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On carbon, methane and electromagnetic radiation

  1. Mar 13, 2013 #1
    iTunes University layman looking for answers and willing to do the work – just need some direction.

    I now understand electromagnetic waves can be created when molecules vibrate – which they all do. I understand the frequency of the light correlates to the frequency of the molecular vibration – which is itself a result of the mass of the individual vibrating adams and the strength of the molecular bonds.

    And, I understand that a “bombarded” adam generates electromagnetic waves when the electron drops back to a lower energy state. I understand the resulting energy of the electromagnetic wave – the frequency – correlates to the energy difference between the two energy orbitals. The electrons travel around the nucleus in waves by “choosing” specific complete-orbital-wave frequencies and distances from the nucleus, otherwise that orbital could not exist because out-of-phase waves would cancel each other out as the electron “circles” the nucleus.

    I believe the the resulting lightwaves, either from vibrating molecules or from electrons dropping to a lower energy state, generate resulting magnetic waves, and those very magnetic waves generate “new” lightwaves.

    OK - a few questions...

    I am told, methane is a “stronger” greenhouse gas than carbon dioxide. Why? I understand that there are multiple vibrational directions or “degrees of freedom” for each bonded adam within the molecule because adams vibrate in a three-dimensional world. Is it that methane is vibrating with a greater number of frequencies and can therefore absorb a greater number of frequencies? But, isn’t the earth is emitting infrared radiation at a specific frequency? And, doesn’t the earths infrared frequency change slightly from one day to the next as the earth’s temperature changes?

    Which brings me to the next question…
    As the vibrating molecules give off more and more energy – photons – don’t the molecules lose energy? And, if they lose energy does their vibration change? And if the vibration changes then the frequency of the light would change. Which I know is not true because molecules of a specific type give off a specific frequency.

    And lastly...
    Do the magnetic waves that are propagated from lightwaves create new lightwaves that amplify the original lightwaves? Which then create new magnetic waves and the cycle continues? And if so, is that why light travels forever? (Or at least for 13 1/2 billion light-years as far as we know.) Or does light travel forever because a body in motion (a photon) remains in motion?

    I’m happy to read further on my own. I just need some direction.
    Last edited: Mar 13, 2013
  2. jcsd
  3. Mar 13, 2013 #2


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    Staff: Mentor

    The picture you have of discrete vibrational frequencies, and therefore a discrete absorbtion spectrum, only works for an isolated molecule. In a gas, where you have lots of them, collisions and interactions between the molecules, along with the Doppler effect, transforms discrete absorption into a continuous absorption band. The amount of absorption will change as a function of the frequency of the light.

    To figure out which gas is a stronger green house gas, you have figure out what the emission of the Earth looks like in the infra-red region, and then see how much of that will be absorbed by the different gases.

    And I do not know what you mean by "magnetic wave". Do you mean electromagnetic wave? In that case, it is the same as a light wave, with the name light wave only applying to a small part of the full electromagnetic spectrum (from the infra-red to the ultra-violet).
  4. Mar 13, 2013 #3


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    Staff: Mentor

    The electromagnitic wave just propagates freely in space until it encounters an object. I don't think that "a body in motion" is the best way to talk about photons, but if it helps you to see it that way, the photon just travels in space until it is absoebed by something.
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