The earth is teeming with life. Because it’s all around us, displayed in a variety of plants, insects and animals, we may take the existence of life for granted. But have you stopped to consider what it really takes to support life on Earth? Two scientists did. Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist, wrote Rare Earth: Why Complex Life is Uncommon in the Universe. They explain why the factors required to support life on Earth are such a rare combination. Here are the factors that must exist simultaneously:
- A star within the right range of size and luminosity.
- A terrestrial (not gaseous) planet rich in atomic elements essential to life.
- A solar system with planets having circular (not elliptical) orbits.
- Large oceans with salinity and pH in the right ranges to support subsurface life, and to moderate temperature fluctuations.
- A large planet (Jupiter) to protect Earth from bombardment by comets and asteroids.
- An oxygen-enriched atmosphere.
- A distance from the sun that’s within the inhabitable zone where the planet doesn’t receive too much or too little radiation.
- Tectonic plates that form continents so that shallow areas of the oceans exist which absorb CO2 from the atmosphere and convert it to limestone.
- A planet that rotates on its axis so all surfaces have access to sunlight.
- A large moon to stabilize the Earth’s tilt and rotational speed, and to provide lunar tides in the oceans.
- Tucked away from astronomical threats such as gamma ray bombardment
Is it only chance that all these factors simultaneously exist and have been stable for a long time? You decide. As I contemplate this, I’m reminded of David’s thoughts captured in Psalm 8:1, 3-4:
O Lord, our Lord, how majestic is Your name in all the earth, who have displayed Your splendor above the heavens! When I consider Your heavens, the work of Your fingers, the moon and the stars, which you have ordained; what is man that You take thought of him, and the son of man that you care for him?