Listening to the Whispers of Spacetime: How Accurate Is LIGO?
Imagine trying to measure the distance between Earth and the nearest star outside our solar system over twenty-five trillion miles away with an error margin smaller than the thickness of a single human hair. That mind-boggling level of precision describes the Laser Interferometer Gravitational-Wave Observatory, better known as LIGO. LIGO does not take pictures of stars with optical lenses, nor does it pick up radio signals with dish antennas. Instead, it measures gravitational waves: invisible ripples in the very fabric of space and time created when massive cosmic objects, like colliding black holes or dead stars called neutron stars, crash into each other billions of light-years away. By the time these cosmic ripples travel across the universe and wash over Earth, they are so faint that detecting them requires the most precise ruler ever built by human beings. How Small Is the Measurement? To understand how accurate LIGO is, you have to look at the scale of what it measures. A passin...