Despite my "retirement" from the Perkins Observatory, I still do a lot of public programs. During this phase of my astronomical life, I am now free to engage in the activity I've always loved the best – using telescopes of the big and the small to show people what their universe looks like.
During my long career as a star, people have asked me thousands of questions as they move at night, but one of them is still the most common, especially in the hours after midnight. "Do you believe there is another life in the universe," ask people. Alternatively, they ask, "Do you believe in UFOs?"
Questions complicate my natural skepticism. As for the physical universe, I do not believe in anything. I often answer: "Believe in your God, believe in your family, believe in your own country, if you want, trust in the basic goodness of mankind, I know that I am doing, look for evidence for all other affirmations."
Despite the other contradictory claims, the only life for which we have solid evidence is the life we find on our planet. We use the knowledge we have about him to speculate about the possibility of life in other worlds and what might look like.
Such assumptions are, of course, so specious to begin with. "Life" is difficult to define and may exist in radically different biochemical forms in other worlds.
However, we have to go with what we know, so we try to determine the circumstances that produced life on Earth and then extrapolate them to the possibility of life on other planets.
There are many complex demands to produce life on planet Earth. The Inevitable Conclusion: We are happy (or blessed, depending on your religious view) that all these circumstances have gathered here.
The requirement astrobiologists most often emphasize is the need for a mild, universal solvent so that the elements of the living being interact with each other. Fortunately, such a solvent exists in relative abundance in the universe. It's called water.
Unfortunately, most of the universe is too cold to produce a lot of water in the required liquid form. Places where they can be very special.
That's what astronomers talk about when they relate to the Goldilocks zone. Each star produces a different amount of energy. As a result, the planets are heated in varying degrees.
Therefore, each star has a unique band around where water can remain fluid most of the time. The band around the Earth's Sun stretches from Planet Venus from the inside to Mars planet outside. Both are barely in the zone. The earth is firmly connected within it. Happy!
Of course, the star energy must remain stable over a very long time, so the zone does not change. Many "variable stars", as they call it, change wild energy. Our second part is that the sun's energy is only slightly variable and it has been so long since.
We are happy that Earth's orbit is practically a circle, a situation that has remained unchanged for billions of years. Many planets circling around other stars show signs that their orbits have been extensively moved due to close gravitational encounters with other planets.
If the planet was close enough to Earth, its gravitational influence could take us out of the Goldilocks zone in its entirety. The stray mountain could also provide our almost circular orbit to the ellipse. As a result, the Earth will travel and exit from the Goldilocks Zone, and water could not remain liquid long enough to ease the long life-creating process.
Influence with another large body like a planet could have the same effect, and Earth had at least one of them. Fortunately, almost strange, such an effect has actually helped to create life on Earth.
The country is leaning 23 degrees toward orbit around the sun. Some kind of cataclysmic event like giant influence had to cause our tune.
Our seasonal shifts, from summer to winter and back, are the result of this incline. Seasons allow water to be fluid at some time or in the other part of a larger part of the planet. Planets with no gradients must have a very narrow zone where water is possible, even if they are in the Goldilocks zone.
And we are fortunate for another truly cataclysmic influence. Early in Earth's formation, before life was possible on our planet, a Mars-sized object hit the Earth with enough strength to begin making ours significantly larger than the average month.
During tens of thousands of years, the Earth's slope ticks a little while traveling around the sun. It would be much more without stabilizing the influence of a large object circling around it.
Consequently, we have long had a relatively stable and predictable climate, a situation that certainly will not last forever, as we will see next week.
A stable climate means that water can remain liquid over most of our planet, but it obviously asks the question: "Where did all the water come from first place?"
The earth was created by the influence of smaller bodies called planetsimals, who were forced into a violent intersection due to their orbits and their intriguing gravitational attraction.
The result was a molten ball of rock, with a hot force of influence and made a ball at the gravity gravity to make things all over again in all directions equally.
These items safely contained frozen water, and water escaped from the rock in the form of gas. At some point, the Earth has become big enough to have enough gravity to support the atmosphere, and so part of the water did not escape the universe.
More and more, many astronomers are convinced that this process will not produce enough water to take account of the Earth's relative abundance. Something has to happen at the very end of the Earth's formation when it starts to cool off.
That something, and something good luck, was a late heavy bombing. LHB started about four billion years ago. As Earth hid around the sun, she cleansed her orbit of astonishing material.
To a great extent this cosmic detritus consisted of small objects now referred to as comets and asteroids. Comets are particularly rich in water. Our oceans, where life originated on Earth, are mostly caused by this happy late bombing of the comet.
LHB also added much nitrogen to the atmosphere and a little carbon dioxide. We mean carbon dioxide as a gas. Our CO2 came from a solid shape called dry ice, which comets also have in abundance.
Then there is a hot ball of fireplaces with a large amount of surface water and a rich chemical mixture in the atmosphere and the ocean. In this way the stage is set for life, but life has not yet been formed. To create life and to develop people, a separate set of happy events should appear. More about it next time.
Tom Burns is former director of the Perkins Observatory in Delaware.