reply to post by seagull
seagull....good points....about the laser reflectors, I forgot to mention those!!!
Here's an interesting tidbit I recently saw, on the Science Channel (Dish Network Satellite)...based on, now, 39 years of measurements....the Moon is
slowly spiralling away, as it orbits the Earth. This amounts to a few centimeters every decade, or so....but it seems that A) If we assume this
continues, the Moon will eventually leave the gravitational pull of the Earth, and become a rogue. This, of course, well after you and I are
dead....in fact, this will take another two billion years, give or take ten million....
B)....extrapolating backwards, it tends to lend credence to the theory of how the Moon was formed, in the first place. A chance collision, in the
early formation of the Solar System....when the barely forming Earth was struck by a large mass, and ejecta was....well....ejected. Enough of the
lighter material of the early Earth was blown out, and eventually congealed, to become our Moon....after about two billion years....but, this nascent
Moon was much nearer, then....it has been gradually spiralling away since then....for instance, if we could go back in time 900,000,000 years, it
would seem larger in the sky than it does now, in 'modern' times.
Hence, its influence, gravitationally, would have been greater....the combined effects could have led to a slowing of both bodies' rotational
periods....the smaller body, the Moon, becoming gravitationally 'locked' with its 'parent' planet....Earth. Each influencing the other, as
gravity inevitably slowed them both, to equilibrium....which we see today.
This, over hundreds of millions....or even billions of years....gradually resulting in a unique (in our Solar System) almost double-planet system.
No other planet, in our System, has a natural satellite that is equivalent in mass and ratio to its parent, as the Earth-Moon system.
This has tremendous bearing on the potential for a stable environment, here on Earth....it is a theory that, maybe, a stable 'Earth-like'
environment needs a Moon....a fairly close Moon....to stabilize the 'parent' planet.
Venus, for instance, has no Moon....and Venus does not rotate like the Earth....It has a very, very slow rotation period, compared to our planet.
Venus rotates once about its axis every 243 Earth days....its orbit around the Sun is about every 225 earth days....so it is not tidally locked to the
Sun....but its slow rotation might possibly account for its inhospitable surface temperatue of over 800 degrees.
Venus is, technically, in the 'habital zone'....meaning, it's distance from the Sun isn't certain death, to humans. It just, for some reason, had
Global Warming to the MAX!!!
Mars, a bit farther out, is smaller than Earth....may have lost her magnetic field, thus her atmosphere billions of years ago....but most certainly,
there was life there, at one time....and a little more mass, or a different composition of the planet....and there would be a thicker atmosphere
today, and multicellular life, as well.
Still, Mars is in the 'habital zone'.....
Given different circumstances, Venus, alhough slightly closer to the Sun, could have, since she is about the same size as Earth, been a harborer of
life. Maybe it was so, a billion years ago?
Same with Mars....a Billion years ago...could have had life. I'm not saying intelligent, techinically advanced life!
Yet, here we are, able to contemplate...and study, and learn....and eventually, go out to study and learn more, as we did on the Moon, with robots,
and eventually with Men, and to Mars, with robots....and maybe Men....and Venus, robot so far, mostly Russian.....(not likely to send men)