Welcome to Stardate: The Transit of Venus.

Although the Transit of Venus is fantastically rare - the last one happened in 1881 - they happen in pairs, so they're not quite once-in-a-lifetime events. However, this Transit is special for us in the UK as its "twin", in 2012, won't be visible in Britain and the one after that will be in 2117! So this really is your only chance to experience one here in the UK.

But is the Transit of Venus anything more than just a rare coincidence? As we'll show you, the passage of a planet crossing the disc of the sun was really important in helping people work out the Astronomical Unit - that's the distance between the Earth and the Sun, and that in turn is important for all sorts of calculations about space and the planets.

Indeed, in the past Transits of Venus were considered to be so important that astronomers would spend years of their life crossing the oceans to get in a good position to view them. You can find out more in our article about the history of the Transit of Venus.

Luckily, you don't have to go so far - you can switch on the television and join us, or check out our events page to find Transit of Venus events near you. However you decide to enjoy this rare event, do be careful - looking at the sun is fantastically dangerous. So please, make sure you read our safety advice.

And do join in - have a look at our fabulous interactive calculator, which will let you take your own measurements of the transit and see how close you can get to working out the distance between the sun and the earth, and tell us all about your experiences in the forum.

I hope you enjoy this amazing event!

Adam Hart-Davis