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Light - gains or doesn't gain speed from source
There seems to be some conjecture whether we see light gaining a direction
component from a moving star. Is that correct? Surely, if it does, we will see a 'streak' of light in the sky as light from various sides of the star gets to us? Cheers, Alex. |
#2
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Light - gains or doesn't gain speed from source
Observers in all reference frames measure light in a vacuum traveling at the
same speed, c. This goes all the way back to Special Relativity, and I'm not aware of any serious conjecture to the contrary. Light from objects moving towards us is blue shifted, while light from objects moving away from us is red shifted, but the speed is the same in both cases. Because of the great distances involved, the motion of stars moving tangentially to us can only be measured over time. None of them streak. The faster moving ones, like Barnard's star, can be seen to move over a period of years. Otherwise, detection of proper motion is a slow and tedious process. "Alex Kudrasev" wrote in message ... There seems to be some conjecture whether we see light gaining a direction component from a moving star. Is that correct? Surely, if it does, we will see a 'streak' of light in the sky as light from various sides of the star gets to us? Cheers, Alex. |
#3
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Light - gains or doesn't gain speed from source
The speed of the star is much less than the speed of light, so there's no
possibility that photons arriving from different points along the star's trajectory would arrive at the same time. "Alex Kudrasev" wrote in message ... Precisely my question - Why don't stars travelling tangentially streak? If light inherited direction from a body's motion, different direct rays from the spherical surface would appear to us from different times in the body's history. So what is the answer? Alex Kudrasev "Bill Nunnelee" wrote in message rthlink.net... Observers in all reference frames measure light in a vacuum traveling at the same speed, c. This goes all the way back to Special Relativity, and I'm not aware of any serious conjecture to the contrary. Light from objects moving towards us is blue shifted, while light from objects moving away from us is red shifted, but the speed is the same in both cases. Because of the great distances involved, the motion of stars moving tangentially to us can only be measured over time. None of them streak. The faster moving ones, like Barnard's star, can be seen to move over a period of years. Otherwise, detection of proper motion is a slow and tedious process. "Alex Kudrasev" wrote in message ... There seems to be some conjecture whether we see light gaining a direction component from a moving star. Is that correct? Surely, if it does, we will see a 'streak' of light in the sky as light from various sides of the star gets to us? Cheers, Alex. |
#4
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Light - gains or doesn't gain speed from source
"Greg Neill" wrote in message ... "Bill Nunnelee" wrote in message arthlink.net... The speed of the star is much less than the speed of light, so there's no possibility that photons arriving from different points along the star's trajectory would arrive at the same time. True. On the other hand, jets from active galaxies are moving at a significant fraction of the speed of light, and if the geometry is right with respect to source and observer, will appear to be moving superluminally. So I take it that we can observe 'streaks' (they appear as lines) in fast moving light sources? Alex Kudrasev |
#5
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Light - gains or doesn't gain speed from source
"Alex Kudrasev" wrote in message
... "Greg Neill" wrote in message ... "Bill Nunnelee" wrote in message arthlink.net... The speed of the star is much less than the speed of light, so there's no possibility that photons arriving from different points along the star's trajectory would arrive at the same time. True. On the other hand, jets from active galaxies are moving at a significant fraction of the speed of light, and if the geometry is right with respect to source and observer, will appear to be moving superluminally. So I take it that we can observe 'streaks' (they appear as lines) in fast moving light sources? Well, jets are more or less continuous in nature, sometimes with lumpy inclusions. But I can't think of a geometry for the source and observer that would have light from different points on the trajectory of the same "lump" arrive at the same time at the observer. |
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