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Old Mar 20, 2004, 12:08 AM   #1
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Default does light travel in a straight line? --- OFF TOPIC

call me crazy but, does light realy travel in a stright line?
think about it...

if you point a laser pointer in front of a black hole, the light gets sucked in
this tells me that light has mass, because of the gravitational pull of a black hole anything with mass near it is sucked in
we all know that the earth hase a gravitational pull, however much weaker then a black hole, so does it not make since that light would be pulled down by the earth's feild? just an infinitly small amount?
i have told two people this, and both looked at me like i was crazy...
am i?

can some one help me find an articale on this?

thanks,
brad
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Old Mar 20, 2004, 12:37 AM   #2
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can you spell "GOOGLE"?
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Old Mar 20, 2004, 12:55 AM   #3
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I'm sure it can be calculated if you take the mass of a photon (???), it's speed (300000km/s), Earth's gravity (~9.8m/s2), etc... but the last time I messed around with physics calculations was a long long time ago, and my brain just doesn't have the same computational power anymore :lol:

Oh, but I do remember reading somewhere that a round aglomerate of galaxies or stars worked like a lens, bending light from a far away object behind the aglomerate and making that object seem closer than it really was. I think that's what the article said, perhaps from Popular Science.
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Old Mar 20, 2004, 12:58 AM   #4
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Read Stephan Hawking's books. He can actually make sense of this.
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Old Mar 20, 2004, 1:28 AM   #5
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Quote:
Originally Posted by marokero
Oh, but I do remember reading somewhere that a round aglomerate of galaxies or stars worked like a lens, bending light from a far away object behind the aglomerate and making that object seem closer than it really was.
So thats how the mirror on the passenger side of my car works??? It has an agolmerate in it :P
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Old Mar 20, 2004, 8:26 AM   #6
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Einstein's infamous theory was about this. He did specify that light is bent by gravity, and I'm sure the earth's gravity is sufficient to bend the light travelling past it from a distant source to an observer say in the neighbouring galaxy.

Also, the semi-sci fi story of John Titor (google is your friend) posted some pictures, one of which was of a lazer pointer's red light being bent into an arc, supposedly due to the gravitational propulsion of his time machine.

Titor/time travelling is a whole nother pandora's box....
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Old Mar 20, 2004, 11:15 AM   #7
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Quote:
Originally Posted by Onyx
Einstein's infamous theory was about this.
You must be referring to General Relativity since Special Relativity (E=MC squared etc) didnít include gravity. I never knew General Relativity was ďinfamousĒ. My limited intellect always thought it was pretty good.
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Old Mar 20, 2004, 11:23 AM   #8
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Light has no mass and is therefore is not affected by gravity. According to Einstein's general relativity, (not special relativity),What actually happens is: anything that has mass makes a distortion in the space-time continuum. The bigger the mass, the more distortion. The distortion curves space-time around the object. When something goes through this curvature, its direction is altered. Think of a rubber sheet. If you roll a marble across the rubber sheet, it will travel in a straight line. Now, if you put a bowling ball in the middle, there will be a curvature in the shape of the sheet. Now if you roll a marble it will follow the curved path around the ball. Large masses such as black holes, neutron stars, etc, produce a large enough curvature that we can see the results from here. To answer your question, light is not affected by gravity, but space-time is. The light thinks it's going in a straight line, but it is going in a straight line through curved space and the result to an outside observer looks like the light is following a curved line through straight space.
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Old Mar 20, 2004, 12:07 PM   #9
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Quote:
Originally Posted by LTBerry
Light has no mass and is therefore is not affected by gravity.
My limited understanding of General Relativity and gravity is that particles with mass arenít drawn to very massive objects by a ďpullingĒ effect of gravity on their mass either. They also follow the space time curvature created by gravity into the massive object. Other than generating a tiny amount of space/time warp themselves I donít think objects with mass are affected by gravity any more than objects without it. Particles with mass canít go fast compared to light and are affected by the curvature longer.

If you shoot a steel bullet an inch past a strong magnet is isnít going to be deflected much. Roll the same bullet an inch past the magnet and the magnet will capture it.

Gravity also drains energy from light by red shifting it. Red is a lower energy state. I have no idea how the red shift relates to Einsteinís concept of gravity acting by warping space/time and not by an actual attraction force.
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Old Mar 20, 2004, 12:50 PM   #10
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Just get your subject to stand a little closer!

:?
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