In 1654 a German scientist and politician named Otto von Guericke was supposed to be busy being the mayor of Magdeburg. But instead he was putting on a demonstration for lords of the Holy Roman Empire. With his newfangled invention, a vacuum pump, he sucked the air out of a copper sphere constructed of two hemispheres. He then had two teams of horses, 15 in each, attempt to pull the hemispheres apart. To the astonishment of the royal onlookers, the horses couldn’t separate the hemispheres because of the overwhelming pressure of the atmosphere around them.
Von Guericke became obsessed by the idea of a vacuum after learning about the recent and radical idea of a heliocentric universe: a cosmos with the sun at the center and the planets whipping around it. But for this idea to work, the space between the planets had to be filled with nothing. Otherwise friction would slow the planets down.
Scientists, philosophers, and theologians across the globe had debated the existence of the vacuum for millennia, and here was von Guericke and a bunch of horses showing that it was real. But the idea of the vacuum remained uncomfortable, and only begrudgingly acknowledged. We might be able to artificially create a vacuum with enough cleverness here on Earth, but nature abhorred the idea. Scientists produced a compromise: the space of space was filled with a fifth element, an aether, a substance that did not have much in the way of manifest properties, but it most definitely wasn’t nothing.
But as the quantum and cosmological revolutions of the 20th century arrived, scientists never found this aether and continued to turn up empty handed.
The more we looked, through increasingly powerful telescopes and microscopes, the more we discovered nothing. In the 1920s astronomer Edwin Hubble discovered that the Andromeda nebula was actually the Andromeda galaxy, an island home of billions of stars sitting a staggering 2.5 million light-years away. As far as we could tell, all those lonely light years were filled with not much at all, just the occasional lost hydrogen atom or wandering photon. Compared to the relatively small size of galaxies themselves (our own Milky Way stretches across for a mere 100,000 light-years), the universe seemed dominated by absence. [Continue reading…]