Date: February 23, 2012
Title: Bill Nye Visits Arecibo
Podcaster: Mat Kaplan
Organization: Planetary Society
Links: National Astronomy and Ionosphere Center (Arecibo Observatory): http://www.naic.edu/
The Planetary Society: http://planetary.org
Description: Bill Nye the Science (and Planetary) Guy is now the Chief Executive Officer of the Planetary Society. A recent trip took him to Puerto Rico for a somewhat precarious tour of the great Arecibo Observatory, by far the largest single dish radio telescope on our planet. He reflects on his visit and explains why he admires the audacity of supremely ambitious human undertakings on behalf of science.
Bio: Mat Kaplan is the Planetary Society’s Media Producer. He has also hosted and produced Planetary Radio, the Society’s award-winning weekly podcast and public radio series about space exploration and development, for nine years. The show presents the men and women who are leading our push into the final frontier, along with regular contributions from Bruce Betts, Emily Lakdawalla, and Planetary Society CEO Bill Nye the Science Guy. Catch it on a local radio station, Sirius XM Satellite Radio, in the iTunes Store, or at http://planetary.org/radio . With this return to 365 Days, Mat and the Society kickoff a monthly contribution on the last Thursday of each month in 2012. (With the exception of August, when it will be heard on Thursday the 23rd.)
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Transcript:
MAT:
Hello again, astronomy fans. Mat Kaplan here from the Planetary Society. I host and produce our weekly radio show, Planetary Radio, that you can find at planetary.org. But at the moment, we have brand new and original content for you on today’s edition of 365 Days of Astronomy. Sitting across from me is the CEO of the Planetary Society, who you know. You do know him—as Bill Nye the Science Guy. Hi, Bill.
BILL: Hi, Mat! Great to see you, great to be here.
MAT: We’re gonna talk about a trip you took recently to the world’s biggest…
BILL: Anything!
MAT: Dish!
BILL: Oh, it’s crazy! Arecibo. Radio telescope in Puerto Rico. Everybody, it is amazing. What I can’t get over, Mat, is the audacity of the thing. The scientific paper was written in 1958. The thing was built in 1963. It’s been upgraded and upgraded many times since then. But, everybody, I don’t know if you’re familiar with this. You see it in the movie Contact. They took a sinkhole in Puerto Rico, which is largely limestone. You can walk around and see seashells embedded in the rock, the white rock. So underground caves form with underground streams, and the whole thing collapsed many, many centuries ago. And people built a radio dish a 1,000 feet across—305 meters across. It has all these crazy little screws and nuts—adjuster things on the corners of these aluminum panels–and they can make it round to plus or minus 1.5 millimeters, about a 1/16 of an inch. I bet originally it was 1/16 of an inch in the old English system, yes!
Then they’ve got this receiver hanging on cables, like a suspension bridge over this valley, this huge thing! If you want to think about how you design reflectors, if it’s a parabola, you may recall, the parabola is the locus of points equidistant from a line or in the case of a parabaloid, a plane and a point. But this is a sphere, that is to say, a portion of a sphere. So the focus is not a single point. The focus is a line, and this is geometry. It’s kinda cool.
So the antenna, the receiver is this big stick—25 meters long. Then there’s another one that is this air conditioned half dome hanging off the ground on these cables that they adjust, eeee-eeee-eee, just perfectly so that as the temperature changes it’s still in focus.
MAT: You can actually walk out to that receiver, right?
BILL: Oh, God! It’s crazy. There’s this catwalk, goes out over the valley. I mean, you watch your life pass before your eyes. And down below you is nothing’ but aluminum, perforated aluminum. It’s just like the screen in your microwave oven door. Even though it has holes in it which let optical wavelengths through—visible light—radio waves bounce right off it, microwaves bounce right off it completely. The people who describe it and sit there and tell you all about it, they all talk about the light–the light from space bounces off this reflector up into the secondary receiver. ( If there’s an “r” in the month…but it’s complicated, is all I mean.)
Actually, it’s simple in a way. “We’re gonna build a great big bowl, and reflect radio waves into an antenna.” Really, I wouldn’t have expressed it in this way. If I had been there in 1963, I might have said something like, “Are you high?” Like, that is crazy! That is just a crazy idea.
The towers! They built the whole thing out of cement, and the cement is made from limestone. When they were excavating this sink hole valley thing there was no shortage of limestone! They just ground up the local rock and created concrete towers to suspend this thing—and the buildings and support structures and so on.
MAT: You also heard about some of these improvements that they’ve made over the years, right? Those are not the same electronics that were installed in the early ‘60s.
BILL: Exactly! Yeah, you go to the old area—it’s all in one room, but the old area, the consoles are maybe, uh, 10 meters, they’re 30 feet long, and taller than I am. I mean I’m 183 centimetes—6 feet tall. So they’re 7 feet tall and thirty feet long of electronics. That’s all been replaced now with about 2 laptops, cause there’s redundancy, you know. And there’s this cool diagram that shows you the configuration of the receiver right now, at the current time while you’re operating it.
The thing that hangs over the valley has two features. First of all, it’s a big arc so that the receiver moves through an arc and maintains the same distance from the dish all the time. The dish is an arc, so it’s an arc. Then it pivots like the turret on a tank or big steam shovel style piece of construction equipment.
MAT: Some major ball bearings.
BILL: MAJOR ball bearings. The thing has been up there, hanging in the sky, for fifty years! To me, it’s really an amazing deal. It’s audacious.
MAT: It is a great piece of engineering. And I think “audacity” is the right word for it.
BILL: It’s not just…the engineering’s great. And I’m an engineer. I’m kooky for engineering. The science! The astronomy! “What we need is somethin’ this big!”
It may interest us to know that the scientific paper they have on display in the lobby, “look at the scientific paper” area, is from 1958. It talks about exploring the ionosphere. And in the acronym for Aercibo the ionosphere is still in there. But I cannot help but wonder–as a guy who grew at a time when people really did build fallout shelters and I visited Nike missile bases—I can’t help but wonder if somebody didn’t have a cold war application for this thing. That you could listen for the electromagnetic pulse of a nuclear weapon or something in the ionosphere, or something like that. It wouldn’t surprise me.
There’s another thing to it. Unlike your home radio telescope that you’ve, no doubt, built in your backyard. (I’m kidding.) There’s another feature to it. It can broadcast microwaves. It can beam them. In your microwave oven you have a device which has come to be called a klystron—there were some competitive names for awhile—but this is the thing that takes radio frequency signals and amplifies them into microwaves themselves in what’s called a waveguide. (Wow, that’s pretty creative. It’s a guide for waves.) But the thing about a waveguide, everybody, it has to be precisely made. The dimensions of the cavity, the metal cavity—it’s almost always metal, it has to be reflective of radio waves—it is precisely shaped so that the waves will amplify. Your microwave oven might be 500 watts, 600 watts. This thing’s a megawatt. It can broadcast a million watts of radio signal into space, bounce it off the planet Saturn—you have to wait while the Earth turns a couple of hours—and then the signal comes back. It’s an amazing thing.
It may help us discover asteroids that could potentially kill us all. So it’s a vital piece of equipment, and we have to maintain it. If you ever get a chance to visit it, Arecibo, Puerto Rico, it really is a spectacular thing.
MAT: Bill, thank you for this little audio tour of the world’s biggest single-dish radio telescope.
BILL: Thank you, Mat.
MAT: Bill Nye is the CEO of the Planetary Society. You can read much more from him and hear much more from him, along all the other projects that we’re up to, at planetary.org. For 365 Days of Astronomy, the podcast, this has been Mat Kaplan.
End of podcast:
365 Days of Astronomy
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