Moon showing only one side?

reply to post by weedev

I know how it works! but why and if its it's common?

The best explanation is the Law of Conservation Of Angular Momentum.

The mutual gravitational attractive forces act to transfer energy...the kinetic energy of motion, and momentum.

Billions of years ago the Moon was much closer to the Earth, the Earth was rotating much faster, and so was the Moon.

The impetus of the formation of the Moon left it with enough speed (energy) in its orbit that it continues to pull away each time...that rate isn't constant over great lengths of time, it is slowing. Currently it averages about 2.8 centimeters per year. This is known because of the laser reflective ranging surface experiments left by Apollo on the Lunar surface.

The energy the Moon uses to orbit a little bit 'higher' each time robs the Earth of some angular momentum....just as the Earth robs the Moon. Because of the difference in size and mass, the Earth wins most of the battle. Hence, what we now see today as "tidal locking"...the 'tidal' refers to the gravitational forces interacting between the two bodies. This is why we refer to the ocean's movements as "tides".

For Humans, and our lifespans, the differences are not apparent, and hardly measurable. Takes millions of years to see big changes.

edit: Don't know if I can improve on LAUGHING-CAT's explanation!

But for the conservation of angular momentum, you can see that at work in an ice skater, when she twirls. Spreading arms out, speed of rotation slows down, bring arms in close to body, person speeds up rotation.






[edit on 17 July 2009 by weedwhacker]

Could the fact that the near side is larger than the far side be a reason why it is locked in it's current position? (more surface area = greater pull toward Earth?)

reply to post by weedwhacker

Thanks for the attribution, I can get simpler, but as my employer says, "Mike, If you treat them like children, they will be children".

reply to post by Mars007


I don't believe the near side is 'larger'....in fact, there appear to be some localized mass anomalies on the far side!!!

They've been dubbed 'mascons', for "mass concentrations". They aren't massive enough to afect the entire planet...just as the Alps here on Earth, although very massive, don't have much influence other than on weather patterns and such.

I was curious as to the tidal locking for a bit and here's a much simpler explained version..

We have tides -- the tides are because of the gravitational pull of the moon.

The moon was also being pulled and stretched. During that time period the moon had volcanoes because the stress the Earth was putting on it was immense.

As time goes by, the spinning slows down and it finally stops. Just like if you sit a bike upside down, spin the wheel and when it comes ALMOST to a rest, the wheel will most likely rotate back and forth real slow a few times.

The moon did this for a long time... or did it ?
------------------

Not many people know about the tidal locking Venus has with the Earth and I have to admit that this is a VERY strange anomaly. I spent the time to research the formula once and the one given came out to be a period of time that was BILLIONS of years past the supposed "big bang" time frame.

On a crazy thought level, if a species COULD stp a planets rotation enough to become tidally locked to the Earth, the only reason why I could see that being needed is for a "line of site" transfer of objects or things. Like a radar dish pointing to another radar dish.

Also, the supposed "slowing of the Earth and Moon" formula goes way past the Big Bang theory as well. But who are we to know anything like that really? To us it's gravitation.
To others gravitation isn't what is commonly taught and the internal structure of the moon may be of a substance that has a stronger magnetic draw to the Earth's content.

Same for Venus. If gravity is NOT based on mass but rather the ELEMENTS of the mass, then Venus would have a different valid reason for being tidally locked to the Earth that we don't understand yet...

There's my "outlandish thoughts of the week" for everyone to read

b

dunno if anyone posted this already, I dont have time to read all the way through...so here ya go from wiki

"Tidal locking occurs when the gravitational gradient makes one side of an astronomical body always face another; for example, one side of the Earth's Moon always faces the Earth. A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner. This synchronous rotation causes one hemisphere constantly to face the partner body. Usually, only the satellite becomes tidally locked around the larger planet, but if the difference in mass between the two bodies and their physical separation is small, both may become tidally locked to the other, as is the case between Pluto and Charon. This effect is employed to stabilize some artificial satellites."

reply to post by Bspiracy

Not many people know about the tidal locking Venus has with the Earth and I have to admit that this is a VERY strange anomaly.

Bs, Venus is NOT 'tidally locked' with the Earth!!!
Sorry, but your research needs to be re-examined.
Besides...the dynamics of the two planets' orbits would preclude any "tidal locking" between the two!!!

Orbital characteristics

Aphelion 108,942,109 km
0.728 231 28 AU
Perihelion 107,476,259 km
0.718 432 70 AU
Semi-major axis 108,208,930 km
0.723 332 AU
Eccentricity 0.006 8
Orbital period 224.700 69 day
0.615 197 0 yr
Synodic period 583.92 days
Average orbital speed 35.02 km/s
Inclination 3.394 71° to Ecliptic
3.86° to Sun’s equator
2.19° to Invariable plane
Longitude of ascending node 76.670 69°
Argument of perihelion 54.852 29°
Satellites None

Physical characteristics

Mean radius 6,051.8 ± 1.0 km[3]
0.949 9 Earths
Flattening < 0.000 2[3]
Surface area 4.60 × 108 km²
0.902 Earths
Volume 9.38 × 1011 km³
0.857 Earths
Mass 4.868 5 × 1024 kg
0.815 Earths
Mean density 5.204 g/cm³
Equatorial surface gravity 8.87 m/s2
0.904 g
Escape velocity 10.46 km/s
Sidereal rotation
period 243.018 5 day
Equatorial rotation velocity 6.52 km/h (1.81 m/s)
Axial tilt 177.3°

en.wikipedia.org...

THIS is important to note!!! Venus is askew, relative to the Earth!!!


Earth's axial tilt:

Equatorial rotation velocity 1,674.4 km/h (465.1 m/s)
Axial tilt 23.439281°

en.wikipedia.org...



[edit on 18 July 2009 by weedwhacker]

hmm. interesting thread, i need to pay more attention

Well thanks all! Got a few good views going on there...

Originally posted by LAUGHING-CAT
reply to post by weedwhacker

 

Thanks for the attribution, I can get simpler, but as my employer says, "Mike, If you treat them like children, they will be children".

reply to post by LAUGHING-CAT

Anyway, that's how I finally "got it".

I have a better one, been saving it.

Picture looking down from above the North Pole, at the Earth/Moon

NOW, imagine a disc (like an old-fashioned vnyl LP) and the Earth is in the center of the disc. Tape a coin to the outer edge. Have one light source to represent the Sun.

As you rotate the disc, you will see the coin (representing the Moon) will rotate relative to the room, and the light source, but not the center (Earth).

Of course, the Moon isn't "taped" down, but this just demonstrates how rotation is relative to the observer's location.

Originally posted by Bspiracy


As time goes by, the spinning slows down and it finally stops. Just like if you sit a bike upside down, spin the wheel and when it comes ALMOST to a rest, the wheel will most likely rotate back and forth real slow a few times.

The moon did this for a long time... or did it ?
------------------


b

Thanks!