In science, advances arise at the intersection of theory and real-world observation.
Our measurements reveal what does exist, but only theory can predict what should exist.
Throughout astronomy’s history, observations led the way, revealing the Universe for theorists to describe.
That would change after 1781, following William Herschel’s serendipitous discovery of Uranus.
The other planets dutifully followed the laws of planetary motion, but Uranus appeared to violate them.
Breaking Kepler’s laws, Uranus moved too quickly for decades, then at the right speed, then too slowly.
The observations weren’t easily dismissable, but their physical cause was unknown.
An additional planet beyond Uranus, gravitationally tugging on it, offered a potential solution.
Determining the mass, orbital parameters, and location of an unseen world presented incredible calculational challenges.
On August 31, 1846, Urbain Le Verrier composed a letter detailing the hypothetical planet’s location.
On September 23, the letter arrived at the Berlin Observatory.
That evening, within 1° of Le Verrier’s prediction, Neptune was discovered.
For the first time, a new astronomical object was discovered through its gravity alone.
François Arago, who compelled Le Verrier to investigate Uranus’ orbit, lauded him as “the discoverer of a planet with the point of his pen.”
Mostly Mute Monday tells the astronomical story of an object, phenomenon, or discovery in visuals, images, and no more than 200 words. Talk less; smile more.