Five physics questions

Discussion in 'Physics & Math' started by Christmas 1996, Apr 17, 2004.

  1. Christmas 1996 Registered Senior Member

    1. Why are galaxies moving faster away from each other? What is giving them that extra 'energy' to move faster?

    2. Why is glass transparent, or any other transparent material for that matter? How do the photons interract with the atoms when moving through that material? I'm presuming that photons aren't simply travelling through the material . I.e They're not travelling between the space between the nucleus and the electrons. Or are they? I don't know.

    3. Why is it colder higher in atomsphere, as opposed to warmer lower in the atmosphere?

    4. Why is it in binary stars that when they orbit 'each other' faster the closer they become (they orbit each other closer). Whereas in a solar system the faster a planet orbits a star the futher away it becomes

    5. How come we can see light spiralling into a blackhole? Surely we wouldn't be able to see light if it's going into the black hole and not into our eyes
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  3. Pete It's not rocket surgery Registered Senior Member

    Good questions!

    1. Don't know. I think "Dark Energy" or "Quintessence" is the current favourite? Don't ask me to explain - I don't know what those things really are (if they even exist).
    2. This is nasty Quantum Electrodynamics stuff I don't know much about, but I'll give a very dodgy explanation anyway!
      Light interacts with atoms by shifting electrons between energy states. In the case of glass, there are no convenient energy state gaps that match the photon energy of visible light, so the photons are not completely absorbed by the electrons - the electron tries to go to a higher state, finds that it has nowhere to go, so lets the photon go on its merry way.
    3. What's the difference? Colder at higher altitutde is the same as warmer lower, right?
    4. Hmm... you may be a little confused. Closer orbits are always faster orbits.
    5. You're right, we can't. We can and do detect the radiation emitted from charged particles in the accretion disk.
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  5. ddovala Pi is exactly 3 Registered Senior Member

    actually you can see the light spiriling into the black hole until it reaches the event horizon (the point that the light cannot escape). An actual black hole is just a single point persumably infinately small...
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  7. 2inquisitive The Devil is in the details Registered Senior Member

    Pete gave the correct answer to question no. 5. The only light we can "see" is the
    photons that are entering our eyes, at which point they are destroyed.
  8. invert_nexus Ze do caixao Valued Senior Member

    Quick comment here, this has always been a pet peeve of mine. Isn't our sun named Sol, hence we live in THE Solar System? I hear comments all the time about other solar systems and etc. It's always annoyed me. Other planetary systems sure, but no other SOLar system, unless you name another star Sol somewhere down the line.

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    Anyway, that's my little rant about that.

    As for number 3, it's colder higher up because there's lower air pressure, less air around you to hold in the heat. Although, in space, if you're in direct sunlight it gets pretty hot right? Not sure about the actual temperature. So you'd think the same would be true about the upper atmosphere. Hmmm. Something to do with earth's magnetic field perhaps? You do get sunburned a lot easier at higher elevations, yet it is still cold. So you could say that the lower air pressure means the air is less capable of storing heat (which is a good thing; because if the upper atmosphere took the heat before it reached the ground, it might tend to get cold down here). So even though the heat passes through and can cause sunburns, etc... the overall air temperature is cold. Sounds good. I'm sure there's more to it than that, and more elegant ways to put it, but that works for me.
  9. Redrover Registered Senior Member

    The cool thing about space is that the only way to transfer heat is by radiation. In space, if you were in front of the Sun, you would start absorbing the heat radiated from the sun but your also increase the amount of heat your body normally radiates. So as long as you don't dress in black, you should be okay.
  10. James R Just this guy, you know? Staff Member

    The atmosphere only gets colder as you go upwards to a certain point, then things get warmer again. The atmosphere has many layers.

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