If life exists elsewhere in the Universe, would we be able to communicate with it? In this clip from the 1977 CHRISTMAS LECTURES "The planets", Carl Sagan demonstrates how we could send a signal that would make sense to intelligent beings that have evolved independently from us. Subscribe for regular science videos: http://bit.ly/RiSubscRibe This video is from our 2017 advent calendar. Watch the full series here:    • Transmissions through Time   Or watch the full lecture here: http://www.rigb.org/christmas-lectures/watch/1977/the-planets/planetary-systems-beyond-our-sun?utm_source=youtube&utm_medium=social&utm_campaign=2017_advent&utm_content=description The Royal Institution 2017 advent calendar ‘Transmissions Through Time’ looks through the lens of CHRISTMAS LECTURES past to share the best demonstrations around the science of communication. From Attenborough and Sagan to Woollard and Fong, we revisit old favourites and find new gems to bring you a little gift of science every day in the lead up to Christmas. http://bit.ly/RiAdvent17 The Ri is on Twitter: http://twitter.com/ri_science and Facebook: http://www.facebook.com/royalinstitution and Tumblr: http://ri-science.tumblr.com/ Our editorial policy: http://www.rigb.org/home/editorial-policy Subscribe for the latest science videos: http://bit.ly/RiNewsletter