Veritasium - 2017-07-12
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 http://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: http://ve42.co/patreon Interferometer video by TSG Physics: https://www.youtube.com/watch?v=j-u3IEgcTiQ Music from http://epidemicsound.com "ExperiMental1" by Gunnar Johnsén Studio filming by Raquel Nuno
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".
@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
Like what my physics teacher used to say the physics equations are simple math...
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?" 🤔
@Mukund Ranjan Tiwari Yes I think they are. The job is to find the simple truth of apparently complex things, without being excessively complicated or oversimplifying it ;)
Another thing.. I thought the fact that you've locally mapped g in the room was FASCINATING.
+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
Hi Mr. Potato
How crazy is that?!!
That's an insane amount of precision. Just mind-blowing.
my head after 35 seconds:
INTERNAL SERVER ERROR 500
NO BRAIN CONNECTION DETECTED
I would have expected 413 (Payload Too Large) or 507 (Insufficient Storage).
As long as your brain doesn't return code 418 (I'm a Teapot), I guess it's not too bad.
Me: huh
Most people:
INTERNAL SERVER ERROR 69
INVALID FORMAT
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.
How do you measure g without knowing what a kg is? this seems circular.
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.
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.
@Idjles Erle 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.
I agree from an external perspective too
brain.exe has stopped working
sudo apt-install physics-degree
@Connor D What do you know? It could be wine.
@BluntforceJ it is basic. It is the world that moves around that make it hard. It is the engineering that is hard.
Didn't get the notification but noticed a severe slowdown.
@lemble What kind of crazy school do you got to?
The official day has come....
Today kilogram definition is changed
@Jam Bos The planck's constant is derived from the sun's spectrum and planck's equation. The laws of physics tells us what the energy of the particles would be, but they had to express it in terms of the old kilogram, because that's what we had. But now that we have the new kilogram defined, we can just count particles. That's what they did with the silicon sphere. The joule will depend now on the new kilogram, which is defined by the mass of a known quantity of particles which will be equivalent to the energy of a certain photon, and so on, all that we can know through the equations of physics, and the magnitudes that we measured from caesium 133 and the speed of light. It's pretty confusing, I must say.
@ThalesPo you forget that the speed of light was fixed in the 70's to an exact value, just like they are doing now with Plank's constant. So the meter is a unit that is defined by this fixing of speed of the light.
Furthermore, the sun, as a physical body having a spectrum of radiation, is not a black body, as black bodies are ideal objects which don't exist, thus cannot be used to calculate Plank's constant, which is defined by the spectrum of radiation of black bodies.
@Jam Bos Yeah, sure. But what did you want? All the equations in physics are approximations. No one knows the true laws of physics. That's what they're working on right now with the string theories and similars. And even though, it's doubted that it's possible with those means, because it may be way more complex that they can imagine. But we are doing the best that we can.
But I don't believe that you can deny that the kilogram being defined by a number of atoms of a certain isotope is way steadier than a kilogram defined by piece of metal.
Edit: I missed the conjunction on word 54. It should be "...complex than..."*. And I forgot an article in the last line. It should be "...by a piece of metal."*.
Yes but that still depends on the what gravitational constant? It would way differently on mars. As since we don't understand gravity well. And using fixed set 'minimum' and ' maximum' makes it either convenient to use this reasoning. Don't know very much too well about this topic as you guys, was an interesting read though. But feels like @James Bos is still trying to protect sort of the possible truth, although we don't know the true laws indeed. But always good in the sake of the unknown factors to not draw such conclusions. but who the hell am i. i'm sure they know what they are doing..
Watt?
Volt you don't understand
Cause.
That joke was lame, scAmpere off.
I Resist the urge to laugh.
Watching this on May 20, 2019.
SI units have been officially redefined today, kg is defined by Planck’s constant.
You know what I hate Plank's Constant
@Bhupendra Singh and the Planck's constant hates you.
@Melquisedec Alvarado : 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.
/r/MapsWithoutNewZealand at 0:35
Or at least, without the North Island
New Zealand doesn't really exist, does it?
@abortionsrock nah think it's a place in Australia
Auckland exists
The new Kg will be defined as 1/247th of your mother's weight
Golden.
@Amin Ben badass kid
LMAO WTF
That would be one heavy kilogram...
nice
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
589 seconds 9 minutes and 48 seconds
Make a video on why we go to 60 instead of 100
Its true now!
Commented on 16 Nov 2018
yayyyyy
Wooo hoooo
Make Kilogram Great Again
Who's here on the big day?
One Balance to rule them all, one balance to define them.
One balance to standardise them all, and into light forever bind them.
Oh no, the sticker is gonna screw the measurement
lol
Ash nazg durbatulûk, ash nazg gimbatul,
ash nazg thrakatulûk, agh burzum-ishi krimpatul.
Serpentine The black speech has never been spoken on Youtube before.
Until uncle "SAM" carries Frodo into Mountain or mordor ....
MuRiKAaaaaaaaaaaaa
https://youtu.be/X-WgGjJ_On8 here America vs japan
TLDR 8:09
More like TL;DW
Thank you
No.
Watch the whole d---*- thing!!
and eat all your vegetables [unless you shouldn't]!!!
I'm joking, I'm experience the humor/comedy version of sarchoticism right now😥
It's like being werewolf, but instead, you turn into an internet troll😭
Look up the definition of a kilogram, hint: he's wrong
Where was he wrong? https://en.wikipedia.org/wiki/Kibble_balance
Why defining kilogram instead of gram?
And it's also about a time to replace tonnes with megagrams.
-It's that easy, yeah.
-It's that easy.
Me: Ok, I am out of here :D
When they locally mapped 'g' in the room's surface plane, it reminded me of Rick making an 'absolute level' surface from Morty's Mind Blowers.
Ah, I see you are a person of culture.
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.
Fizizy Watt do you mean? 🤓
Yeah, this video seems to assume a lot of background knowledge. Either that or I'm an idiot.
James Watt is who it is named by
All my brain gets from this is, "put the mass in and get the H out!"
I understood that and nothing else...
7:49 - She's Lebanese <3
Please a video on definitions
Of all 7 si base units
I would recommend watching practical engineer's video on this and how he made a homemade watt balance
4 years of my physics degree later and I'm still like "ah yes I know some of those words"
sureee, i'm in my first year and I understood everything he said
How do you determine f accurately? Or else, how can you send out radiowaves with wavelengths known precisely enough?
dude get your money back. thats a crap university
As someone who commited the fatal error of assuming that 'as long as you pass the exams, you learn' I bitterly have to concur. Also, if you don't actively work on these topics as an experimental physicist you'll forget them very very fast :(.
Tem Kuskov lol do you think you will remember all the physics equations you learned in university, even if you attend the best of the best , you will forget most equation and maybe only remember the basics
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?
"Hahahahaha just that easy, just that simple" I hope I can say something like that
1:24 except that we know now that the speed of light can change.
I literally thought it said “redefining the keg.” I don’t know what that says about my alcohol consumption lmao
''Derek changing the world, one kilogram at a time''
Isaac Haller you must be fun at parties..
+illuminatist boss The pound mass is defined as exactly 0.45359237 kilogram, so the pound will also change.
Actually changing the kilogram, one world at a time.
Some people prefer losing kilograms. Some like to define them.
Game of Life 1.15.2:
- Minor bug fixes.
At least they will now know Planck's constant to infinite decimal places 🤣
0:21 I'm at least 50% french and I'm so proud. Good luck with the replica!
Who comes from the "Long live the kg video? :D😂
drugs dealers are going back to school because of this
One meter of skunk please.
“Could I get 28.35g of weed?”
Avacado H Yeah becoz then dont want their weights to be inaccurate in one-billionth of a kilo, as a single nanogram of kilo can contain enough drug molecules to give you extra kick that will land you in kissing the Scientist's cunt.
hahaha they better go back to school or business is over
Now nearly an year later, I'm(or the chemist inside me is) really eager to know the answer.
When he showed the simplified version of the formula he mentioned that some of the values were known constants, so why didn't he sub those in to further simplify the final equation
Just when my massive headache was starting to go away, I watched this video... The math is inhumane.
Everything in science can be distilled down to the relationships between weights and measures. Kinda blows the mind.
I will have to come back and watch this video again when I am not high
Don't worry. It's a reupload anyways.
It doesn't help, but at least you are not able to perceive that fact...
thought i was the only one haha
RV proof that weed is bad for you. Lol
this reminds me of lambda from Half-Life the game. xD 0:04
That first elevator is something straight from HL1
8:35 is mocking me.
R.I.P. the 1-kg mass in France. You'll be remembered.
There is no authoritative imperial unit standard as a physical object for measures, hasn't been for a long while. Since the British units were destroyed in an accident and were found to be of low quality even well before that, the units were instead referenced on metric units by the Mendenhall Order of 1893 in the States, and the definitions were adjusted for higher precision again in terms of metric in 1959 internationally. So to claim that metric units were not used to put man on the moon is fallacious.
"With respect to units, the LGC was eclectic. Inside the computer we used metric units, at least in the case of powered-flight navigation and guidance. At the operational level NASA, and especially the astronauts, preferred English units. This meant that before being displayed, altitude and altitude-rate (for example) were calculated from the metric state vector maintained by navigation, and then were converted to feet and ft/sec. It would have felt weird to speak of spacecraft altitude in meters, and both thrust and mass were commonly expressed in pounds. Because part of the point of this paper is to show how things were called in this era of spaceflight, I shall usually express quantities in the units that it would have felt natural to use at the time."
https://www.doneyles.com/LM/Tales.html
Joes WebPresence we already know that light speed can be slower than the absolute speed limit, its nothing new. but the "speed of causality" is still constant, and we know that massless particles are the only ones that can move at such speed. so its still possible the use as a measurement since we know its a absolute value and constant
As a high-school physics/chemistry junkie, I found this VERY COOL!
Fascinating but just this definition of the meter is missing a crucial part, what is a second? Turns out that is defined as "the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom".
I imagine someone explaining our SI standard to an alien and they could actually follow that explanation and know precisely what all our SI standards are, and thats just amazing!
Or they'd look at us like we have one head and hand us a ducking clock 😂
that is amazing, thank you for making this video. I am always amazed at the extreme attention to detail it takes to make very precise measurements, especially when they are defining constants that other scientists and engineers will use in their calculations.
How exactly do we "Know" that the speed of light is indeed constant throughout the universe again?
Kai Widman - 2017-07-12
The kilogram is being redefined in the United States? How ironic.
Third party - 2019-08-10
I know this is an old comment and video, but if you have researched, or watched his 2014 video about the sphere...
you would know that the imperial measurement system doesn't have physical weight tied to it's system of measurement because it is calculated to be the equivalent of: 0.453592 kg
...which is why we need the kg precisely measured.
Grasshopper K - 2019-10-01
@Frank Joosten it doesn't matter to them that it's a better system, in the late 1700's, as far as they were concerned it was what the British were using, which they had just decided why wanted nothing to do with.
Mfon Inyang - 2019-10-08
im dying
Motaz Fawzi - 2019-12-11
Sht
GH1618 - 2020-03-02
Kai Widman — Not really. The United States was one of the original members of the Convention du Mètre of 1875. We have the best technology, so it is fitting.