We missed it

Tokyo on Wednesday, June 6, was covered by clouds and sprinkled by intermittent rain--especially in the morning, when we should have been able to witness the planet Venus's transit across the sun. For simple folk like me, it would have been interesting because of the event's rarity. But scientists have a much deeper interest. Here is how they explain the significance of the Venus transit:

Planetary transits have enduring scientific value.

"Timing the transit from two widely separated places on the Earth's surface allows you to work out the distance to Venus and hence the size of the solar system," explained Fred Watson, astronomer-in-chief at the Australian Astronomical Observatory.

Scientists say it also allows them to learn more about how to decipher the atmospheres of planets outside our solar system as they cross in front of their own stars.

Only six transits have ever been observed — in 1639, 1761, 1769, 1874, 1882 and 2004 — because they need magnification to be seen properly, though the event has happened 53 times between 2000 BC and 2004.