As long ago as 1200 BC, Babyloneans named the 'Evening Star' for the goddess of love, Ishtar.  When the Greeks borrowed the cult of Ishtar and Astarte to build the mythology surrounding Aphrodite, which the Romans later altered  to Venus, each appropriation carried on the tradition of recognizing the third brightest luminary in the sky as the deification of love.

For the ancients, a planet that appeared in the morning sky, disappeared for a short while, then popped up in the evening sky soon after, seemed an apt expression of the goddess of love.  What could be more mysterious, more changeable than this planet, seemingly arbitrary but always beautiful in its apparition?  So like the nature of love.  A fragment from Sophocles on Aphrodite/Venus expresses this maddening duality:

O children—she of Kypros is
                         Not only called “the Kyprian”
But is named many
                         Times with many names.
She’s death—and the realm thereof,
                         She’s undestroyable life,
She’s madness raving loose, She’s
                         Undiluted hot desire,
She is a wailing with pain,
                         With sorrow, with rage, with fear.
All real, excellent energy’s
                         In her, and all restedness too.
And all that leads us into
                         Violence.

Despite the allure of mysteries, as humans we also feel compelled to analyze them.  Thus, from the Babylonians on, the secrets of the solar system have slowly been peeled away.  By the time time Sophocles wrote the above, close to 2500 years ago, 5 planets in our solar system had already been identified.  Through the following millennia, however, scientific strides weren't consistent.  It took almost 2000 more years for western thinkers to accept that the Earth and the planets revolved around the sun.  And it took a few more hundred years before scientists got close to an accurate measurement of the distance between the Earth and the Sun.  In 1761, in order to make this incredible attempt, they relied on our girl Venus.

With their orbits situated between the Earth and the Sun, both Mercury and Venus eventually intercept our sightline of the Sun.  When conditions are ideal, the planets will be close enough to appear in silhouette against the sun's glowing disk.  We call these transits.  Mercury is such a speedy planet that its transits average about 13 times a century.  But since the telescope was invented there have only been 5 Venus transits of the Sun.  

Venus transits appear in 8 year pairs and then experience an incredible hiatus of either 105.5 or 121.5 years.  The first Venus transit viewed on Earth was in 1631.  After the second of that pair was observed in 1639, a mathematician proposed a general method for using transits to measure the distance between the Earth and the Sun.  For the next transit, in 1761, over one hundred astronomers at over 60 locations throughout Europe gathered the data needed to calculate this number.


The various stories that resulted from these expeditions are a fascinating read (see Nick Lomb's Transit of Venus:  1631 to the Present, for instance).  And while the data failed to give a precise measurement of the Earth-sun distance, they provided astronomers with a better sense of the solar system's scale.  

Now astronomers rely on a pulse from a radio telescope, timing the wait for the return signal, in order to chart distance.  But once, not so long ago, men were dispatched to the farthest reaches of the globe to watch Venus cast her shadow across the face of the Sun.  The Babylonians, Greeks, Romans — none of them would have been surprised to learn this.  As Sophocles reminds us

For who is not hungry
For this goddess? [...]
Among the gods up above.
Wrestling Her, which of the gods does she fail to throw three times?

 

The last transit of Venus until 2117 will occur in the western Hemisphere (including North America) on June 5, 2012.  Check out NASA's SITE to find out the best time to view it in your location. Follow the prescribed methods for viewing (the same equipment for viewing solar eclipses is necessary) and join in this once-in-a-lifetime view of Venus, the goddess of love, reminding us of her preeminence, historically, scientifically, culturally and personally.