0
$\begingroup$

Famous Astrophysicist Dr Neil DeGrasse Tyson, explains that whenever we observe a rainbow it appears exactly semi-circle to us. If another person is observing the same rainbow from a slightly different position, the rainbow still appears 'face-on' semi circle to him/her, not inclined. So he concludes that for every person the rainbow is unique. Why does this happen?

$\endgroup$
5
  • 2
    $\begingroup$ Have you looked at the wikipedia page on rainbows? The fourth paragraph of the explaination section has the answer. If you still find it confusing, the wording of that section might help clarify which aspects are confusing, allowing you to narrow down the question further. $\endgroup$
    – Cort Ammon
    Commented Feb 13 at 3:06
  • $\begingroup$ Did Neil really say that a rainbow is always a semicircle? A rainbow is a circular arc, but how much of the circle you see depends on your altitude & the Sun's elevation. See physics.stackexchange.com/q/72518/123208 & physics.stackexchange.com/q/23647/123208 $\endgroup$
    – PM 2Ring
    Commented Feb 13 at 3:20
  • $\begingroup$ youtu.be/6PrrPOvEU6w?si=wc9iuh3FmhcNwRDu You can check out this video. Quite interesting. $\endgroup$
    – entropy
    Commented Feb 13 at 4:54
  • $\begingroup$ bigthink.com/starts-with-a-bang/rainbow-full-circle $\endgroup$
    – anna v
    Commented Feb 13 at 5:38
  • $\begingroup$ The rainbow is indistinguishable from a 42° circle at infinity. In the language of geometrical optics, it is a virtual image at infinity. However, Degrasse is addressing youtube viewers (link) who are unfamiliar with geometrical optics and infinity. For them, he argues that one might assume the rainbow is an object located in the raindrops, and says, if a rainbow was a real thing, an observer could move to another location and look at it from a different angle, and each observer would see a unique rainbow. $\endgroup$
    – jkien
    Commented Feb 13 at 8:53

0