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The Giant Impact Theory  (Source:
Two new studies attempt to prove the Giant Impact Theory in different ways

Two different studies say they've found evidence supporting the theory that the moon was created from a collision between Earth and a Mars-sized body.

The Giant Impact Theory, which was proposed back in 1975, suggests that the early Earth and a Mars-sized planet called Theia collided with one another. This completely obliterated Theia, and its composition created a ring around Earth and eventually came together to create the moon.

While scientists have been able to explain how this event occurred, one major thing didn't add up: the composition of the moon.

Scientists long believed that for this theory to be true, the moon would have to be composed mainly of Theia's elements. Moon rocks from that were brought to Earth were studied, and surprisingly, they had the same types and amounts of elements that the Earth had, including titanium, silicon and oxygen. This didn't make sense, and has left the theory wide open for the last 30+ years.

However, scientists from Washington University in St. Louis managed to measure a small excess of a heavier variant of zinc in moon rocks from that were brought to Earth in the 1970s. They believe the excess is due to heavier zinc atoms condensing out of the collision's cloud faster than the lighter zinc atoms, and the vapor that remained escaped before it condensed.

This bit of sorting by mass is called isotopic fractionation, and it's what scientists have been looking for all along. This shows that the moon rocks were depleted of easily evaporated elements called volatiles, and a large collision could explain this depletion while other theories can't.

"The magnitude of the fractionation we measured in lunar rocks is 10 times larger than what we see in terrestrial and Martian rocks," said Frédéric Moynier, PhD, from Washington University in St. Louis. "So it's an important difference."

But the Washington University team isn't the only one to bring new evidence to the table. Robin Canup, a planetary scientist from the Southwest Research Institute Colorado, used Harvard scientists' findings to create a theory of her own related to the collision.

According to the Harvard team, which used computer simulations to create its theory, ancient Earth had to have been spinning too fast for today's 24-hour rotation. They suggested that early Earth and a body half the size of Mars could have collided where both were obliterated and combined elements to create both the moon and Earth's heavy iron core/lighter rock layers.

At a later point, Earth's rotation could have slowed due to the moon and sun aligning in a way that changed Earth's orbit.

Canup used the idea that Earth's rotation was slowed and came up with the theory that two bodies similar in size collided at a slow speed, and their materials merged to create the Earth and moon.

Source: Science Daily

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By Goty on 10/20/2012 11:46:40 AM , Rating: 5
This isn't in any way a new idea. I've been telling this exact same story (including the complete destruction of Earth and Theia) to my astronomy students for years.


At a later point, Earth's rotation could have slowed due to the moon and sun aligning in a way that changed Earth's orbit.

Yeah, no. The shape and size of the orbit have nothing to do with the rotational period of the Earth. The effect you want is called tidal braking and it doesn't have anything to do with the alignment of the Earth, Sun, and Moon, either, it only requires that you have orbiting bodies with dissimilar rotational periods.

I understand that you probably have a quota on articles to write, but you really need to understand the material before you write, first.

RE: *sigh*
By DanNeely on 10/20/2012 2:15:52 PM , Rating: 2
From better quality reporting I saw a week ago; what's new is that researchers have found an additional mechanism to drain angular momentum from the Earth-Moon system. As a result the proto-Earth could have been spinning faster when it was hit than previously believed. One of recent paper used the higher initial spin rate to get a more thorough mixing of the protoplanets mantles needed in order for the Earth-Moon isotope ratios to match as closely as they do. A second paper by a different group accomplished the same by colliding two protoplanets of approximately equal sizes.

I don't recall where I first read it. lists the names of the authors and the Journals they were published in so you (or anyone else was access) could read the actual papers being mangled here; and its article mentions everything I did except the additional spindown mechanism.

RE: *sigh*
By ET on 10/22/2012 7:35:14 AM , Rating: 2
Thanks. This makes more sense.

RE: *sigh*
By vol7ron on 10/20/2012 2:27:48 PM , Rating: 1
This isn't in any way a new idea. I've been telling this exact same story (including the complete destruction of Earth and Theia) to my astronomy students for years.

I hope you address it as that, a theory

RE: *sigh*
By Goty on 10/20/2012 3:00:11 PM , Rating: 3
Of course it's a theory. So is Newton's law of gravity, so is relativity. I don't think you really know the scientific meaning of the word.

RE: *sigh*
By Samus on 10/20/2012 10:09:23 PM , Rating: 1
Na, it's not a theory man. I was there when it happened, MAN.

RE: *sigh*
By wordsworm on 10/21/2012 11:58:26 AM , Rating: 1
The law of gravity is not a theory. It's a law. Relativity is a theory, which is why it's called the theory of relativity.

RE: *sigh*
By Goty on 10/21/2012 12:39:30 PM , Rating: 2
I'll go ahead an lump you in the group with the other guy. I guess gravity being a "law" explains why breaks down in regimes where relativity still functions and why relativity can predict things that Newton's law of gravity cannot (like the precession of Mercury's orbit or the bending of light around massive objects)? Yeah, that must be it.

If you know so little about the subject as to not even recognize that general relativity is a replacement and extension of Newton's law of gravity, you really shouldn't be commenting in this thread.

RE: *sigh*
By StormyKnight on 10/23/2012 1:01:55 AM , Rating: 2

RE: *sigh*
By delphinus100 on 10/21/2012 12:45:59 PM , Rating: 2
But that 'law' only describes what gravity does, not what it is.

Laypeople tend to use the word 'theory' in the way scientists use the word 'hypothesis.' One poses a hypothesis, tests it with experiment and/or observation, and theories are built on, or modified by, or invalidated by the results of those experiments or observations.

And no, we don't yet fully understand the actual nature of gravity, mostly because we can't yet reconcile General Relativity and Quantum Mechanics (both well-supported theories that describe certain aspects of the Universe in different, inconsistent ways) into a single theory.

RE: *sigh*
By KPOM1 on 10/21/2012 12:46:07 PM , Rating: 2
Is it a theory or a hypothesis?

RE: *sigh*
By Goty on 10/21/2012 2:36:30 PM , Rating: 3
Theory. General relativity has been rigorously tested and no contradictions have yet been observed.

RE: *sigh*
By JNo on 10/21/12, Rating: -1
RE: *sigh*
By Goty on 10/21/2012 11:44:49 PM , Rating: 5
Actually, none of these theories have been proven. That's the crux; to be scientific a hypothesis must be disprovable, so absolute proof is unobtainable.

As to the rest of your self-righteous ranting, since when is it wrong to expect a journalist to inform themselves on a subject before publishing or to exhibit self-control in abstaining from adding extraneous, made-up statements to an article instead of making a five minute visit to Wikipedia beforehand? Laziness is not an excuse for poor writing.

RE: *sigh*
By retrospooty on 10/20/2012 9:03:13 PM , Rating: 2
"This isn't in any way a new idea. I've been telling this exact same story (including the complete destruction of Earth and Theia) to my astronomy students for years."

Exactly... I have seen this all over the science channel for at least the last decade. Anything but new. Cool , but not new.

RE: *sigh*
By ShaolinSoccer on 10/21/2012 11:13:50 PM , Rating: 2
Kind of like Reddit. They recycle "old" stuff there constantly and get tons of upvotes for it... Gotta love teenagers...

RE: *sigh*
By Chemical Chris on 10/20/2012 10:04:06 PM , Rating: 2
I wish I still had it, but my grandfather (retired librarian) had a book from the late 1800's about astronomy. In it, it said that they once thought the moon was formed from a collision between two objects a long time ago (as we now believe); but that that theory had been discarded as nonsense and the earth instead trapped the moon by its gravity.
I love how the state of 'truth' changes over time!
(thats a good thing, btw, changing ones opinion based on new evidence/facts)

RE: *sigh*
By Goty on 10/21/2012 12:41:08 PM , Rating: 2
That would be awesome to have. The big difference between now and then (and why I'd say our claims today are much stronger) is that we have evidence of the composition of each body, whose similarity is best explained by the giant impact hypothesis.

RE: *sigh*
By maugrimtr on 10/22/2012 8:52:56 AM , Rating: 3
The "truth" doesn't change. All we have are hypothetical scenarios that could lead to the formation of the moon we have. The trick is finding one which fits all the observations and known composition of the moon so it graduate a little bit closer to "truth".

So the article above is a bit of a mess. We've known about the broad strokes for many decades - either we captured the moon or it formed in orbit from Earth debris, i.e. most likely from a collision with another planet. Capture seems improbable so collision is not the frontrunner. The new information provides a scenario where we end up with a moon closer to the composition we expect - that's why it's big news.

RE: *sigh*
By kattanna on 10/22/2012 10:56:07 AM , Rating: 2
I understand that you probably have a quota on articles to write, but you really need to understand the material before you write, first

sadly.. that statement can be made to much of what passes for "journalism" these days

I did it
By hiscross on 10/20/2012 2:55:12 PM , Rating: 2


RE: I did it
By Motoman on 10/21/12, Rating: -1
RE: I did it
By Asetha on 10/21/2012 9:20:34 AM , Rating: 2
Why waste the keystrokes?

RE: I did it
By Motoman on 10/21/2012 5:03:16 PM , Rating: 2
Stupid should hurt. If everyone tolerates the stupidity of those around them, they don't know they're being stupid and they just continue being stupid.

If you at least make fun of them, they'll maybe someday realize that they're stupid, and do something about it.

RE: I did it
By Asetha on 10/22/2012 2:48:17 AM , Rating: 2
Actually people who are made fun of usually retrench.

Second, I think it's kind of stupid to make fun of something you don't think exists.

RE: I did it
By Motoman on 10/22/2012 9:03:18 AM , Rating: 2
I'm not making fun of the thing that doesn't exist...I'm making fun of people who insist on believing it does exist. And that it controls everything that happens in the universe.

If you want to teach your kids that Santa Claus brings presents every Christmas, that's long as you let them in on the joke eventually. Religious people are in effect nothing more than children who never caught on to the fact that Santa Claus doesn't actually exist, and who wind up spending their whole lives believing in him.

RE: I did it
By hiscross on 10/21/2012 4:48:43 PM , Rating: 1
BTW: I made you. Do you wish I change my mind, like right now?

RE: I did it
By Motoman on 10/21/2012 5:02:15 PM , Rating: 1
Go ahead and try. I'll wait.

BTW: nice "Christian" attitude there, loser. XD

RE: I did it
By FITCamaro on 10/22/2012 7:26:54 AM , Rating: 3
Says the guy throwing out cuss words like they're on sale.

And God doesn't have to explain himself to you or anyone else.


RE: I did it
By FITCamaro on 10/22/2012 7:30:53 AM , Rating: 2
And blaming God for the failures of man is like Obama blaming Mitt Romney for there being poor people in this country.

RE: I did it
By Motoman on 10/22/2012 9:07:30 AM , Rating: 2
"God" is a failure of man.

RE: I did it
By Florinator on 10/22/2012 3:45:57 PM , Rating: 2
One of my most favorites quotes ever, belongs to Gore Vidal:

The great unmentionable evil at the center of our culture is monotheism. From a barbaric Bronze Age text known as the Old Testament, three anti-human religions have evolved — Judaism, Christianity, Islam. These are sky-god religions. They are, literally, patriarchal — God is the Omnipotent Father — hence the loathing of women for 2,000 years in those countries afflicted by the sky-god and his earthly male delegates. The sky-god is a jealous god, of course. He requires total obedience from everyone on earth, as he is in place not for just one tribe but for all creation. Those who would reject him must be converted or killed for their own good. Ultimately, totalitarianism is the only sort of politics that can truly serve the sky-god's purpose.

RE: I did it
By FITCamaro on 10/22/2012 4:47:15 PM , Rating: 2
If you get women being "loathed" from the Bible, then you're illiterate.

Husbands, love your wives, just as Christ loved the church and gave himself up for her

In this same way, husbands ought to love their wives as their own bodies. He who loves his wife loves himself.

Just because men screwed things up does not mean that God calls for women to be "loathed", subjugated, or otherwise treated poorly.

And maybe Islam calls for those who don't believe to be killed, but Christianity does not. It does call those who believe to go and spread the good word to others, but in no way does it say to force it on them. Again, there were men who tried, but that doesn't mean the Bible says it.

There are passages atheists try to quote to imply that but they all take it out of context. For instance, Deuteronomy 17.

“If there is found in your midst, in any of your [b]towns, which the Lord your God is giving you, a man or a woman who does what is evil in the sight of the Lord your God, by transgressing His covenant, 3 and has gone and served other gods and worshiped them, or the sun or the moon or any of the heavenly host, which I have not commanded, 4 and if it is told you and you have heard of it, then you shall inquire thoroughly. Behold, if it is true and the thing certain that this detestable thing has been done in Israel, 5 then you shall bring out that man or that woman who has done this evil deed to your gates, that is, the man or the woman, and you shall stone them to [c]death. 6 On the [d]evidence of two witnesses or three witnesses, he who is to die shall be put to death; he shall not be put to death on the [e]evidence of one witness. 7 The hand of the witnesses shall be first against him to put him to death, and afterward the hand of all the people. So you shall purge the evil from your midst.

Of course they usually conveniently leave out the first line which speaks to the transgression of not following the Lord's covenant with the people of Israel. Yes the Lord is a God that required obedience from his people. But those laws no longer apply since the Lord no longer requires sacrifices from his people to show obedience and belief. Christ extended God's covenant with the Jews to all people. He only asks two things. Belief in him and belief in his son.

RE: I did it
By FITCamaro on 10/22/2012 4:53:23 PM , Rating: 2
Jesus was pretty clear on the matter of whether those who follow him should execute those who sin.

"May he who is without sin cast the first stone".

RE: I did it
By Motoman on 10/22/2012 9:06:44 AM , Rating: 2
Deeply disappointed to see that you're that stupid.

Do you really need a lecture on subjective anecdotes?

So sad that humanity hasn't grown up and pulled on it's big-boy pants yet.

RE: I did it
By FITCamaro on 10/22/2012 12:32:40 PM , Rating: 2
Yes because counting on man to provide all the answers is a sign of intelligence...

No no...
By Prime2515103 on 10/20/2012 6:07:58 PM , Rating: 1
Oh what a crock. Everybody knows the moon was put there to hide the spaceship that's inside it. You know, the one described in Revelations? Look at it's dimensions and look at the dimensions of the moon. It fits right inside. This is the spaceship that is going to take us all to Orion this December.

RE: No no...
By StevoLincolnite on 10/20/2012 8:47:47 PM , Rating: 2
What you state is about as probable as Nazi's living on the moon ready to invade Earth on a flock of seagulls.

RE: No no...
By Steve Blowz Jobz on 10/20/2012 11:00:05 PM , Rating: 1
Actually Nazis are here on Earth, and they rule it.

PS. No jokes, I'm one of them.

RE: No no...
By Prime2515103 on 10/21/2012 9:01:46 AM , Rating: 2
I thought they lived in the center of the earth...

RE: No no...
By JediJeb on 10/22/2012 2:47:18 PM , Rating: 2
That was the best stupid movie I have seen lately.

RE: No no...
By Prime2515103 on 10/21/2012 9:03:01 AM , Rating: 2
You only say that because that's what they want you to believe. They have control of everybody's minds you know.

RE: No no...
By delphinus100 on 10/21/2012 12:48:55 PM , Rating: 2
Isn't thee a movie about that? I thought it was fiction, I guess it's really a documentary...

RE: No no...
By StormyKnight on 10/23/2012 1:10:59 AM , Rating: 2
And I ran, I ran so far away...

Sorry. Had an 80s moment there...

I wonder
By bug77 on 10/20/2012 6:07:21 PM , Rating: 1
So, there were two planets sharing an orbit at the exact distance from the Sun necessary to sustain life. Could this mean the odds of life in other solar systems goes up if this collision theory is correct?

RE: I wonder
By Goty on 10/21/2012 1:21:21 AM , Rating: 2
They did not share an orbit, they had intersecting orbits. During planetary formation and heavy bombardment, there were many objects with (relatively) highly elliptical orbits. Frequent collisions resulted in the accretion of many of those objects onto the more massive bodies and circularization of the orbits of most of the bodies in the solar system.

Also, no.

RE: I wonder
By bug77 on 10/21/2012 2:09:16 PM , Rating: 2
Ok, let me explain a bit better. One of the arguments against life on other planets is that a planet needs to orbit in a rather narrow region around its sun so that life (as in human, not some exotic form) can develop. Now, of course two celestial bodies won't share exactly the same orbit, that would be a terrific coincidence. It could be downright impossible, I don't know the math. But the fact that another body, large enough to create the Moon was orbiting in the same neighborhood, I think that would mean the probability of planets forming within the comfort zone isn't so low after all.
Of course, astronomy is just a hobby of mine, so there's a lot of things I'm unaware of. That much I know.

RE: I wonder
By delphinus100 on 10/21/2012 12:56:21 PM , Rating: 2
Goty is right. Such collisions don't care if they occur in a biologically comfortable part of their systems, or not. It wouldn't seem to change the chances of life elsewhere, one way or another.

It would help if we could more easily detect Earth-mass (and smaller) exoplanets, to get a better sense of overall planetary formation dynamics, but give it time...

I have a theory
By pwnsweet on 10/20/2012 7:53:57 PM , Rating: 2
God created it

RE: I have a theory
By jvillaro on 10/21/2012 2:41:57 AM , Rating: 2
First explain god...

RE: I have a theory
By PrinceGaz on 10/21/2012 12:30:55 PM , Rating: 1
Read your bible; the creation of the Moon is explained in Genesis 1:16.

Admittedly more detail about exactly how it took place would be desirable, as miraculously creating a roughly 73 quintillion ton object orbiting the Earth probably deserves a little more than "God made two great lights ... the lesser light to govern the night".

I suppose we should be thankful for that level of detail, as the creation of everything else (excluding the Sun, "the greater light to govern the day") is covered by the end of Genesis 1:16 what must be the most concise summary of major events ever "He also made the stars."

blue moon
By cludinsk on 10/21/2012 11:49:34 AM , Rating: 2
Well, since the moon is made of cheese, we have to figure out how the cheese got there. I expect it has something to do with the cow that jumped over the moon, maybe she dripped some milk that curdled. That's my best guess anyway.

Just wondering,
By JediJeb on 10/22/2012 2:57:10 PM , Rating: 2
If two planets could form in an area of the accretion disk near enough to each other that they would eventually collide, why would their composition be different enough that we would be able to tell if there was a through mixing of the debris or not?

Two similar size planets forming from the same material should be nearly the same in composition unless one forms much earlier than the other. As for the lighter Zinc atoms being missing from the moon, did they take into consideration the lower atmospheric pressure and the higher degree of solar and cosmic radiation hitting the surface which could have caused the lighter isotope to be in a lower concentration? There are a lot of variables between what a rock on Earth and a rock on the Moon would have been exposed to between the time they formed and the time when man finally got there to take a sample. Unless you are looking at some fairly deep core samples from the Moon that is.

"I modded down, down, down, and the flames went higher." -- Sven Olsen

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