Interview: Thomas Levenson, Author Of 'The Hunt For Vulcan' For decades, astronomers believed there was another planet in our solar system, tucked just out of sight. Then Albert Einstein figured out it wasn't there. Author Thomas Levenson explains.

A Star-Crossed 'Scientific Fact': The Story Of Vulcan, Planet That Never Was

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We often like to think that science is all about cold hard facts - things like concrete evidence, mathematical models, replicable experiments - all that to explain the world around us. But in all the data, it's easy to forget that there are people behind those equations and models. And when people are involved, there's always room for - well, what else? - human error. Thomas Levenson's book "The Hunt For Vulcan" explores one pretty glaring error that was taken as fact for more than 50 years. And that is the belief that there was another planet in our solar system that we could not see because it was behind the sun. Thomas Levenson is with us now from the studios at Massachusetts Institute of Technology, where he's the head of the science writing program. Professor Levenson, thanks so much for speaking with us.

THOMAS LEVENSON: Thank you for having me.

MARTIN: How did the idea that Vulcan existed come into being?

LEVENSON: Well, they idea of the planet Vulcan came into being for absolutely the best reasons. You know, the way you find new things in the solar system or anywhere is by noticing something odd about what you already can see. And in the mid-19th century, an extremely talented astronomer - I mean, really, really top-flight guy - was studying the orbit of the planet Mercury, and he found that there was a wobble in it. There was an unexplained extra residue of motion. And, you know, there's a perfect standard explanation in the science of the time - Newtonian - you know, Isaac Newton's great theory for what would cause that extra bit of motion - another planet that we hadn't yet discovered inside the orbit of Mercury that could tug it just slightly off its expected course.

MARTIN: Would you read from the - actually, there's a little section from the preface that I was hoping I could get you to read. Do you have a copy of the book with you?


MARTIN: OK. You want to read that for us?

LEVENSON: All right. (Reading) As a hypothesis, conjuring a plane out of an orbital glitch was perfectly reasonable. Indeed, there was precedent, and at first, it seemed not just logical, but right. Almost as soon as Mercury's plight became public knowledge, amateur and professional astronomers alike spotted and identified an object lurking within the concealing glare of the sun. It would be seen again, over and over, more than a dozen times over two decades. Its own orbit would be calculated, its history recovered in old records of unexplained sightings. It would even receive a name. There was only one problem. The planet Vulcan was never there.

MARTIN: And your book tells the story of how it came to be understood that it wasn't there. And a person - a name that I think any people will know - if they don't know any other scientists' names, they probably know this one. A man named Albert Einstein is the reason that we no longer think that.

LEVENSON: Well, Albert - I mean, I actually think of him as Big Al because I've been working on him so long. But Albert Einstein had a problem in the first decade of the 20th century. In 1905, he invented the special theory of relativity, which explained motion in all kinds of circumstances but one, which was motion under the influence of gravity. And so from about 1907 on, he started trying to reconcile the fact that his special theory of relativity and Newton's laws of motion - Newton's ideas about gravitation - were incompatible. They clashed. And he spent eight years on the problem, completed 100 years ago this month. He showed that it was the actual shape of space and time that produces this visible wobble in its orbit that requires no extra explanation for it. It's just that's the way the shape of space is where it happens to be.

MARTIN: How excited was Einstein about coming to this conclusion?

LEVENSON: Einstein - he kind of lost his mind for a little bit. He did the calculation, you know, to see if Mercury behaved as his - if his theory produced an account of Mercury that behaved as the real Mercury does. And he was working through the calculation, and there are bunch of steps. And he got to the end, and he, you know, got the number. And he looked at the number, and he looked at the table of what astronomers had observed, and he saw that they matched. He said he had palpitations. I mean, his heart was literally shuddering in his chest. I just have this vision - I mean, this is completely made up, but I have this vision of Einstein, sockless, dancing at his desk when he got the number, right? Just, you know...

MARTIN: Why do you think the story of Vulcan isn't better known? I'm wondering if you think it's one of the things that should be taught as a cautionary tale of forcing the facts to fit the explanation.

LEVENSON: We don't teach the history of science by the things that people messed up on. We teach the history of science - we teach all of history by the things that worked. You know, the transcontinental railroad goes through, and you drive the golden spike, and there it is. You don't talk to all the, you know, railroad companies that went bankrupt somewhere in the Great Plains, right? And in science, you don't dwell on the blind alleys, but the blind alleys are most of what science actually does. You have to go down the blind alley. You bang your head against that, you know, blank wall at the end of it, come back out again and try something else. And that's the real experience, and that's why Vulcan is so wonderful. It shows how you do it and, ultimately, how you get out of that.

MARTIN: But I do have ask you - so I do - I do find myself wondering - are there things that we assume today that will turn out to be ridiculous in the future?

LEVENSON: I am absolutely certain. I mean, I'd bet real money on this that 100 years from now somebody's going to look back on things we believe about who knows what - our current theories of the brain or consciousness, some of the deep ideas people work in physics, ways that, you know, social relations are presumed to work. Anything - you name it. There's something out there. We have assumption, we have a mental model, we have a theory that just isn't right.

And a hundred years from now, somebody's going to look back at them and say - wasn't that ridiculous? How could they get it so wrong? Isn't it obvious? I mean, yeah, human beings don't get things right all at once. It takes us a lot of time. We make a lot of mistakes. We have category mistakes. And it takes a great leap of the imagination to get from what you really know you know to the wacky thing that turns out to be more true than your remembered-but-erroneous past.

MARTIN: Thomas Levenson - his book is called "The Hunt For Vulcan And How Albert Einstein Destroyed A Planet, Discovered Relativity And Deciphered The Universe." Professor Levenson, thank you very much.

LEVENSON: Thank you. And, you know, I've been holding this back all the time I've been writing my book. To everyone out there, live long and prosper.

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