00:29Wholes lurk in the hearts of most galaxies, and galaxies grow by merging with other
00:35galaxies. When that happens, their black holes also merge and grow, becoming more and more
00:41massive over time. How exactly this happens is not fully understood, but the universe
00:48is telling us its secrets in gravitational whispers. We just have to listen.
00:54Just as sound waves are vibrations of air molecules, gravitational waves are vibrations
00:59in the fabric of space-time. When two massive black holes spiral toward each other, they
01:05produce gravitational waves that travel through the cosmos at the speed of light.
01:10If we imagine the universe as a grand symphony, these merging supermassive black holes are
01:15the bass players. As they orbit each other, these black holes play the deep bass notes
01:21that echo throughout the cosmic concert hall. But that's not all there is to the symphony.
01:27In the background is a faint but pervasive hum produced by the collective motion of massive
01:32objects throughout the universe, from the earliest moments of the Big Bang until now.
01:38This gravitational wave background is truly a harmony of space and time.
01:44Nanograv is an NSF-funded collaboration of astronomers and astrophysicists. Our goal is to solve some
01:50of the deepest mysteries of the universe by studying the gravitational waves produced by these dancing
01:55monster black holes. These waves are light years long and can only be detected by the most
02:01extraordinary instruments. To measure these giant but subtle ripples in space-time, Nanograv created
02:09a galaxy-sized detector using some of the most incredible objects in the cosmos, rapidly rotating neutron stars, known as millisecond pulsars.
02:17Pulsars are the ultra-dense remnants left behind when massive stars reach the end of their lives
02:24and explode as supernovae. These pulsars are also cosmic beacons. They spin extraordinarily rapidly
02:30and with startling regularity, releasing pulses of radio waves with each rotation. Astronomers detect
02:38those pulses using giant radio telescopes. By monitoring the radio pulses from these ultra-precise
02:45cosmic clocks, Nanograv can detect the slightest deviations in the regularity of their timekeeping,
02:51and these deviations trace ripples in space-time. This galactic scale detector is called a pulsar timing array.
02:59Nanograv has now observed an array of dozens of pulsars for more than 15 years, and the results are astounding.
03:08We are finally hearing the faint background hum likely coming from in-spiraling pairs of supermassive black holes.
03:15With time, astronomers expect to pick out the individual instruments in this cosmic symphony, revealing unique insights into the evolution of galaxies and the history of the cosmos.
03:26We are now seeing the most free×™×›ess of the cosmic enrichment of galaxies based on the radio waves.
03:30We've known all of these 10,000 people start to think about the supernatural gifts,
03:33and at the current level of the cosmos.
03:34We've been to the museum and he nearly 2,000 people start to think about the light.
03:35In this space, we've had lots of three-thirds of the entire planet and the life-backer.
03:38We're all about 10,000 people start to think about the world's theory of something that it's COSMOS.
03:40The clocks are the most important, and at the time we hear critically about the world's architecture,
03:42we're almost there to be aulanimate component to the world's knowledge.
03:43Here we've heard a lot of the history of the cosmos,
03:45we've been able to start from a homepage.
03:46We'd rather be able to around 1,000 people start to think about the world's theory of what we're trying.
