World's Roundest Object!

  • Added:  4 years ago
  • The world's roundest object helps solve the longest running problem in measurement -- how to define the kilogram.
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    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 ( Decision, Danse Macabre, Scissors
  • Video CategoriesEducation
  • Runtime: 11:44
  • Tags for this video:  veritasium  science  physics  Perfect  sphere  kilogram  avogadro  avogadro project  redefining the kilogram  kilo  metric system  silicon  silicon sphere  silicon-28  silicon 28  watt balance  bipm  history of the kilogram  grave  units  SI units  definition  gram  mass  quantity  weight  weights  kilograms  csiro  kilogram of the archives  kilogramme  definition of the kilogram  unit  perfect sphere  roundest object  world's roundest object  kilogram definition  

Comments: 29 865

  • Jason Li
    Jason Li 19 minutes ago

    1:45 I'm from Canada and I speak French. «Système International d'unités» means "The International System of Unites". If you translate it word for word, it would be "System International a Unites". No, the "a" is not a typo, there is supposed to have an "a".

  • Tyler Roach
    Tyler Roach 53 minutes ago

    A priceless Fushigi ball? Cool :)

  • Zach Boersma
    Zach Boersma 3 hours ago

    The sexual tension is insane

  • Rob C
    Rob C 4 hours ago

    She's like, "It's priceless." No, Madam, my heart is priceless.

  • jeruman
    jeruman 6 hours ago

    thanx for using Danse Macabre as a background music ❤❤❤❤

  • Px90Pro
    Px90Pro 6 hours ago

    *drops it on the floor*

  • Marc.2377
    Marc.2377 7 hours ago

    This is genius. I hope they can change it.

  • Krayon. IllIIlIIlllI

    *forgets to turn off adblock*
    - not skippable 2minute ad appears

  • Jada Giles
    Jada Giles 7 hours ago

    *S P H E R I C A L*

  • john difrancisco
    john difrancisco 8 hours ago

    "Can I hold it?"

    GASTRO GAMING 9 hours ago

    why not use computers for that

  • Bushcraft1974
    Bushcraft1974 10 hours ago

    Without destroying the Silicon sphere how can they be sure there are no voids within it? When things get this precise my head starts to hurt!!!

  • Rieksfier
    Rieksfier 10 hours ago

    Priceless sphere placed on a highly unstable looking stand, placed on a block with barely enough surface area for it not to be knocked over, and she's worried about him dropping it...

  • Enoch Root
    Enoch Root 10 hours ago

    Have they never seen Kim kardashians ass?

  • Ezra Levino
    Ezra Levino 11 hours ago

    only 20M views?? Hahahahahahhahah I know how to get more. get a hidrolic press

  • Anon Emus
    Anon Emus 14 hours ago

    Proudly Made in Australia by the CSIRO (Commonwealth Science and Industrial Research Organisation). Us Aussies are not that stupid :)

  • JediFight
    JediFight 17 hours ago

    Pretty funny you can almost smell and taste how infatuated that lady is with this guy.

  • slad roznik
    slad roznik 23 hours ago

    and to think, it only cost more than a million euros... and I want one also... your taxes at work...

  • Mark's Wife
    Mark's Wife 1 day ago

    Wow it is a ball thing i am impressed

  • Francis Piche
    Francis Piche 1 day ago

    Why not just go back and measure water again in the case of damage to the physical objects?

  • Barley1312- Clash Of Clans

    I would have dropped it on purpose lol

  • Will Vaughan The Absolute Meme Kekker

    I don't even care. I just heard Dance Macabre in this so i like it.

  • Adam Martin
    Adam Martin 1 day ago

    What's the update on this? Did they adopt it?

    • Veritasium
      Veritasium 1 day ago

      +Adam Martin you should check out my recent vid on the American kg. And I have the final answer coming in the next month or so...

  • y y
    y y 1 day ago

    I don't know what your talking about.... the us has adopted the metric system

  • Aidan Holm
    Aidan Holm 1 day ago

    The roundest

  • Aidan Holm
    Aidan Holm 1 day ago

    No it is not

  • ZombyBryne
    ZombyBryne 1 day ago

    Want to know who's world's dumbest president pls ^^

  • ZombyBryne
    ZombyBryne 1 day ago

    Want to know who's world's dumbest president pls ^^

  • Matthieu JOLY
    Matthieu JOLY 1 day ago

    "from cradle to grave" =)> that was just perfect.

  • Stan Kormy
    Stan Kormy 1 day ago


  • Creth Haas
    Creth Haas 1 day ago

    why would any idiot give this video a thumbs down, I guess you could say they just are plain stupid.... freak's

  • Ty Palmer
    Ty Palmer 1 day ago

    How stoned was he when filming the explanation of the kilogram? lol his eyes...

  • Colin Alston
    Colin Alston 1 day ago

    gah, the offset audio balance

  • Mister Grim
    Mister Grim 1 day ago

    This would be a great steal for a thief.

  • Rayan Oliveira
    Rayan Oliveira 1 day ago

    dude looks stoned as fuc

  • MaddenGod Ben E
    MaddenGod Ben E 1 day ago

    1000mph fidget spinner vs world's most round object

  • Black_bomb
    Black_bomb 2 days ago

    idk why but when he picket it up it liked like it was a 2d sprite from a game a long time ago that allays faced the player

  • SupraLIFE
    SupraLIFE 2 days ago

    Ms.Katie is very cute x10^23

  • SupraLIFE
    SupraLIFE 2 days ago

    Ms.Katie is very cute x10^23

  • Mister J Westcoast
    Mister J Westcoast 2 days ago

    Homeboy looks baked😥😥😥😑

  • Trenchcoat1Sword
    Trenchcoat1Sword 2 days ago

    Petty classist bastards. Bring back the Grav.

  • Backyardmech1
    Backyardmech1 2 days ago

    The scientists calibrated its roundness to George Michaels butt.

  • The unknown XD
    The unknown XD 2 days ago

    You know what else is round dat booty ;)

    MANOFTHEMOON 2 days ago

    what weed there smoked? XD

  • David Warner
    David Warner 2 days ago

    I used to have a Marble that was pretty round!!! Wonder how much that's worth 💷💷💷💷

  • Ya Mum
    Ya Mum 2 days ago

    CSIRO = Australian :D

  • Miroslav Michlicek
    Miroslav Michlicek 2 days ago

    Just this week, I was deeply impressed by presentation of a physicist studiing mass of this silicon sphere, or more precisily mass of the surface contamination - silicon oxide, carbonous contamination and adsorbed water. They used superior state of the art surface diagnostics (XPS + XRR, both on a synchrotron), to get mass and its uncertainty with about 10 microgram presision (approx 10-8 relative error). Keep this really impressive work.

  • Gerkinjamjii YT
    Gerkinjamjii YT 2 days ago

    One of a handful of people. Wow you must have big hands.

  • ItThunderbolt
    ItThunderbolt 2 days ago

    My balls...

  • Gus Johnson
    Gus Johnson 3 days ago

    ooh, shinny, ooh CSIRO, ooh Australian.. hehe.. that country at the bottom..

  • Burak Baggins
    Burak Baggins 3 days ago

    Why silicon?

  • Ryan Kyojiri
    Ryan Kyojiri 3 days ago

    it looks like a fushigi

  • DomOskaBishop69
    DomOskaBishop69 3 days ago

    14. Meters apart???? Anyone like to explain that bit of nonsense???

  • Agent Office
    Agent Office 3 days ago

    so did you two get married by now

  • tizio caio
    tizio caio 3 days ago

    that kilogram isn't that important... if u see that all the "big k" are "contamintated" u can use others just measured objects to see how it was

  • MyNameIsMud
    MyNameIsMud 3 days ago

    Perky boonies? She wants him to fist her so bad.

  • Hayden Forest
    Hayden Forest 3 days ago

    My speculation and one of the most logical ones to why the weights changed would be hawking radiation

  • Enter Username
    Enter Username 3 days ago

    It's spherical! SPHERICAL!

  • SuperBearcats22
    SuperBearcats22 3 days ago

    So a few months ago on the ACT there was a passage about the kilogram and I got so interested in lost in the words that I forgot to answer the questions and I almost ran out of time.... all because I was like woah veratasium did a video about this!!

  • ProjectMachines
    ProjectMachines 4 days ago

    Well its now 2017 and we still rely on "Big K"

    ET THE BOY 4 days ago

    fake, he us not actually on a beach

  • GameAdmin
    GameAdmin 4 days ago

    Am I the only one that wants to walk in this place and scratch the smoothest object in the world

  • Red_Jacket
    Red_Jacket 4 days ago

    2:18 I'm a simple man... I see titties, I click like...

  • Rodrigo Velásquez
    Rodrigo Velásquez 4 days ago

    so, what happened? was the Kg redefined?

  • dobby240
    dobby240 4 days ago

    Iv just watched 2 videos I have subscribed to you because that's God Damn interesting

  • Danwolf15
    Danwolf15 4 days ago

    Imagine him dropping it...whoops

  • ISXOL 1
    ISXOL 1 4 days ago

    2:19 :D

  • Gary Pugh
    Gary Pugh 4 days ago

    my left nut is way more round

  • Peter Hall
    Peter Hall 4 days ago

    Ok, but the mass of the silicon 28 atom must be known, so why not mathematically extrapolate that out to the standard weight you want? Why do you need a physical object in the first place?

  • ChannelX24
    ChannelX24 4 days ago

    What's inside the worlds roundest object?

  • jordan gurgul
    jordan gurgul 4 days ago

    "The Earth's pretty round"? not heard of an oblate spheroid then Mr Science expert

  • Vytone Jr
    Vytone Jr 4 days ago

    I like how the comment section shows most people like to spout knowledge they learned from videos and articles rather than from an actual education

  • Andy 12 Daniels
    Andy 12 Daniels 4 days ago

    sili cone

  • Phantom Drums
    Phantom Drums 4 days ago

    Lebron K

  • Kimber Weston
    Kimber Weston 4 days ago

    This is stupid

  • - Vexations -
    - Vexations - 4 days ago

    Not rounder then my balls

  • turboboy1983
    turboboy1983 4 days ago

    Ugh, she's got glasses- and a ponytail...
    But, but... No! Glasses and a ponytail!
    Smokin' hot.

  • MR.Physics
    MR.Physics 5 days ago


  • Phil Chia
    Phil Chia 5 days ago

    how on Earth did the CSIRO get to do this?

  • anindya basu
    anindya basu 5 days ago

    Platinum iridium evaporation?

  • Max Dallas
    Max Dallas 5 days ago

    A real scientist would compare how round her boobs are to the sphere. I know I would have.

  • TheSpiikki
    TheSpiikki 5 days ago

    i disagree

  • Barrel
    Barrel 5 days ago

    Type "0" for your own blaster !!

  • Max Whitworth
    Max Whitworth 5 days ago

    He's in love

  • Nate Shonkwiler
    Nate Shonkwiler 5 days ago

    F u I'm an American!!!!!!!

  • sue celeste
    sue celeste 5 days ago

    0:34 Is he even rotating the sphere??? :V

  • Xploding-turtle
    Xploding-turtle 6 days ago

    Metric system is the best system

  • gingerbreadmanquan
    gingerbreadmanquan 6 days ago

    fact check; according to nasa the earth is not round, but rather an oblate spheroid

  • Meme hole Whomst've

    Why do all of the smart YouTube channels start with the letter "V"?

  • Steve Pants
    Steve Pants 6 days ago

    From a round object
    To SI Units
    To Kilograms
    To Water
    To platinum stuff

  • Munjee Syed
    Munjee Syed 6 days ago

    still no change to the kilogram definition but we are on the cusp of change

  • i_meow_sometimes GD - Guides - And more!

    Looks like you aren't even turning it!

  • Bogdan-Laurentiu Baltaretu

    Good thing the French didn't patented the SIU, otherwise it would have been SId'U, haha :D just kidding, love you all

  • Juma sayeh
    Juma sayeh 7 days ago

    just return to the original 1 liter of water at 4C degrees, here problem solved , now hand me my $1M.

  • SN1PERyan
    SN1PERyan 7 days ago

    i would drop it like it's hot

  • Simon Riley
    Simon Riley 7 days ago

    Well that makes it 3 roundest spheres in the world. The other 2 are in my pants

    SAMUEL SANTOS 7 days ago

    Is the kilogram unity already defined?

  • Carlos Soto
    Carlos Soto 8 days ago

    her body language was very obvious. lol

  • Nikhil Sharma
    Nikhil Sharma 8 days ago

    1 million Euros! Could have been spent on saving millions of starving animals around the world.

  • Vedika Bhatnagar
    Vedika Bhatnagar 8 days ago

    lol iMovie sound effects at grave

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