Parts of Arizona are havens for stargazers, with their dark skies and lack of light pollution. But, are those dark skies really devoid of color?
Rebecca Boyle, science journalist at Atlas Obscura and author, argues they're, in fact, not. Boyle wrote "What Color Is Night," and joined The Show to talk about what got her thinking about what color the night sky is.
Conversation highlights
What got you thinking about what color the night sky is?
REBECCA BOYLE: Honestly, it was in part because I was planning a trip to Alaska. And I was hoping to see the northern lights. And I did, I got lucky ... the sun's been very active lately. So, it's been a good show actually in a lot of the U.S., not just in the northern latitudes. But I was wondering if I'd be able to see it. And in part because, you know, Alaska in the summer is very, there's the midnight sun, you know, depending on how far north you are, it's not that dark.
And, there's this actually good chart you can look at on timeanddate.com has a nice little like darkness chart and there's a few other kind of scales that I look at as a stargazer to look at: Were is there a good dark sky that doesn't have light pollution?
But also the sun itself in the northern latitudes in the summer can kind of get in the way, and you don't really have darkness overnight. You have what they call civil twilight or astronomical twilight, which are these kind of like grades of darkness.
It just made me kind of think about, like, what does that actually mean? And like, it's not absent of color ever, really. And even when you're looking for a really dark sky, you know, you think of it as this blackness, but it's not. It's more complicated than that.
It seems so counterintuitive. Of course, if you go outside in the middle of the night, the sky is black. There's no light. But that's not true.
BOYLE: Yeah, it's not true for how we experience it. It's not true just optically. It's not true for how animals experience it. And that's something I didn't even get into in this piece for Atlas Obscura is that, you know, the experience that other creatures have of nighttime is very different from ours. And we wouldn't even think of it as that dark if you had the, the sensory capabilities of some nocturnal animals. But, yeah, it's kind of counterintuitive. But if you go outside at night and look, you'll be like, "Oh, yeah ... it's not just blackness, it's not just this emptiness." There's a lot of color. There's a lot of vivid characters in the night sky and in the landscape around you. Uou know, almost anywhere you are in the U.S., it's not totally dark. And so there's always going to be some leakage of light from somewhere.
Are there ways that we can actually see that? I think for a lot of people who go outside and look up at night, they're not going to see those colors. So, is there a way that we can help ourselves to do that?
BOYLE: I think one of the most important things to do when you're outside at night is to just give yourself time. This is not something people think about, necessarily, if you're an amateur kind of stargazer, "I want to go outside and look at some stars. Like, take a peek." You need to be out there for like 30 minutes at least. ... Your eyes have to really adjust, you know. The rods and the cones have to really be able to receive this as, you know, many photons as they can, as your pupils dilate as widely as they can get. It takes a lot longer than you might think. Like 30 minutes is kind of a minimum for good seeing, is the term astronomers use to talk about what the sky looks like at night. You wanna give yourself time. And the longer you're out there, the more you can adjust, the more features, the more color you might actually see in the night sky.
Is it easier to do that in a place where there is less light?
BOYLE: Yeah, I mean, the darker you are the drier you are. I mean, the Phoenix area is a great place to be for a really dark and — well, depending on where you are in Phoenix, I guess it can be pretty bright in the city. But, you know, in the Sonoran desert and the deserts around Phoenix, it's really, really dark in certain areas. We can get away from city lights. The atmosphere is so dry that light domes are not quite as bad as they are in the Midwest and other places in the U.S., because there's just so little humidity in the desert to carry molecules of air that would bounce light around. So you're going to get darker in Phoenix, outside of Phoenix, you know, north towards Tucson than you would somewhere like Chicago. You know, it takes a lot longer to get somewhere dark if you're in the Midwest.
But yeah, the darker you can get the better you'll see the detail in the night sky ... Color itself kind of depends on the light around you. What time of night it is. How far after sunset you're outside. Whether there are clouds overhead, that can kind of reflect light back to the ground from the, you know, cities or from the sun itself, depending on what time of night it is.
There's some like ancillary reflection that could happen after sunset. But then also just look at the stars themselves, and you'll notice how much color there is in the stars. I mean, stars are not just like flecks of light — they're blue, they're red, sometimes they're yellow. Sepending on the type of star, their distance from us. All these different features kind of make them appear differently.
