Rotation of the Earth

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The rotation of the Earth (and its change over time) is significant because it is evidence for an old Earth, yet Young earth creationists (YECs) try to use it as evidence for a young one.

Old Earth

See the main article on this topic: Evidence against a recent creation

There are two separate lines of evidence for an Old Earth coming from the slowing rotation of the Earth.

Coral

Thwaites et al. (1982) suggests that the Earth's rotation slows by 0.005 seconds per year, every year (0.005 s/yr²). Because the rate of change of the rotation of the Earth is relatively predictable, we would predict a 22.7 hour-long day (in a year of 386.2 days) about 370 million years ago.

$-0.005{\text{ s/yr}}^{2}\times -370{\text{ million yr}}=+1,850,000{\text{ s/yr}}=+21.4{\text{ days/yr}}$

$(365.25+21.4){\text{ days/yr}}=386.66{\text{ days/yr}}$

${\frac {8766{\text{ hrs/yr}}}{386.66{\text{ days/yr}}}}=22.7{\text{ hrs/day}}$

Measurements of the Earth's past rotation rates go back to work on the growth lines of rugose corals by John Wells (1963), who discovered that a year in Devonian times (radiometrically dated to ca. 370 million years ago) had around days of about 22 hours (in a year of about 400 days). This (rough) agreement between multiple dating methods (radiometric dating, coral clocks, and the Earth's rotation) suggests an old Earth.

Tidal rhythmites

More recent work suggests that the Earth's day was 21.9±0.4 hours long about 620 million years ago, a value derived from studying "tidal rhythmites" of Elatina and Reynella, Australia.

Again using Thwaites et al. 1982, we would predict a 21.9 hour-long day (in a year of 401 days) about 620 million years ago.

$-0.005{\text{ s/yr}}^{2}\times -620{\text{ million yr}}=+3,100,000{\text{ s/yr}}=+35.9{\text{ days/yr}}$

$(365.25+35.9){\text{ days/yr}}=401.13{\text{ days/yr}}$

${\frac {8766{\text{ hrs/yr}}}{401.13{\text{ days/yr}}}}=21.9{\text{ hrs/day}}$

Again, this (rough) agreement between multiple dating methods (radiometric dating, tidal rhythmites, and the Earth's rotation) suggests an old Earth.

Chambered nautilus

Sometimes creationists will bring up the failures of using the chambered nautilus to measure number of days. As Dave Matson of Talk Origins explains:

Studies of the chambered nautilus, for a time, was also proposed as a geologic clock by Kahn and Pompea. However, that effort ran into problems. Creationists still cite it in their efforts to discredit the coral clocks. Each case, of course, has to be judged on its own merits. The nautilus is not a coral, and the coral clocks are good enough to destroy the young-earth claims.

Slower past rate

The present rate of slowing of the Earth's rotation may be off (though this, if anything, would further support an old Earth). Sonleitner 1991 wrote:

[T]he correct present rate of slowing of the earth's rotation is excessively high, because the present rate of spin is in a resonance mode with the back-and-forth motion of the oceans' waters in the ocean basins. In past ages when the rotation rate was faster, the resonance was much less or nonexistent, resulting in a much more gradual slowing of the rotation rate. The most recent calculations indicate that the earth could be 4 to 5 billion years old and not have been spinning excessively fast or requiring the moon to be any closer to the earth than 225,000 kilometers (140,000 miles).

Young Earth

See the main article on this topic: Young Earth creationism

Creationists argue that the Earth's slowing rotation independently proves a young universe and supports proof that the moon could not have been old. Kent Hovind of Creation Science Evangelism said:

“”The earth's rotation is slowing down, meaning that the earth can't be older than a few million years.

Although Mark Isaak references Eicher (1976) for a 2 second/100,000 year (0.00002 s/yr) slowdown of the Earth's rotation, the more recent Thwaites et al. (1982) suggests that the Earth's rotation slows 0.005 seconds per year per year (0.005 s/yr²). Even given this faster rate of slowing, there's no trouble with a 4.6 bn year old Earth:

$-0.005{\text{ s/yr}}^{2}\times -4.6{\text{ billion yr}}=+23,000,000{\text{ s/yr}}=+266.20{\text{ days/yr}}$

$(365.25+266.20){\text{ days/yr}}=631.45{\text{ days/yr}}$

${\frac {8766{\text{ hrs/yr}}}{631.45{\text{ days/yr}}}}=14{\text{ hrs/day}}$

While a 14-hour day may seem strange, it's certainly not impossible. In fact, it's exactly the conclusion that Thwaites et al 1982 come to.

Mark Isaak of TalkOrigins notes that there are several lines of evidence (even before 1980) for a faster past Earth rotation (numbered-points added):

The rate of earth's rotation in the distant past can be measured.

1. Corals produce skeletons with both daily layers and yearly patterns, so we can count the number of days per year when the coral grew. Measurements of fossil corals from 180 to 400 million years ago show year lengths from 381 to 410 days, with older corals showing more days per year (Eicher 1976; Scrutton 1970; Wells 1963; 1970).
2. Similarly, days per year can also be computed from growth patterns in mollusks (Pannella 1976; Scrutton 1978)
3. and stromatolites (Mohr 1975; Pannella et al. 1968)
4. and from sediment deposition patterns (Williams 1997).

All such measurements are consistent with a gradual rate of earth's slowing for the last 650 million years.

Faster lunar recession

See the main article on this topic: Lunar recession

YECs argue that a faster Earth rotation would mean a faster Moon recession, which means a young Earth. They're wrong.

Biblical scientific errors

See the main articles on this topic: Biblical scientific errors § Rotation of the Earth and Biblical scientific foreknowledge

Some fundamentalists argue that the Bible shows scientific foreknowledge by predicting that the Earth rotates. Instead, the Bible assumes a geocentrist universe by implying that the Sun goes around the Earth, rather than the Earth rotating.

See also

• Lunar recession (the moon is going away from the Earth too fast)
• Lunar dust (there's not enough moon dust)
• Lunar formation (the moon couldn't have formed)
• Lunar radioactivity (the moon is too hot)
• Lunar atmosphere (there's too much moon gas)
• Lunar bukkake hypothesis (the moon got shot with water during the Flood)