The kg is dead, long live the kg
The kg is dead long live the kg

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The kilogram, mole, kelvin, and ampere will be redefined by physical constants. For a limited time, get 3 months of Audible for just $6.95 a month: or text VERITASIUM to 500500 Will this be the last video I make about SI units? Quite possibly. There's something about being so precise and defining the systems within which science works. When we can more accurately and routinely measure a kilogram, a mole, a kelvin and an ampere, then we can make better observations, we can better detect anomalies and improve our theories. That is why this is so important to me. Special thanks to Patreon supporters: Donal Botkin, Michael Krugman, Ron Neal, Nathan Hansen, James M Nicholson, Terrance Shepherd, Stan Presolski Special thanks to NIST: Additional graphics by Ignat Berbeci Music from "Experimental1"


Kaskobi : Damn. I thought I’d be able to finally say I’ve lost weight.

Chris : “Should we make a new kilogram block made out of sodium?” Avogadro: “Na”

Yehezkiel Siahaan : Does that means a kilogram of steel is heavier than a kilogram of feathers?

same name : But steel is heavier than feethers

gradle : Sad that the pound is not dead ...

Sharan Ramesh : High school students gotta memorize a whole set of constants now GL

djhero0071 : Why the nearly 1K dislikes tho? The video pretty much put it in perspective when he said that we’ve been doing the equivalent of the Indiana Jones sand and statue thing as measurement. The new method is more consistent and allows better measurements along with not changing much. So I don’t see a problem here:

Leonardo Domonik : I knew I gained a little weight. Thanks for letting me know it's not my fault.

Jack is not in the box : If you dropped that orb while handling it, were you liable for its cost?

Sebi Michel : But steel is heavier than feathers :/

Rundik : Game of life update: Minor bug fixes

puncheex2 : Lots of comment below about legislating constants and such goo. The constants are being "fixed" only for the purposes of metrology. No one is saying that a lab chemist has to use the metrology Avogadro's number - they'll continue using the latest value determined experimentally. Somewhere down the line the metrologists will adopt the new value and change the conversion, not the unit value. An example: when the metric units were invented, the meter was set to 1/10,000,000 the distance from the north pole to the equator, and that meter was inscribed on a metal bar. Later on that distance was refined, and as a result, the value is now 1/10,000,001.965. Geographers didn't slavishly use the metrologist's length; when a new length for pole-to-equator was determined, they used that. The metrologists didn't change the meter, either. In a slow, deliberate, well-publicized manner they changed the conversion constant. And that is how it will be for all the constants they set this month. The same thing happened in the definition of the gram.

Alex Madsen : why is the Headlline and description in Danish?! We redefined kg "stays the same"

The Physicist Cuber : -2 DAYS (UTC+1 time zone)

howie Getants : Most Americans :" cool, but what's that in lbs?"

Skinny Bitch : Except for the fact that the US for some weird reason doesn’t use the metric system anyway🤦‍♂️

Black Simon : I think you can‘t compare science to art. Science is about understanding the things outside of us. Art is about expressing the things inside of us. Science, art and philosophy are all about gaining some form of enlightenment. But each discipline has it‘s own way of defining enlightenment. And in the end, they all work together and even somehow depend on each other, even though they all work in completely different ways.

loys zimmermann : One must hope that constants are... constants. And not, let say, changing with time, as the universe expand.

B4GG : I get it, for the first time in history, all our measurements of what things are, are no longer linked to anything physical in our world but a mathematical principle. We can now measure things more accurately than we can make things to that measurement.

Jesus Christ : fundamental constants in nature > physical artifacts

Police Officer : Don't mind me, I'm just learning what it is I have to vote for tomorrow.

Sandor Dugalin : They literally just voted on this at the science convention.

imat Roll : Oh I'll show you how to kill a gram.. That'll be $15. Puff..puff..puff.. 😘💨 now here's the fundamentals or what you need to know is...Wait what were we talking about again? 😎

Zypherus : It's​ still crazy to me how this is actually happening, it's so cool to think about.

Neo2266 : Avicii, Stefan K. Stefanson, Stephen Hawking, Stan Lee, And now the Kilogram ...thanks 2018 Expanding the list:(XXXtentacion, Stephen Hillinberg, George Bush...)

Horinius : FYI: your Paris map @0:47 is an old one, very certainly older than 1926.

Felenov-official : Great, I have to go recalibrate my two Fluke 5730A calibrators

Mo'kalamity : It's happening!!

Blair : Day 3 since the kilo was changed. The world is in chaos Governments have collapsed Squirrels have taken over mainstream media


Nathan Kliem : FYI: Shot location: John Lawson Park, West Vancouver, BC Canada

Jakob butzbach : the background music... checked facebook 20 times. sounds like messages were running in!

Helix Studios : Anyone else notice the TES: Redguard reference in the title?

Daniel Nepomuceno : guess what, I've just memorized conversions of mass, volume, pressure, and temperature couple of weeks ago. ha ha haha

nikko paolo de oro : 1kg steel has lower volume than 1kg feather...don't cross out the existence of Density guys

John Cabacungan : Long live the kilogram

Leonardo SA : Everything in the universe is a wave like thing, you want a fixed number for a wave? Well good luck with that, the best you are going to get is approximated values.

mmh fdsf : why they dont measure cylinder in paris and give planck number to it

Ville Lepoaho : This is like releasing a new update to a game, with some bug fixes.

Radio Laboratory : So will this affect drug prices on the street? grams, kilos etc??

CanadianMade1414 : I love the GPA your wearing!! Cha Gael

esilence : best time for US to join the changes to metric

Kitsune's Den : First Pluto stopped being a planet for a decade or so, now kilogram died. #Science #HoboMurders

zapfanzapfan : Does this mean that I lose weight? ;-)

Marc McKenzie : Huh. I always thought of constants as, well, constant!

funkyman909 : It is funny because the definition of a pound is based on a decimal number of the kilogram, so the pound will be changing in turn as well

Trajan Danubius : I have just searched something on Quora... 6:40 People still believe in the traditional paranormal... They've said, there's a library for our memories after death or that our soul contains our memories after death... or that we and our memories either go to hell or some other place based on the way and mood we died in. THIS is what really breaks the faith in humanity...

gamer3928 : what if they set plank's constant so something whack like 7

quickknowledge : Textbook publishers are salivating at the opportunity to change just a couple digits because of this new standard and calling that a new version they can charge a couple hundred bucks on.