Leonardo da Vinci predicted how our heart valves close with almost unbelievable powers of deduction and 500 years later, we know he was right. Leonardo became obsessed with the heart in the latter period of his remarkable life. He made a prediction about the main blood vessel leaving the heart, the aorta. He had figured out how the flow of blood out of the heart actually closes the aortic valve. Leonardo had no way of testing it and no way of seeing inside a working heart. For centuries no one else even speculated. But in the last 50 years technology has finally been invented to show that he was absolutely right. --- Thanks for watching. I am new to this so likes are less about getting numbers, but just to know if you thought it was any good - even better please leave a comment, I appreciate any feedback. --- Music: Tango de Manzana by Kevin MacLeod (Creative Commons licence, downloaded from http://incompetech.com/music/royalty-free/index.html?collection=15 References: Incredible British Library digitised version of Leonardo's notebooks and sketches - http://www.bl.uk/manuscripts/Viewer.aspx?ref=arundel_ms_263_f001r Image credit: http://www.sciencedirect.com/science/article/pii/S0021929016306194 Image credit: http://heart.bmj.com/content/83/4/376 Image credit and you've got to check out John Hutchinson's amazing website if you love anatomy, physiology, animals or just gory pictures: https://whatsinjohnsfreezer.com/ Great article by Alastair Sooke about Leonardo's anatomical brilliance: http://www.telegraph.co.uk/culture/art/leonardo-da-vinci/10202124/Leonardo-da-Vinci-Anatomy-of-an-artist.html The landmark study proving him right: http://circres.ahajournals.org/content/circresaha/67/2/448.full.pdf That awesome giraffe study: http://circres.ahajournals.org/content/circresaha/8/5/1049.full.pd Nice overview: https://academic.oup.com/eurheartj/article/35/20/1344/430141/Flow-vortices-in-the-aortic-root-in-vivo-4D-MRI