They became upright and taught themselves the use of tools, domesticated other animals, plants and fire, and devised language. The ash of stellar alchemy was now emerging into consciousness. At an ever-accelerating pace, it invented writing, cities, art and science, and sent spaceships to the planets and the stars. These are some of the things that hydrogen atoms do, given fifteen billion years of cosmic evolution.

Hydrogen is a light, odorless gas, which, given enough time, turns into people.

The hydrogen atoms in a human body completely refresh every seven years. As we age we are really a river of cosmically old atoms. The carbons in our bodies were produced in the dust of a star. The bulk of matter in our hands, skin, eyes, and hearts was made near the beginning of time, billions of years ago. We are much older than we look.

Those are some of the things that molecules do, given four billion years of evolution

Some scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that is the basic building block of the universe.

We on Earth have just awakened to the great oceans of space and time from which we have emerged. We are the legacy of 15 billion years of cosmic evolution. We have a choice: We can enhance life and come to know the universe that made us, or we can squander our 15 billion-year heritage in meaningless self-destruction. What happens in the first second of the next cosmic year depends on what we do, here and now, with our intelligence and our knowledge of the cosmos.

Our planet... consists largely of lumps of fall-out from a star-sized hydrogen bomb...Within our bodies, no less than three million atoms rendered unstable in that event still erupt every minute, releasing a tiny fraction of the energy stored from that fierce fire of long ago.

There is a further advantage [to hydrogen bombs]: the supply of uranium in the planet is very limited, and it might be feared that it would be used up before the human race was exterminated, but now that the practically unlimited supply of hydrogen can be utilized, there is considerable reason to hope that homo sapiens may put an end to himself, to the great advantage of such less ferocious animals as may survive. But it is time to return to less cheerful topics.

Every atom in me has a long history during which it may have been part of many living things, including human beings, and during which it may also have spent long periods as part of the sea, or in a lump of coal, or in a rock, or as a portion of the wind blowing upon us.

This is the greatest discovery of the scientific enterprise: You take hydrogen gas, and you leave it alone, and it turns into rosebushes, giraffes, and humans.

measurements, so please let me take a few minutes to summarize 13.8 billion years of cosmic history.

We were able to discover two new kinds of atomic species, one was hydrogen of mass 3, unknown until that time, and the other helium of mass 3, also unknown. … We were able to show that heavy hydrogen nuclei, that is to say the cores of heavy hydrogen atoms, could be made to react with one another to produce a good deal of energy and new kinds of atom. …Of course, we had no idea whatever that this would one day be applied to make hydrogen bombs. Our curiosity was just curiosity about the structure of the nucleus of the atom, and the discovery of these reactions was purely, as the Americans would put it, coincidental.

Apart from the question of food, there is the question of energy. It seems clear that, if it were financially worth while, fairly economical methods could be discovered by which more use would be made than at present of energy from the sun. And in theory there is no calculable limit to what can be got out of atomic energy. When people have discovered how to turn hydrogen into helium, sea-water will become their raw material, and it will be a long time before this source of supply is exhausted. Speaking of less specific possibilities, we have to reflect that man has existed for about a million years, and scientific technique for at most two hundred years. Seeing what it has already accomplished, it would be very rash to place any limits upon what it may accomplish in the future. Scientific knowledge is an intoxicating draught, and it may be one which the human race is unable to sustain. It may be that, like the men who built the Tower of Babel in the hope of reaching up to heaven, so the men who pursue the secrets of the atom will be punished for their impiety by providing by accident the means of exterminating the human species, and perhaps all life on this planet. From some points of view such a consummation might not be wholly regrettable, but these points of view can hardly be ours. Perhaps somewhere else, in some distant nebula, some unimportant star has an unimportant planet on which there are rational beings. Perhaps in another million years their instruments will tell them of our fate, and lead them to agree on an agenda for a conference of foreign ministers. If so, man will not have lived in vain.

But the universe, all of it, almost everywhere, is 99 percent hydrogen and helium,* the two simplest elements. Helium, in fact, was detected on the Sun before it was found on the Earth — hence its name (from Helios, one of the Greek sun gods). Might the other chemical elements have somehow evolved from hydrogen and helium? To balance the electrical repulsion, pieces of nuclear matter would have to be brought very close together so that the short-range nuclear forces are engaged. This can happen only at very high temperatures where the particles are moving so fast that the repulsive force does not have time to act — temperatures of tens of millions of degrees. In nature, such high temperatures and attendant high pressures are common only in the insides of the stars.