Wikipedia:Reference desk/Archives/Science/2021 April 10

= April 10 =

What's the explanation for 10 milion colours?
If the visible light is between 380-750 nm of wavelength, then I'd expected to have 370 colours (each colour for 1 wavelength), but I saw that scientists say there are around 10 million colours. What's the explanation for that? --ThePupil (talk) 04:13, 10 April 2021 (UTC)
 * Light is not quantized by the nanometer, that's an arbitrary human unit. We can distinguish colors when presented side by side, testing shows that we can perceive about 10 million such distinctions. See Color vision. Abductive  (reasoning) 05:50, 10 April 2021 (UTC)
 * I'm old enough that when I learned about wavelengths of light, they were customarily measured in angstroms. Should I have expected 3,700 distinguishable colors to exist?
 * Anyway, consider also that the light from a particular object will typically consist of a range or mixture of wavelengths, but we still see it as one color. Colors based on a single frequency of light are not the only kind we can distinguish. --184.147.181.129 (talk) 06:04, 10 April 2021 (UTC)
 * Indeed, light "of wavelength between 380 and 750 nm (3800 to 7500 Å)" is pure monochromatic light. The human colour perception system can only distinguish a few hundred spectral colours standardized at a uniform brightness. --Lambiam 12:08, 10 April 2021 (UTC)
 * You may be interested in All the Colors We Cannot See - Tetrachromacy in Humans. Alansplodge (talk) 15:05, 10 April 2021 (UTC)
 * " light "of wavelength between 380 and 750 nm (3800 to 7500 Å)" is pure monochromatic light." Erm, no. That's in fact pretty much the entire visible spectrum, nowhere near monochromatic. Actual monochromatic light will have a range of maybe 10 nm, depending on the source. Fgf10 (talk) 18:35, 10 April 2021 (UTC)
 * I think Lambiam meant "of any one wavelength between...". --184.147.181.129 (talk) 20:33, 10 April 2021 (UTC)
 * Right-o, meant to correspond to the parenthesis "(each colour [of 370 colours] &thinsp; for 1 wavelength &thinsp; [between 380–750 nm])" in the original question, which clearly reveals that the question is based on the premise that all visible light has a specific wavelength, just like any person between the ages of 18 and 20 has a specific age. The light of extra-spectral colours, such as pink and magenta, does not have "a wavelength", so when any (visible) light is specified as being "of wavelength", it implies (to me) it is monochromatic light. --Lambiam 11:57, 11 April 2021 (UTC)

An interesting Covid vaccine question
I had another engineer ask me an interesting question today.

mRNA causes the cells to build a foreign protein. The protein molecules cause an immune response. Later the immune system identifies and destroys the actual pathogen. So, does the mRNA keep building the protein forever? Or is the mRNA "used up" and you only get as many protein molecules as you got mRNA molecules? Or is it somewhere between with one mRNA building more than one protein but eventually getting "worn out" instead of producing proteins forever? I tried to figure this out from reading our RNA vaccine article but it wasn't clear to me. --Guy Macon (talk) 21:39, 10 April 2021 (UTC)
 * According to Messenger RNA, the mRNA lasts from a few minutes to several days, so your final supposition appears to be correct.- gadfium 21:46, 10 April 2021 (UTC)
 * mRNA is also degraded when processed (it loses some A codons at the end, similar to how DNA loses telomeres). This site has a discussion of the full mRNA sequence of the BioNTech/Pfizer vaccine - it makes for fascinating reading (at least for geeks like me). --Stephan Schulz (talk) 11:43, 12 April 2021 (UTC)