When you think of dangerous geological specimens, does your mind jump straight to radioactive uranium, toxic heavy metals, or even asbestos? What if one of the most dangerous items sitting on a shelf is actually a polished, perfectly ordinary-looking piece of black onyx? Professor Hannah Fry and Michael Stevens dive into the surprisingly treacherous geology and chemistry of onyx. Hannah brings an onyx from her personal rock collection to explain exactly why this specific piece of material holds the title of the most dangerous rock she owns, unpicking the fascinating physical properties of the stone and exploring how its conchoidal fracture pattern can easily create edges sharper than a modern surgical scalpel. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠⁠https://cancerresearchuk.org/restisscience⁠⁠ Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Video Editor: Jack Meek Animator: Sam Benson Video & Social: Bex Tyrrell Assistant Producer: Lucy Lipscombe Producer: Simona Rata Senior Producer: Lauren Armstrong-Carter Chief Digital Officer: Samuel Oakley Exec Producer: Neil Fearn ------------------- 00:00 Intro 00:18 If you were out in space in the vicinity of a pair of black holes colliding, would you be able to feel the gravitational wave from the collision pass through you? 01:49 Cancer Research UK 03:00 Black holes colliding continued 14:05 If there’s so much trash in space, why can’t we see it in photos from the ISS? 25:20 Should it be more effort to walk up stairs or an escalator? 31:35 What is the sharpest object in the universe? 52:15 Outro