Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: radiometer paradox





On Mon, 16 Jun 1997, Bob Sciamanda wrote:

Bob Sciamanda wrote:
. . .
The first clue came when I put the radiometer in a microwave oven (!)
for a 1 second blast. The whole bulb glowed nicely with a nitrogen
discharge and . . .

Notice how a microwave oven can turn a Crookes radiometer into an
(electrodeless) Crookes discharge tube! Does anyone know for sure that
these are the same person - any anecdotes or references about the man?
--

Yes, it is the same person, Sir William Crookes (1832-1919). Crooks' field
was primarily spectroscopy. He was one of the discoverers of the element
Thallium, and also attained popular notice for his investigations of
spirit mediums and his endorsement of reality of the physical
manifestations during seances. Historian A. Rupert Hall thinks there's
good evidence his initial enthusiasm for spiritualism began when he had an
affair with one of the mediums. These spiritualism investigations brought
him criticism and ridicule, and some even speculated (without sufficient
evidence, I think) that his careless handling of Thallium had produced
brain damage and irrational behavior (his lucid writings late in life are
evidence to the contrary). It was Crookes who prepared Faraday's "Chemical
History of a Candle" for publication.

The Crookes radiometer was considered important then *as evidence for the
kinetic theory of gases*, for it was understood that the motion of the
vanes was due to air molecules in the partial vacuum of the tube. (If we
demonstrate the toy, we ought to get the historical importance of it
right.) The direct radiation pressure of light requires a *far more
sensitive* device to demonstrate, and that came much later. (Anyone know
who?)

Crookes' investigations of gas discharges led him to describe gases of
charged particles as a "fourth state of matter". We now call it the
"plasma state."

Crookes invented the spintharascope which used a zinc sulfide screen to
detect alpha particles.

Crookes noticed on several occasions that photographic plates were fogged
when near his operating Crookes, even though they were in light tight
sealed containers. He didn't make the connection, and on one occasions,
returned an batch of plates for refund as "defective". Thus he missed the
discovery of X-rays. He also was near to discovering isotopes, but didn't
take the final step, and Soddy is credited with that discovery.

Crookes was, in his day, as well known to the public as Feynman was more
recently. His work in physics was respected in the physics community. He
was knighted in 1897 and served as president of the Royal Society from
1913 to 1915.

Any of you who use Coletta's "College Physics" have seen the neat picture
on p. 427 of Tesla reading a newspaper while 25 foot long sparks dance
overhead. But have you gotten out a magnifier to read Tesla's note penned
at the bottom of the picture? It reads:

To my illustrious friend Sir William Crookes of whom I always think
and whose kind letters I never answer! June 17, 1901 Nikola Tesla.

There are many opportunities to inject real history of physics and present
physicists as "real people" without taking much extra class time. But the
teacher needs reliable science history resources to draw upon.

-- Donald

......................................................................
Dr. Donald E. Simanek Office: 717-893-2079
Prof. of Physics Internet: dsimanek@eagle.lhup.edu
Lock Haven University, Lock Haven, PA. 17745 CIS: 73147,2166
Home page: http://www.lhup.edu/~dsimanek FAX: 717-893-2047
......................................................................