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Searching for Life Beyond Earth, Finding Our Dreams Instead

How would you recognize another Earth while you’re on this one?


 That’s a question astronomers often try to answer. Oh, the scientists say, they could look at orbital models, temperature models, atmospheric models, formation models. All kinds of models. “None of these models include anything like pollution or warfare or any of the things that make Earth a human world,” says Lisa Messeri, an anthropologist of science and technology. There was a striving quality to their answers.


 “We don’t want to find a world with warfare or stricken with poverty,” Messeri says. We want a perfect world, she continues, “a world that is untouched by human activity.”

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 Messeri herself doesn’t study these great-beyond planets: She studies the people who study them. And in their presentations, papers, and talk amongst themselves Messeri notices a few things: that the astronomers have turned these light-years-away planets into real places—not just plots and pixels—defined in comparison and contrast to this
 
 terra firma
 
 . Most importantly, though, Messeri sees evidence that while exoplanet science is a field of the present and future, it also reaches, fundamentally, toward the past.


 The astronomers Messeri studies often spend their lives searching for so-called Earth-like planets. These worlds could potentially have life. They could have liquid water or continents or oxygenated air. They’re the right sizes at the right distances from their suns, and could have the right atmospheres and oceans. We sometimes call this search one for “Earth’s twin.”


 But that’s not quite right, Messeri says: It’s actually the search for Earth’s perfect twin. Earth as it used to be, before humans got to it. A whole-world Eden.

<h2>
 Yearning for Home
</h2>

 After attending a meeting of Kepler space telescope scientists, Messeri read more about the philosophical concept of home, she says, “and what a home is and this idea of ‘Can you ever go back to your home?’ ” She had first picked up this thread in graduate school, and now she returned to work from mid-20 th -century philosophers, who’d grown up before World War II and had to continue living after it. They missed their prelapsarian place.


 And, Messeri realized, exoplanet astronomers felt that same feeling—for a place that they’d never known: an Earth without them.


 There’s a word that conveys that feeling, actually, in Welsh:
 
 hiraeth
 
 , longing for a home you’ve never had or can’t return to.

<h2>
 Finding Herself
</h2>

 “Anthropologist” wasn’t a thing Messeri initially intended to become. At MIT as an undergrad, she was poised to enter the workforce as an aerospace engineer. She loved space: the existence of it, the bigness of it, the big questions it forced you to try to answer whether you wanted to or not. “But by the time I got to my senior year, I began to realize that the actual day-to-day work of an engineer wasn’t something I was particularly enamored of,” Messeri says. Expanding her interests, she took an elective course about the history of science. The idea that science had a history—that it came from somewhere and had not always been thus—had never exactly occurred to her.

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/lisa-messeri-large.width-990_KKLsWnH.jpg"/>
<figcaption>Lisa Messeri says our search for habitable exoplanets reveals our yearning for a perfect world.
 
 </figcaption>
</figure>

 But she liked the idea so much that she went on to get a doctorate in the history and anthropology of science and technology. When it came time to pick a dissertation project, she went back to what had first caught her scientific interest: all that stuff beyond our atmosphere, all the people who tried to figure it out. Messeri’s roommate was a planetary scientist and offered to introduce her to some people in her department—people who included Sara Seager, who, back in 2008, wasn’t yet the rock star she is now and hadn’t yet been profiled by CNN or the
 
 New York Times
 
 . So Messeri began to (with permission) follow these exoplanetary scientists around—watching them code, watching them use telescopes, watching them make sense of the dots and lines decorating x-y axes.

<h2>
 Finding Places We’ve Never Been
</h2>

 Messeri’s scrutiny of these scientists came to focus on placemaking. It’s not a gerund we think about often: transforming a position in x-y-z-t space into something with more sentiment happens seemingly automatically in our minds.


 But while it’s normal for humans to do that, it still takes mental work. “Places don’t just exist,” Messeri says. “We have to make them.” Each place is tinted by our particular history, our sensory interpretations, our social contexts. In just about every case, we placemake in places where we’ve visited or lived or of which we’ve seen copious Street Views. “But can there be places,” Messeri wondered, “that are not on Earth, where humans haven’t been?”


 It seemed to her that the exoplanet astronomers thought so. They had transformed their planets into places, seeing each of them as a small step on the way toward the real goal: that perfect place, the never-inhabited-by-humans habitable home.

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<h2>
 Seeking a Perfect Species
</h2>

 But those homes may not be uninhabited—they potentially may be someone else’s planet. That thought frames the work of SETI scientists, another group of researchers who are looking not just for habitable worlds or for the chemical signatures of biology, but for smart, technologically capable inhabitants. In their quest for advanced civilizations, these SETI—search for extraterrestrial intelligence—scientists bring their own idealizations to their quest. They are usually scouring the universe for a type of species we hope to become: nonviolent and stable, the kind that sticks around long enough to broadcast signals that lesser beings like us might pick up.


 Their field began around 1960 and solidified around a conference at the National Radio Astronomy Observatory in Green Bank, West Virginia. There, a young astronomer named Frank Drake came up with “the Drake Equation,” which gives researchers a framework for talking about how many intelligent civilizations might inhabit the Milky Way galaxy. Drake’s formula steps through the conditions required for life to arise and gain intelligence: First comes the rate at which suitable stars form (
 
 R
 
 ), followed by the fraction of those suitable stars that have planets (
 
 f*p
 
 ). Then, one must consider the number of planets around those stars that are “habitable” (
 
 n*e
 
 ), the fraction of those habitable planets on which life arises (
 
 f*l
 
 ), the fraction of those life-having planets on which the life becomes intelligent (
 
 f*i
 
 ), and the fraction of those intelligent civilizations that use technology to send signals to space (
 
 f*c
 
 ).


 Some of those variables are straight physics: questions that have easy answers, albeit ones we don’t fully understand yet. The evolution of actual life and serious smarts and the development of detectable technology are less quantified and perhaps less quantifiable.

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/eso1629a.width-990_lEY6D3J.jpg"/>
<figcaption>Proxima b orbits in the habitable zone of its star, Proxima Centauri.
 
 </figcaption>
</figure>

 But there’s one more variable in the equation—and it could be the biggest question-mark factor determining whether we can find alien life. Scientists call it
 
 L
 
 : the length of time that intelligent civilizations keep broadcasting.


 What
 
 L
 
 actually connotes is “the amount of time a technological society usually stays around before it destroys itself or significantly regresses.” If
 
 L
 
 is small, it could mean humans are the only ones in reasonable shouting distance. If it’s large, there could be many more intelligent others out there.


 Humans are the only example of intelligent life that we have. So
 
 L
 
 , based on our personal stats (and because we could blow ourselves up tomorrow and stop broadcasting signals into space), is on the order of 100 years—the approximate amount of time we’ve been producing radio transmissions. Of course, we could stick around and stay smart for a lot longer and prove that conservative estimate of our own
 
 L
 
 wrong.


 But if SETI finds anything (or anyone), those aliens likely will have been around for a long time (the chances that we’d find aliens that had popped up just 50 years ago is smaller than minuscule). That means any intelligent alien civilization alien civilization would probably have an
 
 L
 
 much longer than 100 years. And that would, SETI scientists have long said, give humans hope: In addition to knowing we’re not alone, we’d also suspect that however we’ve changed our planet, whatever marks we’ve left on it and each other, we could figure out how to continue existing. Those aliens figured out how, after all—and they’re aliens!

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 Finding extraterrestrial intelligence would show us an ideal version of our future selves.

</div>

 As researcher David Duner, a professor of the history of science and ideas at Lund University, put it in a recent paper, such a civilization must have encountered difficulties like the ones that face us today. “Wars, climate change, pollution, decreasing biodiversity, and so on,” he wrote. “The mere fact that they have survived would indicate that they have a functioning social structure that can handle and avoid crises (or at least that they are able to recover from them), and that they have a complex social system that regulates risks and destructive behavior.” Finding extraterrestrial intelligence, in other words, would show us an ideal version of our future selves—a more cohesive society, one that’s better at stewarding its planet and less murderous of each other.


 To search for such a civilization indicates a hope that those versions of intelligence are out there, stably surfing through the universe. These beings may not have kept their Earth-twin planet pristine. Neither would it be that Ur-Earth for which astronomers feel
 
 hiraeth
 
 . But it would be a place—a real place—that would look nice on a poster. “It may not be perfect,” these ideal aliens may beam in a message to us, “but it will always be home.”

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<h2>
 Missing an Imagined Planet
</h2>

 Just as American states have tourism offices and ad campaigns, touting their lush landscapes and theme parks, NASA has an “Exoplanet Travel Bureau.” On its website, you can click to twist and turn around the foreign (illustrated, imagined) surfaces of other worlds, or you can download a promotional poster that portrays these orbs as vacation destinations. There’s the double-starred planet Kepler 16-b, “where your shadow always has company.” Or Kepler 186-f, “where the grass is always redder,” because it orbits a red-dwarf star whose longer-wavelength light may have influenced photosynthesis. On PSO J318.5-22, “the night life never ends”—because it travels through space starless. On huge HD 40307g, meanwhile, you can “experience the gravity of a super earth.”

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/exoplanet-posters-2.width-990_DxUkc3E.jpg"/>
<figcaption>NASA produced a series of posters that evoke vintage travel advertisements, suggesting a nostalgia for places we've never known.
 
 </figcaption>
</figure>

 The posters are done up in the vintage 1930s style of Works Progress Administration advertisements—the Bauhaus-inspired, dreamy types that people now hang framed in their hip houses. Those creations encouraged contemporaries to “See America.” NASA, though, wants the viewer to see something else entirely: planets they can never actually visit. The agency’s posters show a two-shadowed solo pioneer facing a frontier; a person in front of a white picket fence, fronting red foliage; a formally dressed and handsy couple at a late-night social event; and a person skydiving toward a planetary surface.


 Exoplanet astronomers almost always put these posters in their public-presentation PowerPoints, Messeri says.
 
 Here’s what it might be like if we could go to the places we study
 
 , the images convey. Fun!


 We humans miss that perfect place, creating a bizarro nostalgia that tinges the science, and the artistic representations from the Exoplanet Travel Bureau: the vintage style, the long-gone American-dream fence, the couple that’s happier and having more fun than we are right now. These posters, these planets, present us with the idea that although an Edenic and unspoiled life isn’t possible on Earth anymore, it could perhaps exist somewhere else—a somewhere else for which we’re homesick.


 “What does it mean to be nostalgic for something we haven’t discovered yet?” Messeri asks. “To long for a sense of home in a place that’s not our own planet?”


 Image credits: Dan Addison/University of Virginia, NASA/JPL


 Video credit: Conceptual Image Lab/Goddard Space Flight Center/NASA

Our search for life beyond Earth is more than scientific—it’s a quest to find our perfect selves.

How big a deal was Stephen Hawking’s big black hole announcement?

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 “Can you hear me?” Stephen Hawking asked as he was about to begin his August 25 talk at the Royal Institute of Technology’s
 <a href="http://www.nordita.org/hawkingradiation/">
 “Hawking Radiation” conference
 </a>
 in Stockholm.
 

 The 29-person audience, all VIP physicists, was eager to hear his big announcement and could hear him just fine. They knew, from a pre-announcement announcement the previous night, that Hawking was about to explain his solution to a 40-year-old mystery in physics: how information escapes from black holes.
 

 But while his idea made big headlines, the mere nine minutes of explanation felt vague and confusing to other physicists.
 
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/pia16695-620_crop.width-990_zbwaBpN.jpg"/>
<figcaption>Artist's concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Credit: NASA/JPL-Caltech
 
 </figcaption>
</figure>


 What is Hawking’s problem?
 


 Hawking set out to resolve a problem called the “
 <a href="http://www.pbs.org/wgbh/nova/blogs/physics/2013/12/do-black-holes-destroy-information/">
 information paradox
 </a>
 .” Understanding this snag requires a brush-up on
 <a href="http://science.nasa.gov/astrophysics/focus-areas/black-holes/">
 black holes
 </a>
 . If light or matter venture past a boundary around the black hole called the “event horizon,” they are done for: The speed required to overcome the black hole’s gravity and escape is greater than the speed of light. So anything that crosses the event horizon—and any information about what it was in its previous life—stays inside the black hole. Whether you, a Snickers bar, or a whole planet fall in, they all end up the same: as anonymous extra mass piled onto the black hole itself.
 

 Or at least that used to be the idea. Then, in 1974, Stephen Hawking showed that black holes slowly evaporate. They continuously leak radiation (later named “Hawking radiation”), dwindling away until there’s nothing left, on timescales ranging form a few billion years to much longer than the current age of the universe. But, as theoretical physicist Carlo Rovelli of Aix-Marseille University, who attended the talk, explains, “This creates a problem: Where has all the stuff gone that fell inside? Where is the information about what fell in? It cannot be anymore ‘just inside,’ because the black hole has disappeared. So, where is it? Is it really lost?”
 

 Quantum mechanics says that information about the stuff can’t be lost. Information can neither be created nor destroyed. But black holes seem to destroy it. But they can’t. But they seem to. That’s the “paradox” part of the information paradox.
 

 Some scientists think the escaping Hawking radiation carries the information out with it, like a set-free hostage who can tell police about the room he just spent five days in.
 

 Ideas abound about how that radiation might spill the beans, and Hawking’s new revelation is just one contender. “The situation is not that there is a big problem, and here is the solution,” says Rovelli. “The situation is that there is a big problem, and there are a dozen solutions … none totally convincing, and now we have a new one.”
 


 Hawking’s big idea
 


 On August 25, as Hawking sat before the esteemed physicists, his voice played through the room’s speakers. “I propose that the information is stored not in the interior of the black hole, as one might expect, but on its boundary, the event horizon,” he said, “in the form of supertranslations of the horizon.”
 

 Translation: If you passed over the event horizon, you would leave an imprint on it. That imprint takes the form of, essentially, a hologram called a supertranslation—a two-dimensional representation of your three-dimensional parts—etched into the black hole’s exterior geometry. When Hawking radiation bubbles up, the event horizon leaves a similar imprint on that radiation. It’s like cosmic re-gifting. The Hawking radiation then streams back out into the universe, carrying the imprint, and the encoded information, with it. That code, though, is scrambled: If you fell into a black hole, we could not create your clone from it (sorry). But, cold comfort, your informational essence wouldn’t be eternally lost.
 

 The idea that information could be stamped onto a black hole’s event horizon was first proposed by Nobel Laureate Gerard ‘t Hooft, and supertranslations—as mathematical ideas—
 <a href="http://journals.cambridge.org/action/displayAbstract?fromPage=online&amp;aid=2055372">
 come from the 1960s
 </a>
 . We don’t yet know enough about Hawking’s idea to detail how new and different it is.
 


 The problem with Hawking’s solution
 


 And that’s part of the problem: According to colleagues, the details of his “solution” feel fuzzy. “Two big questions are where the information from infalling stuff gets deposited, and how that information later gets transferred to stuff leaving the black hole,” says Steven Giddings, a physicist at the University of California, Santa Barbara.
 

 Those
 
 are
 
 two big questions—the biggest, most fundamental questions. It’s great that Hawking described the
 
 what
 
 of his idea, but, in science, the
 
 how
 
 is much more important. “What we need for a more detailed understanding is a more complete description of the mathematics … to see if they’ve really nailed the answer,” says Giddings. Rovelli agrees, stating, “The picture is very preliminary for the moment.”
 

 They weren’t the only two left scratching their heads. “In the conference, there were many world-class physicists, including Nobel Prize winners,” says Joe Polchinski, Giddings’ colleague at UC Santa Barbara. “I didn’t perceive much enthusiasm about the new idea. Everybody was interested, of course, but I couldn’t detect anybody that appeared convinced.”
 

 Polchinski, who has previously science-battled Hawking about
 <a href="http://www.pbs.org/wgbh/nova/blogs/physics/2014/02/stephen-hawking-serves-up-scrambled-black-holes/">
 black hole paradoxes
 </a>
 , also pointed out a problem beyond the idea’s fuzziness: In Hawking’s scenario, information stays on the event horizon. But the information (using the previous example, you yourself) also falls into the black hole, meaning two copies of it would exist. “In quantum mechanics, information can’t be in two places,” Polchinski says, although he points out that Hawking may have found a way to evade this problem.
 

 Because Hawking’s black-hole revelations (as well as his proclamations about
 <a href="http://www.popsci.com/science/article/2010-04/hawking-aliens-are-out-there-and-want-our-resources">
 aliens
 </a>
 and
 <a href="http://www.techtimes.com/articles/16687/20140930/atheist-stephen-hawking-denies-god-existence-science-more-convincing-explanation-for-universe.htm">
 religion
 </a>
 ) receive public buzz and papers called “
 <a href="http://arxiv.org/abs/1507.00591">
 AdS/CFT without holography: A hidden dimension on the CFT side and implications for black-hole entropy
 </a>
 ” don’t, it may seem that his idea is totally novel. But it’s not. “From what we here understand, his suggestion builds on ideas that people have been tossing around recently,” says Giddings. Rovelli and Polchinski also point out its similarity to
 <a href="http://profmattstrassler.com/articles-and-posts/relativity-space-astronomy-and-cosmology/black-holes/black-hole-information-paradox-an-introduction/">
 ’t Hooft’s 1990s ideas
 </a>
 , although Hawking has added “some technical steps.”
 

 Hawking claims he, and co-conspirators Andrew Strominger of Harvard University and Malcolm Perry of Cambridge University, will leak more information in a paper in late September. If that paper throws around some convincing equations—what black-hole theorists require as evidence—the result could be a big deal. Until then, scientists are waiting to reserve judgment. “For the moment the theory is far too sketchy, in the manner it has been presented,” Rovelli says. “Let me put it this way: The big news is Hawking himself: his persona, his popular fame, the wonderful manner in which he communicate to the public and transmits enthusiasm to the public. This is fantastic and is his mastership. His physics is interesting, as many others’ are.”
 


 Go Deeper
 
 

 Editor’s picks for further reading
 


 KTH Royal Institute of Technology:
 <a href="https://www.kth.se/en/aktuellt/nyheter/hawking-offers-new-solution-to-black-hole-mystery-1.586546">
 Hawking offers new solution to black hole mystery
 </a>
 
 Read a summary and watch video of Hawking’s August 25, 2015 talk.
 

 Scientific American:
 <a href="http://www.scientificamerican.com/article/stephen-hawking-hasn-t-solved-the-black-hole-paradox-just-yet/">
 Stephen Hawking Hasn’t Solved the Black Hole Paradox Just Yet
 </a>
 
 Clara Moskowitz tempers the buzz around Hawking’s August 2015 announcement.
 

 The Washington Post:
 <a href="http://www.washingtonpost.com/news/speaking-of-science/wp/2015/08/29/after-a-week-of-intense-debate-stephen-hawking-and-his-colleagues-are-still-puzzled-by-black-holes/">
 After a week of intense debate, Stephen Hawking and his colleagues are still puzzled by black holes
 </a>
 
 Rachel Feltman, who runs The Washington Post’s Speaking of Science blog, reports on the broader takeaways from the Hawking Radiation conference.
 
</section>

Stephen Hawking proposes a new answer to the black hole information paradox.

NASA Likely to Break Radiation Rules to Go to Mars

NASA’s biggest obstacle to sending humans to Mars may not be related to line items in budgets, but to the safety of the astronauts themselves.


 Despite having sent humans into space for nearly 55 years, NASA doesn’t quite understand what risks the radiation out there poses. More importantly, the agency doesn’t know exactly how to manage those risks—and it might not be able to.

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 Space radiation presents the tallest hurdle to NASA’s future travel plans that extend beyond low-Earth orbit and for periods longer than a year. On the International Space Station, astronauts are bombarded with 10 times as much radiation as they experience on Earth in a given period; on Mars, they will encounter 100 times the terrestrial dose.


 When NASA sends astronauts on its planned two-year-long Martian trip, they’re probably going to break their own rules about radiation exposure, which already set limits above those for most workers here on Earth. As a report from NASA’s Office of the Inspector General put it, “Based on current knowledge, astronauts on a mission to Mars would exceed NASA’s career radiation dosage limits. Although the Agency plans to continue efforts to develop countermeasures to address the radiation risk, NASA is likely to seek an exception from the current standards for those that cannot be fully mitigated.”

<h2>
 12 Month Study
</h2>

 NASA’s understanding of the effects of long-term exposure to radiation in deep space is still in flux. While the government has been concerned with radiation hazards on a potential Mars mission since going to the fourth planet became a goal, it wasn’t until November 2012 that they realized they had the opportunity to perform a controlled experiment on humans, looking at the effects of space radiation.

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 NASA was set to announce that astronaut Scott Kelly would go to the Space Station for 12 months, to participate in the agency’s aptly named One Year Mission. The plan was to send an American astronaut—Kelly—and a Russian cosmonaut—Mikhail Kornienko—to orbit for twice as long as most space-farers, and then study the physiological and psychological effects of the trip. The results would help space agencies prepare for longer-term space missions like the planned journey to Mars.

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/kelly-twins-nasa-prep.width-990_BJG6AV6.jpg"/>
<figcaption>Twins Mark and Scott Kelly participated in a NASA study to determine the effects of long-term exposure to space radiation on the human body.
 
 </figcaption>
</figure>

 The day before the press conference, NASA officials met to help Kelly prep. At the very end of the gathering, as everyone was shuffling papers and standing up to leave, someone asked, “Hey, are we doing anything with the twins?”


 By this, they meant Kelly’s gene-sharing, same-aged brother, Mark Kelly—who had also spent time in the astronaut corps.


 “No, that would just be a stunt,” said John Charles, head of the One Year Mission. “We’re not going to do anything.”


 But as people began to file out of the room, Mike Barrett—Charles’s boss and manager of NASA Human Research Program—stopped Charles and said, “Not so fast.”


 And soon, they sat down and made a plan for the “Twins Study,” mapping out research that would be good for more than just publicity: a formal project to compare how the bodily and brainy functions of Mark—living, as Charles says, “la vida loca” as a retiree in Tucson—and Kelly—living in space. Scientists would study how the characteristics of a claustrophobic space environment—the lack of gravity, the astronaut ice cream, the serotonin-boosting view out the window, the cortisol of launch, the screwed-up sleep schedule—contributed to any differences between the two men’s biology. “Our experiments are not clean. They are a juxtaposition of all these stressors,” Charles says. “We, being rocket scientists, try to figure out which phenomenon is related to which stressor.”


 And perhaps the biggest body-stressing difference between Earth and orbit is the amount of bombarding radiation.

<h2>
 “Like Cellophane”
</h2>

 Radiation is the catch-all term for high-energy particles like protons and nuclei that can tear into human microanatomy. A few different kinds of radiation exist under that umbrella: the radiation that’s trapped by the Earth’s protective electromagnetic shield; the radiation that comes from the Sun; the radiation that comes from deep space, like supernova explosions; and the secondary radiation that is spawned when, say, a supernova particle smashes into some other matter, like a spacecraft hull or an astronaut’s head.


 The Earth-trapped radiation and the particles that fly from our star don’t pose huge problems, because the former is localized and the latter doesn’t have much energy (comparatively). But those deep space particles, more formally called “galactic cosmic radiation”—watch out, journeyers.

<div class="pullquote">

 OSHA gave NASA a waiver, allowing the agency to create its own radiation guidelines.

</div>

 “They rip through you like you’re cellophane,” says biomedical and health informaticist Dan Masys of the University of Washington. Engineers haven’t yet found a way to protect astronauts’ fragile, cellophane selves against such bombardment.


 NASA sets its own thresholds for how much radiation is too much, but that wasn’t always true. Astronauts used to fall into the Occupational Safety and Health Administration’s “radiation workers” category, like pilots and people who work at nuclear reactors. OSHA places caps on the particles a worker can encounter and, on top of that, demands that organizations keep exposure “as low as reasonably achievable.” They call this the ALARA Principle.


 But today, ALARA is the only principle by which NASA abides. Terrestrial radiation worker limits proved too low for celestial employees, so OSHA gave NASA a waiver, allowing the agency to create its own guidelines. OSHA’s limits don’t apply anymore. NASA’s Office of the Chief Health and Medical Officer now sets the limits, which say that an astronaut’s exposure to radiation shouldn’t increase their risk of death from cancer by more than 3%. Yet that same office will grant new exceptions if trips beyond low-Earth orbit will put astronauts at radiative risk greater than what’s now allowed, as the agency suspects they will.

<h2>
 “It Depends”
</h2>

 NASA’s current chief medical officer is J.D. Polk. And Polk tells me that while some other space agencies lay down a blanket radiation limit—saying none of their employees can exceed a set and static dose—NASA doesn’t. Instead, the agency takes an astronaut’s age and sex into account. Women have higher cancer risk because of their breasts, ovaries, and uteri; they also have an unexplained increased risk of radiation-induced lung cancer. Their limits, then, are lower than men’s.


 The older someone is, the less a doped-up dose means to them. “If I expose a 55-year-old astronaut to radiation and they have 20–30 years in which that radiation exposure might produce a cancer, that’s a different risk than if I expose a 30-year-old to that same radiation,” Polk says. “So if you ask what the NASA career limit is, the answer is, ‘It depends.’ ”


 And if you ask whether NASA would be willing to break its cancer-focused career limits to go forward with a big-picture space mission, the answer is maybe.


 But the trouble is that the radiation problem isn’t limited to cancer, something which NASA acknowledges. They have it all laid out in a set of thirty-plus “Evidence Reports on Human Health Risks” that are produced by their Human Research Program and reviewed by the National Academy of Sciences, which selects independent experts to assess the quality and rigor of NASA’s work.


 Masys is one of those experts. This year, he was the vice-chair of the committee that prepared the fourth of five such assessments, one slated to come out each year from 2014–2018. Each addresses a subset of the tens of evidence reports, which deal with everything from sleep loss to habitat design to the microbiome to nutrition. Much of this year’s analysis dealt with radiation reports. Masys says that, so far, NASA hasn’t been surprised by anything the committee has said—“other than their mild surprise that we have anchored radiation as the deal breaker,” he says. “It is the showstopper for what NASA calls exploration-class missions.”


 Both NASA’s and the Academy’s documents say that long-term missions will be radiation-risky for the foreseeable future—maybe forever.


 Masys doesn’t use the words “deal breaker” and “showstopper” lightly. According to NASA’s reports and the Academy’s evaluation, cancer-inducing radiation can also cause cardiovascular and degenerative diseases—like cataracts, premature aging, and endocrine problems—a risk “of much greater concern than previously believed.” It can also rejigger the central nervous system, screwing with everything from cognition to spatial perception to hand-eye coordination. Then there’s the infertility, the cataracts, the slow wound healing, and the problems that astronauts could pass on to future children if they make it back from the long trip to Mars and manage to procreate.


 For several of these medical matters, scientists don’t understand the underlying mechanisms. And so far, their research into those mechanisms, and their manifestations, has mostly involved the low-energy particles from Earth or near-space—not the high-energy cosmic rays from farther off—and radiation exposure that falls in one fell swoop, like the swoop of a nuclear bomb. Often, too, researchers base their conclusions on animal models that they haven’t translated to humans. Both NASA’s and the Academy’s documents say that long-term missions will be radiation-risky for the foreseeable future—maybe forever.


 “For as long as there have been catalogs of health effects, radiation has been the most intractable, most severe, hardest problem to solve,” Masys says. “Now, 20 or more years into advances in space technology and propulsion and systems and vehicles, radiation is still the deal breaker. It has never changed.”

<h2>
 Engineering Solutions?
</h2>

 NASA has been hard at work on the problem. The agency is attempting to determine how radiation might impact crewed Mars missions with research projects like the Twins Study and the One Year Mission, with on-the-ground facilities like the Space Radiation Laboratory, and with biology research in laboratories. But they are also hoping to engineer ways to decrease exposure.


 “We talk about time, distance, and shielding,” Polk says. If the agency creates faster rockets, astronauts can spend less time in transit. They can time trips for low-emission points in the solar cycle that also put Earth close to Mars. And then they can build better barriers between astronauts and space. Perhaps advances in nano- or materials science will bring a lightweight, launch-friendly material that efficiently traps the offending particles before they slam through skin. Medical types could also develop drugs that undo or protect against bodily harm when particles do slam into skin. But none of those are reality yet.


 “NASA, as a future-thinking engineering organization, believes they will find a solution,” Masys says. “And so the real issue is, well, how soon? They would be the first to tell you there is not a solution in hand right now.”


 In the future, when NASA is actually making deep-space trips, engineers and biologists will likely have better tools on hand. But will those tools allow NASA to abide by its astronaut-protecting guidelines? Or will the agency alter the guidelines for the good of human exploration?

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/orion-crew-module-heat-shield.width-990_gxBKdjp.jpg"/>
<figcaption>The Orion crew module will not be enough to protect astronauts from galactic cosmic radiation.
 
 </figcaption>
</figure>

 It’s a burden that NASA has to bear, but one the private space industry doesn’t have to bother with. If Elon Musk wanted to send someone to Mars tomorrow, radiation guidelines probably wouldn’t stop him.

<div class="pullquote">

 “Nonemployees are likely to be exempt from dose limitations.”

</div>

 Private space companies like Musk’s SpaceX fall under the watchful eyes of the Department of Transportation and the Federal Aviation Administration. Crew members—employees of the space tourism company—will be protected by OSHA regulations. But occupational standards don’t apply to the passengers, who are not working for SpaceX or whoever else flies beyond the atmosphere, or for the federal government. As Alyssa Megan Sieffert, now an attorney-advisor at NASA’s Office of the Inspector General, wrote in the journal
 
 The SciTech Lawyer
 
 , “Nonemployees are likely to be exempt from dose limitations.” They could, potentially, endure as much radiation as they want. If Musk wanted to send a remotely operated, fully-tourist trip to Mars—as with the two tourists he’s sending around the Moon in 2019—he just could, as long as he informed them all the radiation wasn’t good for them.


 The way the law works, the Secretary of Transportation cannot create preventative regulations that would stop the first rich tourist from dying of cosmos-caused cancer or cardiovascular disease while cataracts cloud their eyes. As the code says, regulations issued by the secretary “shall…be limited to restricting or prohibiting design features or operating practices that…have resulted in a serious or fatal injury…during a licensed or permitted commercial human space flight; or contributed to an unplanned event or series of events during a licensed or permitted commercial human space flight that posed a high risk of causing a serious or fatal injury.” In other words, only once something goes wrong in commercial spaceflight can the Secretary bring into being a new safety regulation to prevent a similar situation from happening in the future.

<h2>
 No Easy Task
</h2>

 Research like the Twins Study will help medical types determine the effects and ethics of that rule-breaking. NASA released the radiation data from the Kelly Study to researchers on February 28. “They’re just now opening those files up,” Charles says.


 Figuring out how radiation affected Scott Kelly’s corporeality—and how it didn’t—won’t be easy. “This is not like
 
 Bones
 
 or
 
 CSI
 
 ,” Charles says. “You don’t pick up a cigarette butt and put it in your whizmo machine.”


 Regardless of the findings, though, of these or future studies, astronauts like Kelly would probably always raise their hands to go, whether it was strictly good for them or not. “Astronauts are a risk-taking group. That’s part of their persona,” Masys says. “The agency has to have a more prudent approach to risk than the astronauts themselves.”


 Photo credit: NASA, Lockheed Martin

Mars-bound astronauts will likely be exposed to high levels of radiation—far beyond what NASA typically allows.

How Landowners Helped Save the Rogue

<div class="related"></div>

 Bill Leavens was one of the chosen ones.


 Leavens owns a 125-acre plot that sits beneath Lower Table Rock, a volcanic plateau from which a mythical creature might overlook the valley and say, “It is good.” Leavens, who, before retirement, ran an aggregate mining company, had long struggled to manage his riverfront acreage. When he looked out at his section of the Rogue, he saw Himalayan blackberries standing 12 feet tall along its banks. The unchecked fruit choked out the trees. Choked out everything, really.


 Then came Eugene Wier’s knock at his door, offering to rip out those bushes, and replace them with around 2,500 linear feet of trees—cottonwood, elderberry.


 “Why me?” Leavens asked.


 “I’m not just here because you’re a nice guy,” Wier said. “I’m here because you’re the right person.”

<h2>
 Mapping Medford
</h2>

 It all began in 2011, when Medford, Oregon, had a water problem. The local wastewater treatment plant was shooting 26 Olympic swimming pools’ worth of water back into the Rogue River every day. That water was clean, sure—but it was warm. It sounds like a minor issue—compared with raw sewage, a bit of warm water doesn’t seem like a big deal. But just as pouring newly hot coffee into a tepid cup makes the formerly tepid part less tepid, adding the warm once-wastewater back in increased the river’s heat. That cut down on the oxygen levels, making fish eggs hatch earlier than they should. If city politicians did nothing to offset the warmth, the increase would leave them in violation of the Clean Water Act.


 The city considered a cooling tower—a steaming, nuclear-looking monstrosity—or a holding pond in which the water could dissipate its heat skyward before flowing into the river. But both of those were expensive and synthetic. A nonprofit, the Freshwater Trust, presented a more palatable idea: planting shade trees along the Rogue, whose shadow-slinging would cool the water.

<div class="pullquote">

 If city politicians did nothing to offset the warmth, the increase would leave them in violation of the Clean Water Act.

</div>

 After the city bit, the Freshwater Trust developed a tool called BasinScout. Today, it hoovers in data—from soil samples to bank angles to satellite images—and exhales a color-coded map that shows how restoration efforts (like lining shade trees along the Rogue) could affect the liquid around a given plot of land. BasinScout allowed them to pinpoint “red” areas—land ripest for restoration. And then they called in a local, Eugene Wier.


 Wier is always out on Oregon’s Rogue River—floating, fishing, and managing the restoration projects that dot its banks. Though Medford is the fourth-largest metro area in the state, most of the land around it is rural, a Crayola box of green laid down along the Rogue River in between mountains. The Portland-based Freshwater Trust plucked Wier—a plaid-shirt-and-sleepy-smile kind of guy—from other restoration work and asked him to manage their projects in the Southern part of the state. They needed someone local who loved the Rogue, and who locals knew loved the Rogue, to manage their projects.


 “I’d been doing what we’d call quote-unquote traditional restoration,” he says, “Applying for grants, finding a willing landowner,” since the property in question often belongs to private citizens. The grants usually lasted three years, and then the landowner was on their own. “Those projects often fell back into the bushes,” Wier says. He hated that. He has parental feelings about the projects. “I want to see them grow up and graduate,” he says.


 The Trust, though, would give him these BasinScout maps, with their ribbons of color, and the promise to support each restoration project for 20 years.


 He said yes, and then took a look at those maps, which showed where some strategic planting could have the best chilling effects. Wier knew he had to be strategic in choosing which landowners to approach first. He was going to be asking a lot when he knocked on their doors: not just to change the shape of their land but to access it for two decades.

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/inline-1_2048x1152.width-990_WFEI2YJ.jpg"/>
<figcaption>Eugene Wier, Restoration Project Manager based in Ashland, stakes a sign alerting the public of restoration in progress along the Leavens property in southern Oregon.
 
 </figcaption>
</figure>

 Whoever said “yes” first could help convince others to sign on. “People are going to do it for a lot of reasons,” Wier says. “But the first person has to be someone who believes in this.”


 When he looked at his list, he knew which of the potential landowners might be willing to suspend disbelief long enough to let some trees grow: Bill Leavens, a former mine operator and businessman who’d been to local river restoration meetings before.


 Wier didn’t know Leavens well, but well enough. “He’s authentic,” Wier says. “He’s business-oriented. He’s not just a tree hugger. If he likes this, other guys are going to like this and notice.”


 So Wier went to knock on Leavens’s door—armed with cartographic evidence that this was the right place to be.

<div class="ad"></div>
<h2>
 Digitizing Data
</h2>

 The motivation for BasinScout actually came about because Medford was so big, and so spread out. There were hundreds of potential landowners to approach, and the Trust couldn’t—at least not cost-effectively—knock on every door. They needed to up their efficiency. They needed to find the right people, like Leavens.


 So they turned to digitized data. BasinScout’s current incarnation can pull in satellite and other aerial images, soil samples, and laser-based mapping data from airplanes. After feeding it all to BasinScout, the team can look at how newly planted trees, once mature and fully shady, can affect rivers and streams.


 Such a data-driven approach is not strictly novel. “Watershed assessments in and of themselves are nothing new,” says Julia Bond, The Freshwater Trust’s science director. “People have been doing them for decades.” But what sets BasinScout apart is its focus on individual landowners, and how their their restoration contributions can sum to a greater whole.


 BasinScout, in other words, turns big-picture digital data into detailed portraits that people can make sense of. And for the Trust, it makes finding those people easier. “Rather than knock on hundreds of doors to find the half dozen, we can start with 20 or 30,” says Denis Reich, the organization’s recruitment and Southern Oregon director.


 Leavens didn’t say yes right away. “It was a little intimidating,” he says. “I was basically giving them access to the river frontage for 20 years.”


 This Portland organization wanted to come in and do what they would with his land—his land—for an awfully long time.

<div class="pullquote">

 BasinScout turns big-picture digital data into detailed portraits that people can make sense of.

</div>

 He thought their idea was exciting (and he wanted someone else to deal with his blackberries), but Leavens wasn’t sure he could trust them—to do what they said or to continue existing as a functional organization for 20 years. How could he address every concern, when he couldn’t see the future, in a contract?


 Leavens talked to his lawyer, and, in words that perhaps have never come out of any other attorney’s mouth, was told that he had to put some trust in people. “You’re not going to get everything in an agreement,” the lawyer said.


 Leavens followed the unconventional legal advice. And the Freshwater Trust soon hired local labor to come plant the 6,900 trees from a nearby nursery.

<h2>
 Investing in Trust
</h2>

 And with that, Leavens became the Freshwater Trust’s man on the inside, which helped the Trust recruit other landowners. If Leavens trusted the Trust, the reasoning went, maybe it was okay to let hippie-nonprofit Portlanders onto their property for the next 20 years. Plus, the other guy, Wier, was local. He loved the river. People—the kind who’d been there forever and the kind who moved there just for the prettiness and recreation—perhaps thought they could trust him with their land.


 It worked. Other people trusted the Trust.


 Wier is currently working with Leavens’s downstream neighbors. After Leavens first signed on, five or so years ago, Wier knocked on their door, too. But they weren’t interested. They’d seen mediocre restoration projects that were left to wither with little to show for results.


 Today, though, the neighbors look with some envy upstream at Leavens’s property, which was once tangled with weeds but, five years after planting, is now flush with 10- to 30-foot-tall native trees.

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/inline-2_2048x1152.width-990_Jh9IzyE.jpg"/>
<figcaption>Native plants installed by The Freshwater Trust alongside the Applegate River, a 51 tributary of the Rogue in Oregon.
 
 </figcaption>
</figure>

 The Trust, with the help of BasinScout and a lot of digging, has planted some 50,000 trees along the Rogue River since that first one plopped into a hole on Leavens’s property. And, in general, the recruitment wasn’t as difficult as Reich thought it might be. That’s in part because land along Rogue has ballooned in price—thanks to Californians moving in with their tech millions and staring, removed from the rat race, at the eye-soothing land that someone used to farm. “Most of the landowners have never heard of a cow or milked one,” Reich says, mostly joking. “They’re attorneys or tech guys or entrepreneurs, and they want their slice of heaven.”


 But Patient Zero—Leavens—is not one of those Californians. And he was one of the most skeptical Reich says he’s seen. He’d be the first to tell you, he says, if the Freshwater Trust’s work wasn’t successful. But so far it has been.


 And Leavens is optimistic that it will be into the future. Part of that comes from the long-future investment the Trust promises. But it also comes from the data the group used to back their initial decisions, data that includes satellite imagery. Our view of the Earth from above is increasing by terabytes every day. There are hundreds more Earth observation satellites in orbit around Earth than there were just a few years ago. All of this imagery reveals land and water as they are right now, how they were a week or a year ago, and how they’ll be tomorrow. With airplane and field-gathered data, and there’s almost too much information.


 But it’s better than having too little. And the plan takes ground truth, literally, into account. The Trust’s people trekked on and off Leavens’s land periodically, poking and prodding and digging and measuring each year to check its status. Leavens was initially wary, but now he’s glad for that. “They assess the site and make modifications to their plan on an ongoing basis rather than planting it and just talking about the great things they did,” he says.

<div class="newsletter"></div>

 Photos courtesy The Freshwater Trust

One conservation organization is turning to digitized data to restore Oregon’s Rogue River.

The B-Mode Story You Haven’t Heard

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>

 It’s a tough time to be a B-mode.
 

 B-modes rocketed to fame in
 <a href="http://www.pbs.org/wgbh/nova/blogs/physics/2014/03/first-direct-evidence-of-cosmic-inflation/">
 March 2014
 </a>
 , when a team of scientists working on an experiment called
 <a href="https://www.cfa.harvard.edu/CMB/bicep2/">
 BICEP2
 </a>
 announced the first direct evidence for primordial gravitational waves rippling out from the earliest moments of the universe: a distinctive imprint in the cosmic microwave background (the light left over from the Big Bang) called “B-mode polarization,” or B-modes for short. Polarization describes the way that light-waves are oriented, and B-mode waves are twisted into a swirling pattern. The detection of these swirls was a stunning confirmation of the theory of cosmic inflation. Suddenly, B-modes were electromagnetic celebrities.
 
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/cmb_620.width-990_P0CpoTz.jpg"/>
<figcaption>Polarized emission from Milky Way dust, which complicates the search for B-modes from the era of inflation, as seen by the Planck telescope. Credit: ESA and the Planck Collaboration
 
 </figcaption>
</figure>

 But the story went sour just weeks later, when doubt arose that the B-mode signal was really coming from the era of inflation. Eleven months after their first, much-buzzed-over announcement, the researchers conceded that some or all of the CMB swirling might actually be due to nearby galactic dust. They had not necessarily detected gravitational waves at all, but perhaps just flecks of dirt floating in the space around us.
 

 And so, deserved or not, the B-mode story became a cautionary tale. But in reality, there are a variety of different astrophysical processes that create B-modes—processes better understood and tested than inflation—and B-modes can reveal a great deal about the universe. Telescopes like
 <a href="http://lambda.gsfc.nasa.gov/product/polarbear/">
 POLARBEAR
 </a>
 , now being expanded into a three-telescope set called the
 <a href="http://cosmology.ucsd.edu/simonsarray.html">
 Simons Array
 </a>
 , can study not just the birth of the cosmos but also the galaxies it has produced, the dark matter it tries to hide, the oldest magnetic fields it made, and more. They have been returning results this whole time, and what they discover about the universe is only going to get more interesting as they continue to spy into space.
 


 Mapping the Milky Way’s Magnetism
 


 After the controversy, dust seemed like the enemy. But, as BICEP2 team member Brian Keating of the University of California, San Diego says, “One scientist’s trash is another scientist’s treasure.” And this dusty trash tells us about our own galaxy. The grains, left behind from star formation and spewed out in supernova explosions, line up like soldiers along the Milky Way’s magnetic field lines. “They become a swirling pattern of microwave emission that looks like B-mode polarization,” says Keating.
 

 By tracing out the dust’s swirls, scientists can make a better map of the galaxy’s magnetic field. But that’s not a trivial pursuit, says Jamie Bock of Caltech, because it’s hard to make a 3-D map of a structure that encloses you. Imagine trying to make a realistic map of a forest without leaving your campsite! The cosmic cartographers have their work cut out for them, even with the help of B-modes.
 


 Weighing the Universe
 


 By the time a CMB photon, or particle of light, hits the Milky Way, it has already journeyed billions of light-years. And along the way, it has passed a lot of roadside attractions. “Each photon encodes the properties of everything it encountered on the way to us,” says Keating. “The most significant thing it encounters is gravitational potential,” that is, the stretching of space-time under the gravity of massive objects.
 

 You can imagine space-time as a trampoline. Massive objects warp the trampoline more than tiny ones. For example, if you place a pencil on the trampoline, it hardly makes a dent. But if you put a penguin there, the stretchy material will dip down around the animal. Now, if you roll a marble near the penguin, the dip will change its path. In a similar way, the space-time dip from a galaxy cluster will change the path of a CMB photon.
 

 The wonkiness of the photon’s travel changes the B-modes. And from the size and shape of those shifts, scientists can figure out how much stuff the photons encountered on their trip. “You can measure mass in the entire universe without holding it,” says Keating.
 


 Cosmic Mousetrap
 


 That mass is some 80 percent dark matter. We often think of dark matter as a single thing — some mysterious particle we haven’t discovered yet. But there’s more to it. “There are many types of ordinary matter,” says Keating. “So why should you expect that dark matter would be any different? There could be hundreds of different flavors of dark matter.” But we only know of one flavor for sure: the neutrino, a tiny neutral particle that travels nearly the speed of light and earned two scientists the
 <a href="http://www.pbs.org/wgbh/nova/blogs/physics/2015/10/neutrino-physicists-win-nobel-but-neutrino-mysteries-remain/">
 2015 Nobel Prize in Physics
 </a>
 .
 

 Like cosmic mice, they’re hard to find because they are small, move fast, and don’t interact directly with us. However, they do imprint a specific “signature” on the B-modes, and that signature depends on their mass as a whole and as individuals—both quantities we don’t know yet.
 

 Once our B-mode map is good enough, we will learn about neutrinos — no matter what. “It’s a guaranteed signal,” says Keating, “whereas the B-modes of inflation may not exist at all.”
 


 On the Weird Side
 


 On a larger scale, magnetic fields beyond the galaxy also cause B-modes to swirl out of the static of the cosmic microwave background. Scientists are specifically interested in the most ancient magnetism. Magnetic fields guide the formation and evolution of galaxies and stars, helping to sculpt the raw material of the cosmos into the universe we see today. The POLARBEAR collaboration, a project specifically designed to detect B-modes, exists in part to figure out where magnetic fields come from in the first place. But before it can find an answer to origin, it has to measure this original magnetism. So far, the team members know it can’t be more than a few billionths of a gauss, or a billion times smaller than the mere Earth’s magnetic field. But the specifics are still to come.
 

 B-modes can also show us stranger stuff, too, such as cosmic strings. These “strings” aren’t like those in string theory but are defects in spacetime, like one-dimensional versions of fault lines. They would have formed when the cosmos first cooled off, right after the hot Big Bang.
 

 Most interesting, though, are the total unknowns. “B-modes will tell us if there’s anything in the universe that prefers one polarization versus another,” says Keating. And anytime the universe has a preference, that reveals something fundamental about physics, just like your preferences reveal something fundamental about your personality. On Earth, for example, all life depends on amino acid molecules that face one direction (called “left-handed” molecules), while right-handed molecules also exist in space. And the universe is made mostly of matter rather than antimatter. We don’t yet understand the full reason behind either of those preferences, but we know they are fundamental.
 

 Such fundamentals interest Keating most. “I always wanted to study things that were the purest, most elementary things in nature,” he says. And he believes others want to know about those things too. “It traces back to mankind’s oldest pursuit,” he says. “Where did we come from? We came out of caves and looked up. … I think there’s something primordial in people just like the primordial universe. It’s an urge people have to want to know, ‘How does it all work?’”
 

 We will have to wait to find out how it all works, but the science is moving steadily forward, with
 <a href="https://www.cfa.harvard.edu/CMB/bicep3/">
 BICEP3
 </a>
 now online and POLARBEAR collecting its own photons. “The most exciting CMB project isn’t in the future,” says Bock. “It is right now.”
 


 Go Deeper
 
 

 Editor’s picks for further reading
 


 Nature:
 <a href="http://www.nature.com/news/dust-to-dust-1.16137">
 Dust to dust
 </a>
 
 The editors of Nature ask, what can we learn from the twists and turns of the BICEP2 story?
 

 NOVA Next:
 <a href="http://www.pbs.org/wgbh/nova/next/physics/bicep2/">
 From Discovery to Dust
 </a>
 
 Science writer Amanda Gefter takes a deep look at inflation and the science of the BICEP2 experiment.
 

 University of California, San Diego:
 <a href="http://www.sciencedaily.com/releases/2014/10/141021101142.htm">
 POLARBEAR detects B-modes in the cosmic microwave background: Mapping cosmic structure, finding neutrino masses
 </a>
 
 This press release highlights discoveries from the POLARBEAR experiment, which showed in 2014 that it is possible to isolate B-modes produced by gravitational lensing.
 
</section>

B-modes are still revealing cosmic secrets.

Physics in 1 Trillion Years

When winter weather closed Harvard University one day in 2011, astronomer Avi Loeb used the snow day not to sled or start a new novel but to contemplate the future of the universe. In that future, cosmologists like him, who study the universe’s origins and evolution, might not be able to make a living.


 Nine years before, he had written a paper outlining the problem: Dark energy makes the universe expand faster and faster every femtosecond. As spacetime—the fabric of the cosmos—stretches, it carries galaxies along with it. The stretching sends each galaxy farther and farther from the others, eventually driving them so far apart that light will never be able to bridge the gap between them.


 In that future, our own oasis, the Milky Way, will be completely alone. When future astronomers look up, they will see only our galaxy’s own stars. They won’t find any evidence—even with the powerful telescopes of a trillion years hence—that other galaxies even exist beyond the horizon of their visible universe. Without a view of those other galaxies, they won’t be able to tell that everything was born in a Big Bang, or that the black vacuum of space is expanding at all, let alone that that expansion is speeding up. Ironically, dark energy itself will destroy evidence of dark energy.

<div class="related"></div>

 Thinking of this emptied universe, Loeb stared out the window at the snowfall, which covered the ground in a blank blanket. “I was pretty depressed that there would be nothing to look at, and that we won’t be able to tell how the universe started by observing it.”


 He set out to find a solution.

<h2>
 A Galactic Merger
</h2>

 Currently, cosmic expansion clues us in to the Big Bang. Press fast-forward on the growing universe we see today, and it continues growing, with objects flying ever-farther apart. It doesn’t take much creativity to then press rewind: The universe shrinks, and its ingredients squish together. If you rewind until the very beginning of the tape, everything piles into one infinitesimally small, infinitely dense spot. Press play and it bursts forth: a Big Bang.


 Astronomers only discovered that expansion because they could see other galaxies, which all seem to be running away from us. In 1999, using ultra-distant supernova explosions, they figured out that faraway galaxies were retreating faster than they “should” be, and that even more distant galaxies were distancing themselves faster than that. Something—which they later termed dark energy—spurs expansion on, like a car whose pedal never reaches the metal no matter how hard you push.


 The real problems won’t show up for a while, until about a trillion years after the Big Bang. By that time, the Milky Way will have long ago crashed into the Andromeda Galaxy. The stars will have spent 3 billion years swirling into stable orbits, before becoming a seamless chimera: a single galaxy called “Milkomeda,” a term Loeb coined in 2008 when he simulated and then forecasted the collision’s specifics.

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/milkomeda.width-990_DZk78xV.jpg"/>
<figcaption>Billions of years from now, the Milky Way and Andromeda will merge.
 
 </figcaption>
</figure>

 Even as that galactic collision takes place, dark energy will be dragging everything else away from us. Little by little over billions of years, everything will pop over the visible horizon, along with any physical evidence of its existence, until only our neighbor stars in Milkomeda remain. “The universe becomes lonely,” says Glenn Starkman, a physicist at Case Western Reserve University. He and astronomer Lawrence Krauss of Arizona State University in Tempe wrote an article titled “
 <a href="http://arxiv.org/abs/astro-ph/9902189">
 Life, The Universe, and Nothing: Life and Death in an Ever-Expanding Universe
 </a>
 ,” which also discusses this “lonely astronomer” problem. “The longer you wait, the less you will see and the more of the universe will disappear before your very eyes,” Krauss says.

<div class="pullquote">

 “The three main pillars of the Big Bang will all be gone.”

</div>

 “Earth’s night sky will change,” Loeb says. Stars that humans (or whoever is around) will get to watch in a few billion years will shift radically. Today, the Milky Way appears as a diagonal swash of fuzzy light, the combined photons of billions of stars too small for our eyes to resolve. But when people in the distant future look up at Milkomeda, they will see those stars distributed evenly across the sky.


 If astronomers still live in Milkomeda at that point, they could be thrown into an astronomical dark age. To them, the universe will look like the one we thought we understood before telescopes. Back then, we thought we were the center of the cosmos, and we believed the Milky Way to be the entirety of the universe.


 That universe seemed static and without beginning. Alone in Milkomeda, future astronomers may—validly, based on actual evidence—see it that way, too. “Scientists who evolve on such a world will look out and find that the three main pillars of the Big Bang will all be gone,” Krauss says.

<h2>
 Three Missing Pillars
</h2>

 “It’s a gloomy forecast,” Loeb says. “We won’t be able to look at anything. It’s not just galaxies—it’s any relic left from Big Bang.” Right now, telescopes can see a glow of light left over from the Big Bang. This relic radiation, called the cosmic microwave background, comes from every direction in the sky. The Planck Telescope recently made a high-definition map of it, which is essentially a blueprint of a baby universe. It shows us the seeds that grew into groups of galaxies, tells us what the universe is made of, and tips us off about the very beginning of everything.


 But as time passes, the photons that make up cosmic microwave background cool off and lose energy, increasing their wavelengths. Eventually, those waves—which today are on the order of millimeters—will be bigger than the visible universe. There’s no telescope, not even one a trillion-year-old society could build, that can detect that. “They will no longer be able to learn what we know about the early universe,” Starkman says.

<div class="ad"></div>

 The composition of the universe, which now tells scientists that the Big Bang occurred, won’t help in the far future, either. After the Big Bang, the universe began to cool off. Soon, free-range quarks settled down into electrons, protons, and neutrons, which could then intertwine into hydrogen atoms. Those atoms then smacked into each other and stuck together, fusing into larger helium atoms. In just 30 minutes, most of the helium that exists today had formed. A comparatively small amount has been created inside stars in the few billion years since.


 “Right now, we know the Big Bang happened because 25% of universe is helium,” Krauss says. “There’s no way stars could have made that.” But by the time the universe is 10 trillion years old, stars will have fused most of the hydrogen into helium. That is, in fact, their job. But in doing it so well, they will knock down the last solid evidence that the universe had a beginning at all. “All relics of Big Bang will be gone from us,” Loeb says. “There will be really nothing.”

<div class="pullquote">

 “There may be cosmological observables that we could see in the far future that we can’t see now.”

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 It seems that we live at a somewhat strange time in the universe—one in which our sky is filled with evidence of the cosmic narrative. Does that make us lucky? And does it make future observers unlucky? Astronomers generally shy away from suggestions that we are anything other than dead-average. They call it the Mediocrity Principle.


 But maybe each eon is a special snowflake in its own way, meaning none of them is really special, just like soccer kids who all get trophies. The far-future folks may have easy access to knowledge we, in our dark-energy-dominated and bright-skied time, can’t grasp. “I suspect that each era is interesting for different reasons,” Krauss says. “There may be cosmological observables that we could see in the far future that we can’t see now.”


 We can’t know for sure, nor can we know for sure that this future forecast is correct. Just like perfect weather prediction, it can only happen if we know everything about every subatomic particle. The year 1 trillion CE may not look exactly as we envision it. “That broad picture is what will happen if what we know continues to be the whole truth and nothing but the truth,” Starkman says. “There’s a lot of chutzpah in thinking that’s really so, that we’ve captured everything there is to know about physics.”

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 As the winter storm swirled outside, Loeb considered the dark, empty (potential) future he’d predicted. He hated that so much knowledge—the science he loved—would disappear, like all the galaxies. He had recently given a public talk on the topic, sharing his sadness, and an audience member’s question had sent him reeling: Would this future convert cosmology into a kind of religion? “You would have books talking about the story of how the universe started, but you wouldn’t be able to verify that,” he says. “I was worried that cosmology would be turned into folklore.”


 “There will really be nothing,” he thought again. But then a flash swept through his brain. Nothing—except for one thing. “I realized that not everything is lost,” says Loeb. The key is a type of object called a hypervelocity star.


 “The center of our galaxy keeps ejecting stars at high enough speeds that they can exit the galaxy,” Loeb says. The intense and dynamic gravity near the black hole ejects them into space, where they will glide away forever like radiating rocket ships. The same thing should happen a trillion years from now.

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 “I was worried that cosmology would be turned into folklore.”

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 “These stars that leave the galaxy will be carried away by the same cosmic acceleration,” Loeb says. Future astronomers can monitor them as they depart. They will see stars leave, become alone in extragalactic space, and begin rushing faster and faster toward nothingness. It would look like magic. But if those future people dig into that strangeness, they will catch a glimpse of the true nature of the universe. “Just like Edwin Hubble observed galaxies—historically trying to infer expansion—they could observe those stars outside the galaxy and figure out the universe is expanding,” Loeb says. Starkman says they could accomplish this synthetically, too. “They could send out probes far enough to notice that the probes accelerated away,” he says.


 And then, perhaps, they will imagine pressing fast-forward on this scenario. And, if their imaginations are like ours, they will then think about rewinding it—all the way back to the beginning.


 Krauss doesn’t necessarily buy this. Occam’s Razor states that the least complicated answer is usually the correct one, and that principle will lead these future beings astray. It sounds crazy that the very fabric of the universe is growing larger faster all the time, carrying some runaway star with it. It’s not the explanation that comes to the tip of the tongue. But perhaps more importantly, with just Milkomeda in the night sky, astronomers will have no reason to come up with a theory of anything beyond those stars. Just as pre-telescope scientists thought only of what they could see with their eyes, not of an invisible universe outside of that, so too could future astronomers’ imaginations be constrained.


 Loeb stands by his solution, although he admits it could remain in his 21 st century paper and never occur to someone in the 2.1 trillionth century. “It’s difficult to speculate what will happen in a year or 10 years on Earth, let alone a trillion years,” he says. “We don’t even know if humans will still be around…I’m just talking about what one
 
 could
 
 learn.”


 Which is why Loeb is so intent on forecasting the future cosmos, even though he won’t be around to see it. “Most of my colleagues do not care about the future because they regard themselves as down-to-Earth,” he says. “They only think about things that can be tested or looked at right now. We can’t really observe the future, so they prefer not to think about the future. They often run computer simulations of the universe to the present time and then stop. All I’m saying is ‘Why stop?’ ”


 Image credits: Unsplash/Pixabay; NASA, ESA, Z. Levay and R. van der Marel, STScI, T. Hallas, A. Mellinger

In the far future, will cosmologists be able to decipher the origins of the universe?

What Does Beauty Have To Do with Physics?

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As a Harvard undergraduate, Sarah Demers—now a professor at Yale University—didn’t have the job you would imagine of a young student of particle physics. She wasn’t running code, writing equations on whiteboards, or trawling data for statistically significant signals. Instead, she was sitting in a basement, transforming 10,000 sheets of gold-coated Mylar into an instrument that would go inside the Fermilab particle accelerator.It was menial, tedious labor, and she was the only woman in the windowless room. Even after the transformation was complete, the work and the instrument itself didn’t scream “glamorous.” In its DIY, basement-built glory, the detector looked less like a sophisticated science instrument and more like someone toppled over a set of cheap garage shelves.
Before the job started, she thought she would hate it, and—worse—that she wouldn’t understand the underlying physics, that she was just messing around with foil sheets.But she found that she did understand, and soon she could comprehend not only how the strange instrument worked, but also how it would help reveal fundamentals of physics. “I gave myself permission to think about underlying questions,” she says.
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<figcaption>The galaxy Messier 104
 
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Inside the Fermilab particle accelerator, her instrument looked on as protons collided at near light-speed with their opposites—antiprotons—and the resulting particle shards decayed after the cataclysmic blast. By rewinding that action, physicists could dissect it in slow motion. From there, they could pick up its pieces, discover what matter is made of and the forces that hold it together, and pry it apart.Despite the foil-wrapped contraption’s messiness, those close observations of the femtoscale explosions are what helped her see she beauty. “A lot of us go into science partly driven by how beautiful the theories are,” Demers says.Physicists often describe their earliest experiences with the field as borderline spiritual, moments in which they realized that they—they!—can represent the world with math. They can describe how stars shrink to black holes, how hard you will hit your head if you slip on a banana peel, and how protons fall apart inside particle accelerators. That ability gives them a sense of control in the way that describing something gives humans dominion over it.For many physicists, this fosters a desire to get to the very, very bottom of things: the theory of everything. Such a theory, many physicists often believe, should be beautiful, simple, elegant, aesthetically pleasing. All of the forces should fit under one umbrella; all particles need to emerge from a nested set of equations. No ifs, ands, buts, or loopholes. Physicists sometimes use these qualities, and their opposites—ugliness, caveats, asymmetries—as respective hot-and-cold indicators to guide them on the path toward understanding, describing, and conquering the universe.The current gold standard for describing the nature of reality, the Standard Model, isn’t physicists’ ideal because, among other blemishes, it isn’t perfectly symmetric, and the way it glues fundamental forces together is a little kludgy. That’s partially why scientists have developed a new idea, called supersymmetry, which smooths and extends the Standard Model, giving each of those old-school particles a new-school “supersymmetric” counterpart.Despite the fact that particle physicists have found no evidence of supersymmetry, they continue hunting for the elusive supersymmetric partners—partly because the theory is more aesthetically appealing than the Standard Model.But not all physicists believe that beauty should count as indirect evidence in favor of an idea.As Demers dug in to her research, she began to have doubts. Maybe it was okay for the universe to be a little bit ugly. And with that thought, Demers joined a faction of physicists who believe that the pursuit of beauty as truth may be leading the field of particle physics astray.<h2>Semi-Symmetry</h2>Marcelo Gleiser, a professor of physics at Dartmouth College, began his career the same way as Demers: searching for the underlying explanations of why the universe is the way it is. But about a decade ago, he felt Demers’s same uncertainty tugging at him. “You look outside, and what you see in nature is not really perfection and symmetry,” he says. “You see patterns and formats which are not exactly perfect. Animal, tree, cloud, face: They obviously have symmetry but not perfect symmetry. It’s not really perfection, but near perfection.”
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“How contrived is too contrived? And how fine-tuned is too fine-tuned?”
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He saw the blemishes in physics, too. There is more matter than antimatter, for example. If the two were perfectly balanced and symmetric, they would have annihilated each other like the particles in Demers’ detector, and the universe would be empty—there’d be no physicists to wonder why, or to high-five each other after the discovery of a beautiful but deadly cosmic balance. “Something happened during the history of the early universe to cause this,” he says. “That got me thinking that perhaps the insistence that we have in search of perfect symmetry is not a physics idea, but a bias.”Demers’s epiphany took place as she was composing grant applications to fund her work after graduate school with the Large Hadron Collider, where the so-called “God particle” Higgs boson was discovered. Around 3,000 people worked on the ATLAS instrument team with her—attempting to discover physics that’s beyond the well-established Standard-Model. In the grant application, she also had to justify her experiment and the motivations behind it. Some of the reasons she jotted down, she realized, were purely aesthetic. It made her uncomfortable. “I personally had been sloppier about that than I should have been,” Demers says. “It struck me: You wonder, how equipped are we to be making aesthetic judgments given what we know now?” she adds. “How contrived is too contrived? And how fine-tuned is too fine-tuned?”
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<h2>Millennia of Aesthetics</h2>The human desire for a fine-tuned, aesthetically pleasing cosmos goes much further back than our ability to build particle accelerators. Plato believed the universe was made of geometry: simple, pure shapes that some deus snapped together to form a Lego-like reality. A sufficiently smart person, he reasoned, could unsnap those building blocks to reveal the fundamental forms.Early astronomers also believed that planetary orbits were perfect circles. After all, in their view, God wouldn’t have doomed the planets to orbit along an imperfect path. Because every early astronomer started with this belief, it took Johannes Kepler six years to figure out that the evidence pointed to unappealing elliptical orbits instead. But when he allowed the experimental data to lead him toward a conclusion, he discovered a truth about the universe.
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<figcaption>The spiral arms of the galaxy M74
 
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After Kepler’s data-driven discovery, Isaac Newton created the theories of gravitational force that described how and why orbits actually trace ellipses, though his ideas again reached back toward aesthetic pleasure. The same gravity that makes apples fall onto our heads also makes Earth go around the Sun. One beautiful force to control them both.In this kind of thinking, Gleiser sees a different version of the ancients’ god-driven commitment to perfect circles. And in modern scientists’ pursuit of further unification—like making the physics of atoms and subatomic particles work with the classical physics that governs the everyday world—he sees a renewed religious impulse. “The idea that there is a force that describes everything is sort of a monotheistic cultural vice that we have,” he says. “Growing up in a culture for two or three thousand years where there is a god and a central command of things—I think that’s deeply ingrained in people’s heads.” In some sense, physicists have replaced their one true, symmetrically-faced God with one true, symmetric theory.Take Einstein, who in the early 1900s said that general relativity was too beautiful to be wrong. Or physicist Paul Dirac, who in the 1960s said that the elegance of an equation outweighed the outcome of an experiment. It’s as though they had both taken to heart what poet John Keats wrote in 1820: “Beauty is truth, truth beauty.”For Demers and Gleiser, aesthetics as evidence loses its appeal when it is taken as…well…on par with evidence. For example, when the Large Hadron Collider failed to find any evidence of supersymmetry, many theorists tweaked their ideas about supersymmetry—saying, “Here’s why we don’t see any evidence”—rather than accepting that perhaps the evidence was pointing them elsewhere.
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<figcaption>The Cat's Eye Nebula
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Demers believes particle physics is in a data-rich era and that physicists should let data lead the way. As the Large Hadron Collider continues its run, it produces more and more evidence for experiments physicists like her to analyze—and then for theorists explain. “I think we may be more likely to win by the data just forcing us in a direction, as opposed to having some great idea that’s aesthetically motivated that pans out to be true,” she says. In other words, it isn’t a physicist’s job to write mathematical poetry expounding upon the platonic “universeness” of the universe. It’s their job to describe the physical reality that we interact with, that we have concrete experimental data about.And so, while beauty may be truth, the science of physics isn’t actually the pursuit of truth, nor the quest for beauty. The universe may be, at its most fundamental, as perfectly balanced as a Shakespearean sonnet. But if the data from experiments suggests not a sonnet but a modern prose poem—which is no less pretty, just different, unconventional, and more complicated—it is still physicists’ duty as scientists to analyze it.<h2>Agnostic Quests</h2>In April 2015, after a two-year break for an upgrade, the Large Hadron Collider spooled back up. This summer, the accelerator—including the ATLAS experiment that Demers is part of—will conduct its second data-taking run at these higher energies with more particle collisions. By the end of the season, it will have recorded twice as much information as it did in all of 2015. In that data, says Demers, physicists should still search for evidence of the Standard Model and supersymmetry—she’s not opposed to those theories. But they should also go on “agnostic quests,” she says, where they don’t go looking for something in particular. Instead, they should just look , and see what they find.
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<figcaption>The Veil Nebula is the remains of a massive star that exploded 8,000 years ago.
 
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But some physicists may be reluctant to give up their beautiful theories, even if the data dictates they should. For example, while the Large Hadron Collider has so far failed to show evidence of supersymmetry, many have essentially said that the collision wasn’t powerful enough or that some small modifications are all that’s needed to fit the theory they love with the data they gathered.“Supersymmetry has been around since 1974, for 42 years, and it doesn’t really have any evidence that it’s there. But people really bet their careers on this,” Gleiser explains. “Many physicists have spent 40 years working on this, which is basically their whole professional life.”That may change in in ten years or so, he says, when further advances to the LHC could force the hangers-on to let go if the data they need doesn’t materialize. “If we don’t find evidence, people who still stick to it after that are doing it as a philosophical practice,” he says.Of course, it’s certainly possible that the answers to life, the universe, and everything will be elegant. To physicists like Demers and Gleiser, that’s not the problem: The problem is the a priori assumption that it is so. And if the foundational principles of the universe turn out to be ugly or tedious, perhaps we can find the beauty beneath the mess.Editor’s note: For another perspective on beauty in physics, read “ <a href="http://www.pbs.org/wgbh/nova/next/physics/in-100-years/">How Physics Will Change—and Change the World—in 100 Years</a> .
Image credits: NASA/ESA/HEIC/The Hubble Heritage Team (STScI/AURA), NASA/STScI/AURA, NASA/ESA/Hubble Heritage Team
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Physicists often revel in the elegance of their equations, but some think it’s gone too far.

Sarah Scoles

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