There's No Place Like Earth!

by Anthony Nevard

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Speculation about life on other planets ignores this essential fact: only very special conditions make life possible on earth. These are not known to exist on any of the other eight planets in our solar system, nor anywhere else in the universe. Some scientists seem to imagine that, if a planetary system were discovered around a distant star, there would be one chance in nine that one of the planets would be just like the earth! Such an assertion ignores the many absolutely unique features of our planet.

The Earth’s Size

The diameter of the earth is 8,000 miles. If 10% smaller (7,200 miles), its lower mass would decrease gravity, allowing much of the atmosphere to escape. Temperatures would fall to below freezing point over most of the globe. However, an increase of 10% (8,800 miles) would double the weight of the atmosphere, increase the volume of water and probably flood the whole planet.

Orbit and Rotation

Our year of 365¼ days and the length of the seasons allow for crops to be grown and harvested. The 24-hour day allows adequate heating in the day and prevents excessive cooling at night. Compare this with a year on Mars, lasting 687 days, Saturn’s day of 10¼ hours and a rotation of Mercury taking 59 days!

Distance from the Sun

On average, earth is 93 million miles from the sun, producing an ideal range of temperatures for life. Venus, nearer the sun, has a surface temperature of 480°C, while Mars is at –23 °C. There is concern that a world-wide rise of two or three degrees (e.g. due to CO2 emissions and the greenhouse effect) could melt the polar ice caps and cause widespread flooding.

Atmosphere

Most of the other planets are covered by poisonous gases with very little oxygen. Our level of 21% is ideal: below 10%, fire would not burn and respiration would be difficult. A much greater level would encourage too rapid burning and oxidation processes. The ozone layer also shields life from harmful ultra-violet radiation from the sun. The atmosphere on Venus, for example, consists mostly of carbon dioxide and methane.

These unique features of our earth, on all of which depend the myriad of life forms on land and in the sea, can hardly be accidental: they betoken design by a loving Creator.

The Earth: Uniquely Created for Human Life

GRAVITY: Mass and density of Earth exactly suited to hold the atmosphere.

ROTATION: Cycle of day and night. Produces winds and ocean currents.

TILT: 23 degrees. Causes seasons by changing angle of sun.

THE MOON: Reflective surface to give light at night. Phases for 4-week cycle. Gravity causes tides. Exact size and distances from Earth and Sun to allow total solar eclipses.

MAGNETIC FIELD: Diverts solar radiation. Directional aid for animals and man.

THE SUN: A million times larger than Earth. 93 million miles away: we receive one two-billionth of its energy. Provides ideal light and temperature for life.

MINERAL RESOURCES: Soil contains elements needed for plants to grow. All natural elements found in sea water. Provides man with materials for building (stone, lime, clay), fuel (coal, oil, gas), artifacts (metals), adornment (precious stones).

AIR: 78% nitrogen; No poisonous gases. 21% oxygen - precisely suitable for life; 0.04% carbon dioxide - essential for plants. Ozone layer in upper atmosphere to protect life from harmful solar radiation. Ionosphere reflects radio waves. Water cycle - clouds to provide water inland. Winds to mix air, move clouds, disperse seeds, etc.

WATER: Liquid over wide temperature range. High boiling point. Dissolves most chemicals and gases e.g. oxygen. Expands when frozen and floats, so protects life. High surface tension and heat capacity. Supports bodies of animals.

Bibliography. Chapman, G. Our Unique Planet, CSM pamphlet 251, 1987.

First published in DAYLIGHT No. 29, Autumn/Winter 1999. © A. Nevard 2000.


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