In the 19th century, astronomy experienced a golden age. Scientists discovered new worlds without leaving their desks—simply via mathematics. Yet, amidst these triumphs, lurked one of science’s most instructive errors—the planet Vulcan. Dozens of astronomers sought it, it was “seen” through telescopes, and its existence was dictated by the laws of physics. We recount how the desire to uphold a beautiful theory led researchers to chase a phantom for half a century.
Triumph at the Tip of a Pen
The saga of the pursuit of the mysterious planet began in 1846. At that time, Newton’s laws of universal gravitation were considered absolute truth. But there was an issue: the planet Uranus moved irregularly. It constantly deviated from its calculated path, as if something immense were pulling on it.
French mathematician Urbain Le Verrier took on the enigma. He did not look to the skies but immersed himself in calculations. Le Verrier solved the “inverse problem”: he calculated where an unknown planet must be located for its gravity to account for Uranus’s peculiarities. On August 31, 1846, he dispatched the coordinates to Berlin. Astronomers aimed their telescopes at the specified location and… found the planet Neptune. The discrepancy was less than one degree.
It was a monumental achievement. Le Verrier was hailed as the man who “discovered a planet at the tip of his pen.” This event convinced everyone: if Newtonian calculations predicted a planet, it must exist there.
Black Hole or Ninth Planet: What Hides in the Solar System
A Crack in the Celestial Clockwork
Encouraged by his success, Le Verrier sought to bring order to the entire Solar System. He analyzed Mercury and stumbled upon another anomaly. Mercury orbits the Sun along an elongated path. This orbit itself slowly rotates—a phenomenon called perihelion precession. Le Verrier accounted for the influence of all its neighbors: Venus, Earth, Mars, Jupiter. But the figures did not align.
Map of the Solar System featuring the planet Vulcan, 1846
Mercury’s actual orbit was shifting faster than theory predicted. The difference was minute—43 arcseconds per century. This is akin to viewing a coin from several kilometers away. But for exact science, it was a catastrophe. Either the great Newton was mistaken, or something massive was lurking near Mercury.
The Birth of Vulcan
Le Verrier could not accept that Newton was wrong. In 1859, he announced that the anomaly was caused by an unknown planet or an asteroid belt situated even closer to the Sun. The new world was named Vulcan—after the Roman god of fire. It was apt for a planet literally roasting in the “solar furnace.” Mathematicians even calculated its characteristics:
Distance from the Sun—21 million km (only a third of Mercury’s distance).
A year on the planet lasts about 19 Earth days.
Observing the planet is nearly impossible due to the Sun’s intense glare.
The Country Doctor and His Find
As soon as the hypothesis was published, Le Verrier received a letter from a country doctor and amateur astronomer, Edmond Lescarbault. The doctor claimed to have witnessed a small dark dot crossing the Sun’s disk six months prior.
Le Verrier, noted for his difficult temperament, personally traveled to the village to interrogate the physician. The amateur’s equipment was rudimentary: he measured the transit time of the dot using old clocks and timing his own pulse as a metronome.
Yet, the details matched the calculations. Lescarbault described a round object moving precisely as the planet should. Le Verrier believed him. On January 2, 1860, the discovery of Vulcan was officially announced, and the modest doctor received the Legion of Honour order.
Hunting the Shadow
It seemed the matter was settled. Vulcan entered textbooks. But problems soon arose: no one else could find it. Astronomers understood: the sole chance to see an object this near the star was to wait for a total solar eclipse, when the Moon would block the blinding light. The period from 1860 to 1878 became a true gold rush for “Vulcan hunters.”
The climax occurred during the 1878 eclipse in the USA. Two respected astronomers, James Watson and Lewis Swift, independently declared they had seen a red disk adjoining the Sun. Newspapers rejoiced.
However, scrutiny revealed something strange: the coordinates of the two “Vulcans” did not match each other, nor did they match the calculations. Most likely, in the haste and darkness, the astronomers mistook known stars in the constellation of Cancer for the planet.
By the turn of the 20th century, technology had advanced. Powerful cameras at the Lick Observatory definitively proved: there is nothing larger than 20 kilometers inside Mercury’s orbit. Vulcan did not exist. But Mercury’s anomaly remained, a persistent “blemish” in physics.
Einstein’s Solution
The resolution came not from a telescope but from the mind of Albert Einstein. In 1915, he completed the General Theory of Relativity (GTR). Einstein proposed a revolutionary concept: gravity is not an invisible force, as Newton believed, but a warping of space and time. The Sun is so massive that it creates a deep “gravitational well” around itself.
Mercury, being closest to the star, traverses space that is severely curved. It must cover a slightly longer path than it would in Newton’s “flat” cosmos. Einstein plugged Mercury’s orbital parameters into his new equations. The outcome was astonishing:
Newtonian mechanics yielded an error of 43 arcseconds.
Einstein’s formula predicted a shift of exactly 43 arcseconds.
No hidden planet was needed to explain the anomaly. It was all a matter of the Universe’s geometry. Upon seeing these figures, Einstein was, by his own account, “beside himself with delight.”
This discovery both thrilled and unnerved Einstein: he could not fully accept it until the end of his life.
Why Did Scientists Err?
The story of Vulcan is a prime illustration of how the human mind operates. Psychologists label this confirmation bias. Here is how it works:
The success trap. Scientists were so accustomed to Newtonian theory being correct that they could not conceive of its fallibility.
Seeing what you desire. Astronomers knew what they were supposed to see. Therefore, any optical defect, sunspot, or passing bird was interpreted by the brain as the long-awaited planet.
Although Vulcan’s existence turned out to be mistaken, its search was not futile—it forced science to abandon old dogmas and embrace a new, far more complex depiction of the world, proposed by Einstein. And the name Vulcan found a new purpose—in science fiction, fittingly.
About the Author
