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Posted by: nat ® 12/13/2002, 12:48:55 Author Profile Mail author |
I was wondering, carring on some of the topics about black holes and such... they say the nearest galaxy is about 4 light years away. How do we know that? Light speed is based on how fast a proton can travel/accellerate based in a vacuume, no friction and no gravity based on the potenial energy behind it, ie, nuclear fission. Ie, light from a perfect nuclear explosion could only accelerate so fast based on the mass behind it. You only can use as much energy that is availible. Like if I put you on a swing and pushed you, you would only accelerate based on how hard I pushed you. If i pushed you hard, you would move fast. If i lightly pushed you wyou wouldn't be moving very fast as well due to gravity you wouldn't swing as far. If there was no gravity you would be moving slowly untill you stopped...unless i pushed you harder,then you would move faster in a vacuume. Now, if I were a light beam from a star, in a perfect vacume you could measure my speed and how long it took me to get here and there. That would be easy. However if I was a light beam and there was a big gravitation feild near by I would tend to bend towards it. Now if there were a lot, i would be bending and twisting. And if that were so, wouldn't it take longer for me to reach a desination then it would with out? It would be like traveling on a flat straight road verses in the mountains going up and down hills and around mountains. And assuming the cars were traveling at the same speed. and the same distance, only one is staight the other is twisted. In the car example, wouldn't the car traveling through the mountains take longer to get to the destination as the one traveling striaght? So, wouldn't a light beam take longer to get some where. So if we measure 4 light years, it could be probably it could only be 2 light years away because of the bending light. As well, if light bends, wouldn't time bend too? So could time bend it's self in such a manner we could be seeing the light delayed in time? Just wondering... I love to think of wierd stuff like this..hehe. Not just wierd stuff about LDS, but everything! Being wierd is fun sometimes. --nat |
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a book you'll love Re: Light years -- nat Top of thread Archive
Posted by: rpcman ®
12/13/2002, 13:03:02
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Re: Light years Re: Light years -- nat Top of thread Archive
Posted by: Martin ®
12/13/2002, 17:09:07
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It's great that you're curious and interested in science! That's an extremely valuable character trait, and it will serve you well.
However, may I recommend that you apply that curiosity more carefully to your science studies? Are you aware that just about everything you said in your post is mistaken to some extent, sometimes enormously so?
I started out trying to point you in the right directions, but my corrections became so voluminous that I thought it best to let you do some of your own reading and research so it will be more meaningful for you and stick with you better.
I recommend: Introducing the Universe, by Felix Pirani and Christine Roche as a good place to start.
Have fun!
- Martin
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Parallax Re: Light years -- nat Top of thread Archive
Posted by: The Vines ®
12/13/2002, 18:21:34
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Distances in astronomy are not measured by seeing how fast light got here. How would we know how long a photon has been travelling? In fact, for the photon itself the time from emission to absorption by our instruments was instantaneous, there was no passage of time, or travel through space.
You ask how do we know that a galaxy is X light years away? Its not by measuring how long it took light to get here, but rather through the use of complex instruments and calculations that measure the apparent movement of a celestial body compared to others as the earth travels around in its revolutions around the sun.
Here is a website that explains "paralllax."
www.eg.bucknell.edu/physics/astronomy/ as101/specials/parallax.html
Regards
TV
Modified by The Vines at Fri, Dec 13, 2002, 18:22:05
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