back to article 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 …


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  1. Graham Wilson

    Irrespective of theory.

    Irrespective of which is the correct theory, it'd have been a nice time to take a long vacation on Mars.


    1. Vladimir Plouzhnikov

      Re: Irrespective of theory.

      I'm afraid you'd have found the weather there a little rough back then. Like intermittent marsquakes, constant lava flood warnings in place, major meteor showers expected and category 128 dust-and-carbon-dioxide storms...

      1. Destroy All Monsters Silver badge

        Re: Irrespective of theory.

        ...and then your house goes into foreclosure!

      2. Graham Wilson

        @Vladimir Plouzhnikov -- Re: Irrespective of theory.

        Right, I'm living in my hermetically sealed vehicle which is hopping about for safety--thing's ain't good here on Mars. But I've been watching the sky and earth's a spectacular messy ball-of-fire.

        Better here than there.

  2. Anonymous Coward
    Anonymous Coward

    with that rendered photo

    with that rendered photo, I wonder if being on the opposite side of Earth would even matter.

    1. DJV Silver badge

      Re: with that rendered photo

      No, you would definitely not have survived. Not only that but back then the atmosphere (if any) was not breathable - also it was early closing day and umbrellas were in short supply.

    2. Goat Jam

      Re: with that rendered photo

      You would be OK if you had a "magic cave" I suppose.

      <shudder> What a terrible movie that was </shudder>

      1. Kamal Hashmi

        Re: with that rendered photo

        I thought it was beautifully shot and acted and didn't shy away from the End.

        It was a bit boring though...

  3. Stevie



  4. Anonymous Coward
    Anonymous Coward

    Not quite a Friday story yet ...

    ... 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.

  5. Anonymous Coward
    Anonymous Coward

    Pah, nothing but liberal lies, I tell you!

    Everyone knows that the moon was created at 10:33 CST on Monday, October 24, 4004 BC. That's why we call it the "moon", from "Monday", innit?

    1. Naughtyhorse

      Re: Pah, nothing but liberal lies, I tell you!

      curse you!

      beat me to it!

    2. Michael H.F. Wilkinson Silver badge

      Re: Pah, nothing but liberal lies, I tell you!

      That date is 15 minutes off (Pratchett and Gaiman, 1995).

      1. Anonymous Coward
        Anonymous Coward

        Re: 15 minutes off

        Depends upon whether you're talking about the start of the creation of the moon, or the end.

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  7. An(other) Droid

    Fifth Element and Armageddon

    If only Bruce Willis had been around that time, he would have stopped that planet from crashing into our rock. For documented evidence of his previous exploits, see message title.

  8. Matt Bryant Silver badge

    Real explanation.

    Obviously, Gawd was busy driving all the planets about and sorting out their orbits, etc., when Mrs Gawd said; "Go on, let me drive one for a minute....."

    1. asdf

      Re: Real explanation.

      You mean Mr. Flying Spaghetti Monster and the Misses right? You better or as a the faithful Pastafarian I am I will need to declare silly jihad on you.

      1. Thorne

        Re: Real explanation.

        "You mean Mr. Flying Spaghetti Monster and the Misses right?"

        The spaggetti monster didn't need the missus. He was drunk at the time as it was written in the Pastafarian Bible

      2. Matt Bryant Silver badge

        Re: Real explanation.

        ".....I will need to declare silly jihad on you." Don't be silly, the real jihadis don't let their women drive at all!

  9. NomNomNom


    1. Anonymous Coward
      Anonymous Coward

      I agree with you.

      But I don't see any reason that God wouldn't have done it by colliding two planets... that fits with what I understand to be God's sense of humour.

      1. NomNomNom

        Re: I agree with you.


        1. ChrisM

          Re: I agree with you.

          Nice try,.got the caps and swivel-eyed lunacy right but would have been better as anon

      2. Anonymous Coward
        Anonymous Coward

        Re: I agree with you.

        I think you mean God's sense of economy.

      3. Naughtyhorse

        Re: I agree with you.

        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.

        1. This post has been deleted by its author

        2. TeeCee Gold badge

          Re: I agree with you.

          "...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.

  10. ElNumbre
    Thumb Up


    We won, and the moon is our trophy.

    Go Earth!

  11. AfternoonTea

    Surely this was news 25 years ago..

    1. Anonymous Coward

      nah... was news about 4 billion years ago.

  12. Jones

    I thought Apple invented the moon ??

    1. NukEvil

      No, they merely patented the moon's rounded corners.

  13. Gene Mosher

    There's more to this, I'm pretty sure.

    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.

  14. Anonymous John

    Re: giving a "day" of just two to three hours.

    How would that work? By the time you got to sleep, it would be time to get up again. A quick shower, shave, and breakfast, and it would be bedtime again.

    1. itzman

      Re: giving a "day" of just two to three hours.

      Sound entirely like my student days....

  15. Anonymous Coward
    Anonymous Coward


    given the masses and speeds involved, wasn't Earth shattered to pieces (instead of "absorbing" the intruder)?

    Still fluid enough (à la Lava lamp blobs)?

    1. Anonymous Coward
      Anonymous Coward

      Re: Why...

      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.

    2. Anonymous Coward
      Anonymous Coward

      Re: Why...

      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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  17. Mike 16

    Not surprising

    "God does not play dice with the Universe"

    - Einstein

    "He does, however, occasionally enjoy Billiards"

    - Velikovsky

    1. Francis Boyle

      Re: Not surprising

      Surely that was not Velikovsky but the HHGTTG. The latter is at least rather more scientifically reliable.

    2. Bob Holtzmann

      Re: Not surprising

      He may have to forfeit his turn, though, if he didn't call the grey ball striking and getting engulfed by the blue ball.

  18. Goat Jam
    Paris Hilton

    What are "rotation forces"?

    Surely we can come up with a sexier name than that don't you think?

  19. Local G

    There are many ways to skin a cat...

    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.

    1. Anonymous Coward

      Re: There are many ways to skin a cat...

      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...

      1. Mephistro

        Re: There are many ways to skin a cat...

        "... the hit that knocked Uranus askew"

        That had to hurt!

    2. Michael H.F. Wilkinson Silver badge

      Re: There are many ways to skin a cat...

      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.

      1. deadlockvictim

        Re: There are many ways to skin a cat...

        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).

        1. Kamal Hashmi

          Re: There are many ways to skin a cat...

          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.

  20. QuinnDexter

    "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

    1. This post has been deleted by its author

  21. fearnothing

    >>What are "rotation forces"?

    >>Surely we can come up with a sexier name than that don't you think?

    This calls for a suitable unit of measurement!

  22. Afflicted.John

    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?

  23. Tom 13

    Bah! Everyone knows the Minervans did it.

    As documented by James P. Hogan was back in '81:

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