The great thing about our universe is that it’s full of stuff.

We’ve got atoms, galaxies, and rays of light. I mean, it could just be empty, and instead we have this incredible universe.

But how did it get this way? Arranged into particles and solar  systems and giant spirals of stars? At all different scales, the key to the structure of the universe… is the way it vibes.

From the insides of atoms to the arms of galaxies, vibrations give rise to some of the most mind-blowing structures in our universe. [intro] The universe vibes because lots of things have what’s called a natural frequency, or sometimes more than one. You can think of a natural frequency as the frequency an object “likes” to vibrate at. For instance, if you blow  over the top of a bottle, or pluck a guitar string, it’ll vibrate and make a sound  at one specific frequency.

That’s its natural frequency, and it’s determined by the  object’s physical properties. When objects get a regular push or pull near their natural frequency, they’ll start vibrating. That’s called resonance.

But a vibration doesn’t have to be a sound; it can be any back-and-forth motion, or oscillation. Like, a swing always takes the same amount of time to go back and forth. If you’re pushing a child on a swing and the swing comes back  to you 30 times a minute — that’s its natural frequency.

And as you give it a push each  time it reaches the top of its arc, the swing goes higher and  higher, thanks to resonance. In this video we’re talking  about vibrations and resonance all over the universe, and the incredible ways these  simple phenomena play out. Back before there were galaxies  and stars and solar systems, the universe started out as a hot soup made of fundamental particles.

And things were pretty smooth at first. Nothing was clumped up or lopsided… And we know this because today, nearly 14 billion years later, we can still see a snapshot  of that early universe. It’s called the Cosmic Microwave  Background, or the CMB.

It’s this faint glow that radiates  from every point in the sky. This glow originated during the Big Bang. It stretched out as space expanded, and today it falls to Earth  as microwave radiation.

One of the first things  astronomers noticed about the CMB was that there didn’t seem  to be any features to it. All they could see was a faint, uniform glow. But looking at it with more sensitive telescopes revealed that it’s not completely smooth.

Some sections are ever so slightly  warmer or cooler than others. And this pattern of fluctuations is an imprint of some of the  universe’s first-ever vibrations. The first sign of structure that emerged when the universe was just a hot, primordial soup.

Back then, there were particles  of light, called photons, and a mishmash of subatomic particles, including protons, neutrons, and electrons. Within a few seconds, some of those protons and neutrons joined together to form atomic nuclei. But it was too hot for the  electrons to settle down into atoms, so they stayed loose.

As they whizzed around, they scattered photons like pinballs, making it impossible for  light to really get anywhere. Meanwhile, those same electrons were tugging on the protons  and nuclei around them. That created a link between  the photons and the particles, with the electrons as the middlemen.

The whole mix flowed together like a single fluid. But within that fluid, there  were some competing forces: As photons pinged against other particles, they created an outward push  known as radiation pressure. The other particles had mass, so they created a gravitational  force, pulling inward.

This set up a little tug of war. Gravity pulled matter together, increasing the density in some regions. But as density increased, collisions between photons and matter also increased, and radiation pressure from those collisions pushed matter back outward.

As this fluid made of matter and photons repeatedly squeezed and stretched, it created a spring-like oscillation. This vibration, this squeeze and stretch, kept going for a few hundred thousand years. At that point, things cooled enough for the free electrons to get captured by nuclei.

Once they were tied up in atoms, those electrons stopped scattering photons, and the photons broke free. Suddenly, matter was no longer bound to light. And with that, the oscillations ended.

But the ripples from that  tug-of-war got frozen in place. Regions that were being squeezed when the oscillations ended were slightly hotter. The regions that were being  stretched were slightly cooler.

That created the pattern of  warmer and cooler sections we see imprinted on the CMB today. Over time, matter in those denser areas came together under the force of gravity, and collapsed into stars and galaxies. Stuff, rather than soup.

Today, the distribution of galaxies  in the universe aligns with the warmer sections of the CMB, revealing that those early, microscopic vibrations in our baby universe became the seeds of galaxies. Today, those galaxies themselves are some of the most incredible examples of structure in the universe — especially the spiral ones. Astronomers don’t completely understand how spiral galaxies form, but one leading idea is that spiral arms are a kind of oscillation — a vibe, if you like — known as a density wave.

Density waves themselves are pretty ordinary. If you’ve ever hit the end of a slinky and watched a wave run through it, you’ve seen a density wave. It’s like a little pinch that  travels through some medium… even though no physical thing is  moving from one end to the next.

Astronomers think that spiral arms are  basically a galactic version of this: They’re just parts of the galaxy that have gotten scrunched up enough to pop out a bunch of new stars, and then will relax again as the wave passes through. Scientists aren’t sure what exactly triggers these waves in the first place, but they think part of the reason the spiral structure holds its shape is because of how various oscillations in the galaxy sync up. Because the density waves aren’t the only oscillations happening.

Even though stars look like  they’re fixed in place, they’re actually constantly orbiting the center of their galaxy. And as stars go around and around, they do a little dance. They move in and out as other stuff orbiting the galaxy pulls on them.

And that little dance has its own frequency. In spiral galaxies, that frequency often matches the amount of time between density waves… and that’s not a coincidence! What happens is, every time a density wave passes, it tugs on the star.

When that tug aligns with the star’s in-and-out motion of the star, it reinforces it. Think of the swingset example, where the swing goes higher and higher as you give it a regular push. That’s exactly what astronomers think is happening in spiral galaxies.

In a galaxy, that periodic tug caused by the density wave eventually nudges the star into an in-and-out pattern that’s a multiple of the wave’s period. Or the amount of time it takes the wave to go around the galaxy once. Like the swingset scenario, this is an example of resonance.

And resonances with the density waves help sync up the galaxy so that it keeps its overall shape, even as individual stars  go in and out of the arms. So a spiral galaxy both  forms, and stays, a spiral, even though everything in it is moving! Now, if you zoom way in on  one of these spiral galaxies and look at a star system, chances are, you’ll find even  more objects moving in sync.

For instance, here in our solar system, Pluto makes three orbits for  every two orbits of Neptune. Similarly, every time Jupiter’s  moon Ganymede makes one orbit, its fellow moon Europa makes exactly two, while Io makes four. And whole groups of asteroids have orbital periods that are perfectly synced with Jupiter’s.

And we’re not special! Around the galaxy, some planetary systems are even more synced up. A system of exoplanets  known as the Trappist system has at least seven planets whose orbital periods are nearly whole number ratios of each other.

If that doesn’t seem amazing, remember: These systems all started out  as a hot mess of swirling matter that somehow turned into planets and moon that politely do-si-do around their star. And once again, these patterns form because  of the way things vibe. As objects move around their star, they tug on each other at different points.

And whenever an object experiences a tug, its orbit changes a little. It might gradually shrink or widen or change shape. And this changes the orbit’s frequency.

Now, orbital mechanics gets messy fast, so we won’t get into all the details here, but to make a long story short what happens is this: Over time, two nearby bodies will  often pull each other into orbits whose frequencies reinforce  each other. In other words, they’re in resonance. They give each other a tug  at just the right moment to reinforce each other’s motion, just like if you push a swing right when it reaches the top of its arc.

When this happens, orbits that had been stretching or shrinking suddenly lock into place. This is called resonance capture. Once two satellites are in this configuration, it can be hard for them to get out.

If one object starts to move  out of the resonant orbit, the resonant object will naturally hold it back or pull it forward a little until it falls back into resonance. And this is one big reason why planetary systems settle into such organized places. But these cosmic vibes aren’t just  structuring stuff out in space.

Even at a subatomic level, resonant vibrations underpin  the world as we know it. Just like a swingset or a planetary system, atoms and molecules have natural frequencies based on their structure. Inside them, electrons whiz around  the nucleus in specific orbitals.

You can imagine an orbital as being kind of like a story in a building. You have a ground level and then you have a bunch  of other levels above that. Electrons occupy different energy levels depending on how much energy they have.

And electrons can move between orbitals if they gain or lose exactly  the right amount of energy… like when they come in contact with light. Light is an electromagnetic wave that jiggles charged particles back and forth. And every different color of light has a different frequency, which also corresponds to a different amount of energy.

Certain colors have just  the right amount of energy to bump an electron to a higher orbital. When this happens, it means the frequency of the light is one of the natural frequencies of the atom. Meanwhile, anytime an electron drops down from a higher orbital to a lower one, it releases light.

Once again, that light has a specific frequency that corresponds to the difference in energy between two orbitals. All the colors we see in the universe come from light being absorbed or emitted by atoms and molecules. For example, leaves are green because they absorb everything except green light.

If it weren’t for resonant vibrations, the interactions between light and matter that give the world its  color just wouldn’t happen. Our whole universe would be colorless. If we drill down to the tiniest  building blocks of our universe, we’ll find particles.

And even those owe their existence to vibrations. Because particles, despite being the tiniest things out there, are actually not the most fundamental thing. As best as theoretical physicists can understand, particles themselves emerge from what are called fields.

You can think of a field as a kind of fluid d that is spread all throughout the universe. Fields have a specific value at every point in space. A magnetic field is one familiar example of this.

You can’t feel a magnetic field yourself, but if you look at how iron filings orient themselves around a magnet, you can see that there is  something permeating space that is “telling” those filings  how to orient themselves. That’s the value of the field at that location. There are all kinds of fields in the universe.

In fact, every single fundamental particle today has a corresponding field. And in any field, the values can change over time. For the most part, those fields  have a value close to zero.

You can think of these fields  as a calm surface of a pond, sitting pretty flat. But sometimes they get jiggled a little. And to understand what happens when a quantum field gets jiggled, let’s stick with the pond analogy for a sec.

When raindrops fall into a pond, they create ripples spreading outward from each drop. Those ripples are little oscillations. And in this case, they cause water to move up and down.

When a quantum field gets jiggled, it also creates an oscillation, and that oscillation moves through the field like a ripple. As that ripple passes, the values of that field oscillate around their zero point, just like water moving bobbing  up and down with a wave. That little jiggle that the field does is known as an excitation.

It’s the thing that carries energy around a field… and that’s something we know better as a particle. So, particles themselves are essentially vibrations of a field. But here’s where the similarity with a ripple in a pond ends.

Because that excitation in a quantum field doesn’t look like a regular wave. In a lake, if you drop tinier and tinier rocks in the water, you will always get ripples; they’ll just get smaller and smaller. But in a quantum field, if you don’t jiggle it just the right amount, you will barely get a ripple at all.

The field will just stay flat. That’s because this is the  realm of quantum mechanics, so everything is quantized. In other words, values aren’t continuous.

Everything comes in chunks, and there is no in-between each chunk. It’s similar to how light falling on an atom has to have just the right wavelength in order to bump an electron up to a higher energy level. A quantum field needs to receive just the right amount of jiggle to get excited and create a particle.

In other words, that jiggle has to match the natural frequency of the field. So the properties of each quantum field — the ways in which they resonate — are what define the properties of the particles that emerge from them. As for how you jiggle a quantum  field in the first place… different fields can do that to each other.

Not all fields interact with each other, but some are closely related, so a jiggle in one can set  off a jiggle in another. And what you end up with is a never-ending collection of vibrating fields that create all the stuff in the universe. So from beginning to end, from the most fundamental to the most complex, resonant vibrations underlie  the structure of the universe as we know it.

And there are a lot of wonders to behold, from immense to tiny. For example, much of North America will be experiencing a total solar eclipse on April 8th, 2024. Those only happen in specific  locations once a century or so, so if you’re in the path of totality – from southwestern Mexico all the way up past Dallas, Detroit, and Toronto – you do not want to miss this one.

And you won’t if you order our SciShow eclipse glasses, which are safety certified by  folks whose safety opinions matter, and will let you look at the Sun during the eclipse without hurting your eyes. thanks for watching this video [ OUTRO ]