This is the online edition of In the Beginning: Compelling Evidence for Creation and the Flood, 8th Edition (2008), by Dr. Walt Brown. It is designed to be read online.
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Did the Preflood Earth Have a 30-Day Lunar Month?
Then 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 for lights in the expanse of the heavens to give light on the earth”; and it was so. And God made the two great lights, the greater light [the Sun] to govern the day, and the lesser light [the Moon] to govern the night;
Genesis 1:14–16a
Genesis 7:11, 7:24, and 8:3–4 tell us that exactly 5 months elapsed during the first 150 days of the flood. Could the preflood Earth have had 30-day months? Page 150 and Endnote 22 on page 164 explain why the preflood Earth probably had a 360-day year. This would make 30-day lunar months an ideal way to divide a year. The changing phases of the Moon would clearly show each month’s progression to everyone on Earth.
The problem with this idea is that today the average time between successive full Moons is 29.531 days—not 30 days. If preflood months were 30 days long, but today are 29.531 days long, then the Moon’s orbit was probably “pulled” closer to Earth as a consequence of the flood. (Satellites travel faster the closer they are to the body they orbit. A satellite orbiting very close to Earth completes one orbit in about 90 minutes.)
The energy (E) of a body of mass m (such as the Moon) orbiting a much larger body of mass M (such as the Earth) is
where G is the gravitational constant and a is the semimajor axis of the orbiting body. The orbiting body’s period (P) is
Solving for E in terms of P gives
As explained on page 150, before the flood (bf), a day was probably 365.256/360 times longer than a day is after the flood (af). If the Moon had a 30-day period before the flood, it would have lost 2.0% of its orbital energy as a result of the flood.
The cratered Moon has been severely bombarded. [See Figure 143 on page 268 and Item 12 on page 283.] Did the debris (rocks, ice, and water molecules), launched into space during the flood, remove 2% of the Moon’s energy? While these particles would have a wide range of orbits, the greatest concentration of debris would initially travel near to and roughly parallel with Earth’s orbit. Half the time, the Moon would have traveled generally in the same direction as this dense debris, so collisions would have been few and of low velocity. During the other half of the Moon’s orbit, orbiting debris would have opposed the Moon’s motion; many high-velocity collisions would have removed energy from the Moon’s orbit.
The Moon would have been analogous to a massive truck that every 15 days traveled in the proper lane (with the flow of traffic). On alternate 15-day periods, this “truck” traveled in the wrong lane (facing oncoming traffic), experienced many collisions, and lost some of its energy.
Ice and water vapor hitting the Moon would contribute to a thin lunar atmosphere. That atmosphere, especially on the side of the Moon facing the Sun where temperatures reach 260°F, would steadily escape the Moon’s gravity. Escaping water molecules would then be available for additional collisions with the Moon on future orbits. Therefore, water particles in the inner solar system would have been used multiple times in removing energy from the Moon’s orbit. (Although a water particle’s mass was small, the water’s total mass and momentum were large.) Eventually, these particles would have been scattered, and most would have been absorbed by the Sun and planets.
The Apollo 17 crew discovered that the Moon has an extremely thin atmosphere, about 10-14 that of Earth. These gases come from several sources, but the relatively large amount of oxygen present probably comes from dissociated water vapor that collided with the Moon. Today’s lunar atmosphere may be a remnant of what existed on the Moon soon after the flood. Water recently discovered on the Moon falsifies theories on the Moon’s evolution, but is consistent with the hydroplate theory. [See Endnote 48f on page 85 and Endnote 17 on page 289.]
If the preflood Earth had a 30-day lunar month, as appears likely, people living then would have had a marvelous system for telling calendar time—one that was simple, free, visible to all, standardized worldwide, and fixed with respect to the seasons.
At the end of the creation week, “God saw all that He had made, and behold, it was very good.” (Genesis 1:31) Seldom are we able to understand how much better things were then. However, with regard to measuring time, we now can better imagine how “very good” things once were.