The Omnipotence of the Creator: Robert Hooke, Astronomer

Part of the Science Networks. Historical Studies book series (SNHS, volume 39)


Even though Hooke was probably England’s most important astronomer between Galileo’s contemporary Thomas Harriot and the first Astronomer Royal John Flamsteed, his role in astronomy is not generally recognized.1) His activities as an astronomer and astronomical instrument maker were uniquely diverse by comparison with those of his contemporaries, both because he was a somewhat sporadic observational astronomer who made discoveries with the telescope and discoursed on them to the Royal Society, but also because he was also a recognized authority on optics, an adept designer of and fabricator of astronomical optics, and an original designer of mountings for quadrants, telescopes, and other instruments. The Journal Book is full of accounts of Hooke’s designs of grinding machines for lenses and mirrors, and his mechanical designs are displayed for all to see in his published Cutler Lectures.2) This represented a convergence of his talents as an optician and instrument maker with his other interests in natural philosophy, notably light and color on the one hand, and planetary motion on the other.


Seventeenth Century Planetary Motion Lunar Eclipse Astronomical Timing Binary Star System 
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  1. 1).
    Some exceptions are Nagajima (2001; 2006) and Allan Chapman, “Robert Hooke’s Telescopic Observations of Solar System Bodies,” Hooke 2003 Symposium. Also Chapman’s England’s Leonardo (2005).Google Scholar
  2. 2).
    “An Attempt to Prove the Motion of the Earth Through Observations” (1674), “Animadversions on the First Part of Hevelius’ Machina Coelestis” (1674), and “Helioscopes” (1676).Google Scholar
  3. 3).
    Henry Powers, 1664: “Of all the Inventions, none there is Surpasses the Noble Florentine’s Dioptrick Glasses. For what a better, finer gift could bee in this world’s aged Luciosity; To help our Blindness so as to devize a paire of new and Artificial eyes, By whose augmenting power we now see more than all the world has ever known before.”Google Scholar
  4. 8).
    In Micrographia, p. 242.Google Scholar
  5. 9).
    See Wright (2000), for example. Reeves appears several times in Pepys’ Diary. Huygens took advantage of the opportunity to visit Reeves shop when he visited London in 1661 (and also skipped the coronation of Charles II on 23 April 1661 in order to observe the transit of Mercury). See also Nicholson (1965).Google Scholar
  6. 11).
    Simpson (1992), pp. 84–88.Google Scholar
  7. 12).
    Birch , III, p. 122. Birch records that “Mr. Hooke produced a new kind of reflecting telescope of his own contrivance ... This was performed in a way propounded by Mersennus, and repeated in Mr. [James] Gregory’s Optics; but was thought to hve been never actually done before.” Richard Reeves, London’s most accomplished optician, attempted to build a Gregorian telescope. The main difficulty seems to have been that of polishing a speculum metal mirror, but the issue of non-spherical surfaces was also a large one. Reeves also built Boyle’s 60-ft telescope, which was intended for Hooke’s use, and worked with Wren and Hooke on their compound microscopes. Gregory described his telescope in his Optica promota of 1663. Whiteside described Gregory as “the only one of Newton’s British contemporaries who could match him in mathematical breadth and profundity.” (Whiteside, 1967–80, p. xiii) See Simpson (1989, 1992).Google Scholar
  8. 13).
    Gunther , VI, p. 358.Google Scholar
  9. 14).
    Flamsteed to Collins, 1 December 1670. Gunther, VI, p. 370–1.Google Scholar
  10. 15).
    Micrographia, p. 241–2. The effect of aperture on limiting magnitude is clearly described as well.Google Scholar
  11. 16).
    Allan Mills, John Hennessey, and Stephen Watson have given a detailed analysis of Hooke’s design, including the worm and gear driven backwards. See “Hooke’s design for a driven equatorial mounting,” Mills, et al. (2006). Hevelius was not a stranger to telescopes, himself.Google Scholar
  12. 22).
    Micrographia, p. 245.Google Scholar
  13. 24).
    PT, 1, 3 (1666). Hooke recounted that the spot moved half of Jupiter’s diameter, “east to west,” in two hours, implying a period of rotation of perhaps 8–10 hours, though he seems not to have derived a number. This account, of an observation made 9 May 1664, followed a similar report by Campani, who also observed shadows of the satellites on the planet. Jupiter, of course, rotates west to east, so Hooke was in error, perhaps forgetting he was using an inverting telescope. Cassini arrived at a figure of 9h 56m, almost identical to the modern value, and published it in 1665. Cassini also discovered an “inequality” in the rotation of Jupiter of up to 16 minutes, related to the distance between Earth and Jupiter. The final step, that this was due to the finite speed of light, he was unwillign or unable to take. See, for example, J.D. North, “The satellites of Jupiter from Galileo to Bradley,” in The Universal Frame, London, 1989. It was Rømer who took that step, in 1676 (I.B. Cohen, “Rømer and the First Determination of the Velocity of Light,” Isis 32 (1940) 327–79. Rømer’s discovery was published in the Philosophical Transactions in 1677, but Hooke, like Cassini, seems to have been unwilling to admit the finite speed of light.Google Scholar
  14. 26).
    Birch, I, p. 19.Google Scholar
  15. 28).
    “A late Observation about Saturn ...”, PT, 1, 14 (2 July 1666) 247.Google Scholar
  16. 34).
    Diary , 1 April, 1673 (11 April Gregorian).Google Scholar
  17. 38).
    Birch, 28 February, 1677/8. Hooke apparently understood that even a solid body could be distorted by its rotation. This idea is consistent with his discussions in Micrographia on how gravity determines the shapes of the planets and with his ideas on elasticity, expressed in his “De Potentia Restitutiva”, i.e., “Of Spring.” We touched on this issue in context in Chapter 7.Google Scholar
  18. 39).
    Diary , pp. 146 and 149. The lunar eclipse was on the night of 18–19 September.Google Scholar
  19. 42).
    For example, Diary , 22 and 29 April 1678.Google Scholar
  20. 44).
    Pepys, in his diary, noted that he had heard Hooke lecture at Gresham College on 1 March 1664/5, and that “Mr. Hooke read a curious Lecture about the late Comett ... proving very probably that this is the very same Comett that appeared before in the year 1618, and that in such a time probably it will appear again.” Pepys (1972), VI, p. 48. See also Chapter 7.Google Scholar
  21. 47).
    PW, p. 154.Google Scholar
  22. 48).
    PW, p. 150. Other parts delivered on 8 and 15 November. Hooke’s first observation of the Comet of 1682 was on 16 August, and he saw it on another 10 occasions up to 10 September, just before perihelion on 15 September.Google Scholar
  23. 51).
    The lecture had been read four years earlier. As we have said, this is really a quite wonderful work, which describes the astronomical issues involved, but also Hooke’s zenith telescope and how he mounted it in his rooms at Gresham College. See Gunther , Vol. VIII, pp. 1–28.Google Scholar
  24. 55).
    See especially Gunther , VIII, pp. 17–23.Google Scholar

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