"There will be no other (transit of Venus) till the twenty-first century of our era has dawned upon the earth, and the June flowers are blooming in 2004. When the last transit occurred the intellectual world was awakening from the slumber of ages, and that wondrous scientific activity which has led to our present advanced knowledge was just beginning. What will be the state of science when the next transit season arrives God only knows."
- William Harkness, director of the U.S. Naval Observatory in 1882
portions taken from:
http://www.pressherald.com/news/state/040606met.shtml
Now, or wait for 113 years
On the Web: www.transitofvenus.org
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SET YOUR ALARM
viewings of the transit of Venus will take place at dawn (just before 5 a.m.) on Tuesday June 8.
The last transit of Venus occurred on Dec. 6, 1882. The newspapers of the day recounted the event in the next day's editions:
"In the City Hall Park a telescope was erected, and so great was the rush of people to take a look through it that the services of a Park policeman were required to keep them in line awaiting their turn. Once at the telescope a view of a few seconds only was allowed, and by actual count 20 men peered through the glass in 5 minutes." - New York Times
"It was within a few minutes of the time of the third contact when a Post reporter entered the dome where the large telescope is situated. Prof. Frisby and his assistant, Mr. George Anderson, were already at the instrument. Mr. Hall, son of Prof. Hall, stood before the astronomical clock, tablet in hand, waiting to record the time. The silence was broken only by the click of the pendulum motion of the machinery beneath the telescope. Through the glass, the atmospheric disturbances, greatly magnified, made the edge of the sun bubble and boil like a great cauldron. "It is awful," said Prof. Frisby to his assistant, as he noted this drawback to a perfect observation. A moment later and the canvas dome of the room echoed a sharp "Now!" The third contact had been noted. - The Washington Post
Jeremiah Dixon and Charles Mason were attacked by a French frigate. Jean-Baptiste Chappe d'Auteroche traveled by horse-drawn sled across frozen Siberia. A French nobleman named Guillaume Joseph Hyacynthe Jean-Baptiste Le Gentil de la Galaisiere sailed 70,000 miles, staying away from home so long his relatives thought he was dead.
Other 18th-century adventurers braved typhoons, British warships and untamed wilderness - all for the chance to watch Venus pass in front of the sun, an event so rare that no person who is alive today has ever seen it.
Weather permitting, early risers Tuesday will have the opportunity to witness the transit of Venus across the sun, a celestial event that hasn't occurred since 30 years before the sinking of the Titanic and only six times since the invention of the telescope.
"We'll be watching an event that a very, very small percentage of people in world history have ever seen," said Edward Gleason, manager of the Southworth Planetarium at the University of Southern Maine.
Historically, there's a 60 percent chance that the skies will not be totally overcast that day, according to Robert A. Burgess of the ASNNE, who is also a NASA "solar system ambassador" for Maine.
The event will take a little more than six hours. The transit begins at 1:15 a.m., but in the Northeast it will only be visible from sunrise at 4:56 a.m. until the silhouette of Venus leaves the sun at 7:25 a.m.
Venus will look like a small dark spot traveling across the sun. It will not have the same kind of dramatic effect as an eclipse, when the sun is largely obscured and a shadow falls on Earth.
"If you had no idea the transit was happening, you wouldn't notice any difference," Gleason said. "It's not really going to block out much of the sun at all."
The transit will have its own optical effects, however.
Watch for the "black drop effect," which occurs just as the disc of Venus gets close to the edge of the sun. The effect makes it difficult to see exactly when the two edges coincide, just like bringing a thumb and forefinger together until they're almost touching.
"There turns out to be a huge sunspot group on the sun now, so people will probably see a sunspot group in addition to Venus," said Murray Campbell, a professor of physics and astronomy at Colby College. "Venus will look like a simple circle, and the sunspots will have structure to them."
Transits of Venus occur in pairs. The crossings are eight years apart, and each pair is separated by more than a century.
The planets all orbit the sun in slightly different planes, tilted at different inclinations, Campbell explained. On rare occasions, one of the planets lines up directly with the Earth and the sun.
"In this case what's happening is the plane of Venus' orbit and the plane of the Earth's orbit are intersecting just as Venus passes between the Earth and the sun," Campbell said. "And it's this tilt of the different planes that causes it to be a rare event. It's the same effect that causes eclipses to be rare. If the moon were in exactly the same plane of orbit as the Earth is around the sun, you would have eclipses every full moon and every new moon. But because the plane of the moon's orbit is inclined, you don't get frequent eclipses."
Previous transits of Venus were witnessed by humans in 1639, 1761, 1769, 1874 and 1882. The next one will take place in 2012, when the West Coast will be able to catch the beginning of it at sunset. The East Coast won't view another one until 2117.
"This is the last chance for [the northeast] for 113 years," Burgess said.
Johannes Kepler first predicted when a transit of Venus would occur, but didn't get to see it. Eight years later, in 1639, a young British astronomer named Jeremiah Horrocks took Kepler's work and figured out the next one would occur in just a few weeks. To make sure clouds wouldn't be a problem, he asked a friend, William Crabtree, to try to view the transit from another town.
"It was cloudy, and I think it was on a Sunday," Burgess said. "The skies parted late in the day, and they became the first two people to have ever witnessed it."
In 1716, Edmond Halley proposed that transits of Venus could be used to find what was then the Holy Grail of astronomy - an accurate measure of the distance between the Earth and the sun, which would then give scientists an absolute "yardstick" to measure the size of the solar system.
"Once they knew the distance between Earth and Venus," Burgess said, "they knew the distance to the sun and all the other known planets, out to Saturn."
As the 18th-century transits approached, astronomers grew excited at the prospect of finding this yardstick. But to do their calculations, they needed measurements of the transits from places on Earth where the events would be visible.
"The English and the French both sent out expeditions to various parts of the world," Campbell said. "In some sense, they were competing with each other. To get the distances, you had to have people observing how long it took Venus to cross the disc of the sun from two different locations on Earth."
Capt. James Cook watched the 1769 transit from Tahiti. Ben Franklin saw it, too, in 1761, and greatly raised the scientific cachet of the American colonies.
People risked their lives trying to reach inaccessible corners of the globe. In 1761 Jeremiah Dixon and Charles Mason set sail from England for Sumatra, but their ship was attacked by a French frigate and 11 people were killed. After regrouping, they left again and made it as far as South Africa before they had to go ashore to make their observations of the transit.
That same year, Guillaume Joseph Hyacynthe Jean-Baptiste Le Gentil de la Galaisiere, a French nobleman, traveled to the island of Mauritius, a French colony in the Indian Ocean. His ultimate destination was Pondicherry, India, but when he arrived there he ran into British warships and had to turn back to Mauritius. The transit of Venus occurred while he was at sea, where it was impossible to take accurate measurements.
Undeterred, he decided to wait eight years for the next opportunity. In 1769, he finally made it to India - but on the day of the transit, clouds covered the sun. After suffering from dysentery and watching a hurricane almost tear his ship apart, he finally arrived home to find his estate looted by robbers and relatives who thought he was dead.
The last transit of Venus occurred on Dec. 6, 1882. Jesse James, the famous outlaw, died that year. So did Charles Darwin, Henry Wadsworth Longfellow and Mary Todd Lincoln. Chester Arthur was president.
The celestial show was splashed across the front pages, and the public was as eager to watch the spectacle as the scientists. The Dec. 7, 1882, edition of The New York Times noted that crowds formed on the sidewalks of New York City, where enterprising amateur astronomers offered access to their telescopes for 10 cents a peek.
In Maine, the weather obscured the first and last parts of the transit, but Portland's Daily Eastern Argus reported that Professor M.C. Fernald of the State College in Orono and other skywatchers were able to get a short glimpse of the event.
William Harkness, director of the U.S. Naval Observatory in 1882, poetically pondered what the world would be like the next time Venus inched across the sun:
"There will be no other (transit of Venus) till the twenty-first century of our era has dawned upon the earth, and the June flowers are blooming in 2004. When the last transit occurred the intellectual world was awakening from the slumber of ages, and that wondrous scientific activity which has led to our present advanced knowledge was just beginning. What will be the state of science when the next transit season arrives God only knows."
What would Harkness make of this world, where people will be traveling on jet planes instead of wooden ships to view the transit from Mauritius, and where they won't even have to step outside to watch a live Webcast of the event on the Internet?
Robert Burgess feels a kinship with Harkness and others who looked to their descendants to continue the transit of Venus chain.
"I just find it somehow very exciting, that he was there witnessing this and thinking ahead to the time right now, when I'm alive," Burgess said. "I feel like I want to be part of that connection, that chain of sharing the excitement of witnessing this."
On the Web: www.transitofvenus.org