Everything you need to know about gravitational waves. In February 2016 scientists announced the first detection of gravitational waves by humans on Earth. This was a huge, world changing, discovery. The gravitational waves were caused by a pair of colliding black holes 1.3 billion light years away 1.3 billion years ago. This video summaries all the of the mind blowing facts about the gravitational waves and describes LIGO, the incredibly sensitive telescope that detected them. #gravitationalwaves #space #DomainOfScience If you would like to buy a poster you can get one here http://www.redbubble.com/people/dominicwalliman/works/24649310-gravitational-wave-astronomy?asc=u&p=poster&rel=carousel Errata and clarifications. I endeavour to be as accurate as possible in my videos, but I am human and definitely don’t know everything, so there are sometimes mistakes. Also, because my videos are summaries of some quite complex science, I make simplifications. Some of these are intentional because I don’t have time to go into full detail, but sometimes they are unintentional and here is where I clear them up. 1. I got the month of the original detection wrong! It was September 2015, not November 2015. Silly me, my apologies. 2. “1.3 billion years ago, 1.3 billion light years away” This is incorrect and an oversight on my part. I completely forgot to take into account the expansion of the Universe. The resulting black hole is 1.3 billion light years from us today, but was closer to us when the collision happened, which means that it happened less than 1.3 billion years ago. I tried to work out exactly when but was stumped because I couldn’t find the function for the acceleration of the expansion of the universe. The redshift of the signal from the black holes was about 10%, so I thought the collision was 10% closer in time than 1.3 billion years i.e. 1.18 billion years, but I think it might be a bit more complicated than that. 3. LIGO schematic animation. I made a couple of silly errors here. The first circular mirror that the laser hits should be 90º to the way I oriented it: half the laser light is transmitted and half reflected, each one going up a different arm. 4. LIGO schematic animation. When the laser bounced back and forth it should bounce between the two suspended mirrors and not go all the way back to the diagonal mirror. 5. VIRGO is near Pisa, not at Trento as I drew on the map. I said the right thing but drew the wrong thing. My apologies. 6. ‘A second even more powerful collision.” Wrong again! The second collision was less powerful and the signal was more buried in the noise. I’m not happy with the number of flat out mistakes I made on this one! I will try better in the future. I blame it on the Christmas spirits. If you would like to find out more about gravitational waves and the detection here are the original papers and some very informative links. Main LIGO scientific paper: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 Supplementary LIGO paper: http://iopscience.iop.org/article/10.3847/2041-8205/818/2/L22 Articles: http://physicsworld.com/cws/article/news/2016/feb/11/ligo-detects-first-ever-gravitational-waves-from-two-merging-black-holes http://www.nature.com/news/the-black-hole-collision-that-reshaped-physics-1.19612 http://www.businessinsider.com/black-hole-collision-energy-50-times-universe-2016-2 http://www.space.com/33176-gravitational-waves-from-second-black-hole-collision.html http://www.ligo.org/science/Publication-GW150914/index.php http://www.nature.com/news/gravitational-waves-6-cosmic-questions-they-can-tackle-1.19337 http://www.nature.com/news/the-black-hole-collision-that-reshaped-physics-1.19612 What they sound like: http://www.vox.com/2016/6/15/11948618/ligo-gravitational-waves-black-hole-sound Also, if you enjoyed this video, you will probably like my science books, available in all good books shops around the work and is printed in 16 languages. Links are below or just search for Professor Astro Cat. They are fun children's books aimed at the age range 7-12. But they are also a hit with adults who want good explanations of science. The books have won awards and the app won a Webby. Frontiers of Space: http://nobrow.net/shop/professor-astro-cats-frontiers-of-space/ Atomic Adventure: http://nobrow.net/shop/professor-astro-cats-atomic-adventure/ Intergalactic Activity Book: http://nobrow.net/shop/professor-astro-cats-intergalactic-activity-book/ Solar System App: http://www.minilabstudios.com/apps/professor-astro-cats-solar-system/ Find me on twitter, instagram, and my website: http://dominicwalliman.com/ https://twitter.com/DominicWalliman https://www.instagram.com/dominicwalliman https://www.facebook.com/dominicwalliman