at 2.2 or 4.5 microns. But the oxygen isotopes also show up in the visible if you have a good enough spectrometer: if you go to http://bass2000.obspm.fr/solar_spect.php and ask for 10 angstroms centered at 6871A wavelength, the lines there are all made by O ₂ in Earth's atmosphere. The strong ones are 16O+16O; the weak guys are 16O+17O or 16O+18O.

[L. Marcus]

:eyebrow: Fascinating.

[Pariah]

We just talked about the C-N-O cycle in last night's class. I'm sure I'd learned it once upon a time, but I remembered pretty much none of it. It was a fascinating discussion.

[Cancer]

You can look up a couple of papers by some bozo named Brown about where in the evolutionary sequence the CN-cycled material shows up at the surface.

[Pariah]

Sounds utterly fascinating!

[Cancer]

this

 

and

 

this

 

Those are abstracts, but the full papers are linked from there.

[L. Marcus]

Bozo Brown? Isn't that a college?

[Cancer]

Might be. Could be a pub, too.

[aylwin13]

Bozo Brown? Isn't that a college?

 

Isn't that the Secret Service's code-name for Trump?

[Old Man]

No, there are better code names.  "Twitler" and "Hair Furor" are my faves.

[Bazza]

Watching a documentary-drama about Ancient Egypt. Whatever your view on slavery; you have to admire they solved the unemployment problem -- gave everyone a government job.

[Pariah]

[L. Marcus]

The manual labourers that built the pyramids were peasants, not slaves.

[Old Man]

Glad to see today's slaves are buying the propaganda.