TBF they really thought we'd uncover technologies such as:
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Electro Aviation - up until the 1980s-ish a lot of people including researchers believed Magnetic Levitating Aviation was possible.
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Infinite Nuclear Power - Nuclear power plants use decaying nuclear materials, fission, to heat water to turn turbines. Another type of nuclear energy is called Fusion, it's the process behind the Atomic Bombs that leveled Nagasaki, Hiroshima, and Bikini Atoll. Cold Fusion, a type of theoretical fusion completely contained via electromagnetic field or advanced materials, was expected to happen at any moment in the last 60 years.
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Faster than Light Travel - With nearly infinite power and nearly infinite thrust and therefor speed, we should have been able to go anywhere in the universe.
Sadly, all of it was wrong. Chances are, at the rate we're going, all habitable systems' stars will completely die out before we ever catch a good glimpse at them, a part of space we refer to as "the local group" is a portion we could theoretically reach before the end of the universe and it's quite limited.