The distinction between the theories—and the distortions that distinction might produce—was minor, Horrocks knew. But scaled against the solar system, at distances that could be cadenced in thousands of Earth radii, it was just large enough to turn a non-event into a full-blown transit of Venus. Kepler's Rudolphine Tables had Venus passing just above the sun on November 24, 1639. Horrocks predicted that Venus would pass in front of the sun, just as it had eight years earlier.
And this was not all. Horrocks believed that this, the second Venus transit of the decade, was no fluke. Yes, he agreed, Kepler was right about the frequency of Venus transits. They recurred at intervals 105.5 and 121.5 years. But Horrocks now claimed that they recurred in pairs. After 105.5 years, two Venus transits would occur, eight years apart. Then, after 121.5 years, two more Venus transits would follow, again eight years apart. Horrocks believed that Venus transits would no longer be isolated events—nor had they ever been.
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Add CommentHi there, interesting how a badly researched article can appear on the website of such a prestigious publication, when summing up all the errors it contains, as done in Thony Christie's blog here: http://thonyc.wordpress.com/2012/06/02/scientific-american-craps-out/. Just one bit of cross-verification through Wikipedia about the main features of Copernicus' heliocentric theory, see: http://en.wikipedia.org/wiki/Copernican_heliocentrism.
Reply | Report Abuse | Link to thisMakes me think about publishing standards and procedures for scientific material. Hmm...
Cheers Jiri
Thony Christie's writes that words fail him, but in truth they merely betray his as rash and mostly wrong. For starters:
Reply | Report Abuse | Link to thisCambridge University records show Jeremiah Horrocks entering Emmanuel College on May 18, 1632 as a sizar--a student who supplemented his tuition by performing menial tasks. Why would a wealthy father subject a gifted son to this indignity? And as far as the nature and location of Horrocks’ observatory, we can only speculate, although they were clearly not as elaborate as Tycho’s.
The device Gassendi used during the 1631 transit of Mercury is properly defined as a camera obscura.
Keeping track of dates can be difficult for one who straddles centuries. Every author deserves at least one mulligan. I offer one here for Mr. Christie. Copernicus published De Revolutionibus in 1543 (although he had circulated draft versions of his heliocentric theory to friends and colleagues on or before 1514.) Both dates fall well within the 16th century. Again, the 16th century. Kepler worked with Tycho Brahe in 1600, published Astronomia Nova in 1609,and his third law in 1619. His major contributions all occur in the 17th century, the one in which Kepler lived from age 28 until his death in 1630.
Sure, Copernicus explained retrograde motion. So did Ptolemy, and Aristotle. They just didn't explain it right. Of course the heliocentric model is light years better than those with jury-rigged epicycles or nesting spheres to illustrate why planets seem to move backwards in their orbits. But the phenomenon of retrograde motion wasn’t fully understood until Kepler.
As far as Galileo goes,my bad. Mr. Galilei worked with the 10x scopes in 1608. By 1610, during his observation of the phases of Venus, he did have a 30x. And it is true that in 17th century astronomy the known bodies were referred to as stars. But these bodies were divided into two categories: Galileo himself refers to fixed stars (still known as stars,) and wandering stars (known today as planets) in Sidereus Nuncius. In a 1610 letter to Cosimo II, Grand Duke of Tuscany, he refers to the moons of Jupiter as planets, and later as Medician stars. I’m happy to parse the language further, but the matter here is that Galileo’s observations of the phases of Venus confirmed that Venus orbited the sun and was, just like the earth, a planet.
I don’t think I’m telling Mr. Christie anything he doesn’t already know. But I will tell him if he cares as much about the stars and the truth as he professes to, he certainly should know better.