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Images of the Universe

  1. Jun 17, 2012 #1
    We "see" distant objects as they were , sometimes, very, very, long time ago.
    I assume these images are all in the fleeting / transient - for us - category.
    What is it in their nature that makes them last - for us, and, potentially, other observers, to "see" them. In our world, all images, whether mental, electronic, physical ... have limited life.
     
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  3. Jun 17, 2012 #2

    phinds

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    We see them via instrumentation (telescopes in various parts of the EM spectrum). They are not in any way "fleeting/transient", so I do not understand that part of your question.
     
  4. Jun 17, 2012 #3
    phinds: I agree: - my wording is msleading, especially the words "fleeting" and "to us".
    What I meant was that images we "see" do not allow us to "play back" what has happened
    before or to slow things up so that we can see the details of very violent events in the Universe. Hence my use of "transient images".
    However, the question, why these images last so that we can "see" them now, remains.
    FStepien
     
  5. Jun 17, 2012 #4
    We can see them now because they emitted EM radiation that has been traveling through space.
     
  6. Jun 17, 2012 #5

    Drakkith

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    On the contrary. We can easily play back what has happened so long as we have been recording the sequence of events we wish to replay. This is exactly like you would record and play back anything with a normal camera. In fact, the chips used in your average digital camera are almost exactly the same as the ones used in many of the state of the art observatories. The only difference between me recording my cat chasing its tail on my bookshelf and recording the change in a supernova is that the light has to travel a far greater distance to get from the supernova to my telescope.
     
  7. Jun 17, 2012 #6

    phinds

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    You still seem to be presenting an incoherent concept. If I wave my hand and you see me do it, you cannot "play back" the event nor can you watch it in slow motion.

    If, as Drakith suggested, you record it with a video camera, then you CAN play it back.

    As to why we can see them at all, aroc91 has already answered that
     
  8. Jun 19, 2012 #7
    Having doug myself into a hole, I might, as well, deepen it:
    Electromagnetic radiation:
    I am aware that it is this that this & our ingenuity give us various ways of looking at the
    Universe.This is the reason why I put the words WE SEE in inverted commas. But, what is
    it that gives the EM Radiation this "self propagation" nature ?
    Even so, our atmosphere is quite effective in blocking some parts of the EM Spectrum. This is the reason why we venture outside of it.
    I would ASSUME that this occulting may exist throughout the Universe. I, also, assume that this "something or other" doing the occulting does not have to be as big as the enormous size of the body being occulted. I, also, assume that in the concept of a Black Hole, none of the EM Radiation can emanate from it, not, just Light in a narrower sense.
    Some of the questions that come to mind:
    How much of this occulting is there ? Do partial occultations exist ? ....
    F. Stepien
     
  9. Jun 19, 2012 #8
    Hey man Can't you post your question in easy language.when i am reading this question.I feel i am reading some English mixed with some other language.
     
  10. Jun 19, 2012 #9

    Drakkith

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    It is simply the laws of the universe than an EM wave self propagates. If you want to learn how this happens there are plenty of articles online. You can try wikipedia's article on electromagnetic radiation for starters.

    Occultation is a specific term that means one body moving in front of another and blocking part or all of that body from view. I don't see how this relates to your questions about EM radiation. Actually, I don't even know what you are asking here.
     
  11. Jun 19, 2012 #10
    DhruvKumar,
    I am trying hard not to respond to individuals. But, you changed all that by your
    "Hey man Can't you post your question in easy language.when i am reading this question.I feel i am reading some English mixed with some other language." Really: is this English ?
    Also, you are so perceptive ! It is so difficult to infer from my name that I am of some foreign origin !
    Occultation: I have used the word without any reference to a dictionary or awareness of
    what the "astromy community" takes it to mean. Now, I found one definition in my dictionary:
    concealment by one celestial body by another. What is a celestial body ? You appear to imply that a body is something like a planet (obscuring the sun). I chose to take it to mean
    a "composite" like a galaxy ...
    Why don't you address yourself to the crux of what I am "voicing" rather than to the "nitty gritty" ?
    FStepien
     
  12. Jun 19, 2012 #11

    Drakkith

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    A celestial body is generally referred to as an object held together by gravity, such as moons, planets, stars, etc. It can refer to galaxies as well, but I have never heard of someone saying one galaxy occulted something. The term, as far as I know, just isn't used in that way.

    Because your questions didn't make any sense with the usual way occultation is used. Are you asking about occultations as a whole? If so then yes, they happen all the time. The moon is constantly moving in front of stars as it orbits the Earth, and you can easily see this happen over the course of even a few minutes with a telescope.

    But I still don't see how this has anything to do with your original question, black holes, and the atmosphere blocking parts of the EM spectrum. I'm still uncertain as to what your original question was in regards to us "seeing things now".

    And please, don't get upset. We are trying to answer your questions but it is very difficult to answer a question that you barely understand. Just try and keep it simple and stick to one thing at a time. Is your basic question regarding the propagation of light through the universe?
     
  13. Jun 20, 2012 #12

    jimgraber

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    I think you mean obscuration or absorption, rather than occultation.
    Astronomers believe as much as 50% of star formation may be obscured, especially in the early universe.
     
  14. Jun 20, 2012 #13

    jimgraber

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  15. Jun 20, 2012 #14
    jimgraber,
    Thank you for correcting my semantics (I agree !) & for the link.
    This was a rather painful experience for me. I started on the wrong foot by not explaining what the word IMAGE meant to me. After all, visible light image, infra red image, wide view image, narrow view/highly focussed image ..... are all different.
    In my mind I was not limiting myself to any particular part of the EM spctrum.
    The rest of the interaction stems from this lack of precision on my part.
    FStepien
     
  16. Jun 22, 2012 #15
    Thanks a lot everyone as i was having some doubts. Now they are cleared. Thanks a lot.
     
  17. Jun 22, 2012 #16
    You're telling me about a transient universe.

    I'm on tenterhooks waiting for Betelgeuse to blow. It may already have done so, but the light may not yet have reached us.
     
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