?'s about light

[UglyEd]

I had some questions about light. Mb some1 could explain 2 me. I know about red shift and blue shift. If the object is moving towards you it's color shifts to blue and vice versa. Is this because if the object is moving towards you it compresses the light waves and if moving away it stretches the light waves? What would an object moving near light speed look like if viewed from the side passing by you? Would the light have like a rainbow effect blue to red shift in colors? When light near a Black Hole enters past the event horizon is the reason you don't see light because the light waves are pulled to like a flate line? If you are moving towards or away from a stationary object are the shifts in light the same? If that is true then would it mean that light waves don't get stretched out compressed but by moving toward or away you are changing the percieved time between the modulations in the lights frequency. Like shortening or lengthing the percieved time between the the peaks in a light waves frequency?

Thanks Ed

[The Binary Monster]

I know about red shift and blue shift. If the object is moving towards you it's color shifts to blue and vice versa. Is this because if the object is moving towards you it compresses the light waves and if moving away it stretches the light waves?Yes, yes it is.

What would an object moving near light speed look like if viewed from the side passing by you?If it was moving to the side of you then for you to see it light would have to be emitted from it in your direction. In this case it would be blueshifted as the object approached, redshifted as it moves away from you, and it would not be altered at all as it passed directly perpendicular to you.

Would the light have like a rainbow effect blue to red shift in colors?Kind of, though I'm not certain what you mean.

When light near a Black Hole enters past the event horizon is the reason you don't see light because the light waves are pulled to like a flate line?In theory, no. According to the current ideas, you do not see the light because the velocity of the light, c, is not larger than the escape velocity of the event horizon. Basically, the light cannot reach your eyes because it cannot escape from the event horizon.

If you are moving towards or away from a stationary object are the shifts in light the same?I don't believe that moving towards or away from an object will shift its wavelength at all. But then again, I'm not sure.

If that is true then would it mean that light waves don't get stretched out compressed but by moving toward or away you are changing the percieved time between the modulations in the lights frequency. Like shortening or lengthing the percieved time between the the peaks in a light waves frequency?I'm not too sure of my last statement, so I better leave that to someone else.

:: Ben ::

[Nenad]

I had some questions about light. Mb some1 could explain 2 me. I know about red shift and blue shift. If the object is moving towards you it's color shifts to blue and vice versa. Is this because if the object is moving towards you it compresses the light waves and if moving away it stretches the light waves?


The resaon light is blue and red shifter is because of the expansion of spce itself. When light is emitted from a star, space is expanding all the time and this expnsion of space ellongates the wavelength of light, amking it red shifted.

[h8ter]

The resaon light is blue and red shifter is because of the expansion of spce itself. When light is emitted from a star, space is expanding all the time and this expnsion of space ellongates the wavelength of light, amking it red shifted.

I think that is only true when the direction of emission is opposite of the direction of star movement. When light is emitted from a stationary object, it appears to be normal. Only then is the wavelength inversly proportional to it's frequency (Maxwell). If you light compared to a moving system, Maxwell's definition of light being emitted from a stationary source does not apply.

[Nenad]

I think that is only true when the direction of emission is opposite of the direction of star movement. When light is emitted from a stationary object, it appears to be normal. Only then is the wavelength inversly proportional to it's frequency (Maxwell). If you light compared to a moving system, Maxwell's definition of light being emitted from a stationary source does not apply.

:uhh: :uhh: :uhh: :uhh: Im just telling him why light from other stars is red shifted. :uhh: :uhh: :uhh: :uhh:

[Chronos]

Just for clarification, red shift due to expansion only occurs between galaxies, not within them. Any red shift observed in light from stars within our galaxy is due to proper motion. Also, any light passing by in front of you is not visible. Only light that 'hits' you can be seen.

[Vern]

Moving toward or away from a light source does blue-shift red-shift the light. That's the way police radar works :smile:

[Vern]

Just for clarification, red shift due to expansion only occurs between galaxies, not within them. Any red shift observed in light from stars within our galaxy is due to proper motion.
Are you sure about this ? I've never seen it stated that way, and can't imagine an equation that would expand the universe but leave out lumps where galaxies reside :smile: But I could be wrong.

Vern

[pervect]

Are you sure about this ? I've never seen it stated that way, and can't imagine an equation that would expand the universe but leave out lumps where galaxies reside :smile: But I could be wrong.

Vern

This is mentioned in the sci.physics.faq

http://math.ucr.edu/home/baez/physics/Relativity/GR/expanding_universe.html

Mrs Felix: Why don't you do your homework?
Allen Felix: The Universe is expanding. Everything will fall apart, and we'll all die. What's the point?
Mrs Felix: We live in Brooklyn. Brooklyn is not expanding! Go do your homework.

(from Annie Hall by Woody Allen)

Mrs Felix is right. Neither Brooklyn, nor its atoms, nor the solar system, nor even the galaxy, is expanding. The Universe expands (according to standard cosmological models) only when averaged over a very large scale.


Basically, things that are bound together don't expand as the universe expands. Atoms are bound together by the electromagnetic force, the galaxy is bound together by gravitation.

[existence]

...and it would not be altered at all as it passed directly perpendicular to you.



:: Ben ::

Wrong. Look up 'transverse doppler shift'. You would be correct if there such a thing as absolute time (classical doppler effect).

[what_are_electrons]

Moving toward or away from a light source does blue-shift red-shift the light. That's the way police radar works :smile:

Could the Compton Effect be interpreted as a Doppler effect on the wave properties of X-rays and the shift to longer wavelength that depends only on angle?

[Vern]

Basically, things that are bound together don't expand as the universe expands. Atoms are bound together by the electromagnetic force, the galaxy is bound together by gravitation.
This must be only in theory; I can't imagine reality operating that way :smile: I thought that there was gravitational attraction between galaxies also ??

Vern

[Vern]

Could the Compton Effect be interpreted as a Doppler effect on the wave properties of X-rays and the shift to longer wavelength that depends only on angle?
In the Compton Effect energy is transferred so I don't think the doppler effect could be to blame :smile:

Vern