planets moving closer to the sun?

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

  1. Starthane Xyzth returns occasionally... Valued Senior Member

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    Oh - and do you have a link to your Electrodynamic spin gravity theory, Zarkov?

    @Janus58: are you saying that ALL satellites with a retrograde orbit are slowly approaching their primaries? (That would also include Phoebe, the outermost satellite of Saturn). If the reason is the motion of the tidal bulges those satellites cause on the said primaries, it must be infinitesimally small with most of them: I don't think Adrastea or Metis, for example, can generate any appreciable tides in the liquid mantle of Jupiter!

    The contrast in heating between the day and night sides of a planet would have more effect on its rotation than the tidal effect of such minor satellites.
     
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  3. Janus58 Valued Senior Member

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    But they still will have an effect, even if only very small. Off course, in complex systems like the those of Jupiter and Saturn, you are going to have all kinds of perturbations to account for, some of which will cause individual moons to move in or out regardless of what the tidal effect is trying to do.(Just look at the solar system; all the planets orbit directly and with longer periods than the sun's rotation, yet some are presently moving in and some are moving out.)
     
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  5. Janus58 Valued Senior Member

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    The Earth's kinetic energy lays in two forms, the KE due to its orbital velocity and the KE due to its rotatation around its axis.

    The earth's total orbital energy is equal to its KE due to orbital velocity plus its gravitational potential energy(GPE) this is expressed in by the formula

    E = mv^2/2 - GMm/r

    (GPE is negative, so we have the minus symbol)

    Since v (the orbital velocity) can be found by

    v = sqrt(GM/r)

    Through substitution we can get

    E = -GMm/2r

    As the Earth slows its rotation, it loses kinetic energy, but its total energy stays the same, so this energy is converted to orbital energy.

    thus -GMm/2r must get larger, and the only value that can change is r. In order for the orbital energy to get larger, r must get larger (Thus driving the Orbital energy less negative.)

    As a result, the Earth moves into a higher orbit, Since higher orbits also have lower orbital speeds, the Earth also loses kinetic energy in this form.

    Even though the Earth loses kinetic energy, the gain in GPE caused by moving away from the sun offsets this.
     
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  7. Arcadea9 Registered Member

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    There is a giant misunderstand in the general population's understand of Mars and its nature. Mars indeed shares many features of Earth and may, at one time, had microsopic forms of life. However today, even if it was in the same solar position as us, it could not.

    Mars has only 10% of the mass of the earth and proptionally less gravity, thus larger organisms would have a fundemental problem of staying on the planets surface. However, even if life did manage to stay on its surface through evolution, they would be able to survive the very bitter cold that would be on Mars at night and especially during its 6 months of winter. You see, because of the lack of mass, and thus gravity, mars has very little atmosphere compared to earth. Thus, heat cannot stay trapped as much or as long as it can on earth.

    This is one theroized reason to why the water that may have been on mars at on point is now all ice at its polls. Overtime, as more and more atmosphere escaped into space, the planet grew colder, and colder, until it is what it is today.

    Earth itself is also loseing its atmosphere. Notice that there is no hydrogen or helium in our atmosphere. It is not because it somehow changed forms and is now on the planet's surface. Over the billions of years of the earths existence, hydrogen and helium slowly escaped from our atmosphere, leaving the heavier elements in its place, i.e., carbon dioxide, nitrogen, etc.

    Jupiter, due to its large mass, still has much of the same gas that was around even at its creation!

    To be honest, Mars is more like a over sized moon than an actual planet. So to answer your question, no, even if mars was where we were, life would not exist (or to be more accurate, over time, as mars lost more and more of its atmosphere, life would cease to exist).
     
  8. Communist Hamster Cricetulus griseus leninus Valued Senior Member

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    Good points, but a bump. I disagree with Mars being more like a moon than a planet though. A very intelligent post overall though, WELCOM TO SCIFOUMS!
     
  9. emusquire Registered Senior Member

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    As the sun expands it will engulf the planets eventually exploding into a supernova.
     
  10. Pete It's not rocket surgery Moderator

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    Hi emusquire, and welcome to the forums.
    Are you sure about that? You'll find that at sciforums, it pays to check your facts before posting.
     
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  11. kevinalm Registered Senior Member

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    I believe that should be when the sun switches over to helium burning and expands to a red giant. Most texts suggest it will engulf everthing out to the asteroid belt.
     
  12. Communist Hamster Cricetulus griseus leninus Valued Senior Member

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    It varies, that distance. SOme say it won't even reach Earth, perhaps Venus and definitely Mercury but not Earth
     
  13. orcot Valued Senior Member

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    I heard that if the sun would become a red giant right now then the earth would be swallopt,
    but because the sun is losing mass by solar radiation and later on will expell it's outer layer's. It will loose a considerbly enofpart of it's mass. So the earth would move in a bigger orbit.
     
  14. Muslim Immortal Valued Senior Member

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    It is pretty possible that might not even happen, the earth might not actually be engulfed by the sun. Although all this is just speculation, there is no hard evidence to support which one of the two will happen. On a personal note I believe we will end up in the sun. As its already mentioned in the Qu'ran.
     
  15. addyboy Registered Member

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    check it

    As the moon goes around earth so the earth goes around the sun. so according to the great law of physics what happens with one does happen with the other too.

    which implies

    slowing of moons rotation will tke it away from earth and slowing of earths rotation will take it away from sun.

    the earths rotation is slowing since we add o.1 sec extra every 2-3 years at the new year to keep our atomic clocks correct (I can also prove it mathematically if someone needs). so it is moving away from Sun and thus if it is moving away from sun it will never fall into it. similarly other planets are also moving away from sun.

    One last thing all this has completely nothing to do anything with electricity or magnetism.
     
  16. eburacum45 Valued Senior Member

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    I'm sure I posted this link recently; in any case, here it is again.
    http://www.astronomy.ohio-state.edu/~pogge/Lectures/vistas97.html

    The Sun constantly loses mass because of the solar wind and other effects; gradually the Earth and other planets will move outward.
     
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  17. Janus58 Valued Senior Member

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    It is actually the slowing of Earth's rotation that is causing the Moon to move away from the Earth. Due to tidal interaction, the Earth is transfering angular momentum to the Moon.
    Just to clarify, the leap second we add every couple of years does not mean that Earth's rotation slows by that much over that period. IOW just because we added a leap second in 1987 and then another in 1989 does not mean that the Earth took 1 sec longer to complete a rotation in 1989 than it did in 1987. The leap second is to compensate for the fact that the standard length of a sec was established as 1/86400 of a solar day back in the 1800's. Since then, the length of the Solar day has increased by about 2 milliseconds. This 2 ms per day accumulates until it equals a difference of 1 sec. Then we add a leap second to keep standard time in sync with the Solar day. Also, since the rate of rotation for the Earth varies due to a number of factors, the addition of leap seconds are not on a fixed schedule. For instance, we had leap seconds added in 1992,1993 and 1994, but the last leap second added was in 2005.
    Just to be clear, I am not accusing you of making this error, I'm just clarifying so that other don't jump to the wrong conclusion.
    Many factors effect whether a palanet is moving in towards or away from the Sun during any given time period. For instance, for the present epoch, Jupiter, Saturn and Pluto are decreasing their average distance form the Sun, And while during the period of 1800 AD - 2050 AD, the Earth's average distance from the Sun is increases by 0.00000562 AU/century, during the period of 3000 BC - 3000 AD, the Earth's average distance decreases[i/] by -0.00000003 AU/century.
    Agreed.
     
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  18. Measuring the distance is difficult. A well known fact, sure to be talked down, is average orbit distance, from assumed timing.

    Our course is not constant. No 2d. The Sun's main influence is bodies nearly as large, or larger, and things like neutron stars. It really does vary a great deal.
     
  19. eburacum45 Valued Senior Member

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    I have recently learnt something which indicates that I was probably wrong in earlier posts on this subject- the Earth, and all the planets out to Jupiter, will probably spiral into the Sun at a late stage in its evolution.

    The Sun in fact turns into a red giant at two separate points in its life history; the second time it ends up on the Asymptotic Giant Branch, and will probably put out so much material in its solar wind that the planets will be braked by friction, quite quickly falling into the star.
     
  20. D H Some other guy Valued Senior Member

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    The tides are the primary mechanism by which transfer the Moon and Earth transfer rotational angular momentum to orbital angular momentum. The same happens with the Sun and Earth but to a much lesser extent. Just as the Sun raises tides on the Earth, so does the Earth raise tides on the Sun.

    The Sun currently rotates faster than the Earth orbits the Sun. This will not always be the case. The solar wind takes angular momentum from the Sun, and does so faster than it takes mass from the Sun. This angular momentum loss will be compounded when the sun expands into a red giant. By that time, the sun will be rotating slower than the earth's orbital rate. The Sun-Earth system will transfer angular from the Earth's orbit to the Sun. The Earth will spiral into the Sun a long, long time from now. Note that this will not be a great feat because the Sun will be a lot bigger than it is a long, long time from now.

    Another factor in the late evolution of the Sun will help the decay of the Earth's orbit. When the Sun expands into a red giant the Earth will orbit through the Sun's upper atmosphere. Just as satellites in low Earth orbit decay due to atmospheric drag (e.g., that satellite that was just "shot down"), so will the Earth's orbit decay as the heliosphere becomes denser.

    A paper that examines these factors was recently accepted for publication in the Monthly Notices of the Royal Astronomical Society. The paper was recently posted at arXiv; link here.
     
  21. adamalden Registered Member

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    these are my theories...

    Theory one :

    The sun formed the planets one by one. This proccess can be compared to a human deficating. Once the human is ready to deficate he or she with tence up forcing the planet out. Apon the suns tencing up its gravity weakens as it sends a nice molten blob out into space. Gravity soon returns to normal. It is in this way the planets are spaced in like they are.

    Theory two :

    When a sun is formed planets are formed. Everything about the galexy is determined by this proccess. I beleive that black holes are created by god. The black holes suck up a hole bunch of crap and eventually expload... And if you haven't noticed black holes look pretty swirly so I bet thats why the planets circle the sun and dont just get sucked back into it. Black holes... Anyways. I think that the planets will all eventually be sucked into the sun... Each planet has its chance to spawn life when it reaches it's optimal distance from the sun. Earth made life... So we will either fire ourselves out into space and move to pluto or we will just die when the earth gets to close to the sun. OR we can set up huges jet engines around the equator that will fire at exactly noon every day untill we are back in our normal position. Once mars gets close enough to us we will blow it up. Just kidding. We will most likely bring life there as it will be in the right range to support it. By then we will have already blown up the planets that are closest to the sun because that's cool. But until that time we are ok. This wont happen for 400 trillion years...

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  22. Xylene Valued Senior Member

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    The sun is losing ca 4 million tons of mass per second, by converting 616 million tons of hydrogen into 612 million tons of helium in the fusion process. As the sun loses mass, it loses gravitational force very gradually; therefore the planets move out from it. Also, the sun's rotation rate is slowing down very gradually as well; as that happens, the angular momentum of the sun is transferred to the planets, and they move away.

    In just the same way, the Earth is moving more slowly now than it was when the Moon formed, because of the obvious tidal effect. Hence, the Earth is losing angular momentum to the Moon, which is moving away from Earth at about 2 inches per year (I got that statistic from an article written by Isaac Asimov, so if it's wrong, I'm not to blame

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

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    This thread is doing well. It has been regularly resurrected over 5 years now.

    That's an old idea. Physicists have shown that things can't work that way.

    That's more or less the currently accepted theory - that the Sun and planets formed at around the same time, condensing out of the same dust cloud.

    Why do you believe that?

    Nobody has ever seen a black hole explode. Why do you think they explode?

    Planets circle the sun because black holes look swirly? Hmm... interesting theory, but I think you're probably wrong.

    By what process?

    You'd need to actually launch stuff into space. A jet engine wouldn't do the trick. Also, do you know how heavy the Earth is? It has a mass of 6,000,000,000,000,000,000,000,000 kilograms. Do you really think a few jet engines would be able to move it significantly?

    Do you write many sci-fi stories at school?
     
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