Page 16 - GALIET PHYSICS BLOSSOMS II+

Consider each of these possibilities, and explain in perhaps 100 words for each one, how you interpret it, and how likely you think it is. What is crucial here is not the opinion you have, but your reasons and arguments for justifying it!
(ii) Consider the following three assertions:
- there is life on at least one other planet within 1000 light years of the earth, that is in at least some respects similar to what we have on earth.
Earth-like life in another planet could exist if it formed and evolved under similar conditions as the earth was formed and evolved. Carbon and a liquid water environment are essential. If a planet begun in a similar gravitational nebular contraction environment forming a parent star, planetoids and planets in a solar system, and similar catastrophic events occurred (meteorites colliding with the planetoids to form planets, volcanoes erupting), and natural radioactivity and ultraviolet radiation occurred, all leading to a chemical evolution emanating gases from the planet’s interior through volcanoes and geysers to create at atmosphere rich in hydrogen, nitrogen and carbon compounds, and if the planet, having cooled, created ammonia, methane, carbon dioxide and water, and preserved the right, life-sustaining temperature, there could be life in it as we know it. If this planet rotated relatively fast around its sun-like parent star at a life-sustaining speed and distance from it to ensure that a liquid outer iron core could generate, through convection, an active magnetic field or magnetosphere to shield the planet for harmful solar radiation, it is possible for life to exist. This planet would also need to be large enough to preserve its liquid iron core. If it were a small planet, it would cool faster, and its liquid core dry out. And yes, plate tectonics, continents drifting and colliding, would also be important for it makes our world changing and dynamic.
- there is life on at least one other planet within 1000 light years of the earth, that is however totally different to what we have on earth - so different that we may not even recognize it as such.
There can be life in another extra-solar planet that is dissimilar from our own. It may have been formed in similar or dissimilar ways, but it may have evolved in such a way that all the conditions for life became adverse. Life can thrive in environments rich in sulfur, poor oxygen, and which are absolutely dark. Hydrothermal vents found in our hostile deep ocean floor is an example. In a dissimilar form of life, these living organisms can react to their adverse environment by healing themselves, and by nourishing and growing, reproducing and passing along some of their characteristics to offspring, able to change and adapt in ways that are foreign to us.
- all planets within this volume (containing several billion planets) are devoid of life.
This is challenging to defend given that if life depends on just a few basic molecules that contain all the genetic information to reproduce and survive, whose elements are more or less common to all the stars, and that if the laws of nature and science, as we know them, apply to the whole universe, then given sufficient time, life must have indeed originated in similar or differing ways elsewhere in the universe. Even if it could be proven that life on earth evolved randomly according to certain astronomical, chemical, geological and biological accidents that did not occur anywhere else, and that our evolution over millions of years came to be only by chance mutations in genetic structures, and that intelligence and language evolved by natural selection, these same sequence of random of events could also have occurred in a parallel universe somewhere. Moreover, it is questionable if molecules can arise by chance alone.
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