The title of this post derives from the 1956 novel by Arthur C. Clarke "The City and the Stars" which starts with the description of the ancient city of Diaspar - one billion years in our future. Just as the protagonist of the novel breaks one barrier after the other in his quest for truth, so we are breaking one scientific barrier after another in a series of scientific revolutions. A recent one has started with the discovery of a large number of extra-solar planets coupled with the new understanding we have of the mechanisms that keeps our Earth "alive".
If I go back to my teenage years, I can identify some of the reasons that led me to follow a scientific career. One is a novel by Arthur C. Clarke: "The City and the Stars," published in 1956 and that I read when I was, maybe, 15 years old. The name of the city of the novel "Diaspar" has remained riveted in my mind ever since.
"The city and the stars" is "hard" science fiction; it deals with planets, stars and spaceships. You can read it as an adventure novel, but also as an allegory of the human search for truth and enlightenment. It starts with the protagonist locked inside the walls of Diaspar. A jewel of a city of a billion years in our future, but also a small world from which the protagonist tries to escape. And he succeeds; breaking one wall after another, exploring what is left of the ancient planet Earth, and then moving to space to find all sorts of wonders. The novel leaves you breathless with its width and depth. It is pure magic: the magic of scientific discovery.
It is said that science is 1% inspiration and 99% perspiration. I can confirm from my experience that it is true. Of course, science fiction makes things easier: it removes the 99% of perspiration. But even in real science, the 1% of inspiration is well worth the 99% of hard work. Good science brings to you the same sensation of wonder that good science fiction produces - the sensation of breaking down one knowledge barrier after another, with the advantage that it is for real!
So, during the past few years, we have had so much good science that it has been almost overwhelming to keep track of it. Every morning, I give a look to the web to see what is new in science and, almost every morning, I am struck by something new and unexpected to be read and understood. It is hard to absorb so much, but I try and it is always fascinating.
The latest scientific revolution is in planetary science. It seems almost unbelievable that just some decades ago people were still debating on whether extrasolar planets actually existed. Today, we are discovering so many of them that it is now believed that almost every star in the galaxy has planets. It all reminds us of the times of Galileo Galilei. Think about that: before Galileo, planets were just specks of light fixed to crystal spheres. Then, after Galileo looked at the night sky with his telescope, - bang! - planet became big balls floating in space. And and not just that: there were small planets orbiting big planets; miniature solar systems. A sudden expansion of the horizon - the breakdown of a knowledge barrier. From Galileo to us, it has been breaking one wall after another: science is enlarging our horizons at a breathless pace. The universe keeps becoming bigger. Now, everytime you raise your eyes to look at the Milky Way, you know that you are looking at a galaxy full of planets. (image below from ESO, showing a comparison of the planets of the Solar System and those of Gliese 581, a star located at about 20 light years away from the Sun. )
But the thrill of new discoveries doesn't just come from knowing that extrasolar planets exist. It comes also from what we know about these planets. A revolution in planetary sciences has been going on at a breathless pace. It is a synthesis that puts together geology, biology, astronomy and physics to give us a picture of the life and the evolution of planets. Life on an Earth-like planet is not just a question of being at the right distance from a star. It is a delicate balance of factors that involve plate tectonics, the core temperature, the carbon cycle, solar irradiation; all interacting with each other to keep a planet "alive". The right combination of these factors can make a planet suitable for organic life and, probably, for the development of intelligent life. So, looking at the sky at night, we what we are seeing is not just a galaxy full planets, but also full of life and - probably - of intelligent life.
At the same time, the new science of planetary systems gives us a pretty clear view of how we can destroy our civilization by upsetting the delicate balance of the factors that keep our planet alive and friendly to us. We can do it in more than one way, but the most effective one is to continue to emit greenhouse gases in the atmosphere. So, once you have looked at the stars, come back to Earth and start doing something because we are all in trouble. If we manage to destroy ourselves it will little consolation to know that others in the Galaxy may do better than us.
About extrasolar planets, you may look at "Centauri Dreams" for updates.
A good synthesis of the interlocking factors that keep planets alive can be found in an article by Milan Cerkovic.
A previous post of mine on galactic civilizations is "The Hubbert hurdle: revisiting the Fermi paradox"