For Planet-Seekers, a Cautionary Tale

17:22 minutes

Last week, Caltech astronomers Michael Brown and Konstantin Batygin made big news with their prediction of a ninth planet, beyond Neptune. The pair hadn’t spotted “Planet Nine” at the end of a telescope. Instead, they’d conjured it with mathematics—not a new technique in the annals of astronomy. In 1846, French mathematical astronomer Urbain-Jean-Joseph Le Verrier was said to have discovered Neptune “at the tip of his pen” (as a colleague put it). He used Newtonian physics to predict the exact location of our eighth planet, before ever observing it. Just a few decades later, he repeated the feat, “discovering” the planet Vulcan the same way. Except Vulcan didn’t exist.

In his book, The Hunt for Vulcan…And How Albert Einstein Destroyed a Planet, Discovered Relativity, and Deciphered the Universe, Thomas Levenson tells the cautionary tale of Vulcan’s discovery and destruction at the hands of Einstein and relativity. He joins Ira to talk about what lessons Vulcan may hold for today’s planet-hunters.

Segment Guests

Thomas Levenson

Thomas Levenson is author of The Hunt for Vulcan…And How Albert Einstein Destroyed a Planet, Discovered Relativity, and Deciphered the Universe (Random House, 2015) and a Professor of Science Writing at the Massachusetts Institute of Technology in Cambridge, Massachusetts,

Heard on the Air

Read an excerpt: Discovering Planet Vulcan

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow.

Last week astronomers Mike Brown and Konstantin Batygin came on the show to share an exciting prediction, a ninth planet orbiting beyond Neptune. It wasn’t Pluto either. Brown and Batygin has actually not seen the so-called Planet Nine. But they had detected its gravitational effects way out there in the solar system.

I asked Mike Brown how confident he was that Planet Nine exists.

MIKE BROWN: We believe it. We believe enough that we’re willing to write a paper and stand up and say, yes for the past century, everybody who said there was a Planet X is crazy and they were all wrong. But we’re right.

IRA FLATOW: It takes some chutzpah to predict a planet, because as Mike says, the history of astronomy is littered with planets that could have been contenders. And we’re not just talking about Planet X. Among these many cautionary tales, one stands out, and that is the planet Vulcan.

My next guest tells the story of Vulcan, its so-called discovery and demise, in his book The Hunt for Vulcan: How Albert Einstein Destroyed a Planet, Discovered Relativity, and Deciphered the Universe. Thomas Levenson is Professor of Science Writing at MIT. He joins us today from Cambridge. Always good to talk to you, Tom.

TOM LEVENSON: It’s great to talk to you again, Ira.

IRA FLATOW: Thank you. So let’s talk about the planet Vulcan. So is Mike Brown right to be a little bit cautious?

TOM LEVENSON: He is. I’m terribly excited by the news of a possible Planet Nine. And the story holds together perfectly. I actually had the chance to speak to Konstantin last week as well. And he told me they tried to do everything they could to rule out the planet before they finally succumbed to its necessity. And those are two very good scientists. And I really hope they’re right. And if I were a betting man, I’d bet at least lunch money that they are.

IRA FLATOW: All right. You’re buying.

TOM LEVENSON: Yeah. Exactly. But you know, nature has many more ways to fool us than we have ways to figure things out. And that’s still true even this far into the several hundred year exercise of modern science.

IRA FLATOW: Well, let’s talk about your book. Let’s talk about The Hunt for Vulcan. How did Vulcan become part of our solar system in the first place?

TOM LEVENSON: Vulcan became a plant that was actually listed in the planetary guides in some places for very good reasons. The way you find something that you can’t see is you look for its influence on things that you can see. That’s how Brown and Batygin think they have pointed towards Planet Nine.

And that’s how we discovered Neptune, when a man named Le Verrier, a great French mathematical astronomer– Urbain Jean Joseph Le Verrier, very great name– calculated all the gravitational influences on the planet Uranus, saw that there was a residue of unexplained motion, and was able to predict where Neptune could be seen. And within two or three hours of turning their telescope at the point he had predicted, two astronomers in Berlin found it.

Perfect sort of test case for the idea that Isaac Newton’s theory of gravity really does hold throughout the solar system. And when you see gravitational influences on something you can’t explain, that tells you, you got to go look for what’s out there.

IRA FLATOW: Was Neptune the first time a planet was discovered in the math, in that way?

TOM LEVENSON: Yeah. It was said at the time that Le Verrier discovered Neptune at the tip of his pen. And it was almost a romantic moment. It was this great kind of rhetorical persuasive triumph of the Newtonian world view of the power of modern science. It was a big, big deal in the 19th century.

IRA FLATOW: So he invented Vulcan?

TOM LEVENSON: Yeah, exactly. And he did it the same way he discovered Neptune. He analyzed the orbit of Mercury. He found what’s really there. The effect he found is real, which was a slight wobble in Mercury’s orbit.

The point on the orbit nearest the sun that Mercury passes each year, moves around the Sun over the centuries. And it does so by an amount that’s influenced by Venus and by Earth and by Jupiter and so forth. But it does so by a little bit more than could be explained by those planets.

So as with Neptune so close in memory it was obvious what the explanation had to be, right?

IRA FLATOW: Right. So even though it didn’t exist, you write in your book, a lot of people claim to have spotted it. Say hey, there’s Vulcan.

TOM LEVENSON: Yeah. I mean, again, everything made sense, right? Newton’s theory had worked in every application. Everybody knew if Le Verrier said that was in the math, he was that good, it was in the math. And in fact, it is. The affect that he documented is slightly larger than he did at the time. But he got it right.

And the only plausible explanation, given what was known at the time, was there had to be this planet inside the orbit of Mercury, that they almost immediately named Vulcan because with all that necessity, sort of this moral right of Vulcan to exist, people started– the first person was a country doctor who saw this little round spot, perfectly round spot, across the face of the sun. He said, gotta be Vulcan. And people said, OK that’s Vulcan. Were done.

And it just snowballed from there. People found things that they persuaded themselves were this planet. And it didn’t seem to bother them that nobody could repeat the observation.

IRA FLATOW: You got to be able to do that in science. And then the guy who finally puts the stake in the heart of Vulcan is, of course, Albert Einstein. How did he do that?

TOM LEVENSON: Well, the really interesting thing is there’s a gap. So Le Verrier publishes his prediction that Vulcan has to exist in 1859. And for the next 20 years, there are at least a dozen reputable sightings of this thing.

And finally, in 1878, there’s an eclipse who’s track goes across the United States and a whole bunch of astronomers look for it with the best instruments they could find. And one guy reports seeing it and everybody else says no.

And at that point, the astronomical community just says, we’re done. There’s no Vulcan. We understand the dynamic of desire and the hope for it to be and the expectation for it to be there, but it ain’t there. And you remember what we were all taught in high school, right? In science, a single brute fact is powerful enough to overturn the most beautiful theory, right? Remember that, something like that?

IRA FLATOW: You sort of hate a fact that gets in the way of a good theory.

TOM LEVENSON: Exactly. But at this point, you have an important fact that’s getting in the way of Isaac Newton’s theory. Vulcan should be there to explain what has been reconfirmed and reconfirmed, really is happening with Mercury. Vulcan’s not there. What gives?

And there were a few attempts to do these hand waving explanations. Maybe the sun’s fat around the middle and that gives some extra mass. Maybe there’s a disk of dust we haven’t seen before and that’s the mass. Of all these things were tried, and they didn’t work out.

But for the most part, for another 30 years, Vulcan and Mercury’s sort of wobbling orbit were like the crazy uncle in the attic, hooting up in the distance. And if you were polite, you just didn’t notice that there was this noise coming down from up above. And that was sort of what happened with Vulcan in the sciences. There was a problem with Mercury, but people didn’t see it as serious or something they really had to pursue.

And finally, along comes this patent clerk. He’s still a patent clerk when he gets started on this problem, Albert Einstein. And he starts working on a different problem, not the problem of explaining Mercury’s orbit, but the problem of reconciling Newton’s whole theory of motion, with his then special theory of relativity that says things that there is actually a contradiction.

I mean, for example, Newton says, things can happen instantaneously, right? The gravity from the Sun reaches the Earth in an instant whereas in Einstein’s special relativity, nothing goes fast in the speed of light. So there’s eight minutes of light travel time between the sun and the. Earth and that’s how fast any influence can pass between them.

So Einstein hated contradictions. And he started working on it. And it took him eight years. But finally, in the middle of wartime Berlin, working on his own, scribbling away calculation after calculation, he comes up with the fully formed theory of general relativity, which is a really, truly weird idea, right?

It says that gravity isn’t a force. It doesn’t tug on you like this sort of imagined, sort of mechanical, connection. It’s actually something that is a property of the shape of space and time. And big masses deform space and time more. Big mass, like the Sun, creates a big dent in space time. And that helps explain how things move around the sun and throughout the universe.

And that was his big conception. And the test was when he tried to apply it to a real world problem. And the first real world problem he applied it to was the problem of Mercury. And he found that if you worked through the idea of curved space time near the great mass of the Sun, Mercury’s orbit behaved exactly as Le Verrier said it did, but perfectly naturally.

It was just rolling down the shortest path it could travel in curved space time. You didn’t need another planet. You didn’t need some mysterious effect on the sun. You didn’t need to play with the fundamental constants of nature. That’s just the way it was. And it was a revelation.

IRA FLATOW: So he didn’t set out to disapprove Vulcan, it just stemmed naturally from his ideas about Mercury.

TOM LEVENSON: Exactly. I got into this whole story actually because of Einstein. I was doing a different piece of work on Einstein more than a decade ago. And I came across references in his letter to his extreme joy when he got the Mercury result right. He said he had palpitations in his chest. His heart leap in his chest. He was beside himself with joy. He couldn’t work for days.

And you’ve been around this business long enough to know, that’s not the usual picture of Einstein. He’s not this wild emotional type, right? And at the time, I wondered what was it about this one? Because it seemed like fixing a minor problem in solar system dynamics, why was that such a big deal for him?

And it was in answering that question, finally getting back to that question, that I came across the story of Vulcan and realized why it was such a big deal. It’s a big deal, because it showed that his conception of how the universe fits together, radically different from the one it was replacing, Isaac Newton’s theory of gravity as instantaneous action at a distance, pretty much had to be correct.

He was convinced he nailed it, once he got the orbit of Mercury right, even though that’s far from what he set out to do. And the rest of the world would catch up with him when the Eclipse Expedition of 1919 measured the bending of starlight around the Sun, as his theory predicted. But already in the late autumn of 1915, Einstein knew.

IRA FLATOW: Yeah. Our number 844-724-8255. 844-724-SCI-TALK. If you want to tweet us, we’re welcoming your tweets @scifri.

When you heard about Planet Nine last week, was it was this sort of deja vu all over again for you?

TOM LEVENSON: It kind of was. The thing that’s beautiful about Planet Nine is science advances. People do things differently now than they did in the 1850s. The mathematics that Batygin and Brown brought to bear on the problem of trying to understand the orbits of these little Kuiper Belt objects that weren’t behaving as expected, it’s much more sophisticated mathematics than Le Verrier had at his disposal, just as Le Verrier had much more sophisticated mathematics than Newton had as his disposal. So this goes on continuously.

But underneath it all, the argument is exactly the same. There’s stuff out there in the universe that is doing something that we can’t quite fully explain. So let’s try and fill in the gaps. What could possibly account for all that? And there’s a real elegance to it. And I really hope Batygin and Brown are right. I bet they are. Because it’s just such a pleasing argument.

IRA FLATOW: We asked them what they want to call it. They say right now they’re calling it George. And maybe we could– or you could– or everybody could get Vulcan, right? We’re looking for a Vulcan maybe we could just name it Vulcan and do away with that search.

TOM LEVENSON: Vulcan would actually be kind of cool. I have to say. I wouldn’t mind if it were Vulcan. Though I have to say it’s way out there, right? It never gets closer than 250 Earth-Sun distances, astronomical units. It’s cold, it’s dark, the nights are long. Bacchus, the life of the party. That’s be kind of fun as well.

IRA FLATOW: That’s an idea. I’m talking with Tom Levenson, author of a great new book The Hunt for Vulcan: and How Albert Einstein Destroyed a Planet, Discovered, Relativity, and Deciphered the Universe on Science Friday, from PRI, Public Radio International.

And is that search for Vulcan, is that how Vulcan got to be such a big name in science fiction? Star Trek, all these sorts of things. Vulcan this, Vulcan that. People are always asking. As I said, to rename a planet Vulcan.

TOM LEVENSON: You know, I’m not sure if Gene Roddenberry knew about the story of Vulcan. I’d be kind of surprised if he didn’t, because one of the people who wrote, briefly, about Vulcan was somebody that was really important to a lot of people of a certain age getting excited about science is Isaac Asimov.

And I actually, very carefully didn’t read what he had written about this before I wrote my book, because Asimov really has this wonderful voice in his writing and I did want to get that mixed in with mine. But I’d be surprised if Roddenberry didn’t know about it. But I can’t say that he did.

IRA FLATOW: I’ve been reading American history, and the name Vulcan goes all the way back to Thomas Jefferson. You know about this?


IRA FLATOW: Jefferson was a scientist. He did experiments, he and Ben Franklin. And people were looking at the geology of the Earth, and figure out where did the Earth come from. What’s the geology of it? And there were people who said it comes from volcanoes, the lava and stuff that came from volcanoes. Other people are saying, it’s sort of a precipitate out of the ocean. It’s the residue that’s left over.

And the people who– there were two competing theories– believed in the volcanoes were called Vulcans. And they were spelled with a U. I thought it was kind of funny that that name goes so far back, besides being mythology.

TOM LEVENSON: That was a great age of clubs and naming and references back to the Romans and so forth. I can easily see people very happily walking around, maybe not with pointed ears, but very proudly calling themselves Vulcans.

IRA FLATOW: Let’s talk about, in the few seconds we have left, the problem all the time of how long do you keep looking for something in science, until you have to give up on that idea?

TOM LEVENSON: You know, that’s one of the hardest questions. Einstein himself really was different from the rest of his colleagues. I remember his biographer and friend Abraham Pais once told me this, that the thing that always astonished him was just Einstein’s stamina. He wouldn’t stop working on a problem that he thought was interesting.

And that put him in a great place to solve, his great breakthrough of general relativity. And it left him, I think, somewhat at a disadvantage when he worked on unified field theory for so long, at a time when there really wasn’t the amount of data and mathematical apparatus out there needed to make the kind of progress that he would have hoped to achieve.

So it’s never easy, even for somebody like Einstein, to know when to hold them and when to fold them. But one thing that’s happened over the whole history of modern science, since the scientific revolution, is we’ve become more and more sophisticated in defining what constitutes a meaningful result.

So early on in the search for Vulcan, there was an American astronomer, named Gould I believe, who was an early expert in astrophotography, using the then new invention of the camera to make astronomical images and study them. And he did a survey during an eclipse–

IRA FLATOW: Tom, I’m going to have to interrupt you.

TOM LEVENSON: We’re going to cut it off there. It’s a great story.

IRA FLATOW: I love you when you get talking. You can read all about it in Tom’s book The Hunt for Vulcan. Tom Levenson. A wonderful Science Right. Thank you, Tom, for taking time to be with us today.

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