Recently, I have had the odd experience of reading or watching something, and having to remind myself that a particular piece of technology is science-fiction, or at least was to the author and intended audience. You know when the Avengers and Fantastic Four casually have video conferences, or when Captain Picard asks the computer to locate Commander Riker? Video conferencing, and voice-activated computers, were, at the time these media were designed, were only slightly less fanciful than adamantium skeletons or warp drives. But in 2020, it seems quite natural to teleconference and talk with a computer. At some point in the past 20 to 40 years the technology went from science-fiction to experimental to high-end to a normal part of life.

The existence of extrasolar planets (or "exoplanets") also has taken such a trajectory. For any science-fiction stories written or filmed before the mid 1990s, the existence of planets outside our solar system was still a theoretical possibility. When Star Trek, Star Wars, Super Man, Dune, Masters of Orion, Doctor Who, The Fantastic Four, The Foundation Trilogy, The Hitchhikers Guide to the Galaxy, ET, or any other media featuring or mentioning alien planets were released, there was no scientific evidence that other planets existed, at all. Then, back in 1992, scientists discovered the first exoplanet. By the mid 1990s, they had discovered a few more. The first few planets discovered were highly unusual, massive planets orbiting very close to their stars. This was an artifact of the technology used to discover the planets, and as the technology was refined, entire systems of planets were discovered. Systems full of Hot Jupiters and Superearths, but also full of what appear to be terrestrial planets in the habitable zone. What is interesting to me is there was never a single moment when extrasolar planets crossed the line from theory and fiction to prosaic reality. At first, the examples of planets were few and far between, and were very unusual. But the trickle of discoveries turned into a flow, and then into a flood, especially after the launch of the Kepler Space Telescope in 2009. We now know, as much as we know anything in astronomy, that planets like our earth, and stellar systems like our solar system, are fairly common, and that there are possibly billions of planets like our earth, in the galaxy. But there was never a defining moment when this turned from dream into fact.

I also find it interesting how big of a difference there is between the long, protracted nuts and bolts work of finding exoplanets, as opposed to the discoveries of the past. A little over a hundred years ago, Albert Einstein basically revolutionized physics by making a conceptual leap. Other physicists since him have tried to do the same, as mathematical abstractions such as reconciling general relativity with quantum mechanics became somewhat of a holy grail for physicists. In contrast, the process of finding exoplanets---sorting through computer generated data to find a pattern that evidences the existence of a planet around a star---is done by teams and organizations, and involves slowly combing over data. However, the results of the search are just as paradigm shifting as the more abstract astrophysics that was popular for most of the 20th century.