Hi, hello⁣ IM AT LIGO (!!!!)⁣ ⁣ And THIS CHAMBER right here is where the first gravitational 〰️ waves were detected.⁣ ⁣ 🤔 what is a gravitational wave? These are ripples through the fabric of spacetime 🤯and they're caused by large catastrophic events like 2 black holes merging, stars exploding, etc⁣ ⁣ 〰️ how do you measure them?⁣ WITH ONE OF THE GREATEST ENGINEERING MARVELS OF ALL TIME⁣ ⁣ 🔢 Gravity waves propagate like a hula hoop that is squeezed - it smooshes things in one direction and stretches them in the other. So at LIGO they have 2 long tubes shaped like an "L". They shoot lasers down each tube and because we know the speed of light we can tell if one side got longer or shorter. (More complex than this, but sort of like this)⁣ if they did, then we have a candidate gravity wave! ⁣ 🛠️ To achieve this, they needed:⁣ 1️⃣Two 4km arms which are so long that you need to account for the curvature of the Earth to keep the laser beam straight⁣ 2️⃣ The smoothest mirrors ever created (...