What Are Color Shifts Like Redshift in Science?

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Discussion Overview

The discussion revolves around the concept of color shifts in light, specifically redshift and blueshift, and their implications in physics. Participants explore the nature of these shifts, their relation to motion, and the broader implications of light behavior in various scenarios, including hypothetical thought experiments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Thought experiments

Main Points Raised

  • One participant seeks a simple explanation of redshift and questions whether green or blue shifts exist.
  • Another explains that blueshift is the opposite of redshift, occurring when an object approaches the observer, compressing light waves.
  • A participant presents a thought experiment involving a green shrub and questions whether its apparent movement is a trick of light.
  • Some participants clarify that color shifts are related to the frequency of electromagnetic waves and that the terms red and blue are used to describe shifts at the ends of the visible spectrum.
  • There is a discussion about the implications of an object moving at high speeds, including a hypothetical scenario involving a spinning baseball and its color shifts as it approaches the speed of light.
  • One participant expresses confusion about the phrase "the speed of light squared" in the context of Einstein's equation E=mc², seeking clarification on its meaning.
  • Another participant emphasizes that nothing with mass can achieve the speed of light, questioning the relevance of visualizing such scenarios.

Areas of Agreement / Disagreement

Participants express various viewpoints on the nature of color shifts and their implications, with some agreeing on the definitions while others present differing interpretations or hypothetical scenarios. The discussion remains unresolved on several points, particularly regarding the implications of high-speed motion and the understanding of light speed in relation to mass.

Contextual Notes

Participants express uncertainty about the implications of color shifts and the nature of light speed, with some statements relying on assumptions that are not universally accepted. The discussion includes speculative scenarios that are not grounded in established physics.

eggman
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What is 'redshift' ?

one poster says depending on the color you see it will tell you which way the picture is moving..

ex:either away from the observer or towards the observer..

please explain in SIMPLE terms what these 'shifts' are...

is there a green shift or a blue shift in science?

..(i hope i put this idea in the proper area of the forum) :rolleyes:
 
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There is indeed a 'blue' shift, which is the opposite of the 'red' shift. Both occur because the speed of light is constant. An object approching you is traveling at speed a, for instance. Since the speed of light is c, the logical first thought is that the light would then be approacing you at a + c. That can't happen, though, because the light is restricted to c. Instead, the light waves become 'compressed' (sort of like a spring). The waves get closer together (shorter wavelength), which raises the frequency (in the case of visible EM, toward the blue end of the spectrum).
A redshift is the opposite, wherein a receding object has the light waves behind it 'stretched' to a longer wavelength (red end of the spectrum).
 
Thanks you for your reply...

Look at this logic and see if it makes sense?

I look out my kitchen window...there is a green shrub/tree in the distance..

Is it moving away from me...or towards me?

..or is this apparent movement a 'trick of the light'?

This is very complex I feel because of the 'observers' question can be

false...that is to say not a True Scientific Question..

Needless to say I am not good at science...
 
I think that you're misinterpreting the use of colour words in Doppler terms. Whatever the initial frequency of the EM is, it will be either increased or decreased according to a specific formula related to its motion. 'Red' and 'blue' are simply used to indicate that because they're the extreme ends of the EM spectrum that humans can see. Something that's blue to start with, approaching you fast enough, will be shifted up to ultraviolet or even gamma, which aren't visible. Something that starts out in ultraviolet will climb to x-ray or gamma status.
The bush is green due to the pigmentation of its cells, and has nothing to do with whether or not it's moving. (It isn't, by the way, unless you have an alien in your yard.) If someone were to uproot that bush and throw it at you at a good percentage of light speed, it would then grow bluer.
 
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I think I see the idea...

The next time I see one of those trees vanish I will know its moving fast and could possibly wack me! :smile:

Thanks for your help Danger :-p

...the moral of the story...'Watch out for things that suddenly disappear..it will indicate a 'shift' in the continuum and sh*t is
in the process of hurling itself about SpaceTime!
 
I wouldn't go putting that on an exam paper, but it sounds good to me. :biggrin:
 
.'Watch out for things that suddenly disappear..it will indicate a 'shift' in the continuum and sh*t is
in the process of hurling itself about SpaceTime!
And watch out for SpaceTigers!
 
Oh, yes! They're the worst! Bengals are timid little pussycats compared to the Space variety.
 
eggman said:
is there a green shift or a blue shift in science?
The names redshift and blueshift are used because red and blue are on opposite ends of the spectrum. If the wave is shifted longer, it is "redshift", if it is shifted shorter, it is "blueshift".

Doppler shift also works on sounds. When a train passes you and the pitch of its whistle changes - first rising, then falling, that's the same as blue then red shift - just with sound instead of light.
 
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  • #10
Thought Experiment

1)..If a man had a baseball attached to a wire and began to

spin it in a circle above his head what would you see as the ball

approached the speed of light...
 
  • #11
You would see a spinning ball. I assume you mean what color, if so, because it is spinning, one side would be red, and the other blue as it approached the speed of light. One side is relatively moving toward you, and the other, relatively moving away.
 
  • #12
If the ball achieved 'c' (speed of light) would it disappear?

or what would you observe?
 
  • #13
The ball wouldn't achieve the speed of light.
 
  • #14
I put some stuff about speed and vibration over in the metaphysics section...I was attempting to understand what would occur
if an 'object' were capable of remaining intact and going lightspeed.

I am attempting to wrap my brain around Time Travel...and its different perceptions

Its very hard to grasp
 
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  • #15
You would notice nothing out of the ordinary, regardless of the speed of the ball.
 
  • #16
And nothing with mass, be it a ball, a bat, or an umpire, can achieve light speed. There's no point in trying to visualize what would happen if it did, because it's flatly impossible.
 
  • #17
You would notice nothing out of the ordinary, regardless of the speed of the ball.
Are you dismissing my conjecture?

because it is spinning, one side would be red, and the other blue as it approached the speed of light. One side is relatively moving toward you, and the other, relatively moving away.
 
  • #18
Mk said:
Are you dismissing my conjecture?

Why would the baseball be 'spinning'?

~H
 
  • #19
I think that he means revolving around the anchor of the string, not rotating on its own axis.
 
  • #20
Help Please...

If nothing can move faster than the Speed of Light...

then please explain the phrase 'The speed of Light Squared' (E=MC2)

that would be 186,000 mps X 186,000mps

...what am I missing :cry:

even in the mutiplication its still called 'the speed of light' :frown:
 
  • #21
It's merely the number squared, not the speed. I can square my age on paper; it doesn't make me suddenly 2,500 years old.
 

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