reply to post by mikem
The recent most accept theory of how the moon came to be, is the impact theory. It goes like this:
Around 4 billion years ago, the inner solar system was comprised of a LOT of rocky planets, many in orbits that ended up flinging them out of our
system, or into the sun. One of these planets was in a orbit that intersected the Earths. It was about the same size as Mars. They've even given it a
It impacted with the Earth at an angle. This turned the entire planet molten of course and just about destroyed the Earth, it did completely shatter
Theia. The remains of which swung around and impacted again (the core remains) and sank into the Earth.
The cores of rocky planets contain the heavier elements. The remaining debris formed the moon.
This even caused the earth to be knocked on it's axis at just over 23 degrees and sped up our rotation to about 6 hours for a day. The moon formed
very close to the Earth, and began it's tidal friction with us.
It's this friction that eventually slowed the Earth down to it's current rotation period and is also what is helping push the moon away from us (the
moon is receeding from us at like 3 inches per year). Don't worry, we won't loose the moon. The sun will become a red giant before that happens,
consuming the Earth several billion years from now.
Now this is all theory, but fits all models, and computer simulations show that it was quite possible. Other theories (such as the capture theory or
the moon forming on it's own next to Earth, do not quite work out with computer models), still the only way to prove it 100 percent would be to have
a time machine and go back to the event.
The majority of the debris that made the moon were absorbed by both the moon and the Earth, billions of years before the dino's were on the scene.
To change the amount of gravity of the Earth, you would have to remove or add a extremely LARGE amount of mass from our planet. While we do have
meteors and solar dust coming to earth, even if you add up that tons and tons of debris, it's still a drop in the bucket. Remember, the dinos were
gone just 65 million years ago, so in order for the theory to be correct, the Earth would have had to have a MASSIVE amount of material added to it in
just that 65 million years and there is no evidence of that.
Look at Venus, it's only slightly smaller than us, and you'd still weigh 90 percent of what you weigh now.
Around 300 million years ago, the Earth had plants and bugs that were giant. Spiders the size of your head, dragonflies the size of eagles, and
centipies the size of a small car. The Earth's atmosphere at that time had an oxygen content of about 32 percent, unlike the 21 percent we have now.
Higher oxygen content promotes larger growth in biology.
By the time the dinos showed up, that oxygen content had gone down, and was closer to what we have now (not exactly, but lower than that 32 percent).
However, the Earth's climate supported large areas of plant life.
Go out and get a fish tank that's 10 gallons. Put an Oscar fish in it and keep it for about 6 months. Note it's size. Now go out and get a much
bigger tank (30, 40 or 50 gallon) and put a new Oscar fish in it (but not too many other fish, the more room the better), and watch how big that one
gets! It's not the gravity, but the environment.
It is true that if you have biology working in very low gravity, it can get bigger, but the Earth's gravity has not changed that much since it formed
after the moon impact. On the moon you'd only weigh 1/6 of what you do here, but the moon is much smaller than us, at only 1/4 the size. So small
that it can't hold on to a atmosphere.
And there's your kicker: if gravity was that week back then, our atmosphere would have ended up being like Mars by now: very thin.