Venus puts a period on our Time

I left work early yesterday to scoot down to Forest Park, one of St. Louis’s best city parks, and take in the transit of Venus. The St. Louis Astronomical Society conducted a public outreach event on the grounds of the World’s Fair Pavilion. The pavilion sits atop a small hill with a good view of the western horizon. Many club members had set up telescopes for the public. Some scopes projected images of the sun and others used solar filters.  It was another large daytime star party. Hundreds of people showed up and patiently waited in telescope lines to get a glimpse of Venus crossing the Sun.

World's Fair Pavilion

Worlds Fair Pavilion in St. Louis’s Forest Park on Venus transit day.

The mood was curious and somber; parents urged their children to look and remember. Many dutifully complied but you could see they were more interested in running around the pavilion than watching a little black dot. Maybe some will remember in the decades to come; maybe one or two will live to see the next transit but for the rest of us the little black dot of Venus is a “period” to the sentence of our time. We will never see Venus’s silhouette on the Sun again.  Venus will circle on punctuating future epochs but we, my friends, will soon cease to exist — period.

Sunspotter solar transit projection

A Sunspotter transit of Venus projection.

Blurb: Nick Lomb’s Transit of Venus

Nick Lomb’s Transit of Venus 1631 to the Present is the best illustrated astronomy book for general readers since Terence Dickinson and Alan Dyer’s The Backyard Astronomer’s Guide.  Everything about Lomb’s book from its eye seizing cover, rarely seen historic photographs and charming well researched commentary is first class. Transit is the type of work you steal[1] from and frankly, there is no better endorsement than that.  I’m not the only reader to reach this conclusion check out this and this and this.

When prowling our few remaining bookstores I often skip illustrated works. Usually they’re dumbed-down rehashes of familiar material but, in Transit’s case, I learned something on my first randomly browsed page. The chapter introduction for Venus of the South Seas reads:

Sometimes scientific expeditions have unintended consequences. The desirability of observing the 1769 transit from the South Seas began a chain of events that would lead to the founding of the colony of New South Wales by the British in January 1788. In effect, modern Australia owes its existence to a celestial event.

How about that history haters. I knew why astronomers cared about transits of Venus. In 1677 Edmond Halley, of Halley’s Comet fame, described a method for calculating the astronomical unit from transit of Venus timings. Venus is close enough to the Earth that its track over the Sun differs for widely separated terrestrial observers. This is the familiar parallax effect.  From this small difference you can determine the astronomical unit and if you know the astronomical unit Kepler’s third law tells you the distance of every planet in the solar system.  This was a huge payoff for 17th, 18th and early 19th century astronomers. This is what got Cook out in the Pacific. It’s a great story and Lomb’s telling is the best you will find.


[1] I’ve picked up a few page design ideas.

2012 Venus Transit and Annular Eclipse

I’m gearing up for two big eminent celestial events. On May 20th I’ll be near Page Arizona observing an annular eclipse of the Sun and on June 5th, weather permitting, I’ll be in St. Louis watching Venus creep on the disc of the Sun for the last time in my lifetime.

Eclipses and transits are spectacular events for amateur astronomers and innocent bystanders. Of the two eclipses offer the greater spectacle. In fact, for sheer unbridled awesomeness, it’s hard to beat a total eclipse of the Sun! You can add up all the World Cups and Super Bowls ever played and they would barely register on the logarithmic total solar eclipse spectacle scale. The one total solar eclipse I saw easily ranks as the greatest thing I’ve ever seen and I’m including the births of my children. The May 20th solar eclipse is annular so it’s not in the same galaxy as a total but annular’s have their charms. At maximum eclipse the Sun appears like a perfect blazing ring of light. In Page it will be 10 degrees above the north-western horizon: a good altitude for composing solar landscape pictures.

By comparison the June 5th transit of Venus will not be a big show. Without proper equipment you won’t be able to see it at all. During transit Venus looks like a little black dot on the Sun. The best way to see this event is with telescope or binocular projection. Under no circumstances should you look directly at the Sun without proper eye protection!  For safe transit viewing techniques look here. In 2004 I used binocular projection to view the last transit of Venus from Ottawa Canada. Transits of Venus come in pairs, eight year apart, followed by over a century before the next pair.  After 2012 you will have to wait until 2117 to see another transit of Venus. This is our last chance people. Yeah mortality seriously blows.

2004 transit of Venus from Ottawa Canada. I used 10x50 binoculars to project an image of the Sun. The little dark spot on Sun's limb is the planet Venus.