Throughout most of history, people thought that the sky did not change and life was always the same.
Peter Backus, SETI Institute (Translation: Dikala Oren)
Throughout most of history, people thought that the sky did not change and life was always the same. Many believed that the earth is the center of the universe and that humans are superior to other creatures, and then, four hundred years ago, the Copernican revolution came. The earth was no longer at the center, people realized that its true place was among the planets in our solar system. About two hundred and fifty years later, another revolution took place, when Charles Darwin revealed the true relationship between humans and the other animals and plants on Earth. These revolutions have a common denominator: they changed our perception and perspective and contributed to our understanding of our origins and our future.
Now we know that everything is changing. In four and a half billion years, the Earth changed from a hot, dry, crater-scarred piece of rock to a temperate world, composed mostly of oceans and teeming with life. We also know that most of the life that was on Earth has been extinct for a long time. Life changes, new species are created and others disappear, and we see the logic of this thanks to Darwin and his theory of evolution. Additionally, a perspective on how things change over time is very helpful in astronomy.
When we look into the depths of space, beyond the earth, we observe history and see the universe and its contents changing over time. 13.7 billion years ago, if there were stars, planets or life of any kind in the universe. At that time the universe was simpler, it consisted of only hydrogen and helium. Slowly, clouds of these two gases collapsed and formed stars, and the universe began to evolve. You must understand that stars are thermonuclear factories, creating larger atoms from smaller atoms. In the main process, hydrogen turns into helium, and in the process energy is released, which prevents the star from collapsing under its own gravity. Heavier stars are able to form larger atoms such as carbon, nitrogen and oxygen. In the end, the material for the star's nuclear furnace runs out and it is "dying". In this process, the star throws, sometimes in a spectacular explosion, a small part of its mass into space. The material released at the time of a star's death is different from the material that builds it at its birth. The material ejected at the death of a star is richer in heavy elements.
With the formation of a new generation of stars, formed from the remnants of the previous generation, the universe begins to change. Rocky planets form. Simple molecules such as water form and begin to collect on the surface of these planets. The earth was created after eight billion years and after the death of countless stars. A new chemistry has begun to form on our rocky, young planet. Scientists argue among themselves about the beginning of life on Earth. The exact mechanism and location of the "cradle of life" on Earth is shrouded in mystery. We do know, however, that the process began with the formation of the universe itself and proceeded through the hot cores of giant stars.
As Carl Sagan said, we are made of "stellar stuff". We are one of the results of the process of cosmic evolution. There is nothing special on earth. Our current understanding of the processes driving astronomical and biological evolution gives SETI astronomers much reason for optimism. If intelligence has evolved here, it can evolve elsewhere, and the technology to discover it is within our grasp, if our friends utilize the electromagnetic spectrum to communicate with us as we do.
As I spend Darwin's 195th birthday at the Arecibo Observatory, I find myself pondering such things as spider webs, nebulae, and the very process of contemplation. From all of us, who carry the journeys of human exploration into the universe, happy birthday, Charles!
