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Back in the mid-17 hundreds, people were just beginning to figure out the vast scale of the solar system. And thanks to astronomer Johannes Kepler,

we've known since the 1600s what the relative distances of planets are,

how far from the sun other planets are compared with Earth.

We had a scale of knowing, you know, that Mercury was closer to the sun, that Venus then

was closer to the sun, then it was fast, and then it was Mars.

So we figure out our position in the solar system.

That's Chilean astronomer Dr. Barbara Rojas Ayala. She said Kepler outlined those ratios

but the actual distance from the sun to the earth alluded us. Luckily,

there's a cosmic event that happens roughly every 120 years. A pair of sightings eight years

apart that would give us a glimpse of our true place in the solar system. It's

called the Venus Transit.

And a really important one began in 1761.

This set off the space race of the 18th century.

Or as Barbara would describe it, Odyssees, in the sense that they have to have passed all of these obstacles in order to get to a place and settle there with their instruments and everything

and hope for a sunny day with no clouds to be able to measure this transit.

The treasure they were searching for

was exact measurements of Venus crossing

in front of the sun.

You could see it from various far-flung points

in the world, which would make this a massive global undertaking.

Countries spent fortunes to send astronomers around the world, all to measure a tiny black

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