Talk:Redshift

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Nonlinear scaling factor[edit]

The Hubble red shift problem must be generalized mathematically to include other scaling factors than linear. Try searching Google with the phrase "Hubble red shift exponential". SyntheticET (talk) 20:43, 20 September 2014 (UTC)


Redshift used for Radar Guns?[edit]

This article claims that Redshift is used in Police Radar Guns. However, these devices are not "spectroscopes" and do not measure redshift. This effect should be properly attributed to Pulse Reflection Orrerysky (talk) 20:08, 30 November 2013 (UTC)

Doppler radar and radar gun both disagree with you, and cover the topic in rather more detail.--JohnBlackburnewordsdeeds 20:27, 30 November 2013 (UTC)
radar gun does not appear to be a spectroscope capable of analyzing absorption lines. Unrelated topic. Orrerysky (talk) 20:34, 30 November 2013 (UTC)
Please read it again: it does not say spectroscopes are used in radar guns.--JohnBlackburnewordsdeeds 20:50, 30 November 2013 (UTC)
The Redshift Effect is very specifically in regards to the measure of absorption lines & emission lines in a spectrograph. Given that radar gun is not measuring a displacement in absorption or emission lines, I fail to see how it relates to the topic. I propose this section be removed and added to Pulse Reflection Orrerysky (talk) 20:54, 30 November 2013 (UTC)
"Redshift" refers to the shifting of the spectrum of an object toward longer wavelengths. It does not refer to simply measuring absorption and emissions lines in a spectrograph otherwise there would be no such thing as photometric redshift, for example. jps (talk) 23:20, 30 November 2013 (UTC)
That's great, perhaps you can explain to me how a radar gun works to measure redshift when its specifically calibrated for Pulse_(physics)#Pulse_Reflection of a signal with the same frequency and wavelength as what was emitted. This is bad science and misrepresents both redshift, pulse reflection, and radar guns. Orrerysky (talk) 16:19, 1 December 2013 (UTC)
Most radar guns use Continuous-wave radar. jps (talk) 23:11, 1 December 2013 (UTC)

Edit 6 March[edit]

Can you explain why "none of these edits really helped"? Especially since it's my understanding that the current text is factually wrong. Banedon (talk) 01:13, 7 March 2014 (UTC)

suspected error in redshift for theta= 0 formula[edit]

under redshift formulae in the dopler effect section it says:

1+ z = \frac{1 + v \cos (\theta)/c}{\sqrt{1-v^2/c^2}}

and for motion solely in the line of sight (θ = 0°), this equation reduces to:

1 + z = \frac{1}{\sqrt{1-v/c}}

I'm pretty sure this is simply not true. I cannot get to that form.

can anyone verify?

Indeed, I fixed it. Thanks for pointing out! Banedon (talk) 14:24, 11 November 2014 (UTC)