Orbit

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Cyperium, Nov 25, 2007.

  1. Cyperium I'm always me Valued Senior Member

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    How can something stay in orbit for 4 billion years without either being sucked in or pushed out from centrifugal forces?

    Especially considering that mass has been added, and only a small change in mass will create a massive error in time, causing the earth to be sucked in if mass was added, and blown out if mass was taken away.

    Or are we that perfectly balanced that it can last so long, what about the other planets?

    The moon?

    Other satellites?
     
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  3. Avatar smoking revolver Valued Senior Member

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    The Moon is getting more distant from the Earth and the Earth actually is spinning towards the Sun.
    I don't remember the exact numbers though, but they are minute.
    The Earth will be long before swallowed by the Sun in its Red giant stage.
     
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  5. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Don't electrons orbit around a neutron? Aren't they older than 4 billion years?
     
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  7. kaneda Actual Cynic Registered Senior Member

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    After the formation of the solar system, which some believe was before the sun ignited, planets were sent into inner and outer orbits by slingshot effects from the giants, everything seems to have settled into orbits and with nothing acting on them since then, have stayed there. The Sun loses four million tons of mass per second but in it's lifetime has maybe lost one millionth of an Earth mass so not enough to gravitationally affect the planets in orbit around it.

    It is said that if you throw something in space it will travel in that speed and direction forever unless acted on by another force and seems to be the same for orbits.

    Electrons and nucleii work by some kind of atomic/magnetic fields since the nucleus is too small to have sufficient gravitational force to hold an electron in place. This energy is released in nuclear bombs.
     
  8. K.FLINT Devil's advocate :D Registered Senior Member

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    The ties that bind

    The reason to your question in it's simplest form is that all the planetary bodies { planets and moons } in our solar system hold EACH OTHER in place. Each pulls and pushes on the other as they spin as fast as they can, gravity is the forced that is push-n and pull-n. and its nothing but a big teter toter or maybe a tug of war take your pic of visuals.
     
  9. Janus58 Valued Senior Member

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    You seem to be operating under a quite common misconception: that in order to maintain a stable orbit, gravity and "centrifugal force" must be perfectly balanced. This not the case.

    To explain, imagine we have an object in a perfectly circuar orbit where such balance exists. We give it a little nudge so that it loses some of its orbital speed.
    At this point gravity wins the battle and the object begins to fall inward. As it does so, it begins to speed up as it exchanges potential energy for kinetic energy. At a certain point, balance returns. The object trajectory at this point is still taking it inward, so it continues fall; it "overshoots" the balance point. As it falls, it continues to gain speed, and the centrifugal effect increases until it stops the inward fall. At this point the centrifual effect is stronger than gravity and the object will begin to climb up. On its way up it will again overshoot the balance point and will continue to climb until it reaches the same point where we gave it its nudge, where it will have the same orbital speed as it had after we slowed it down. IOW, it starts to fall back in and repeats the cycle again. The object has entered a new eliptical orbit.

    If we add speed we get the same type of effect. The greater the change in speed the more elliptical the new orbit will be. The Earth's orbit is constantly changing its shape slighty due to the gravitational pulls of the other planets, but it never reaches the point where it will either falls out or fly off of its orbit.

    For a circular orbit (which the Earth's very nearly is) the amount of change in speed needed to cause the object to fly away frm the sun is about 41% of the object's orbital speed. In the case o fthe Earth, its orbital speed is just about 30 km/sec, meaning you would have to increases its velocity by 12km/sec to cuase it to fly off away from the Sun.

    To cause the Earth to fall into the Sun you have to remove nearly all of its orbital velocity. Since the nudges the Earth does receives come nowhere near this, the changes in its orbit are very small over time.

    As far as the mass question. Altering the Earth's mass would not alter its orbit. While doubling the Earth's mass would double that force of gravity between the Earth and Sun, it would also double the centrifugal effect and the two would maintain the same relative balance as before.
     
  10. Cyperium I'm always me Valued Senior Member

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    3,058
    Thank you for explaining that.

    Is there a higher risk for asteroids to hit the earth at the direction it is heading? Or do the asteroids sometimes catch up the earth?

    If there is a higher risk for asteroids to hit the earth at the direction it is heading then shouldn't they slow the earth significantly over billions of years?

    I can understand if the risk is equal (50/50) as it would balance out the change of speed to be roughly the same, but surely the risk must be slightly larger if the asteroid comes right at front, at least the asteroids speed in relation to the earth would be greater (thus slowing it down more than it could speed it up if it came from behind).


    Or perhaps the chances are slim as the asteroids are also in orbit, and most of them that could hit the earth from the front (direction of it's orbit) has allready done so...
     

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