Once serious science. Venus transit still wows

When Capt. James Cook stood on what he would later call Venus Point on Tahiti’s shores in June 1769, he, his naturalist, Joseph Banks, and several assistants, observed the shadow of Venus move slowly across the sun’s bright face. They each carefully noted the time the planet first appeared to touch the sun with a black-drop effect. They timed its arc across the sun and then noted when its black shape slipped from view. Then they discovered that their measurements all disagreed — by as much as 42 seconds.

Using a technique employed by Capt. Cook in Tahiti in 1769, photographer Sally Andrew projects the disk of the sun on the title page of Cook’s journals during the recent transit of Venus.
   Image Credit: Courtesy University Central Lancashire/Soho Consortium

This experience was not uncommon, and the 1769 attempt to use the transit of Venus as a tool to measure the earth’s distance from the sun and consequently the size of the solar system, was a failure. Around the world, astronomers found that their tools were too primitive to measure the phenomenon accurately. (This measurement was finally achieved in the 19th century with the use of photography, according to NASA records.)

Cook, usually more taciturn in his observations, was fairly ebullient in his journal: “This day prov’d as favourable to our purpose as we could wish, not a Clowd was to be seen … and the Air was perfectly clear, so that we had every advantage we could desire in Observing the whole of the passage of the Planet of Venus of the Suns disk: we very distinctly saw an atmosphere or dusky shade round the body of the Planet.” He also sketched a careful diagram in his notebook.

On June 8, 2004, the transit of Venus again brought crowds of observers outside to stare at the sky with shaded binoculars and telescopes, from Sydney to New York and all points in between, although some were foiled by clouds, fog and even smog. Those who were thus confounded have another opportunity, since the event happens in eight-year pairs about every 120 years. The next transit occurs June 6, 2012. See you in Tahiti.

By Ocean Navigator