Introduction
As an astronomer, Thomas Wright was particularly struck by the sheer size of the universe, “the secret Depths of Infinity, and the wonderful hidden Truths of this vast Ocean of Beings”. He often found that others, though fascinated by the solar system, had no conception of the distances involved, so he came up with this homely illustration.
TO give you therefore a clearer idea of Distance, and impress the proportions of space more strongly and fully in your mind, let us suppose the body of the Sun, as I have said before, to be represented by the dome of St Paul’s;* in such proportion a spherical body eighteen inches diameter, moving at Mary-le-bone, will justly represent the Earth, and another of five inches diameter, describing a circle of forty-five feet and a half radius round it, will represent the orbit and globe of the Moon.
A body at the Tower* of 9,7 inches,* will represent Mercury; and one of 17,9 inches at St James’ palace will represent the Planet Venus; Mars may be supposed at a distance, like that of Kensington or Greenwich, 10 inches diameter.
* Wright worked with a figure of 145ft for the diameter of the dome of St Paul’s Cathedral, which is actually a little on the large side. His scaled figures for the various planets stand up well to modern measurements. He gives:
Saturn from the Sun, 27 Miles, and 1700 Yards.
Jupiter, 15 Miles, and 458 Yards.
Mars, 14 Miles, and 751 Yards.
the Earth, 2 Miles, and 1632 Yards.
Venus, 2 Miles, and 217 Yards.
Mercury, 1 Mile, and 267 Yards.
and of the Moon, from us, 45 Yards and a half.
* That is, the Tower of London.
* Wright uses a decimal comma instead of a decimal point, relatively unusual in England since John Napier used the period (full stop) as the decimal separator for his logarithm tables in 1614 and 1619, a convention adopted by Henry Briggs in Arithmetica Logarithmica (1624). The use of commas is more characteristic of the European Continent.
Précis
In 1750, Durham-born Thomas Wright attempted to make the vast distances involved in the science of astronomy more comprehensible to a popular audience. He took the dome of St Paul’s in London as representing the Sun, and on that scale calculated the relative positions and diameters of the planets of the solar system. Earth he placed at Marylebone. (58 / 60 words)
In 1750, Durham-born Thomas Wright attempted to make the vast distances involved in the science of astronomy more comprehensible to a popular audience. He took the dome of St Paul’s in London as representing the Sun, and on that scale calculated the relative positions and diameters of the planets of the solar system. Earth he placed at Marylebone.
Variations: 1.increase the length of this precis to exactly 65 words. 2.reduce the length of this precis to exactly 55 words. 3.introduce one of the following words into the precis: about, although, because, if, not, unless, whether, who.
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