The belief that intelligent life is abundant in the universe, popular not many years ago, is no longer held in such high regard. Some experts now think we may even be alone. And that we are incredibly lucky to be here. How did it happen?
The Big Bang
In the beginning ..... Any story of a genesis begins with these words, and in this case In the Beginning there was the Big Bang. We can argue whether this was really the beginning, but neither theory nor observation gets us any further, so let's start there.
From a tiny speck, the universe exploded about 13 or so billion years ago (what's a billion years among friends?), and expanded rapidly, and in fact is expanding, even faster, now.
Neutrons
After the Big Bang there was plasma -- a hot soup of neutrons, protons, electrons, and radiation. Fortunately, there are forces that make it easy and desirable for 2 protons and 2 neutrons to team up to make what is called an alpha particle, but is really just the nucleus of a helium atom. Whole atoms couldn't form in the very early universe because of the temperature and the radiation, but the alpha particles became abundant, along with protons, which are really hydrogen nuclei. How lucky! You see, the neutron is unstable if left by itself and disintegrates with a half-life of 10 minutes. All the neutrons would have been gone in a few days if half of them hadn't been bound up in alpha particles in the first 8 minutes after the Big Bang.
Atoms
About 400,000 years later, things had cooled down enough for atoms to form, eventually leading to a periodic table of elements. At this time the universe became transparent to radiation, and the cosmic background radiation, which tells us there was a Big Bang, was born.
Galaxies and Supernovae
By and by stars formed in such proliferation that galaxies ensued. Some stars were unstable and they exploded, forming the higher atomic number elements like carbon, oxygen and uranium.
Planets
Some stars were blessed with planets, and some of these planets are in the Habitable Zone -- just the right distance from the star so that water exists in all three states of matter: solid, liquid, and gas --most importantly liquid.
At least one of these habitable planets exists under conditions that have made it possible for advanced life forms to arise. It took several billion years for this to happen, and this required extreme stability in some of the parameters of this planet.
Jupiter
Jupiter may be the most important factor in the rise of man. The early solar system was a dangerous place, with comets and asteroids and all sorts of debris from the unruly proto-planetary system whizzing about. Giant Jupiter, in its orbit farther away from the sun than the earth, swept away much of this debris, and protected earth from constant bombardment. Still, a few large pieces of junk have gotten past Jupiter and struck the earth.
Rotation Rate and Eccentricity
The earth has a rather roundish orbit, and a rapid rotation rate. This combination allows the planet to have fairly stable temperatures over much of its surface.
Extinction
Many times during the history of earth, there have been massive extinction events -- where up to 90% of the species vanished. The last of these was 65 million years ago, when the dinosaurs disappeared, giving the primates an opportunity to thrive and evolve into Homo sapiens.
Big Bang; neutrons; atoms; galaxies; stars; planets; big brother Jupiter; Goldilocks temperature; orbital stability; extinctions; the dinosaurs; the oceans -- water. We sure are lucky.
Interesting Reading:
- Rare Earth: Why Complex Life is Uncommon in the Universe, by Peter D. Ward and Donald Brownlee, Copernicus Press, 2000
Jon Plotkin - The author was a math major at Cornell and has a master's degree in meteorology from MIT.
