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Thread: sun "wattage"

  1. #1
    Always a newbie glider14's Avatar
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    i dont know where this would go so i put it here.... does anyone know what "wattage" sunlight equals?? i know there is no wattage on sun... but hopefully you get what im asking.
    Alex
    Everything is explainable. The seemingly unexplainable is but a result of our insufficient knowledge.- Hans Brewer

  2. #2
    Hello, I must be going... Not a Number's Avatar
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    Well Wattage actually is a measurement of electrical power (voltage x current) but most people associate it with light output when concerned with light bulbs. My blow dryer is rated at 1875 Watts but produces very little visible light (plenty of IR though).

    But a Google search of "Power output of sun" linked to this page which gives a value of approximately 4 x 10e26 Watts (10 to the 26th power). That's ~400,000,000,000,000,000,000,000,000 Watts.

    What you are really concerned with is Luminance or Illuminance (see this sticky thread), usually expressed in lumens.
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

  3. #3
    Always a newbie glider14's Avatar
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    woah... thanks! ive been wondering how strong the sun really was
    Alex
    Everything is explainable. The seemingly unexplainable is but a result of our insufficient knowledge.- Hans Brewer

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    Doing it wrong until I do it right. xvart's Avatar
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    Quote Originally Posted by [b
    Quote[/b] (glider14 @ Dec. 22 2006,10:48)]woah...
    Woah is right. He's a beast I tell you, a beast!

    xvart.
    "The tragedy of life is not that every man loses; but that he almost wins."

    "Quis custodiet ipsos custodes?"

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    Let's positive thinking! seedjar's Avatar
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    Lumens is a good estimate of light output, but for the purpose of growing plants, what you're really interested in is a value called PAR, photosynthetically available (active?) radiation. Lumens measure light that people see - PAR measures the light that plants use for energy. Unfortunately, many bulbs are not rated in terms of PAR, so often lumens are your best guide to brightness. Because the spectrum we see in is different than the spectrum that plants photosynthesize, you need to pay attention to the color of light emitted by your bulbs, to make sure that your plants are getting light that they can actually use. This is measured by the color temperature of the bulb, which is usually a number in the thousands measured in degrees Kelvin, like 6500K. I'm not sure exactly where the Kelvin scale comes from; it's some physics thing - I think it has to do with the color of light emitted by some sort of metal when you heat it to a given temperature or something. It doesn't really matter for our purposes - all you need to know is that you can use the color temperature rating to help match your bulbs to the colors of light that plants use, and try to match the intensity of the sun in those colors.
    ~Joe
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    Doing it wrong until I do it right. xvart's Avatar
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    Quote Originally Posted by [b
    Quote[/b] (seedjar @ Dec. 22 2006,4:03)]I'm not sure exactly where the Kelvin scale comes from; it's some physics thing - I think it has to do with the color of light emitted by some sort of metal when you heat it to a given temperature or something.
    The Kelvin scale was created as the absolute scale of temperature meaning that 0 (zero) K is the absolute lowest theoretical temperature at which point there is no heat energy in matter. Essentially, all matter and atoms stop moving and radiating any heat. The increments of measurement for the Kelvin scale and the Celcius scale are equivilent; the only difference is the zero mark on each scale. Kelvin equals -273 deg. C (it's actually like 273.xx something) so zero degrees kelvin equals -273 deg C.

    Of course this is the calculated 'absolute zero' and has never been achieved nor observed. Additionally, there is no 'degree sign' when shorthanding the temperature in writing like the little circle next to the F and C in other scales. A simple 'K.'

    I knew majoring in physics in college would have some practical application!

    xvart.

    edit: it's 273.15 (I just looked it up). Interestingly enough, you only capitalize kelvin when it starts a sentence or you are referring to the Kelvin scale. You learn something new everyday! Needless to say I corrected those mistakes as well.
    "The tragedy of life is not that every man loses; but that he almost wins."

    "Quis custodiet ipsos custodes?"

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    Stay chooned in for more! Clint's Avatar
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    Ok... I thought kelvin temperature was a theoretical black body and the light it emits at different temperatures in the kelvin scale?

  8. #8
    Let's positive thinking! seedjar's Avatar
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    I'm talking about the Kelvin scale of light frequency, which has to do with the temperature (relative to absolute zero, hence the necessity for measurements in kelvin) of a black body radiating light of a given color. Not the general measurement of temperature.
    ~Joe

    PS - Excellent ninja skillz, Clint.
    o//~ Livin' like a bug ain't easy / My old clothes don't seem to fit me /
    I got little tiny bug feet / I don't really know what bugs eat /
    Don't want no one steppin' on me / Now I'm sympathizin' with fleas /
    Livin' like a bug ain't easy / Livin' like a bug ain't easy... o//~

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