If you get caught between the moon and New York City, the best that you can do is call Neil DeGrasse Tyson, the director of the American Museum of Natural History’s Hayden Planetarium.
A rare “blue moon” will hover over the city Friday night, meaning it’s the second full moon in a month (there was another on Aug. 1). The last blue moon happened back in 2009, and if you miss tonight’s, you won’t have another chance until 2015.
Dr. Tyson is equal parts cosmic party promoter (he coined “Manhattanhenge”) and party pooper (he lead the charge to demote Pluto off its planetary status). So the Wall Street Journal asked him to sort out tonight’s blue moon fuss for us.
WSJ: Wasn’t there just a supermoon? How many special moons are there this year?
Tyson: All of the full moons for the entire year are special in that they have particular names. The most famous is the harvest moon; it helps to have a popular song. And, in June, the moon lies low and takes on an amber hue because of atmospheric dust, so it’s called the honey moon.
WSJ: But blue moons are extra-special, no? Once in a blue moon. All that.
Tyson: A blue moon is just a second full moon. The average time the moon takes to complete a cycle of phases is 29.5 days. Every month except February can have a second full moon. Chances of a full moon on the first of the month, like we had this month, is about 1 in 30. So blue moons happens about once every 30 months. About 2 1/2 to 3 years. Not really that rare, my friend.
WSJ: A little more rare than congressional elections, a little less rare than Summer Olympics.
Tyson: If that’s how you measure time.
WSJ: So you’re not going to be doing anything special for it?
Tyson: For what? It’s just a full moon. It’s not an eclipse or anything like that. It’s just another Friday night.
WSJ: But that’s the spoilsport in you. You get excited about Manhattanhenge, and that’s twice a year.
Tyson: That’s because Manhattanhenge is a visual spectacle. People come here just to see it, to experience it. A blue moon is just like any other moon. You know it’s not going to actually look blue, right?
WSJ: I know. But so why all the fuss?
Tyson: There’s something about witnessing something in the sky that makes people think they’re seeing something unique or special. I don’t really understand the psychology of it, to be honest.
WSJ: Are New Yorkers more prone to that?
Tyson: In any city with lots of skyscrapers, lots of skyline, the moon seems bigger than it is. It’s called the moon illusion.
WSJ: Because of framing?
Tyson: That’s a good way to put it. We see that it’s bigger when we compare it to towers and bridges and trees and mountains. The moon looks much smaller if you’re on the ocean and have nothing to judge its size against.
WSJ: So blue moons are nothing special? And they’re not even that rare?
Tyson: Let me tell you something about full moons: kids don’t care about full moons. They’ll play in a full moon, no worries at all. They only get scared of magic or werewolves from stupid adults and their stupid adult stories. Scientifically illiterate adults are the problem. And the weather in New Jersey, y’know, if it’s overcast or something.