21 10 meters SARA SEAGER Physics and planetary science, Massachusetts Institute of Technology, Cambridge We picnicked inside a fiberglass radome (a portmanteau of radar and dome), atop the tallest building in Cambridge. The Green Building, otherwise known as Building 54, houses the fields of Geology and Earth Sciences on the lower floors and Astronomy and Atmospheric Sciences on the upper floors. It was only late October, but the temperature was already below freezing, so we bundled up in fur caps and heavy jackets to endure the cold inside the dome. We sat next to a defunct radar satellite that had recently been hacked by students to bounce beams off the moon. 1 Sara requested high-protein brain food, so we made hard-boiled eggs and prepared them so that each egg was boiled for a different increment of time, which was an- notated on each of the dozen eggshells: 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, MICHAEL: Do you know the early astronauts like Buzz 15 min, 16 min what your kids are going to Aldrin. Buzz Aldrin can be dress up as for Halloween? alternately outspoken, rude, Sara ate a twelve-minute egg to test her theory that there is a threshold beyond obnoxious, and fun, while the which there is no effect on the egg, so boiling longer only serves to waste energy. SARA: Yes, one son is going to be current astronauts typically Buzz Aldrin, an astronaut, and appear to be more conforming (FIG. 1) the other son will be a pirate. and obedient. A pirate is kind of like the early astronauts: a AMY: Similar. radical who challenges authority. SARA: Actually they are quite AMY: Is Buzz still alive? opposite in personality. SARA: Yes. For MIT’s 150th AMY: They are both going on anniversary in 2011, there journeys. were a number of celebratory symposia. One of the symposia SARA: Yes, agreed. Astronauts was “Earth, Air, Ocean and Space: are adventurous, most especially The Future of Exploration” 104 3 signs of life by way of unusual off of the picture. In fact I could MICHAEL: What is beautiful is that amounts of “biosignature” gases even argue that when we want to we will be able to observe it if we in exoplanet atmospheres. think about the probability of life as a society keep aging. Eventually in the Universe we first think the light would reach us. (FIG. 2) Sara showing us our of the scale of 1021, the scale of place in the universe, a rendering our galaxy and even 1026, the SARA: If we lived for billions of what we believe our galaxy, scale of the visible universe. and billions of years we could the Milky Way, looks like. “This is One more thing I want to add is see a little further out. showing us approximately where that because we are looking for our sun is, and trying to illustrate signs of life by way of exoplanet AMY: So is that the goal of how far away we can find other atmospheric gases, we are trying astronomy, to see out that planets, around other stars. At the to understand the gas outputs far, but knowing you can’t? end of this little column, that’s how of microbial life on earth, trying far away the Kepler stars are, but to understand processes at a SARA: Astronomers have many even those stars we consider too far much smaller scale than planetary different goals and most of our to see. So despite the fact that we or planet orbit size, on the scale goals center around the concept have a hundred billion stars in our of 10-5. of understanding where we galaxy, and there are upwards of came from. One of our goals is 2 hundreds of billions of galaxies, we AMY: This movie was made in to know how the universe was can only really find planets close 1968, and it claimed that we born and evolved. And, we don’t to our home, right near our sun.” were looking at the edges of necessarily need to see the whole our understanding at that time. universe to move our understand- AMY: So we’ve been using How have the edges of under- ing forward. For example, right and included a panel of ten to the differing scales in Powers standing in your field changed now, outside of my window we twelve astronauts all together. of Ten to frame our conversa- from that period to now? can see the city of Boston on a Buzz certainly stole the show. tions with people; where macroscopic scale (FIG. 3). And would you place your research SARA: Well the movie went to we know that there are other AMY: Now that you’re on that continuum? 1024, and in astronomy, we’d like cities out there. We just can’t see warmed up, can you tell to go a lot further. We have the them from here but we could us about your research? SARA: Most of my research is capability for observing very, extrapolate or try to use other placed in the planetary scale, very far away. The size of the information about cities. With SARA: My research is on which is 107. Our earth has a ra- observable universe is roughly astronomy, it’s a similar concept. exoplanets – planets that orbit dius of about 6,400 kilometers, so 47 billion light years or 4.4 times We still have information about stars other than our sun. We its diameter is about 107 meters. 1026 meters. We can’t see further most of the components of the know of hundreds of exoplanets What I love about exoplanets away than this because light more universe, even if we cannot see all right now and there are likely is that the research operates on than 4.4 x 1026 meters away has of the very distant components. far more than trillions of planets other scales. For instance, 1012 not had time to reach us over out there in the universe. We encompasses the orbits of the the age of the universe. So the Returning to the changes since are trying to understand what Solar System’s four inner planets. next power of ten, 1027, is not the film was made, in the 1960s exoplanets are made of, how to Or 1013, which encompasses the observable. So, sorry you won’t exoplanets were simply specula- detect them, and how to find solar system with Pluto partially be able to do 1027. tion; people hadn’t even found 105 them yet. There were a few leads planets are twice the size of Earth planet in the so-called habitable idea, and it will be accepted. But which turned out not to be real and must have large quantities zone of its host star, with a there is a line drawn, and aliens planets, so people imagined that of gas in their atmospheres, habitable moon in orbit about definitely fall on the wrong side all planetary systems were just making them more equivalent to the planet. Right now, we know of that line. Instead we are doing like our own. At the scale of a mini-Neptune than to an Earth. there are no big planets in the the real search for planets that 1013, we see an image of our solar I can give you dozens of examples Alpha Centauri sun-like star could have life; it’s our goal to system where the planets are well of anomalous exoplanets. So systems; such planets have been find so-called “habitable worlds,” sorted with the four small inner the sheer number of surprises is ruled out by observations. and when we find potentially planets and the four outer giant changing our philosophy about habitable planets, we’re going to planets. Theories were built, then, what other planets could be MICHAEL: I’m imagining that look for signs of life on them. about planet formation based on like. This changed paradigm of Avatar must have had some There is no question that others the single example of our own the range of exoplanet types team of scientists that helped will follow and try to send or solar system. But today with is the biggest factor that has them. Have you ever been listen for radio signals. And, hundreds of known exoplanets changed since the 1960s. consulted by Hollywood? there’s also no question in my – many, many known planetary mind that in the distant future systems – we have a completely AMY: And how does that knowl- SARA: Absolutely. I really like people will try to go there, either different picture. And so now edge that there’s more out there Hollywood. At the end of the day with a robotic probe, which might we believe that for exoplanets affect culture on a larger level? Hollywood doesn’t usually take take tens to hundreds of years, anything is possible within the my advice, but I have been a ves- or alternatively to find a way for laws of physics and chemistry. SARA: What’s fascinating about sel for brainstorming in a unique humans to travel there alone. The Any kind of planet you could exoplanets is that in some ways way. The public has a huge public loves the concept of aliens, imagine is out there somewhere. popular culture is ahead of us appetite for black hole physics, and the public are our taxpayers scientists because of science time travel, outer space, relativity, who ultimately fund our space MICHAEL: What is an fiction, things like Star Trek.