An Expanding World: Enlarging the dominion of human senses
How big is the arena of your awareness? In the 17th century, the human understanding of Nature was enlarged by the development of optical instruments. At the beginning of the century Galileo (1564 – 1642) caught wind of a Dutch invention whereby two lenses working together could bring distant objects into closer view. Quickly he developed his own telescope and turned it toward the heavens.(1) He published his astonishing observations in The Starry Messenger, 1610. The Moon was not a smooth sphere, as had been believed since classical times, but was covered in mountains that cast shadows.
Jupiter, the bright planet, had four moons of its own that circulated around it, like a small version of the solar system that Copernicus had proposed in 1543. In the light of this observation, Galileo became a vigorous advocate of the Copernican view that put the Earth and the other planets in orbit around the Sun. Unfortunately, that got him into trouble with the church authorities for speaking out of turn.
However, Galileo also looked at the Milky Way, normally visible to the unaided eye on a clear night as a cloud-like smudge that stretches across the sky. Through the telescope it could be seen as a mass of stars, many more than had ever been suspected previously. The known universe grew bigger, though it was a matter for conjecture whether the stars were all at the same distance away or studded inside a huge sphere.
One reasonable objection to the Copernican system had been that if the Earth moved in orbit around the Sun, surely the measured direction of a particular star would vary through the course of a year (a phenomenon known as parallax). Astronomers at the time could not detect it. Copernicus offered what probably seemed a lame excuse that the stars were just too far away for the effect to be apparent. He happened to be right, but it was not until 1838 that Bessell had access to instruments refined enough to measure the minute angles involved.
While the 17th century astronomers were exploring outer space, other people chose to create microscopes that enabled them to gaze into Nature’s finer details. In England, following the accession of Charles II in 1660, a group of ‘natural philosophers’ launched the Royal Society to promote experimental knowledge. They charged one of their number, Robert Hooke (1635–1703), to provide practical demonstrations at their regular meetings in London, a practice at which he was particularly adept. To this end he brought his observations with newly constructed microscopes. He revealed an exciting world and in 1665 the Society sponsored the publication of Hooke’s Micrographia,(2) which became a best seller, not least on account of the fine illustrations made possible by engraving on copper plates.
The book has lost none of its appeal, because it brims with the excitement of his discoveries. In his day fleas were a common pest, but Hooke found them worthy of admiration both for their prodigious ability to leap and for their beauty:
He is similarly enthusiastic about the louse, which he describes in almost heroic terms:
In paying attention to such creatures, Hooke not only extended the range of the physically observable but enlarged human sensibility. These common ‘pests’ exhibited structures that deserved respect for their ingenuity.
In the final section of his book, Hooke also describes how he had turned his attention towards the night sky, making use of a thirty-foot telescope with a three-inch object glass. This had revealed “multitudes of small stars”.
‘So that ‘tis not unlikely, but that the meliorating of telescopes will afford as great a variety of new Discoveries in the Heavens, as better microscopes would among small terrestrial Bodies, and both would give us infinite cause, more and more to admire omnipotence of the Creator.’
Hooke was not alone in studying ‘Bodies’ at close quarters. In the Netherlands the distinguished physicist and diplomat Christiaan Huygens (1629–1693) had already made a practice of carrying a lens in his pocket with which to examine ‘a new theatre of nature’. His young compatriot Anton van Leeuwenhoek (1632 – 1723) visited England in 1662, where it is possible that he saw a copy of the Micrographia or at least heard tell of it. Whatever the case, he set about his own microscopic studies using just mounted single lenses. His findings proved remarkable for what he revealed over many years, such as protozoa in rainwater, and bacteria in the tartar picked out from between his teeth. When Huygens learned of this activity in 1673, he wrote a letter to Hooke drawing it to his attention. Unfortunately, this was the time of the Anglo/Dutch war, and Hooke, who had an awkward temperament anyway, failed to answer.(3) Nevertheless, Leeuwenhoek began sending letters to the Secretary of the Royal Society in London about his discoveries. In all he sent over a hundred, which enlarged even further the world described by Hooke.
In the second half of the 17th century, the outstanding scientist was Isaac Newton (1642–1727). Not only a superb mathematician, he also had a talent for practical experimentation. Interested in astronomy, he devised a reflecting telescope to overcome the limitations of the glass lenses then available. This provided sharper images for the observer. But he is famous for his train of thought which stemmed from seeing an apple fall in his garden. It was drawn the Earth by gravity. That being so, he reflected how far did the force of gravity extend? Did it have an effect on the Moon, or through the space beyond? Such questioning led him to develop his theory of universal gravitation, published in Principia Mathematica 1687. It was a theory that embraced the stars.
Subsequently Newton published a treatise on optics in 1704.(4) It included details of his experiments showing that sunlight, by means of a prism, could be split into a spectrum of colours, yet another enlargement of awareness.
As Hooke forecast, improved microscopes continue to reveal ever more detailed minute structures in matter, and telescopes detect events far away in space and close to the beginning of time. We humans find ourselves positioned between the extremes of the incredibly small and the immensely vast. Rather than regarding ourselves as mere specks in the universe, I suggest that we enjoy a special privilege. While not knowing whether beings on some other planet can do the same, evolution has brought us to the point where through our agency the universe becomes aware of itself. We are not gods, but we do exercise a power that could be unique. How remarkable! AQ
(1) The wonderful Museo Galileo in Florence, which is devoted to the history of science, displays two of Galileo’s telescopes, together with the bones of his little finger!
(2) In 1961 Dover Publications of New York produced a facsimile edition of Micrographia with a modern preface by RT Gunther, but there is now a range of recent versions available. Also it can be viewed on line at www.royalsociety.org or as a free Ebook at www.gutenberg.org.
(3) The text of Huygens’ letter to Hooke may be found in Lisa Jardine, The Curious Life of Robert Hooke, Harper Collins, London, 2003, pp. 360-361.
(4) An Ebook edition is available from Barnes and Noble.