Planetary Radio: Space Exploration, Astronomy and Science - Einstein and Gravity Probe B

Episode Date: May 23, 2011

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Proving Einstein was right about space in space, this week on Planetary Radio. Welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. After more than 50 years of development and data gathering, a spacecraft called Gravity Probe B has demonstrated that Einstein was right about the nature of space and gravity. It's a wonderful story of science and engineering at the edge of their capabilities, and we'll hear about it from Principal Investigator Francis Everett. Bill Nye usually takes us soaring among the stars. This time his commentary will put us

under the waves. Bruce Betts got quite a shock when he actually met the answer to the space trivia contest question. We'll share his surprise when we get to our What's Up segment. As I record this, Space Shuttle Endeavour is docked with the International Space Station and will make its final return to Earth in a few days. Big personal news comes from Emily Lakdawalla this week. Apparently we're not the only ones who love her Planetary Society blog entries. Emily, it has been a big week. We're going to talk about the time that you spent last week at the meeting to decide where Curiosity, the Mars Science Laboratory, may be landing on Mars.

But there was another event of some significance in your life. Congratulations. Thank you very much. I got a very exciting phone call from Melissa McGrath on the DPS Prize Committee, the DPS, of course, being the Division of Planetary Sciences of the American Astronomical Society. And every year at their annual meeting, they give out five prizes for various contributions to planetary science. And this year, I have won the Eberhard Prize for Excellence in Planetary Science Journalism.

So they're flying me to their annual meeting in October, which happens to be in France this year. So I am really thrilled. I'm honored, of course, to receive the prize, but thrilled that I'm getting a free trip to France to go accept it. You're going to be going with another Planetary Society colleague. That's right. Jim Bell is another recipient of an award this year for his contribution to public excitement about planetary exploration. Of course, for his generosity with the Mars Exploration Rover images, which stimulated the development of the crowded unmanned spaceflight that I'm so involved with,

that makes all of those wonderful amateur processed images of Mars and other planets in the solar system. And Jim Bell, of course, the president of the Planetary Society, so they must be proud as peacocks down at the office. Absolutely. Listen, before we run out of time, how about MSL? Do we know where it's going to set down? Well, this meeting that I attended this week was never going to decide exactly where MSL was going to land. Actually, I should call it the Curiosity rover was going to land. This is just an advisory body, a bunch of scientists getting

together to argue out what they think the best site is. But you get 150 scientists in a room, you're going to get 151 different opinions. So they weren't going to decide. But I think the most exciting thing that came out of this meeting is that there are no engineering restrictions on any of these four landing sites. We could go to any one of the four. The mission would be quite different at each of the four sites. And it's really not clear which one would be the best for Curiosity. So it's gotten punted back to the mission, and they're going to have to make a decision and send it up to headquarters. We should find out in June where MAMAS they're going to have to make a decision and send it up to headquarters.

We should find out in June where MAMASAL is going to land. Now, I read your entry of May 18th, and I got to say, doesn't the confidence that these folks are expressing in the survivability of this rover, isn't it making you a little bit nervous? It's not making me nervous. It's just making me confused because usually it's the engineers who are saying, no, no, don't go there. It's dangerous. It's unsafe. You need to protect the rover. Do everything you can to land it on the most boring, flattest possible landing site. And this time it's the scientists who are saying, no, don't risk the rover. It's so scary to go to a site that has any craters in it. Whereas engineers are saying, drive, baby, drive. We're going to go to the roughest, toughest landing site we can. We've built a great machine that could land anywhere on Mars,

pick and choose. So it was just bizarre, actually, to watch those conversations go back and forth. It is so opposite to what normally happens. Emily, you're going to be on the road the next few weeks. We will try to check in with you when we can. But just one more time, congratulations for a very well-deserved honor. Thank you very much. And thanks to all of the people who've been writing in such kind emails to me today. Emily Lakdawalla is the Science and Technology Coordinator for the Planetary Society. She's also a contributing editor to Sky and Telescope magazine and the just announced recipient of the Jonathan Eberhardt Planetary Sciences Journalism Award. Here's another award-winning guy, Bill Nye.

Hey, hey, Bill Nye the Planetary Guy. And this week for me, the news in space is in the ocean. We're going to launch the Aquarius satellite with its instrument that will study the salt in the sea. And the salt in the sea reveals to us the currents. Because currents are driven by salt and heat and spin of the sea. And the salt in the sea reveals to us the currents, because currents are driven by salt and heat and spin of the earth. And these are what people call thermohaline currents, salt-heat currents. And by understanding them, we can understand how water moves all over the world. Water moves in these enormous masses along the seafloor and emerges at the poles. And it wasn't very well understood until pretty recently in science. And so now, along with measuring rainfall and the cloud cover and

where freshwater rain falls and where storms develop in the Gulf of Mexico and other places where there's a lot of heat, now we can measure the salt and see where the water sinks again after it's risen up from the deep. Along with this, we're going to use the ocean to learn how to live in space. The NEMO, the NASA Extreme Environment Missions Operations Expedition, is going to go underwater in October or so, and these astronauts or aquanauts are going to learn to live and work underwater in preparation for a mission to an asteroid. Now, when you go to an asteroid, you don't really need a lander. You're kind of floating around.

And so it is working under the sea. The astronauts will learn to work with the same equipment or equipment designed in a similar fashion as they learn to work with on asteroids, which is on the way to Mars. If we can get humans on Mars, we will make discoveries that are literally hard to imagine. It's an exciting time for space in the ocean. I gotta fly. Bill Nye the Planetary Guy. Gravity Probe B got its theoretical start back in 1959. That's when it was first realized that Einstein's general theory of relativity could be tested by a gyroscope, so long as that gyroscope was in space

and was exquisitely sensitive, far more sensitive than any previous device of its kind. Francis Everett was then a young physicist. More than 50 years later, Francis remains a research professor at Stanford University in Palo Alto, California. He and others could not have known that it would take five decades to fund, design, build, and fly the amazing machine that would finally deliver its triumphant findings just a few weeks ago. I came to Stanford in the year 1962, before NASA started funding it, thinking I would stay at Stanford for two or three years.

And I have stayed somewhat longer than that. In fact, more than a third of the history of the university. And you've been the principal investigator for 30 years. Something like that, yes. That's quite a run. What was it that those scientists, your predecessors, wanted to do when they proposed putting this device in space? There are two ways one needs to think about this. One needs to think about Einstein's theory to know how difficult it has been to test.

And one needs to recall that in 1959-60, it was just two, three years after the Sputnik. And so space was opening up and people were asking questions. Can one do something in space that wasn't possible before? So Gravity Probe B is a test of Einstein's general theory of relativity. That's his theory of gravity, and I can say more about that, which requires space to do it in. Alternatively, you could say space makes it possible where it would be completely impossible on the ground.

So the idea of the experiment is to put a gyroscope. This gyroscope is a spinning sphere the size of a ping-pong ball, very, very homogeneous quartz sphere coated with metal, put it in orbit around the Earth, point it at a star, and ask what happens. Here we need to know a little bit about Einstein's theories. Everybody has heard that Einstein did something about relativity and isn't E equals MC squared something to do with that? Yes, that's

true. That's Einstein's special theory of relativity dated from 1905, where he was dealing with the problem of objects moving very close to the speed of light, where you have to modify Newtonian mechanics. Fine. When he had completed that theory, he began thinking about whether you need to modify Newton's theory of gravity. And it took him 11 years to think of the theory to do that. Now the great contrast between these two theories and their experimental status is special relativity is extremely well tested quantitatively exactly. You can worry about the philosophical meanings of what it says about space and time, but if you look at the equations without thinking about this and take the sort of hard-headed, does it work?

The theory works fantastically well. His theory of gravity is very, very different. In 1960, Leonard Schiff pointed out that there were supposedly three tests of this theory, but only one of them actually really tested the fundamentals of the theory, and that these were not very accurate. George Pugh thought of the idea of a gyroscope experiment in space a month or two before Schiff, completely independent. So then we came, and William Fairbank brought me to Stanford University to start thinking about this, actually before it was funded by NASA.

And then we put together a proposal to NASA, and that's the start of the story. But you need to understand that you need to make a gyroscope that is at least a million times better than the best earth-based gyroscopes. And when you think of all the billions of dollars that have been spent on developing inertial navigation gyroscopes since World War II, at first it seems ridiculous to think that one can do anything new. The reason why one can do something new is you have a very different environment of space instead of something in the submarine or something in a missile. And that's what Gravity Probe B was all about. But in order to develop it, we had to invent

something like 12 or 13 new technologies, new ways of making spheres, new ways of measuring how homogeneous spheres were, how uniform they were, and so on and so on. That was why it has taken time to develop this experiment, which was finally launched April the 20th, 2004, at 9.57 and 24 seconds in the morning. This itself is a very interesting thing, because about a minute after that, you look up into the sky and see your apparatus disappearing,

and you begin to wonder about all the things you might have done more differently, although you'll never be closer than 400 miles to it again. So that was what Gravity Probe B was. Actually, it worked amazingly well. One of the things that people said to me before we launched was the following. You will find all the things you thought would probably go wrong will go perfectly better than you expected, but there will be one or two other things which you didn't expect anything to be difficult, but there will be one or two other things which you didn't expect anything to be difficult, and those will be the nightmares you face.

Einstein's theory describes gravity in terms of curving space-time. This sounds very mystical, and I want to make it less mystical than it sounds, because really it's not so difficult to get a feel for it. So imagine in empty space drawing a circle, and the circumference of the circle is 2 pi times the radius, something we all learned in high school, all of you of poor high school, and probably remember. And now imagine that circle to have a 4,000 miles radius,

that's the radius of the Earth, and slide the Earth inside the circle. Well, according to Einstein, but not according to Newton, the circumference of the circle, if you could measure it, would be a little bit less than 2 pi times the radius, and that's what one means by curved space. So you ask, how much less? Well, the circumference of the Earth is to 25,000 miles,

and the Einstein difference is 1.1 inches. This is a result we have checked, not quite directly, but very closely indirectly, by the change in direction of spin of a gyroscope in the plane of the orbit of the satellite, which goes over the poles and we have measured it to just over a quarter of a percent so you can say that's like equivalent to measuring that to three thousandths of an inch 25 000 miles so that's one of the ways

you can get a feeling of the challenge that this experiment involved we'll hear more from gravity probe b principal investigator francis everett when planetary radio continues you can get a feeling of the challenge that this experiment involved. We'll hear more from Gravity Probe B Principal Investigator Francis Everett when Planetary Radio continues. I'm Sally Ride. After becoming the first American woman in space, I dedicated myself to supporting space exploration and the education and inspiration of our youth. That's why I formed Sally Ride Science,

and that's why I support the Planetary Society. The Society works with space agencies around the world and gets people directly involved with real space missions. It takes a lot to create exciting projects like the first solar sail, informative publications like an award-winning magazine, and many other outreach efforts like this radio show. Help make space exploration and inspiration happen. Here's how you can join us.

You can learn more about the Planetary Society at our website, planetary.org slash radio, or by calling 1-800-9-WORLDS. Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio t-shirt. Members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Francis Everett has told us that Einstein's special theory of relativity

has been proven and utilized many times over, but the challenge of proving his general theory was much more daunting. Doing so with a spacecraft called Gravity Probe B has occupied the Stanford University professor for nearly 50 years. He has been the project's principal investigator for the last 30. Francis has already told us how their experiment has measured the curvature of space-time. But there was a second prediction made by Einstein that would be even harder to observe. Even more fascinating to me is this concept of frame-dragging, which your experiment also found evidence for. Right. What Einstein's theory says is that as the Earth, it drags space and time around with it. This also sounds mysterious.

The way to think about it is imagine the Earth to be immersed in honey and have, say, a straw in the honey. Then as the Earth rotates, the honey would be dragged around with it, and so would the straw. And that analogy is surprisingly good when you look at the mathematics of it. All sort of a little odd. One has heard that Einstein says, well, he abolished something called the ether,

and I've just given you an ether picture of brain-bagging. But it's a very good picture, and it's a reliable picture. It makes sense. And that effect, which is 150 times smaller than the first one, we've measured to slightly better than 20%. So, as I said, Einstein vindicated once again. Once again, but the once again has to be said out of a surprisingly small number of vindications.

The beauty, in my view, of the experiment is not only that it does this, but it does this in a fundamentally new way because it's a controlled physics experiment where we have not one gyroscope, we have four separate gyroscopes, each metering both effects, and they end up all agreeing with each other. So it's a very compelling test. Could you say a word about the technologies that you had to, you and your team had to come up with over the years to make this experiment work? Let me start by saying that we had to make spheres that were rounder than any previous sphere. So the sphere, in the end, was so round that if you expand it to the size of the Earth proportionally, the highest mountain would be about nine feet. You also had to have it very uniform.

And now you have it supported electrically and you have to spin it up. We spun it up by means of gas. Then you ask yourself the very curious question, how do I measure the direction of spin of a perfectly round, perfectly uniform sphere which has no marks on it? And this is where the properties of superconductivity come into play. Some metals at very low temperatures, this was discovered exactly 100 years ago this year, lose their electrical resistance when you cool them to low temperatures, a few degrees above the absolute zero. resistance when you cool them to low temperatures, a few degrees above the absolute zero. That's nice and very remarkable, astonishing, but we have our sphere of glass as it is,

the size of a ping-pong ball, coated with a thin layer of a superconducting metal. When we spin it, it becomes a little magnet, and the magnetic moment, or the magnet, is aligned with the instantaneous spin direction, so although it's perfectly round and perfectly uniform, you end up with a magnetic pointer in it, and that's called the London moment, because Fritz London was the first person who deeply investigated it. This is how you measure the direction of a perfectly round, perfectly uniform sphere with no marks on it. And we came up fairly early with the idea about how to do this. Actually reducing it to practice and getting this tiny magnetic moment accurately measured so that we could measure one thousandth

of an arc second angle in 10 hours, that was the problem. And let me tell you what 1,000th of an arc second is. It's the width of a human hair, actually one of my hairs, seen at a distance of 10 miles. And that's the tiny angle that we're measuring. That worked, and it really worked as predicted. In fact, it worked a little bit better than predicted on orbit. This was one of the cases

where people said your findings may work better on orbit than you were expecting. As in so many things in life, it's totally non-obvious until you see it, and then you can't understand why it took you so long to understand. We had three things that didn't quite work, which we had to fit together. And then when we'd done that, it was amazing. All the gyroscopes beautifully agreed. I find this to be a gloriously inspiring instance of achievement by humanity and very much in line with the great achievement that is the basis of all of this, and that was Einstein's achievement.

Do you feel any kinship with that great mind, having helped to show that he was on the right track? I do feel a certain kinship. Of course, it only took him 11 years to think up a new theory of gravity. It then took another 50 years before people could really think of a new test, and then it took us another 50 years to do it. So maybe Einstein was a little quicker off the mark than we were, but it still took him 11 years.

It has been a great pleasure speaking with you, and I do want to congratulate you on this very recently announced, anyway, achievement that really, I guess, is the crowning glory after over 50 years of effort in this project. We are delighted to have you take an interest in it. Thank you. Thank you, Francis. Dr. Francis Effert is a research professor at Stanford University's W.W. Hansen Experimental Physics Lab, and he is the principal investigator. He has been for over 30 years and has been involved with the Gravity Probe B project for much longer than that.

We will be right back with our friend Bruce Betts for a look at the night sky, the night sky that still has a Gravity Probe B in it, in just a few moments. Got Bruce Betts on the Sky Connection. He's going to tell us all about the night sky and most of the other stuff we usually do. We're going to bring you What's Up. Welcome back. Why, thank you. It's good to be back.

We've got good stuff. That pre-dawn, still four planets there. Go check it out. A half hour before sunrise or so, we've got Jupiter getting higher and easier to see, super bright. To lower left of Jupiter, there's a cluster of Venus, even brighter, and Mercury dimmer, and Mars dimmest and looking kind of reddish. And if you check out the gang, it's very low on the horizon, but if you check them out on the 29th or the 28th, you will see the crescent moon hanging out in the group as well. And it's quite the sight. Go hanging out in the group as well. And it's quite the sight.

Go see it, Matt. Nice times. Yeah, I think I might even get up and do that. And still got Saturn hanging out in the evening sky, high in the east in the early evening. We move on to this week in space history. We had Scott Carpenter, Aurora 7, and the Mercury program in 1962. We also had the first primates in space,

who I believe were named Matt and Bruce. No, no, that was actually Bing Crosby and Bob Hope. Well, there certainly is movie evidence of that. But Abel and Baker are ringing some bells as well. I'm thoroughly confused now. All I know is that there were definitely lots of bananas involved. I know it had a lot of appeal. Yeah. So anyway, the risk of more puns. Let us move on to Random Space Fact.

Oh, an entirely falsetto version. I don't know if we've had one of those before. It was tender and sensitive, didn't you think? You were getting in touch with your feminine side. Hey, hey, stop saying that. All right, okay. Bruce is much more Mars than Venus. We just want everybody to know that right now. In so many ways. Anyway, on to the random space fact, which is that helium was actually first discovered through observations in 1868 of the sun. Observations of the solar eclipse, both Joseph Lockyer and Pierre Janssen independently observed something in the spectrum that they didn't know what it was. It turned out to be helium, so it was sort of discovered. It wasn't discovered on Earth until 1895.

I had no idea. That is absolutely amazing to me, but I suppose it has everything to do with, you know, this non-reactivity, right? What's the word for something like that? That'd be inert. Inert, yes. Or a noble gas. It's so inert it doesn't mess with things. I'm still perplexed why people didn't wonder what was in the birthday balloons. Well, let's just say that it wasn't wise to light the candles at birthday parties in those days.

So back then, helium burned. Oh, the humanity, the humanity. Let us move on to the trivia contest before, and I have a lovely story for you. Some people may have read this in my blogs from the Planetary Defense Conference, but for the first time in all these years, I had something new happen having to do with the trivia contest. I actually met the answer the day after I asked the question. Oh, my gosh.

So we recorded when I was in Romania on Sunday night for the Planetary Defense Conference. I thought, well, I'd be thematic and ask who the first Romanian person in space was. Little did I know that the next day at lunch, I would sit down next to Rusty Schweikart, the Apollo astronaut, who I know. And about halfway through the meal, I realized sitting next to Rusty was the answer to the trivia question. The first Romanian in space, he now heads the Romanian Space Agency. I chose not to tell him he was the answer to our trivia contest. I first Romanian space, he now heads the Romanian Space Agency. I chose not to tell him. He was the answer to our trivia contest.

I thought it might be offensive. Oh, what a shame. He could have won a T-shirt. Well, and I'm sure he would consider it among his top honors ever. I'm sure it outdoes what happened later in the week.

They had a ceremony where they released a new postage stamp honoring him the 30th anniversary of his flight, which was 30 years ago that week. And David Kaplan, no relation, actually sent us an image of that new Romanian stamp. Wow. We should probably say who we're talking about here, that it was Dimitru Prunariu. And I hope he's not listening because I'm sure I got that wrong and that's actually exactly how he said his name seriously well sometimes I get lucky I guess I could tell you that that answer came from a whole bunch of

people we had a huge response I mean maybe one of the biggest we've ever had. Don't ask me why. But it was Marcin Ziga from Wrocław, Poland. She has been entering for weeks and weeks and weeks now, but she is a first time winner. She did give us that name. It was Dumitru. I do want to tell you that Torsten Zimmer had it right. But he said, you know, that's a good question. But the really good question would have been who was the first Romulan in space? I'm just not equipped to answer that. I don't know that anybody is. Although that would have been even stranger if I had asked that and then met the answer the next day. Well, anyway, Marcin, we're going to send you a Planetary Radio T-shirt. And the other news, folks, is no new trivia contest this week. I know, it's sad,

but it's because of Planetary Radio Live, which will air in a couple of weeks. The first part, because it'll be in two parts, will air during the week of June 6th, and we're going to do a live trivia competition then, and it just doesn't work out well for us to do one.

So you get a week off, and there will be a brand new trivia question next week. All right. Planetary Radio Live. Yeah, it's going to be great fun. And we have a sold-out house. It is absolutely going to be a blast. All right, everybody, go out there, look up at the night sky, and think what kind of gas you'd put in your birthday balloons. Thank you, and good night.

You know, it's not so much the question of the gas for me. I've never been able to tie a knot in a balloon, so all that gas is going to come out if you hand that balloon to me. He's Bruce Betts, the director of projects for the Planetary Society. He joins us every week here for What's Up. Next week, we'll check out the weather on Mars. Planetary Radio is produced by the Planetary Society in Pasadena, California and made possible in part by a grant from the Kenneth T. and Eileen L. Norris Foundation.

Clear skies and Godspeed endeavor. Thank you.