Comets are in the news this week with the worldwide apparition of Comet Wirtanen in the evening sky. We’re accustomed to being told about astronomical phenomena in detail these days — when such-and-such an event will occur, where a particular object can be seen, how bright it will appear, and so on. And yet the basic science behind this knowledge took years, and even centuries to work out. Here’s the very moment, in 1705, when mankind first understood that comets really were independent bodies orbiting the sun, each with its own period, and with predictable dates of return:
Tuesday is Books & Libraries Day at the River Houses, and the wonders of our digital age make it possible for you and your homeschool high-schoolers to encounter and explore some of the great books of the past that even just a few years ago would have been available only in the largest research libraries. The extract above is from a small essay by Edmund Halley (1656–1742) called A Synopsis of the Astronomy of Comets, published in London in 1705. Your students can examine it today:
Halley collected all the precise observations he could find on historical comets, and using the most advanced mathematics of his day he attempted to calculate their trajectories and orbits. In particular, he concluded that the remarkable comets seen in 1531, and then again in 1607, and again in 1682, were in fact all the same object, returning every 75–76 years:
“The principal Use therefore of this Table of the Elements of their Motions [the numerical table included in the essay], and that which induced me to construct it, is, That whenever a new Comet shall appear, we may be able to know, by comparing together the Elements, whether it be any of those which has appear’d before, and consequently to determine its Period, and the Axis of its Orbit, and to foretell its Return. And, indeed, there are many Things which make me believe that the Comet which Apian observ’d in the Year 1531, was the same with that which Kepler and Longomontanus took Notice of and describ’d in the Year 1607, and which I my self have seen return, and observ’d in the Year 1682.”
That’s the object we know today as Halley’s Comet, scheduled to return to the inner solar system again in the year 2061.
Somewhere out there in the homeschooling community there is a future astronomer, physicist, or mathematician ready to follow in Halley’s footsteps. By introducing your own students to the great works of the past you make it possible for them to develop their own vision for what they may be able to accomplish in the future.
What treasures have you discovered in your library lately? 😊
❡ Explore more: For a quick review of the Scientific Revolution, in which Edmund Halley played an important part, turn to page 266 in your River Houses history encyclopedia (riverhouses.org/books). It’s just the background you need for a wonderful homeschool history of science lesson.
❡ Books in the running brooks: Have you found all the local libraries in your area? There may be more than you realize! The WorldCat Library Finder (worldcat.org/libraries) will help you find all the libraries near you — public and private, large and small — and the WorldCat catalog itself (worldcat.org) will help you locate the closest copy of almost any book in the world. 😊
❡ When in doubt, go to the library: This is one of our regular Homeschool Books & Libraries posts. Add your name to our weekly mailing list (riverhouses.org/newsletter) and get great homeschool teaching ideas delivered right to your mailbox all through the year. 📚