If you ask me? Mobile/WiFi internet… The way and amount of time we use our phones had changed A LOT since their diffusion. I guess the release of the iPhone changed our idea of what a phone is too
Edit: when I say modern world I’m referring to the last 50 years. So stuff like “the electricity” or “the telephone” doesn’t count.
Transistors is the defacto answer. We wouldn’t have anything we have now without them.
Oh you say but what about (this thing) that doesn’t have any in it? The factory it was mass produced in runs on transistors.
Going down the list of comments in this post:
Telephones. Always had transistors.
Internet. Obvious.
Coal. Everything from the trucks to the converors, to the systems that track production, and all the transportation involved after uses them.
Washing machines also use them even if they’re not the stupid “smart” machines people buy for some reason.
Edit. If you’re in anyway curious about transistors here’s a new video from Asianometry about them:
https://youtu.be/k8cdByDa3oA?si=5B4tgJjP7X7jIuhT
Something worth repeating is that transistors are a direct application of quantum mechanics. Quantum physics isn’t a metaphysical thing about half dead cats and working only on a few ultra cold atoms. If you want to explain how a piece of silicium can be conductive or insulating depending on it’s polarisation you need… Quantum physics.
Holes and dots.
its* polarization (or polarisation, in your part of the world.)