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Creation’s Story (12)

R W Cargill, St Monans

THE EARTH - A UNIQUE PLANET

The world we live in, this planet called Earth, is truly a unique place, an exceptional planet among all the others in the solar system, an exceptional world among all the uncountable worlds in space. It is exceptional and unique in at least two respects. The first and best of these is that the very Son of God came here, born in a lowly manger at Bethlehem, dying on a rugged cross at Calvary, to work out God’s great plan of salvation. He "came into the world to save sinners" (1 Tim 1.15), to provide eternal life. The second unique feature is how Earth alone provides a suitable environment to contain and support physical life.

Although many changes took place at and after the great Flood which we have been considering, these affected mainly its surface structure, its topography, geography and geology, rather than its fundamental properties designed by God. We have already seen that His creative acts in Genesis 1 were in an orderly sequence leading up to the point where man could take his place in an "up-and-running" world which he could enjoy and care for, which would supply all his requirements for food, home, peace and beauty. In spite of the entrance of sin into the world, the fact remains that those strict and stringent conditions for life are still found on earth, and nowhere else! Scripture teaches clearly that God designed the world to be inhabited by man (Is 45.18; Acts 17.26). We know also that the blessing of man was planned "before the foundation of the world" (Eph 1.4). Therefore God designed, founded and formed this unique planet with man in mind from the beginning.

Creation’s story is written throughout the whole universe, with more being revealed and in measure understood as time passes. But most clearly for us, and most relevant to us, is the part of this amazing story written in the structure and properties of our own planet Earth. All who have studied this fascinating subject have come to the conclusion that Earth is a truly unique place, exactly suited for life and for man. Many far fetched and fuzzy theories of how it came to be like this have been proposed. A series of accidents, a few coincidences, and a measure of "luck" (and I quote from a recent science-based book!) we are told were responsible! The idea of "intelligent design" is ferociously rejected although it is so evident from the largest to the smallest structure which is explored.

Conditions for Life

Life is very fragile, although we take it for granted. Its existence depends upon many physical conditions being just right, e.g. temperatures between about 0 and 40 degrees C, values of fundamental gravitational and nuclear forces being what they are. It also depends on certain chemicals being available, e.g. water and oxygen, and equally on others being absent or in very small amounts, e.g. cyanide and carbon monoxide. Likewise, there are forms of radiation which are absolutely essential to all life on earth, i.e. "visible" light and some infrared, but others are lethal, e.g. X rays and deep ultraviolet.

In the next few articles, we shall look at the unique way in which all these conditions come together in our planet, and nowhere else, and how God designed them into the fabric of the world we live in.

The Sun

The earth’s surface temperature is governed mainly by two things, the energy emission from the sun and the distance from the sun. If the sun were hotter, or if Earth were nearer it, all life would burn up. If it were cooler, or Earth farther away, all would freeze to death.

The sun is a star whose energy is generated from its interior where hydrogen atoms combine to form helium atoms at a temperature of around 15 million degrees C. Its surface temperature is about 5,500 degrees C. Stars vary in size from about one tenth to over one hundred times the size of the sun, and their surface temperatures vary between 3,000 and 40,000 degrees C (shown by their colours – red dwarfs up to blue-white giants). Among all these, the sun is a medium sized yellow star (diameter about 865,000 miles, 109 times the diameter of the earth, 745 times the mass of all the planets put together). At the correct distance of about 93 million miles from the sun, Earth receives the correct amount of radiation from this correct size of star to achieve the temperatures we can live with - all beautifully matched!

The Solar System

The sun provides the anchor point for the whole solar system of eight major planets moving round it in an anticlockwise direction, while they also spin on their own axes. There are four inner planets, Mercury to Mars, relatively small, dense and rocky; and four outer ones, Jupiter to Neptune, which are huge spheres of low density gaseous material. Planets closer to the sun are very much hotter, those farther away much cooler. Our distance from the efficient, clean, giant power generator called the sun is just right, and the energy comes free over the vast distance involved, in fact taking 8.3 minutes to reach us. "There is nothing hid from the heat thereof" (Ps 19.6); "He maketh his sun to rise on the evil and on the good" (Mt 5.45).

Planets nearer the sun orbit round it more quickly - a year on Mercury is about a quarter of our year (whilst its "day" lasts for 58 of our days). More distant planets orbit the sun more slowly - Neptune’s year is 165 of our years (its day is 16.1 hours). Among the planets, Earth occupies its God-given position between Venus and Mars, with even the length of the year and the length of the day suiting our life cycle.

Other factors help to maintain the temperatures we need. First, the period of 24 hours for the earth to spin on its axis is just about right. Longer periods would give time for extremely cold nights and extremely hot days to develop; shorter periods would destabilise weather patterns and cause the gases of the atmosphere to spin off into space. Also, because the earth’s axis is not at right angles to the sun’s rays but tilted by 23.5 degrees, the energy influx is spread over a wider area north and south of the equator. Seasons are thus extended, and the very hot and the very cold regions of the earth are minimised.

As the planets orbit the sun, they trace out an elliptical path. Some, like Mercury nearest the sun or Pluto farthest away, have very elongated ellipses. But the earth’s orbit is almost circular. If it too were elongated (more squashed), then for some months of the year the earth would be nearer the sun and get very much hotter, followed by very much colder months when it was further away. Such life threatening extremes do not occur because of the near circular shape of the earth’s orbit.

The Atmosphere

Yet another factor which has a major effect on temperature is the size and composition of the atmosphere – an insulating blanket which helps to retain the heat (greenhouse effect). Atmospheres on other planets are very different. Mercury’s is so thin that the temperature swings between - 170 and + 400 degrees C as heat is lost or gained easily. Venus’s is very thick, composed of carbon dioxide, with clouds made of 80% sulphuric acid. It retains so much heat that the temperature is 475 degrees C.

The composition of our atmosphere is governed by the gravitational pull of the earth, as is the mobility of everything on its surface. If, for example, gravity was much less, oxygen, nitrogen, and water vapour necessary for life would escape into space, only argon and carbon dioxide remaining. The shielding effect of the atmosphere would also be reduced, both for retaining heat and for preventing damage due to cosmic rays. On the other hand, if gravity was much greater, the air density and pressure would increase, and life forms of all types would require greater muscle and skeletal strength to move and survive.

Gravitational factors govern the pull of the earth on everything, especially the moon, our nearest celestial neighbour. Its pull in turn affects the ocean tides, the size of which are important, too much giving coastal instability, too little hindering recycling of nutrients and pollutants.

The balance of every factor responsible for Earth being a suitable home for man, and for countless other life forms, is truly a clear pointer to the wisdom and design of the Creator. We can say with conviction and with worship, "O Lord, how manifold are thy works! In wisdom hast thou made them all: the earth is full of thy riches. So is this great and wide sea …" (Ps 104.24-25).

To be continued.

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