Transit of Venus – as it happened
Join us as we track the final time that Venus will cross the sun in our lifetime with tidbits of history, snatches of science and scraps of literature to enhance the viewing
• All times ET
• All times ET
• What's the transit of Venus? It's Venus crossing the sun, and it is one of the most celebrated spectacles in all of astronomy. That's because a pair of such transits in the late 18th-century allowed astronomers to calculate for the first time how big the solar system is. Also it looks cool.
• Can I watch it? Yes. Local viewing times are here. In the eastern US it begins at 6.03pm and ends at 12.51am. Astute readers will note that viewing in the east will necessarily be cut short; the sun is not visible at midnight. True, but thanks to Nasa, you can watch the entire breathtaking transit here. Nasa's live coverage begins at 5.45pm ET.
• Do I need special eye protection to view the transit? If you're old enough to read this live blog (which after dark will feature 19th-century nudes of the goddess Venus), you're old enough to know that the answer to that question is yes. To stare into the sun is to risk grave eye damage without the guarantee of sympathy. Nasa has a guide to safe solar viewing here.
• A dot on the sun. What's the big deal? Three quick answers: the transit of Venus set in motion one of the greatest quests of all time, a race across the seas to measure the heavens; the transit produced one of the greatest breakthroughs in the history of science; and it won't happen again till 2117, 105 years from now. (The last one occurred in 2004; there were none in all the 20th-century.) Join us!
Read the whole Q&A here.
What have scientists used the transit for?
In the 18th century astronomers set out to far-flung corners of the globe to time the transit of Venus. Combined, their results gave them the first accurate measurement of the distance between the Earth and the sun, a figure they calculated to be between 93 million and 97 million miles (172-180 million kilometres). Today, the accepted distance is 93 million miles. The result allowed astronomers to calculate the size of the solar system.
Nasa has produced a video explaining the transit of Venus, embedded below, with this to say about the historical importance of the transit:
"Astronomer Sir Edmond Halley realized that by observing transits from widely spaced locations on Earth, it should be possible to triangulate the distance to Venus. The idea galvanized scientists, who set off on expeditions around the world to view a pair of transits in the 1760s. The great explorer James Cook himself was dispatched to observe one from Tahiti, a place as alien to 18th-century Europeans as moon or Mars."
The historian Andrea Wulf, author of the lovely book "Chasing Venus: The Race to Measure the Heavens," spoke to the Guardian about Halley's role in launching the world expeditions to view the transit – after his death:
IN 1716, almost 50 years before the 1761 transit happens, Halley sits down and he writes an essay, in Latin, because that's the international language of science.. ... and in this essay, he says, 'This is what we have to do. In 1761, you all have to work together.' And he very much emphasizes that all the different European nations should make use of their colonial possessions. The English would send someone out to India, the Dutch to Jakarta. He's using the trading empires to have this idea.You can listen to the full interview with Wulf here.
He knows that this can only happen if everybody works together. That's why he writes it in Latin. And what's so visionary about it is he knows that he's not going to see this, unless he would be 104, which he knows he's not going to be. So it's like a call of action for a future generation.
"The planet Venus drawn from her seclusion, modesly delineating on the sun, without disguise, her real magnitude, whilst her disc, at other times SO lovely, is here obscured in melancholy gloom."
Sousa was known as "The March King." And you know what calls for a march? A planet marching across the face of the sun.
The December 1882 Transit of Venus lasted 6 hours and 18 minutes, according to NASA.
The next year, Sousa published his "Transit of Venus" march. It's about two minutes long, depending on your tempo, meaning that it could have been played on repeat approximately 189 times during the 1882 transit.
Can you imagine hearing this 189 times in a row?
The painting, completed in 1886, now adorns the ceiling of the western rotunda of the Perrault wing of the Paris Observatory.
In the painting the sun is on a chariot surrounded by fog and rosy-cheeked nudes. Venus is naked, wearing a star on her head, attended by doves.
The transit center falls at 21:27:27; the egress interior at 24:33:33 and the egress exterior at 24:51:25.
We're preparing links to other live streams. Meanwhile:
First contact at #VenusTransit will happen soon. Latest image from the Solar Dynamics Observatory yfrog.com/esjr3wqj
— Ever Lazz (@Everlazz) June 5, 2012
For those observers viewing the phenomenon directly, the planet appears to be crossing the sun from the lower left.
Contacted by phone at the event, Kendall yells "What did we just see five minutes ago?" and raises his phone to the crowd.
"Venus!!" a wave of exuberant yells comes back.
"Almost 900 people are here on the pier," said Kendall. "We've been able to see it, despite the clouds. We saw second contact and now it's getting across. We've handed out a couple hundred sunglasses, and people are having a great time watching it, and it's a great succses here in NYC!"
Kendall said the sun was lowering toward the Hudson but there were still a good two hours of viewing time left.
"We're kind of fortunate that we have clouds, because we're at capacity here," Kendall said. "I think the clouds discouraged some people."
"They're having fun when they see it, it's very exciting when it comes out. It's officially a happening here in New York City!"
They all were acting at the behest of one man: Edmond Halley, who died in 1742.
Why was Halley so eager that hordes of astronomers disperse to the ends of the Earth decades after his death to watch a planet pass between the Earth and the sun?
Halley realized that accurate measurements of the time it took Venus to cross the sun, when taken from distant points on Earth, could be used to establish the distance between the Earth and Venus, and thus the distance between the Earth and the sun.
The 17th century German mathematician Johannes Kepler had already calculated the proportional distances of the solar system. Thanks to Kepler, scientists knew that Jupiter is five times as far away from the sun as Earth is, for example.
They knew the proportional distances. They just didn't know the absolute distances. This was the central quest of astronomy: to determine the size of the solar system.
And suddenly Halley saw how it could be done, using the transit of Venus.
And the sun smiled upon us! #venustransit twitpic.com/9t7ern
— Kathy Ceceri (@KathyCeceri) June 5, 2012
aforementioned John Philip Sousa, the renowned composer of the march "Transit of Venus," among other marches, was also a novelist.He wrote the march in 1883, but Sousa wasn't done with the transit. In 1920 he published a novel called "The Transit of Venus." The
Here's the crucial scene, on page 221:
The day of days for the expedition arrived. The observation of the transit was a superb success. The sky was clear, the sun shone brightly, and the little black disc we call Venus, situated between our planet and the sun, behaved like a real lady, and photographs and data of value were obtained.Riveting stuff.
Thanks to Google's work at digitizing the holdings of the New York Public library, you can read the entire novel, all 250 pages, online here.
Do you know what else John Philip Sousa was preternaturally gifted at? Trapshooting. He apparently never missed. His induction page to the Trapshooting Hall of Fame, which exists, is here.
Katie Rogers has a dispatch from space – cyberspace:In a Google+ corner of the Internet, several professional and amateur astronomers from Vancouver Island to San Francisco have attached their telescopes to cameras and are My colleague "hanging out" in real-time.
Fraser Cain, founder of space website Universe Today, said the group bumped its weekly "Virtual Star Party" to Tuesday in order to watch the event.
What can a novice stargazer learn from this transit?
"Only six [transits] have occurred since the invention of the telescope," Cain said. "It's because of the transit of Venus that we even know how big the solar system is. It's one of the most fundamental observations that have ever been made in the history of astronomy."
Chasing Venus: The Race to Measure the Heavens," Andrea Wulf traces the dramatic transformation of Venus from object of mythological awe to instrument of scientific revelation.In her magisterial " Here's Wulf:
The Ancient Babylonians called her Ishtar, too the Greeks she was Aphrodite and to the Romans Venus – goddess of love, fertility, and beauty. She is the brightest star in the night sky and visible even on a clear day. Some saw her as the harbinger of morning and evening, of new seasons or portentous times. She reigns as the 'Morning Star' or the 'Bringer of Light' for 260 days, and then disappears to rise again as the 'Evening Star' and the 'Bringer of Dawn.'
Venus has inspired people for centuries, but in the 1760s astronomers believed that the planet held the answer to one of the biggest questions in science – she was the key to understanding the size of the solar system.
In the below image, courtesy of Nasa, the path Venus is taking is flipped, so that it appears the planet is crossing the sun from the upper right. In fact, from our vantage, Venus is crossing the sun across the bottom from the lower left.
She looks a bit lonely out there. No?
Imagine two different people, one on each pole of the Earth, viewing the transit of Venus. The person on the North pole sees Venus following one path across the Sun. The person on the South pole sees Venus follow a slightly higher path, one that's shifted a little to the north.Visit the Exploratorium here.
Because we see the Sun as a circle, these two different paths will have different lengths. Halley proposed that an easy way to measure the difference between the lengths of these two paths would be to time the transits, using the four phases of the transit—the first, second, third, and fourth contacts—as indicators.
With the two different paths known, the distance between the Earth and the Sun can be pretty easily calculated using trigonometry and Kepler's third law of planetary motion.
There's more trigonometry where that came from.
In "The Age of Wonder," Richard Holmes argues that Cook's great voyage marked the dawn of a golden age of Romantic science – romantic in the same sense that we have Romantic poetry. (The Age of Wonder ended, Holmes says, with the voyage of Charles Darwin's Beagle to the Galapagos islands in 1831.)
Here's Holmes on Cook's trip:
The Endeavour expedition remained for three months on Tahiti. Its main object was to observe a Transit of Venus across the face of the sun. (Cook stated that this was the reason their settlement was named Fort Venus, though his junior officers gave a different explanation.)In an interview with the Guardian, historian Andrea Wulf summarized the results of the expedition and others around the world.
The expedition was organised by the Admiralty, but also partly financed by the Royal Society, which suppled L4,000 towards astronomical observations. [...]
Through the brilliance of Cook's navigation, and the skill of his crew-management, the Endeavour arrived at Tahiti with over six weeks in which to prepare for its main task, the transit observations. Previous expeditions had often been decimated by this stage, but Cook had lost only four men, and none to disease.
They start calculating [the distance from the Earth to the sun] in the summer after the transit. But they have to wait for Cook to come back, in July 1771. Then they calculate and they come up with a range that goes from 93 million miles to 97 million miles. Today's value is just under 93 million.
So they're pretty, pretty, pretty close. Compared to what they thought in the 17th century. So I think the result is pretty impressive.
Please people get some good pictures, if you can. Can't see nothing in Seattle - the weather thing, you know.Can do, liliyaW! Here is a gallery of images of Venus making her transit – and of Earthlings watching it.
And here's a Nasa shot. The sun: it's hot.
Can anyone tell me what the other black dots are we see? Are these sun spots? Are they stationary?
My colleague Katie Rogers spoke with astronomer Fraser Cain, who is running an online transit of Venus meetup.
Of those black dots not Venus, Fraser Cain says: "They are sunspots."
Andrea Wulf, author of Chasing Venus, recounted the story in her interview with the Guardian:
The most doomed of all was a French guy called Guillaume Le Gentil. He was the first in the race. He leaves [France] in March 1760. He leaves France to go to Pondicherry, which was then in French hands, in India. And everything goes wrong on this voyage.
His boat gets attacked by the British, he gets in a hurricane, his health is ruined by dysentary. So it takes him 14 months to finally see the coast of India, and it's like two weeks before the transit, so it's all getting a bit tight here.
And then he receives the devastating news that the British have just taken Pondicherry, so he can't go ashore. So he's stuck on a rolling boat with a pendulum clock, which is of no use at all.
So he sees the transit, but scientifically it's of no use because he can't time it.
So then he thinks, 'Nevermind, there's the next transit in eight years.'
He hangs out in the region. He doesn't go back to Paris. Three years later he travels from Mauritius to Manila. Three years in advance [of the second transit]. Builds his observatory. Sets up his instruments. Then he gets a letter from the French Academy of Sciences sending him back to Pondicherry. He arrives back in Pondicherry a year in advance. Builds his observatory and then waits for the transit.
And then on the day of the transit, he wakes up and there's this howling wind. He looks out, and there are just clouds. He just sees the sun as this kind of dim light behind a curtain of clouds.
A few hours after the transit, the clouds disappear and the sun shines again.
He returns back. The story goes on.
He arrives in Paris in '71, 11 years after he's left. He finds that his heirs have declared him dead, divided up his estate, and he's lost his job in the Academy of Science.
So he's clearly the most doomed and jinxed of them all.
Set up our telescope and got a pretty good projection of the #VenusTransit. So cool to witness this rare event! twitpic.com/9t96z4
— Mindi Capp (@MCapp22) June 6, 2012
It turned out that the phenomenon would be entirely invisible to people living in certain areas; if the sun is not up where you live at the time of the transit, you won't catch it.
But the shapes of those "invisible" areas, and whether they were in the northern or southern hemisphere, were difficult to intuit. It's not as if viewability of the transit marched across the globe degree by degree. Visibility depended upon the tilt and rotation of the earth as well.
Here's a map of the global visibility of this year's transit of Venus.
Delisle figured it out 250 years ago.
Coming up is the egress interior (12.33am ET, 5.33am BST) to be followed by the egress exterior 18 minutes later.
And then we will never see it again.
We're going to end this live blog now and join those of you watching the Nasa live feed. We want to thank you for reading and especially for all the insightful comments.