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Author Topic:   Moons: their origin, age, & recession
Calypsis4
Member (Idle past 5214 days)
Posts: 428
Joined: 09-29-2009


Message 1 of 2 (528359)
10-05-2009 10:32 PM


A few years ago I got into a heated debate with an astronomer from Princeton about the supposed 4.6 billion yr age of earths moon. I stated that I felt the figure was an error because mathmatically, when one considers the 4 cm per yr recession of the moons orbit around the earth then if one computes the time frame then the moon would have been touching the earth about 1.7 billion yrs ago.
The professor found what he thought was an error in my math and ridiculed me when I replied that his formula did not consider the very necessary factor of a change in recessional velocity because of the change in gravitational pull as the moon got further from earth. For the sake of those not adept in physics I posted something I felt at least some of the readers could grasp: the law of inverse varition r1/r2 = t2/t1. He scoffed at me and challenged me with the standard lunar recession formula among evolutionist astronomers):
DF / DR = 2Gm1m2 / R3
Quote: "DF / DR represents a change in the force (DF) with respect to a change in distance (DR). That variation in force, or tidal gradient, is what produces the distortion in the shape of both Earth and the moon."(talk/origins).
But I knew that did not comport with reality because the moon's recession would be changed by the inverse square law as it receded further and further from earth. But 'the force of gravity changes with the square of the distance, such that if the distance is reduced by 1/2 the force of gravity increases by a factor of four'. (Creation/Wiki).
I phoned Dr. Don DeYoung, the head of the physics dept. at Grace College in Indiana & asked his opinion about the matter and he told me that the evolutionist formula for lunar recession as far as the age of the moon is in error. Here is why:
1. 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/R^6,
where k is a constant = (present speed: 0.04 m/year) x (present distance: 384,400,000 m)^6 = 1.29x1050 m^7/year. Integrating this differential equation gives the time to move from Ri to Rf as t = 1/7k(Rf^7 Ri^7). For Rf = the present distance and Ri = the Roche Limit, t = 1.37 x 10^9 years.
2. It can be restated this way:
'To compute the moon’s recession time to its present orbit, we first integrate equation (1). Over the time interval 0 to t, the moon’s distance from the earth increases from the Roche limit r0 to its present orbit at distance r:in which t is the maximum age of the earth-moon system. The present value of r is 3.844 x 10^8 m. For an object orbiting a planet, the Roche limit r0 is where R is the radius of the central body (the earth in this case); p(sub)m is the density of the central body; and m is the density of the orbiting body, in this case the moon. With R = 6.3781 x 10^6 m for the earth; p(sub)m = 5515 kg/m^3; and p(sub)m = 3340 kg/m^3, we find that r0 = 1.84 x 10^7 m. This is less than 5% of the moon’s current orbital radius.
From equation (1), the proportionality constant k is the product of the sixth power of the distance r, and the current recession rate. The present value of the recession rate is 4.4 0.6 cm/yr, or (4.4 0.6) x 10^—2 m/yr. Therefore, k = 1.42 x 10^50 m^7/yr. With this value for k, the right hand side of equation 1 equals the present recession rate dr/dt, when r = the moon’s current orbital radius.
From equation (2), the time for the moon to recede from r0 to r is 1.3 Ga. Without introducing tidal parameters, to be discussed below, this is the moon’s highest allowable evolutionary age.' The Astromony Book by Dr. Jonathan Henry.
So the upper limit of the age of lunar recession for the moon in its recession from the earth is no more than 1.2 or 1.3 billion yrs ago.
The Roche Limit (closest the moon could have ever been to the earth) was also taken into consideration because had the lunar body been any closer to earth than that it would have disintigrated. Actually, the earth and moon would have pulled each other apart.
So the change in velocity over time is seen by this:
So the velocity of lunar recession changes with the 6th power of the distance.
George Darwin stated, ‘Thus, although the action [rate of lunar recession] may be insensibly slow now, it must have gone on with much greater rapidity when the moon was nearer to us.' Darwin, G., The Tides, Houghton Mifflin, Boston, pp. 278—286, 1898
So the law of inverse variation DOES play a very important factor in determining how far back one can take the formula to determine the length of the time of lunar recession. The evolutionary time scale as it concerns the age of the moon is in error.
Interesting that the last time I approached the Princeton astronomer with these facts he didn't attempt to refute it.
Edited by Calypsis4, : change from 'an increase' to a 'change'.

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Message 2 of 2 (528382)
10-06-2009 12:20 AM


Thread Copied to Big Bang and Cosmology Forum
Thread copied to the Moons: their origin, age, & recession thread in the Big Bang and Cosmology forum, this copy of the thread has been closed.

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