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Our Earth, being a beautiful blue orb, has an overall perceived wavelength of somewhere near 470 nm, that being the wavelength of light blue, because the oceans play an enormous role in the weighted average of all of the Earth's colors.

But what about the whole universe? The Earth is nothing in comparison to the host of multicolored stars, ranging from deep red to fiery blue.
Taking into consideration the number of stars and each separate color's weighted average,
could we calculate the average color of the universe?

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  • $\begingroup$ Why stop at stars? Dust clouds are important, too. $\endgroup$ – HDE 226868 Jul 28 '15 at 18:42
  • $\begingroup$ I have a sneaking suspicion that the color is infrared. $\endgroup$ – called2voyage Jul 28 '15 at 19:20
  • $\begingroup$ Actually, though I can only find references that make the claim (e.g. Mukhanov 2005 and Hobson et al. 2006), but none that do the calculation, the photon budget is dominated by CMB photons, which are in the microwave region. Of course this is outside the human eye response, but I think the tail of the CMB photons would make the average color reddish. $\endgroup$ – pela Jul 28 '15 at 20:20
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In RGB Hex notation, it's #FFF8E7, a light beige color called "Cosmic Latte".

The color was calculated by a team of astronomers at Johns Hopkins University in 2002 from a sample of over 200,000 galaxies as a side-effect of a more "serious" study on the spectral features of different galaxies in relation to star formation.

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According to astronomers at Johns Hopkins University, it's beige. Note, they previously announced it was turquoise, but they identified a bug in their calculations, redid the numbers, and now it was determined the average color is beige. Kind of boring, yes, but kind of what you'd expect.

In short, they collected "detailed light measurements from more than 200,000 galaxies. They then constructed a "cosmic spectrum," which represents all the energy in the local universe emitted at different optical wavelengths of light" and averaged it. More details at link below.

NPR : The Color of the Universe Is...

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The wave lengths emitted by hydrogen are a good candidate. Limiting the idea of color to the narrow band that earth's current atmosphere does not filter out and is not emitted in great quantiles to our sun out will probably miss the mark.

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