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Thanks to my diet of tacos and skittles, my
weight constantly fluctuates, which is yet another thing I have in common with the kilogram. Hey killer grams — which is what I call my
grandma when she’s lookin’ fly — Jules here for DNews! How much does a kilogram weigh? Well…it’s a kilogram, right? But how do we know how much that is? Maybe a better answer is: 1000 grams. A gram was originally defined as the mass
of one cubic centimeter of water at the melting point of ice, and well, that’s something
we can actually measure, rather than some ephemeral idea of “a kilogram”. So, now we can say “a kilogram is 1000 cubic
centimeters of water at the melting point of ice3”. That’s almost dead on accurate, but that’s
not how much a kilogram weighs. The real answer is that a kilogram is defined
by the weight of one single object in the entire universe: Le Grand K, or “the Big
K”. On the outskirts of Paris, in the basement
of the International Bureau of Weights and Measures, is an environmentally controlled,
impenetrable safe, in which is the official definition of the kilogram4. It is called the International Prototype of
the Kilogram or IPK4,. It is a cylindrical piece of metal, a platinum
alloy to be specific, about the size of a film canister or a golf ball, and it weighs
exactly one kilogram4. And there’s no way it can’t, because the
official metric definition of a kilogram is equal to whatever Le Grand K weighs. So if you sneak into the Pavillion De Breteuil
where it’s kept, and shave one gram off the top, every single “formerly” one-kilogram
weight in the world will now officially be one gram heavier than a kilogram. I cannot stress this enough: the entire world’s
scientific understanding of what a kilogram is, is based on the exact weight of a physical
object stored in a French basement. And it’s been this way since 1889. Now, that’s not to say that the IPK isn’t
a fairly reliable source. It is made up of 90% platinum and 10% iridium10,
making it super hard, resistant to oxidation, nearly twice as dense as lead, and not very
susceptible to magnets. There are a number of exact copies all around
the world to allow for comparison and calibration. Now, it’s great that they’re going to such
lengths to make sure that nothing happens to the IPK, because if something were to happen
to it, science would change — mostly physics. Think about how often we use the kilogram,
and how much of physics is built on itself. Take, for example, the newton, which is defined
by the amount of force necessary to move a kilogram at one meter per second squared. Then, take the pascal, which is defined as
one newton per square meter, or one kilogram per meter per second squared. The kilogram is a base SI unit, so it affects
any measurement that uses mass in kilograms. And that’s a really bad precedent. Already, despite every precaution, the IPK
is changing. Since 1889 there have only been two other
verifications of its weight, in 194817 and 1989. What they found is that the Le Grand K has
lost a petit amount of weight. Roughly 50 micrograms, or 50 billionths of
a kilogram. Worse yet, scientists don’t know why that’s
happening 17. So, does this change in mass means that now
all our calculations have to be redone? Of course not, but it did force the people
who make those sorts of decisions, The General Conference on Weights and Measures, to try
and figure out a better system of defining the kilogram, rather than something you can
accidentally lose in the washing machine. In 2011, they generally agreed to redefine
the kilogram based on Planck’s constant. Planck’s constant is a number representing
the relationship between the energy of a particle and its frequency. You don’t really have to understand how
that works, except that it never changes, and it relates to energy. That’s useful, because we can then relate
energy to mass thanks to Einstein’s E=mc2 equation. This means we can define mass, and therefore,
the kilogram, using a constant figure. But the Conference on Weights and Measures
decided to postpone the decision to make that change until 2014, and in 2014 they postponed
it to 2018. Which means that if you’re having trouble
losing weight, you still have a year or two to fly to France and stick a piece of gum
on the Grand K. A heavier kilogram means a smaller you! If you’ve been a subscriber of DNews for a
while, you might’ve seen some of our recent VR videos. It’s a completely new way to tell stories,
learn and experience the world, and we just launched a brand new channel called Seeker
VR. Thanks to my diet of tacos and skittles, my
weight constantly fluctuates, which is yet another thing I have in common with the kilogram. Hey killer grams — which is what I call my
grandma when she’s lookin’ fly — Jules here for DNews! How much does a kilogram weigh?
Well…it’s a kilogram, right? But how do we know how much that is? Maybe a better answer
is: 1000 grams. A gram was originally defined as the mass of one cubic centimeter of water
at the melting point of ice, and well, that’s something we can actually measure, rather
than some ephemeral idea of “a kilogram”. So, now we can say “a kilogram is 1000 cubic
centimeters of water at the melting point of ice3”. That’s almost dead on accurate,
but that’s not how much a kilogram weighs. The real answer is that a kilogram is defined
by the weight of one single object in the entire universe: Le Grand K, or “the Big
K”. On the outskirts of Paris, in the basement
of the International Bureau of Weights and Measures, is an environmentally controlled,
impenetrable safe, in which is the official definition of the kilogram4. It is called
the International Prototype of the Kilogram or IPK4,. It is a cylindrical piece of metal,
a platinum alloy to be specific, about the size of a film canister or a golf ball, and
it weighs exactly one kilogram4. And there’s no way it can’t, because the official metric
definition of a kilogram is equal to whatever Le Grand K weighs. So if you sneak into the
Pavillion De Breteuil where it’s kept, and shave one gram off the top, every single “formerly”
one-kilogram weight in the world will now officially be one gram heavier than a kilogram.
I cannot stress this enough: the entire world’s scientific understanding of what a kilogram
is, is based on the exact weight of a physical object stored in a French basement. And it’s
been this way since 1889. Now, that’s not to say that the IPK isn’t
a fairly reliable source. It is made up of 90% platinum and 10% iridium10, making it
super hard, resistant to oxidation, nearly twice as dense as lead, and not very susceptible
to magnets. There are a number of exact copies all around the world to allow for comparison
and calibration. Now, it’s great that they’re going to such
lengths to make sure that nothing happens to the IPK, because if something were to happen
to it, science would change — mostly physics. Think about how often we use the kilogram,
and how much of physics is built on itself. Take, for example, the newton, which is defined
by the amount of force necessary to move a kilogram at one meter per second squared.
Then, take the pascal, which is defined as one newton per square meter, or one kilogram
per meter per second squared. The kilogram is a base SI unit, so it affects any measurement
that uses mass in kilograms. And that’s a really bad precedent. Already,
despite every precaution, the IPK is changing. Since 1889 there have only been two other
verifications of its weight, in 194817 and 1989. What they found is that the Le Grand
K has lost a petit amount of weight. Roughly 50 micrograms, or 50 billionths of a kilogram.
Worse yet, scientists don’t know why that’s happening 17. So, does this change in mass
means that now all our calculations have to be redone? Of course not, but it did force the people
who make those sorts of decisions, The General Conference on Weights and Measures, to try
and figure out a better system of defining the kilogram, rather than something you can
accidentally lose in the washing machine. In 2011, they generally agreed to redefine
the kilogram based on Planck’s constant. Planck’s constant is a number representing
the relationship between the energy of a particle and its frequency. You don’t really have
to understand how that works, except that it never changes, and it relates to energy.
That’s useful, because we can then relate energy to mass thanks to Einstein’s E=mc2
equation. This means we can define mass, and therefore, the kilogram, using a constant
figure. But the Conference on Weights and Measures
decided to postpone the decision to make that change until 2014, and in 2014 they postponed
it to 2018. Which means that if you’re having trouble losing weight, you still have a year
or two to fly to France and stick a piece of gum on the Grand K. A heavier kilogram
means a smaller you! If you’ve been a subscriber of DNews for a
while, you might’ve seen some of our recent VR videos. It’s a completely new way to tell
stories, learn and experience the world, and we just launched a brand new channel called
Seeker VR. You can view the videos in 360º from your phone or computer. Click now to
watch, or visit the first link in the description. And make sure you subscribe to Seeker VR. So now you know how much a kilogram really
weighs, but how long is a second, really? We have a video all about that here. So what do you prefer, kilograms or pounds?
Let us know down below in the comments and keep coming back here for more DNews every
day of the week.

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