Moon was formed when PLANET SMASHED INTO EARTH That old theory that the Moon was formed out of fragments of Earth blasted into space after a massive planetary collision 4.5 billion years ago has gained support from two new studies. Giant impact, common at the end of planet formation Boffins have tried to figure out exactly how a giant impact in our solar system made the …
You would be OK if you had a "magic cave" I suppose.
<shudder> What a terrible movie that was </shudder>
... or else it'd have been something like "Cannibal Earth gulping on bits of Theia's core", and the article claiming that Young Earth was found to have been a fiery-blooded planetovoric predator delighting in smashing smaller cousins to bits and slurping on the splattered planetary offal. After a particularly bad episode of cannibalistic carnage, having a vision of the spaghetti monster, it vomited and voila, the moon formed in a perfect image of a meatball. Or some such.
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well to start with the picture of the event in the article showed theia hitting the earth on the wonk as it were (with a bit of side if you will) - now I cant see any truly intelligent designer allowing such a thing. a really intelligent designer would have applied a little screw to theia in deference to the designers teachers third law of motion.
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"...a really intelligent designer would have applied a little screw to theia..."
Correct. Then he'd have got the position to take the subsequent shot on the red (Mars) after the blue (Earth) rather than the break ending there with the cue ball (Moon) snookered by the respotted blue.
The Theia impact also nicely explains Earth's 23.5 degree axial tilt as well, of course.
Perhaps someday we will be able to guess with some probability of certainty from which direction Earth was struck by Theia, perhaps pushing it toward or away from the Sun, or perhaps speeding up/slowing down the time of its annual journey around the Sun, depending upon from which relative direction it was traveling prior to the collision.
It could have been. The gravitational attraction of the "pieces" would be the same as a solid earth. Thus... Well, it does not move, they then settle back together.
A nice long example of this is mentioned in the "How to destroy earth, a guide for evil supervillians" page.
http://qntm.org/destroy
On the scale involved and under the physical conditions of the collision rock is pretty flimsy stuff. It'd be more like two drops of water coalescing (though without the surface tension effects). We can see this sort of thing first hand right now - plate tectonics puts huge pressure on rock and it flows like putty.
Even if it did completely shatter there would still be a point about which all the remains are orbiting, and any debris without sufficient velocity to escape would just fall back towards it, and the planet would reform. All that happened here was that a large amount of the material coalesced on one side of that point and became the earth, and the rest coalesced on the other side and became the moon.
One has to remember that the moon doesn't orbit the centre of the earth. It orbits a point somewhere along the earth-moon line. And the earth also orbits that point too, but because the earth has a lot more mass we don't (as humans) really notice that (the point lies inside the earth I think). The consequence is that the remains that became the moon and earth are still 'falling' towards the original orbital centre in the sense that all orbits can be considered to be falling in the right way so as to keep missing.
In the sci-fi book "The Forge of God" Greg Bear uses an idea that nicely corresponds to all this. The concept is that something sufficiently heavy and dense could orbit the centre of the earth ***inside*** the planet despite the enormous drag of all that rock and mantle. The book actually has two such objects composed of neutronium and antineutronium. When their in-planet orbits eventually decayed and the two objects collided in the centre of the earth a matter-antimatter reaction took place on an enormous scale and destroyed the planet.
It is conceivable that a black hole could also orbit the planet's centre inside the earth. Although it would be more like the earth orbiting around the black hole that just happens to be inside it. I'm not sure that I'd want to be around if that were going on!
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But does that go for making moons, too?
There are over two dozen moons in the Solar System. Were all of them the result of lucky strikes by alien planets?
And why did the new moons of our Solar System flourish in the orbits of the big gassy planets (Jupiter 4, Saturn 9, Uranus 6)? Is that where the valuable resources they need are?
Were these two dozen Theias bellicose when they attacked and are the moons they left behind standards planted in our Solar System claiming their Sovereignty?
Inquiring minds want to know.
All or nearly all the big outer system moons were probably formed out of acretion disks surrounding each gas giant, sort of like the solar system in miniature. Evidence of this is in the nearly parallel orbital planes of each moon system, and their close alignment with the equator of their parent planets. Also they all orbit in the same direction as that planet spins. One exception; Even tho the Uranian moons follow this pattern, Uranus has that huge tilt (>90deg). Seems those moons must have formed during/after the hit that knocked Uranus askew.
Most of the small outer system moons are captures and have all kinds of orbits.
Oddly, Earth's moon has a huge orbital tilt of 5 degrees, but compared to the ecliptic (Earth's orbital plane), NOT Earth's equator. Bizarre. Pluto's moon Charon is thought to also be a knock-off, but its orbital tilt in relation to Pluto's equator is 0.001 degree! What the heck?
I suspect our oceans, always sloshing around, causing trouble...
Many astronomers now say the moon is not really a satellite of earth (hence "That is not a moon" ;-) ), because it is not many orders of magnitude lighter than the Earth. The Earth-Moon system is a double planet (much like Pluto and Charon is properly called a double dwarf planet).
Most moons formed in orbit around their planet, as mini solar systems (and can have a strikingly different composition from their parent planet, and even each other, depending on the distance to the planet). Some, like Phobos and Deimos of Mars, were probably captured asteroids.
I am open to correction on this and it is rather simplistic, but isn't a planet defined as an object beyond a certain mass that revolves around a star? A moon, likewise, is an object beyond a certain mass that revolves around a planet.
With a double planet system, one could not tell which revolves around the other (or they both revolve around each other and as a unit revolve around a star).
I think the fact that the common point around which they orbit is inside one of them makes the other one a 'moon'.
If the point was even fractionally outside the Earth then I'd formally accept the 'double planet' description.
Regardless of that, the Moon certainly has a greater influence on this planet than most satellites on their planets - the tides and consequent evolution of land-based life being the most notable.
"The second study, by Robin Canup at the Southwest Research Institute in Boulder, also backs the impact theory, but she reckons that the Earth and the planet that hit it were each around half of the Earth's current mass."
The maths doesn't work for this unless her assumption of each Proto-Eath and Theia has a tolerance range of half a moon each, which is a kinda hefty tolerance...
@ Local G
Perhaps the matter that makes up the numerous moons coalesced seperately to the gas giants and then got dragged into orbit around them as the big fellas were on their little trek around the sun
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So what do they know about the Moon that they did not 10 years ago? Reason being that the theory of the Moon's composition revolved around the surface being comprised of a single tectonic plate which floated in the past on top of a now cooled mantle. The hypothesis was that here was a small molten iron core which had long since cooled although the presence of deep moonquakes does mean that "there's something going on in there".
If these theories are true, then the Moon could not have an iron core, could it?
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