Hank Green: We all know what a telescope is, but if you tried to describe one, you might say something like, "It's a tube, with lenses in it!" which would be quite wrong. A telescope is just a device that lets you see far away things close-up, and you may be surprised to discover that neither a tube, nor lenses, are required.

(Intro)

The first telescope was created in Holland, probably by a Hans Lippershey in 1608, and yes, it was a tube with lenses in it. But lenses are heavy, and expensive, and tend to bend different wavelengths of light differently, making distant images blurry.

Johannes Kepler, Galileo Galilei and Christiaan Huygens all used this sort of telescope though, and to great effect! It was so revolutionary that Galileo was imprisoned for the knowledge he obtained from it. Before his persecution, Galileo was working on a new design for a new telescope, one that used mirrors instead of lenses. But the world would have to wait for Isaac Newton, fresh from getting hit in the head by apples and inventing calculus to come along and actually build the thing. Newtons reflecting, rather than refracting telescope, was the first of its kind. But it wasn't long before a more advance model, the Cassegrain telescope, with one parabolic primary mirror reflecting onto a hyperbolic secondary mirror kicked it to the curb.

Laurent Cassegrain published the design of his telescope in 1668, and it remains to this day, pretty much the standard, from the telescope in your geeky neighbor's backyard, to the Hubble. 

Once we had the Cassegrain system, the design was no longer the limitation, the atmosphere was. The air around our planet, even on the clearest days, scatters light and makes extremely distant observation impossible. While a lot was done to improve on the Cassegrain design, with bigger, better mirrors, the only way to leap forward was to put one in orbit, which is exactly what we did in 1990 with the Hubble. And the Hubble is magnificent. I believe it to be one of the primary legacies of our time, providing some of the most inspiring pictures and detailed data about our universe, stuff that we could have never have acquired without it. But, what comes next?

Well, I got to learn all about that when I visited the team responsible for building the next big thing in telescopes at Northrop Grumman in Southern California, the James Webb Space Telescope.

Scott Willoughby: Astrophysics, every ten years, you know 2000, 2010, does a survey and says "What do we want?" and they said "We want an infrared telescope."

Hank Green: The spectrum of light is massive. We see only a very tiny percentage of that, and there are telescopes that can see at pretty much every wavelength. But perhaps the hardest part of the spectrum for astronomers to see is the infrared. IR radiation is everywhere, we're bathed in it all the time, so any detector designed to see faint infrared light has to contend with all that background radiation. It would pick up heat from the Earth, from the Sun, from nearby machinery, there's just no way to block it all out. 

Well, actually there is one way. Put the telescope a million miles from earth, with 5 sheets of insulating plastic between it and the primary IR source in our solar system, the Sun. Everything about the Webb telescope is there to help it see into that one blind spot that we still have. Things, for example, like the size of its mirrors.

Dr. Rolf Danner: So, you will see pictures just about as good and as finely, as in as much detail as, you see from Hubble, just in infrared, and you can do this because the mirror is so much larger.

Hank Green: The heat shields.

Dr. Rolf Danner: Almost 600 degrees, right, from one side to the other, 600 degrees Fahrenheit. 1.2 million SPF I think.

Hank Green: The location of the telescope.

Dr. Amber Straughn: Infrared light is a lot like heat radiation, so the whole thing has to be very, very cold. That's why we're putting it out in deep space.

Hank Green: And the mirror's gold coating.

Dr. Rolf Danner: On the wavelengths of interest, gold is better at reflecting infrared wavelengths.

Hank Green: So the question remains, "What will the Webb be able to show us?"

Dr. Amber Straughn: You can tell things like what kind of chemicals are in atmospheres of exoplanets, for example. Or you can tell what molecules are in a certain galaxy, or all these different things you can tell how stars are forming, how many stars are forming.

Hank Green: All of that, and the very beginning of the universe too. In 2018, when the Webb deploys, all will be revealed, and the next chapter will begin.

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