3. Earth, No Ordinary Rock (2)

☼ Exhibit #3: Earth, a Truly Privileged Planet

What is the likelihood of other habitable planets in the future to be discovered in our universe? Is there life on Mars? Facts of life are missing but popular science often assumes the presence of liquid water for a long enough time on any given planet is the most important criteria for life to exist. Recently NASA engineers were interviewed about the discovery by the 2004 Mars Landers.  They were excited at indications that liquid water might have been present.  This, they insisted, suggested discovery of facts on life on Mars was only a matter of time. However, water is only one of the many prerequisites (or factors) required for life to exist. There are many factor that influence the likelyhood of discovery of other habitable planets in the future.

Factors for Life on a Planet

Let’s look closer at some of these essentials:

·         Distance from the sun: Life will exist only where temperatures range between the freezing and boiling points of water. Earth’s temperature is determined by the distance to its heat (and light) source: the sun. Only planets in a consistently temperate region around a sun (star) where liquid water could exist on the surface for an extended time (this is called the Circumstellar Habitable Zone or CHZ) would be potential candidates for life. In our solar system earth is the only viable candidate. Venus, next closer to the sun is too close and thus too hot (about 475 degree Celsius); Mars is our closest outward neighbor and averages a surface temperature below zero degrees Celsius, the freezing point of water. With these temperatures none of our neighbors can reasonably support/sustain life.

·         The right sun: Not any sun will do. First of all only planets that orbit in a single star system would qualify; zero or two-plus star systems fail. Next, the star must be a specific mass. A star more massive than ours will burn too quickly and too erratically to sustain consistent temperatures. Smaller stars with more frequent and violent flares would require a planet to be so close that the distance would cause tidal effects and restrict proper rotation of the planet. And the star must also be the right age to be at a stable burning phase without devastating temperature variations.

·         The right planet: To sustain life, many factors have to be just right for the planet. These include the age of the planet (stability, surface temperature, rotating speed), mass of the planet (gravity), presence of vital elements such as carbon and water (human life requires the presence of 26 essential elements), atmosphere (of the right composition), magnetic field around the earth, volcanic activity, plate tectonics, axial tilt, rotation period, oceans to continent ratio, quantity of water, shape of the orbit, ozone levels in the atmosphere and atmospheric pressure.

·         Presence of a moon: Earth’s moon is relatively large. It causes lunar tides, it stabilizes the tilt of the earth’s axis, and it slows the earth’s rate of rotation. Without the right size moon, complex life forms are not possible.

·         Protection from comets and asteroids: A planet that supports life needs to be in a solar system with at least one much larger planet. In our solar system this planet is Jupiter, it is two and a half times more massive that all other planets combined. Jupiter’s gravity attracts and captures incoming comets and comet debris thus preventing numerous collisions that would be destructive to the earth.

·         Location in the galaxy: There is a so called Galactic Habitable Zone (GHZ) – the area in a galaxy where habitable places can be found. As we learn from studying the Milky Way, the GHZ is an extremely small section of a galaxy, since the inner (most heavily populated) regions are too dense with too many collisions and interference.  The limited number of planets in the outer regions do not provide enough heavy elements to form terrestrial planets like earth. Galaxies outside the Milky Way appear even less inviting to life as they are less luminous and therefore – in general – lack the heavier elements needed for planets and life.

·         Age of the universe: The concept of Cosmic Habitable Age (CHA) further limits possibilities of life other than on earth. Only planets in galaxies formed at the right age of the universe will be worth considering. Life-essential elements heavier than helium weren’t present in the universe until they were made in the first stars and then ejected from their interiors; that excludes all the older galaxies. Galaxies/stars/planets formed in later ages of the universe not only have too many heavy elements, but also lack vital radioisotopes essential to support geological activities on these planets.

This list of factors is not complete but merely a subset of the currently identified requirements as mentioned in the following three books:

• The Creator and the Cosmos (1993) by Hugh Ross was one of the first publications to use scientific data to show the uniqueness of planet earth. Ross is an atheist-turned-Christian as a result of his research.
• Rare Earth (2000) by Peter Ward and Donald Brownlee. In Rare Earth the authors (both professors at the University of Washington in Seattle ) conclude from an evolutionary perspective, that, based on evidences from a wide range of disciplines, earth is a rare place indeed, and that complex life must be extraordinarily rare in the universe.
• The Privileged Planet (2004) by Guillermo Gonzalez and Jay Richards builds a strong case for a Creator based on the evidence from unique factors for earth as well as the unique location for observation of earth in the universe.

These factors show that earth is not just an ordinary rock, but that many things had to go “just right” when earth formed in terms of time, location and subsequent events. Earth is for sure considerably more “rare” and “privileged” than realized in the days of Carl Sagan.

Next: (3) Likelyhood of other Habitable Planets

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(1) Just an Ordinary Rock?	(2) Exhibit #3: Rare Earth
(3) Likelyhood of other Habitable Planets	(4) Exhibit #4: Designed for Discovery
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