Is Earth a Privileged Planet?
In November, 1990, space exploration succeeded in nearly reaching the edge of our solar system. From about 4 billion miles away the camera looked back to spot a pale blue speck in a vast sea of asteroids, planets and stars. That spot had been the launching place – Earth. It evoked a resurgence of philosophical questions. Was there any meaning or purpose attached to the existence of our planet? It seemed like such an insignificant, tiny speck. How could it be considered special?
After centuries of geocentric thinking, where everything revolved around the earth including the sun, Copernicus, in the 1500’s, presented evidence for a heliocentric existence. We, and the rest of the planets, move around the sun! Astronomer E. Hubble, 1921-26, at the Mt. Wilson Observatory, fueled the expectation of life existing elsewhere in the universe since there were so many stars and planets. Scientists like Carl Sagan pounced on this fact as showing that earth is not special. It is a mediocre planet existing alongside many other planets and likely billions more in the vast universe beyond our galaxy. There is bound to be life elsewhere – extra-terrestrial life. He said it’s delusional to think that Earth is a privileged planet.
Astro-biologist G. Gonzalez was also convinced of this in the 60’s and 70’s, was inspired to search space for Extra Terrestrial Intelligence and pursued this diligently. He was up against the probability of random trials producing a life supporting planet plus the knowledge that a number of essential factors would have to all exist in the same place at the same time to support complex life.
Given that all the laws of physics, biology, chemistry and mathematics are the same throughout the universe there would be about 20 essential factors that needed to all be present at the same time for complex life to be sustained. Some of them are listed below.
Liquid water – its qualities and nutrient absorbing abilities are absolutely essential but not sufficient alone. The recipe for life is not ‘just add water’.
Location – it would have to be revolving around the right sized star.
Distance – it would have to be just the right distance away from this star.
Atmosphere – the right mixture of gases must be present.
Crust – the composition of the crust would have to support plant growth, the water cycle and the carbon dioxide/oxygen cycle.
Plate tectonics – the movement of these huge plates in the crust allow for recycling carbon in the earth and shaping continents.
Ratio – the ratio of surface water to land needs to be just right.
Magnetic field – liquid iron at the core creates the magnetic field crucial to fending off harmful rays and providing compass direction.
Moon – just the right size and distance away to stabilize the tilt of the axis and control tides.
The electromagnetic spectrum (EMS) spans a range from huge radio waves to the very minute gamma rays. Visible light occupies just a tiny fraction of EMS but it is what allows for sight, photosynthesis in plants and other essentials. It has to be just right. 11.
The rotation of the earth must be stable and just the right speed to produce day and night, so essential for life forms. Too fast or too slow would have disastrous results.
The axis of earth tilted at 23 ½ degrees is just right to produce seasons.
These are not all the factors. If we then apply the probability function, we get a picture of how infinitely small the potential is for life to exist anywhere. Even at a generous allotment of 1 in 10 for each factor to happen by chance, the exponential nature of probability produces 1/10 x 1/10 … twenty times!! The probability approaches zero.
WE ARE LIVING ON A SPECIAL PLANET FOR A SPECIAL PURPOSE!