Tidal lock - Revision history

Dataclarifier: /* Problems for uniformitarianism posed by tidal lock */ linked dynamics

2019-07-05T16:34:08Z

Problems for uniformitarianism posed by tidal lock: linked dynamics

DavidB4-bot: /* Problems for uniformitarianism posed by tidal lock */Spelling/Grammar Check, typos fixed: Indeed → Indeed, (2)

2016-09-10T17:32:56Z

Problems for uniformitarianism posed by tidal lock: Spelling/Grammar Check, typos fixed: Indeed → Indeed, (2)

DavidB4-bot: /* See also */clean up & uniformity

2016-07-13T20:34:47Z

DanAP at 07:53, November 23, 2012

2012-11-23T07:53:39Z

TerryH: /* Problems for uniformitarianism posed by tidal lock */

2008-07-05T14:46:11Z

Problems for uniformitarianism posed by tidal lock

TerryH: /* Example */ More sections, including a formula to calculate tidal lock time

2008-07-05T14:45:14Z

Example: More sections, including a formula to calculate tidal lock time

Aziraphale: categorize

2007-07-16T19:53:22Z

categorize

Vossy: wikifying article

2007-03-24T07:09:17Z

wikifying article

Donalbain: Created page

2007-02-28T09:43:53Z

Created page

New page

Tidal locking is the process by which two bodies in an orbital relationship will, over time, come to show the same face to one another. In other words, the period of rotation about the axis of the body will come to match the body's orbital period.

'''Mechanism'''

Considering two bodies, one larger (A) than the other (B):
Body A will exert a gravitational force on B, causing B to be bulged towards body A.

As body B continues to rotate, a different part of the surface will be pulled towards A. In effect, the bulge will "move". However, the material of body B will resist being warped in this way, resulting in a torque that will affect the rotation of B.

This torque acts in such a way that eventually, the rotation of B is such that the same face always points towards A.

This process will also alter the rotation of body A, but if A is much larger, then the process will take a greater amount of time.

'''Example'''

One example of tidal locking is the [[Earth]]/[[Moon]] system. The moon has become tidally locked, and so continually shows the same face to inhabitants of planet Earth.

'''See also'''

@@ Line 35: / Line 35: @@
 == Problems for uniformitarianism posed by tidal lock ==
-Tidal locking is as likely to happen to the primary as to the moon. Indeed, [[Pluto]] and [[Charon]] are mutually locked. But tidal lock has its most profound implications for the Earth-Moon system. Though the presence of tidal locking might appear to militate in favor of a great age for the solar system, the dynamics of tidal lock suggest youth, not age.
+Tidal locking is as likely to happen to the primary as to the moon. Indeed, [[Pluto]] and [[Charon]] are mutually locked. But tidal lock has its most profound implications for the Earth-Moon system. Though the presence of tidal locking might appear to militate in favor of a great age for the solar system, the [[Dynamics (physics)|dynamics]] of tidal lock suggest youth, not age.
 As earth's rotation decreases, the moon must recede from the earth, or else angular momentum is not conserved (see above). Therefore, the rate of deceleration of Earth's rotation must itself decelerate over time. For that reason alone, the Earth-Moon system cannot be more than 1.2 billion years old, because at such a time the Earth would have been rotating dangerously fast, and the Moon would have been touching the Earth.

@@ Line 35: / Line 35: @@
 == Problems for uniformitarianism posed by tidal lock ==
-Tidal locking is as likely to happen to the primary as to the moon. Indeed [[Pluto]] and [[Charon]] are mutually locked. But tidal lock has its most profound implications for the Earth-Moon system. Though the presence of tidal locking might appear to militate in favor of a great age for the solar system, the dynamics of tidal lock suggest youth, not age.
+Tidal locking is as likely to happen to the primary as to the moon. Indeed, [[Pluto]] and [[Charon]] are mutually locked. But tidal lock has its most profound implications for the Earth-Moon system. Though the presence of tidal locking might appear to militate in favor of a great age for the solar system, the dynamics of tidal lock suggest youth, not age.
-As earth's rotation decreases, the moon must recede from the earth, or else angular momentum is not conserved (see above). Therefore the rate of deceleration of Earth's rotation must itself decelerate over time. For that reason alone, the Earth-Moon system cannot be more than 1.2 billion years old, because at such a time the Earth would have been rotating dangerously fast, and the Moon would have been touching the Earth.
+As earth's rotation decreases, the moon must recede from the earth, or else angular momentum is not conserved (see above). Therefore, the rate of deceleration of Earth's rotation must itself decelerate over time. For that reason alone, the Earth-Moon system cannot be more than 1.2 billion years old, because at such a time the Earth would have been rotating dangerously fast, and the Moon would have been touching the Earth.
 == References ==

@@ Line 46: / Line 46: @@
 * [[Gravity]]
-[[category:astronomy]]
+[[Category:Astronomy]]
-[[category:moon]]
+[[Category:Moon]]

← Older revision		Revision as of 07:53, November 23, 2012
Line 47:		Line 47:

	[[category:astronomy]]		[[category:astronomy]]
		+	[[category:moon]]

@@ Line 37: / Line 37: @@
 Tidal locking is as likely to happen to the primary as to the moon. Indeed [[Pluto]] and [[Charon]] are mutually locked. But tidal lock has its most profound implications for the Earth-Moon system. Though the presence of tidal locking might appear to militate in favor of a great age for the solar system, the dynamics of tidal lock suggest youth, not age.
-As earth's rotation decreases, the [[moon recession|moon must recede]] from the earth, or else angular momentum is not conserved (see above). Therefore the rate of deceleration of Earth's rotation must itself decelerate over time. For that reason alone, the Earth-Moon system cannot be more than 1.2 billion years old, because at such a time the Earth would have been rotating dangerously fast, and the Moon would have been touching the Earth.
+As earth's rotation decreases, the moon must recede from the earth, or else angular momentum is not conserved (see above). Therefore the rate of deceleration of Earth's rotation must itself decelerate over time. For that reason alone, the Earth-Moon system cannot be more than 1.2 billion years old, because at such a time the Earth would have been rotating dangerously fast, and the Moon would have been touching the Earth.
 == References ==

← Older revision		Revision as of 14:45, July 5, 2008
Line 15:		Line 15:

	One example of tidal locking is the [[Earth]]/[[Moon]] system. The moon has become tidally locked, and so continually shows the same face to inhabitants of planet Earth.		One example of tidal locking is the [[Earth]]/[[Moon]] system. The moon has become tidally locked, and so continually shows the same face to inhabitants of planet Earth.
		+
		+	The earth's rotation is itself slowing. Given enough time, the earth could lock itself to face the Moon.
		+
		+	== Time scale ==
		+	The time required for tidal lock is difficult to estimate, primarily because it depends on many factors, unique to any given satellite or primary, that are difficult to measure. The formula for the time required for any moon to enter tidal lock with its primary is:<ref name=Gladman>Gladman B., Quinn D. D., Nicholson P., and Rand R. "[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45MH0T4-32&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6d63ca17a7e56eb1fc7fc5129527f822 Synchronous Locking of Tidally Evolving Satellites]." ''Icarus'' 122(1):166-192, July 1996. {{doi\|10.1006/icar.1996.0117}} Accessed July 4, 2008.</ref>
		+
		+	<math>t_{\textrm{lock}} = \frac{16 \rho \omega a^6 Q}{45 G m_p^2 k_2}</math>
		+
		+	where
		+	*<math>\rho\,</math> is the density of the moon
		+	*<math>\omega\,</math> is the initial rotation rate in rad s⁻¹
		+	*<math>a\,</math> is the [[semi-major axis]] of the moon's orbit.
		+	*<math>Q\,</math> is the ''dissipation function'' of the moon (not to be confused with its apo[[apsis]]).
		+	*<math>G\,</math> is the gravitational constant.
		+	*<math>m_p\,</math> is the mass of the primary.
		+	*<math>k_2\,</math> is the tidal second-order ''Love number'' of the moon.
		+
		+	Thus the time required is very sensitive to orbital distance and somewhat less sensitive to the mass of the primary. Thus dense moons relatively close to their primaries are more likely to be in tidal lock.
		+
		+	== Problems for uniformitarianism posed by tidal lock ==
		+	Tidal locking is as likely to happen to the primary as to the moon. Indeed [[Pluto]] and [[Charon]] are mutually locked. But tidal lock has its most profound implications for the Earth-Moon system. Though the presence of tidal locking might appear to militate in favor of a great age for the solar system, the dynamics of tidal lock suggest youth, not age.
		+
		+	As earth's rotation decreases, the [[moon recession\|moon must recede]] from the earth, or else angular momentum is not conserved (see above). Therefore the rate of deceleration of Earth's rotation must itself decelerate over time. For that reason alone, the Earth-Moon system cannot be more than 1.2 billion years old, because at such a time the Earth would have been rotating dangerously fast, and the Moon would have been touching the Earth.
		+
		+	== References ==
		+	{{reflist\|1}}

	==See also==		==See also==

← Older revision		Revision as of 19:53, July 16, 2007
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	* [[Lunar tides]]		* [[Lunar tides]]
	* [[Gravity]]		* [[Gravity]]
		+
		+	[[category:astronomy]]

@@ Line 1: / Line 1: @@
-Tidal locking is the process by which two bodies in an orbital relationship will, over time, come to show the same face to one another. In other words, the period of rotation about the axis of the body will come to match the body's orbital period.
+==Mechanism==
 Considering two bodies, one larger (A) than the other (B):
@@ Line 13: / Line 12: @@
 This process will also alter the rotation of body A, but if A is much larger, then the process will take a greater amount of time.
-'''Example'''
+==Example==
 One example of tidal locking is the [[Earth]]/[[Moon]] system. The moon has become tidally locked, and so continually shows the same face to inhabitants of planet Earth.
-'''See also'''
+==See also==