IRA FLATOW: Have you ever left a movie theater wondering about that one detail that just didn’t make sense? Like, how did the main character hold their breath underwater so long? Or this one I really like. Why are galactic stormtroopers such bad shots? Well, Science Friday’s digital producer Emma Gometz is investigating the kernel of science behind some of those made from movie moments. Hi, Emma. What movie is on your mind this time?

EMMA GOMETZ: Hi, Ira. It’s called 65. Have you heard of it?

IRA FLATOW: I have to say that I have not.

EMMA GOMETZ: That is fair. It came out pretty quietly in early 2023, but I am an Adam driver super fan so I did see it. But here’s a comparison. Have you seen the movie Alien?

IRA FLATOW: Oh, I loved Alien, especially the part about the alien jumping out at you and scaring you half to death.

EMMA GOMETZ: Yeah, me too. I love that part. Well, 65 is kind of like a reversal of Alien to me. Instead of humans coming to an alien world and getting attacked by aliens, in 65, aliens that existed 65 million years ago crash land on a prehistoric Earth and get attacked by dinosaurs. Oh, and the alien is Adam Driver.

IRA FLATOW: Adam Driver, that really sounds like fun.

EMMA GOMETZ: It is. Yeah, I definitely spent a lot of this movie laughing. But after I was done, I came across a study about how a planet that resembles Earth during the Jurassic era would have signs of life that are easier to notice from space than modern Earth. And instantly, I was like, so why was Earth this unknown planet in this movie? And why weren’t the aliens who visited more prepared for what they would find there? So we found a real scientist who models exoplanets to talk about this premise.

IRA FLATOW: Yeah. You spoke to one of the scientists behind that study, Dr. Lisa Kaltenegger, the director of the Carl Sagan Institute and professor in astronomy at Cornell University in Ithaca, New York. So take it away.

EMMA GOMETZ: Hi, Dr. Kaltenegger. Welcome to Science Friday.

LISA KALTENEGGER: Thanks so much for having me.

EMMA GOMETZ: So tell me, why would Earth during the Jurassic era be easier to spot from space than Earth today?

LISA KALTENEGGER: Actually, the signs of life would be easier to spot because there’d be more oxygen that allowed for these huge dinosaurs to roam our beautiful planet. And so signs of life would be just a tiny bit easier to spot.

EMMA GOMETZ: And when you say “signs of life,” what do you mean?

LISA KALTENEGGER: I mean life changes the atmosphere of a planet. The oxygen we breathe is made by life. And there was a time, about 300 million years ago, just when the dinosaurs started out, when oxygen was in higher concentration.

EMMA GOMETZ: That’s interesting. So I read the paper that you wrote that kind of revealed this information to us. And to do that research, you refer to something called transmission spectra, which I’ve seen written as light fingerprint before. Could you tell me what exactly are transmission spectra, and what do they tell us?

LISA KALTENEGGER: So if, by chance, we look at another star, another sun, just the right way, then when the planet goes between us and its sun, part of the light that the star sends out gets filtered through the air of that alien world before it hits my telescope. And light and matter interact. That means if you have a molecule– if you remember from school, water is H2O, so 2H, 1O. You can hit it with just the right energy to make it swing and rotate.

And if that happens, the light actually doesn’t pass through the atmosphere to my telescope, but it actually makes the molecule swing and rotate. So by what’s missing in the light that gets to my telescope, it’s kind of like a passport stamp. It tells me what molecules light met on its way to me. And thus, I can decipher the air or what’s in the air on an alien world without getting there.

EMMA GOMETZ: And what would need to be in the air of an exoplanet in an alien world in order for us to say that might be habitable?

LISA KALTENEGGER: So the combination of oxygen with methane, methane is a reducing gas that reacts with oxygen. So oxygen and methane make CO2 and water. If you have oxygen and methane together in a nice warm world just the right distance, not too hot, not too cold from its sun, then we have no other explanation. Then we need life for this amount of oxygen and methane to coexist. So that’s, in a way, our golden fingerprint that we’re looking for to decipher where life could be hiding on other worlds.

EMMA GOMETZ: Right. So what you and the co-author of this paper found then was that 300 million years ago there was this really high concentration of oxygen. And that would be a stronger signal then for, let’s say an alien, to see at that time?

LISA KALTENEGGER: Absolutely. And that’s kind of the fun part because we think oh, we’ve evolved. And so you might be able to look for technology. You’re going to find humans. But if you take the Earth and its history, you find out there were some times in our history, and it happens to coincide with when the big organisms, like dinosaurs, roamed the Earth, where there was more of oxygen on the Earth and also a bit more of methane. And so if these are the two gases we’re looking for, it seems that a Jurassic world would be actually easier to spot for an alien observer.

EMMA GOMETZ: Based on everything we’ve talked about, what do you think the main character in 65, who is this advanced extraterrestrial, should have known about Earth before he landed on it?

LISA KALTENEGGER: Well, it kind of seemed that there was an unexplored planet, so he didn’t have much information before he crash landed. But by just the amount of oxygen that he could find– if he had just a very first glimpse of the atmospheric composition, it tells you that the amount of oxygen gives a lot of energy, thus there will be huge creatures. Whether it’s dinosaurs or something else, it’s just watch out. Make yourself small, hide, would probably be my best guess.

And then they never really say where these advanced aliens come from. So did he need more oxygen too? Or he should have been like super, super hyped because with more oxygen it’s just going to be more energy available for you and me too. So we could maybe run a bit faster. Not that we could outrun a dinosaur, I don’t think. But maybe it’s going to be just a little easier to jog around.

EMMA GOMETZ: That’s so interesting. Well, thank you.

LISA KALTENEGGER: Thanks. And I’m looking forward to the next sci-fi you’re going to talk about.

EMMA GOMETZ: If you also wonder how science and movies could play out in real life, check out our Science Goes to the Movies newsletter. Every few weeks you’ll get a story in your inbox about the unexpected science that you can find in movies, whether they’re out in theaters or streaming at home. Just visit sciencefriday.com/movies. I’m Emma Gometz.

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