What is the most surprising and out of nowhere piece of scientific technology that we thought was impossible?

What is the most surprising and out of nowhere piece of scientific technology that we thought was impossible?

Arguably, this:

This is the laser in a Blu-Ray player. A Blu-Ray laser is a blue solid-state strained quantum well laser diode that exploits some very weird physics to work.

About three or four times a week, some question floats through my Quora feed along the lines of “is quantum physics real or is it just made up?” Quantum physics is real, weird-ass freaky quantum mechanical rules are real, and everyday devices like NAND Flash SSDs and Blu-Ray lasers use that freakiness to work.

Quantum well devices are devices that trap electrons into a space about the size of the electron’s wavelength. The electron falls into the well, giving up its energy as a photon as it does. Remember Heisenberg? You can’t know an electron’s absolute position and momentum simultaneously because an electron doesn’t have defined absolute position and momentum simultaneously? Very briefly and handwaving over the mathematical details, when an electron is confined to a quantum well, its momentum becomes indeterminate and it tunnels back out, making space for another electron.

If Heisenberg’s uncertainty principle weren’t true, or if electrons were hard little round balls like tiny marbles with no wavelength, a Blu-Ray laser wouldn’t work.

Me personally, I’ve always wanted to meet the guy who read a paper about the theoretical nature of quantum wells and said “Guys! Hey, you guys! I can make a laser out of that!”