The line started at dawn and stretched all the way to the end of the world.

I stood at the back of it, shivering in the cold mountain air, watching the scientists ahead of me file into the particle accelerator one by one. They moved with a quiet dignity that was almost religious, like pilgrims walking to a shrine, like soldiers marching to a battle they knew they would not survive.

Each one of them was a top scientist in their field. A physicist who had spent forty years studying quantum gravity. A chemist who had discovered a new element. A biologist who had mapped the genome of a species that had existed for two billion years. Each one of them had spent their entire life preparing for this moment—the moment when the accelerator would reveal the ultimate truth about the universe.

And each one of them was willing to die for it.

I was a young physicist, twenty-eight years old, and I had spent the previous five years working on a theory of everything that I knew, with absolute certainty, was wrong. I had published papers, given lectures, defended my work at conferences, and slowly, painfully, I had come to understand that the theory was wrong. Not partially wrong. Not approximately wrong. Completely, fundamentally, irredeemably wrong.

And I had spent five years of my life building a house of cards on a foundation of sand.

The man ahead of me in line was a mathematician. He had solved a problem that had puzzled mathematicians for three hundred years. He was sixty years old, with thinning gray hair and glasses that were cracked on one side. He turned to me as he waited for his turn to enter the accelerator.

"Do you know what the truth is?" he asked.

"No," I said.

"I don't either," he said. "That's the point. The truth is not something you know. It's something you become. When you walk into that accelerator, you don't learn the truth. You become the truth. And then you die."

He smiled at me, a small sad smile, and walked into the accelerator.

The door closed. There was a flash of light, and then silence.

I thought about my father. He had been a coal miner, and he had never heard of quantum gravity or quantum chemistry or whatever it was that the people in front of me had spent their lives studying. He had never heard of the particle accelerator or the universe or the truth.

But he had known something. He had known that "the sky will not fall."

I did not know what that meant. Not really. It was a miner's phrase, passed down through generations, a phrase that meant nothing and everything at the same time. The sky will not fall. The world will continue. The coal will keep burning.

My father had died in a mine collapse. He had been underground when the tunnel collapsed, and he had not come out. I was eight years old when they brought him home in a box that was too small for him.

I had spent my entire life trying to understand the universe because I could not understand why my father had died. If the universe was rational, if it was governed by laws that could be discovered and understood and predicted, then my father's death had a reason. It was not random. It was not meaningless. It was the result of geological forces that could be studied and predicted and, one day, prevented.

But the man in front of me—the mathematician who had solved a three-hundred-year-old problem—was walking into that accelerator to learn a truth that he would not live to tell anyone about.

Was that rational? Was that meaningful? Or was it just another way of dying?

The line moved forward. I was next.

The technician at the entrance looked at me with tired eyes. "Are you sure?" he asked. This was a standard question. Everyone was asked. Everyone said yes.

"Yes," I said.

He nodded and opened the door.

Inside, the accelerator was a cylindrical chamber, maybe ten meters long and three meters in diameter. The walls were lined with sensors and cameras and recording equipment. In the center was a platform, and on the platform was a chair.

I sat in the chair. The sensors activated. The cameras began recording. The equipment started to hum.

And then I understood what was happening.

The accelerator was not going to reveal the truth to me. It was going to reveal the truth to the world—and I was going to be the medium through which the truth was revealed. The accelerator would use my consciousness as a conduit, broadcasting the truth across the entire scientific community in a single instant of pure understanding.

But the human mind was not designed to hold the truth. Not all of it. Not at once. The truth was too big, too complex, too overwhelming for a single human brain to contain. So when the truth flowed through me, my mind would burn out. I would die. But the truth would live.

I closed my eyes and thought about my father. I thought about the coal mine, the darkness, the collapse. I thought about the phrase he had lived by and died by.

The sky will not fall.

I opened my eyes and looked at the ceiling of the accelerator chamber. I thought about the universe, vast and indifferent and beautiful and terrible. I thought about the truth, waiting for me on the other side of the light.

And I smiled.

Because I finally understood. The truth was not something you learned. It was something you became. And becoming the truth was the most important thing a human being could do.

The accelerator activated.

The light was blinding. It filled the chamber, filled my body, filled my mind. I felt the truth flowing through me, vast and infinite and beautiful and terrible, and I knew, in that single instantaneous moment, everything.

Everything.

And then I was gone.

The accelerator stopped. The chamber was empty. The platform was empty. The chair was empty.

No one knew what the truth was. No one had seen it, heard it, felt it. I had been the conduit, and I was gone, and the truth had flowed through me and disappeared into the void, leaving no trace, no record, no evidence that it had ever existed.

I walked out of the laboratory and looked at the world. The sky was blue. The mountains were green. The wind was cold. The world was exactly as it had always been, and yet it was different, because I had seen the truth, and even though no one else had, even though the truth was gone, even though I was the only person in the world who had ever known it and I was now dead—

Even so, the sky had not fallen.

I stood in the wind and looked at the mountains and I thought about my father, and I smiled, and I walked away into the world that would never know what it had lost.