Why Is Everything Made Of Atoms?

“If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one

sentence passed on to the next generations of creatures, what statement would contain

the most information in the fewest words?

I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it)

that all things are made of atoms.”

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The ship rattles as it stretches out into

the void, beginning the adventure of a lifetime.

The nervous crew are off on an epic journey

to visit their home world's only natural satellite. Though similar in concept to the journey undertaken

by the Apollo astronauts when they left Earth for the Moon - this voyage is very different.

When Armstrong and Aldrin headed for history on the lunar surface, they needed only to

travel a distance equal to the width of thirty Earths.

Our intrepid travellers must cover a distance equal to more than 63,000 times the diameter

of their home world. Compared to the crew´s destination though,

the Moon is a celestial snail. It crawls around the Earth once a month at a speed of 1000

metres per second. That may sound fast, but this satellite is whipping around at over

two million metres per second or just under one per cent the speed of light. It's moving

so quickly that it completes 6.5 quadrillion orbits each and every second.

For it is no moon.

And this is no solar system.

Our travellers are not exploring the astronomical realm, but the atomic one.

They are brave atomonauts, adrift inside the hydrogen atom. Departing from the solitary

proton at its centre, they are in search of the lone electron that encircles it.

But their mission is a lot harder than it first appears. The electron only orbits the

proton like a moon orbits a planet in the simplified Bohr model of the atom, named after

the Danish physicist Niels Bohr. Modern quantum physics says that we can never know for certain

where the electron actually is – we can only say where it's most likely to be. The

blur of all its possible paths creates a cloud around the nucleus. Our atomonauts could therefore

never land at their destination - only float into the fog of possibility.

These atoms are the universe's lego bricks. Vast galaxies swirl in the void and distant

stars keep vigil over the night, but they are all built out of atoms. As we all are.

Indeed, there's an entire cosmos inside you. The number of atoms in your body alone exceeds

the total number of stars in the entire observable universe. Even if you started counting them

at a rate of a billion a second, it would still take you far longer than the current

age of the universe to complete the task. And as we have seen - even within those atoms

themselves, there are entire complex systems to explore.

And yet… at the very beginning of time the number of atoms in the universe was precisely

zero. Not a single atom in the entirety of the cosmos.

So how did we end up here? Where did the very first atom come from?

And just why is everything made of atoms?

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A wicked wind howls across the Black Sea. Waves swell and crash as the previously mirror

smooth water is tossed and churned. Marooned on a kayak amid this maelstrom is

a pair of newly-weds.

They are refugees, fleeing Ukraine to escape

from the Russian regime. Yet this is not a twenty-first century story.

The year is 1932 and the couple stranded in the tumult are the physicist George Gamow

and his wife Lyubov, who he affectionately calls Rho after the Greek letter.

What could drive this young couple to risk their lives on such a perilous voyage?

The early 1930s witnessed a big shift in the way the Soviets treated their scientists and

intellectual ideas and foreign trips were increasingly tightly policed. Gamow wants

to present his research at a large scientific conference in Rome, but needs a new passport.

His application is constantly kicked into the long grass by bureaucrats in Leningrad

who promise progress, but instead deliberately run down the clock. He never goes to the Italian

capital. Yet his endless visits to the passport office

have one significant upside: it is there that he meets Rho. They marry soon after and within

a year the newly-weds agree to flee. They pore over maps looking for the surest means

of escape from the Soviet Union. And so they settle on the Black Sea, leaving

Gamow's birthplace of Odessa to head for Turkey. Gamow still has a Danish motorcycle licence

from his days collaborating with the physicist Niels Bohr in Copenhagen, and so the plan

is to wash up on a Turkish beach, pretend to be Danish and ask to be taken to the Danish

embassy in Istanbul. Their journey couldn't have started better.

The water is calm and the breeze is gentle. But when they awake before sunrise the second

day the weather is already turning. By the evening, the situation intensifies and soon

becomes perilous. By the time the storm abates they are exhausted to the point of hallucination.

Drifting alone on the open water, strong winds buffet the boat all the way back to Crimea.

Despite this setback, eventually Gamow and Rho do escape. They secure passage to a scientific

conference in Belgium and after the conference, Marie Curie helps the couple extend their

stay in Western Europe. Never to return to the Soviet Union, they finally headed to the

United States in early 1934. This entire odyssey has unfolded before Gamow's

thirtieth birthday. Six years later, Gamow is granted American

citizenship. Free from the shackles of oppression, he is now able to continue his work.

And it is this work that would turn out to be pivotal in our understanding of physics

- for it would change the way we think about the history of the universe forever.

In 1929, three years before Gamow's exploits on the Black Sea, the American astronomer

Edwin Hubble had shocked the astronomical establishment with evidence that the universe

is expanding. If the universe is growing day by day then it was smaller yesterday and smaller

still a week ago. Keep rewinding the clock and there was a time when every part of the

modern universe was concentrated down into an incredibly small space before it expanded

outwards. The Big Bang. Except that it wasn't such a new idea to Gamow.

The Russian physicist Alexander Friedmann had already predicted the universe's expansion

back in 1925 and the pair had lengthy discussions about it during Gamow's time in Leningrad.

Gamow spent much of his early time in America working on something else – the ultimate

power source of stars. Yet the focus of his attention was shifting. In October 1945, Gamow

writes a letter to his old friend Niels Bohr to mark the Dane's 60th birthday.

The letter reveals that Gamow was starting to apply his work on the internal mechanics

of stars to the origin of matter in the early universe immediately after the Big Bang.

Up until this point cosmologists had assumed that the early universe was dominated by matter,

the stuff that all visible structure is made of, from stars and planets to galaxies and

galaxy clusters. Yet Gamow began to suspect otherwise. History wavers on who truly deserves

the credit, but it could have been Gamow's student Ralph Alpher. In his doctoral dissertation

Alpher claimed that the early universe wasn't dominated by matter, but by electromagnetic

radiation. This electromagnetic radiation would supposedly dominate the early universe

for a full fifty thousand years after the Big Bang.

Physicists have another word for electromagnetic radiation: light. We may use that word for

the light our eyes can see, but there's more to it than that.

Just as there are frequencies of sound too low or high for our ears to hear, there are

frequencies of light too low or high for us to see.

When a physicist uses the word light they mean the radiation that spans the full range

of these frequencies, from gamma-rays and X-rays at the high frequency end to microwaves

and radio waves at the other. When you use a microwave to heat your dinner, you're actually

cooking the food using low-frequency light. And so light and matter were trapped together

in the nascent universe. After 100,000 seconds of expansion, the entire universe was still

denser than the air you're breathing right now - and continued for thousands of years

to be dense enough for sound waves to travel through.

Sound waves of such low frequency that they'd need to be squashed by 100 septillion times

– that's 1 followed by 26 zeroes – just to push them into the range of human hearing

- something that in 2013 John G Cramer at Washington University used data from the early

universe to reproduce:

Cosmologists call these sound waves baryon

acoustic oscillations and they can still be detected today using facilities such as the

Sloan Digital Sky Survey. As the universe kept expanding it continued to stretch out

these sound waves, shifting them to ever lower frequencies.

But then there came a point when everything changed.

It is one of the most important events in the entire history of the universe – and

it was predicted by none other than Alpher and Gamow. It is called recombination and

it also opened the floodgates for the first light to come streaming out into the early

universe. But what recombined exactly?

And what does this first light have to do with the first atom?

The feeling of claustrophobia rises by the second. You're trapped.

Whichever way you turn just leads to a blocked path.

Have you seen these walls before? Did you turn right or left at this junction earlier?

No matter how hard you try, you just can't figure out how to escape.

And that is not surprising. Because there is no escape.

You are trapped in an impenetrable maze. This series of never-ending dead-ends is exactly

what light encountered after the Big Bang. Everywhere light tried to go it bumped into

insurmountable obstacles in the form of sub-atomic particles. And yet the universe didn't begin

as such a labyrinth. In the very beginning there was none of this matter to get in the

way. For the faintest sliver of a second, just after its birth, it was free.

But very quickly light turned into its own captor, snapping the shackles shut on itself.

This happened because light leads a double life. Like the vampires and werewolves of

myth and folklore it can shape-shift into something else: matter. Light is a form of

energy, and energy and matter are two sides of the same cosmic coin. They are completely

interchangeable. And the more energetic the light, the higher the likelihood it will change

into matter. Within a trillionth of a second after the

Big Bang some of the universe's energy is converted into particles of matter that start

popping into existence, flooding the universe with fundamental particles - everything needed

to build atoms, including electrons. Yet we'll still have to wait hundreds of thousands of

years for these particles to actually coalesce into the first atom.

We may already have electrons, but to make a hydrogen atom, like the one explored by

our atomonauts, we also need a proton. Unlike electrons, they are built out of something

else: quarks – fundamental particles that also appeared during light's partial metamorphosis

into matter. Quarks come in a menu of different flavours,

but the most important ones for our story of atom formation are the up quark and the

down quark. Up quarks carry a positive charge and down quarks a negative charge. A proton

is made of two up quarks and one down quark, giving a proton an overall positive charge.

Yet these quarks are not natural bedfellows. Electric charges act like the poles of a magnet

– opposites attract, but like charges repel one another. How can two positively charged

up quarks happily sit side by side inside a proton?

The solution to this puzzle lies with forces, the glue needed to stick the first atom together.

Physicists know of four fundamental forces in the universe. Two are familiar to us: gravity

and electromagnetism. Light is an electromagnetic wave and it is electromagnetism that repels

like magnets and quarks from one another. Down in the atomic world, two less familiar

forces are at a play. The weak nuclear force governs radioactivity, but it's the strong

nuclear force that really dominates here. It is one duodecillion times stronger than

gravity. That's ten followed by thirty-eight zeroes – significantly more zeroes than

there are stars in the entire observable universe. The strong nuclear force is also one hundred

times stronger than the electromagnetic force. So two quarks with the same charge may want

to push away from one another, but the strong nuclear force can override this electromagnetic

instinct and keep them tied together. There is a catch, though.

The strong nuclear force may be the king of the forces, but the kingdom it governs is

tiny. It only has dominion over the most minute of distances: about a trillionth of a millimetre.

Initially energies are too high for quarks to bind together through the strong force.

When the quarks first formed, the temperature of the universe was over one quadrillion degrees.

Though they pass very close to each other, the quarks collide with such high energy that

they cannot stick. But the new universe is expanding all the

time. It cools as it grows and particles within it slow down. After the first millionth of

a second the temperature drops to a mere one trillion degrees and the first protons are

able to form. Neutrons form too, the other kind of particle you'll find in an atomic

nucleus. They are made of one up quark and two down quarks.

Simple enough, you might think. But again, as with Bohr´s model of the atom,

neutrons and protons are not quite that straightforward.

Indeed, the more physicists learn about the proton, the more downright weird it gets.

To quote Mike Williams, physicist at the Massachusetts Institute of Technology: “This is the most complicated thing that

you could possibly imagine,” For one thing, together the three quarks – known

as valence quarks - actually make up just one per cent of the proton's mass. The rest

is taken up by particles called gluons. They are the particles that carry the strong nuclear

force. It's by exchanging gluons that the trio of valence quarks are able to bind together

into a proton. Yet it gets a lot stranger. Occasionally gluons

pick up enough energy that they can do some shape-shifting of their own, turning into