Is Earth's orbit decaying?

Discussion in 'Physics & Math' started by wesmorris, Jun 3, 2003.

  1. ryans Come to see me about a dog hey Registered Senior Member

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    Maybe Venus was home to an ancient civilisation that endowed itself in nuclear winter, with the nukes all fired in the same diraection thus imparting angular momentum to it. It would certainly explain why there are so many clouds there and why there was a sudden burst of life on earth that many millions of years ago (the ones that survived came here). I thought that since crack pottery is the taste of the month, I might have ago at my own crackpot theory and see how many of you I convince. You know you will never be able to prove me wrong.
     
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  3. ElectricFetus Sanity going, going, gone Valued Senior Member

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    Actually Venus and Mercury have very slow rotations, it seems that only mars and earth have high-speed rotations… Earths case can easily be blamed on the world colliding impact that formed are moon and modern earth. Mars also sustain heavy impacts but nothing that harsh.

    The inner planets are very slowly falling into the sun, the outer planets are very slowly moving away. Why? I don’t know, this is just something I read out of a astronomy book some time ago.
     
    Last edited: Jun 12, 2003
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  5. ElectricFetus Sanity going, going, gone Valued Senior Member

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    by the way ryan we can prove you wrong: the amount of nukes needed turn its rotation backwards would have blown venus in half!
     
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  7. NileQueen Registered Senior Member

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    So if the core of a planet is solid, it is going to slow down? No...I think Mars does not have an active core, does it? And it takes 24.6 Earth days to spin a day, and 687 Earth days to make a revolution around the sun.
    Wait, it seems Mars has a liquid core: March 2003 news
    http://www.space.com/scienceastronomy/mars_core_030306.html
    "Additional information for the study came from previous measurements of the precession of Mars' rotation. Like Earth, the Red Planet's axis of rotation is not steady, but instead proscribes an imaginary cone-shaped feature in space as it shifts over time.

    It takes 170,000 years for the Martian axis to make one revolution, Konopliv said, effectively drawing a circle on some imaginary plane above the pole. "The precession rate indicates how much the mass of Mars is concentrated toward the center. A faster precession rate indicates a larger dense core compared."

    In addition to iron, the new study indicates there is also some lighter element in the core, possibly sulfur, Yoder told SPACE.com. The study also pinned the core's radius down to between 945 and 1,143 miles (1,520 and 1,840 kilometers)."

    Mars is a rikwid creechuh. But it doesn't have a dynamo like Earth does.

    A body in motion tends to stay in motion, a body at rest tends to remain at rest. Maybe Venus never really got started moving....

    Or being so much closer to the sun, maybe the sun's magnetic field has slowed their spin. Could it be a magnetic rather than a friction cause?
     
  8. Janus58 Valued Senior Member

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    Re: Even more answers.

    The actual outward movement of the Earth would be caused by the Earth's tidal effect on the Sun. (Just like the outward drift of the Moon is due to the Moon's tidal effect on the Earth.)

    This effect would be very small and such a drift would be very slow.

    But his does bring up an interesting point: The tidal locking of the Earth with the Sun. This would be pretty straight forward (Assuming there was enough time for it to happen), with the Earth slowly losing rotational speed until it matched its period of revolution. There is one fly in the ointment however, the Moon.

    Right now, both the Moon and sun work to slow the Earth's rotation, and eventually the Earth's Rotation will match that of the moon's period. But what happens then?

    The Sun will continue to try to slow the Earth. But as it does, this means that the Earth will rotate slower than the moon's period. This means the Tidal action between the Earth and Moon will begin to tug the Moons backwards in its orbit, as it now tugs it forward. The moon will begin to impart some of it's angular momentum back to the Earth, trying to speed up the Earth's rotation while falling into a lower orbit.

    Now at first, the moon will have moved far enough away from the Earth that the Sun will win, and the Earth will continue to slow. But as the Moon falls into a lower and lower (and faster and faster) orbit, Its tidal influence will increase and eventually surpass that of the Sun. The Earth would begin to speed up again trying to catch up with the Moon.

    The moon would continue to drift further and futher inwards. The interesting question is how far? Will it drop below the Rouche limit and break up? (In which case, the Earth will develop a ring system. ) Or will a new equilibrium state be reached with the Earth and moon tidally locked again?
     
  9. Lazybbones Registered Member

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    Hi. I'm getting in on the end of the conversation, probably and a little late at that no doubt. I'm no scientist, but I've thought long and hard about this. Thinking only about the Sun and earth, here, if you look at a diagram of earth's orbit, recall that the sun rotates like the planets do. I believe it is something like 26 hours it takes for the sun to orbit once. My theory is that the earth falls under the influence, not only of gravitational pull, but also of what I call centrifugal throw. Imagine a boy with a yo-yo at the end of its string, but not spinning up and down, just hanging there. He starts twirling the yo-yo around in a circle around his finger, out of boredom. The sun's gravitational pull is the "string" and the sun's spinning is the boy moving his finger around in a circle, which is what keeps the string taut. I am a creationist, and I believe God made all these objects with the exact right mass, in order for such perfect balance to exist for this long. A diagram here on the internet shows the orbit of earth to be almost circular; just slightly elliptical, and tries to explain how the "ellipticalness" of the orbit, combined with the mass of the orbiting object is what keeps it going. I personally believe earth's mass is not enough by itself to keep it going this long; especially since our orbit is very nearly circular. This would explain a phenomenon we see once in awhile, when a meteor falls out of the sky, and it glows as it falls through our atmosphere; you ever see that before? How does it fall? Straight down? No, it always comes in at an angle, if you've ever noticed it. Why? because it fell under the same two influences - gravitational pull and centrifugal "throw", and came down in a long spiral. By contrast, look at the moon and its many pock marks and meteor hits. The moon rotates once every, what, 28 days or so? That's almost not rotating at all. There's gravitational pull, but no centrifugal "throw", and meteors apparently come straight down. The falling objects have very little mass, so this "throw" action can not influence then outward into an orbit, so they fall. Earth has some mass for the sun's gravity to act upon, so this "throw" action keeps us out here where we bel0ng. I personally believe if the sun were spinning fast, like a quasar, any planets would be thrown far out into space. If the sun were spinning much slower, or not at all, the planets would have plummeted into it long ago. Anyhow, I don't know if that is any help at all, but as Stan Laurel would say, "that's my story, and I'm stuck with it."
     
  10. Lazybbones Registered Member

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    My next one to work on is comets, and rogue, maverick asteroids. I can't figure those at all. However, like I said, i am a creationist, and I believe there are many things about His vast, wonderful universe we simply will never figure out.
     
  11. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Being a creationist eh? Thought creationist HAD the universe figured out - god did it

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  12. sideshowbob Sorry, wrong number. Valued Senior Member

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    Yeah, we know the creationist theme song, "There are some things that just can't be explained - so here's the explanation."
     
  13. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Energy cannot be made or destroyed as the saying goes what can happen is energy is converted from one form to another with 100% efficiency

    However that 100% is not made up into 100% of the other energy

    I'm going into the realm of making up examples purely for illustration

    At the age of about 14 / 15 I invented the Perpetual Motion machine. My joy in doing so lasted about 30 seconds

    The science class I was in was in were learning about electrical motors and generators. Bamm - connect a generator to an electric motor - connect that electric motor back to the generator vola perpetual motion machine

    Then came the teachers explanation why not so. While true most of the generated electrical power would keep generator running some of the power would be bleed off as heat through the connected wire

    Same applies to a meteor crashing into the moon, most (?) of the kinetic energy goes to moving the moon while the rest goes to heating the moon at the crash site due to the friction between the moon surface material and the meteor material

    So since energy cannot be created or destroyed how about being rendered irrelevant (moot)

    One of the theories of how the Universe will end is called the Heat Death. This occurs when the expansion of the Universe has expanded so much no interaction can occur between two parts of the Universe

    No interaction no energy conversion. Is no possibility of interaction the same as destruction of energy? The energy (potential) is still present in the motion of the bits of the Universe flying away from the other bits but rendered moot since no work can be performed

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  14. James R Just this guy, you know? Staff Member

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    Lazybones:

    You're no scientist, but you're confident, based on your long and hard thinking, that all the scientists are missing something in the description of planetary orbits, and have continued to miss that important thing for the past 400 years or so. I see.
    Apart from the fact that your "centrifugal throw" seems to have no particular mechanism for affecting planetary orbits, there is a complete lack of any attempt on your part to quantify the force (or whatever it is) caused by your proposed "throw" effect. This is not how long and hard scientific thought is usually done - imagining a story that sounds like it might fit your (possibly incorrect) ideas about planetary motion and then doing nothing to try to test (falsify) your idea.
    Meanwhile, actual science shows, to a high degree of accuracy, that no force other than the Sun's gravity (perturbed slightly by gravitational pulls of other bodies in the solar system) is needed to explain the Earth's orbit around the Sun.
    What you believe about God seems completely irrelevant to this discussion. I can tell you, though, that planetary orbits balance themselves nicely, for scientific reasons. The solar system is not, in fact, indefinitely stable, but it's only unstable over extremely long periods of time.
    Elliptical orbits are the rule rather than the exception for planets and other astronomical bodies. Creationists used to believe that the orbits of the planets must be perfect circles, due to God's perfect plan for his Creation and so on. These days, they are forced to face the fact that the orbits are actually elliptical - a fact that was first recognised back in the 1600s by Kepler. Nothing special is needed to make an orbit elliptical. It's more the other way around: things have to happen to circularise an orbit.

    Also, it sort of sounds like you think something is needed to "keep [the orbit] going". That idea left science with Newton, also back in 1600s. Maybe another Creationist piece of misinformation?
    Where did you get the idea that something is required to keep the Earth moving along its orbit?
    Most meteors come from the middle of the solar system, where they are already in orbit around the Sun. They don't fall from rest towards the Earth. But even if we were to assume that meteors hitting the Earth have velocities in random directions, it would still be extraordinarily rare to see a meteor heading "straight down" towards the ground. It's just a matter of your viewing angle relative to where the meteor happens to be entering the atmosphere.
    The Moon rotates once every time it goes around the Earth. That's why the same side always faces us. The reason it is synchronised in this way is due to "tidal locking".
    It's not true that you'd see meteors on the Moon come "straight down" any more than you do on Earth.
    Did you know that the acceleration of a falling object does not depend on on its mass (unless air resistance is significant)? All objects near the Earth's surface fall at approximately the same rate. Do the experiment yourself. Take two objects: a heavy one and a light one, and drop them from the same height. They will hit the ground at the same time, unless one of them experiences more air resistance than the other. Their masses don't matter.
    You have yet to suggest any reason why the Sun's spin would affect the gravitational force it exerts on a planet or other object in the solar system.

    The question arises, then: why do you "personally believe" what you believe? Just because the idea appeals to you - you wish it to be true?

    This isn't how science is done. "Creation science" maybe.

    Do you think that spin has something to do with gravity, in general? It doesn't.

    Why doesn't the Moon plummet into the Earth? After all, the Earth rotates only once every 24 hours. If the Earth's spin is needed to keep the Moon up in the sky, how much spin is needed? Do you think the Moon would fall if the Earth stopped spinning? Why?
     
  15. wesmorris Nerd Overlord - we(s):1 of N Valued Senior Member

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    wow, a 19 year old thread. I so very forgot I ever asked this question, but yeah that sounds like some dumb shit I would have asked. i just happened to stumble in here after not participating for I don' t know how long and wow, nostalgia!
     
  16. James R Just this guy, you know? Staff Member

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    Long time no see, wesmorris.
     
  17. Dicart Registered Senior Member

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    You can also think the trajectory of the planets as if related to their 4-density.
    Technicaly speaking this is the alike of the mass of the photon.

    So, planets can not fall into the sun nor interchange their orbits.

    A simple way to understand is to visualise a liquid with high to low density (high as you approach the sun and low as you exit the heliosphere).
    The planets will remain where their "density" is alike the density of this "liquid".
     
  18. James R Just this guy, you know? Staff Member

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    This nonsense is off-topic for this thread. Please try to post on topic in future. Thanks.
     
  19. Dicart Registered Senior Member

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    I was only giving the obvious answer.
    But ok, please only understand this as a possible (exotic) mean to understand why and how planets remain at orbit.
     
  20. DaveC426913 Valued Senior Member

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    Never mind that it doesn't explain anything, you don't even have the facts straight.

    Earth is more dense than both Venus and Mercury.
    Neptune and Uranus are both significantly more dense than Saturn.
     
  21. James R Just this guy, you know? Staff Member

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    Obvious to you, perhaps.
    By "exotic", you mean "wrong", I take it.
     
    Last edited: Jun 13, 2022
  22. Dicart Registered Senior Member

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    Sure...

    Did you understand the 4-density claim ?
    No. Surely.
    And you are arguing "all is wrong" ??!!!
    I am laugthing, like a crow could do...
     
  23. sculptor Valued Senior Member

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    intro:
    Circa a couple decades ago, while visiting my son who was in the peace corps in Ecuador, I found myself standing on the top of a mountain hurtling toward the east at over a thousand miles an hour: with no sensation of motion.
    Which made inculcating the false notion of stasis all too easy.
    OK
    I ain't completely confused yet(but I am working on it)
    Let us proceed:
    Given that the earth revolves around the sun at about 67 thousand miles an hour.
    And that the solar system revolves around the galaxy at about 447,000 mph, while bobbing up and down/in and out of our galactic arm
    And that the galaxy is moving toward the great attractor at about 1.37 million miles per hour
    OK
    Our solar system is slightly(63 degrees) out of line with the plane of the galaxy
    OK
    It seems that everything is in motion
    except, perhaps our descriptors?
    That being said is "Orbit" the best descriptor for out motion around the sun?
     

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