The moon: the light that rules the night
Our Moon. God created it. Man reached it. Poets have written about it. Find out about some fascinating truths behind our great ‘lesser light’…
Posted on homepage: 29 June 2011 (GMT+10)
The moon—an object of wonder since the dawn of mankind. It lights up the night sky like nothing else in the heavens, and appears as if it regularly changes shape. As we shall see, it is well designed for life on Earth, while its origin baffles evolutionists.
The moon’s origin
Although there are many different ideas on how and when the moon formed, no scientist was there at the time. So we should rely on the witness of One who was there (cf. Job 38:4), and who has revealed the truth in Genesis 1:14–19:
And God said, “Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons, and for days and years, and let them be lights in the expanse of the heavens to give light upon the earth.” And it was so. And God made the two great lights—the greater light to rule the day and the lesser light to rule the night—and the stars. And God set them in the expanse of the heavens to give light on the earth, to rule over the day and over the night, and to separate the light from the darkness. And God saw that it was good. And there was evening and there was morning, the fourth day.
This passage clearly states that God made the moon on the same day as the sun and stars—the fourth day of Creation Week. It was also created one day after the plants. This order of events is impossible to reconcile with evolutionary/billions of years ideas.
The moon’s purpose
The answer’s in Genesis! A major purpose is to light up the night. The moon reflects the sun’s light on to us even when the sun is on the other side of the earth. The amount of reflected light depends on the moon’s surface area, so we are fortunate to have a moon that is so large. It is over a quarter of Earth’s diameter—far larger in comparison with its planet than any other in the solar system.1 Also, if it were much smaller, it would not have enough gravity to maintain its spherical shape.2
Another reason for the moon is to show the seasons. The moon orbits the earth roughly once a month causing regular phases in a 29½ day cycle (see diagram right). So calendars could be made, so people could plant their crops at the best time of the year.
An important feature is that the moon always keeps the same face towards the earth.3 If different parts were visible at different times, the moon’s brightness would depend on which part was pointing towards the earth. Then the 29½ day cycle would be far less obvious.
The moon’s size and closeness to Earth means it has the greatest tidal effect on Earth. Even the sun has less than half this effect, and the effect of the other planets is negligible.1 When the sun and moon are aligned, their combined gravity results in strong spring tides. When they are at right angles, their gravity partly cancels, resulting in weak neap tides.
- Gravitational force between two objects is given by F = Gm1m2/R2, where G is the gravitational constant, m1 and m2 are the masses of the objects, and R is the distance between their centres of mass—an inverse square law. But the tidal effect drops off far more quickly, with R3—an inverse cube law. If more people had known this, they wouldn’t have been scared by knowing all the planets would be roughly aligned in 1982, when many predicted this would lead to disaster.
The earth’s gravity keeps the moon in orbit, and is so strong that it would need a steel cable 850 km (531 miles) in diameter to provide an equivalent binding force without breaking. The moon exerts the same force on the earth. But the force is somewhat higher on the part of the earth nearest the moon, so any water there will bulge towards it—a high tide. The part furthest from the moon is attracted the least by the moon, so flows away from the moon (and Earth’s centre)—another high tide on the opposite side of the earth. In between, the water level must drop—the low tides—see diagram. As the moon orbits the spinning earth, there is a cycle of two high tides and two low tides about every 25 hours.
Tides are vital to life on Earth. Tides cleanse the ocean’s shorelines, and help keep the ocean currents circulating, preventing the ocean from stagnating. They benefit man by scouring out shipping channels and diluting sewage discharges. In some places, people exploit the enormous energy of the tides to generate electricity.4
Nice to visit; but to live?
One of the most dramatic events of our time was the landing of men on the moon. However, they confirmed that it is a lifeless, airless world, with huge temperature extremes and no liquid water. From the moon, Earth appears as a bright blue-and-white object in the black sky. Earth is the planet God has designed for life. Man may be able to live on other worlds one day, but it will be hard to make them habitable.
Many people don’t realise that the man behind the Apollo moon mission was the creationist rocket scientist Wernher von Braun.5 And another creationist, Jules Poirier, designed some vital navigational equipment used in the space program.6
How long has the moon been receding?
Friction by the tides is slowing the earth’s rotation, so the length of a day is increasing by 0.002 seconds per century. This means that the earth is losing angular momentum.7 The Law of Conservation of Angular Momentum says that the angular momentum the earth loses must be gained by the moon. Thus the moon is slowly receding from Earth at about 4 cm (1½ inches) per year, and the rate would have been greater in the past. The moon could never have been closer than 18,400 km (11,500 miles), known as the Roche Limit, because Earth’s tidal forces (i.e., the result of different gravitational forces on different parts of the moon) would have shattered it. But even if the moon had started receding from being in contact with the earth, it would have taken only 1.37 billion years to reach its present distance.8 NB: this is the maximum possible age—far too young for evolution (and much younger than the radiometric ‘dates’ assigned to moon rocks)—not the actual age.
|Mean distance from earth||384,404 km or 239,000 miles|
|Diameter||3,476 km or 2172.5 miles (0.273 Earth, 1/400 Sun)|
|Mass||7.35 x 1022 kg (0.0123 Earth)|
|Density||3.34 g/cm3 (0.6 Earth)|
|Surface Temperature||204°C (400°F) day, -205° C (-338°F)|
|True (sidereal) orbital period||27.322 Earth days (29.531 day phase cycle)14|
|Orbital angular momentum||2.68 x 1034 kg m2/s (82.9% of earth-moon system)|
|Inclination of equator to orbital plane||6° 41′ (cf. Earth 23° 27′)|
|Earth-moon gravitational attraction||1.98 x 1020 N (2.23 x 1016 tons)|
Could the moon form by itself?
Evolutionists (and progressive creationists) deny the moon’s direct creation by God. They have come up with several theories, but they all have serious holes, as many evolutionists themselves admit. For example, lunar researcher S. Ross Taylor said: ‘The best models of lunar origin are the testable ones, but the testable models for lunar origin are wrong.’9 Another astronomer said, half-jokingly, that there were no good (naturalistic) explanations, so the best explanation is that the moon is an illusion!10
Fission theory, invented by the astronomer George Darwin (son of Charles). He proposed that the earth spun so fast that a chunk broke off. But this theory is universally discarded today. The earth could never have spun fast enough to throw a moon into orbit, and the escaping moon would have been shattered while within the Roche Limit.
Capture theory—the moon was wandering through the solar system, and was captured by Earth’s gravity. But the chance of two bodies passing close enough is minute; the moon would be more likely to have been ‘slingshotted’ like artificial satellites than captured. Finally, even a successful capture would have resulted in an elongated comet-like orbit.
Condensation theory—the moon grew out of a dust cloud attracted by Earth’s gravity. However, no such cloud could be dense enough, and it doesn’t account for the moon’s low iron content.
Impact theory— the currently fashionable idea that material was blasted off from Earth by the impact of another object. Calculations show that to get enough material to form the moon, the impacting object would need to have been twice as massive as Mars. Then there is the unsolved problem of losing the excess angular momentum.11
When day becomes night …
One of the most fascinating sights in the sky is a total eclipse of the sun. This is possible because the moon is almost exactly the same angular size (half a degree) in the sky as the sun—it is both 400 times smaller and 400 times closer than the sun. This looks like design. If the moon had really been receding for billions of years, and man had been around for a tiny fraction of that time, the chances of mankind living at a time so he could observe this precise size matchup would be remote.12
The moon is a good example of the heavens declaring God’s glory (Psalm 19:1). It does what it’s designed to do, and is vital for life on Earth. It is also a headache for evolutionists/uniformitarians.
References and notes
- Apart from the remote Pluto/Charon system. Return to text.
- The most stable shape for a massive body is for all parts of the surface to be the same distance from the centre of mass, i.e. a sphere. The pressure inside the moon is ten times the crushing strength of granite, so any large unevenness would be crushed into shape. Such a sphere may bulge at the equator if the body is spinning fast enough. Return to text.
- That is, its rotational period is identical to its (synodic) orbital period. This is true of many moons in the solar system, because the planet’s gravity is always stronger on the nearest side (a tidal interaction), and this will eventually lock one side so it will always face the planet. The effect is enhanced if one side is denser than the other. Return to text.
- Fred Pearce, ‘Catching the tide’, New Scientist 158(2139):38–41, June 20, 1998. Return to text.
- See Ann Lamont, 21 Great Scientists who Believed the Bible, Creation Science Foundation, Australia, 1995, pp. 242–251. Return to text.
- For more details, see his article ‘The magnificent migrating monarch’, Creation 20(1):28–31, 1997. Return to text.
- Angular momentum = mvr, the product of mass, velocity and distance, and is always conserved (constant) in an isolated system. Return to text.
- For the technical reader: since tidal forces are inversely proportional to the cube of the distance, the recession rate (dR/dt) is inversely proportional to the sixth power of the distance. So dR/dt = k/R6, where k is a constant = (present speed: 0.04 m/year) x (present distance: 384,400,000 m)6 = 1.29x1050 m7/year. Integrating this differential equation gives the time to move from Ri to Rf as t = 1/7k(Rf7 —Ri7). For Rf = the present distance and Ri = the Roche Limit, t = 1.37 x 109 years. There is no significant difference if Ri = 0, i.e. the earth and moon touching, because of the high recession rate (caused by enormous tides) if the moon is close. See also Don DeYoung, ‘The Earth-Moon System’, Proceedings of the Second International Conference on Creationism, Vol. II, pp. 79–84, 1990. Return to text.
- S. Ross Taylor, paraphrased by geophysicist Sean Solomon, at Kona, Hawaii, Conference on Lunar Origin, 1984; cited in: Hartmann, Wm. K., The History of Earth, p. 44, Workman Publishing Co., Inc., Broadway, NY, 1991. Return to text.
- Irwin Shapiro in a university astronomy class about 20 years ago, cited by Lissauer, J.J., It’s not easy to make the moon, Nature 389(6649):327–352, 25 Sep 1997 | doi:10.1038/38596 (comment on Ida et al.,, Ref. 11). Lissauer affirms that the first three theories have insoluble problems. Return to text.
- Shigeru Ida et al., ‘Lunar accretion from an impact generated disk’, Nature 389(6649):353–357, 25 Sep 1997 | doi:10.1038/3866. Return to text.
- See also D.R. Faulkner, ‘The angular size of the moon and other planetary satellites: An argument for Design’, Creation Research Society Quarterly 35(1):23–26, June 1998. Return to text.
- From John C. Whitcomb and Donald B. DeYoung, The Moon: Its Creation, Form and Significance, Baker Book House, Grand Rapids, Michigan, 1978. This book provided many ideas for this article. Return to text.
- The sidereal period is the time for a complete orbit of the moon around the earth, relative to an observer outside the solar system. The phase cycle (synodic period) is the time taken for the moon to return to the same orientation towards the sun. It is longer because the earth moves about 1/13th of the way in its orbit around the sun, so the moon must travel further than one true lunar orbit for a given orientation to recur. (The assistance of astronomer Dr Danny Faulkner is gratefully acknowledged). Return to text.