*Watch with headphones on! Is 45 minutes really the longest anyone can stay in a perfectly silent, pitch-black room? Support Veritasium on Patreon Check out Audible: Want to watch the whole hour of silence? Many stories have circulated claiming the longest anyone has stayed in an ultra-quiet anechoic chamber is 45 minutes, the reason being any longer would drive you insane. To me this sounded like unsubstantiated rubbish, like the claim the Great Wall is the only manmade structure visible from space. So I put my own psyche on the line, subjecting myself to over an hour of the most intense quiet on Earth. No, this was not THE quietest room on Earth (-9dB) but it is one of the quietest, and the truth is once you put a person inside, they are by far the loudest thing in there so the sound rating of the room is irrelevant.
I was not surprised to find that I could stay in there for as long as I liked and feel perfectly fine. What was surprising is that my heartbeat was audible. You can hear it on the sound recording. Now I wasn't consciously aware of the sound of my heart while in the room, but I was more aware of the feeling of it beating.
Huge thank you to everyone at BYU: Duane Merrell, Spencer Perry, Cameron Vongsawad, Jazz Myers, Ann Clawson, and Robert Willes.
Who on Earth is exposed to the most ionizing radiation? Check out Audible: I'm filming a documentary for TV about how Uranium and radioactivity have shaped the modern world. It will be broadcast in mid-2015, details to come. The filming took me to the most radioactive places on Earth (and some places, which surprisingly aren't as radioactive as you'd think). Chernobyl and Fukushima were incredible to see as they present post-apocalyptic landscapes. I also visited nuclear power plants, research reactors, Marie Curie's institute, Einstein's apartment, nuclear medicine areas of hospitals, uranium mines, nuclear bomb sites, and interviewed numerous experts. Notes about measuring radiation: Sieverts are a measure of 'effective dose' - that means they measure the biological impact of the energy transferred to tissues from radiation. Obviously I owe a debt to the fantastic chart made by xkcd, which inspired my visual approach to this video. DOSES MAY VARY The level of radiation varies widely around the world depending mainly on altitude and geology (excluding nuclear accidents). Estimates of particular doses also vary. All numbers reported in this video should be taken as order of magnitude only. The most contentious claim may be that smokers receive the highest dose of ionizing radiation. This is not a whole body dose, but a dose to the lungs as specified in the video. References are here: Special thanks to: Physics Girl: MinutePhysics: Natalie Tran: Bionerd23: Nigel and Helen for feedback on earlier drafts of this video. Music is "Stale Mate".
Why is there something instead of nothing? In other words: Why does the universe exist (and why are we in it)? Philosopher and writer Jim Holt follows this question toward three possible answers. Or four. Or none. TEDTalks is a daily video podcast of the best talks and performances from the TED Conference, where the world's leading thinkers and doers give the talk of their lives in 18 minutes (or less). Look for talks on Technology, Entertainment and Design - plus science, business, global issues, the arts and much more. Find closed captions and translated subtitles in many languages at Follow TED news on Twitter: Like TED on Facebook: Subscribe to our channel. The world's roundest object helps solve the longest running problem in measurement - how to define the kilogram. Support Veritasium on Patreon: A kilogram isn't what it used to be. Literally. The original name for it was the 'grave', proposed in 1793 but it fell victim to the French Revolution like its creator, Lavoisier. So begins the tale of the most unusual SI unit. The kilogram is the only base unit with a prefix in its name, and the only one still defined by a physical artifact, the international prototype kilogram or IPK. But the problem with this definition has long been apparent. The IPK doesn't seem to maintain its mass compared to 40 similar cylinders minted at the same time. The goal is therefore to eliminate the kilogram's dependence on a physical object. Two main approaches are being considered to achieve this end: the Avogadro Project and the Watt Balance. The Avogadro project aims to redefine Avogadro's constant (currently defined by the kilogram - the number of atoms in 12 g of carbon-12) and reverse the relationship so that the kilogram is precisely specified by Avogadro's constant. This method required creating the most perfect sphere on Earth. It is made out of a single crystal of silicon 28 atoms. By carefully measuring the diameter, the volume can be precisely specified. Since the atom spacing of silicon is well known, the number of atoms in a sphere can be accurately calculated. This allows for a very precise determination of Avogadro's constant. Special thanks to Katie Green, Dr. David Farrant, the CSIRO, and the National Measurment Institute for their help. Thanks also to Nessy Hill for filming and reviewing earlier drafts of this video. There is debate as to whether this is truly the roundest object ever created. The Gravity Probe-B rotors are also spherical with very low tolerances such that they may in fact be rounder. Music by Kevin McLeod (incompetech) Decision, Danse Macabre, Scissors.