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Question about light and telescopes

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  • 04-12-2011 11:36pm
    #1
    acurno
    Registered Users Posts: 236 ✭✭


    Wondered about this as I was staring into the sky last night. Do the most powerful telescopes on Earth see the same light as we see with our naked eye? I was always led to believe that the more powerful the telescope, the further back in time we could see. As in, if we had an infinitely powerful telescope here on earth, we could see the formation of other stars and planets as it happened billions of years ago. But surely we can't see further back depending on the strength of the telescope because it's still the same light that we see with our own eyes.

    Don't know if I'm making much sense there.....


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    #2
    slade_x
    Moderators, Science, Health & Environment Moderators Posts: 1,425 Mod ✭✭✭✭slade_x


    acurno wrote: »
    Do the most powerful telescopes on Earth see the same light as we see with our naked eye? I was always led to believe that the more powerful the telescope, the further back in time we could see.


    Yes its the same light, you just dont get enough of it to resolve incredibly distant objects as thats not the eyes purpose, telescopes have a larger surface area so they can capture more light hence reflecting more of it to bring it to a focus for our eyes. Camera sensors are also useful as their long exposures allow an image to be generated from more accumulated light as you no doubt already know. many users have posted their long exposure shots here on the boards, of which the vast majority would not have been possible without the accumulation of light. The more light the more information, which is easy to demonstrate with the differences in vision during the course of a day (after sunrise/ midday/ before sunset/ after sunset) and then the eventual transition to night where the sun is too far below the horizon to illuminate anything in our field of view unless the moon is overhead. The sunnier the day the more intense your visuals and if it wasnt for glare (which is additional light reflecting from other surfaces) you could resolve a lot more detail about distant objects in your field of view. look how much less detailed and luminous objects are in the shade.
    acurno wrote: »
    As in, if we had an infinitely powerful telescope here on earth, we could see the formation of other stars and planets as it happened billions of years ago.

    A visual telescope would not be able to see through the accretion disk to see early stars and planets, as there would be far too much stuff in the way. They would also be unable to see the beginning of a stars life before fusion occurs as obviously enough it is not generating its own light yet.


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    #3
    coylemj
    Registered Users Posts: 25,429 ✭✭✭✭coylemj


    acurno wrote: »
    But surely we can't see further back depending on the strength of the telescope because it's still the same light that we see with our own eyes.

    Don't know if I'm making much sense there.....

    You did in the second last sentence, the first one quoted above.


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    #4
    Cú Giobach
    Closed Accounts Posts: 3,772 ✭✭✭Cú Giobach


    acurno wrote: »
    Wondered about this as I was staring into the sky last night. Do the most powerful telescopes on Earth see the same light as we see with our naked eye? I was always led to believe that the more powerful the telescope, the further back in time we could see. As in, if we had an infinitely powerful telescope here on earth, we could see the formation of other stars and planets as it happened billions of years ago. But surely we can't see further back depending on the strength of the telescope because it's still the same light that we see with our own eyes.

    Don't know if I'm making much sense there.....
    A telescope doesn't bring an object "closer" it just gathers more light than your naked eye can, consequently enabling you to magnify the image.
    Think of it this way....
    Jupiter is (as an average) 45 light minutes away from Earth, so when you look at the planet with your naked eye you see it as it was 45 minutes ago.
    When you look through a telescope it is still 45 light minutes away but you have gathered more light therefore you can magnify the image and see the planet in detail.
    Since the light takes the same amount of time to travel from the planet to the telescope and then into your eye, you are still seeing it as it was 45 minutes ago, even though you can now see the planet much clearer.
    The same holds true for objects at any distance.
    When people say "the more powerful the telescope, the further back in time we could see" they just mean we can use a telescope to actually see a distant object that is too dim to resolve with the naked eye, it's like expanding your pupil from a few millimetres to a couple of meters in diameter. :)


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