Get up to 91% off yearly web hosting plans. Go to https://www.hostinger.com/stevemould and use promo code stevemould at checkout. (you can also go to http://1sm.me/a) 1 - you can cut ice with a blunt diamond because it is such a good conductor of heat 2 - The filament in an old fashioned incandescent light bulb is a helix of a helix - a meta helix! 3 - Some vampire bats mimic chicks so they can snuggle up to a hen's brood patch and drink her blood. 4 - The word "second", as in the length of time comes from the fact that it is the second time we subdivide the hour into smaller units. The first time being minutes. So why aren't minutes called firsts? 5 - Most owls have asymmetrical ears. It helps them to figure out the direction of its prey by sound. The asymmetry causes an interaural intensity difference that the owl can use to figure out the origin of sound in the vertical plane. Here's Bill Schutt's articles about vampire bat behaviour: http://www.naturalhistorymag.com/features/31700/the-curious-bloody-lives-of-vampire-bats Thanks to Dr. Kelly Williams for her photograph of the inside of an owl's ear (at 8:12). Thanks to Dr. James Duncan at Discover Owls for this image: https://www.owlpages.com/owls/articles.php?i=14 Other image credits: Batfossil - https://en.m.wikipedia.org/wiki/File:Common_Vampire_Bat_Skull.jpg Oasalehm - https://commons.wikimedia.org/wiki/File:Vampire_bat_allogrooming.jpg Sandstein - https://en.wikipedia.org/wiki/File:Desmodus_rotundus_feeding.jpg You can buy my books here: https://stevemould.com/books You can support me on Patreon here: https://www.patreon.com/stevemould just like these amazing people: Nathan Williams Matthew Cocke Glenn Watson Mark Brouwer Joël van der Loo Alex Southwell Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk/