"Double-A" wrote in message
oups.com...

John Zinni wrote:
"beav" wrote in message
...
On Sun, 11 Dec 2005 10:12:55 -0500, "John Zinni"
wrote:

"Ryan Evans" wrote in message
...
Do we always see the same side of the moon, or does it slowly rotate
in relation to our view?

To me, it seems quite a cooincidence that the moon rotates perfectly
such that we see the same side constantly.

RE

No coincidence. In fact it's quite common.

It's called 1-to-1 spin-orbit resonance.


"Most of the moons in the solar system are similarly locked by the
tidal
fields of their parent planets."
http://physics.fortlewis.edu/Astrono...ML/AT30803.HTM

"All the large moons in our Solar System are in 1:1 spin-orbit
resonances:
Those moons always show the same side to the planet, just like our Moon
does
relative to the Earth."
http://www.astro.uu.nl/~strous/AA/en...rtekracht.html


Question: What major solar system object is locked into a spin-orbit
resonance with its primary that is other than 1-to-1?


answer neptune and pluto?

actually, you could include any asteroid or KBO at the respective
Langrange regions away from any planet, especially the ones at 2:3 and
2:5 resonances...

BZZZZZZZZT! Sorry wrong answer.

(Actually, I think you may be thinking of a different kind of resonance
(orbit-orbit). My question was specifically about spin-orbit resonance -
rotations of the secondary in relation to orbits of the primary)




me? i've personally revoked pluto's license to be a planet...



"It [Mercury] is in a gravitational resonance, but one in which its
axial rotation period is about 58.6 Earth days, or two thirds of its
orbital rotation period."

http://www.daviddarling.info/encyclo...ercuryrot.html

Double-A

Give that man a Cupie-Doll!!!

Yes it's Mercury that is captured into a 3:2 spin-orbit resonance around the
Sun (rotating three times for every two revolutions around the Sun).

Contributing factors in allowing this 3:2 spin-orbit resonance to be stable
are Mercury's permanent bulge and its orbital eccentricity.