A creationist website makes this argument for the 6,000 year old earth. I'm embarrassed to say I don't know how to do the math to evaluate the claim myself. However, the time scales involved seems to lend some credence to this argument. "The Moon is slowly drifting away from the Earth. If it is getting further, at one time it was much closer. The Inverse Square Law dictates that if the Moon were half the distance from the Earth, its gravitational pull on our tides would be quadrupled. 1/3 the distance, 9 times the pull. Everything would drown twice a day. Approximately 1.2 billion years ago, the Moon would have been touching the Earth. Drowning would be the least of our concerns! - See more at: http://www.allaboutcreation.org/how-old-is-the-earth.htm#sthash.LSHK4GQk.dpuf"

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    $\begingroup$ Tides go by the inverse cube in distance from the primary. $\endgroup$ – dmckee --- ex-moderator kitten Feb 12 '14 at 3:40
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    $\begingroup$ Various related posts: physics.stackexchange.com/q/31429 physics.stackexchange.com/q/47829 and I think there are a couple of others. Also one of the answer to that first link is pretty close to what you want to know. $\endgroup$ – dmckee --- ex-moderator kitten Feb 12 '14 at 3:41
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    $\begingroup$ You know, I did start to write an answer, but then I looked at the link. It is pointless for scientists to engage with drivel like this that fails on every level to pass any kind of evidential test itself. $\endgroup$ – Rob Jeffries Nov 19 '14 at 20:15
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    $\begingroup$ Your tidal math is correct for the most part. At a Geostationary orbit tides stop moving around the planet and inside the solid object Roche limit the Moon would begin to break apart, so there are limits to how close the Moon could have once been, but it's very possible we had tides of a couple hundred feet high about 4.2-4.3 billion years ago. That would have been fun to see. The Moon when it formed, it probably glowed red like hot lava for at least a little while, and it was much closer. That would have been fun to see too. $\endgroup$ – userLTK Nov 15 '15 at 5:24
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    $\begingroup$ In the Creationistverse, the laws of physics are such that it is consistent with the the 6,000 year old earth theory. $\endgroup$ – Count Iblis Nov 15 '15 at 18:48

Extrapolation is as likely to produce meaningless results when done into the past as when done into the future.

The most widely accepted theory for how the Earth-Moon system was formed is the Giant impact hypothesis: around 4.5 billion years ago, the (then itself still very new) Earth was nearly destroyed by a collision with another planet roughly the size of Mars. This created a huge cloud of debris orbiting the Earth, much of which coalesced into the moon.

So the moon first formed at a certain distance from the Earth, and that distance has since then grown due to tidal braking (and the same effect is steadily increasing the length of the day on Earth).

An interesting detail about your quote is that their extrapolation of 1.2 billion years is much shorter than the time since the impact, but without any indication of how that number was computed, it means nothing. It is not a linear extrapolation of the current distance (384,000km) and rate of increase (3.8cm/a) because that yields over 10 billion years. But the rate of increase really cannot be meaningfully extrapolated because it depends on the magnitude of friction caused by tidal forces, and that depends on what the Earth looks like. After the impact, the Earth was probably mostly liquid for some time, which would cause much more tidal friction and thus a much more rapid increase in distance.

But the creationists are correct about one thing: Drowning would, indeed, be the least of our concerns back then!


63,360 x 238,900 = 15,136,704,000(inch now) (1.5inch x 4,000,500,000 = 6,000,750,000) 15,136,704,000 - 6,000,750,000 (inch then ) = 9,135,954,000 inches. 9,135,954,000/63360=144,191.19318181 (converting it back to miles)

Roughly 144,000 miles 4.5 billion years ago

But due to the tidal friction, caused by the tidal bulge, the earth loses energy and is given to the moons orbit at a slower and slower rate as time goes by so it was much less than 144,000 miles.

The rate of the moons movement (away from earth) decreases as the moons distance (away from earth) increases.

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    $\begingroup$ The rate of movement varies with the height of the tidal bulge. The closer the Moon is to the earth, provided the Earth has oceans and the Earth rotates faster than the Moon orbits, the Moon will move away. There also may have been 4.5 billion years ago, there probably was one 4.4, certainly 4.3 billion years ago, some debate on the age, but when the Moon formed it was closer than 144,000 miles. It was about 20,000-30,000 miles away but it moved away fairly quickly due to the enormous tides when it was that close. Now it's moving away much slower than it used to. $\endgroup$ – userLTK Nov 15 '15 at 5:12
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    $\begingroup$ And radiocarbon dating produces false results only when it's mishandled and it's not used for dating the age of the Earth anyway. Uranium-Lead dating is used to determine the age of the Earth and while an individual test can produce a false result due to contamination, that question has been tested enough times to have a good degree of certainty. Your answer has some flat out scientifically incorrect statements in it. I don't want to vote you down, but you shouldn't post incorrect statements about science. $\endgroup$ – userLTK Nov 15 '15 at 5:19

I just stumbled across this more than two years after the fact. Interesting conversation.

One thing that the creationist website and the answers I've seen in this forum have failed to address, is that the increased tidal action would not be the only effect of a closer Moon. The farther back we look in time the less chance the moon would be able to escape the Earth's gravity. It should be getting closer today and yet it is moving away instead.

For the sake of argument let's assume that the aforementioned idea that the moon was caused by a collision of another Celestial body with the primordial Earth is indeed what occurred. That leaves us with a contradiction.

With an exponential increase in gravity the closer the Moon and Earth are to one another, in order to maintain the proper balance to sustain its orbit until now, the moon would also have to be going exponentially faster the further back in time. That being the case, the debris from the Collision could never have coalesced into the moon in the first place. (These same factors, also mean the death of the capture Theory.)

Assuming such exponential speeds were not present at the time of the Collision, means the debris that would have coalesced into the Moon, would need to have accelerated dramatically once it had. This again would not have happened.

Further, through observation, we know that objects in space that break apart within the gravitational field of a planet, do not coalesce back into a localized Mass. Instead, due to the influence of the nearby gravitational field, they remain a debris field because the field exerts greater influence on the individual bits of debris than they can exert on one another.

This does not even consider heat pressure; another force working against coalescence. This, among other reasons, is the same reason nebula are coming apart rather than coalescing into new stars.


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