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The Moon's Two Sides Look So Different Thanks To 4.5 Billion-Year-Old Physics (forbes.com)

Posted by samzenpus on from the good-side-bad-side dept.

StartsWithABang writes: 4.5 billion years ago, a giant object collided with our proto-Earth, kicking up debris that eventually coalesced into the Moon. While the near side contains dark maria and lunar lowlands, the far side is almost exclusive heavily cratered, high-mountainous regions. This was a mystery for a long time, but it appears that heating from the hot, young Earth caused a chemical and crustal difference between the two faces.

96 comments

  1. I could be missing something by ILongForDarkness · · Score: 2

    but couldn't the far side have craters and the near side few because something big, like I don't know the earth, blocks one side and not the other?

    1. Re:I could be missing something by Michael+Woodhams · · Score: 3, Informative

      As seen from the moon, the Earth is only about two degrees across, so the proportion of projectiles blocked by it would be miniscule. Even that small effect is reduced (possibly beyond zero) by 'gravitational focusing': projectiles which come towards the moon from the direction of the Earth which would otherwise have missed can be deflected by Earth's gravity such that they hit. (And this happens more often than projectiles that would have hit being deflected so they miss.)

      Here is a paper I found on gravitational focusing.

      --
      Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
    2. Re:I could be missing something by Pharmboy · · Score: 1

      No, they explain this in the article. This might account for maybe 1% difference due to the actual distance between the Moon and Earth, but that is about it.

      Ironic, I was watching "The Universe" on Netflix earlier, the exact episode that covered most of this. Good stuff.

      --
      Tequila: It's not just for breakfast anymore!
    3. Re:I could be missing something by Anonymous Coward · · Score: 1

      Although the Moon was much closer to the Earth in the past, perhaps 20x closer. The article suggests that the Moon formed just outside of the Earth's Roche limit. However, the articles don't explain the difference in the number of craters on the two sides of the moons. I would guess that most of the visible craters were formed prior to the maria, although I'm not sure why the events that formed the maria occurred almost at the end of (or after) the heavy cratering periods.

    4. Re:I could be missing something by rasmusbr · · Score: 3, Interesting

      Another interesting aside is that many have tried to explain gravity by postulating that the universe is full of tiny particles that fly about randomly in all directions and that gravity works because bodies block the particles from hitting one another.This is sometimes called the screening theory of gravity.

      If you make some reasonable assumptions you will find that two nearby bodies would block particles from hitting one another, creating forces that follow the inverse square law...

      These theories also predict that planets will de-orbit and crash into their stars, and that moons will similarly crash into their plants. But hey, no theory is perfect.

    5. Re:I could be missing something by Anonymous Coward · · Score: 0

      The space between objects is MUCH bigger than the objects themselves.

      www.distancetomars.com

      You can see the Earth-Moon system's size here.

    6. Re:I could be missing something by MobSwatter · · Score: 1

      The Illuminati wise tail about the formation of the moon. If this were the case, then the earth would have coalesced with iron deposits on one side after the collision and the orbit lock would have been to both celestial objects likely resulting in a solid iron core in the earth, and we probably wouldn't be here. I would have expected they would have better engineered a load of bull-crap to feed us based upon being German/English Blue Blood/Mongol origins of this organization. Why not? They did a hell of a job with the federal reserve system. Perhaps they were never really focused on actual goals of NASA either when they loaded NASA with Nazi's.

    7. Re:I could be missing something by Anonymous Coward · · Score: 0, Troll

      20x closer

      Last time I checked, our unit systems measured distance (not closeness), temperature or heat (not coldness) and speed (not slowness).

      Anyone who says "X times closer" or "X times colder" or "X times thinner" or "X times slower" has failed to grasp the nature of measurement.

    8. Re:I could be missing something by Anonymous Coward · · Score: 1

      How's that asperger going?

    9. Re:I could be missing something by Gadget_Guy · · Score: 1

      Ironic, I was watching "The Universe" on Netflix earlier, the exact episode that covered most of this. Good stuff.

      No, it would be ironic if you had watched "The Universe" to find out about this topic and they explained the concept of irony to you instead!

    10. Re:I could be missing something by Anonymous Coward · · Score: 0

      How do you measure rotational frequency then? 200rpm is 10x faster than 20rpm but the period is 1/10th as long. :P

    11. Re:I could be missing something by RubberDogBone · · Score: 1, Informative

      You are correct. But this sort of ignorant "X times to a lesser value" bullshit math is rampant. I use it to easily spot stupid people for me.

      Sometimes I will ask them, please draw for me on a blackboard how you would work "20 times less than X" and laugh at them when they can't do it.

        But the scary thing is how many people don't understand what's wrong. It is simply that you cannot multiply and reach a lower value. 10 times less can't work. Ever.

      One tenth can. But fractions are apparently impossible.

      --
      Sig for hire.
    12. Re:I could be missing something by Anonymous Coward · · Score: 0

      No, they explain this in the article. This might account for maybe 1% difference due to the actual distance between the Moon and Earth, but that is about it.

      Ironic, I was watching "The Universe" on Netflix earlier, the exact episode that covered most of this. Good stuff.

      Ironic? In what way?

      Sounds like a coincidence to me.

    13. Re: I could be missing something by Anonymous Coward · · Score: 0

      The Moon will crash into my plants? Oh noes! I must put a better roof above my precioussss flowerssss.

    14. Re:I could be missing something by wonkey_monkey · · Score: 1

      And yet, somehow, we all knew exactly what he meant.

      If you want to be really picky, how else would one define "closeness" except as 1/distance? Oh look, all the math works out perfectly - twice as close is half as distant. Problem solved.

      --
      systemd is Roko's Basilisk.
    15. Re:I could be missing something by Dog-Cow · · Score: 2

      Last time I checked, English was a natural language, not a technical language. As long as the meaning is understood, the expression is valid. In English, it's perfectly valid to refer to reciprocal relationships from either direction. If something is twice as far, it is half as close. If something is half as far, it is twice as close.

    16. Re:I could be missing something by gsslay · · Score: 1

      If only TFA specifically mentioned this and explained why not.

      Oh wait, it does. You could indeed have missed something; in this case Reading TFA.

    17. Re:I could be missing something by BlackPignouf · · Score: 1

      It is simply that you cannot multiply and reach a lower value

      You must be fun at parties.
      What about 0.1 times x, when x is positive? Note : no fraction involved.
      What about 2*x, when x is negative? Note : no decimal involved.
      If you're gonna laugh at stupid people for math problems, you might want to check your math first.

    18. Re:I could be missing something by FlopEJoe · · Score: 1

      Sometimes I will ask them, please draw for me on a blackboard how you would work "20 times less than X" and laugh at them when they can't do it.

      You must be fun at parties

    19. Re:I could be missing something by FlopEJoe · · Score: 1

      Damn it! Missed someone else saying the exact same thing.... never mind

    20. Re:I could be missing something by fisted · · Score: 1

      You must be fun at parties.

      --
      CLI paste? paste.pr0.tips!
    21. Re: I could be missing something by cthulhu11 · · Score: 1

      Thank you. This sort of thing bugs the hell out of me.

    22. Re:I could be missing something by stoatwblr · · Score: 1

      "As seen from the moon, the Earth is only about two degrees across"

      Now.

      At the time of the late heavy bombardment, the moon was a _lot_ closer than it is now. Close enough that the earth was a fairly effective shield.

      It also means that tidal forces and heating effects would have been a lot stronger too.

    23. Re:I could be missing something by mcswell · · Score: 1

      Perhaps a little OT, but: "Then comes the list of problems. It says, 'John and his father go out to look at the stars. John sees two blue stars and a red star. His father sees a green star, a violet star, and two yellow stars. What is the total temperature of the stars seen by John and his father?' -- and I would explode in horror." (Richard Feynman, on a "new math" textbook he was reading)

    24. Re:I could be missing something by mcswell · · Score: 1

      Similar to the theory of light bulbs as darkness absorbers?

    25. Re:I could be missing something by rasmusbr · · Score: 1

      Similar to the theory of light bulbs as darkness absorbers?

      In a sense yes. Attractive forces like gravity and magnetism have always been a challenge to explain in terms of direct contact.

      The motivation for the screening theories is that some people, or perhaps most people, have a deep-seated intuition that all of physics ought to be reducible to direct contact interaction.

      You could say that one of the prime motivations of the early scientist was to prove that there were no non-direct contact forces at work in the universe, except for the force of God himself.

  2. The moon could have been artificially created. by Anonymous Coward · · Score: 5, Funny

    Another, more plausible explanation is that the moon was actually an ancient artificial space station, placed in a very specific orbit around the earth. Over time, debris has collected on it, giving it its current appearance. The fact that it always faces the earth, and orbits the earth once every month is very intriguing. This isn't something we'd expect to happen were the moon a natural creation. That suggests that it likely was created as an artificial space station which has since become, for lack of a better term, dusty over a long span of time.

    1. Re:The moon could have been artificially created. by Anonymous Coward · · Score: 5, Funny

      That's no space station. It's a moon!

    2. Re:The moon could have been artificially created. by Michael+Woodhams · · Score: 1

      Not only that, but without the moon, Earth's day would not be even close to 24 hours. (Lunar tides over billions of years have modified the length of the day.) Think how inconvenient that would be! I think you're on to something.

      --
      Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
    3. Re:The moon could have been artificially created. by ClickOnThis · · Score: 4, Informative

      The fact that it always faces the earth,

      Nothing remarkable about that. It's due to tidal locking and is quite common.

      and orbits the earth once every month is very intriguing.

      Yea, and Lou Gehrig died of Lou Gehrig's disease. [cue creepy music]

      --
      If it weren't for deadlines, nothing would be late.
    4. Re:The moon could have been artificially created. by Anonymous Coward · · Score: 1

      Did you read the article? The moon was formed much closer to the than it is now, perhaps 20x closer. The authors did some calculations that suggest that the moon likely became tidally locked within a few hundred days of its formation due to its proximity to Earth at the time of its formation.

      And as for it being curious that the moon orbits the earth once every month, that is plain silly. The month was originally defined in terms of the time it takes the moon to go through its phases. And if you're questioning why it's 29 days (approx) and not 10 or 100 or 1000 days, that is a simple function of its distance from Earth and the combined mass of the Earth-Moon system. And the distance of the moon from the Earth is mostly a result of the amount of time that has passed since its formation. Nothing curious here at all.

    5. Re: The moon could have been artificially created. by JDevers · · Score: 4, Funny

      Damned, you would think he had to see that coming.

    6. Re:The moon could have been artificially created. by Dereck1701 · · Score: 1

      That would be neat, however if it were a station I would bet its inexplicable mass (probably much lighter) would be driving astrophysicists crazy. I assume that all of the equations are working out as this isn't the case.

    7. Re:The moon could have been artificially created. by murdocj · · Score: 1

      dang, where's my mod points when I need them?

    8. Re:The moon could have been artificially created. by Anonymous Coward · · Score: 0

      It isn't that ancient, some think god made it, just like it is, about 6000 years ago.

    9. Re:The moon could have been artificially created. by 140Mandak262Jamuna · · Score: 1

      Yea, and Lou Gehrig died of Lou Gehrig's disease. [cue creepy music]

      More creepily all the onomatopoeia words sound like the sound they describe! bang!

      --
      sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
    10. Re:The moon could have been artificially created. by Anonymous Coward · · Score: 0

      Another, more plausible explanation is that the moon was actually an ancient artificial space station, placed in a very specific orbit around the earth. Over time, debris has collected on it, giving it its current appearance. The fact that it always faces the earth, and orbits the earth once every month is very intriguing. This isn't something we'd expect to happen were the moon a natural creation. That suggests that it likely was created as an artificial space station which has since become, for lack of a better term, dusty over a long span of time.

      So chicken / Egg argument..

      How do we know that the concept of a month was not based on the moon's orbit ?

      The actual coincidence is that the moon at this point in history is the right size and distance from he surface of the Earth that it appears the exact same size as the sun. This is temporary.. in a few million years it will be farther away and appear smaller. (due to our oceans, the moon is receding away from us at a rate of about 5 inches per year..)

    11. Re:The moon could have been artificially created. by ACE209 · · Score: 1

      But what about the distinct whooshing sound the moon makes when passing over your head? Can you explain that?

      --
      "we are all atheists about most of the gods that societies have ever believed in. Some of us just go one god further."
    12. Re:The moon could have been artificially created. by ageoffri · · Score: 1

      Don't forget that humans are descended from the crew of the space station and are divided into two factions. The mutineers and loyal crew. The AI of the station is just waiting for a human to return.

      --
      -- Slashdot, making the Left look conservative since 1997.
    13. Re:The moon could have been artificially created. by Anonymous Coward · · Score: 0

      More creepily all the onomatopoeia words sound like the sound they describe! bang!

      It's creepier than that: the real sound is similar to the onomatopoeia word! How did they do that?

    14. Re:The moon could have been artificially created. by geantvert · · Score: 1

      The article mentions that the moon was tidally locked from the start but does not explain why. At first I was a bit suspicious because that is a huge assumption. The paper in http://iopscience.iop.org/2041... explains that in more details.

      Also, another reason for having 12 months is that this number is, like 60 and 360, quite remarkable because it has a lot of divisors. Simply speaking 12 is the smallest number that can divided by 2, 3, 4 and 6 while 60 can also be divided by 5 and 10. That is why we still count eggs in dozen, times in 60 minutes or 60 seconds, days in 24 hours (2*12) ...

      In ancient calendars, the time was often measured in 'moons' which made a lot of sense for hunter gatherers so when farming was invented, they switched to a yearly based calendar and it made sense to decompose the year in 12 months (so a convenient number) that also had the advantage of being relatively close to the moon period.

    15. Re:The moon could have been artificially created. by Anonymous Coward · · Score: 0

      But we just haven't someone with the right stuff to the correct location yet!

    16. Re:The moon could have been artificially created. by stoatwblr · · Score: 1

      The earth's day has always been 24 hours, however the defined period of the 86400 seconds within it may have changed over the millenia.... :-)

  3. The moon's integrated face system by Anonymous Coward · · Score: 0

    The integrated face system caused the two different sides of the moons.

  4. How could the Earth heat it? by Billly+Gates · · Score: 1

    I read the article and it mentioned the hot side faced Earth. Not that heat radiating tens of thousands of miles in a vacuum heated it thousands of degrees.

    More than like the force of the bang pushing the material left it run towards the back facing Earth not to mention gravitational pulls swelled the molten core towards Earth. And a 100 degree heat difference from the side facing the sun as well might of had a very small role.

    1 billion years ago the Earth had 100 to 1,000 foot tides as the Moon and the Earth were much closer which is how plants evolved from Sea Algae and fish to land animals as great pools were left to get wet and dry over and over. I would imagine the molten cores would have as similiar effect of a pull one side with pressure as well.

    --
    http://saveie6.com/
    1. Re:How could the Earth heat it? by Anonymous Coward · · Score: 0

      Did you read both articles, particularly the iop.org paper? The physics of the heating are discussed there, including calculations of how much heating would have occurred.

    2. Re:How could the Earth heat it? by techno-vampire · · Score: 2

      I think that you misunderstood the article. It's not that the hot side faced the Earth, it's that the heat of the Earth (around 2700 Kelvins) kept that side of the Moon (orbiting considerably closer than it does now) hot longer than the side facing away.

      --
      Good, inexpensive web hosting
    3. Re:How could the Earth heat it? by Michael+Woodhams · · Score: 5, Interesting

      1 billion years ago the Earth had 100 to 1,000 foot tides as the Moon and the Earth were much closer

      My initial response is "I don't think so." My second response is to calculate, so here goes:
      Current distance to moon = 384,400 km = 4 x 10^8m
      Current rate of increase in distance to moon = 3.8 cm/year = 4 x 10^-2 m/year.
      If this rate were constant over a billion (10^9) years, then a billion years ago the distance to the moon was 4 x 10^-2m/year*10^9year = 4 x 10^7 m closer, or 10% closer. Tidal effect strengths are inverse-cube in distance, so a billion years ago, lunar tides would have been about 30% larger than now.

      This doesn't come close to "100 to 1000 foot tides."

      --
      Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
    4. Re:How could the Earth heat it? by Billly+Gates · · Score: 1

      My facts were quoted from a college level biology book. It was believed the tides were much bigger.

      --
      http://saveie6.com/
    5. Re:How could the Earth heat it? by Namarrgon · · Score: 3, Interesting

      Good, but the rate of increase in distance to the moon isn't constant (it was faster in the past), and it's thought that the moon formed at a distance of only about 20 to 30 thousand kilometers.

      By your maths, 4B years ago would've put the moon at 60% its current distance, but at formation it is more likely to have been only 6% of current distance. Assuming similar mass to today, 60% closer implies more like 4.6x the current tidal force - but 6% distance might be 4,600x stronger forces (probably more, given that the distance to the Earth's surface was even closer). How this translates into actual tidal sizes is left as an exercise for someone who knows more than I do.

      Of course back then there probably wasn't much water around, given terrestrial temperatures in the thousands of degrees, but there may have been some impressive magma tides instead.

      --
      Why would anyone engrave "Elbereth"?
    6. Re:How could the Earth heat it? by Michael+Woodhams · · Score: 1

      What happened 4 billion years ago is not the point - the claim was made in the context of the 'conquest' of the land by multicellular life, which was only about 0.5 billion years ago (not 1 billion, as I used in my analysis, and so tides were likely only about 15% higher then.) I agree that tidal conditions were very different four billion years ago, and that my linear extrapolation would not apply so far back.

      10% (for a billion years, or 5% for 500 million) is a small enough change in distance that we wouldn't expect the recession rate to have changed a lot over that time. This is a somewhat weak point in my argument - the recession rate of the moon is largely dependent on how many Bay of Fundys there are in the world, so the current rate may not be typical. However the argument is strong enough to place the burden of proof on those making the claim: you claim an effect an order of magnitude greater than simple analysis allows for. Show evidence for these tides, or a well founded model which predicts these tides (at the required time.)

      --
      Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
    7. Re:How could the Earth heat it? by Michael+Woodhams · · Score: 1

      I've shown the claim is implausible, not impossible. I'd be interested to see what evidence there is to support it.

      I don't see the need for the claim from an evolutionary point of view: there is no reason I am aware of to suppose that current tides are insufficient to drive organisms to evolve into terrestrial niches.

      --
      Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
    8. Re:How could the Earth heat it? by kwbauer · · Score: 1

      Wait, I thought that everything ever published that tells us exactly how evolution happened is totally accurate? Is someone suggesting that there might be some minor mistakes in those textbooks? What's next? Are we going to hear some nonsense about the global warming models not quite predicting today with 100% accuracy?

    9. Re:How could the Earth heat it? by chmod+a+x+mojo · · Score: 1

      And the "article" was misconstruing the actual research. The actual study didn't say RADIANT heat from the Earth somehow magically went through the vacuum of space. The latent heat of the impact could very well keep many silicate minerals in a gaseous form on early Earth though.

      The study indicates that mathematically, higher levels of reflected solar radiation ("Earthshine") - which again, could be possible with post-impact silicate gas atmospheric compositions - contributed to the side that always faces the earth, while the side that only faces the sun had much less solar radiation heat input so cooled much faster.

      --
      To err is human; effective mayhem requires the root password!
    10. Re:How could the Earth heat it? by Namarrgon · · Score: 1

      Much more accurate than your assorted straw men, anyway.

      --
      Why would anyone engrave "Elbereth"?
    11. Re:How could the Earth heat it? by Anonymous Coward · · Score: 0

      I this rate were constant over a billion (10^9) years,

      ObXKCD: https://xkcd.com/605/

    12. Re:How could the Earth heat it? by ceoyoyo · · Score: 1

      "The actual study didn't say RADIANT heat from the Earth somehow magically went through the vacuum of space."

      That's kind of what radiant heat does.

    13. Re:How could the Earth heat it? by ceoyoyo · · Score: 1

      The rate won't be constant. The moon is gaining momentum by stealing it from Earth by raising tides. The closer the moon is, the larger tides is raises, which means it steals more momentum. The actual relationship is likely complex, but it's probably at least quadratic.

    14. Re:How could the Earth heat it? by geantvert · · Score: 1

      Only the Sun is allowed to send those magic rays!

    15. Re:How could the Earth heat it? by chmod+a+x+mojo · · Score: 1

      Oops, my bad. It was quite late and I meant to type "RADIATING" heat, as in heat being transferred through a medium, as should be obvious from the rest of the comment.

      --
      To err is human; effective mayhem requires the root password!
    16. Re:How could the Earth heat it? by ceoyoyo · · Score: 1

      I was being a smartass, but if you insist... your comment is incorrect throughout. The paper refers to "earthshine" which today is dominated by reflected sunlight. But the point of that paper is that right after the collision that created the moon, earthshine was dominated by radiated heat from the Earth, not reflected radiation from the sun, meaning that the earthshine was much more intense than today. The takeaway from the paper is literally the opposite of what your post said:

      "The actual study [did] say RADIANT heat from the Earth, [in complete obeyance of the laws of physics], went through the vacuum of space." This radiant heat kept the Earth facing side of the moon molten longer than the far side.

  5. Those _are_ some old physics. by berchca · · Score: 4, Insightful

    I wish we still had physics like that today... these new-fangled ones just don't coalesce like they used to.

  6. Re:Please StopWithABang by jfdavis668 · · Score: 5, Informative

    The link could have gone straight to the Penn State news article Forbes was reporting on: http://news.psu.edu/story/3178...

  7. Tidal Lock by BradMajors · · Score: 0

    This theory would require the moon to be tidal locked very early in its history. I didn't think that was true.

    1. Re:Tidal Lock by delt0r · · Score: 1

      it easily could be locked very quickly if it formed close to earth, just outside the roche limit for example. Of course if it liquid it is even harder to define "locked".

      --
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    2. Re:Tidal Lock by Anonymous Coward · · Score: 0

      Did you read the articles? Oh, I forgot, this is slashdot.

  8. sweet mysteries of life by PopeRatzo · · Score: 1

    it appears that heating from the hot, young Earth caused a chemical and crustal difference

    Heating from hot young things tends to cause chemical and crustal differences in my underwear.

    Sorry. It's Sunday night and my fantasy team is in the toilet and I've been drinking.

    --
    You are welcome on my lawn.
  9. Don't link to Forbes articles by Anonymous Coward · · Score: 1

    Forbes articles display just a blank page for anyone running browser protections, a clear sign that Forbes' web admins are totally clueless since they can't even get static content through to viewer eyeballs.

    1. Re:Don't link to Forbes articles by Anonymous Coward · · Score: 1

      Hang on, you run settings/extensions that purposefully disable and remove functionality from a website and then blame the web developers for not giving you a satisfying experience? Do you also remove the tires from your car and blame the manufacturer for the bumpy ride?

    2. Re:Don't link to Forbes articles by Anonymous Coward · · Score: 0

      Never under any circumstances enable Javascript for a site that renders an empty page when Javascript is disabled. The reason is that the site constitutes a double-jeopardy security threat.

      Developers who require Javascript even for static elements are showing you that they either don't know or don't care about security, or both. This greatly increases the probability that their site will be hacked, since it's low-hanging fruit.

      And when their site does get hacked, their Javascript will get replaced by malicious code, which then has an open highway into your browser because you enabled it to compensate for the developers' lack of competence at displaying static content without scripting.

      There is also the possibility of triple-jeopardy, if the site is itself malicious or some of its developers have been pressured by criminals. Showing a blank page may be a deliberate strategy designed to encourage people to disable their browser protections.

      So, treat a blank page as if it had clearly displayed "Security risk. Avoid this site."

  10. Did the moon form after the earth? by tinkerton · · Score: 1

    How do they know the earth was first fully formed and only then collided with something large causing the moon to form? I can imagine it was a bit of a jumble at the time but this claim seems a bit arbitrary. Why the need for a collision with something large? Was it something larger than the moon?

    1. Re:Did the moon form after the earth? by Anonymous Coward · · Score: 0

      Other possibilities seem somewhat implausible (i.e. the moon having been "spun off" from a fast rotating, molten Earth was one such theory).

    2. Re:Did the moon form after the earth? by tinkerton · · Score: 1

      That does sound implausible indeed.But moons forming in an accretion disk and gobbling up whatever was not absorbed into the center, that does sound acceptable. The earth also wasn't created out of a collision with the sun. Maybe they think the moon is too large for having formed the way other moons are formed.

    3. Re:Did the moon form after the earth? by ceoyoyo · · Score: 1

      IIRC the main piece of evidence is the similarity of isotope ratios in the moon and Earth, and the rarity of heavy elements in the moon. The moon appears to be enriched in silicates, which are the bits that would have been floating on top of a proto-Earth.

    4. Re:Did the moon form after the earth? by Teun · · Score: 1

      Fortunately we send a few missions to the moon that brought back soil samples.
      With these samples and a lot of remote sensing it became fairly certain that the moon is made up of similar material as the earth's mantle or crust.
      An (logic) extrapolation of this points to the moon being ripped out of the earth after the separation between core and mantle had already taken place.

      Even the creationists have it from their own source: http://biblehub.com/genesis/2-...

      --
      "The likes of Facebook and WhatsApp are free to those whose privacy is of zero value."
    5. Re:Did the moon form after the earth? by painandgreed · · Score: 1

      How do they know the earth was first fully formed and only then collided with something large causing the moon to form? I can imagine it was a bit of a jumble at the time but this claim seems a bit arbitrary. Why the need for a collision with something large? Was it something larger than the moon?

      It comes basically from the various theories on the formation of the moon. It could have been created in place, spun off of the earth, captured while it passed by, the result of a collision with another object, etc. So there were lots of different theories, and then there was the actual evidence dealing with the chemical make up of the moon, the orbital mechanics, the conservation of angular momentum, etc. Some theories were better than others and explaining the various facts. Some were much worse than the others at explaining the observed facts. In the late 90's, computer simulation of an object hitting the photo-earth and then forming into the current earth and moon because possible and showed that it was possible. That theory then jumped to the head of the line as it at least came in with a C grade (this was in the college physics presentation I attended in the early 90's on the topic) in the various criteria where other theories all still had D and F grades in some of them. It showed that the collision could have resulted in the proto-earth capturing the other objects iron core to explain our large core and the moon's lack of similar amount, the general chemical composition of both, etc etc. So far it seems the theory continues to get stronger. From last I heard, current theory is that two "moons" formed in orbit, and a smaller one eventually collided with the larger and formed the far mountainous side in a fairly non-energetic collision. that was to explain some of the differences between the near and far sides of the moon as well as asymmetric features of the moon. I haven't read this article, but it sounds like this might be an alternate theory to explain similar things. Eventually the theories will continue to get refined till we have a fairly good idea of how it all happened.

  11. ...and the Science would have been Better by Roger+W+Moore · · Score: 0

    Plus had that been the case we would not have a stupid title referring to "4.5 billion year old physics" which "StartsWithABang" would have known if he had any decent knowledge of physics, is a silly thing to say because the laws of physics are invariant with time. This is actually an incredibly fundamental point of physics since this symmetry with respect to time gives us conservation of energy.

    1. Re: ...and the Science would have been Better by Anonymous Coward · · Score: 1

      Good god the pedants are out tonight. 4.5 billion year old physics clearly means the physics in question began 4.5 billion years ago.

    2. Re: ...and the Science would have been Better by Roger+W+Moore · · Score: 1

      Did I claim that it meant that anywhere? In the simplest possible way it is wrong because the physics involved is at a minimum 13.8 billion years old since it has at least existed since the Big Bang. While you might regard this as pedantic in science details matter especially when communicating it. It's one thing to sacrifice accuracy for simplicity when communicating with the public but doing it unnecessarily like this is just sloppy and unscientific...and sadly something this writer who shamelessly self-promotes on Slashdot does far too often.

    3. Re:...and the Science would have been Better by Anonymous Coward · · Score: 0

      StartsWithABang might have been hanging around with physical cosmologists too much. :-)

      More likely, what was meant was "the operation of known physics about 4.5 billion years ago".

      Known physics is only a little more than 13.7 billion years old; that's less than an order of magnitude!

      (Also, I know you mean *locally* invariant, and are (reasonably) extending that in the weak field limit to a bigger region of spacetime, but you're extending too far if you can be read as saying that there is some global conservation of energy in the observable universe. The metric expansion of space, inflation, and the big bang are pretty good examples of violations of that. Moreover, enormous translations on the timelike axis are likely to run into new physics, certainly at the early boundary, and possibly in various spacetime regions in the future light cone.)

  12. Blame the conservationists by Roger+W+Moore · · Score: 1

    Ever since they passed all those laws requiring us to conserve energy we've been stuck with the same laws of physics.

  13. Wow!!! by gsslay · · Score: 1

    This article uses way too many exclamation points (I counted 12). Putting exclamation points at the end of every other paragraph doesn't automatically make something interesting and exciting. It just looks like the writer has no confidence in capturing the reader's attention without them!

  14. Question... by LongearedBat · · Score: 1

    Is Earth's magnetic field caused by the moon?

    1. Re:Question... by Anonymous Coward · · Score: 0

      The flow of liquid iron in Earth's outer core generates electric currents, which in turn produce magnetic fields. Heat and Coriolis force etc would be enough to cause the flow. However, tidal forces should also affect it to some degree that I don't know.

    2. Re:Question... by Anonymous Coward · · Score: 0

      Thank you.

      ~ LongearedBat

  15. Developer incompetence by Anonymous Coward · · Score: 0

    If you'd bothered to actually read the parent's point, it was about a site's static content.

    A web developer who requires browser-side Javascript to display content that is entirely static clearly doesn't understand the purpose of Javascript and doesn't know how to leverage plain HTML to make a site viewable by the widest possible audience. They're not doing their company any favours.

    If their management knew that their devs had deliberately chosen to make the company site invisible to anyone who has the commonsense to protect their browser, they'd get a damn good telling off or shown the street.

    1. Re:Developer incompetence by geantvert · · Score: 1

      I am not sure to see the relation between being static (or not) and running Javascript.

      Anyway, I would not qualify their page as being static so I guess that we probably do not have the same definition for that word.

      PS: I am not one of the two AC parents

  16. Gravitational locking already? by rgbatduke · · Score: 1

    Seriously? The moon is gravitationally locked now, sure, but the Earth (and moon) still being liquid/hot when it slowed to a lock? I don't think so. For this to be plausible the moon would have had to coalesce, in an orbit, with nearly zero spin angular momentum, which seems absurdly unlikely. Otherwise, like a bird on a rotisserie, it would have been "roasted" pretty much equally on both sides. So maybe, but I doubt it.

    --
    Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.
  17. Re:Please StopWithABang by thegarbz · · Score: 2

    But then StartsWithABank won't be able to feed his family. This isn't a Forbes problem, it's a Slashdot not standing up to submitters who submit every single one of their lame stories as front page news.

  18. Stop linking to Medium by thegarbz · · Score: 2

    Well I guess Slashdot did finally stop linking to Medium. Though it looks like StartsWithABang just moved his personal blog to Forbes and now reposts everything he writes from there.

  19. Repeal SLoTD! Now!! by 140Mandak262Jamuna · · Score: 1
    We freed the banking from the law of supply and demand and the profits of the financial sector have boomed to 25% of all profits earned by all enterprises. But still we are still hampered by rest of the economy saddled with physical process of delivering goods and services in the real world of Euclidean geometry and physics. Ages ago, before we understood the real cost of energy a small band of elite "scientists" passed all sorts of laws, "conservation of energy" "conservation of angular momentum" and the most egregious of all, the Second Law of Thermodynamics. Our economy has been straining at the yoke of these tyrannical laws.

    It is high time we repeal these draconian laws and free the economy to create more jobs and prosperity for all. We will form a committee of high powered lawyers and finance wizards to study the constitutionality of these laws, and we are planning to sue them to be declared unconstitutional and hence null and void. Our private assessment is that the John Roberts court will be sympathetic to our plea but timing is of the essence, we need to get the case in the docket while Scalia is still in office.

    We will not rest till the Finance sector takes home 98% of all profits earned in all endeavors.

    Confidential. Circulation strictly limited. For the eyes of finance executives only

    --
    sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
  20. Nothing new by blbordelon66 · · Score: 1

    This is old news. Really, really, really old news.

  21. Study is at best incomplete by Anonymous Coward · · Score: 0

    Its not just the radiant heat from the earth warming one side. The tidal pull works on any liquid, just like the tides work on earth. However the tidal pull on the moon is exclusively on one side. This would make it much more likely to liquid magma to be pulled to the near side of the moon, creating channels and volcanic fissures that would continue to pour liquid magma for a much longer period of time than the far side of the moon. This, more so than radiant heat, would explain why there are signs of lunar resurfacing at a much later time than on the far side of the moon.