i dont understand how can a telescope see the past

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Orbax At that point you kind of crossed the rubicon and you might as well lay siege to Rome

ask your teacher for a better explaination. How can you accept that without an explaination.

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Originally posted by venomX i dont understand how can a telescope see the past

very hard to explain... example, the sun is quite a far way from us... i think it takes about 8mins? (not sure) for the light from the sun, to reach earth... so we're basicly seeing the sun 8mins ago... which is basicly looking @ the old sun... now apply that to stars that are trillions of light years away from us... it will take billions of years for the light to reach us, so the hubble is seeing the past when the light from the stars reach it... get it???

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ah if u had said it like that before
yeah i heard smth like that some time ago really interestin tho :d

Your teacher was probably talking about the hubble telescope being able to see far away light. Although light particles are really tiny, light consists of matter, or actual "solid stuff." And since matter is neither created nor destroyed (first law of thermodynamics), the light particles that were present at the begining of the universe still exist today.

So the telescope is not seeing the past, but actually something from the past that still exists today in the present.

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Last edited by PeacefulWarrior on Sep-29-2002 at 04:28

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Originally posted by PeacefulWarrior Your teacher was probably talking about the hubble telescope being able to see far away light. Although light particles are really tiny, light consists of matter, or actual "solid stuff." And since matter is neither created nor destroyed (second law of thermodynamics), the light particles that were present at the begining of the universe still exist today. So the telescope is not seeing the past, but actually something from the past that still exists today in the present.

huh? but say, a star 2000 light years away from us, which we can visibly see from earth... like a little yellow dot @ night. ok, we are seeing the star that is 2000 years ago (follow?) coz it takes 2000 years for the light of the star to reach us... but as we see that star of the past... the present star actually exploded, and it will take another 2000 years or so for us to realize it has exploded, doesnt that mean we saw the star explode... but in reality, it already exploded 2000 years ago... is that not us witnessing the past?

that explanation just confused me, ne one know more about this stuff?

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Originally posted by dj_nomiz huh? but say, a star 2000 light years away from us, which we can visibly see from earth... like a little yellow dot @ night. ok, we are seeing the star that is 2000 years ago (follow?) coz it takes 2000 years for the light of the star to reach us... but as we see that star of the past... the present star actually exploded, and it will take another 2000 years or so for us to realize it has exploded, doesnt that mean we saw the star explode... but in reality, it already exploded 2000 years ago... is that not us witnessing the past? that explanation just confused me, ne one know more about this stuff?

If we look at the star you're describing, we're just seeing the remnants of that star, or the light particles that the star emitted when it exploded 2000 years ago. So that star doesn't actually exist anymore, just the light from that star remains.

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Originally posted by PeacefulWarrior If we look at the star you're describing, we're just seeing the remnants of that star, or the light particles that the star emitted when it exploded 2000 years ago. So that star doesn't actually exist anymore, just the light from that star remains.

hmm... true, makes sense, ok i understand wat ur saying now... so is my post about being able to see the past wrong?

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Originally posted by dj_nomiz hmm... true, makes sense, ok i understand wat ur saying now... so is my post about being able to see the past wrong?

Somewhat. What peacefulwarrior is saying is absolutely correct, which is that what you are seeing is not the past, it is light which originally began its journey towards the observer in the past. As for seeing into the past with the Hubble Telescope, it can detect photons travelling away from the center of the universe, and their pattern can give us clues to the events of the past. However, to be certain this will unravel the secrets of the creation of the universe is a jump we simply cannot be certain to make. I, for one, am skeptical it will provide definitive evidence of anything.

the only certainty is the uncertain

You are looking at the past in a sense that if we see a star collapse or explode from Earth, chances are that the even happened several thousand if not million years ago, because thats how long it took the image of that event (carried by light) to arrive on earth to be seen by us. In effect every time we look at the night sky we are looking at the past. As the Hubble telescope can view things so distant that we cannot see them normally, focusing obscure and distant light, it can vieww things that occurred even earlier.

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