How We're Redefining the kg

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3 år sedan

In 2018 the kg will be defined by Planck's constant, not a hunk of metal.
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Special thanks to the staff at NIST who made this possible: Darine Haddad, Jon Pratt, Stephan Schlamminger, and Ben Stein.
Additional footage and animations by Sean Kelley, Jennifer Lauren Lee, and Frank Seifert.
I have been obsessed with measurement for a long time and I'm not sure quite how it happened. The world's roundest object played a role in this. I guess I'm just fascinated by how difficult it is to pin down a quantity like a kilogram. A physical object seemed like a good idea until the mass of the international prototype kilogram wasn't as constant as expected. These methods of the Kibble balance and silicon sphere have shown better precision than 20 parts per billion, making them superior to the old method. The agreement between Avogadro approaches
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Music from "ExperiMental1" by Gunnar Johnsén
Studio filming by Raquel Nuno

Lakshmi Narayana.k Narayana.k
Lakshmi Narayana.k Narayana.k 3 dagar sedan
Renan Goiana
Renan Goiana 13 dagar sedan
opa, então você veio pelo Umberto??
waki DL
waki DL 14 dagar sedan
My head hurts
mirat parmar
mirat parmar 14 dagar sedan
0:07 I'm at the National Institute of Standards & Technology in Washington D.C. and I'm trying to rob the sub-basement vault
Flickd Orion
Flickd Orion 17 dagar sedan
Dude, just buy a kilogram of bananas from the local shop and use it holy, why you gotta show your big brains using all of that physics and stuff
Yahya Saleem
Yahya Saleem 17 dagar sedan
I bit even my physics teacher can not understand this
That Guy
That Guy 17 dagar sedan
Makes sense...
Sean Hartung
Sean Hartung 17 dagar sedan
Second should have changed planks conference should have been set to 1 or Avogadro's number.
Sean Hartung
Sean Hartung 17 dagar sedan
Where is the force due to space-time gravity well converted to mass calibrated at? I know it's at earth's surface, but that equation should be different at almost another other location, from it's original location.
Elvis Björk
Elvis Björk 19 dagar sedan
1:10 Buuuut we don't know the speed of light, we know the speed of light after a reflection. Which makes it uncertain aswell;)
François Bergmans
François Bergmans 20 dagar sedan
Derek in 2017 : the speed of light is 299.792.458 m/s exactly. Derek in 2020 : do we really know the speed of light ?
Bejars318 21 dag sedan
Man, just show me the shiny ball
MustardIsMurder 23 dagar sedan
How do these scientists casually say all this stuff is "easy".
Shadow Rider clone
Shadow Rider clone 28 dagar sedan
OK... so... what is the new definition of kg🤔
Douglas Smith
Douglas Smith Månad sedan
Of course, this assumes the speed of light does not change over time.
Douglas Smith
Douglas Smith Månad sedan
@TheEmerald End Also, see: "The idea of light slowing down over time was first proposed by Professor João Magueijo, from Imperial College London and his colleague, Dr. Niayesh Afshordi, of the Perimeter Institute in Canada. Their paper was submitted to Astrophysics in late 1998 and published shortly thereafter. Unfortunately, the proper instrumentation necessary to investigate the CMB to search for clues supporting it, wasn’t available at the time. "
Douglas Smith
Douglas Smith Månad sedan
@TheEmerald End If the speed of light changes over time, then using the speed of light as a metric standard would raise issues. See
TheEmerald End
TheEmerald End Månad sedan
C measures light in a vacuum. Basically saying this is the defined max speed any object could go in a universe in ideal conditions.
Nathanael Niklaus
Nathanael Niklaus Månad sedan
Hey! I love equations and therefore this is one of my favourites! You've got some pearls on your channel. Thank you! Just a question, at around 7:00-7:12 of the video, you named all the constants except what the p value stands for. What was it again?
FrostDirt 28 dagar sedan
Just an integer
George Carlson
George Carlson Månad sedan
It all comes down to how accurately we can measure the second. Einstein and Heisenberg may have a problem with that.
Frank Chen
Frank Chen Månad sedan
but steel'z heavia den feathas...
Donavon Wewers
Donavon Wewers Månad sedan
why isn't it defined by the mass of a liter of water? Meter is already well defined and a liter is just 0.1 meter cubed.
veloc1tyTV Månad sedan
So the wiggly thingy is basically a very precise but expensive weight scale. Got it!
Gold Winger
Gold Winger Månad sedan
Hmmmmm . . . sounds like a lot of smoke and mirrors. To measure this, we have to measure that but we can't measure that precisely because we have the other thing to measure.
N Voss
N Voss Månad sedan
brilliant expanation
D Seb
D Seb Månad sedan
Your gesticulate hands šuld be cut.
Muhammad Nada
Muhammad Nada Månad sedan
Who said that the speed of light is not changing? If the space itself is changing wouldn't that suggests that what ever in space is changing!
Justin Sander
Justin Sander Månad sedan
Right this moment some one is working on proving that lights speed might be variable and not constant.
Chitra Singh
Chitra Singh 2 månader sedan
Some feedback - 3:55 the current is adjusted until (not- "the weight is equal and opposite to the electromagnetic force" since weight is the constant, rather:) electromagnetic force (is adjusted) on the coil till it is equal and opposite to the weight. Also, it's unclear, in the velocity mode (@6:00) you balance the voltage using Joseph's injunction, to what? The earlier reading when in weighing mode? Really appreciate it. Just dint get these bits
Chitra Singh
Chitra Singh 2 månader sedan
Veritasium, that's a brilliant job in explanation!! What we need is a children's book explaning this, so young students learn to appreciate what 'exactly' are we speaking of when we talk about physics ( the basic building blocks), instead of just learning to solve equations. Will work wonders for many!!!
mc Muck
mc Muck 2 månader sedan
4:11 Hmmm°?°... i'd have thought that the hardest part would b 2 determine the gravitational pull @ the x-act spot where the apparature is located... & its momentum over time as earth interiour processes may alter it or 4 x-ample the moon swings by. Thinking all this i'd say: Let's define the kg in refference 2 the Schwarzschildradius (8)
Edge 2 månader sedan
5Head Clap indeed
paul zapodeanu
paul zapodeanu 2 månader sedan
Ok, so now we've defined the basic measurement units in terms of physical constants. But how sure are we of the constance of these constants? Are they fundamental, or do we have a theoretical understanding of how the came to be what we now find them to be? Are they likely to change on the scale of the lifetime of the Universe.
Rishil Shah
Rishil Shah 2 månader sedan
So i watched this video today.. and the kilogram is again redefined in terms of plank constant and speed of light in vacuum by relating E = mc^2 & E = hv where the symbols have usual meaning . Not that anyone asked but i think this is the last redefination of 1 kilogram.
Alex Landherr
Alex Landherr 2 månader sedan
Annoyingly Avogadro’s Number was updated/changed shortly after I took an exam in stoichiometry...
Carl Hansen
Carl Hansen 2 månader sedan
Was the definition of Avogadro's number on your exam? Because for what they expect you to know in introductory Chemistry, I don't think they expect you to be more precise than the 4 significant figures you memorize.
Philip Malaby
Philip Malaby 3 månader sedan
Twist ending. One kilo is now equal to one pound!
kuessebrama 3 månader sedan
All of this for 1 kg :D Nice
44 er
44 er 3 månader sedan
simple: how much light does it need to kg
Matthew Vicendese
Matthew Vicendese 3 månader sedan
The measure of distance is circular. Yes the speed of light is a naturally occuring speed, but breaking it down into chunks of time ... a second is defined by humans.
Marshall Bryan
Marshall Bryan 3 månader sedan
Dis so cool fr
Marshall Bryan
Marshall Bryan 3 månader sedan
Seema Kushwaha
Seema Kushwaha 3 månader sedan
6:30 oh okay
Hosan Cinta 6
Hosan Cinta 6 3 månader sedan
I dont understand any of those words, my brain can't handle it, but idk why but i still love watching this kind of video, even tho i dont understand it lmao
Matías vf
Matías vf 3 månader sedan
your series on the kilogram saved an essay I had to do for tomorow :) thank you
Vebjorn A
Vebjorn A 3 månader sedan
" The kilogram is dead. It remains dead. And we have killed him/it" - Nietzsche
Lumberjack king the great
Lumberjack king the great 3 månader sedan
Me pretending to understand this
Lumberjack king the great
Lumberjack king the great 3 månader sedan
1:04 which is the same as the bar
Unknown 3 månader sedan
Me:watching this video My brain:.404brainnotresponding
Calculando Com Moshe
Calculando Com Moshe 3 månader sedan
Looks complicated man but i hope it works I am going to tell my dad about the circular fringes he likes this stuff. 😂😂😂😂😂
Felipe Soares
Felipe Soares 3 månader sedan
Vim pelo Umberto Mannarino
Automata GX
Automata GX 3 månader sedan
Nothing occured of your happening in youtube. No knowledge with your videos
Luis Xiao
Luis Xiao 4 månader sedan
Raquel Magalhães
Raquel Magalhães 4 månader sedan
Vim pelo Umberto Mannarino 🤗
Kelvin Thiago
Kelvin Thiago 4 månader sedan
1mberto me trouxe aqui, kkkkkkkkkkkk
Gustavo Medeiros
Gustavo Medeiros 4 månader sedan
Vim pelo Umberto Mannarino
Manoel Lucas Lopes Reis
Manoel Lucas Lopes Reis 4 månader sedan
1berto kkkkkkkkkkkkkkkkkkk
Calculando Com Moshe
Calculando Com Moshe 4 månader sedan
Makes no sense because there is information missing. For example how can you find the voltage without knowing the charge value. I think Avogadro constant depends on the electrons charge , which is not clear to me how they “calculated it”. I think you should ask the electrons for their numbers, because the deeper you go the more ridiculous things you will have to invent to complement your theory. People just love these proofs.
Calculando Com Moshe
Calculando Com Moshe 4 månader sedan
I just don’t know how they define physics theories anymore they are putting out so much secret theories that no one understands.
Bunny Bro
Bunny Bro 4 månader sedan
Y'know, it's gonna suck when humanity eventually and inevitably destroys itself and all this knowledge is gonna have to be painstakingly rediscovered or forgotten by those who come after us
Robert 6 månader sedan
How come we don't redefine the meter to a decimal of planck length?
Zainab Ahmadnagarwala
Zainab Ahmadnagarwala 6 månader sedan
The kilogram is not redefined sorry
Zainab Ahmadnagarwala
Zainab Ahmadnagarwala 6 månader sedan
It didnt worj
vmurad 6 månader sedan
The only thing I could assimilate from this video is that it's pretty funny to say Josephson junctions.
Nikioko 6 månader sedan
Avogadro's number is closely related to Loschmidt's number. The Avogadro constant is the number of particles in one mole, the Loschmidt constant the number of particles in 1 cm³ of an ideal gas at standard conditions (273.15 K, 1013.25 hPa). The factor between those constants (6.022 x 10^23 mol^-1 and 2.687 x 10^19 cm^-3 is roughly 22,414 cm³/mol. So, one mole of an ideal gas at standard conditions has a volume of roundabout 22.4 l.
Nikioko 6 månader sedan
Originally, the metre was defined as 1/10 million of the meridian from the north pole over Paris to the equator. And that is slightly longer than the second pendulum which is also said to be about 1m long.
Richmond the Goth
Richmond the Goth 6 månader sedan
Is that measurement of a meter by the speed of light using light in a vacuum?
Carl Hansen
Carl Hansen 2 månader sedan
Yes. The speed of light in anything other than a vacuum, is a red herring in this context.
cvele cvelevic
cvele cvelevic 6 månader sedan
How much speed of light weights?
Fadhli M.T
Fadhli M.T 6 månader sedan
Send help. My brain hurts. :(
Warmpereer 6 månader sedan
8:33 My Physics class in the nutshell
ivan schafeldt
ivan schafeldt 6 månader sedan
yeah, only the speed of light has never been measured at the same speed twice, ever.
hypehuman 6 månader sedan
He keeps saying "accurate" where "precise" would be more accurate.
Nissim Deij
Nissim Deij 4 månader sedan
you mean ... precise? ಠ_ಠ
Paolo Pantaleo
Paolo Pantaleo 6 månader sedan
BTW, there is no proof that speed of light doesn't change with time, right ? :D
Jpzorz 6 månader sedan
And how much does that balance cost cuz I wanna use it to put a very precise mass of parsley into my mom's spagetti
Archangel 6 månader sedan
So essentially the ambiguous consept of weight as kilogram is being redefined to be based on another ambiguous concept which is frequency which is based on seconds? They would better of tie all concepts of space/time based on a single phenomenon that is either unaffected or barely so in near any conceivable situation so that it can be used as a constant of which the meter and second would be a mere multiplication of. Because as of right now the second is defined based on the rotational speed of earth making a second 1/(24*60*60) of a day. But the thing is the earth rotational speed is by no way a constant.
Archangel 4 månader sedan
@Ridwan Syah Maulana my bad. I only called it ambiguous because of the reason I explaned already. But you totally right. I was just unaware that it was figured out already. My missconseption is also explaned in the wiki XD
Ridwan Syah Maulana
Ridwan Syah Maulana 4 månader sedan
1. The standard is not an ambiguous concept. 2. One second is not 1/86400 day. One second is 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. And that is constant.
Zephyr3 6 månader sedan
That’s a big ass elevator
moo mooerson
moo mooerson 6 månader sedan
he won't pin me
Jacob Wiren
Jacob Wiren 6 månader sedan
Why is the meter so retarded? Just make it 1/300,000,000. Is there a good reason for it not being this other than politics?
Ridwan Syah Maulana
Ridwan Syah Maulana 4 månader sedan
Oh btw, we already have the definition. From : The kilogram is now defined in terms of the Planck constant, h, which has been measured with extraordinary precision in recent years. Its agreed value will be set as 6.626,070,15 × 10-34 kg m2 s-1, with researchers able to make precise mass measurement using equipment such as the Kibble balance.
Ridwan Syah Maulana
Ridwan Syah Maulana 4 månader sedan
1. There is no politic in it, just the pursuit of knowledge. 2. 1/300.000.000 of what ? Oh also, THAT is a CONVERSION, not DEFINITION. We already have conversion standard for it. 1 Kg = 1/1000 tonne = 1000 grams = 1e+6 mg. As the video said, we need to define it using constant properties of the universe to avoid any error. 3. Meter has no bussiness here. Meter is a unit of measurement for length. This video is about mass. 4. Today, your US Imperial System (or Customary Measurement System as the Government calls it) IS DEFINED BY the Metric Standard (which the kilogram is part of), So any uncertainty in metric will affect the imperial.
De Mus
De Mus 6 månader sedan
What??? Americans have to redefine the Kg???? You have no idea what it is, what normal units are. You and your inches, feet, ounces, pounds, etc. All these crooked units which make no sense at all.
ElitheGredler 6 månader sedan
Are we really sure that the constants of the universe don't change?
GH1618 6 månader sedan
ElitheGredler - Physical constants are different from mathematical constants. If measurements show them to be constant within experimental error, then they are constant for practical purposes. A few physicists have hypothesized that speed of light may have slowed down since the Big Bang. There is no evidence of that, but even if it were true it would affect only cosmology, not units defined using the speed of light.
Roozyj 6 månader sedan
Up until now, I was able to understand almost every video of Veritasium I watched, but this goes waaaay over my head. Maybe because It's about electricity
B L 6 månader sedan
Great episode but the plug at the end is problematic. Pinker is not a historian and the data set he uses for his "scientific" approach to human history is garbage. Historians think he should stick to his own subject rather than ranting about things he doesn't seem to understand. Historical sources are not at all reliable for making those types of broad-sweeping generalisations.
schroeder1112 7 månader sedan
I am quite happy i don´t have to learn this definition in physics class and could stick with the old definition. So this new definition alone could be enough for a single exam.
Henry Teng
Henry Teng 7 månader sedan
why not redefine with the atomic weight of a proton, that's constant, right?
GH1618 6 månader sedan
Henry Teng - It is not enough to have an abstract definition. You need to be able to make physical representations of the standard mass. How would you do that?
snaplash 7 månader sedan
I assume they'll build more than one balance in different parts of the world. use them to calibrate physical mass samples, then bring those together and compare them to prove it all works. (And if they don't match?)
GH1618 6 månader sedan
snaplash - That was done as a condition of adopting the new standard.
Karya 7 månader sedan
So whart's eviah now? A kilogramme of still or a kilogramme of feadehs?
Sean McFarland
Sean McFarland 7 månader sedan
But... the speed of light has been found to be changing. What now?
Çentoé 7 månader sedan
Mr. Sean Bean It hasn't though
Otto Kauppinen
Otto Kauppinen 7 månader sedan
Speed of light isn't allways the same, it depends on the point of view.
XtreeM FaiL
XtreeM FaiL 6 månader sedan
Otto Kauppinen Wrong. It is constant.
Dennis Bautembach
Dennis Bautembach 7 månader sedan
what's wrong with the water-based definition?
GH1618 6 månader sedan
Dennis Bautembach - It is not possible to apply with high precision.
guerrerosaurio 7 månader sedan
I'm not that smart but I'm smart enough to tell that the KG shouldn't be defined in a country that doesn't use it.
GH1618 6 månader sedan
guerrerosaurio - The United States uses US Customary units and SI units, not Imperial.
XtreeM FaiL
XtreeM FaiL 6 månader sedan
guerrerosaurio Us does not use stones or fathoms, so it is not imperial.
guerrerosaurio 6 månader sedan
@GH1618 but they mainly use the imperial system
GH1618 6 månader sedan
guerrerosaurio - Which country would that be? The United States is one of the original members of the Convention on the Kilogram.
Physics Concepts
Physics Concepts 7 månader sedan
Sir can you please make video explaining how the resistance measured is related to plank's constant. This will complete the explanation of this beautiful video.
Aniket Narvekar
Aniket Narvekar 7 månader sedan
I understood everything he said and then 2 sec later I forgot everything how does that work
Mārtiņš 8 månader sedan
Hope soon everyone get this thing in kitchen.
GandWizard 8 månader sedan
The people working here do very invaluable work, but wow, they have to do it in the most depressing workplace in the world 1:53-1:59. It's like a Half-Life level without enemies.
Faire Play
Faire Play 8 månader sedan
I didn't really understand much like I know what you mean, but I really just like how you talk and I like listening to it while doing something. The talks and your voice are soothing, really
Smarty 8 månader sedan
First it was 2014, then 2015, now 2018 lol.
megamorran 8 månader sedan
I thought a kilogram was just a liter of water? At room temp, couldnt you just decide a precise temperature and call it a day?
GH1618 6 månader sedan
megamorran - You cannot measure water with sufficient precision.
Çentoé 7 månader sedan
megamorran No because it's useless for measuring literally anywhere but one specific atom
GH1618 8 månader sedan
Now, how do you make a physical kg from this reference?
GH1618 6 månader sedan
Never mind. I found a better description of the Kibble scale.
RakeSh To
RakeSh To 8 månader sedan
Then if u f on the moon, what is ur definition of Kg and how u measure things by that big complex machine. Or U can simply keep that 1kg metallic measure in ur pocket measure things...
XtreeM FaiL
XtreeM FaiL 8 månader sedan
RakeSh To Definition will be exactly the same. Mass does not change.
Alfa101 9 månader sedan
now you yanks (although you certainly DO NOT look like one) need to stop that horrible glottal stop and constantly letter dropping, and do use the coma to separate DECIMALS not thousands... Oh! and also stop spreading your viruses!
GH1618 6 månader sedan
Alfa101 - We are certainly not going to change the mark between whole numbers and decimal fractions. Using a comma there is the goofiest thing Europeans do, in my opinion.
Çentoé 7 månader sedan
Alfa101 There's a thing called dialects bud.
gmax876 9 månader sedan
I used to think I wanted to be smart, I am now convinced; I just want to be rich.
gmax876 8 månader sedan
@ggzh a Argue With Everyone I imagine rich people have different problems to solve, but that's what money is for.
ggzh a Argue With Everyone
ggzh a Argue With Everyone 8 månader sedan
@gmax876 Its harder with a lot of money.
gmax876 8 månader sedan
it's pretty hard to be happy without money.
ggzh a Argue With Everyone
ggzh a Argue With Everyone 8 månader sedan
From someone that does not need more money and as someone that understands more than most people he knows: Its better to be happy than to be rich.
Kunal Kumar
Kunal Kumar 9 månader sedan
There's Still Very Little Fraction Of Errors....
Jo Momma
Jo Momma 9 månader sedan
How can you compare a theorem with any guessing any psychopath scientist guesses with his bogus theories ? You talk a lot but you say nothing stupid moron
Atul soti
Atul soti 9 månader sedan
I am stuck at measuring g with that precision.
The kg is dead, long live the kg
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