How We're Redefining the kg

In 2018 the kg will be defined by Planck's constant, not a hunk of metal.
Try a free book from Audible for 30 days ve42.co/audible
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
Special thanks to Patreon Supporters:
Tony Fadell, Donal Botkin, Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen
Support Veritasium on Patreon: ve42.co/patreon
Interferometer video by TSG Physics: • Michelson Interferometer
Music from epidemicsound.com "ExperiMental1" by Gunnar Johnsén
Studio filming by Raquel Nuno

[@1lamafarmer]

It's a good thing they went with the Plank's Constant in the end. I've weighed loads of avocados and none of them were close to a kilogram.

[@andersjjensen]

Ba-dum-tsss! :P

[@xGOKOPx]

I hope the plank they've chosen weighs a kilogram tho

[@philipptielmann]

and the avocados also weigh differently and change their mass a lot over time!

[@MinhiNug]

You need to use Avocado’s number

[@gallium-gonzollium]

@@MinhiNug or Plank’s constant

[@smartereveryday]

I appreciated the giggle at the end. The guy basically said "solve this simple algebra equation and redefine the two fundamental units of ALL OF PHYSICS".

[@odin_3]

Hello

[@DustyyBoi]

@@odin_3 Yes

[@kumarsrijan8377]

@Mukund Ranjan Tiwari yes you may want to learn about what the founder of wolfram alpha has to say about it. Look for his ted talk

[@mikaylamerna62]

Like what my physics teacher used to say the physics equations are simple math...

[@camplethargic8]

I'm pretty sure I had this guy for high school physics 8:23 - mumble mutter something-or-other (very fast and in a difficult to understand accent), "simple -don't you see, dummkoff?" 🤔

[@Zorgongola]

Hey Veritasium I was part of the team working with Bryan Kibble on the NPL mkII Kibble Balance (aka Watt Balance, aka Moving Coil experiment) between 1991 and 2000. Firstly I'd like to congratulate you on a great video. It's not easy explaining this elegant but complex method of redefining the kg and you guys did a good job. One thing to possibly add is the importance of keeping the magnetic field constant. Both weighing and velocity measurements are not quick and are conducted over a long time period. Back then it lasted over an hour, and the field strength is highly susceptible to temperature changes, so keeping the large magnet at a constant temperature is imperative. I worked on the NPL system and we managed to keep the temperature drift down to a millikelvin or two over the duration of measurement, usually overnight.

[@idjles]

How do you measure g without knowing what a kg is? this seems circular.

[@raymondo737]

If I understand your question correctly, I think you are mistaken. The "g" in the equation is g as in "Gravitational acceleration", not g as in "gram". It's measured in m/s^2. The video at 7:31 explains how they determine the local value of g with very high accuracy.

[@raymondo737]

Hello Robin, My mind boggles at how we've improved accuracy from measuring in sticks, stones and body parts to tiny fractions of fundamental constants. Also, I find it poetic that we use equipment that needs a crane to lift and assemble to perform measurements so sensitive, that would be affected by the operator's kids changing the TV channel at home.

[@andrewm9425]

@@idjles you measure the free-fall acceleration due to gravity. they do that by dropping a reflecting cube down an evacuated pipe and using a laser to measure the acceleration.

[@braveecologic2030]

I agree from an external perspective too

[@smortboi1320]

No one: Bryan Kibble: “I want to weigh myself with *electricity”*

[@donottrustanyonelol]

i understood none of what Ver just said but *yes yes yes yes*

[@thehouseofcha1nsaw_]

Isnt that how most scales work anyway? I think Kibble was thinking more like "bro, gravity be lackin"

[@trun_k]

One Balance to rule them all, one balance to define them. One balance to standardise them all, and into light forever bind them.

[@rydaddy2867]

That's beautiful...needs to be on a sticker stuck to the side of the Kibble Balance.

[@pizzamannetje79]

RyDaddy i agree, perhaps with "into the light" replaced by "into Planck"

[@Theraot]

Oh no, the sticker is gonna screw the measurement

[@fadyel7946]

lol

[@khadija7530]

Ash nazg durbatulûk, ash nazg gimbatul, ash nazg thrakatulûk, agh burzum-ishi krimpatul.

[@smartereveryday]

Another thing.. I thought the fact that you've locally mapped g in the room was FASCINATING.

[@veritasium]

+SmarterEveryDay yeah, I thought that was fascinating- not only did they have to map it, they then had to calculate what it would be at the center of mass including the influence of the balance itself

[@kuroshite]

Hi Mr. Potato

[@chuckborris804]

How crazy is that?!! That's an insane amount of precision. Just mind-blowing.

[@moos5221]

@@chuckborris804 Imagine doing that for the USA measurements like cups, tablespoons and handfulls.

[@edydaou]

Well, the 2 most channels I watch are here @SmarterEveryDay and @Veritasium. when are you doing an episode together?

[@yuvneesh]

Watching this on May 20, 2019. SI units have been officially redefined today, kg is defined by Planck’s constant.

[@bhupendrasingh8242]

You know what I hate Plank's Constant

[@elendilion]

@@bhupendrasingh8242 and the Planck's constant hates you.

[@Milesco]

​@@elendilion : That's right. A team of scientists from the National Institute of Standards & Technology went to a local Home Depot and took a random Planck of wood off the shelf and measured the weight, divided that weight by Planck's constant, and that became the basis of the new kilogram.

[@makc3887]

The official day has come.... Today kilogram definition is changed

[@JamBos11]

the kilogram is now the energy of a gamma-ray photon which does not exist, which cannot be produced, and which is completely 100% fictional and has a wavelength which is approximately a million times smaller than the width of a quark. What does that say about the level of scientific development...? Not something science should be proud of.

[@eggue9598]

@@JamBos11 Explain?

[@JamBos11]

@@eggue9598 the kilogram's redefinition equates the mass of 1kg to the energy of a gamma ray which is so energetic that has a wave length a million times smaller than the smallest matter particle present day physics has concieved - the quark. this gamma ray photon is so energetic that radiation of photons with that same frequency can never be produced on Earth. it is a fictional photon, that humans cannot experiemce, produce, interact with, etc.

[@eggue9598]

@@JamBos11 just because humans can't intact with it doesn't mean it does not exist

[@JamBos11]

@Eggue, but it does mean that it doesn't exist for humans because humans cannot produce it (too much energy - 20 Mtons of TNT equivalent per photon) or measure it (no equipment to measure such radiation), and if humans were unlucky enough that the planet gets exposed to radiation of such photons passing by, each photon from that radiation will deliver a blow over 1000 times larger than Heroshima.

[@fizizy6415]

5:00 Yes, I can definitely see why they call it the "Watt", because that's what everyone says after you explain it to them.

[@N3G4T3]

Fizizy Or if you go back to school and study physics it'll make sense.

[@msolec2000]

I only know that Watt's on second. :P

[@noname-sg6qx]

VI=P, P= power, unit for power is watt

[@NikhilTawde]

nice one

[@lachlansutcliffe4308]

Fizizy ahahahha lol good one

[@conure512]

R.I.P. the 1-kg mass in France. You'll be remembered.

[@toucaninterieur8011]

#dicksoutforthekilogram

[@rojirrim7298]

Parrot-hD Actually those cylinders will probably still be used. They won't be used as a definition anymore, but as a pattern. You can't have a Watt Balance on every laboratory, what they do is send their instruments to a place where these will be calibrated, and for the calibration they will probably still use the cylinders because of sheer convenience.

[@mkb6418]

Well it was time. All other constants are constant, it is time for kilo

[@danilooliveira6580]

Gabriel, actually they will most likely make new weights instead of changing the ones they already have. the mass in France will probably end up in a museum

[@pizzamandhx]

But they'll be remembered as they should be: in a museum, for the value they contributed to humanity. The prototype kilograms helped put people into space, make metal ships that can float in our oceans, helped us determine Planck's Constant. They have been immensely useful. We're graduating to something better, moving on as a species. Aren't all of these good things?

[@shadowfall2011]

Your videos are beautifully made, entertaining, and wholesome. Thank you! You can see the labor of love that goes into them.

[@observingrogue7652]

I couldn't stop smiling through this whole thing. My face hurts. As an amateur Electrical, Mechanical, and Structural Engineer. Just seeing what it takes to maintain the consistency of measurements, is really interesting & exciting to me. Thank you, this channel, for showing me this. And I thank the scientists doing that.

[@harshachoudhary7847]

''Derek changing the world, one kilogram at a time''

[@JellybellyWaffles]

One kilogram at a time? How long would that take?

[@agioiutdrdgfyfyfhgky]

JellybellyWaffles that depends on the rate at which the kilograms are being changed.

[@nikhildrogbacena]

JellybellyWaffles well, assuming time here means a single moment (1 second (give or take)), it would take 10^24s to change it entirely.

[@paletreker]

+JellybellyWaffles ask vsauce

[@SidekickTrail]

Braden Krause well time in the S.I(international system)is set as 1 second(s) so one can only guess a second

[@James__123]

4 years of my physics degree later and I'm still like "ah yes I know some of those words"

[@emgb1]

4 years of your physics degree later and you can start again at the beginning because all your calculations are now false.

[@JohannaMueller57]

wait, 8 semesters of physics only last for knowing some of those words? :-o

[@AlqGo]

University nowadays = all about degree certificates. Genuinely skilled graduates are those who invested countless hours teaching themselves cause Uni courses are typically not great in imparting knowledge that lasts long in the brain.

[@youssefmousa2830]

because that is algebra not physics

[@chrisdock8804]

... You should really know most of this stuff. Maybe not Josephson Junctions or Quantum Hall but hopefully you would have seen those in a Lab. Everything else is first year stuff though? If that.

[@LonDiffenderfer]

Although I understand the need to change the method of defining the kilogram (thanks to you), I still have no idea how it is done. Those calculations are still currently beyond my abilities to comprehend. I often have difficulty grasping all of what is said in your videos, but I still appreciate that you produce them for our benefit. Thank you for your time, effort, and desire to educate us. :) Very best to you and yours!

[@naufalmEZa]

The fact that you watched this still, is heartwarming.. Really, you gotta see where you're lacking to start learning.

[@pyropulseIXXI]

You should read some books; this is at basic algebra level, which is 6th grade level, I would say. Our education system does a good job in making easy things seem hard, by not properly teaching them. For instance, I learned calculus at 13 on my own, just from reading a textbook. And yet, they don't teach proper calculus until college. Therefore, the system is stunted by at least 6 years

[@jimmysyar889]

@@pyropulseIXXI wow you must be very smart

[@ontime.]

​@@pyropulseIXXI Bruh this is physic, not algebra. Veritasium talked about p, and any of that formula, and that gravitational thingy which idk how can they came up with that idea. I only understand the basic mgv and VI the rest about planck & magnet thingy not really stuck in my head.

[@salimbouhezza5473]

my head after 35 seconds: INTERNAL SERVER ERROR 500 NO BRAIN CONNECTION DETECTED

[@AnhThuNguyen-zz2hm]

Me: huh Most people: *INTERNAL SERVER ERROR 69* *INVALID FORMAT*

[@Tool8x]

The kg is dead, long live the kg! All hail the kg!

[@gnochhuos645]

SEIZE THE MEANS OF MASS

[@woodzy136]

First the weight, then the height, then THE WORLD

[@danielw832]

Vietnam Mapper By any Mass Necessary

[@MrtinVarela]

You could say it was... mass murder

[@cheat200]

WE MUST MASS IMMEDIATELY AND STOP THIS MASS GENOCIDE!

[@hassanallama9376]

drugs dealers are going back to school because of this

[@SpydersByte]

best comment

[@dirtyp4670]

One meter of skunk please.

[@Chunkboi]

“Could I get 28.35g of weed?”

[@its_kamau]

hahaha they better go back to school or business is over

[@akashpatel-cb1dq]

You described it so beautifully.I understood the head wrenching process to define the units using the best available methods.

[@IAmTheRealUsopperGoddamnit]

Great video. I was having a hard time understanding it from the basic definition from my textbook and wikipedia, but after watching the process behind it and the equations involved it is crystal clear now.

[@Dodo-rb4zf]

How about we eliminate Galon, Pounds, Foot, Inches?

[@Boz1211111]

Nah why would you simplify the world if you can screw it up even more

[@sparkyenergia]

Trump is probably working on that.

[@GeminiWoods]

Trump is "working" on a lot things. Doesn't mean it's actually getting done, or making any progress.

[@my3dviews]

The U.S. has its own gallon (3.78 litres, vs 4.54 litres), which is different than the imperial gallon used in most other countries (that don't use metric or use both).

[@wundsalz6831]

Why would you want to discard the superior imperial system in favor of this overly complex SI-nonsense? Being able to measure mass, weight and money using the same unit is convenient.

[@SiddheshNan]

brain.exe has stopped working

[@nagajoj]

SiddheshNandurkar I feel you bro.

[@conexant51]

Yeah, you should delete that file permanently.

[@DarkLink1996.]

Инесса Осипова I have more than a few questions.

[@parodoxis]

Stop running it on Windows

[@BluntforceJ]

nice to see people who are not like "this is easy to understand if you know basic high school science" this dont look or sound basic to me

[@schroeder1112]

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.

[@peppermintmiso4341]

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

[@JOELwindows7]

R.I.P., Elder Kg, 1799-2017 You'll be missed.

[@supertaakot]

Hey that's actually a nice name for the platinum-iridium weight in Paris xD HAIL ELDER KILOGRAM

[@JohnSmith-kt3yy]

TheOneAndOnly Tako ALL HAIL ELDER KILOGRAM

[@walkinmn]

Joel Robert Justiawan well according to the video, is not death yet, may be it can survive 2017

[@MrMineHeads.]

Joel Robert Justiawan actually it should be 2018

[@E1craZ4life]

There are still going to be kilogram replicas around even after the kilogram is redefined; it'll just be easier to track fluctuations in mass.

[@RamiShreds]

I will have to come back and watch this video again when I am not high

[@NikhilTawde]

I wasn't and still couldnt get most of the video.

[@NonDelusional74611]

RV -- Sometimes, a small high helps.

[@phillaboody260]

It only makes sense when you are high

[@RiseWithTheFallen222]

Fucken amen brother

[@royalesniper3092]

fr 😂

[@chitrasingh44]

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!!!

[@matiasvf2520]

your series on the kilogram saved an essay I had to do for tomorow :) thank you

[@Hatch61]

I will not lie, and tell you that I understood everything that you just said, but enough to understand that an amazing amount of work happens behind the scenes to provide the folks like me that use these standards daily to be able to rely on them being constant. I enjoy your channel.

[@Wave1dave]

I'm doing my semestral project on this topic and I have to admit it's really crazy! That amount of work they put into this is just astonishing. Everything has to be perfect, everything has to be measured precisely many times and when they are done, they improve the Watt balance and have to start all over again.

[@xxportalxx.]

Well, unless you're a physicist you probably don't rely on this, considering that all of the measuring equipment that anyone uses is going to be off by magnitudes more than those 'innacurate' standard weights they spoke of at the start

[@Kraigon42]

This kind of thing is what restores my faith in humanity.

[@christianosanjo]

Hi ate you still active?

[@christianosanjo]

I mean *are*

[@Kraigon42]

Define "active"

[@eljahihamgottin4540]

@@Kraigon42 alive

[@splenden2235]

Do you still have faith in humanity?

[@omhekde9033]

Its true now! Commented on 16 Nov 2018

[@arijitpalit2756]

Wooo hoooo

[@inpinksuit]

GG

[@allejandrodavid5222]

5 years ago

[@avici0182]

Watt?

[@falsonaga]

Volt you don't understand

[@sideoutside]

Cause.

[@billyjoejimbob75]

That joke was lame, scAmpere off.

[@AnhThuNguyen-zz2hm]

I Resist the urge to laugh.

[@darwinvironomy3538]

@@AnhThuNguyen-zz2hm Watt? i thought it's MASSive object with GRAVITional acceleration in a VELocity.

[@kcwidman]

The kilogram is being redefined in the United States? How ironic.

[@arda9437]

Kai Widman the us got roasted by kg

[@Hauketal]

Kai Widman Not only, but also in the US. See the overview at 8:20 for some of the others. I can't identify all, but at least France (LNE), Japan (NMIJ), and Germany (PTB) are involved. This is for the balance only, others must be added for Avogadro counting. It's a worldwide cooperative effort, by about everyone having enough money to participate.

[@WarheaddVids]

My phone got stolen so?

[@sparqqling]

Indeed the Americans already converted, the 9mm is the most used.

[@WarheaddVids]

My phone got stolen it doesn't matter

[@TheLittleGuy1]

Video on the Quantum Hall Effect ?????

[@veritasium]

maybe at some point...

[@mesaprime4368]

TheLittleGuy frost prime, what are you doing here?

[@TheLittleGuy1]

nearly mastery 22 got to rep my favourite game

[@ajayrawat9317]

Veritasium which nextflix series were you talking about ? I would really like to watch that. Also Digits was amazing

[@BrillouinBoi]

The Quantum Hall effect is crazy complicated. You need grad physics background to really understand even it's simplest integer form. More complicated fractional forms are still being researched to this day. Really cool though. I hope Derek is up to the challenge.

[@crisrose9707]

I am glad you went into as much detail as you did since even though some might not know everything that you talked about, if you skipped it all then nobody would have understood it whether they knew what you were talking about or not :)

[@movax20h]

This is brilliant. The gravimeter doesn't even require calibration per se. It needs to be only traced back to distance and time, not easy to do using frequency standard and laser interferometry. Brilliant.

[@koosnaamloos4291]

My physics teacher literally recommended your channel to our class, guess who's watching your videos now? Edit: As a VWO6 student I should know how to speak English XD, dutch people will understand

[@averyshaham1697]

Koos Naamloos Your teacher 😛

[@mistertheguy3073]

Koos Naamloos hoe heet je leraar?

[@Henry_Jr_Watsson]

Mattie, paas me je msn dan

[@blzahz7633]

Jack Bauer? Did.. did I win?

[@RAiNfORAiNbOW]

Koos Naamloos Only you

[@kcwidman]

Even though I have only taken a basic level high school physics course, I still really enjoyed the use of the equations to illustrate the complicated nature of this problem. I tried to follow along, and I'm sure I failed, but I got the gist of it.

[@megatrix500]

I mean, having taken all of the high-school physics lessons and having touched on college physics too, I can certainly tell that those formulas were quite simple for something as huge and important. Still not SO simple, and also they're used with high-tech measurements, so not at the reach of any physicist, but it's really cool that something as important is also so understandable.

[@chandel9449]

Kai Widman Everything he did with the math is basic Algebra. No physics knowledge is needed to see what is happening. If you want to know more about why these particular formulas work, you need knowledge of physics.

[@kardo7837]

I've only taken my high school courses, and I understood the whole concept easily after watching it twice

[@robertginsburg8113]

As a kid who grew up with public education and working parents I just wish videos like this would have been around when I was a kid. Not that I have any complaints because I don't but I can only imagine that my life would have probably taken a much different path. Physics is such a fascinating subject.

[@poissondesruisseaux3650]

Thank you! I was looking for that video to explain me why h was better than the mass of carbon 12. Two thumbs up!

[@Biochemguy]

I always knew that the Kilogram would be made into a true constant similarly to how the meter and other units of measure have been. This solution is just so elegant in its simplicity (despite not being simple to carry out) that I find it beautiful.

[@yepok5120]

you spelt metre wrong

[@EGL24Xx]

@@yepok5120 you spelled meter wrong

[@TheRostedChickenz]

Just imagine if the janitor erased that whiteboard

[@Wumbolo]

Imagine if the janitor was Matt Damon

[@abadlydrawnsnowman1648]

verisatium loved your comment omg

[@smidgeyify]

Soooo, Matt Weighmon?

[@dhkatz_]

If you really think they didn't write that down, you have a severe lack of brain function.

[@dannydevito7000]

+Doctor Jew If you cant sense obvious humor you have a severe lack of brain function.

[@ignispurgatorius5297]

Seeing your examples in the beginning, somehow it feels like we missed a huge chance here to redefine the meter or the speed of light to be a fraction/multiple of 300.000.000 ;)

[@vesper7312]

While that would be really handy, it wouldn't be an easy change, countries would have to change road signs to match the new definition, programs that use measurements like modeling software would have to redefine their definition of a meter, anything involving the old definition of the meter would be invalidated. On the other hand, you couldn't just round the speed of light up and keep the meter the same because then the speed of light wouldn't reflect the actual speed of light.

[@ignispurgatorius5297]

@@vesper7312 I know it would require quite a bit of change for measuring equipment, though I think as far as everyday stuff goes the difference would be non-existent. Any significant change only occurs at the 4th decimal place. That is a prescision that would hardly effect normal things people use, like roadsigns. Software is also among the more easily things to fix, as that is just definitions that can be adjusted. The real pain would be measuring equiment in industries which actually require this kind of prescision. My comment was obviously a joke though. ;)

[@andrew7955]

The radius of the earth would be redefined as 4km different to what it is now... seems like basically no different. I'll keep using c=3×10^8 m/s

[@vesper7312]

@@andrew7955 It practically isn't a difference for most things, but different tasks require different levels of precision. It's perfectly fine to use c=3x10^8 as an approximation, but any result that is derived from using that value is limited to a single significant figure.

[@studio48nl]

Yeah, like they almost redefined pi to be 3 . because it would be easier ... lol

[@ingsve]

You should do a video about the discrepancies between the Kibble balance and the Avogadro project. As you might have heard the measurements never had time to completely settle before the deadline to fix the constants so that left a discrepancy between the two constants with regards to the kilogram based on what method you use to realize it.

[@prathameshkale9011]

make kilogram great again

[@Donglator]

make America before am bad good now again

[@SchiferlED]

It somehow makes me sad that they didn't redefine the meter such that light was 300,000,000 m/s

[@KaosFireMaker]

Eh. could always go with the plank system of measurement. The speed of light in that is one plank length per plank moment. The gravitational constant is one cubic plank length per (plank mass times plank moment squared).

[@Hakingdoesgames]

It'll be costly if they did, as there would need to be a lot of changes in the world.

[@Saki630]

that is not the exact speed of light sir. You have a meter set by a velocity that is incorrect which would make your meter incorrect and so your judgement.

[@vigneshr6644]

Saki630 he means that the length of the meter itself be altered to get a a number of 300000000 m/s

[@poisonouspython1410]

+SchiferlED Yeah, I agree since the meter is technically an arbitrary unit of measurement I'm not sure why they didn't set it to a nice round number in relation to light speed. I guess changing the standardized length of a meter would cause too much hubub around the world so they had to leave it alone. Bummer though since they're going to all the trouble to redefine the kilo they may as well do the meter while they're at it so it's all neat and tidy.

[@arif4896]

this is what makes me even more loves in the field of physics

[@betaneptune]

Cool video. Also KUDOS! for not using and "musical" background. Nice and easy to listen to the narration and absorb and think about the content. Thank you!

[@anaangueira1797]

I've been waiting for this video for years.

[@MrMakae90]

How much h p n² f² / 4 g v do you weight?

[@hanseidottersauger5663]

Lucas Balaminut was "more" right but wrong since p, n, f, v are not constant

[@moki2093]

Lucas Balaminut weigh*

[@mainBaisch]

actually they are constant, because it will be defined by what measurements they take in that room

[@jellybean4163]

Lucas Balaminut jgf

[@piyushsonone7]

so easy

[@SaraBearRawr0312]

Oddly, this is one of the few videos by you with math that i actually was mostly able to follow do to it using pretty basic physics based on DC electricity and standard mass units.

[@M.A.S.-SuperiorService-]

I like absorbing as much knowledge as i can from your vids bc even if i didn't get it all I'm at least a little less ignorant than i was 949 secs. Ago

[@M.A.S.-SuperiorService-]

589 seconds 9 minutes and 48 seconds

[@M.A.S.-SuperiorService-]

Make a video on why we go to 60 instead of 100

[@4ur3n]

You have misplaced a full-stop right there.

[@M.A.S.-SuperiorService-]

@@4ur3n sorry?

[@oskarjung6738]

Nice, way of thinking.

[@DigitalDiabloUK]

You lost me right after "basement"

[@GozUnlimited]

Sub-basement dude. Sub-basement. Probably best to avoid the rest of the video

[@user-fx7ce8xc1d]

@@GozUnlimited lol

[@amitanand7534]

it would be cool if we measured a kilogram by how much light bends when it passes by 1KG due to the gravitational dip in the fabric of space time.. impossible but quantifiable

[@Andrew0you0tube]

Amit Anand Wow, great idea actually

[@illidur]

it would have to be close to a perfect sphere

[@amitanand7534]

ohh yea

[@walkinmn]

That actually sounds great but i think that it would require a measurement system so sensible that i don’t know if it exists, a perfect sphere, and I'm not sure if you can do the measurements on the surface of the earth.

[@sakshisaxena7587]

+walkin mn i agree. Also, if we miss it even once then we might have to wait for a very long time to measure it again and recheck it.

[@rifdifirebolt]

it's 2018 I'm still waiting on the final result for the definition of the Kilogram. Oddly excited for it.

[@thaomy4293]

Bro ur videos are so interesting man!!!! Keep up the work i love u dude

[@MyNameIsSimple72]

Kilogram machine 🅱roke

[@BallistaBomber]

David DeGOAT Understanda🅱️le, have a nice day

[@soulstealingginger3612]

Did I hear that we're setting the new definition of the kilogram in... America? Hopefully more changes to follow...

[@cowardly_wizard]

TheSoulStealingGinger With a sphere crafted in Australia. I don't remember the video very well, that's where he was right?

[@slendy9600]

Two Good i feel like i woulda heard about it if its being done over here. you sure it wasnt Austria?

[@Farathus]

TheSoulStealingGinger it's civil research. that kind of research doesn't know boarders for decades. you probably have dozens of scientists of different nationalities work on that. also that scientist has a very strong Austrian German accent ;)

[@betaich]

The effort with the Silicon thing is a world wide effort. The raw silicon was created in Germany, than send to Russia for refinement, than send back to Germany to form a monocrystalline structure, than spheres were formed in different country, one of them Australia and measurements also take place around the world.

[@yettameter]

TheSoulStealingGinger I remember hearing from somewhere that the US govt. officially recognizes the metric system, but does not officially recognize the imperial system. In fact, all modern definitions of imperial measurements are defined by metric counterparts (the inch is defined as 2.54 cm for example). Measurements for science and engineering are always in metric. However, too much of the US's populace is too used to imperial, so changing all the signs and books in the country would be both be expensive and not very fruitful.

[@gabemoser6493]

I’d like to see how the standard kilogram diverges from the new definition

[@rumhave9632]

3 parts per billion in 100 years. Scientists are bored, however, i still watched the whole video.

[@TheoBerkhout]

Interesting to see that imperial units are a conversion of metric standards held in the USA.

[@ThePaintballgun]

This episode was way better than most of the others.

[@Nihilore]

Watch his latest Veritasium2 video where he explains the recent drop in quality. it was an experiment all along!

[@Austin-dm5bp]

Nihilore - Royalty Free Music Was going to say this too. I'm really enjoying watching Derek's videos and seeing his meta-experiment in action. I hope he shares if this much more technical video fares differently in KZbin's algorithms than the other, more simple ones he's been experimenting with lately.

[@jonathanwilhelm8891]

I would like to know more about the quantum mechanics that is beyond the scope of this video. Thank you great video.

[@santeebandit3246]

Stumbled across this channel this evening 3-2-21..and although I’ve zero scientific background, I find the subjects discussed on this channel to be amazing. I love science, although I never excelled at it. Still interests me regardless.

[@Nikioko]

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.

[@nikoladragovic9283]

8:42 *Hey V-sauce, Michael here*

[@biblical_figure]

Where are your fingers?

[@Bebolife12345]

But... how do magnets work?

[@Moxie9]

-It's that easy, yeah. -It's that easy. Me: Ok, I am out of here :D

[@Yolwoocle]

They were joking, haha

[@kagura7107]

And you're smarter than you think :^)

[@concettamiccio5814]

Great explanation! Thank you very much.

[@ChristAliveForevermore]

Everything in science can be distilled down to the relationships between weights and measures. Kinda blows the mind.

[@sandderi]

It is awesome that there is a science channel that does not try to overly popularize a subject. For people with knowledge on physics this was extremely informative. I can now easily describe how the kilogram is defined. Thank you!

[@-.._.-_...-_.._-..__..._.-.-.-]

Why is everyone so confused? Basically, the only new principle involved is that instead of power being generated by the relative motion of conductors and fluxes, it’s produced by the modial interaction of magneto-reluctance and capacitive diractance. The original machine had a base plate of prefabulated amulite, surmounted by a malleable logarithmic casing in such a way that the two spurving bearings were in a direct line with the panametric fan. The lineup consisted simply of six hydrocoptic marzelvanes, so fitted to the ambifacient lunar waneshaft that sidefumbling was effectively prevented. The main winding was of the normal lotus o-deltoid type placed in panendermic semiboloid slots of the stator, every seventh conductor being connected by a non-reversible tremie pipe to the differential girdlespring on the ‘up’ end of the grammeters. Moreover, whenever fluorescence score motion is required, it may also be employed in conjunction with a drawn reciprocation dingle arm to reduce sinusoidal depleneration.

[@cinquine1]

David S. What a waste of words. You could have just said "they use a turboencabulator", and everyone would understand.

[@megatrix500]

And people saying this video was complicated. What if Derek told us all of this with these technical words? I know quite some stuff about physics but I have no idea what a turboencabulator even is.

[@TaiViinikka]

Sadly, many otherwise-smart people still don't know how to build their own turboencabulator. Some don't even know what it is!

[@odavenport7smal]

David S. You actually had me up until the fourth sentence...

[@RyanPaton]

It was a fascinating video and I would love to know more but it certainly was not explained in a way that I could understand fully.... I mean I understood broadly what the steps were but not actually why they were the way they were. .i'm looking forward to actually researching this more in-depth and to hopefully be able to actually understand and see the process of all these steps...

[@neelimams5303]

Thanks for the valuble informations expecting more from You 😊 !!

[@ScottLahteine]

I love seeing how previous technological discoveries help to form the scaffolding for new ones. At nearly every juncture we have been justified to say "this was never possible until now."

[@brojakishormandal1676]

Please a video on definitions Of all 7 si base units

[@Jeffrey314159]

We can, as a stop gap measure, implement the Metric Mile(=1500m) on all of our interstate highways (and government roads). This metric mile would approximate 0.93 standard miles. Then this metric mile could be divided into 5000 metric feet. The metric foot will equal exactly 30cm or 11.8 inches.

[@Diode5]

Great explanation, and now I know why all the media articles had such a poor explanation of how exactly it's going to be measured.

[@Arvind-dev]

Physics Teacher : Mass is defined by physical quantity of platinum iridium alloy located at Paris *WAITING FOR THIS VIDEO* Me : No it is defined by Planck's constant. (Finally)

[@gabrielsommer2136]

You teacher is still right.

[@ashkara8652]

yeah, still gotta wait for 2018. But can't see why this won't be true!

[@pizzamannetje79]

by the time you're having those kinds of discussions with a teacher, you're probably in the wrong school

[@sheriif]

This was all in my A2 Physics exams (including the hall effect), where we were asked to derive each of the individual equations stated in the video, except for the josephson effect...

[@balapesar]

Super!! Thanks for all your wonderful efforts

[@dhiahassen9414]

Kilogram from wikipedia : The kilogram is defined in terms of three fundamental physical constants: The speed of light c, a specific atomic transition frequency ΔνCs, and the Planck constant h. The formal definition is: The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs.[3][4] This definition makes the kilogram consistent with the older definitions: the mass remains within 30 ppm of the mass of one litre of water en.wikipedia.org/wiki/Kilogram

[@Roozyj]

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

[@poop80016]

I heard an interesting NIST talk related to this. Scientists/Engineers at NIST are having to determine how much water is trapped on the surface of the platinum standard KG weights. All of the international standards are stored (or weighed) in air, so their weight includes the water stuck to their surface. They become lighter in put in a vacuum and the water is desorbed (outside of the buoyancy affect of air) . I think the mass of water was on the order of of micro grams, so a significant amount relative to the part per billion accuracy. The folks at NIST are very remarkable, and really good at chasing down any possible uncertainty.

[@braveecologic2030]

What an excellent video. Well described. Thanks.

[@Ethereal_Phoenix_]

Watched the ORB video right before this, very cool to see how this story developed.

[@Hoshimaru57]

I had a thought. We have a scientific definition of what a kilogram is, but is the scientific definition for metric length? Ah, here we go: "the prototype meter was defined as 1x10-7th of the length of the meridian through Paris through the pole to the equator." There's a more accurate definition now, but I wanted to know where it started.

[@UmVtCg]

The US has a Kg, now it is time to stop all the sillyness and to start using it.

[@kallewirsch2263]

:-) They already use it. It is just, that they have different names for it.

[@nameofthegame9664]

Allie Cat the pound is defined by a 96 year old man from Dallas. He walks out in the wood until he finds a rock that he deems the right one. Then he puts it in a bucket of 89% moonshine made of corn and drinks every drop that pours out. Then he takes a piss after 2 days and it must be a Wednesday. And then he weighs the urine and there you have it! 1 pound! The job as the guardian of 1 pound is a trait that's been passed down through generations.

[@jakadirnbek7141]

Mars Climate Orbiter agrees 🔥

[@physicsconceptsbytusharkha7638]

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.

[@jiaminzhu406]

Hey Derek. Love you video. Could you maybe also make a video about the experiment of redefining length?

[@FactHubREAL]

Why doesn't America just switch to the metric system already?

[@ibrahimmudassar6563]

I'm 100% sure that the kilogram is metric

[@bloodraven2.036]

Yeah, kgs are metric.

[@mistertheguy3073]

FactHub "the american kilogram" watch it

[@emanuelgonzalez7213]

FactHub it would cost too much money to switch everything over, plus people don't like change

[@danielhu7459]

They need special units to measure the weight of their guns and the width of their torso's after eating a Big Mac at McDonald's.

[@andersonsmith8625]

Why is the kilogram called the kilogram. It has a prefix even though its SI. Shouldn't it be renamed the gram and everything shifted down by 10^3?

[@genessab]

anderson Smith we'd have to change every book including those written hundreds of years ago, it's just too annoying to matter.

[@sytuma]

originally the unit was the gram but since it is so small the more common unit of use was the kilogram.

[@ZeroTehShadowz]

A teacher once explained it to me. Here's what I remember! Back when the first metric system was being proposed the standard for mass was named 'Grare' (I don't know what it means, I don't speak French). The French Revolution was also happening at the same time and, apparently, 'Grare' also was a reference to the nobility, so for the sake of not being beheaded they changed it to gram, and they reduced its size to help bakers and stuff make small measurements (like the amount of flour they needed to make bread) more consistent. Later they realized that most people were not measuring small enough masses for the gram to be convenient, and since they couldn't go back to the 'Grare' they just multiplied the gram by a thousand and left it at that. After the French Revolution, most of the world just accepted the kilogram as a standard and asked no questions because it was convenient, I guess. Again, I may be forgetting a lot of details since I don't speak French and I heard the story ages ago, but that was the gist of it

[@fatexx544]

anderson Smith I recommend looking up the "roundest object in the world" video, also by Veritasium. He not only explains the other method of fixing the kilogram (a sphere of silicon atom), he also explains how the kilogram got its name.

[@AnirudhGiri]

The SI unit of mass was actually the gram. But it was too small for practical use and so the Kilogram was made into the SI unit of mass. Renaming the kilogram and shifting everything down by 10^3 would just cause confusion.

[@waynetuttle6872]

I-loved-it-and-thank-you-for-being-a-teacher

[@quantaviousowandle3211]

Thanks you I needed dis for my chemistry HL hw

[@ApplepieFTW]

Now imagine everything we know is wrong and plancks constant turns out to not be a constant value

[@xiLoveYouix]

but... it is constant. The relationship between a photon's energy and its frequency is absolute. There is no way that it could change?

[@slaughterround643]

I'm pretty sure he knows guys, he's just making a hypothetical situation

[@Reydriel]

That's always a thought I had. What if these constants weren't fixed? Maybe, in some other part of the universe they change? It's all very sci-fi buts it's interesting to ponder :D

[@DanielDeVito89]

We'd have bigger problems than not having a fixed definition of the kilogram

[@Kori114]

Exactly what I was thinking. or what if they change in time and 10,000 years from now they won't understand how adult humans weighed 100 kg because it could have shifted an order of magnitude lower. The science does seem pretty clear right now that these are constant. But how will we know later if this changes? Also, it might be a stretch, but is it possible to measure these to such precision relative to each other? Does quantum uncertainty itself not affect our ability to measure these constants to such a degree of precision? I would imagine they considered that for this application though... But quantum theory has only been around 100 years, things could change... Like Feynman said, we don't really understand quantum mechanics.

[@ZenMasterChip]

As a Metrologist, I want to commend you on your selective obfuscation of the TL;DR aspect of physics which are crucial to this measurement! Needless to say, with this method we are able to balance almost every source of error to such a high degree that once we've defined Planck's constant, we will know when we are off in our measurement when it doesn't agree with with the determined value of that constant (a little inside joke). That being said, if the universal constants are changing, we're all doomed because we will have no way of knowing! Which goes to the question begged in one of your other videos; are we expanding with the universe... how would we know? Since nowadays we measure the value of everything by physical constants, if they changed, we would never know, at least not by our standards because they're all relative to one another. However, these constants affect other behaviors in physics, and since everything is related; perhaps we would be able to determine that something(s) was(were) changing; but determining what exactly and why... well, with hope, we might not be around to know.

[@gyurhanaziz7676]

We will simply measure the fine structure constant

[@ZenMasterChip]

​@@gyurhanaziz7676 Since α = (e^2) / (4πε₀ħc). We don't know exactly how each of these constant variables affects the others, only that this relationship exists. While measuring α, would allow us to detect if one of the other constants changed, since we do not know why this relationship exists, if the change of one affected the change of all of them, 'α' would still remain the same. If that's true, then perhaps nothing would affect us, and we'd never know they were changing. Since we don't know what the lower or upper limits of these are, we wouldn't see the catastrophe coming until one of the two limits surpassed the primary reason that these values are what they are. IOW, why does this relationship exist? To know so much, only to discover we know so little. This is the real problem. OTOH, I think our paradigm is changing with our perception of the ADS/CFT correspondence; and if we can fully get outside of our monkey brain to comprehend these things beyond "banana", like why these values are what they are. Then, we'll be masters of the universe. ;-) But, yes, I agree. If we measure the fine structure constant, essentially if only one constant changes we would see this, as long as we can obtain a high enough significance in our current measurements. And yes, if one of them did change, this would define an observation of the catastrophe in progress, if we are lucky enough to still be here. OTOH, if this relationship is stable, we could also have the opportunity to watch it evolve over time, if the behavior of the other variables (sic) forces them into alignment to negate any effect. This would be presuming that ADS is the built-in error correction to the quantum computer of the universe.

[@zakyouadah3978]

well, that is indeed a very precise definition.

[@domenicperito4635]

Quote: In a medium, light usually does not propagate at a speed equal to c; further, different types of light wave will travel at different speeds. The speed at which the individual crests and troughs of a plane wave (a wave filling the whole space, with only one frequency) propagate is called the phase velocity

[@Improbabilities]

Ah, yes, the old "stop chopping off 'in a vacuum'". Massless things only exist at the speed where they don't experience time. Would you like it better if I called it "untimely velocity magnitude" instead?

[@domenicperito4635]

@@Improbabilities umm i doesnt matter what you call it but its a bit hard to measure a constant velocity that isnt constant to get an accurate millimeter for my ruler

[@AnonymousAZ]

Veritasium Sauce here

[@supertaakot]

Verisaucium :^)

[@MrtinVarela]

Veritasauce

[@gautamdiwan5952]

Martín Varela vsauce

[@nomadic-loyalist]

Veritasium Sauce Veritasiu Sauce Veritasi Sauce Veritas Sauce Verita Sauce Verit Sauce Veri Sauce Ver Sauce Ve Sauce V Sauce VSauce

[@transcendentape]

It's Dirk from Veratablism.

[@florinsimion6466]

so four potatoes about a kilo...init?

[@truebluekit]

Healthy potatoes you got there.

[@eeshaan1539]

laughed so hard!

[@RoScFan]

Simion Florin can you measure those potatoes to an accuracy of a billionth of an electron?

[@florinsimion6466]

yes...as long as they are Irish potatoes init?

[@minecrap5256]

yes... as long as each potato is equal and weighs 0,25kg

[@Nikioko]

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.

[@dedamarsovac]

So, as far as I can see, the Newton is now more precisely defined than kilogram. Kilogram is (the calculated force of the weight on the Kibble) / (gravitational acceleration), both measured independently and more precisely. Both of those actually derived using two absolute references of time, one is of the wavelength of the interferometer, and the other is to time the counting of the interferometer fringes. And the kibble balance requiring much better reference of both electrical current, and electrical voltage. And the current derived from a voltage and a resistance standard. It's mathematically elegant, everything cancels out in the end, but I see why it would need decades of fiddly work. It requires so many other values to be realized with a way lower uncertainty than the final kilogram. I wonder what are the actual realized error margins of those things.