Daily Junction Play
788watching now
Minute Physics 4 Feb 2026 45 here now

Not a rainbow!

Watch the full video: https://www.youtube.com/watch?v=9udYi7exojk

When Isaac Newton originally observed a rainbow of light split by a prism and made his labeling of the colors as "RedOrangeYellowGree

For You

Because of what you watch

Comments (20)

Daily Junction discussion mixed with clearly attributed comments from the original video provider.

Join in — free. Comments on Daily Junction are for members, so real names stay rare and bots stay out.

One field. We email you a 6-digit code — no password needed. Your comment is kept while you do it.

Under 13? You’ll need a parent’s OK first — it takes them one click.

@
He was quite the believer in occult things
@
Those are indeed the correct colours for the notes!
@
???? Teal sky? Bro has lost it
@
@TAP7a From YouTube ↗ 21 Feb 2026 1
How dare you not finish that scale
@
Chakras | Colors | Sound | Vibration
@
7 notes in a scale. 8 if you count C (or whatever) twice. The octave frequency is double the fundamental tone. The two ends of the octave sound the same but different. On the color wheel purple and violet touch. Human vision runs from 1.65 to 3.26 eV. A close enough for jazz double. We hear 10 octaves and see 1. Maybe his 7 colors weren't so silly.
@
Bro was obsessed with prime numbers
@
@Saleca From YouTube ↗ 21 Feb 2026 1
And the reason you say any number of colours is subjective because there is no fixed amount of colours in the rainbow, its a continuous gradient
@
Im always a sucker for color theory.
@
The green/blue/violet distinction is sooo interesting from a linguistic perspective

In Italian for example we have a common word for light blue, "azzurro" which is used much more frequently compared to "azure" in English, just like pink is for red. Both blu and azzurro are frequently used to refer to the sky (as in the popular songs by Celentano and Rino Gaetano lol). Celeste also literally means "of the sky"

Aqua is called "verde acqua" which makes it seen as a shade of green... and there are many shades of indigo blue that we call "viola". One anecdote I usually mention from my undergraduate optics class is a time we had to calibrate a prism using various low pressure vapour lamps. Many sources classified the 435.8 nm Hg line as "blue" while we were clearly seeing it as violet, so my lab mates weren't sure we were calibrating it correctly hahaha
@
He wanted to have 7 colors to match the 7 notes of the musical scale? Hmmm...did he have any idea about light being a wave and having a frequency and wavelength then? That would allow him to use the same math tools for optics and acoustics.
@
But there IS about as much "indigo" as orange or green in a rainbow. You could think of red, yellow, cyan, and violet as primary colors and the rest as between them.
@
@Systox25 From YouTube ↗ 21 Feb 2026 48
fun fact: we can see true violet because it triggers a bit of the red cones in our eyes. some cameras show violet as blue
@
@JamesR624 From YouTube ↗ 21 Feb 2026 18
What? Who is calling the sky "cyan"?
@
Colour is a continuous spectrum. The choice of how many distinct colours to assign names to is arbitrary, so adding an "extra" colour isn't really a thing.
@
I’m a physicist who has worked with violet lasers, and I just wanted to say this isn’t actually correct. Lasers near 400 nm actually do appear violet to our eyes. Violet is a color in the rainbow not just in the sense that violets are blue, but in the sense that violet is truly a pure spectral color.

You might wonder, how can violet be a pure spectral color given it’s a mix of blue and red? Well, while our eyes’ blue cones are supposed to be the only ones excited by blue light, our red cones are actually slightly excited by wavelengths near 400 nm, which means that we start to see very short wavelengths shades as purple, not just plain blue. Our eyes therefore can’t distinguish between “pure” violet light of the rainbow, and a mixture of red and blue light. But violet itself does appear in the rainbow and is a pure spectral color.
@
@Ze_Austin From YouTube ↗ 21 Feb 2026 27
A less harmful example of fudging the data to match strongly held beliefs at the time
@
@donatj From YouTube ↗ 21 Feb 2026 144
I'd always heard he wanted it to be 7 items due to 7s strong prevalence in the Bible
@
To cite Neill de Grasse Tyson:

"He found the law of gravity, the spectral colors of light and invented calculus on a dare. THEN he turned 25. We should cut him some slack. If he wants a color named indigo he has earned it."
@
@Qberrygames From YouTube ↗ 21 Feb 2026 458
the other reason that he added in the 7th is because at the time 7 was viewed as a holy number from God and he wanted it to incorporate that.