- This video was made possible by CuriosityStream,
get access to my streaming video service Nebula.
When you sign up the CuriosityStream
with the link in the description.
(upbeat music)
- These are pollen particles suspended in water
as seen under a microscope, notice how they jiggle around.
In fact, they never stop jiggling.
Why?
The answer to this question helped prove the existence
of atoms, figure out the movement of stars
and predict the rise and fall of the stock market.
Hi there, welcome to Up and Atom.
I'm Jade, so how could something that we see
under a microscope help us understand gigantic stars
way out in the universe, or even stranger,
a totally man-made system like the stock market?
Well, the story begins in 1827,
when Robert Brown was hired by the British museum
to help form the new Botany Department.
One of his interests was how pollen
could be used to classify plants.
One day Brown wanted to look at some pollen
under the microscope.
So he put a drop of water on a microscope slide
and added pollen to it,
like always the pollen wiggled and vibrated in the water.
But for the first time Brown wondered why?
He got swept away in this question and totally forgot
about his task of classifying plants.
Let's see if we can figure it out.
When we watched the pollen for a while,
the small vibrating movements seem to add up
causing it to drift and zigzag through the water.
What is a typical phenomenon that may cause something
in water to move around?
Well, one I'm sure you're familiar with is a current.
Brown thought maybe the surrounding air
was causing a current which was moving the pollen.
A pretty good guess, but there's a problem.
A current would push all the pollen in one direction
and the pollen is moving randomly.
So that's not it.
Brown's next thought was maybe
it has something to do with water evaporation.
To test this, he needed a way to see what would happen
if evaporation stopped.
So he suspended a drop of water with pollen particles in it,
inside oil, keeping the water trapped,
but the jiggling was still there.
So water evaporation without.
Brown knew the plant the pollen came from was alive.
So he wondered if perhaps the pollen might also be alive
and actively swimming around like sperm.
This might sound silly to us now, but what would you think
if you put something under the microscope
and it never stops jiggling and moving around?
I would definitely think something spooky was going on.
But when we repeat this experiment
with things we sure are definitely not alive.
The jiggling is still there.
It's not just limited to pollen.
So that wasn't it either.
The defining feature that all of the jiggling specimens have
in common is that the motion is totally random.
Eventually Brown moved on
to other experiments without solving the problem.
He was probably having a tough time convincing
his colleagues in the Botany Department
that looking at a piece of pollen
under a microscope was really the best use of his time.
But we are not going to give up.
Now, before we go on
let's get a little context for some
of the scientific views at the time.
Atoms had not yet been discovered.
And the popular understanding of liquids and gases was
that they were densely packed with particles and surrounded
by an invisible substance called caloric fluid,
scientists thought that when they warmed up a liquid
or compressed a gas that caloric fluid was flowing
into the system.
Then when they let it cool the caloric fluid would flow out.
But some scientists were working on a different idea
which said that all those changes in pressure
and temperature could be accounted for by one simple thing,
a small amount of particles constantly moving
and bouncing around.
Now, from the perspective at the time
this was a pretty strange idea.
How could a relatively small number of particles fill
up a whole space, the way a gas expands
to fill up a container and how do they keep moving
even after being left alone for a long time?
Shouldn't they just quickly settle down
and lose all their energy
the way you see a cloud of dust settle,
but there was an even bigger problem.
The theory said that the particles were so small
that even the best microscopes at the time
wouldn't be able to see them.
How was one supposed to experimentally prove a theory
that couldn't be seen?
Well, it was Einstein who came up with a solution
to the problem and in doing so
solved Brown's pollen mystery as well.
He figured that even
if you couldn't see the tiny particles themselves
you should be able to describe how they interact
with something larger that you can see, like wind.
We can't see it, but we know it's there
because we can see its effect on other things.
This is my mom and she is going
to help demonstrate this idea.
Here we have an amp connected to an electric bass guitar.
Here I'm putting in some polystyrene balls
which represent water molecules and a giant red bull
which represents the pollen particle.
When we put the amp on a low setting and play the guitar,
it'll vibrate causing the balls to bounce and jiggle around.
Look familiar?
Now let's turn it up.
This represents an increase in heat.
Hit it mom,
the more energy put into the system
the more violently the balls jiggle around.
So if these tiny particles or atoms did exist,
it would not only explain how increases
in temperature effect pressure and density
in liquids and gases.
It would also explain
why Brown's pollen never stopped jiggling around.
Thanks mom.
This was Einstein's idea.
A nice theory, but how do we know it's true?
Well, let's try it with some water
and something else that we can see.
Ink.
Here I have a glass of cold water and a glass of hot water.
If water really is made up of tiny atoms
which vibrate faster, if more heat is applied
how do you expect that the ink molecules
will behave in each glass?
Take a moment here to pause the video
and see if you can guess how a drop
of ink will behave in each glass.
Ready?
(gentle music)
How did you go?
There's a massive difference.
The ink molecules disperse much faster
and much more violently in the hot water.
This is exactly what we should expect
based on Einstein's theory.
As the hot water molecules are vibrating faster
and more energetically than the cold water molecules.
This theory was experimentally proven
by a French physicist named Jean Perrin who
won a Nobel prize for his work.
Not only did this debunk caloric theory
but is considered the major turning point for atomic theory
where even the scientists who were most skeptical
of this constantly moving tiny particle idea were converted.
This laid the basis for everything we now know about atoms.
Lots of modern technology
from the device you're watching this on to nuclear power
were made possible by these fundamental insights
into the microscopic world.
So big thanks to Robert Brown
for getting obsessed with jiggling pollen
when he should have been classifying plants.
Because of his pioneering work
this phenomenon of tiny atoms pushing
around a larger particle is called Brownian motion.
Brownian motion is most famous for its role
in proving atomic theory, but it's turned out to be useful
in many other fields, including astrophysics and finance.
Now, this might seem weird
because how could the random motion of pollen being hit
by millions of water molecules possibly apply
to giant stars and man-made financial systems?
Well, what is Brownian motion really describing?
Behind the pollen and the atoms,
it's one big thing being affected
by lots and lots of smaller random forces.
So let's imagine that our grain of pollen
is in fact a giant star.
What in the universe might surround it
that could make it jostle around like the water molecules?
As it turns out, the combination of lots of little pulls
from the gravitational field of smaller stars
can jostle around a type of large star
called a massive binary.
A star might not be literally hit
by thousands of smaller objects from all sides
but there are still many smaller
random forces being applied to a larger object.
The force is just gravitational rather
than being physically hit.
Just like with the water molecules,
the smaller stars are not coordinated with each other.
So the forces they exert on the massive binary add up
to random motion.
What about for financial markets?
This is probably even weirder because pollen jostle
and (indistinct), although massively different in scale,
a naturally physical phenomenon.
The stock market is a purely human enterprise.
What forces could possibly simply act
on the price of a stock?
Well, imagine there are 10 apples available to buy,
the price of those apples will be much higher
if 10,000 people want to buy an apple
than if just one person wants to buy an apple,
that seems pretty straightforward
but what determines how many apples are available
or how many apples people want?
The number of available apples could rise
if the weather is good for apple growing
or fall if there is a pest invasion.
Those things aren't easy to predict
and can be considered random factors
for all intents and purposes.
That was a very simple example,
but in real financial markets supply
and demand depends on lots of different things
including a plethora of human emotions, greed and fear,
hope and defeat, elation and despair, news and sentiment.
The state of the world and many more.
Forces on the stock market are more abstract
than water molecules and gravitational pull.
But the mathematics of Brownian motion can still be applied.
It's still a lot of smaller random forces acting
on a larger object.
Brownian motion isn't about pollen, stars,
or the stock market, the power of science lies
in its ability to pull out all of the abstract elements
that different phenomena have in common
and to using the solution to one problem to solve many.
If the same mathematics can be used
to solve many different phenomena,
this leads to a very interesting question,
is the universe mathematical
or is math a language we've invented to describe it?
Is math invented or discovered.
I've made a video discussing these very questions
over on Nebula, which you can watch for free with this link.
So Nebula is an educational streaming platform made
by your favorite educational creators like Adam Neely
(indistinct) real engineering went over productions,
Brian Craft and many more.
We created Nebula so we could have more creative freedom
to bring our creations to life.
For example, I felt that this question
of is math invented or discovered needed more than a month
of work to do it justice, which is about what I spend
on my regular YouTube videos.
Because of Nebula, I was able to spend four months
researching the topic
and get help in the production process
to really make it a special experience for you guys.
If you like the video,
consider subscribing to Nebula to get access to
and support the creation of more videos, just like it.
It's only $3 a month, but our friends at CuriosityStream
are offering a special deal where if you sign up with them
you get Nebula for free.
CuriosityStream is a documentary streaming service
with names like David Attenborough and Stephen Hawking.
So by signing up with them,
you're getting two educational streaming services
for the price of one, that is literally hundreds of hours
of awesome things to learn, but less than $20 a year.
If that sounds like something you're interested in,
go to curiositystream.com/upandatom.
You can find that link and the link to that
is math discovered or invented video in the description.
Thank you for watching and I'll see you in the next episode.
Bye.
(upbeat music)