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Does the recession of the Moon prove a Young Earth?
See Also
Young Earth Evidence
How Old is the Earth?
Discussion Group Age of the Earth
Claim
"¼ 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 a position of contact with the earth, it would have taken only 1.37 billion years to reach its present distance."
See Answers in Genesis (AiG)
To get the 1.37 billion-year age claimed by AiG, the rate of recession would have to have been faster in the past. After all, using the current rate of recession as given by AiG:
Distance of the Moon from Earth = 239,000 miles = 15,143,040,000 inches
15,143,040,000 inches / 1.5 inches per year = 10 billion years
Not the 1.37 billion given by AIG, therefore, even the basic facts presented by AIG are wrong!!! Don't they even own a calculator?
Simple common sense tells us this assumption about an increased rate in the past should be verified before any age claims can be made. What does the evidence say? Has the recession of the Moon been greater in the past as claimed by AiG?
Current rate of recession:
The Apollo astronauts left mirrors on the Moon. These allow
the current rate of recession to be observed directly. Laser ranging
establishes the current rate of recession of the moon at 3.82±0.07
cm/year (approx. 1.5 inches/year).
Past rate of recession:
The recession of the Moon is caused by tidal friction. The larger
the tidal friction, the greater the rate of Moon recession. The
magnitude of tidal friction depends on a combination of the arrangement
of the continents and the distance between the Earth and Moon. You
can't simply pick one factor and ignore the others as AiG does.
"¼ 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." Answers in Genesis
The closer Moon of the past had a stronger effect on the tides and therefore added to the rate of recession, as cited by AiG. However, large differences in the heights of the tides around different configurations of land masses would lessen the friction and therefore tending to cause a slower rate of recession. The arrangement of the continents in the past would have caused a decrease in tidal friction. The question then is, what is the net result of these factors, some of which increase the recession, and some of which decrease the recession? Mathematical modeling has shown that the overall tidal friction would have been less in the past, therefore causing SLOWER (not greater) rate for the Moon's recession.
Also, the closer the Moon, the faster its orbit (according to Kepler's Laws). The faster its orbit, the lower the tidal frequency, therefore the lower the recession rate. At some point, the Moon's orbit would be in sync with the Earth's rotation. Then there would be no energy dissipation and no recession. This shows that the Moon's recession must have been slower in the past when the Moon was closer.
But these calculations could be wrong. Is there any physical evidence to support this conclusion?
The physical evidence of this slower rate comes in the form of tidal rhythmites (tidally laminated sediments). They record the velocity and range of the tides providing a method to measure tidal strengths of the past. They show that 650 million years ago, the rate of recession was about 2 cm/year, and that over the period from 2.5 billion to 650 million years ago, the mean recession rate was 1.27 cm/year.
Note: Basic Newtonian physics allows one to easily calculate the distance of the Moon based on lunar cycles. 650 million years ago, the distance of the Moon was still 96.9% of its current distance. It clearly has not been receding very fast."Sedimentary rhythmites of siltstone and fine sandstone from late Precambrian (c. 650-800 Ma) glaciogenic formations in South Australia are interpreted as distal ebb-tidal deposits that record variability in the velocity and range of palaeo-ebb tides. Variations in lamina thickness encode a full spectrum of palaeotidal cycles, including semidiurnal, diurnal, fortnightly and monthly tidal cycles as well as the lunar apsides (perigee) and nodal cycles. A half-yearly oscillation is attributable largely to a beat between the fortnightly tidal cycles of luni-solar conjunction and lunar declination; the lunar nodal cycle is discernible as an amplitude modulation of this beat oscillation.
The data allow determination of the Earth's palaeorotation and the past dynamics of the Earth-Moon system with an accuracy previously unattainable for the Precambrian. The late Precambrian (c. 650 Ma) year contained 13.1 (+/-0.5) lunar months and c. 400 (+/-20) days, and the late Precambrian lunar month c. 30.5 (+/-1.5) days. These value suggest an average equivalent phase lag near 3[deg] since late Precambrian time rather than the present value of 6[deg]. The period of 19.5 (+/-0.5) years determined for the lunar nodal cycle c. 650 Ma ago indicates a lunar distance 96.9 (+/- 1.7)% of the present distance. The low rate of lunar recession since late Precambrian time revealed by the rhythmite data militates against a close approach of the Moon during the Proterozoic. Precambrian sedimentary rhythmites may hold a key to the early history of the Earth's rotation."~G. E. Williams, "Late Precambrian tidal rhythmites in South Australia and the history of the Earth's Rotation," Journal of the Geological Society, London, Vol. 146, 1989, p. 97. [emphasis added]
Even if these values are off, and even if you don't accept the range of 650 million years, this shows strong evidence that in the past, the overall tidal friction was less and therefore the rate of recession of the Moon was SLOWER, clearly demonstrating that the basis for this Young Earth claim is invalid!!!
Future rate of recession:
The recession of the moon is due to the friction caused by the tidal bulge of the earth being
carried forward of the moon by the earth's rotation. This angle
causes the earth's rotation to slow down. This energy is
transferred to the Moon, causing it to speed up and therefore recede. When the moon becomes synchronous with the earth's rotation, no further
recession will occur. The earth and moon will circle each with the
same face shining towards each other. The earth's rotation will be
one month and the moon's orbital period will be one month (but a month
will be much longer then). This will happen when the moon is
645,000 km from the earth. (Frank D. Stacey, Physics of the Earth
History of this Young Earth claim:
It appears that Thomas Barnes (see also
Magnetic Field) is one of the earliest to popularize this claim.
See
Young age for the Moon and Earth
Other Opinions
Young Earth View
Old Earth View
General Science about the Earth and Moon
Viewer Feedback
2005-12-16 Ty (Young Earth Creationist) wrote
Biased to Evolution
I was pleased you put a link to Malcolm Bowden's rebuttal of Tim
Thompson’s “The Recession of the Moon.” I would just add a
link to Walt Brown's explanation as well:
www.creationscience.com/onlinebook/TechnicalNotes2.html#wp1030385
epicidiot's reply
Thanks. I try to include many points of view, even those I don' t agree with. I have also added the link you suggested (see Center for Scientific Creation above).
I like the link you suggested because it has a really good description of the math behind why the Moon recedes. I recommend it to anyone who wants to understand the basic principle of why the moon recedes. However, I feel that I have failed you. I was hoping that after reading my page, one would understand why what he is doing is wrong. Both on a theoretical and empirical basis.On a theoretical basis, his model makes three fatally wrong assumptions.
- The Earth is a perfect sphere.
- The surface of the Earth is smooth.
- The surface of the Earth is covered with water.
Remember, his model is based on the size of the tidal bulge. For his model to work, then anything that changes the size of the bulge must be accounted for. All of the above factors have a major impact on the size of the tidal bulge and therefore must be considered for the model to work. This model is useful as an aid to understanding the problem, but without including the necessary factors, it is useless for calculating realistic values.
Even if one doesn't understand the math behind his model, it offers one obvious clue that his model is theoretically wrong:
His model presumes to be able to predict the rate of recession of the Moon based on the distance between the Moon and the Earth and the tidal bulge that it creates. Yet, he has to use the measured value for the current recession. If his model was accurate, then he could simply calculate that value using his model. Obviously, his model is not capable of doing this (That's because it doesn't account the factors listed above). He is simply using the current recession rate to estimate the effect of these factors (as they exist now) and then extrapolating backwards in time. This might work if the factors that affect the tidal bulge never changed. But we know that's not true. The continents have moved, mountains have come and gone, and ocean levels have risen and fallen. All of these have major impacts on the tidal bulge, and thus the recession rate, therefore rendering his results meaningless.On an empirical basis, he simply ignores the physical evidence that shows that his model is wrong. See the Physical Evidence presented above.
He answered "how fast would the Moon recede in the past if the Earth was a smooth sphere covered with water and the factors that affect its recession never changed." He should have answered, "how fast would the Moon recede in the past given the conditions of the Earth at that time."
In short, he did a great job of answering the question. Unfortunately, he answered the wrong question.
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2006-08-04 22:38:44, Atheistic Evolutionist wrote
Interesting, Factual, Fair and Balanced
