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Thread: plz help on understanding tides and conservation of energy

  1. #1 plz help on understanding tides and conservation of energy 
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    all right tides make the earth slow donw in its rotation as heat is realesed in this energy transformation

    as the earth slows down the moon gains altitude by conservation of angular momentum

    but eventually due to slight atmospheric friction the moons loses altitude

    being an isolated system by conservation of angular momentum earth speeds up as the moon loses momentum which is transferred to earth as conservation of momentum states

    then tides make the earth slow donw in its rotation as heat is realesed in this energy transformation

    as the earth slows down the moon gains altitude by conservation of angular momentum

    ...

    so hows energy exactly conserved?

    the amount of kinetic energy is conserved but in its transformations releases heat

    or kinetic enery is transformed into heat to be transformed into kinetic enery is transformed into heat to be transformed into heat making life go on on and on?


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  3. #2  
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    Quote Originally Posted by luxtpm View Post

    but eventually due to slight atmospheric friction the moons loses altitude
    Wrong. It continually moves away. By an inch or so each year. We've been tracking it precisely since 1969 when the astronauts placed laser reflectors there. It agrees perfectly with the real scientific predictions.

    But i suppose you don't believe we landed on the moon either


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  4. #3  
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    Quote Originally Posted by luxtpm View Post
    but eventually due to slight atmospheric friction the moons loses altitude
    How much atmospheric friction do you think there is at 385,000km? (Clue: none)

    There is no sharp boundary to the atmosphere but 100km seems a good limit: Outer space - Wikipedia, the free encyclopedia

    This is cool: Moon and Earth, sizes and distances to scale.

    (From File:Earth-Moon.png - Wikipedia, the free encyclopedia)
    ei incumbit probatio qui dicit, non qui negat
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  5. #4  
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    so are you suggesting there theres absolute vacuum?

    so what if the people of this planet with the tidal energy transform solid into gas in order to extend the atmosphere?

    then the moon would fall with which earth speeds up with which you obtain energy to make atmosphere so the moon falls so earth speeds up

    i see this as a good example i will teach when i get my degree in whcih energy is conserved but its sucesive transformations make life and everything go on and on
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  6. #5  
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    This post makes no sense at all.
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  7. #6  
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    man have you noticed how many times you say the word sense

    what would freid say?

    are you afraid of life not making sense for you?
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  8. #7  
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    "the amount of kinetic energy is conserved but in its transformations releases heat"

    Why did you say that?
    Meteorologist/Naturalist & Retired Soldier
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    well the other option isnt less wilder actually

    kinetic energy transforms into heat energy which transforms into kinetic energy

    and while it does evrything goes on forever on many different ways

    sounds like conservation of energy makes the universe some kind of perpetuum mobile by definition of conservation of energy

    take my moon example

    tides decelerates earth which makes moon gain potential energy

    but this has generated heat so the atmosphere extends

    so moon then falls and earth speeds up

    and i accept by faith this cools the system and atmosphere retracts

    then tides decelerates earth which makes moon gain potential energy

    ...
    and then the system goes on like this forever

    isnt this actually conservation of energy?
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  10. #9  
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    Quote Originally Posted by luxtpm View Post
    well the other option isnt less wilder actually

    kinetic energy transforms into heat energy which transforms into kinetic energy

    and while it does evrything goes on forever on many different ways

    sounds like conservation of energy makes the universe some kind of perpetuum mobile by definition of conservation of energy

    take my moon example

    tides decelerates earth which makes moon gain potential energy

    but this has generated heat so the atmosphere extends

    so moon then falls and earth speeds up

    and i accept by faith this cools the system and atmosphere retracts

    then tides decelerates earth which makes moon gain potential energy

    ...
    and then the system goes on like this forever

    isnt this actually conservation of energy?
    This is complete nonsense. For one, the tidal heating of the Earth has an insignificant effect on the extension of the atmosphere.
    For the other, the Earth's atmosphere turns with the Earth which turns faster than the Moon orbits, so even if we were to allow for the atmosphere extending all the way to the Moon, the effect would push the Moon further away.

    Even if we ever had a situation where the Moon was approaching the Earth rather than receding (as would be the case if the Moon orbited faster than the Earth rotated.), there would be no cooling of the Earth, you would still get tidal heating, as this is caused by the physical deformation of the Earth caused by the tides, which exist no matter whether the Moon is approaching or receding. This situation would continue only until the Moon got close enough to come within the Roche limit where it would be torn apart by tidal forces giving the Earth rings. Your idea of the Moon perpetually going in and out is totally incorrect and based on a great number of misconceptions.
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  11. #10  
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    Quote Originally Posted by luxtpm View Post
    man have you noticed how many times you say the word sense

    what would freid say?

    are you afraid of life not making sense for you?
    Yes I do, because I believe posts on a scince forum should make sense. When they don't, I say so. Your posts seldom do.

    Life makes a lot of sense to me. You don't, most uf what you post is gibberish, and it's very difficult to even guess what you are trying to say.

    who the hell is freid?
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  12. #11  
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    yeah i admit i didnt make much sense yet what i meant

    tidal energy comes from the lost of earth rotation

    bu that kinetic energy the earth loses in its rotation its gained by the moon as potential energy as the conservation of angular momentum states

    so energy doesnt get created nor destroyed

    EDIT:

    this arises the question if shouldnt the earth cool down as the moon gains altitude
    Last edited by luxtpm; March 15th, 2012 at 07:58 AM.
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  13. #12  
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    Quote Originally Posted by luxtpm View Post
    yeah i admit i didnt make much sense yet what i meant

    tidal energy comes from the lost of earth rotation

    bu that kinetic energy the earth loses in its rotation its gained by the moon as potential energy as the conservation of angular momentum states

    so energy doesnt get created nor destroyed
    There are two ways that the Earth gives up angular momentum. One is by transferring it to the Moon via gravitational interaction and the other is through tidal friction caused by the Earth rotating through the tidal bulge. This generates heat that it then radiated away into space. This radiation, in the form of photon carry angular momentum away with them. In fact, more of the Earth's angular momentum is shed this way than is transfered to the moon. This means that the Earth-moon system is not a closed system in terms of either energy or angular momentum.

    EDIT:

    this arises the question if shouldnt the earth cool down as the moon gains altitude
    No, the energy transfered to the Moon comes from the Earth rotational energy not its thermal energy. The only change in temp would be the heating caused by tidal friction.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  14. #13  
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    Quote Originally Posted by luxtpm View Post
    so are you suggesting there theres absolute vacuum?

    No, but it's close enough. Comparing the atmospheric friction from so small an amount of air against the tidal forces on the Moon would be like if you saw a fly climbing on the windshield of your car, and you decided to get out and weigh the fly because you thought the fly's weight might be affecting your gas mileage.

    When one force dominates, it's easier to just leave the smaller force out of the equation sometimes.

    Quote Originally Posted by luxtpm View Post

    sounds like conservation of energy makes the universe some kind of perpetuum mobile by definition of conservation of energy
    Yeah, it kind of is, except for the Big Bang Expansion.

    take my moon example

    tides decelerates earth which makes moon gain potential energy
    Yeah. The Earth loses rotational inertia (kinetic energy of motion), and part of that is made up for because of the Moon gaining potential energy.

    but this has generated heat so the atmosphere extends
    Actually when the atmosphere heats up, most of the energy is radiated into space as black body radiation (EM waves). It's kind of like how a light bulb creates light by super heating a piece of tungsten until it glows white hot, except in the case of the atmosphere the EM waves are at a much lower frequency, like mostly below the visual range.

    so moon then falls and earth speeds up
    No. It's a one way trade, unfortunately. Earth stays slowed down, and the Moon stays at its new height.


    and then the system goes on like this forever

    isnt this actually conservation of energy?
    Some day, Luxtpm, we will teach you about entropy. The amount of energy always stays the same, but the orderliness of that energy diminishes over time. Entropy is usually a one way process.
    Some clocks are only right twice a day, but they are still right when they are right.
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  15. #14  
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    im still confused:

    rotational energy of earth is transformed into heat by tides

    conservation of angular momentum makes the moon gain as potential energy the rotational energy earth lost

    am i the only one seeing an excess of energy here?
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  16. #15  
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    Quote Originally Posted by luxtpm View Post
    im still confused:

    rotational energy of earth is transformed into heat by tides

    conservation of angular momentum makes the moon gain as potential energy the rotational energy earth lost

    am i the only one seeing an excess of energy here?
    Some of the rotational energy that the Earth loses is transformed into heat.

    The rest of the energy loss is transferred to the moon via gravitational coupling.

    I other words, if W equals the total energy loss by the Earth via tidal interaction, Y= the energy transformed to heat and X= the energy transferred to the Moon,

    then

    W=Y+X

    Conservation of angular momentum does not require that all of the angular momentum lost by the Earth is transferred to the Moon. In fact, the majority is carried away by the radiated heat.

    Everything adds up and there is no extra energy nor angular momentum to account for.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  17. #16  
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    Quote Originally Posted by luxtpm View Post

    am i the only one seeing an excess of energy here?
    Do you understand the concept of black body radiation? Hot objects emit light. Emitting light causes an object to lose energy. The light from Earth's heat flies off into space, never to return.

    You must understand that the Conservation of Energy principle only applies to closed systems. The Earth and Moon is not a closed system. The Sun is constantly heating both objects, and both objects are constantly emitting black body radiation into space.
    Some clocks are only right twice a day, but they are still right when they are right.
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