This episode is sponsored by Endel,   an app that creates personalized  soundscapes to help you focus,   relax and sleep.

The first 100 people to click our  description link will get a one week free trial. It’s probably hard to ignore the very obvious  green algae taking up most of your screen.   But for the moment, I want you to try.

Look away  from the closterium and instead, shift your focus   to the area that surrounds it. At first, it may  not seem that interesting. It’s just a sea of   dark blue, interrupted only by tiny little dots.

But unlike the completely static closterium, those   tiny little dots are wiggling around in  frantic, uncoordinated directions like they’re   dancing to a million different soundtracks  played at once. There are organisms in the   world of the microcosmos that move in concerted,  directed ways, but this is definitely not that.  Now let’s focus on the closterium. Look towards  the tip of the algae, where there are round barium   crystals wiggling around in the same random  way that those particles we saw before were.  We’re going to see that type of motion over  and over again today because it’s all over the   microcosmos, found in and around many different  types of organisms.

And this kind of random motion   may seem almost too trivial to discuss, leading  at best to an end where I mull over the way that   randomness seems to pop up everywhere like some  kind of unifying force that shapes our lives   through millions of tiny coincidences. Except, well, there’s no point waiting   until the end to say all that because the  reason we want to talk about this weird,   wiggling motion is that this randomness really  does tie us together, not metaphorically, but   very, very literally and physically. This motion  that you see is a proof of something fundamental   not just to life, but to existence  itself.

This movement is proof of atoms.  It’s easy to take the existence of atoms for  granted now, in the same way that it’s easy to   take the existence of microbes for granted. Once  you know about them and how they shape the world,   and you've been told about them since you were a child, it’s impossible to see the  world as existing without them.  But our knowledge of both is relatively recent,   even if it’s built on work that spans  millennia. And just as the microscope has been   essential to our understanding of microbes, it has  played an important role in understanding atoms.  Long before the existence of the  microscope though, there was an idea.   In the fifth century BCE, a Greek philosopher  named Democritus proposed that if you kept   breaking matter down further and further, you  would eventually reach something that could no   longer be broken down.

That indivisible thing was  what he called atomos, which meant “uncuttable”. Democritus’ theory was in opposition  to the ideas of Aristotle and Plato,   who believed that the world was composed of  four basic elements: earth, wind, air, and fire.  So what does Democritus have  to do with the tiny little   wobbles of the pigments inside this stentor? For that, we have to flash forward to 1827.   This was an exciting time for anyone interested in  diving deep into what matter was made of.

The end   of the 18th century had seen important advances  in our understanding of matter. And in 1803,   the scientist John Dalton drew upon these  ideas to propose that each chemical element   could be described by a particular atom. The atom became a useful tool in developing new   theories about how our world is built, and 19th  century physicists used it to describe a theory of   gasses that assumed they were composed of many,  many tiny particles constantly moving around.  But these theories weren’t proof.

If anything,  they raised more questions about how to think   about atoms. Should we think of atoms as  just some kind of mathematical metaphor,   or were they something real? And how could we  find proof of something as unseeable as an atom?  The answer, it would turn out, would come  thanks to a botanist named Robert Brown.  Brown wasn’t setting out to solve the  problem of atoms.

It was the summer of 1827,   and he was trying to clear up some questions  he had about the tiny particles that burst   out of pollen grains like this one. So he did what we’re doing right now:   he brought out his microscope, and looked at  some tiny things under it. While we didn’t have   those pollen particles on hand, we imagine that  what he saw was similar to these oil droplets,   which came from the body of a dying copepod.

He said simply, “While examining the form of   these particles immersed in water, I observed  many of them very evidently in motion,”.   Curious about this motion, Brown proceeded to do  a number of different experiments. He looked at   pollen from other plants and saw the same motion.  He looked at pollen from dead plants and saw the   same motion. He even moved on to inorganic  materials like rocks and saw the same motion.  In water, everything wiggled, even if it wasn’t  living.

And that meant the motion wasn’t something   biological, it was rooted in something else. These random movements are what we now call   Brownian motion. And in the decades that followed  his observation, physicists began to study it   in earnest so they could understand  the forces that shaped the movement.  For example, one scientist noted that smaller  particles exhibited faster motion compared to   larger ones, which you can see at play here  in the crystals lying within this amoeba,   with the larger crystals moving more  slowly compared to the smaller ones5.  But Brownian motion’s biggest impact would  come in 1905 when a scientist theorized   that the movement of the particles Brown  had watched was the result of other smaller   particles colliding into them.

That scientist, you probably know the name of, it was Albert Einstein. And those smaller particles were water molecules, composed of   atoms that are packed with energy. And because of  that energy, the water molecules are constantly   moving and colliding.

Sometimes they collide with  each other. And sometimes they collide into other   larger particles, which move erratically in  response. That is Brownian motion, a movement   shaped by atoms and their kinetic energy.

Einstein’s theories were built on equations,   but they provided a framework that would allow  experimentalists to use Brownian motion as a   way to see atoms and their energy at work. And  ultimately, it was the French scientist Jean   Perrin who put these theories to the test, using  a new microscope called the ultramicroscope to   not only study Brownian motion and confirm the  equations that drove Einstein’s theory, but also   to estimate the size of water molecules. All of that discovery was made possible because a   botanist wanted to study some pollen.  Robert Brown was operating in a realm   that is familiar to us here on Journey to the  Microcosmos.

He was exploring an invisible world.  But what he studied and what he described helped  us find an even more invisible world, one that was   still invisible under his microscope, except  that it was responsible for everything he was   seeing, not just the motions of the pollen grains,  but the pollen grains themselves and anything else   that was under his microscope, outside his  microscope, and even the microscope itself.  What he found in those wiggles—what you’re seeing  now in the same motion more than a century later,   is an invisible world that  built an entire universe.  Thank you for coming on this journey with us as  we explore the unseen world that surrounds us.  And thank you again to Endel  for sponsoring this episode.  Endel is an app that takes  everything we know about sound,   combines it with technology, and creates  personalized soundscapes to help you focus,   relax, and sleep. Their app was named the Apple  Watch App of the Year in 2020 and they have a   brand new soundscape called Wind Down that  they made in collaboration with James Blake.   The goal of Wind Down is to help you  transition from an active day to a   calmer state, so it’s great just before bed too. Sound has a direct impact on your physical and   mental wellbeing, and by adapting in  real-time to things like your location,   weather, and heart rate, Endel creates simple,  pleasant sounds that can help to calm your mind.  If you’re interested in trying out Endel, just  be one of the first 100 people to download it   using the link in the description and you  will get a free week of audio experiences!  Thank you to all the people whose  names are on screen right now.   They are our Patreon patrons.

We love what we  do at Journey to the Microcosmos, this team   is just delighted to be able to do it, and I am  so glad that other people love it too because   without them we would definitely not be able to  do it, so thank you so much to all of our patrons.   And if you are interested in becoming one, you  can check it out at Patreon.com/JourneytoMicro.  If you want to see more from our  master of microscopes, James Weiss,   you can check out Jam & Germs on Instagram,  and if you want to see more from us,   there is always a subscribe  button somewhere nearby.