Chapter 8: Before There Were Atoms

Night 84: The Drill

The alarm on day 84 was planned, but the crew did not know the exact minute. The ground had told them that an emergency drill would happen sometime in the afternoon. That was all. Noor was halfway through a session on the exercise bicycle when the tone sounded through the station, loud and steady, followed by the calm voice of Tomás announcing that this was a drill.

Everyone knew what to do, because they had practised it many times on the ground. Noor unclipped her shoes from the bicycle, pushed off towards the place where the emergency masks were stored and pulled one over her face. Ade was already there. Tomás read out the first steps of the emergency procedure, and each of them answered with their part. They checked the readings, closed certain hatches in the right order and moved to the places they would go in a real emergency, near the spacecraft that could take them home.

The ground watched and timed everything. After about an hour, the drill ended, and the crew had a short talk with the ground about what had gone well and what could be faster. One hatch had taken longer to close than it should have. A checklist page had been in the wrong order. These small things were written down, so that they could be fixed before they ever mattered.

Noor had always thought that drills were one of the most ordinary parts of any job. People in offices, factories, schools and hospitals on the Earth also practise leaving the building when an alarm sounds. They walk down the stairs, gather in a car park or a yard, and wait while someone counts them. Most of the time, it feels a little silly. But the point of a drill is to make the right steps so familiar that, on a real bad day, nobody has to think about them.

The drill was a success, but it left Noor awake that night. It was not fear exactly. It was the feeling that her body had prepared for something that never came. She lay in her sleeping bag, tied to the wall of her small cabin, and listened to the hum of the fans. Her mind kept going back, step by step, through the procedure. And then, because her mind liked to go back, it went further back, past the drill, past the day, all the way to the questions that she had been thinking about on these nights.

Sami had written earlier that evening. He had asked a question that she could not answer quickly: "If you keep going back in time, to before the first minutes, what do you find? And is there a point where nobody knows anymore?" It was a good question for a sleepless night. The honest answer has two parts. Going back, we find a world stranger and simpler than any we know. And yes, there is a point where nobody knows.

Going Further Back

On the previous night, we saw the first few minutes, when protons and neutrons joined to make helium. Before that, the universe was even hotter, and protons and neutrons moved freely. Tonight we go further back again. The further back we go, the hotter and denser everything becomes. And as the temperature rises, the things that we normally think of as solid and permanent begin to come apart.

Here is a way to picture it. Think of ice in a pan. When you heat it, it becomes water. Heat it more, and the water becomes steam. The same molecules are there, but they behave differently at each temperature. Now imagine heating the steam far beyond anything in a kitchen. The water molecules break into atoms of hydrogen and oxygen. Heat them more, and the electrons are pulled away from the atoms. Heat them further still, and even the nuclei break apart into protons and neutrons. The early universe went through all of these steps in the other direction, from the hottest stage to the coolest, as it expanded and cooled.

So if we run the film backwards from the first minutes, we come to a time when the universe was a thick soup of free protons, neutrons, electrons and light, all moving at enormous speeds. Earlier still, we come to a time when even protons and neutrons did not yet exist. They are made of even smaller pieces, called quarks. A proton is a small group of three quarks, held together by a force so strong that, in today's universe, quarks are never found alone.

Electrons are different. As far as anyone has been able to measure, an electron is not made of smaller pieces at all. It seems to be one of the true basic particles of nature, like the quarks themselves. So the list of the smallest building blocks of ordinary matter is surprisingly short: two kinds of quarks, which make protons and neutrons, and the electron.

When the universe was extremely young, it was so hot that the quarks were not locked inside protons and neutrons. They moved freely in a kind of hot, dense mixture, together with the particles that carry the strong force between them. Then, when the universe was about a millionth of a second old, it had cooled enough for the quarks to come together in groups of three. Protons and neutrons formed. From then on, they were the building blocks that the first minutes would use.

A millionth of a second sounds like nothing at all. It is far shorter than a blink. But in the young universe, a great deal happened in such short times, because everything happened so fast. Physicists sometimes say that the early universe should be measured not in ordinary seconds but in how much it had cooled. Each step down in temperature brought a new kind of order, as the soup slowly turned into the pieces of our world.

Small Drops of Early Heat

How can anyone study a time so short and so hot? Part of the answer is that scientists can recreate tiny drops of it on the Earth. In large machines called particle accelerators, the centres of heavy atoms are sped up to almost the speed of light and then made to crash into each other. For a tiny fraction of a second, in a space far smaller than a grain of dust, the crash creates temperatures like those of the very young universe.

In those tiny drops, the protons and neutrons of the crashing atoms melt into their quarks for a moment, and the hot mixture forms. Then, almost at once, it cools and turns back into ordinary particles, which fly out into the detectors around the crash. By studying what comes out, scientists can learn how that hot mixture behaves. In this way, a working laboratory on the Earth becomes a small window onto the first millionth of a second.

These experiments have brought surprises. Many physicists expected the hot mixture of quarks to behave like a thin gas. Instead, it behaves more like a liquid, and one that flows almost without any stickiness at all, more smoothly than water or any other liquid on the Earth. This tells us something about the young universe that nobody could have guessed by thinking alone. It is a good reminder of why experiments matter.

These machines are some of the largest instruments that people have ever built. Thousands of engineers, technicians and scientists work on them, in shifts, day and night. Some check cables. Some write the computer programs that sort the measurements. Some watch screens through the night and call for help when something looks wrong. Like the station, these machines are run by many people doing ordinary jobs carefully, and together those jobs reach back to the beginning of time.

It is important to be clear about what this does and does not mean. The machines do not create a new universe, and they are not dangerous in that way. They create, for a tiny moment, the same temperature as the early universe, in a very small space. Because the laws of physics are the same here and there, what happens in that small space tells us how the early universe behaved at that temperature. The further back we try to go, the higher the temperature we would need, and at some point it becomes far higher than any machine could ever reach.

Back to the time when protons and neutrons formed, and even somewhat earlier, scientists are fairly confident about the broad story, because the temperatures of those times can be tested in this way. Before that, the story becomes less and less certain. Physicists still have good ideas about earlier times, and they use the same laws as far as those laws can be tested. But the closer they come to the very beginning, the less firm the ground becomes.

The People Who Found the Mirror Particles

One of the strangest parts of tonight's story is antimatter. It sounds like something from a science-fiction film, but it is real, and its discovery is a good example of how science sometimes works. Around 1930, a physicist was working on the equations that describe how electrons behave when they move very fast. The equations seemed to say something unexpected. They seemed to allow a twin of the electron, with the same weight but the opposite electric charge.

At first, many physicists did not know what to make of this. Perhaps it was only a strange feature of the mathematics. Then, in 1932, a young researcher who was photographing the tracks left by particles arriving from space saw a track that curved the wrong way. It was a particle like an electron, but with a positive charge. The twin was real. It was named the positron. Later, scientists found that every kind of particle has such a mirror twin. Together, these twins are called antimatter.

Antimatter is not a story only for physicists. Today, it is made in laboratories, and some hospitals use it every working day. In one kind of medical scan, a patient receives a small, carefully controlled amount of a special substance that gives off positrons inside the body. When a positron meets an ordinary electron, the two disappear and turn into a small flash of energy, and the machine around the patient detects that flash. Doctors use such scans to see how parts of the body are working. Somewhere tonight, a nurse or a technician on a night shift may be preparing exactly such a scan.

That disappearing act is the key to tonight's puzzle. When a particle meets its antimatter twin, both vanish and leave only energy behind. And in the hot young universe, particles and their twins were being made from energy and destroyed again all the time. If there had been exactly equal amounts of matter and antimatter, then as the universe cooled, they would have met and destroyed each other completely. Nothing would have been left except light. There would be no stars, no planets and no people.

But something was left. For reasons that we do not yet understand, there was a very small surplus of matter, roughly one extra particle for every billion pairs. When the great meeting was over, the pairs had turned into light, and the small surplus remained. Everything we see today, every star and every galaxy, is made from that tiny leftover. Why the universe made a little more matter than antimatter is one of the great open questions of physics. Scientists are searching for an answer, but nobody knows yet.

Where Today's Physics Stops

Now we come to the second part of Sami's question. Is there a point where nobody knows anymore? Yes, there is. If we keep running the film backwards, past the first millionth of a second, the universe becomes hotter and denser without any limit that we know of. At some point, it becomes so hot and so dense that our two best descriptions of nature no longer fit together.

The first of these descriptions is Einstein's theory of gravity, which explains how large things such as planets, stars and galaxies move and how space itself can stretch. The second is the theory that explains the world of very small things, such as atoms and quarks, which physicists call quantum theory. Each theory works extremely well in its own area. Each has been tested many times. But in the very first moment, when the whole universe was both extremely small in its distances and extremely heavy with energy, both theories would be needed at once. And nobody has yet found a way to join them into one theory that works there.

You can picture the problem like this. Imagine two very good maps. One shows the whole country, with its mountains and rivers, but it has no detail smaller than a town. The other shows a single street, house by house, but nothing beyond it. Each map is excellent for its own purpose. But if you need to find your way through a place that is both enormous and full of tiny detail, neither map is enough on its own, and nobody has yet drawn the map that combines them.

So at the very first moment, today's physics stops working. That moment is so short that there is no ordinary word for it. It is far shorter than a millionth of a second, shorter than anything that any clock could ever measure. What happened then, and whether "then" even has a meaning, is not known. Some scientists are working on new theories that might one day describe it. Some of their ideas are interesting, but none of them has yet been confirmed by evidence.

It is important to say this plainly, because it is often said wrongly. The theory of the Big Bang does not describe the very first moment. It describes what happened after it: how a hot, dense young universe expanded and cooled, made its first elements, released its oldest light and later formed stars and galaxies. That part of the story is supported by many kinds of evidence. The first moment itself, and any question of what came before it, is still beyond what we know.

There is no shame in this. A good map is honest about where it ends. Old sailors' maps sometimes left blank spaces in the places they had not yet explored. Those blank spaces were not failures. They were invitations. In the same way, the blank space at the very beginning of the universe is one of the most interesting places in all of science, and many people are working, patiently, to fill a little of it in.

A Message to Sami

Somewhere over a dark ocean, Noor finally felt sleep coming. Before it did, she reached for her tablet and wrote to Sami, who would be on his break by now: "You asked if there is a point where nobody knows. There is. The further back you go before the first millionth of a second, the less certain things get, and at the very first moment, nobody knows at all. Not even the best scientists. It is all right not to know."

Sami answered a little later. He said that his manager also did not know everything, but pretended to, and that he liked the scientists better. Noor smiled into the dark of her cabin. Then she switched off the tablet and let the hum of the fans carry her to sleep.

Some nights after work, your own mind may also keep running, going back over a day that is already finished. On those nights, there is a strange comfort in remembering that even the universe has a beginning that nobody fully understands. Not every question needs an answer before morning. Some questions can be carried gently, for a lifetime, and still be good company.

Common Misunderstandings

Many people think that scientists know exactly what happened at "time zero", the very first instant of the universe. They do not. As we saw tonight, our best theories stop working at the very first moment, and nobody has yet found a theory that works there. Scientists can describe with confidence what happened from a tiny fraction of a second onwards, and they become more confident the later the time. But the first instant itself is still unknown, and honest scientists say so.

Many people also think that antimatter is only an invention of science fiction. It is real. Scientists make small amounts of it in laboratories, particles of antimatter arrive naturally from space, and some hospital scans use it every day. What is true is that antimatter is very rare in today's universe, because almost all of it met matter and disappeared long ago. That is why we never meet antimatter in daily life, and why the small surplus of matter is such an important puzzle.

Finally, many people imagine that "the universe was very small" means that it was a small object, like a glowing ball, sitting inside a larger, empty space. That is not what scientists mean. There was no outside space for the universe to sit in. When scientists say that the universe was small, they mean that the distances between all the things in it were much shorter than they are today, and that everything was packed very closely and was very hot. The universe did not expand into space. Space itself stretched. On the next night, we will move forward again, to a quiet and dark time after the oldest light, when the universe was waiting for its first stars.