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Thread: How do the Planets stay in orbit?

  1. #1

    How do the Planets stay in orbit?

    I know at first glance this may seem like a simple question...but it just doesn't make sense to me unless there is a force I am unaware of.

    I realize tha gravity of the sun constantly wants to pull the earth(and all planets for that matter) into it's center.
    I also realize that the momentum of orbit (centrifugal force) is in the process of attempting to fling the earth out into space away from the sun.

    So how is it that each and every planet is in such complete balance on this infinitely small line of being either sucked into the sun or flung out into space?

    There are so many variables that would dictate one or the other...but not this PERFECT speed that keeps the earth from doing either.

    The only way I can understand this is if perhaps each planet had a certain frequency or vibration which dictated it's distance from the sun.
    Much like the force that keeps the protons circling around the nucleus without collapsing or flinging outward.

    Any thoughts on this would be welcome.

  2. #2
    Planets stay in orbit due to gravitational influences. So the Sun keeps the planets in orbit around it, whilst the planets stabilize their distances as well in reference to each... Frame-Dragging also effects the locality of galactic objects as well.

  3. #3
    And then of course, as we get even bigger, we find that entire galaxies with strong Total Sum of Gravity, find themselves crashing into each other. We recently wittnessed such an event.

    Andromeda is moving relative to us at something like 300,000 miles per hour, and it might crash into our universe, just before our sun exhausts its fuel through nuclear therm-runnaway.

  4. #4
    Robbing the Shalebridge Cradle CptBork's Avatar
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    No orbit is 100% perfect- there are lots of tiny factors that come into play which over time will change the shape of orbits, but to very good approximation these orbits are perfect and repetitive, such as the ones in our solar system. What makes the difference between a planet being trapped by gravity and forced into orbit, instead of careening off into space, is the speed at which the planet is moving and the distance from sources of gravity. If a planet far off in space is moving too quickly, gravity will not be strong enough to force it into a closed orbit. If the planet is moving slowly enough, however, then it can be trapped in an orbit regardless of how far it is from the gravitational source. To be technical, when a planet has a positive value for the total potential and kinetic energy, it careens off into space. If the net sum is anything less than 0, the planet enters an orbit.

  5. #5
    Interesting cpt

  6. #6
    There used to be more planets in our solar system, but some of them crashed into each other. Since the planets were formed from matter already orbiting the sun, the planets kept that balance.

  7. #7
    Also a worthy point

  8. #8
    And there are well over 100 man-made devices orbiting the Earth... have we really sat down and consider their own tiny perturbations in spacetime?

    Recently, i heard that a spaceship entering space, left earth on a path which was mathematically incorrect, despite it moving in such a mysterious manner. I speculate that the oribiting devices we have around the earth, may have perturbated its trajectory.

    It's things like this, we need to take into account, because, even if the cause is small, it still has an effect.

  9. #9
    (But the latter doesn't apply to the quantum world, because [particles] do not follow necesserily the laws of cause and effect. They can by definition, experience the effect well before the cause. This is just another ''strangement'' of quantum mechanics.

  10. #10
    Robbing the Shalebridge Cradle CptBork's Avatar
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    The effect of gravitation from orbital devices or gravitational waves from moving through space are negligible when considering the paths of space probes. Even thermal leakage from a space probe would have a bigger effect on its motion than what you're proposing, along with a million other more important factors.

    To restate my earlier point, there's not one magic set of values a planet needs in order to maintain an orbit. Either it has enough kinetic energy to escape, and does (unless it's on a collision course), or it lacks sufficient kinetic energy, and orbits. If a giant space monster came and gave the earth a big shove, its orbit would change shape but it would still be an orbit. The reason some objects fall to the Earth or the sun and hit them is because the Earth and the sun are big fat balls of gas and rock that can collide with something orbiting too closely.

  11. #11
    I was however, and should have explained, that the man-made objects orbiting the earth, is not the only gravitational source which indeed, is quite small, so very small, we would hardly notice it. But we may add, or have to add, these tiny forces, with all the greater forces as well, such as the earth's gravitational field and spin and even frame-dragging itself.

  12. #12
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    Hello Reiku, et al.

    When I contemplate this question, I usually end up thinking about "time gradients" derived from GR and SR. After all the same "time rate" has been measured, with atomic clocks, at "sea level" everywhere on the Earth and the Earth has both gravity (GR) and centrifugal force (SR). Both GR and SR have "time" variables.

    BTW the Earth's polar radii is approximately 22km less than the equatorial radii.


  13. #13
    Robbing the Shalebridge Cradle CptBork's Avatar
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    Quote Originally Posted by Reiku View Post
    I was however, and should have explained, that the man-made objects orbiting the earth, is not the only gravitational source which indeed, is quite small, so very small, we would hardly notice it. But we may add, or have to add, these tiny forces, with all the greater forces as well, such as the earth's gravitational field and spin and even frame-dragging itself.
    I'll bet the gravity from the distribution of Africa's population probably has a bigger effect than all these forces you mention, at least in the case of Earth's gravity. Certainly, orbiting satellites would be the least of anyone's concerns when calculating gravity. It's truly negligible.

  14. #14
    It's just some food for thought, i thought anyway.

    Montec

    Yes, the effects are very noticable, even though they are small... i have the results from the basement experiment somewhere (Memory is quite blank right now on this thing), where the effect was very small, but it was still something noticable...

  15. #15
    Quote Originally Posted by CptBork View Post
    I'll bet the gravity from the distribution of Africa's population probably has a bigger effect than all these forces you mention, at least in the case of Earth's gravity. Certainly, orbiting satellites would be the least of anyone's concerns when calculating gravity. It's truly negligible.
    that would not be so
    the mass of the population of afric comes from the soil of africa(and wherever else their food comes from)

  16. #16
    oh god, there wouldnt BE any planets if they wernt in the right spots and orbiting at the right volocity

    So logically the other POTENTUAL planets were either thrown out of the solor system or eaten by the sun

  17. #17
    It's more likely Jupiter and Saturn absorbed other planets, rather than getting eaten by the sun. Whilst it is still probable what you said, for something to get through the path/trajectories of the planets in our solar system and reach the sun, is less probable, that a planitarian collision.

  18. #18
    you are right, i should have included that they got eaten by the forming planets but the point still stands, if they wernt in ballance they were delt with centures ago

  19. #19
    Yes your point is solid.

  20. #20
    Robbing the Shalebridge Cradle CptBork's Avatar
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    Quote Originally Posted by MR. Champagne View Post
    that would not be so
    the mass of the population of afric comes from the soil of africa(and wherever else their food comes from)
    And if 100 million of them decided to pack up and head north by any means possible? Would have a way bigger effect than a few orbiting satellites, even then it would probably be too small to measure the gravitational change with today's equipment.

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