The Universe in Your Hand

A Journey Through Space, Time, and Beyond

Flatiron Books

Contents

Part One

The Cosmos

1 A Silent Boom

Picture yourself on a faraway volcanic island on a warm, cloudless summer night. The surrounding ocean is as still as a lake. Only the tiniest of waves wash against the white sand. All is quiet. You are lying on the beach. Your eyes are closed. The warm, sun-baked sand heats up air saturated with sweet, exotic scents. There is peace all around.

A wild shriek in the distance makes you jump and stare into the darkness.

Then: nothing.

Whatever shrieked is now quiet. There is nothing to be afraid of after all. This island may be dangerous for some creatures, but not for you. You are a human, the mightiest of predators. Your friends will soon be joining you for a drink and you are on holiday, so you lie back on the sand to focus on thoughts worthy of your species.

A myriad of tiny lights flickers throughout the vast night sky. Stars. Even with the naked eye you see them everywhere. And you remember questions you had as a child: what are they, these stars? Why do they flicker? How far away are they? And now you wonder: will we ever really know? With a sigh, you relax back on the warm sand and put these silly questions aside, thinking, why should we care?

A tiny shooting star gently streaks across the sky overhead and, just as you are about to make a wish, the most extraordinary thing happens: as if to answer your last question, 5 billion years suddenly pass and the next thing you know, you are no longer on a beach, but in outer space, floating through emptiness. You can see and hear and feel, but your body is gone. You are ethereal. Pure mind. And you don't even have the time to wonder what just happened or to shout and call for help, for you are in the most peculiar of situations.

In front of you, a few hundred thousand miles ahead, a ball is flying against a background of tiny distant stars. It glows with a dark orange light, moves towards you, spins. It doesn't take you long to figure out that its surface is covered with molten rocks and that what you are facing is a planet. A liquefied planet.

Shocked, a question comes to your mind: what monstrous source of heat could liquefy an entire world like this?

But then a star, immense, appears to your right. Its sheer size, compared to that of the planet, is just astounding. And it spins too. And it also moves through space. And it seems to be growing.

The planet, although much closer, now looks like a child's tiny orange marble facing a gigantic ball that continues to grow at an astonishing rate. It is already twice the size it was a minute ago. Presently, it has a red hue, and it angrily ejects huge filaments of million-degree-hot plasma that blast through space at what seems to be very close to the speed of light.

Everything you see is of a monstrous beauty. In fact, you are living through one of the most violent events the universe can provide. And yet there is no sound. All is silence, for sound does not spread in the vacuum of space.

Surely the star won't be able to keep growing at this rate; and yet it does. It is now beyond any size you could have imagined and the liquefied planet, pounded by energies beyond its strength, is blown to nothingness. The star did not even notice. It keeps growing, reaches about a hundred times its initial size and then, quite suddenly, it explodes, firing all the matter it was made of into outer space.

A shock wave passes through your ghostly form, and then only dust remains, blown in all directions. The star is no more. It has become a spectacular and colourful cloud that now spreads into the interstellar void at a velocity worthy of gods.

Slowly, very slowly, you come back to your senses and, as you realize what just happened, a strange lucidity fills your mind with a fearsome truth. The star that died was not a random star. It was the Sun. Our Sun. And the molten planet that vanished within its brightness was the Earth.

Our planet. Your home. Gone.

What you witnessed was the end of our world. Not a speculative end, not a far-fetched fantasy of supposedly Mayan origin. The real one. One that mankind has known would happen since some time before you were born, 5 billion years before what you just saw.

* * *

As you try to pull these thoughts together, your mind is instantly sent back to the present, inside your body, on the beach again.

Your heart races and you sit up and look around, as if waking from a strange dream. The trees, the sand, the sea and the wind are there. Your friends are on their way. You can see them in the distance. What happened? Did you fall asleep? Did you dream what you saw? An uncanny feeling spreads throughout your body as your queries start to shift: could it have been real? Will the Sun really explode one day? And if so, what will happen to humanity? Can anyone survive such an apocalypse? Will everything up to the very memory of our own existence vanish into cosmic oblivion?

Gazing once more up at the starlit skyscape above, you desperately try to make sense of what happened. Deep down, you know that you did not just dream it all. Although your mind is back on your beach, reunited with your body, you know you really did travel beyond your time, into a faraway future, to see something no one should ever see.

Slowly breathing in and out to calm down, you start hearing strange noises, as if the wind, the waves, the birds and the stars are all whispering a song that only you can hear, and you suddenly understand what they are all singing about. It is both a warning and an invitation. Of all possible futures available, they murmur, only one path will allow humanity to survive the inevitable death of the Sun and most other catastrophes.

The path of knowledge, of science.

A journey open to humans only.

A journey that you are about to take.

* * *

Another wild shriek pierces the night, but you hardly hear it this time. As if a seed just planted in your mind was already starting to sprout, you feel the urge to find out what is known about this universe of yours.

Humbly lifting your sight again, you now gaze at the stars with the eyes of a child.

What is the universe made of? What lies in the vicinity of the Earth? And beyond? How far can one look? Is anything known about the universe's history? Does it even have one?

As the waves gently wash over the shore, as you wonder if one will ever be able to probe these cosmic mysteries, the twinkling of the stars seems to lull your body into a half-conscious state. You can hear your approaching friends' conversations but, strangely, you already feel the world differently than you did a few minutes ago. Everything seems somehow richer, more profound, as if your mind and body were both part of something much, much bigger than anything you had ever thought of before. Your hands, your legs, your skin ... Matter ... Time ... Space ... Intertwined fields of forces all around you ...

A veil you didn't even know was there has been lifted from the world to reveal a mysterious and unexpected reality. Your mind yearns to be back among the stars, and you have the feeling that some extraordinary journey is about to take you very far away from your home world.

2 The Moon

If you're reading this, it means you've already travelled 5 billion years into the future. A good start, by anyone's standards. So you should be confident that your imagination is working well, and that is perfect, because imagination is all you'll need to travel through space and time and matter and energy, to discover what is known about our reality from an early twenty-first-century perspective.

You didn't ask for it, but you did happen to see what fate awaits mankind, indeed all life forms on Earth, if nothing is done to understand how nature works. To survive in the long run, to avoid being swallowed by a furious dying Sun, our only chance is to learn how to take our future into our own hands. And for this to happen, we need to unravel the laws of nature itself, and learn how to put them to good use. It's fair to say that we have a lot to get through. In the following pages, however, you shall see pretty much everything that is known so far.

Travelling throughout our universe, you will discover what gravity is about and how atoms and particles interact with each other without ever touching each other. You will find out that our universe is mostly made up of mysteries and that these mysteries have led to the introduction of new types of matter and energy.

And then, once you've seen everything that is known, you will jump into the unknown and see what some of the brightest theoretical physicists of today are working on to explain the very strange realities we happen to be a part of. Parallel universes, multiverses and extra dimensions will enter the picture. After that, your eyes will probably be shining with the light of knowledge and wisdom that mankind has been gathering and improving for millennia. But you should prepare yourself. Discoveries made during the past decades have changed everything about what we believed to be true: our universe is not only unfathomably bigger than expected, it is also immensely more beautiful than any of our ancestors could have imagined. And while we're at it, here is another piece of good news: to have figured out as much as we already have makes us humans different from all the other life forms that have ever lived on Earth. And that is a good thing, for most of the other life forms became extinct. The dinosaurs ruled the surface of our planet for about 200 million years, whereas we have done so for no more than a few hundred thousand. They had plenty of time to start questioning their environment and figure a few things out. They didn't. And they died. Today we humans could at least hope to detect a threatening asteroid early enough to try to deflect it. So we already have some powers they did not have. It might be unfair to say it, but with hindsight we might thus link the dinosaurs' extinction to their lack of awareness of theoretical physics.

* * *

For now, you still are on the beach, though, and the memory of the dying Sun is still vivid in your mind. You don't have that much insight yet and, to be honest, the twinkling dots that stud the night seem utterly oblivious to your existence. The life and death of earthly species makes no difference to them whatsoever. It appears that time, in outer space, works on scales that your body cannot grasp. The entire existence of a species here on Earth probably lasts no more than a snap of the fingers for such distant shining gods ...

Three hundred years ago, one of the most famous and brilliant scientists of all time, British physicist and mathematician Isaac Newton, the man who gave us gravity from Cambridge University, England, actually thought in such terms about time: for him, there was the time of humans, felt by us all and measured by our clocks, and there was the time of God, which is instantaneous, which doesn't flow. From the point of view of Newton's God, the infinite line of human time, stretching backward and forward into infinity, is but an instant. He sees it all in one blink.

* * *

You are not God, though, and as you watch the stars, as a friend of yours silently pours you a drink, the immensity of the task at hand starts to feel overwhelming. All this is too big, too far away, too strange ... Where to begin? You are not a theoretical physicist ... but you are not the type to give up either. You have eyes and your mind is curious, so you lie down on the sand and start by focusing on what you can see.

* * *

The sky is mostly dark.

And there are stars.

And in between the stars, your naked eye perceives a dim band that glows with a faint whitish light.

Whatever this light is, you know the band is called the Milky Way. Its width looks to be about ten times that of a full Moon. You stared at it many times when you were younger, but not that much recently. As you now see it, you realize that it is so conspicuous that it must have been known to your ancestors since forever, and you are right. Ironic to think that, after centuries during which men and women debated its nature, we now know what it is – although light pollution makes it invisible from most inhabited places.

From your tropical island, however, its presence is overwhelming and, as the Earth spins as the night advances, the Milky Way moves through the sky, like the Sun during the day, from east to west.

The possibility that the future of humanity lies somewhere out there, beyond the Earth's sky, starts to become real in your mind, and spellbinding. Focusing, you wonder if it is possible to see all there is in the universe with the naked eye. And then you shake your head. You know that the Sun, the Moon, some planets like Venus, Mars or Jupiter, some hundreds of stars and that fuzzy streak of whitish dust called the Milky Way don't add up to being Everything. There are mysteries hiding up there, out of sight, between the stars, mysteries that are just waiting to be unravelled ... If only you could probe it all, what would you do? You would start with the vicinity of the Earth, of course, and then ... then you'd shoot away and go as far as possible, and then ... Your mind obliges!

As amazing as it sounds, your mind does start to move away from your body, upwards, towards the stars.

A spinning sensation of vertigo hits you as your body, and the island it is lying on, recede rapidly beneath you. Your mind, shaped as an ethereal you, is heading up, and east. How that is even possible, you do not have a clue, but there you are, higher than the tallest of mountains. A very red Moon appears, suspended above a distant horizon, and in far less time than it takes to say it, you find yourself out of the Earth's atmosphere, flying across the 236,000 miles of emptiness that separate our planet from our only natural satellite. From space, the Moon appears as white as the Sun.

Your journey through knowledge has begun.

* * *

As only a dozen humans have done before, you've reached the Moon. Your ghostly body is now walking on it. The Earth has disappeared below the lunar horizon. You are on its so-called dark side, the side that never sees our planet. There is no blue sky, nor any wind, and not only do you see many more stars above your head than from anywhere on Earth, they don't twinkle. All this because there is no atmosphere on the Moon. On lunar soil, space begins a millimetre above the ground. No weather ever erases the scars that scatter its surface. Craters are everywhere, frozen memories of what once hit that barren soil.

As you start walking towards the Earth-facing side of the Moon, the history of its birth magically pours into your eager mind and you stare, dumbfounded, at the ground beneath your feet.

What violence!

About 4 billion years ago, our young planet got hit by another one, the size of Mars, which tore a huge chunk of it off into space. During the following millennia, all the debris from that collision settled into a single ball in orbit around our world. When that was done, the Moon you are now standing upon was born.

Were it to happen today, such a collision would be more than enough to wipe out all life forms on Earth. At the time, though, our world was bare, and it is funny to think that without such a catastrophic bang, we would have no Moon to illuminate our nights, no significant tides, and life as we know it probably wouldn't exist on our planet. As the blue Earth appears in front of you, above the lunar horizon, you realize that catastrophic events, on a cosmic scale, can be for the best just as they can be for the worst.