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Thread: Is it true light takes so long to reach earth that the stars in the sky...

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    Default Is it true light takes so long to reach earth that the stars in the sky...



    ...aren't even there any more? By the time the light shining from the stars reaches earth, billions of years pass so the night sky appears as it did billions of years ago and not how it is in space where they are located since they could just as well died off and are no longer emitting light.

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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    Yes it is true ,because the distance is too far apart. So light needs some time to travel long distances.

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    Maybe I'm wrong but the stars we see with naked eyes at night are located in the milky way, we do not see individual stars in the other galaxys. If the milky way is aprox. 100,000 light years large, the 'oldest' light our eyes see is +/- 100,000 years old, which is not that old for a sun. Am I wrong?

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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    Maybe I'm wrong but the stars we see with naked eyes at night are located in the milky way, we do not see individual stars in the other galaxys. If the milky way is aprox. 100,000 light years large, the 'oldest' light our eyes see is +/- 100,000 years old, which is not that old for a sun. Am I wrong?
    Yes you are right, but i didnt understand your last statement , i didnt get what you meant in that statement.

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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    Yes,some stars we look at may be dead.

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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    Quote Originally Posted by Danthemanmtl View Post
    Maybe I'm wrong but the stars we see with naked eyes at night are located in the milky way, we do not see individual stars in the other galaxys. If the milky way is aprox. 100,000 light years large, the 'oldest' light our eyes see is +/- 100,000 years old, which is not that old for a sun. Am I wrong?
    Actually yes, your statement is incorrect in as much as looking at the age of the star. While the light you may see from the farthest star in the MW may be 100,000 years old when it hits your eye, the star itself may have been born billions of years ago. So you have to take into account that any star you see in all likelyhoold is way older than the actual light you see at a particular moment in time.
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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    ^ Yep Yep
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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    Quote Originally Posted by caligrl View Post
    ...aren't even there any more? By the time the light shining from the stars reaches earth, billions of years pass so the night sky appears as it did billions of years ago and not how it is in space where they are located since they could just as well died off and are no longer emitting light.
    That is quite true. Because the speed of light is finite, at 186,000 mile per second, then it takes time for the light from distant stars, nebulae, galaxies to reach the earth. One thing to consider is that every time you look up in the night sky, you are looking back in time. Even looking at the moon you are looking a very short distance into the past. The light takes just over 8 minutes to reach the moon from the sun, then about 1.3 seconds to reach us from the moon. Everything else just gets longer and longer. Consider the speed of light again - 186,000 miles per second. There are 60 seconds in a minute; there are 60 minutes in an hour; there are 24 hours in a day; there are 365 days in a year. That is how far light will travel in a year or known as the light year. The nearest star (other than the sun) is Proxima Centauri at 4.2 light years away. The current accepted nearest galaxy to earth (though this is being disputed) is the Canis Major Dwarf Galaxy at 25,000 light years. Galaxies have been found over 13 billion light years away. All the stars you see when you look up at the night sky are within the Milky Way, which currently has an accepted diameter of about about 100, 000 to 120,000 light years.

    Regarding your question about stars potentially having died off and we aren't aware of it, that is correct. Take for example, Betelgeuse in Orion. It is about around 643 light years away, so the light we see is that old at any given time. It is a red supergiant, that most likely will end its life as a Type-II supernova. Could that event already have ocurred? Most definitely, since it will take about 643 years for the visual event to reach us. The stars we see reported as supernovae each year, have long ago met their fate by the time we are aware of it. But just as stars are dying, stars are being born all across the observable universe. So I think it will be quite a while before we run out of starlight to take pleasure in.
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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    Gotta jump off-topic here..... DanTheMan, I love your avatar! The motion gives the pic an almost 3D aspect! really cool! You sould post a "how to" in the AP forum.

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    Default Re: Is it true light takes so long to reach earth that the stars in the sky...

    I think we can say that this is true for 'some' stars, but others are so close to us that they are still alive.. For example, Alpha Centauri is only 4.37 light years away from us:

    https://en.wikipedia.org/wiki/Alpha_Centauri

    I remember that this is the closest star system to us, since I am old enough to have watched the family sci-fi TV show "Lost in Space", where the Robinson family was on a journey there and 'got lost'

    Hey, just found this colorful infographic:

    http://www.space.com/18964-the-neare...fographic.html
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