Just before this BBC podcast gets underway, here's something you may not know.

My name's Linda Davies and I Commission Podcasts for BBC Sounds.

As you'd expect, at the BBC we make podcasts of the very highest quality featuring the most knowledgeable experts and genuinely engaging voices.

What you may not know is that the BBC makes podcasts about all kinds of things like pop stars,

poltergeist, cricket, and conspiracy theories and that's just a few examples.

If you'd like to discover something a little bit unexpected, find your next podcast over at BBC Sounds.

You're listening to the Witness History Podcast from the BBC World Service with me Nick Holland.

We're going back to a moment that hundreds of years ago astronomers calculated would happen in 2012. A moment that made millions of people stop and look up.

On the 5th of June 2012, Joe Carly was driving into the Australian Outback, 400 kilometers inland of his home in

Canberra.

I'm an amateur astronomer from Australia.

I've been interested in astronomy as a hobby for the last 44 years.

He was going to a spot where he had the best chance of seeing something he'd read about years before as a teenager.

In 1979 I was 16 years old.

I just started my interest in astronomy and I read an article in the Sky and Telescope

journal about these two transit of Venus

that were going to take place 25 years in the future.

So I thought I'd better mark that down in the calendar.

A Transit of Venus, a blink in time, when the orbits of Earth and Venus momentarily line up,

and for a few hours in a clear sky, it's possible to see Venus's silhouette as it passes across the face of the sun.

When Venus passes between the Earth and the Sun, anybody on the daylight side of the Earth,

anybody who can see the sun can see Venus. More than half

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