Link: https://bigthink.com/starts-with-a-bang/rainbow-full-circle/

I might be stupid by not knowing this, but I suddenly got an item on my bucket list.

And there's typically three (triple rainbow), you just can't usually see all three.

Triple? What does it mean?!

Water refracts light according to science!

Yeah, it's wild that the bulk result of all the droplets in a system individually refracting the White light is essentially a uniform macroscopic refraction as though it had gone through some kind of super droplet.
Physics does some cool stuff sometimes!

Edit: Refraction not defraction

Sun dog are kind of related aren't they?

This is interesting, but what I want to know is what shape they would be if water droplets were not round.

Like, if they were cuboid or pyramidal instead, would that change the shape of the rainbow?

Theoretically infinite rainbows.

Yes, sundogs occur at a certain point of the arc, and usually closer in to the sun

arent they actually cones? and we just see a segment of that cone which appears as (half of) a ring?

Triple rainbow, oh my gawd!

Look at the moon on a misty night, you'll see the full circle around it. Kinda tricky to have the right Moon and weather at the same time though.

Also: The rainbow you see depends on your position. So a different position yields a different rainbow, even tho it's the same source of light and the same bulk refraction. It isn't like there actually is some kind of physical thing in the sky we see, it's just the light being refracted into our eyes.

Probably not. I would think the more likely outcome is either a very patchy rainbow or none at all. The sphere shape is what is giving you the continuous rainbow, not making it circular. The fact that each color is at a specified angle relative to you / the incidence angle of sunlight does that part.

Great question, I never thought of that.
I tend to think it would be just a blur of different colors mixed together, probably not even visible.

Veritasium did about a year ago using a large glass sphere as a stand in for a raindrop to break down how we're seeing the various light refracted from its interior (or the millions of tiny spheres at one time actually). It's about 30 mins but there's a few points in the video where it hits you what you're seeing, and it's mind blowing. And none of it exists.

The main components of a rainbow are formed by refraction, not diffraction.

That is going to be a halo though - a different (but not unrelated) optical phenomenon!

It would produce a completely different effect. Ice crystals, which tend to be hexagonal prisms, produce some atmospheric optical effects and they can be a variety of shapes.

I have seen full circles and doubles. It's very beautiful. I also like that the background inside of a rainbow is often a different color than the background around it.

A cool thing happened a few weeks ago though. I saw the ends of the rainbow IN FRONT of the trees that were only 100m away. And when we drove past those trees it was in front of the next bunch of trees. Maybe it was just my eyes deceiving me, or maybe a rainbow only exists in the eyes of the beholder. Never saw that before.

I saw a full rainbow from a plane once. It was sick

I saw one in the mountains when ice crystals were floating in the air on a sunny day.

it was actually a septuple rainbow.

Also: there is no pot of gold if there is no end of the rainbow. Let this sink in for a moment.

Across the sky?

I really hope you're kidding

@PattyMcB @illi Here? With the caliber of people I know? Almost certainly a joke.We eat ignoramuses for lunch on the fediverse.

Yep. The one you see is actually just a 2d slice of a complex overlapping structure of light within a cylinder. It's really fascinating.

It's a reference

Original video

Aren't there actually 5, with the other two being on the opposite side of the viewer from the main 3?

What I believe that means is that the mist that formed the rainbow was between you and the trees in question.

I don't think there is a limit, it's just that each one is significantly less visible. It's all to do with the number of bounces within the rain drop.

IIRC rings 1 and 4 are towards the sun.

In cold climates you can also get sun halos where the position depends on the shape of the ice crystals in the air.

Ice crystals are not round and they create different patterns depending on the shape they take. Look up sun halos. There is even a specific one called a sun dog.

Let me share that famous MIT lecture on rainbows again: https://youtu.be/iKUSWJWMSk4

Oops, you're right, got my words mixed up haha

This is one of those weird things where our perception is dictated by our cultural biases.

If you were an intelligent alien coming to earth for the first time from a planet with no rainbows, you'd see one and think "Oh, what an interesting phenomenon! A circular refraction partially obscured by the ground!" - because of course there's no way that kind of optical phenomenon could be anything other than completely symmetrical. It's obvious if you think about it.

But as a human, right from being a child every single portrayal of a rainbow has them as an arc, and we were never given reason to think about it from an analytical perspective. So we never did.

Only because there's no end to it. Leprechauns didn't want you to know that.

So where's the gold then?

My first encounter with this concept was playing Katamari Damacy. Once you've gotten big enough to roll up the rainbow, you get to see it's a full circle ⭕ 🌈

You can see this for yourself if you have one of those hoses with the multiple nozzle settings. I forget which setting I had it on, but I blew my own mind seeing a rainbow ring messing around with one as a kid.

The same story as with climbing the corporate ladder, which is a hamster wheel.

(No gold, too bad)

16 years ago. No wonder i didn't get it!

This comment hurt a little :D

It's related to the number of total internal reflections inside a raindrop. The 2nd rainbow is actually inverted, colour wise. The 3rd inverts again, and so is normal. Each reflection loses more light however, so it gets dimmer. 3 is the practical limit in the sky, with our eyes. In the lab version, at least 18 rainbows can be detected, even by undergraduate level students!

Not infinite. Eventually they begin to overlap and are no longer distinct rainbows.

Sorry. If it helps, I was around 3,000 years ago... when we still used dial-up to access bbs's

Ok this is crazy. I have a picture I took a few years ago of a double rainbow. Never noticed it was inverted, but I went to look and sure enough it is. Now I’m wondering how I didn’t notice before.

This type of misinformation is exactly what I would expect from the leprechaun. "It's a circle, no need to search for the gold, move along". Nice try, I'm not buying it!