Why are things blue shifted and not violet shifted?

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Objects moving towards us are referred to as blue shifted, while those moving away are red shifted, with these terms denoting shifts in frequency rather than color. The distinction between blue and violet is clarified, noting that violet is a spectral color with shorter wavelengths than blue, while purple is a perceptual color. The discussion highlights that blue and red are merely labels for frequency changes, not direct indicators of visible color. Misunderstandings arise from common perceptions of color order in the spectrum. Overall, the conversation emphasizes the importance of understanding the physics behind these terms rather than relying solely on visual associations.
Entropee
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If objects are moving away from us, they are known as red shifted, so why are objects moving towards us blue shifted and not violet shifted?
 
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Semantics. Blue-shifted objects are not necessarily blue: an object emitting at 5 um moving towards us is still blue shifted even though it is way outside the visible spectrum.
 
Entropee said:
If objects are moving away from us, they are known as red shifted, so why are objects moving towards us blue shifted and not violet shifted?

"blue" and "red" are just labels used to denote upshift or downshift in frequency.
 
Oh ok, yeah I just thought it was odd since most elemtary school students even know that purple comes after blue using roygbiv. Thanks :]
 
Entropee said:
If objects are moving away from us, they are known as red shifted, so why are objects moving towards us blue shifted and not violet shifted?

I didn't know that.

So acceleration of the object in relation to us alter wave length?

:eek:
 
Impagliazzo said:
I didn't know that.

So acceleration of the object in relation to us alter wave length?

:eek:

What? Entropee said nothing of the kind.
 
Entropee said:
Oh ok, yeah I just thought it was odd since most elemtary school students even know that purple comes after blue using roygbiv. Thanks :]
Actually, purple is not the same as violet. Violet is a spectral color consisting of wavelengths shorter than blue, but purple is a perceptual color seen only when both blue and red wavelengths are present.
 
Oh lol, my bad, I guess it's time for me to go back to Elementary school?
 
ideasrule said:
What? Entropee said nothing of the kind.

But what he said is right?

I want to know why!

Edit: Ok so I guess I just got pretty inventive with lack of clear information. LOL
 
Last edited:

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