We strolled along, talking idly, each of us periodically tilting his head backward for another look at the magnificent heavens. I don’t remember exactly what Cooper and I discussed during the first 15 minutes of our walk on the golf course. Probably we talked about school, girls, Cooper’s brothers, and the newest computer games -- all normal topics for our father/son conversations during that phase of his life.

The Life Cycle of Stars

Hubble Images Show Birth and Death in Stellar Nursery: Near thecenter of the nearly circular Triffid nebula, and partially hidden by a dark band of dust, is a large star, many times more massive than our sun. The star is the source of energy that fuels the nebula. It also heats the interstellar gas and dust that makes a nebula what it is -- a stellar womb.

The Eagle Nebula: The Hubble Space Telescope captured this image of the Eagle Nebula in 1995. Visit the telescope's website to learn and see more images.

At one point, near a tranquil pond sparkling with tiny, dancing lights that reflected the stars, Cooper and I stopped and spent about a minute identifying the Big Dipper and the north star, Polaris. I then launched into an unsolicited lecture on the historical significance of Polaris, forcing Cooper to listen to my long-winded explanation of the vital role played by the north star in the voyages of discovery and exploration in the 15th and 16th centuries.

Cooper eventually became slightly bored and, toward the end of my monologue, quietly wandered several yards away. He climbed a small knoll and was standing on its top with his arms outstretched and his eyes on the night sky. "What are you doing?" I asked, walking in his direction.

Cooper turned toward me briefly and smiled. Then he stretched out his arms again and gazed upward at the heavens. "Why do I feel so peaceful and content," he said a few moments later, "out here looking at the stars?"

For once I did not answer quickly. At length, after several seconds enjoying the image of my teenage son temporarily absorbed in a quiet appreciation of the wonders of the universe, I responded. "Because the stars are your parents," I said.

Cooper looked at me with a slightly furrowed brow. "You and Mom are my parents," he said, his declarative statement tinged with the suggestion of a question.

"In one sense," I said, "that’s correct. But the stars are your parents in another, more fundamental sense."

He glanced at me quizzically and slowly descended the knoll. "I don’t understand," he said.

"Do you remember learning," I said as Cooper walked over beside me, "in your biology class last year, about hemoglobin, the molecule in your blood that carries oxygen to the tissues?" He nodded. "Can you recall the atom at the center of the hemoglobin molecule?"

"Iron," he said emphatically.

"Good," I said. "And can you tell me where that iron atom comes from?"

Cooper flashed his best smart-aleck smile. "Sure," he said, "it comes from Geritol and spinach, among other places."

I laughed with him. "Okay," I said, "now tell me how it happens that iron is in Geritol and spinach."

He thought for a moment. "Iron is in the ground," Cooper said. "We make steel out of it, and I suppose somehow the roots of the spinach plant know how to pull it out of the soil." He shrugged. "And I guess the Geritol people simply include it in the chemicals when they’re mixing up their stuff."

"That’ll do," I said, as we started walking again. "And now for a tougher question. Do you know how it happens that iron is in the ground in the first place?"

Cooper was silent for several seconds. Then he shook his head. "No, I don’t," he said, turning toward me with a cocky grin. "But I bet you’re going to tell me," he added, "and I bet it has something to do with the stars being my parents."

We laughed again together and I put my arm around him. "Once upon a time…" I started.

"Dad," Cooper said, interrupting me quickly with an entreating look in his eyes, "you know I love your stories, but if you don’t mind, can I please have the short version? I mean, I am sort of interested in how the stars are my parents, but you know, it’s a beautiful night and I don’t want to have to think too much."

Once upon a time, the universe, if it even existed, was empty. Then suddenly, in a moment, there was a cataclysmic explosion of mammoth proportions. Following this Big Bang, which took place about 12 billion years ago, there was matter in the universe. But that primordial matter bore only a faint resemblance to the complex matter that now makes up the planet Earth. That earliest matter was mostly the simplest of all atoms, hydrogen and helium, with just a trace of lithium, the other chemical element at the bottom of the periodic chart.

The early matter of the universe was not uniformly distributed throughout space. As a result, after millions of years, gravity caused the formation of uneven clumps in the matter. These clumps eventually evolved to become galaxies, within which even denser concentrations of hydrogen and helium coalesced into large bodies. Some of these large bodies became dense enough that, at their cores, nuclear reactions converting hydrogen into helium started taking place. The reactions released energy in the form of heat and light. These bodies were called stars.

When these earliest stars formed in the universe, the Earth, the sun, and even the Milky Way Galaxy did not yet exist. It would be another few billion years before our galaxy would begin to take shape. And several billion years more were to pass before the great nebula of gas and dust that would become the sun and our solar system would form in one of the outer spiral arms of the Milky Way.

Stars, like human beings and all the plants and animals of the Earth, have life cycles. For most stars, the time between their birth and their death is measured in billions of years. Ordinarily, throughout most of its life, a star transforms hydrogen into helium as the result of a simple nuclear reaction. This process, in which the nuclei of different hydrogen atoms interact and bind, is called fusion. Helium atoms are the products of the interaction, with the released heat and light energy as a by-product. During its death throes, however, when the temperature and pressure at its center rise markedly, a star becomes a veritable chemical factory. In this extreme environment, some helium nuclei are able to undergo fusion, creating higher-order elements in the periodic chart, such as carbon, in the process.

There was no iron in the first billion years of the universe. There was not even any carbon until the first group of stars had completed their life cycles. Neither human beings nor any of the other complex forms of life that exist on Earth today could have been assembled at that time. Their raw materials had not yet been made.

Some large stars, when they die, explode in a gigantic paroxysm of heat and light called a supernova, sending the individual atoms created by the dying star racing outward through the universe at fantastic speeds. These cosmic rays eventually become part of another nebula of dust and particles in which clumps again aggregate and then form into new galaxies and stars. Near the end of these stellar life cycles, the fusion process continues its inexorable creation of higher-order chemical elements. If the temperature and pressure during the death of the new stars are sufficiently extreme, then such elements as silicon and nickel (a radioactive product that decays into iron) may be created.

"Most likely," I said to my silent son as we stood together on the golf course in the dark, "it took two or more generations of stars, and at least five billion years, to create the iron and other higher-order elements that are part of your body. Iron atoms, forged in dying stars and blasted across space following supernova explosions, were present in the nebula out of which the sun, the Earth and the rest of the solar system formed a mere 4 and a half billion years ago. If there had been no iron in our nebula, then evolution would never have had a chance to discover that hemoglobin was an efficient molecule to carry oxygen to the tissues. No iron, no hemoglobin. No hemoglobin, no human beings as we know them. In that case, needless to say, you and I would not exist."

Cooper smiled wanly at me. I pointed up at Sirius, the brightest star above our heads. "We are chemicals made in dying stars," I said. "That’s why I told you that the stars are your parents."

My son looked briefly at Sirius and then at me. He shook his head. Cooper had obviously had enough. "Dad," he said, starting to walk back toward the house, "you’re something else."

I took his hand and we walked along in silence. I knew better than to say anything more. But my mind continued the conversation unabated.

Yes, yes, my son, I thought, we humans are basically just chemicals produced in stellar factories over billions of years, chemicals now risen to consciousness, magically assembled through the miracle of evolution, somehow able to ponder our origin and our destiny, somehow able to discover that once upon a time stars lived and died and created the very elements out of which our bodies are made. I glanced around me as we walked. And not just us, Cooper, my mind continued, but everything around us, the grass, the trees, that squirrel scurrying through the leaves over there, all of them too had their atoms created in stars like those over our heads tonight. Everything we know and love owes its existence to the stars. Everything we love…

My stream of consciousness abruptly stopped. I looked again at my son walking beside me. Suddenly tears suffused my eyes and a powerful mixture of joy and happiness swept over me. In that brief, epiphanic moment a montage of images from Cooper’s life streamed through my mind. I saw Cooper lying in the hospital nursery a few minutes after his birth, feeding bread to the seagulls on the beach in Florida as a toddler, swimming underwater in the pool behind our home at the age of four, screaming with excitement when we were promoted to Sergeant in that old Apple II version of Castle Wolfenstein three years later and bounding into the air with uninhibited delight as a young teenager when his nine-iron shot from seventy yards away disappeared into the hole.

I stopped and gave Cooper a passionate bear hug. I held him close to me, my head thrown back, and gazed at the magnificent stars above my head. Through my tears I imagined I was watching the manufacturing of the very atoms that would someday become my son and me. Cooper and I began up there somewhere, I said to myself, eons and eons ago. And through a sequence of profound and wonderful miracles, we have arrived here together, parent and child, both of us children of an elaborate process extending over billions of years.

The combination of love and awe that I was feeling was overwhelming. I pulled slightly away from Cooper and our eyes met. "The stars are our parents," I said, my voice breaking, "but I am and will always be your only father."