Transcript James Gregory - Canisius College

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A new view of the Universe V
Fred Watson, AAO
April 2005
James Gregory
Born Nov. 1638, Drumoak Manse (near Aberdeen)
Fit like
Aberdeen
the day?
James Gregory
Education…
Around 1653, James entered Marischal College,
Aberdeen
Founded 1593, rebuilt c.1750
United with King’s College
in 1860…
James Gregory
While at Aberdeen…
James studied the science of optics and new
ways of making telescopes:
‘Moved by a certain youthful ardour… I have
girded myself with these optical speculations,
chief among which is the demonstration of
the telescope.’
(preface to Optica Promota, 1663)
James Gregory
London, c. Nov 1662–Feb 1663…
James travelled to London to
oversee the publication of
Optica Promota.
He made a brave attempt to
build the first reflecting (mirror)
telescope—of which more later.
But he was anxious to be off to
Paris to meet the great Dutch
mathematician, Christiaan
Huygens, and left it unfinished.
James Gregory
Italy, c. May 1663–May 1668…
James missed
Huygens in Paris
and had to be
content to leave a
copy of Optica
Promota for him.
He then went on to
his main destination,
the University of
Padua.
James Gregory
Padua…
James Gregory
While in Padua…
James studied under the Professor of Mathematics,
Stefano degli Angeli (himself a former pupil of
Torricelli and Cavalieri) until May 1667.
His own mathematical studies took on a new and
original dimension, and he independently laid the
foundations of the calculus (which is usually
attributed to Newton and Leibniz).
He published two books of great brilliance: Vera
circuli (1667) and Geometriae pars universalis (1668).
James Gregory
Back to London…
Gregory returned to London in
May 1668 to find that Vera circuli
had been well-received.
He was fêted by the scientific
community because of his up-toGosh, itofwas
date knowledge
Italian science.
James wasnothing,
elected a Fellow of the
really
Royal Society
on 11 June 1668.
James Gregory
Royal intervention…?
King Charles II seems to have been persuaded by
James’ fellow countryman (and fellow member of the
Royal Society), Sir Robert Moray, to found the Regius
Chair of Mathematics at the University of St. Andrews.
James Gregory
Off to St Andrews…
James arrived at St. Andrews late in 1668.
James Gregory
Gregory at St. Andrews…
James in the Upper Library with his clock
(by Joseph Knibb, 1673.)
James Gregory
Observing the stars…
James Gregory
Gregory and the diffraction grating…
James was intrigued by the behaviour of light as it
passed through the feather of a sea-bird.
He had demonstrated the
first diffraction grating.
James Gregory
BUT…
In this, as in all his work,
James deferred to his
younger contemporary,
Isaac Newton (1642--1727).
I would gladly hear Mr
Newton’s thoughts of it.
And that was his main
problem.
James Gregory
Attitudes at St. Andrews…
James was disappointed with the support he
received at St. Andrews:
‘I am often troubled with great impertinences…’
‘I was ashamed to answer, the affairs of the
Observatory of St. Andrews were in such a bad
condition, the reason of which was, a prejudice
the masters of the University did take at the
mathematics…’
So he left.
James Gregory
…And, in 1674, went to Edinburgh
In October 1675,
James was observing
the moons of Jupiter
with his students.
He suffered a stroke,
and went blind.
A few days later, he
died. He was 36.
James Gregory
A modern assessment of Gregory…
He was ‘…the only one of Newton’s
contemporaries who could match him in
mathematical breadth and profundity’.
But…
‘For all his talent and promise of future
achievement, Gregory did not live long
enough to make the major discovery that
would have gained him popular fame.’
(D.T. Whiteside, 1969.)
James Gregory
James Gregory
The origins of the telescope…
James Gregory
Lens telescopes in the 1660s…
James Gregory
There had to be a better way…
In contrast, mirror
telescopes developed
entirely in the heads of
the mathematicians of
the day.
Most notable were
Réné Descartes (1596-1650) and Marin
Mersenne (1588--1648)
James Gregory
Gregory suggested combining mirrors and
lenses…
The problem was that
no-one could make a
mirror good enough for
a telescope.
The reason why is due to basic optics…
James Gregory
Niccoló Zucchi had attempted to make a reflecting
telescope back in 1616
Concave mirror
Parallel light
from distant
object
Concave
eyepiece lens
Eye sees
upright
back-tofront image
It didn’t work.
Why not…?
Air
Glass
It’s 6 times harder to make an accurate mirror surface
than a lens surface.
(Prove it with the bathtub test…)
In 1668, Newton won the day…
Despite Gregory’s efforts in
1662 with the optician Richard
Reeve, he didn’t quite make
his telescope work.
Gregory had thought it
‘not worth the pains to
trouble myself anie
further with it’,
and headed off to Paris.
James Gregory
But eventually, Gregory prevailed…
Appropriately, it was
the Edinburgh optician,
James Short (1710-1768) who eventually
perfected the Gregorian
telescope.
And, in passing,
made his fortune.
James Gregory
And, of course, the rest is history…