by Alohascope » Tue Dec 08, 2015 2:05 am
neufer wrote:
The accurately measured constancy of the
sidereal year = 31,558,149.504 seconds
& the balanced tidal transference of energy & angular momentum from the Earth to the Moon
is perfectly consistent with:
- 1) a constant gravitational constant with
2) no noticeable mechanical work being performed by dark energy.
Such measurements put limits on the ability of dark energy to tear apart bound systems
such as the Sun & Earth or the Earth & Moon anytime soon.
https://en.wikipedia.org/wiki/Tidal_acceleration wrote:
<<The motion of the Moon can be followed with an accuracy of a few centimeters by lunar laser ranging (LLR). Laser pulses are bounced off mirrors on the surface of the moon, emplaced during the Apollo missions of 1969 to 1972 and by Lunokhod 2 in 1973. Measuring the return time of the pulse yields a very accurate measure of the distance. These measurements are fitted to the equations of motion. This yields numerical values for the Moon's secular deceleration, i.e. negative acceleration, in longitude and the rate of change of the semimajor axis of the Earth–Moon ellipse. From the period 1970–2012, the results are:
−25.82±0.03 arcsecond/century2 in ecliptic longitude
+38.08±0.04 mm/yr in the mean Earth–Moon distance
This is consistent with results from satellite laser ranging (SLR), a similar technique applied to artificial satellites orbiting Earth, which yields a model for the gravitational field of Earth, including that of the tides. The model accurately predicts the changes in the motion of the Moon.
Finally, ancient observations of solar eclipses give fairly accurate positions for the Moon at those moments. Studies of these observations give results consistent with the value quoted above.
The other consequence of tidal acceleration is the deceleration of the rotation of Earth.
From the observed change in the Moon's orbit, the corresponding change in the length of the day can be computed:
+2.3 ms/century
However, from historical records over the past 2700 years the following average value is found:
+1.70 ± 0.05 ms/century
Opposing the tidal deceleration of Earth is a mechanism that is in fact accelerating the rotation. Earth is not a sphere, but rather an ellipsoid that is flattened at the poles. SLR has shown that this flattening is decreasing. The explanation is that during the ice age large masses of ice collected at the poles, and depressed the underlying rocks. The ice mass started disappearing over 10000 years ago, but Earth's crust is still not in hydrostatic equilibrium and is still rebounding (the relaxation time is estimated to be about 4000 years). As a consequence, the polar diameter of Earth increases, and because the mass and density remain the same, the volume remains the same; therefore the equatorial diameter is decreasing. As a consequence, mass moves closer to the rotation axis of Earth. This means that its moment of inertia is decreasing. Because its total angular momentum remains the same during this process, the rotation rate increases. This is the well-known phenomenon of a spinning figure skater who spins ever faster as she retracts her arms. From the observed change in the moment of inertia the acceleration of rotation can be computed: the average value over the historical period must have been about −0.6 ms/century. This largely explains the historical observations.>>
Well Art what do I know besides what 'they' (John Hopkins and NASA.)tell me? 'The Hubble Site.'
"With dark energy, the fate of the universe might go well beyond the Big Chill. In the strangest and most speculative scenario, as the universe expands ever faster, all of gravity's work will be undone. Clusters of galaxies will disband and separate. Then galaxies themselves will be torn apart. The solar system, stars, planets, and even molecules and atoms could be shredded by the ever-faster expansion. The universe that was born in a violent expansion could end with an even more violent expansion called the Big Rip."
This from a site called 'The Hubble Site'
http://hubblesite.org/hubble_discoverie ... iverse.php
"A free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA."
http://www.stsci.edu/institute/[quote="neufer"][quote="Alohascope"]
http://www.universetoday.com/107316/what-is-the-big-rip/
http://www.adrianberry.net/art54.htm
It appears the universe may expand itself to death, like stretching a rubber band until it snaps.[/quote]
The accurately measured constancy of the [url=https://en.wikipedia.org/wiki/Sidereal_year]sidereal year[/url] = 31,558,149.504 seconds
& the balanced tidal transference of energy & angular momentum from the Earth to the Moon
is perfectly consistent with:
[list]1) a constant gravitational constant with
2) no noticeable mechanical work being performed by dark energy.[/list]
Such measurements put limits on the ability of dark energy to tear apart bound systems
such as the Sun & Earth or the Earth & Moon anytime soon.
[quote=" https://en.wikipedia.org/wiki/Tidal_acceleration"]
<<The motion of the Moon can be followed with an accuracy of a few centimeters by lunar laser ranging (LLR). Laser pulses are bounced off mirrors on the surface of the moon, emplaced during the Apollo missions of 1969 to 1972 and by Lunokhod 2 in 1973. Measuring the return time of the pulse yields a very accurate measure of the distance. These measurements are fitted to the equations of motion. This yields numerical values for the Moon's secular deceleration, i.e. negative acceleration, in longitude and the rate of change of the semimajor axis of the Earth–Moon ellipse. From the period 1970–2012, the results are:
−25.82±0.03 arcsecond/century2 in ecliptic longitude
+38.08±0.04 mm/yr in the mean Earth–Moon distance
This is consistent with results from satellite laser ranging (SLR), a similar technique applied to artificial satellites orbiting Earth, which yields a model for the gravitational field of Earth, including that of the tides. The model accurately predicts the changes in the motion of the Moon.
Finally, ancient observations of solar eclipses give fairly accurate positions for the Moon at those moments. Studies of these observations give results consistent with the value quoted above.
The other consequence of tidal acceleration is the deceleration of the rotation of Earth.
From the observed change in the Moon's orbit, the corresponding change in the length of the day can be computed:
+2.3 ms/century
However, from historical records over the past 2700 years the following average value is found:
+1.70 ± 0.05 ms/century
Opposing the tidal deceleration of Earth is a mechanism that is in fact accelerating the rotation. Earth is not a sphere, but rather an ellipsoid that is flattened at the poles. SLR has shown that this flattening is decreasing. The explanation is that during the ice age large masses of ice collected at the poles, and depressed the underlying rocks. The ice mass started disappearing over 10000 years ago, but Earth's crust is still not in hydrostatic equilibrium and is still rebounding (the relaxation time is estimated to be about 4000 years). As a consequence, the polar diameter of Earth increases, and because the mass and density remain the same, the volume remains the same; therefore the equatorial diameter is decreasing. As a consequence, mass moves closer to the rotation axis of Earth. This means that its moment of inertia is decreasing. Because its total angular momentum remains the same during this process, the rotation rate increases. This is the well-known phenomenon of a spinning figure skater who spins ever faster as she retracts her arms. From the observed change in the moment of inertia the acceleration of rotation can be computed: the average value over the historical period must have been about −0.6 ms/century. This largely explains the historical observations.>>[/quote][/quote]
Well Art what do I know besides what 'they' (John Hopkins and NASA.)tell me? 'The Hubble Site.'
"With dark energy, the fate of the universe might go well beyond the Big Chill. In the strangest and most speculative scenario, as the universe expands ever faster, all of gravity's work will be undone. Clusters of galaxies will disband and separate. Then galaxies themselves will be torn apart. The solar system, stars, planets, and even molecules and atoms could be shredded by the ever-faster expansion. The universe that was born in a violent expansion could end with an even more violent expansion called the Big Rip."
This from a site called 'The Hubble Site'
http://hubblesite.org/hubble_discoveries/dark_energy/de-fate_of_the_universe.php
"A free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA."
http://www.stsci.edu/institute/