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Hi everyone, it's Fraser here.

So this is a special episode of Astronomy Cast that we recorded during the end of the world cruise in December 2012.

We did this in front of a live show and I thought it went really well.

So it's going to correspond to episode 284 for December 10th, 2012, and the topic was Optics.

Astronomy depends on bullying light.

We reflect it, refract it, bend it, and mirror it through complex manipulation of light through optics.

We bring the distant universe to our eye.

So the show we're going to be doing Optics and we're going to be talking about refractors and lectures and lenses and eyepieces and the big telescopes and little telescopes and the weird tilt mirror lenses and the planetarium lenses and all that.

So first I'd like to sort of go back sort of into history books and talk about what was sort of the first understanding of when we started to use,

like when did scientists really start to understand how lenses were?

Europe in the late 1500s, early 1600s, we started figuring out things like magnifying glasses, microscopes, eyeglasses.

But it was adding the lenses together into compound systems that really took off in the early 1600s.

And so what was like the first application of like microscopes?

Well, a compound, it was microscopes.

But in terms of lenses themselves, magnifying glasses, which led to eyeglasses, which, if you think about it, human kind went through thousands of years where if you were near sighted, that was basically life over.

Think of all the things that our glasses allow us to do that you couldn't do until eyeglasses were invented.

And so you've got the situation where you've got people making discoveries that glass somehow bends the light.

They can see, they can make small objects of your larger, distant objects of your closer.

And so then how do they actually start to pull these things together?

Well, this actually led to a huge controversy over what light is. Is it a particle? Is it a wave?

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