planets moving closer to the sun?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Datura, Apr 11, 2004.

  1. Datura surrender to nothing Registered Senior Member

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    My boyfriend's roommate has a theory that the planets are moving closer to the sun and eventually Earth will become inhabitable and Mars will form life once it moves closer to the sun. Is this possible or no?
     
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  3. Faulty Ragged Rascal Registered Senior Member

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    Does he have a reason for this? It could happen if the Sun's gravitational field strength was increasing, or if the planets' orbital velocities diminished (due friction provided by an interplanetary medium, for example).

    In fact the Sun's gravitational field strength ought to be decreasing as the star very gradually loses mass. The very rarefied interplanetary/interstellar medium provides no significant resistance to planetary motion. I don't see how your boyfriend's roommate's theory could work.
     
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  5. Janus58 Valued Senior Member

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    At present, the Earth is moving in towards the sun at about .00000005 AU per century.
    Mars is moving in at .00007221 AU per century. Saturn, Neptune and Pluto are also moving in.
    Mercury, Venus, Jupiter, Uranus are moving out away.

    The eccentricities of the planets are also changing with time, some decreasing and some increasing, though the change in semimajor axis and eccentricity do not follow any connected pattern. (some planets that are moving in are decreasing eccentricity, while others are increasing)

    All these changes are due to Secular perturbations and do not remain constant. For instance, the Earth's eccentricity is decreasing at this time, but in 24,000 years it will start to increase again. In this time the average distance to the sun will only decrease by some 1800 km; very little when compare to the Earth's diameter (12000 km) not to mention the 4 million km the Planet moves in and out from the sun over the course of a year.
     
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  7. crabhaver Registered Member

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    So, I can assume by what you are saying, the sun will swallow the earth during it's red giant phase, 4 to 5 billion years from now, before the earth's minute degrading orbit will resolve into the outcome of the original question.
     
  8. Datura surrender to nothing Registered Senior Member

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    Thanks everyone. Faulty, I don't know his reasoning behind it. If you really want to know, I'd be happy to ask him and post it.
     
  9. TruthSeeker Fancy Virtual Reality Monkey Valued Senior Member

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    What he might be thinking of is that the sun will eventually become a red giant and expand itself enough for the earth to fall in it. But in tis case itwould be the sun expanding wheter then the earth gradually falling in...

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  10. Silverback Registered Senior Member

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    But by the time the sun expands to red giant, it will have lost enough mass to decrease its gravity (we are talking about a few Billion years here), thus the Earth (and the other planets) would be orbiting slightly farther out. Still close enough to be crispy, but not swallowed.
     
  11. Norman Atta Boy Registered Senior Member

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    Let us know when that happens so we leave that day "blank" on our calendars.....O.K.?
     
  12. Zarkov Banned Banned

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    >> a theory that the planets are moving closer to the sun

    Sorry other way around, the planets are moving away from the Sun, the moons are moving away from the planets.

    Venus will be the next Earth, Mars' fate is set for destructive break up once its core is totally frozen.
     
  13. Vortexx Skull & Bones Spokesman Registered Senior Member

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    Wasn't it that the moon gradually slows down the rotation of the earth and in turn the moon will move closer to us? This should also be the case with the planets slowing down the rotation of the sun, however the sun loses mass by radiation and there are the pertuberations and framedragging gravity effects, wich would all account for all sort of pro and con factors that would make our planets back and forth in time.

    But anyway, we will not go all the way to the sun, but a red sun will rather come to us, by that time we might have subtropical holiday resorts on mars and jupiters moons!
     
    Last edited: Apr 14, 2004
  14. Starthane Xyzth returns occasionally... Valued Senior Member

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    @ Silverback: yes, the Sun could lose up to half its mass during and after its red giant phase. Earth, though long ago sterilized and melted, will probably end up at an orbital radius similar to that of Mars today.

    @ Zarkov:If the Moon's tidal effect eventually slows Earth's rotation to the point of synchrony, where the Moon remains fixed over one side of the Earth like a communications satellite, then obviously the Lunar tidal process will freeze. However, the weaker Solar tides would still continue to slow the Earth's rotation - angular momentum will then be transferred to the Earth's orbit around the Sun, and Earth will begin to spiral outwards. (This would all be long after the Sun's red giant phase ended).

    What do you mean about planets breaking up once their cores freeze? I'm not familiar with that theory.

    Re. the original subject of this thread: in the REALLY distant cosmological future, planetary orbits will theoretically collapse due to gravitational radiation, which leaks away kinetic energy - on the order of 10^20 years. [See the thread on "Does a Body that radiates gravity lose mass?"]

    Before that, though, random encounters between the dead stars will have stripped most planets away from their suns.
     
  15. TruthSeeker Fancy Virtual Reality Monkey Valued Senior Member

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    What are you talking about when you say decreasing gravity? Most of the mass of a read giant is concentrated in the core, where all the CNO is. This core would have a density of 10<sup>6</sup>g/cm<sup>3</sup>, compared to the present stage which is 150g/cm<sup>3</sup>! After the Helium flash and after the sun becoming an RR Lyra, the outer envelope will pulsate at least twice a day and will slowly throw away its outer envelope into space creating a planetary nebula. Still, that will be only a small percentage of the mass compared with the core which is way massive then the rest of the star.

    In other words... how come will the gravity decrease if we will have a white dwarf in the place of the sun?

    Also, just as a comparison, Betelgeuse has a radius 150 times bigger then the sun. The distance from the sun to earth is about 150,000,000km and its diameter is about 1,309,000km. If the sun becomes like Betelgeuse and expand to a size of 150 times the present size, the earth would be just inside the sun, since the diameter of the sun would be bigger then the distance from the sun to earth. The diameter would be at least 150,000,000km, exactly the distance between them. Of course, this is just a comparison, since the sun has a mass of 1M<sub>o</sub> and Betelgeuse has a mass of 15M<sub>o</sub>, but you still can expect the sun to be way bigger then it is right now...

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  16. TruthSeeker Fancy Virtual Reality Monkey Valued Senior Member

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    Huuhh... RR Lyrae can be beautiful, but I have the slight impression that we will need suntain lotion... particularly when the sun star shooting out its outer envelope in our direction...

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  17. Zarkov Banned Banned

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    >> to slow the Earth's rotation - angular momentum will then be transferred to the Earth's orbit around the Sun, and Earth will begin to spiral outwards.

    sorry to pursue the wrong subject but Starthane Xyzth, not sure that the above is logically correct.
    Certainly the larger the orbit the slower the tangential velocity of a planet and this is a constant relation rv^2, so loss of kinetic energy would actually cause the planet to spiral into the Sun, ( a satellite slowed by the atmosphere is lost to the Earth)

    SO there is no gain or loss of kinetic energy, but the distance defines the change in the velocity, so there is a gain of electrical energy in every orbit (= time), caused by electric charge separation, IMO

    >> Re. the original subject of this thread: in the REALLY distant cosmological future, planetary orbits will theoretically collapse due to gravitational radiation, which leaks away kinetic energy - on the order of 10^20 years. [See the thread on "Does a Body that radiates gravity lose mass?"]

    Thanks, these thoughts are intimately intertwined, eg does a magnet lose weight?
    In Electrodynamic spin gravity theory, gravity is the resultant induced by non inertial acceleration of a body in a crossed centric electric-magnetic field. Magnetic fields will cause contraction of distances between objects, while polarised electric fields will cause an expansion of distances. The characteristics of equilibrium are in what we see.

    BUT separated electric fields shield each other and remix with each other (leak) so once the source of charge separation is removed all matter will contract to each other.

    So as long as the Sun has the appropriate output then all solar objects will move away from each other but eventually magnetism will win, once the Sun has ceased sufficient output to maintain an outward pressure on the solar object, the solar bodies will all eventually join the Sun again.

    Re the core solidification.. well 'magnetic-electric tidal forces' if present break up the mantle and the core will be set on a different parth. From my calculations the planet expands in size until the value of the surface geomagnetic force is within a narrow range.

    my understanding

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  18. Pete It's not rocket surgery Moderator

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    Zarkov,
    Do you claim that the orbital radius of all planets is currently and always increasing?
    Do you claim that the orbital radius of all moons is currently and always increasing?
     
  19. Zarkov Banned Banned

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    >> Do you claim that the orbital radius of all planets is currently and always increasing?

    The observed averaged orbital tangential velocities of solar bodies is at or above the theoretical orbital velocities for these bodies. The Moon is measured to be receeding from the Earth. For most of the moons of other planets, they are theoretically receeding.
    The solar planets show little discrepency, but I expect they would receed rather slowly.
    my analysis


    >> Do you claim that the orbital radius of all moons is currently and always increasing?

    see above, EXCEPT the moons of Mars and maybe one of Jupiter. They show a depressed tangential velocity. This could be due to electric shielding.

    I postulate that the positive outer electric charge of all electrically isolated bodies is increased by the Solar output. Of course this implies that the planetary system is born from the Sun (or planets) and they spiral out until the source of charge separation is extinguished and then the bodies spiral inwards towards the Sun.

    Just my model

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  20. zonabi free thinker Registered Senior Member

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    arent the planets mars and venus creeping back close to where we are currently?
    traffic jam. also couldnt the earth be attracted towards the sun if an object with gravitational mass came into the solar system in the direction of the sun.

    i think he is onto something but might have some facts twisted. or maybe i do heh
     
  21. Janus58 Valued Senior Member

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    This is due to tidal interaction between the Earth and Moon. As the lunar tidal bulge slows the Earth's rotation, the Earth transfers angular momentum to the moon, lifting it to a higher orbit.

    Quite a few Jovian moons are decreasing orbital distance, Metis, Adrastra, and all of the recently found moons that orbit in retrograde.

    Most of Uranian moons orbit in retrograde to Uranus' rotation, so they also are approaching.

    Five of Neptune's moons are approaching, because, while they orbit directly, they have orbital periods smaller that Neptune's rotational period.

    These are all due to tidal interaction between the Planet and moon. If a moon either orbits retrograde to the planet's rotation, or orbits directly faster than the planet rotates it will move in towards the planet.
     
  22. Janus58 Valued Senior Member

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    Actually, the Lunar tidal process will not end there. As the Solar tide begins the slow the Earth's rotation, the moon will then start to orbit a little faster than the Earth. As this happens, the lunar tidal bulge will start to move again. But this time, instead of slowing the Earth, it will try to speed it up again to match the moon. It won't quite succeed due to the solar tidal drag, and the Earth's rotation will always lag a little behind the moon. Due to the resulting tidal interaction, the moon will spiral in towards the Earth until it reaches the Roche limit and breaks up.
     
  23. Starthane Xyzth returns occasionally... Valued Senior Member

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    Like Janus58, I was refering to a loss of angular momentum from the Earth's rotation: I guess that to call it "kinetic energy" is inaccurate. Sorry. The Earth can't lose angular momentum without it being gained somewhere else in the Earth-Moon-Sun system; if it is transfered to the orbital motion, then Earth's distance from the Sun will increase, via rv^2 as you said.
     

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