INTRODUCTION A BUMP IN THE NIGHT An observatory in Livingston Louisiana In the early morning hours of September 14 2015 astronomers in two quiet observatories one in Louisiana and the other in Washington State heard a little chirping sound To anyone other than the astronomers who had been waiting for years to hear those noises the chirps might have sounded like some random computer static But to the scientists at the Laser Interferometer Gravitational-Wave Observatory LIGO sites those sounds were potentially groundbreaking 4
LIGO scientists use equipment such as this laser-beam splitter to search for signs of black holes The scientists working at the LIGO sites didn’t get excited right away Instead they got to work They analyzed the data They made sure the noises weren’t a mistake or a fake signal They checked and rechecked their equipment And they kept the chirp a secret Finally in February 2016 they made their announcement A LIGO scientist tests laser equipment
This sky map shows the approximate location of the source of the gravitational waves detected in September 2015 The chirping noises picked up by LIGO were gravitational waves or ripples in space-time The waves came from two distant black holes that collided more than one billion years ago The collision sent ripples through space and time These waves finally rippled through Earth in 2015 and were detected by LIGO This was the first-ever detection of gravitational waves and it helped confirm a theory about the universe that physicist Albert Einstein had come up with in 1915 The detection also proved the idea that two black holes could orbit each other and eventually merge This knowledge will help scientists study and understand black holes where they come from and how powerful they are 6
The detection of gravitational waves helped confirm one of Einstein’s theories about gravity According to some scientists this discovery was the beginning of a whole new way of looking at the universe almost like gaining a new sense Up until now we’ve been deaf to gravitational waves said LIGO executive director David Reitze What’s going to come now is we’re going to hear more things things that we never expected Black holes have been a hard-to-solve mystery for years They are difficult to study and difficult to understand The LIGO discovery has given astronomers one more way to study black holes An artist’s depiction of gravitational waves created by orbiting neutron stars 7
