TechloreHQ on Instagram: "Before electricity, speakers, or the internet, sound could still be recorded and played back. Thomas Edison’s 1877 phonograph did it using pure mechanics: sound waves vibrated a needle, which etched grooves into a rotating surface. When replayed, those grooves pushed the needle back into motion, recreating the sound. What makes this even more impressive is that a kid has recreated the same core principle using nothing more than two cups and a needle. No power. No electr

Coulomb's law