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FOLLOWERS OF Star Trek recognize planet Vulcan as the birthplace of Spock’s father Sarek (his mother Amanda was an Earthling).


A Trekkie family portrait: Spock with his Vulcan father Sarek and Earthling mother Amanda.

What’s more, there was a respected mathematician who believed he had already identified an actual planet Vulcan in 1859. Its existence wasn’t completely debunked until Einstein’s discovery of General Relativity more than five decades later.

The December 18, 2015, issue of Science, published by the American Association for the Advancement of Science, has a review of The Hunt for Vulcan by Thomas Levenson. Levenson is the director of MIT’s Graduate Program in Science Writing, and he tells the tale of planet Vulcan as a good mystery story dating back to 1680s.

It was Sir Isaac Newton’s Philosophiæ Naturalis Principia Mathematica, 1687, that defined scientific thought for more than 225 years. Relevant to our Vulcan story, Newton’s Laws of Motion dictated the movements of planets.


Urbain Jean Joseph Le Verrier, 1811 – 1877, French mathematician. His calculations predicted the existence of planets Neptune and Vulcan.

As Levenson describes it, “The great romantic triumph of Newtonian science was the discovery of the planet Neptune, in 1846.” French mathematician Urbain Le Verrier studied oddities in the orbit of planet Uranus and concluded theoretically there must be another planet tugging Uranus out of its predicted path.


Planet Neptune, from Voyager 2 spacecraft. Image from NASA-JPL.

Le Verrier described this planet’s coordinates to German astronomer Johann Gottfried Galle. The same night Galle received Le Verrier’s letter, he discovered this new planet, Neptune, within 1 degree of its predicted position. Englishman John Couch Adams, doing parallel research, made the same discovery as Le Verrier’s. Adams may have started earlier, but announced his findings later.


Planet Mercury. Enhanced-color view assembled from images taken by Messenger spacecraft. Image from NASA-Johns Hopkins University Applied Physics/Carnegie Institution of Washington.

Le Verrier then turned his attention to planet Mercury, which exhibited a tiny discrepancy in its known wobble (technical name: its precession). He used the same reasoning as he had with Uranus and came to a similar conclusion in 1859: Mercury was being affected by another planet orbiting even closer to the sun.

Because of this hypothetical planet’s solar proximity, it received the name Vulcan, after the Roman god of fire. Levenson says, “What followed was a cat-and-mouse game: Some people looked for Vulcan and couldn’t find it, while there were repeated reports of discovery by professionals and amateurs alike.”

Like Mercury, Vulcan would be difficult to observe. One technique is to wait for a solar eclipse. A more frequent research opportunity comes with a planet’s “transit,” its traveling between us and the sun, visible as a tiny dot on the sun’s image.

Then, in 1915, Albert Einstein published his General Theory of Relativity. And, as a stunning experimental confirmation of relativistic prediction, Mercury’s wobble was explained without recourse to any other planet: Its behavior was consistent with the sun’s gravity bending Mercury’s image on its way to us.


One of the implications of General Relativity: Gravity bends space. Image by User: Johnstone.

Levenson draws two conclusions from this: “One is when you have a worldview that is so powerful and works so well [like Newtonian science], it conditions the way you see the world.”

His second: “The problem [with Vulcan] wasn’t the missing planet, the problem was thinking about space and time in the wrong way…. We are not immune to measurement error, and we’re certainly not immune to the capacity for human self-deception.” ds

© Dennis Simanaitis,, 2016

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