Tidal interaction with the Earth: Made the argument for a - not particularly accurate - "tidal clock", without reference to other methods of dating the deposits. No circularity.
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The motion of the Moon around the Earth can be considered a balance between gravitational attraction and (fictitious) centrifugal force. The balance is only an average, so on the side of the Earth facing the Moon, the gravitational attraction toward the Moon is somewhat larger and the centrifugal force away from it is somewhat smaller. On the other side of the Earth the centrifugal force away from the Moon is slightly larger than the gravitational attraction towards it. The net result of these forces in opposite directions is that the Earth bulges on the side toward the Moon but also on the side away from the Moon. Since the solid Earth cannot deform much, and changes in the atmosphere do not have many consequences, this effect is seen most clearly on the water of the oceans. The bulges of water are the high tides. Since in the course of any day any spot on the Earth is once directly under the Moon and once on the opposite side, there are generally two high tides a day, with corresponding low tides in between. The Sun also produces tides that are somewhat smaller, so they effectively either increase or decrease the amplitude of the Lunar tides, depending on the relative position of the Sun and Moon (or equivalently, the phase of the Moon).
The motion of the Moon around the Earth can be considered a balance between gravitational attraction and (fictitious) centrifugal force. The balance is only an average, so on the side of the Earth facing the Moon, the gravitational attraction toward the Moon is somewhat larger and the centrifugal force away from it is somewhat smaller. On the other side of the Earth the centrifugal force away from the Moon is slightly larger than the gravitational attraction towards it. The net result of these forces in opposite directions is that the Earth bulges on the side toward the Moon but also on the side away from the Moon. Since the solid Earth cannot deform much, and changes in the atmosphere do not have many consequences, this effect is seen most clearly on the water of the oceans. The bulges of water are the high tides. Since in the course of any day any spot on the Earth is once directly under the Moon and once on the opposite side, there are generally two high tides a day, with corresponding low tides in between. The Sun also produces tides that are somewhat smaller, so they effectively either increase or decrease the amplitude of the Lunar tides, depending on the relative position of the Sun and Moon (or equivalently, the phase of the Moon).
−
In detail, the tides are much more complicated than this and have been the subject of scientific investigation for hundreds of years.
One of these details is
the
fact that
friction
between
the
land and
the
oceans tends
to
slow down
the rotation of the Earth and
also
to
move
the
tidal bulge out
of
line with
the
Moon
,
which results in
the Moon moving
slowly
away from the Earth
. Currently
the
distance between
the
Earth
and the
Moon
is
increasing at
the rate of 3.8 [[centimeter]]s per year.<ref>[http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html Apollo Laser Ranging Experiments Yield Results]</ref>
, as measured by lasers bounced off reflectors left on the Moon
.
+
In detail, the tides are much more complicated than this and have been the subject of scientific investigation for hundreds of years.
+
For example,
the friction
of
the
water moving over
the
sea floor results in a transfer of angular momentum from the Earth
to the
Moon. This can be observed in a few different ways.
+
* The
rotation of the Earth
is slowing down, the length of the day is increasing,
and
the number of days in a year is decreasing. This could in principle be measured directly by modern astronomical methods, but the slow change is swamped by a number of other effects. The most accurate way
to
determine
the
rate at which the length
of the
day is changing currently is by examining records of the location of total solar eclipses over the last 27 centuries. The result is 1.7 ms/day/cy (milliseconds per day per century)
,
but it is believed that post glacial rebound since
the
last ice age is causing the equivalent of a speed-up of 0.6 ms/day/cy, so that the effect of the tides is actually 2.3 ms/day/cy.
+
* The
Moon
is
moving
farther
away from the Earth
,
the
length of
the
lunar month is increasing,
and the
number of months in a year
is
decreasing. The most accurate way to measure
the
current
rate of
these changes is by measuring the distance to the Moon with lasers, which gives
3.8 [[centimeter]]s per year.<ref>[http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html Apollo Laser Ranging Experiments Yield Results]</ref>.
−
The current
distance between the Earth and the Moon,
center to center, is 384,000 km
.
The surfaces
would
touch at a distance
of
8
,
000 km
,
and
the Moon would
disintegrate if it were within
the Roche limit, somewhere between 9,500 and 18,000 km, depending on whether the Moon were solid or liquid at the time.
These corrections can be ignored here. If
the
recession has always been
at
the present rate
,
then
the
maximum time the Moon could have been orbiting the Earth is 10 billion years (384,000 km ÷ 3.8 cm per year).
+
Tidal acceleration decreases rapidly with increasing
distance between the Earth and the Moon
. If nothing intervenes
,
eventually a point would be reached billions of years in the future when the rotation of the Earth has slowed so much that it rotates at the same rate as the Moon revolves around the Earth
.
Tides
would
then cease to exist and slowing
of
the rotation would stop. In the same way
,
one could hypothetically extrapolate the dynamics of the Earth-Moon system into the distant past. At increasingly remote past times
, the Moon would
have been closer and closer to the Earth, although the distance could never have been less than
the Roche limit, somewhere between 9,500 and 18,000 km, depending on whether the Moon were solid or liquid at the time.
Taking
the
larger tidal forces
at
smaller separations into account
,
but neglecting any changes in
the
geometry
of the
oceans
, the Earth-Moon system could not
have existed for longer
than
about
1.5 billion years
,
{{ref|Bruce G. Bills and Richard D. Ray, [http://onlinelibrary.wiley.com/doi/10.1029/1999GL008348/abstract "Lunar orbital evolution: A synthesis of recent results". ''Geophysical Research Letters'', Volume 26, Issue 19, pages 3045–3048, 1 October 1999.}} which is 3 times lower than the age derived from [[radioactive dating]].
−
This simple estimate must be modified by a number
of
factors,
the
most important of these being that the tidal interaction decreases rapidly with the separation of the bodies.
+
−
If the tidal dissipation has always had its present value
,
then
the Earth-Moon system could not
be older
than 1.5 billion years{{ref|Bruce G. Bills and Richard D. Ray, [http://onlinelibrary.wiley.com/doi/10.1029/1999GL008348/abstract "Lunar orbital evolution: A synthesis of recent results". ''Geophysical Research Letters'', Volume 26, Issue 19, pages 3045–3048, 1 October 1999.}}
,
which is 3 times lower than the age derived from [[radioactive dating]].
+
−
Another potentially large effect is the configuration of the oceans and continents. This is the explanation favored by secular scientists to explain the discrepancy.
+
−
Calculations show that configurations with fewer continents, especially if there are no continents oriented north-south as North and South America or Europe and Africa are now, have much less tidal braking.
+
−
The continental drift is presently measured to be typically a few centimeters per year, at which rate global reconfigurations would be possible on the time scale of hundreds of millions of years.
+
−
However, such continental arrangements are speculative, and are nor proposed for at least the last 600 million years.{{ref|{{author|Ron|Blakey}}, [http://cpgeosystems.com/mollglobe.html Mollewide Plate Tectonic Maps].}}
+
−
Secular scientists see confirmation
of
their model in
the
patterns
of
layers
found in
tidal rhythmites{{ref|Rajat Mazumder and Makoto Arima
,
[http://www.mantleplumes.org/WebDocuments/MazumderESR2004.pdf Tidal rhythmites and their implications]
,
''Earth-Science Reviews'' '''69''' (2005) 79–95}}{{ref|George E. Williams, [http://onlinelibrary.wiley.com/doi/10.1029/97GL00234/abstract Precambrian length of day
and the
validity of tidal rhythmite paleotidal values]
.
''Geophysical Research Letters'', Volume 24, Issue 4, pages 421–424, 15 February 1997. NATURE, March 9, 1963.}} (alternating layers
of
sand
and
silt laid down offshore from estuaries having great tidal flows)
,
and in sclerochronology
{{ref|
JOHN W. WELLS
, [http://
freepages.genealogy.rootsweb.ancestry
.com/
~springport/geology/coral_growth
.html
CORAL GROWTH AND GEOCHRONOMETRY
]}}
(analysis
of
the growth bands of corals, shells, and stromatolites). Daily, monthly and seasonal cycles can be found in the deposits. Data consistent
with
an origin of
the
Moon some 4
.
5 billion years ago has
been
reported for deposits dated between 0
.
5
and
2.5 billion years before the present.
+
Modeling
of the
tides is very complex, involving resonance effects and dissipation as well as simple gravitational forces. Most
of
the dissipation is
found
to occur
in
a turbulent bottom boundary layer in shallow seas such as the European shelf around the British Isles
,
the Patagonian shelf off Argentina
, and the
Bering Sea
.
Many lines
of
evidence indicate that the continents
and
oceans used to be arranged differently
,{{ref|
{{author|Ron|Blakey}}
, [http://
cpgeosystems
.com/
mollglobe
.html
Mollewide Plate Tectonic Maps
]
.
}}
but knowledge
of
those arrangements is too limited to say
with
any confidence how great
the
tidal dissipation was
.
It could easily have
been
a few times larger or smaller than it is today
.
Calculations show that configurations with fewer continents, especially if there are no continents oriented north-south as North
and
South America or Europe and Africa are now
,
have much less tidal braking
,
so
the
presently observed tidal acceleration may be near the high end
of the
historical range
.
−
A figure
,
derived from three independent values
,
that has passed a test for internal self-consistency through application of
the
laws
of
celestial mechanics is 401 sidereal days/year in upper pre-Cambrian deposits.
+
−
{{ref|George E. Williams, [http://onlinelibrary.wiley.com/doi/10.1029/97GL00234/abstract Precambrian length of day and
the
validity of tidal rhythmite paleotidal values]
.
''Geophysical Research Letters'', Volume 24, Issue 4, pages 421–424, 15 February 1997. NATURE, March 9, 1963.}}
+
−
If these periodicites are correctly interpreted
as
indicating
the number of days in a year
at the time the deposits were laid down
,
then
the number of days in a year
was significantly greater
in
the geologic past
.
+
Orbital parameters such
as the number of days in a year, the number of days
in a month, and the number of months
in a year
, can be found imprinted
in
a number of natural systems
.
−
If the
Earth
has slowed down
,
then it must have lost angular momentum to
the
Moon through
tidal
dissipation
,
but this would have taken hundreds
of
millions of years
.
+
* Tidal rhythmites{{ref|Rajat Mazumder and Makoto Arima, [http://www.mantleplumes.org/WebDocuments/MazumderESR2004.pdf Tidal rhythmites and their implications], ''
Earth
-Science Reviews'' '''69''' (2005) 79–95}}{{ref|George E. Williams
,
[http://onlinelibrary.wiley.com/doi/10.1029/97GL00234/abstract Precambrian length of day and
the
validity of
tidal
rhythmite paleotidal values]. ''Geophysical Research Letters''
,
Volume 24, Issue 4, pages 421–424, 15 February 1997. NATURE, March 9, 1963.}} are alternating layers
of
sand and silt laid down offshore from estuaries having great tidal flows
.
−
However
,
the rhythmite dating is questionable
and
assumes
the
secular age
for the Earth, and
as such
the
argument amounts to circular reasoning
.{{ref|
Henry, Jonathan
, [http://
creation
.com/the-
moons
-
recession
-
and
-
age
The
moon’s recession
and
age]
,
''Journal
of
Creation''
,
20(2):65–70
,
August 2006}}
+
* Living creatures including corals, shells
, and
stromatolites exhibit growth bands influenced by daily, monthly, and yearly cycles.{{ref|JOHN W. WELLS, [http://freepages.genealogy.rootsweb.ancestry.com/~springport/geology/coral_growth.html CORAL GROWTH AND GEOCHRONOMETRY]}}
+
+
All of these natural systems can also be found in deposits at various depths in
the
geological column. For example, the upper pre-Cambrian Elatina-Reynella rhythmites in South Australia have been identified as having periodicities giving independent values
for
three different parameters of
the Earth
-Moon system: 14.1 sidereal months/year, 401 sidereal days/year
, and
19.5 years for
the
lunar nodal period
.{{ref|
George E. Williams
, [http://
onlinelibrary.wiley
.com/
doi/10.1029/97GL00234/abstract Precambrian length of day and
the
validity of tidal rhythmite paleotidal values]. ''Geophysical Research Letters'', Volume 24, Issue 4, pages 421–424, 15 February 1997. NATURE, March 9, 1963.}} These values are internally self
-
consistent when evaluated in the light of the laws of celestial mechanics, namely they all indicate a lunar distance in the range of 96.5–96.9%, or 3.7% smaller than the present figure. <!
---
It would be interesting at this point to include the mathematics relating the number of months per year to the number of days per year, but I need to work on a slightly bigger napkin.--->
The
lunar distance is currently 384,000 km
and
increasing at 3.8 cm per year
,
which is a fractional change
of
10<sup>-10</sup> per year. At that rate
,
370 million years would be required to change the distance by the amount implied by the Elatina-Reynella rhythmites.
+
+
Secular scientists see this result as evidence that these rhythmites were deposited hundreds of millions of years ago. The particular value of 370 million years is 40% lower than the value of 620 million years determined by [[radioactive dating]]
,
a discrepancy that lies easily within the uncertainties related to the configuration of the oceans.
==Human exploration==
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