Hinduism & science: Blueness of the Sky is an optical Illusion
Blueness of the sky is caused by the scattering of the sunlight, this phenomenon is called Rayleigh Scattering named after the physicist Lord Rayleigh (12 November 1842 – 30 June 1919) who first explained it.
The phenomenon is stated asÂ
The shorter wavelength of Blue light will scatter more than the longer wavelengths of Green and especially Red light, giving the sky a Blue appearance.
[Image: Wavelengths of Colors]
- The shorter wavelengths of Violet, Indigo, Blue, Green scatter to varying degrees and create the illusion of Blueness of Sky.
- Compared to Violet, our eyes are more sensitive to Blue, thus human eye sees Sky as Blue rather than variation of Violet
"Blueness of the Sky is an optical Illusion" in Yoga Vasishta
Blueness of the sky was explained first by Lord Rayleigh in Later 19th or early 20th century. Was it known to humans earlier that this could be just an illusion and there isn't anything solid out there which is called sky?
It is possible that other cultures, primitive astronomers knew it. I have come across these verses in Yoga Vasishta which say "color of Sky" is result of an optical illusion.
Yoga Vasishta is dated back as early as 4th-5th Century and as late as 12th-14th Century. Hindus believe Yoga Vasishta to be as Old as 5000 Years, given that it was a conversation between Lord Rama & Vasishta who lived in the Last TretaYuga [>5000 years].
Even till the 16th Century majority of the world believed Earth to be the senter of the universe. It is fascinating even if we consider Yoga Vasishta to be only as old as the script it was written in.Â
This world appearence is a confusion, even as the blueness of the Sky is an optical illusion. It is better not to let the mind dwell on the appearance as realty, ignore it (so that truth can manifest in the absence of assumption)Â - Yoga Vaishta: Section 1 (Vairagya Prakaranam): Chapter 3: verse 2
It is clear that they knew Blueness of the sky is an optical illusion, though they talk of it in "as a matter of factly" manner, though they don't  explain the phenomenon further (which wasn't needed during explanation of Advaitic philosophy).
The same idea is mentioned again in the Section 3, Chapter 7 of Yoga Vasishta:
The Lord can be established only if one is firmly established in the unreality of the universe just as one knows that the blueness of the sky is unreal.