Short Wave - Micro Wave: "Once In A Blue Moon" Is Happening Again This Halloween

Episode Date: October 30, 2020

This year, there will be a "blue moon" for Halloween. So for today's show, we're asking: What IS a blue moon? Is the moon ever blue? And are they as rare as the phrase "once in a blue moon" implies?For additional info and fun links, check out the episode page.Follow Maddie and Rebecca on Twitter for more science nuggets. Maddie's @maddie_sofia and Rebecca's @rebeccalramirez. Email the show your celestial musings and inquiries. We're at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Maddie Safai here with one of our producers, Rebecca Ramirez. What's up, Ramirez? You know, just contemplating the moon. Is this because you read that Twilight book as an adult, Rebecca? Listen, no pleasure should be a guilty pleasure. There should be no shaming of pleasures. All right, that's true. That's true.

So why are we talking moons? Well, I mean, there's a blue moon happening this weekend. Oh, yeah, yeah, yeah. Just in time for Halloween. Exactly. And so I thought, what better way to get into the Halloween spirit than to ask questions about the celestial body responsible for werewolves and creepy shadows? Maybe vampires. I don't know about that one.

Do they have a tie to the moon? Who can say? But they're Halloween. So today on the show, we're asking, what is a blue moon? Is the moon ever blue? And are they even as rare as the phrase once in a blue moon implies? I'm Rebecca Ramirez. And I'm Maddie Safaya.

This is Shortwave from NPR. All right, Beck. So today you're going to explain what's the deal with the phrase blue moon. Right. And so for more on this, I called up Corinne Rojas. These days, she's an operations engineer for the Mars Perseverance Rover, but... I've always loved staring at the moon. I call it my first love.

Oh, my God, I love that. I know, right? And actually, when she picked up our Zoom call, her virtual background was her favorite crater on the moon, too, Giordana Bruno. And so, Karin spent a lot of time studying the moon. Her previous job was as a researcher for the lunar reconnaissance orbiter, which, fun fact, is the only active NASA science mission to the moon. Oh, very cool. Yeah. All right. Anyway, a bloom is just a specific kind of full moon, so let's just start by explaining why you can see the moon at all. What you're actually seeing is. isn't light from the moon. It's sunlight coming from the sun reflected on the moon and then shining back onto Earth. So one side of the moon is always fully lit by the sun. But what dictates how much of the moon you can see is how much of the lit up side is facing us,

which changes as the moon orbits. Right. So during a full moon, the side that's facing us is fully lit. And that happens about every 29 and a half days as part of what's known as the sonotic period or how long it takes for an object in our solar system like the moon to return to approximately the same position relative to the sun and the person looking at it from Earth. Okay. And within the sonotic period, there's a lunar cycle. Yeah, and I know there's some like waxing and waning involved in the lunar cycle. So let's talk about that. Yeah. So technically when

people talk about the lunar cycle, they start with the new moon, not the full moon. And the new moon's basically the opposite and that it seems like the moon has disappeared from the sky. Right, because the moon at that point is kind of between the sun and the earth. So standing on earth, the light is kind of hitting the back of the moon, if you will, the lit-up side you can't see. Right. The moon is still there. It's just not illuminated by the sun. Yeah, and so then it starts waxing, more and more of the side of the moon facing us is lit from the sun. Which means that the full moon is building up. First is a little crescent, then first quarter, then waxing gibbis. Waxing gibbis. Okay, it's a technical term, okay?

And then eventually it reaches full moon status. Then it starts waning, meaning you see less and less of the moon until there's a new moon again, and you can't see any of the lit up part. Rinse, repeat, 29 and a half days later, roughly. All right. Well, we did it. Okay, so finally, we get to the question, when is a full moon a blue moon? Yeah. Okay. So here's where we turn into a mini history podcast. Corinne told me that actually blue moon has had many meanings over the years. It used to be that a blue moon referred to the third full moon in a season that has four full moons. That's what's known as a seasonal blue moon. But I'm guessing that's no longer what it means. Right. So in the mid-20th century, the meaning was actually misinterpreted and changed. And nowadays,

when people say a moon's a blue moon, what they're usually referring to is the second full moon that happens in one calendar month. So you've got a lunar cycle that lasts about 29 and a half days. Okay. And so in months where you get the full moon at the very beginning, like how we had one on October 1st, there's time for another one at the end, like tomorrow on Halloween. Right, which usually happens around every 2.7 years. Which, yeah, that's not nothing, but it's not actually that rare then, like a blue moon? Yes. So, I mean, blue moons in general aren't that rare. But this particular blue moon, a Halloween blue moon for everyone in the U.S., hasn't actually

happened since 1944. That's World War II. Okay. So we actually have a rare Halloween blue moon 2020 situation. A little situation. Okay. So generally speaking. Once in a blue moon, terrible saying, it's not actually that rare. Is it even blue, Rebecca, like, or is this whole thing a lie? What do you think? You're about to crush my dreams right now?

100%. But for the sake of our friendship, I'll let Corinne do it. The moon's color does not physically change. The moon will remain its beautiful, gorgeous color that we know and love. But hang on. But sometimes the color can appear to change. And that is usually related to volcanoes, dust storms, wildfires. You know, stuff here on Earth.

Because basically, there has to be enough ash of a particular size kicked up into the Earth's atmosphere to scatter all of the smaller red light particles, making it look bluish. But so generally speaking, it's that, like, gray and white, beautiful moon body we know and love. Yeah, exactly. Pretty rare for it to actually look blue. So you got it. Blue moons. All right.

So you're telling me blue moons, not that rare and not actually blue. Yeah. It's not great on the blue moon front for factiness, I got to say. Well, what is shortwave for other than destroying your dreams with facts? Am I right? You know what I'm saying, remember? 100%. All right.

So we normally turn to listener mail here, but we are switching it up today to send off our producer Brent Bachman instead. He has been with us since day one. and it is technically, allegedly, his last day on the show. And so I thought it would be really cute if we could just all say something we really love about Brent Bachman and show how much we really appreciate him. So, okay, I'll start, no pressure. My favorite thing about Young Beebe is that he is so nonchalant in his excellence and his playfulness that he'll even let me nickname him Young Beebe, which is ridiculous.

So, you know, all right, your turn. Okay, okay. I would say that Brent taught me to lean into being weird instead of hiding it, which I appreciate, how to trust myself and my instincts. Unless we disagree, and then he taught me to trust Brent's instincts, if you know what I mean. You know what I'm saying? Only way to go. It's the right thing to go. It's the right thing to do for sure.

Yeah. Okay. All right. We're not the only ones who want to say goodbye to Beebe. Hey, this is Emily Kwong. Brent, you taught me the power of a good prop. You know, like that slime in our ASMR episode, using objects to tell stories on the radio,

and how to just roll with the punches. I aspire to be even a little bit as calm and kind as you are under pressure. He is calm under pressure for sure. This is Britt, another producer on the show. The thing about Brent is that he's a total boss, but he would never let you know that. He's so incredibly generous with his time and his skills. We were the luckiest to get to work with him.

This is Viet Brent. You're incredibly talented. I hope we get to work together again at some point. And even though you're leaving us, your producer DNA will always be a part of the show. We've benefited from it, and our listeners have too. Thanks a ton. All right, that is it from us.

Brent Bachman, we appreciate you. We're going to miss you so much, buddy. So much. But we know where you live. Yep. And your windows are on the first floor. You know what I'm saying? So today's episode was produced by Thomas Liu. It was edited by Viet Le, Ariel Elizabeth. Fact-checked it. And we had engineering by Patrick Boyd. Happy Halloween from all of us at Shortwave from NPR. In your capacity, as a NASA employee, serious, serious question. Is there? For the record, a man on the moon. I am not authorized to disclose such information at this time, unfortunately.