Currently I’m reading Richard Holmes’ excellent Age of Wonder. In his book, he chronicles the lives of gentleman scientists and ambitious amateurs of the Romantic generation. These people defy classification: they could be both botanists and explorers, astronomers and inventors, poets and scientists. What they shared was an unquestionable love and wonder for nature. The age of Enlightenment had provided the tools for ‘Natural Historians’ to systematically study the world in which they lived. The Romantics used these tools for exploring nature’s secrets and beauty.
One of these individuals was William Herschel (1738 – 1822). Herschel was a gifted and talented musician. Traveling from town to town between musical performances, he became captivated by the stars above him. He went on to become a self-taught astronomer. Holmes suggests that his musical talents might have aided Herschel in reading the stars, as if they were musical notes part of a larger musical score. Herschel built his own telescopes, which would eventually become far superior to any telescope of his time. In 1781 he was catapulted to fame, after he discovered the planet Uranus and cataloged numerous nebulae.
However, to me these are not his greatest achievements. In his early paper ‘On the Construction of Heavens’ (1786), he displays a remarkable insight into our universe. He hypothesizes that nebulae are distant star clusters, forming other galaxies (or in his words: ‘island universes’), at different distances to the earth. With this hypothesis, Herschel introduced the concept of ‘deep space’ into astronomy. Even more interesting, Herschel thought that the different size and structure of galaxies were indicative for their age. Different galaxies were in different stages of stellar evolution!
Galaxy NGC 4522 is travelling at 10 million kilometers per hour. Star forming regions are left and right, in blue.
Consider the shock this must have been for Herschel’s contemporaries! Since the first Babylonian astronomers looked up towards the stars, the universe had been considered static. The firmament had always been fixed and the movement of heavenly bodies could be predicted with great precision. Things were ordered, things were good.
But what Herschel discovered, is that our universe is dynamic. Stars can be born, galaxies may decay. The starlight that reaches us now comes from stars that may no longer exist. Our galaxy has a beginning and it will have an end. The universe is not only enormously big (deep space), the time scales by which stellar processes occur are enormous as well (deep time). The philosphical implications of this discovery were profound. The way Herschel practiced astronomy revolutionized the entire field.
Erasmus Darwin, the grandfather of Charles Darwin, wrote a passage describing Herschel’s discovery in his poem The Botanic Garden:
So, late descried by Herschel’s piercing sight,
Hang the bright squadrons of the twinkling night;
[...]
Flowers of the sky! ye too to age must yield ,
Frail as your silken sisters of the field!
Star after star from heaven’s high arc shall rush,
Suns sink on suns, and systems systems crush,
Headlong, extinct, to one dark centre fall,
And death and night and chaos mingle all!
A fusion between poetry and science. The stars have become flowers, things of passing beauty.
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