Earth's atmosphere was initially rich in hydrogen ? Carl Sagan explained why that changed during his legendary 1977 Christmas Lectures.
For more out-of-this-world science, don't miss the 2025 Christmas Lectures, with Maggie Aderin-Pocock— they'll be on iPlayer in the UK in late December, and Premiered here on our YouTube channel at 7pm GMT on 28th December.
Join this channel to get access to perks:
https://www.youtube.com/channel/UCYeF244yNGuFefuFKqxIAXw/join
Subscribe for regular science videos: http://bit.ly/RiSubscRibe
The Ri is on Twitter: http://twitter.com/ri_science
and Facebook: http://www.facebook.com/royalinstitution
and TikTok: https://www.tiktok.com/@ri_science
Listen to the Ri podcast: https://podcasters.spotify.com/pod/show/ri-science-podcast
Donate to the RI and help us bring you more lectures: https://www.rigb.org/support-us/donate-ri
Our editorial policy: https://www.rigb.org/editing-ri-talks-and-moderating-comments
Subscribe for the latest science videos: http://bit.ly/RiNewsletter
Product links on this page may be affiliate links which means it won't cost you any extra but we may earn a small commission if you decide to purchase through the link.