Front Page Titles (by Subject) CHAP. IV.: Of the Earth, considered as a Planet. - The Works, vol. 2 An Essay concerning Human Understanding Part 2 and Other Writings
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CHAP. IV.: Of the Earth, considered as a Planet. - John Locke, The Works, vol. 2 An Essay concerning Human Understanding Part 2 and Other Writings 
The Works of John Locke in Nine Volumes, (London: Rivington, 1824 12th ed.). Vol. 2.
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Of the Earth, considered as a Planet.
The earth, by its revolution about the sun in 365 days, 5 hours, 49 minutes, makes that space of time we call a year.
The line, which the centre of the earth describes in its annual revolution about the sun, is called ecliptic.
The annual motion of the earth about the sun, is in the order of the signs of the zodiac; that is, speaking vulgarly, from west to east.
Besides this annual revolution of the earth about the sun in the ecliptic, the earth turns round upon its own axis in 24 hours.
The turning of the earth upon its own axis every 24 hours, whilst it moves round the sun in a year, we may conceive by the running of a bowl on a bowling-green; in which not only the centre of the bowl hath a progressive motion on the green; but the bowl in its going orward from one part of the green to another, turns round about its own axis.
The turning of the earth on its own axis, makes the difference of day and night; it being day in those parts of the earth which are turned towards the sun; and night in those parts which are in the shade, or turned from the sun.
The annual revolution of the earth in the ecliptic, is the cause of the different seasons, and of the several lengths of days and nights, in every part of the world, in the course of the year.
The reason of it, is the earth’s going round its own axis in the ecliptic, but at the same time keeping every where its axis equally inclined to the plane of the ecliptic, and parallel to itself. For the plane of the ecliptic inclining to the plane of the equator, 23 degrees and an half, makes that the earth, moving round in the ecliptic, hath sometimes one of its poles, and sometimes the other nearer the sun.
If the diameter of the sun be to the diameter of the earth, as 48 to 1, as by some it is accounted; then the disk of the sun, speaking “numero rotundo,” is above 2000 times bigger than the disk of the earth; and the globe of the sun is above 100,000 times bigger than the globe of the earth.
The distance of the earth’s orbit from the sun, is above 200,000 semi-diameters of the earth.
If a cannon-bullet should come from the sun, with the same velocity it hath when it is shot out of the mouth of a cannon, it would be 25 years in coming to the earth.