Nineteenth century astronomers had it right, 20th century got it wrong and it drastically delayed the search for exoplanets
While space based telescopes such as Hubble and Kepler have become really, really damn good at finding exoplanets now that we know what we’re looking for, there was a point in the early 20th century when scientists thought our planet-rich solar system was a total fluke, and it was likely there weren’t many other planets at all in the solar system. Problem is, this overturned 19th century ideas of planetary formation that were right all along, and would have begun the search for exoplanets much earlier. Nineteenth century astronomers believed solar systems formed in gaseous nebulae, but in the 20th century, the idea became popular that our solar system was a freak, and that all the stuff from the other bodies in it was due to another star passing too close to the sun, causing the sun to eject out all kinds of junk that became the planets and moons, and that such an event was probably extremely unlikely to happen in any other cases, if at all.
Trying to figure out exactly what the Big Bang was, what caused it, and what might have come before it, is one of the greatest and most fundamental questions in understanding our universe. One new theory, that may sound crazy, but is mathematically sound and possibly testable, is that what we perceive as a “big bang” was the collapse of a four dimensional star into a black hole, and that our three dimensional universe is merely that four dimensional star being smashed into three dimensions, exactly like how in our universe, three dimensional objects become two dimensional when they reach the event horizon of a black hole.