Gravity, Earth and the Moon

I want to say thankyou for all the post first... I think this is a cool topic

I apologize on what I don't know.

So what I thought was that the earth is made up of layers.. crust, mantle, core... there may be more these days but school has been long past me.

The core is made of the most dense material, and the crust is the thinest lightest part of the earth. Doesn't this mean that there is more mass in the dense compacted core and more mass controls the gravity.

As for the dinosaurs they wouldn't be able to live on earth today.. elephants are getting smaller and smaller and even now if they lay down for two long they can die...

So what if the earth use to be bigger... having more of the less dense crust and having a very large core..

The moon for our earth is abnormally big for our size little planet.

They theorize that the earth was hit by a huge asteriod or other celestial creating the moon.

Now say the Earth was hit and a chunk of the earth was blasted into space... there would be a hole in the crust.. like a bite out of an apple... water would fill the void and then slowly the earths crust would shift and move to fill the void.. making our continents move pulling apart.

Then wouldn't the Earths core of heavy dense material still be there... the small amount of light debris is gone... so gravity wouldn't be less and the outer crust would be closer to the core..

Wouldn't this make the gravity on earth be heavier.


As for the earth growing 1in a year... thats not a fact or quote just something someone else posted earlier on another thread. I'm sorry I should have stated that.

I wait with interest from your post.

m

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 name: Theia.

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.

During the period when dinosaurs roamed Pangea, the Earth's surface gravity was much less than it is today. This is explained in a new theory which can be viewed at www.dinoextinct.com. Click on 'The Gravity Theory Of Mass Extinction' to view the PDF summary of the theory.