Introduction
An important celestial event will take place on June 8, 2004.The planet Venus will be so perfectly aligned with the sun as viewed from the earth, that the planet will appear as a black dot on the solar disc. This event is called Transit of Venus as Venus transits or passes in front of the sun. Such an occurrence is a rare astronomical event. In fact it has never occurred in the 20th century at all!
As per historical records Jeremiah Horrocks was the first human to witness this event on Sunday Dec 4, 1639.Who was this Jeremiah Horrocks? He was a very young Englishman who had some responsibilities to perform in a Church in Liverpool. He had mastery over Keplerian Astronomy which was only a few decades old at that time. In addition he was a keen observer of the sky. The records state that he was poor but he seems to have bought himself the new invention of those times, a telescope. (University of Central Lancashire website 2004)
Kepler had predicted for the first time, that a transit of Venus will take place in 1631. NO one in Europe saw it because the sun was below the horizon in Europe during the transit. Horrocks made his own calculation and found that the transit if Venus occurred in pairs by separated an interval of eight years. Thus he was ready in 1639 to verify his own calculations that predicted a transit for Dec 4, 1639. He set up this telescope on that see the sun’s image in projection right from the morning. He had drawn a circle with degree markings into which the projected image of the sun would fit and on which he would mark the position of Venus.
He started his vigil the day before fully conscious that calculations could be in error by as much as a day. No Venus! The next day, Dec 4, 1639 was a Sunday. The sky was intermittently cloudy and he was called away for some period by his responsibilities at the church. But Lady luck was on his side. He returned in time to his telescope while Venus as a dark spot was still on the solar disc! He made three observations of its position before the sun dipped below the horizon of Liverpool. Horrocks had entered the pages of history. He became the first human to see Venus as a black dot on the disc of the sun. Since that time ONLY two pairs of transits of Venus have taken place and we are readying for the next pair to occur on June 8, 2004 and June6, 2012. Horrocks observed the transit by projecting the sun’s image formed by a telescope on a screen and observing it. This is the best way to view the transit even today. Project the image of the sun through a telescope on a screen and view it (NEVER LOOK AT THE SUN THROUGH A TELESCOPE, BUT ONLY IN PROJECTION)
The question this article wishes to raise is ‘ Could Horrocks have seen the transit of Venus on that Sunday afternoon with his naked eye, with out the help of a telescope’?
 

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