Magnetism and Its Humours

Over on brotherguy's blog, he mentioned a transoceanic interview where the journalist heard a word different from the one Guy thought he'd pronounced:

when the author refers to my work measuring "meteorites and their physical properties, including density and magnetic ferocity..."

There are so many oddly-named properties associated with magnetism that the existence of "ferocity" would not surprise me.

Reluctance. Flux. Permeance. Intrinsic moment. Inductive reactance.^* Hysteresis. Barkhausen jumps. And what my Finnish E&M professor kept referring to as "suskeptibility."

It all sounds like a medieval physician wrestling with a difficult diagnosis.




* Accompanied by the fabulous Frequency-Reactance Nomograph, which might make a nice pattern for a kilt.

(Promoted from brotherguy's comments section.)

Graham Nelson's Six Degrees of Neil Armstrong, 3 May 1998

You may be familiar with social-network "games," of which the best-known example seems to be Six Degrees of Kevin Bacon, though an older predecessor was the Erdős number of a mathematician.

Once upon a time, 3 May 1998 to be exact, Graham Nelson posted a wonderful article to Usenet's sci.space.history. He has given me permission to reproduce it here.

From: Graham Nelson 
Subject: Six Degrees, U.S. & Russian
Date: 1998/05/03

( We'll skip the rest of the header )

                  Six Degrees of Neil Armstrong
                  -----------------------------
            "I've danced with a man,
             Who's danced with a girl,
             Who's danced with the Prince of Wales..."
             (song lyric, quoting Herbert Farjeon (1887-1945))
                               -----
                              Contents

                  1. The Rules
                  2. Can the game always be won?
                  3. Distances and centrality
                  4. The Armstrong Number
                  5. Six Degrees of Orville Wright
         Appendix A. A One-Page History of Manned Spaceflight
                  B. Statistics to 3 May 1998
                  C. Proof of Main Theorem

                               -----
                           1. The Rules


In the game "Six degrees of Kevin Bacon", the player is given the
name of an actor -- Alec Guinness, say -- and challenged to think
of a series of films connecting him to Kevin Bacon, each connection
by a common cast member.

In the closely related game of "Six degrees of Neil Armstrong",
manned spaceflights replace films, those people aboard (henceforth
called "astronauts" regardless of nationality or employment status)
replace cast-members and Mr Neil Armstrong replaces Mr Kevin Bacon.
Calculating frivolous statistics replaces any more sensible
activity.

A "spacecraft" is any crewed vehicle launched with the intention
of reaching an altitude of 100 miles.  (Early X-program rocket
planes do not count.)  Crews from different craft are considered
merged into one crew only if they have crossed hatches into each
other's pressurised interior.  So although Gemini 6 and Gemini 7
approached within less than twelve inches, and the four astronauts
remarked on each other's beards as seen through the windows, they
were never one crew.  Similarly for the Shuttle's inspection-only
rendezvous with Mir.  Astronauts on their first launch are called
"rookies".
                               -----
                  2. Can the game always be won?


"Neil Armstrong to Alexei Leonov" is an example where the player
can win, by nominating:

      Alexei Leonov
      ~ Tom Stafford (Apollo/Soyuz)
      ~ John Young (Apollo 16)
      ~ Mike Collins (Gemini 10)
      ~ Neil Armstrong (Apollo 11)

which pleasingly joins the first man to walk in space, who then
drew a picture of it in the log-book with coloured pencils, with
the first to walk on the Moon, who was photographed only twice,
badly and by accident.  The notation ~ abbreviates "was once in
the same crew as".

But the player is certain to lose if challenged to join Yuri
Gagarin to Neil Armstrong, because Gagarin flew only once, and on
his own.  Gagarin is "related" to nobody: no astronaut can be
reached from him.


Main Theorem.  Every astronaut is related to every other, except:
    
   (i) The following are related to nobody at all:
          
       John Glenn (Mercury 6)       Yuri Gagarin (Vostok 1)
       Scott Carpenter (Mercury 7)  Gherman Titov (Vostok 2)
                                    Valentina Tereshkova (Vostok 6)
                                    Georgii Beregovoi (Soyuz 3)

  (ii) Two pioneers are related only to subsequent rookie crews:
  
       Al Shepard (Mercury 3) ~ Stu Roosa ~ Ed Mitchell (Apollo 14).
       Pavel Popovich (Vostok 4) ~ Yuri Artyukhin (Soyuz 14).

 (iii) Four rookie crews are related only to themselves:

       Vladimir Komarov ~ Konstantin Feoktistov ~ Boris Yegorov
       (Voskhod 1).
       Gerald Carr ~ Ed Gibson ~ Bill Pogue (Skylab 4).
       Gennady Sarafanov ~ Lev Demin (Soyuz 15).
       Vyacheslav Zudov ~ Valery Rozdestvensky (Soyuz 23).

Notes.
    (i) In a few months' time, John Glenn will fly on STS-95
    and cease to be an exception, leaving Scott Carpenter the
    sole American astronaut never to have flown with any other.

  (iii) Feoktistov and Yegorov were civilians sent up an an
    experiment: one was an engineer, the other a doctor and
    neither was very fully trained.  Komarov would have had a
    career in cosmonautics had he not been tragically killed in
    the re-entry of Soyuz 1, of which he was the sole crewman.
    Although Ed Gibson did not fly again, he did become head
    of NASA's scientist-astronauts in the early 1980s.


It follows that of the 383 astronauts to date, all but 21 can
be joined to Neil Armstrong by an astute enough player.

( Much more follows... )

( Appendices )

Mr. Nelson's excellent analysis engendered some comment threads, here (responding to an earlier version considering U.S. astronauts only) and here.