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Thread: VENUS planet of Heat.

  1. #1
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    VENUS planet of Heat.

    I read something interesting and amazing while browsing internet :

    "Venus radiates twice the energy it receives from the sun".

    Of course it is surprising from a theoretic point of view. Because it suppose an internal source of heat or an other external source than the Sun.

    I did not found any reference. Is somebody aware of some measurements in agreement with that or is it just bunk ?

  2. #2
    I believe only Jupiter and Saturn emit heat in amounts greater than they receive from the sun.

  3. #3
    Actually, yes. Venus absorbs more heat that it emits. This is the radiative transfer that Sagan spoke of. This is part of the runaway greenhouse effect that keeps Venus so hot.

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    Quote Originally Posted by seanhogge View Post
    Actually, yes. Venus absorbs more heat that it emits. This is the radiative transfer that Sagan spoke of. This is part of the runaway greenhouse effect that keeps Venus so hot.
    In the long term , it is not possible , the planet must reach an equilibrium and radiate as much energy as it receive , whatever the source. Or the planet is very young ,like Velikovski believe , but I cannot accept that. The solar system is old and it is a pure fantasy to believe a new planet has been born in the historical times.

  5. #5
    Here's how I understand it works on Venus.

    Sunlight reaches Venus and is mostly reflected back into space. The remainder that isn't travels to the surface of Venus. Once at the surface, this light is partially reflected and partially absorbed.

    The light that is absorbed warms the surface. This warmth is radiated from the surface as per the Wien and Stefan-Boltzman laws. Wien's law tells us that this heat is mostly at the infrared wavelength.

    The atmosphere, while transparent to visible wavelength light is at least partially opaque to infrared. This radiation has a harder time leaving than when it was at a shorter wavelength.

    Since we have radiation from both "sides" of the atmosphere, the planet is not in thermal equilibrium.

    Eventually, there is a shift to higher wavelength radiation which can escape the atmosphere. This achieves thermal equilibrium.

    No planet "must" radiate as much energy as it receives. Some of that energy is converted into mass or otherwise stored and kept from radiating back out into space. If a planet must emit all the solar energy it received, life wouldn't exist in its current incarnation on our planet.

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    Radiation can't just be converted to mass in a planet. There is no mechanism for direct conversion and storage.

    All of the inner, terrestrial planets are in thermal equilibrium to a very close approximation, radiating almost precisely as much energy as they receive from the sun. This is not true about the gas giants, which tend to radiate more than they receive, but Venus is definitely not in this category.

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    I suspect that the statement "Venus radiates twice the energy it receives
    from the sun" is a misinterpretation of the actual situation. The surface of
    Venus has a mean temperature of 464 degrees Celsius, hotter than the
    maximum temperature of Mercury, which is 427 degrees Celsius, and way
    hotter than Mercury's mean of 179 degrees Celsius. The high temperature
    doesn't imply that it gives off more energy than it receives, though. Venus
    just strikes its balance between incoming and outgoing energy at a higher
    temperature.

    -- Jeff, in Minneapolis
    Last edited by Jeff Root; 2008-Dec-09 at 04:06 AM. Reason: fixed punctuation typo
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
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    When Earth begins the next ice age it will be radiating more energy than it receives, otherwise the average temperature would not decrease. Likely it will be less than 1% difference and when the net heat loss ends we will begin the next intergalcial period, OMHO. Perhaps Venus is cooling about 50 degree c = 90 degrees f per century. Neil

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    Why would Venus be cooling at the incredible rate of 50C per century?

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    Lightbulb Thermal imbalance

    It has been known for a long time that Venus is in thermal equilibrium with incoming solar radiation (Tomasko, et al., 1980). Venus does not radiate more heat than it received from the sun, nor does it absorb more heat energy than it radiates back into space (although perhaps now a bit dated, see my Talk.Origins entry Is Venus Young?)

    However, it has been known since the days of the Voyager mission that all 4 of the gas giant planets emit more heat energy than they receive from the sun. The most unbalanced of the lot is Neptune, which radiates roughly three times the energy it receives from the sun. But this is not hard to understand. All 4 of the gas giant planets are simply too large to have cooled off since the solar system began. Just as Earth keeps itself warm by creating heat energy inside (radioactive decay of unstable heavy elements in the mantle) the gas giant planets create heat energy inside through the viscous friction of helium continuously sinking through the lighter hydrogen. Jupiter emits about 1.7 times as much energy as it gets from the sun (Hanel, et al., 1981). Uranus emits about 1.06 times the energy it gets from the sun (Pearl, et al., 1990). Neptune emits about 2.6 times as much energy as it receives from the sun (Pearl & Conrath, 1991). I don't remember the number for Saturn and it's not in the abstract of Hanel, et al., 1983. Since I am now retired, I can't see the paper that is not open source. So you'll have to find that yourself.

    All of the terrestrial planets (Mercury, Venus, Earth, Mars & Pluto) are in energy balance with insolation, averaged over the entire globe and a full orbit.

  11. #11
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    Quote Originally Posted by galacsi View Post
    I read something interesting and amazing while browsing internet :

    "Venus radiates twice the energy it receives from the sun".
    I did a google search using that phrase, and turned up that unsupported claim on a notorious Electric Universe promotion site. And that's it.

    I did not found any reference. Is somebody aware of some measurements in agreement with that or is it just bunk ?
    Looks like pure bunk.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." Abraham Lincoln

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  12. #12
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    Quote Originally Posted by Tim Thompson View Post
    It has been known for a long time that Venus is in thermal equilibrium with incoming solar radiation (Tomasko, et al., 1980). Venus does not radiate more heat than it received from the sun, nor does it absorb more heat energy than it radiates back into space (although perhaps now a bit dated, see my Talk.Origins entry Is Venus Young?)

    However, it has been known since the days of the Voyager mission that all 4 of the gas giant planets emit more heat energy than they receive from the sun. The most unbalanced of the lot is Neptune, which radiates roughly three times the energy it receives from the sun. But this is not hard to understand. All 4 of the gas giant planets are simply too large to have cooled off since the solar system began. Just as Earth keeps itself warm by creating heat energy inside (radioactive decay of unstable heavy elements in the mantle) the gas giant planets create heat energy inside through the viscous friction of helium continuously sinking through the lighter hydrogen. Jupiter emits about 1.7 times as much energy as it gets from the sun (Hanel, et al., 1981). Uranus emits about 1.06 times the energy it gets from the sun (Pearl, et al., 1990). Neptune emits about 2.6 times as much energy as it receives from the sun (Pearl & Conrath, 1991). I don't remember the number for Saturn and it's not in the abstract of Hanel, et al., 1983. Since I am now retired, I can't see the paper that is not open source. So you'll have to find that yourself.

    All of the terrestrial planets (Mercury, Venus, Earth, Mars & Pluto) are in energy balance with insolation, averaged over the entire globe and a full orbit.
    Yep. Actually, IIRC, the odd one is Uranus, as it is big enough that it should not be as close to thermal equilibrium as it is.

  13. #13
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    Quote Originally Posted by Van Rijn View Post
    I did a google search using that phrase, and turned up that unsupported claim on a notorious Electric Universe promotion site. And that's it.



    Looks like pure bunk.
    Yes from that site. But I did not want to provoke a reflexive answer.

  14. #14
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    Quote Originally Posted by Tim Thompson View Post
    It has been known for a long time that Venus is in thermal equilibrium with incoming solar radiation (Tomasko, et al., 1980). Venus does not radiate more heat than it received from the sun, nor does it absorb more heat energy than it radiates back into space (although perhaps now a bit dated, see my Talk.Origins entry Is Venus Young?)

    However, it has been known since the days of the Voyager mission that all 4 of the gas giant planets emit more heat energy than they receive from the sun. The most unbalanced of the lot is Neptune, which radiates roughly three times the energy it receives from the sun. But this is not hard to understand. All 4 of the gas giant planets are simply too large to have cooled off since the solar system began. Just as Earth keeps itself warm by creating heat energy inside (radioactive decay of unstable heavy elements in the mantle) the gas giant planets create heat energy inside through the viscous friction of helium continuously sinking through the lighter hydrogen. Jupiter emits about 1.7 times as much energy as it gets from the sun (Hanel, et al., 1981). Uranus emits about 1.06 times the energy it gets from the sun (Pearl, et al., 1990). Neptune emits about 2.6 times as much energy as it receives from the sun (Pearl & Conrath, 1991). I don't remember the number for Saturn and it's not in the abstract of Hanel, et al., 1983. Since I am now retired, I can't see the paper that is not open source. So you'll have to find that yourself.

    All of the terrestrial planets (Mercury, Venus, Earth, Mars & Pluto) are in energy balance with insolation, averaged over the entire globe and a full orbit.
    About the gas giants , I am completely Ok with your explanations. And as for neptune 3 times more energu than received from the Sun dos not account for much.

    About the article from Tomasko & al I don't understand the phrase : "A comparison of the measured solar flux profile with thermal fluxes computed from the measured temperature structure and composition shows that the greenhouse mechanism explains essentially all of the 500-K difference between the surface and radiating temperatures of Venus. "

    I mean in the context of my question. I have no problem with greenhouse effect , it exists on Earth after all , with a much less dense atmosphere.But is there some measurements of the global thermal flux from Venus that can be compared with the solar flux ?

    Don't know , may be I will go the EU forum and ask them from where they got this affirmation.

  15. #15
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    Check Your Garden!

    Quote Originally Posted by galacsi View Post
    Yes from that site. But I did not want to provoke a reflexive answer.
    Well, it worked. You didn't get a reflex answer. But if I were Van, I'd be a little irritated.

    Watch out for the invisible elf!

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