1. Does humanity have a future beyond Earth?

“I think it’s a dangerous delusion to envisage mass emigration from Earth. There’s nowhere else in the solar system that’s as comfortable as even the top of Everest or the South Pole. We must address the world’s problems here. Nevertheless, I’d guess that by the next century, there will be groups of privately funded adventurers living on Mars and thereafter perhaps elsewhere in the solar system. We should surely wish these pioneer settlers good luck in using all the cyborg techniques and biotech to adapt to alien environments. Within a few centuries they will have become a new species: the posthuman era will have begun. Travel beyond the solar system is an enterprise for posthumans—organic or inorganic.”

—Martin Rees, British cosmologist and astrophysicist

2. When and where do you think we will find extraterrestrial life?

“If there is abundant microbial life on Mars, I suspect that we will find it within 20 years—if it is enough like our form of life. If an alien life-form differs much from what we have here on Earth, it is going to be difficult to detect. It’s also possible that any surviving Martian microbes are rare and located in places that are difficult for a robotic lander to reach. Jupiter’s moon Europa and Saturn’s moon Titan are more compelling places. Europa is a water world where more complex forms of life may have evolved. And Titan is probably the most interesting place in the solar system to look for life. It is rich in organic molecules but very cold and has no liquid water; if life exists on Titan, it will be very different from life on Earth.”

—Carol E. Cleland, philosophy professor and co-investigator in the Center for Astrobiology at the University of Colorado Boulder

3. Will we ever understand the nature of consciousness?

“Some philosophers, mystics and other confabulatores nocturne pontificate about the impossibility of ever understanding the true nature of consciousness, of subjectivity. Yet there is little rationale for buying into such defeatist talk and every reason to look forward to the day, not that far off, when science will come to a naturalized, quantitative and predictive understanding of consciousness and its place in the universe.”

—Christof Koch, president and CSO at the Allen Institute for Brain Science; member of the Scientific American Board of Advisers

4. Will the entire world one day have adequate health care?

“The global community has made tremendous progress toward health equity over the past 25 years, but these advances have not reached the world’s most remote communities. Deep in the rain forest, where people are cut off from transportation and cellular networks, mortality is the highest, access to health care is the most limited and quality of care is the worst. The World Health Organization estimates that one billion people go their entire lives without seeing a health worker because of distance. Health workers recruited directly from the communities they serve can bridge the gap. They can even fight epidemics such as Ebola and maintain access to primary care when health facilities are forced to shut their doors. My organization, Last Mile Health, now deploys more than 300 health workers in 300 communities across nine districts in partnership with the government of Liberia. But we can’t do this work alone. If the global community is serious about ensuring access to health care for all, it must invest in health workers who can reach the most remote communities.”

—Raj Panjabi, co-founder and chief executive at Last Mile Health and instructor at Harvard Medical School

5. Will brain science change criminal law?

“In all likelihood, the brain is a causal machine, in the sense that it goes from state to state as a function of antecedent conditions. The implications of this for criminal law are absolutely nil. For one thing, all mammals and birds have circuitry for self-control, which is modified through reinforcement learning (being rewarded for making good choices), especially in a social context. Criminal law is also about public safety and welfare. Even if we could identify circuitry unique to serial child rapists, for example, they could not just be allowed to go free, because they would be apt to repeat. Were we to conclude, regarding, say, Boston priest John Geoghan, who molested some 130 children, ‘It’s not his fault he has that brain, so let him go home,’ the result would undoubtedly be vigilante justice. And when rough justice takes the place of a criminal justice system rooted in years of making fair-minded law, things get very ugly very quickly.”

—Patricia Churchland, professor of philosophy and neuroscience at the University of California, San Diego

6. What is the chance Homo sapiens will survive for the next 500 years?

“I would say that the odds are good for our survival. Even the big threats—nuclear warfare or an ecological catastrophe, perhaps following from climate change—aren’t existential in the sense that they would wipe us out entirely. And the current bugaboo, in which our electronic progeny exceed us and decide they can live without us, can be avoided by unplugging them.”

—Carlton Caves, Distinguished Professor in physics and astronomy at the University of New Mexico

7. Are we any closer to preventing nuclear holocaust?

“Since 9/11 the U.S. has had a major policy focus on reducing the danger of nuclear terrorism by increasing the security of highly enriched uranium and plutonium and removing them from as many locations as possible. A nuclear terrorist event could kill 100,000 people. Three decades after the end of the cold war, however, the larger danger of a nuclear holocaust involving thousands of nuclear explosions and tens to hundreds of millions of immediate deaths still persists in the U.S.–Russia nuclear confrontation.

Remembering Pearl Harbor, the U.S. has postured its nuclear forces for the possibility of a bolt-out-of-the-blue first strike in which the Soviet Union would try to destroy all the U.S. forces that were targetable. We don’t expect such an attack today, but each side still keeps intercontinental and submarine-launched ballistic missiles carrying about 1,000 warheads in a launch-on-warning posture. Because the flight time of a ballistic missile is only 15 to 30 minutes, decisions that could result in hundreds of millions of deaths would have to be made within minutes. This creates a significant possibility of an accidental nuclear war or even hackers causing launches.

The U.S. does not need this posture to maintain deterrence, because it has about 800 warheads on untargetable submarines at sea at any time. If there is a nuclear war, however, U.S. Strategic Command and Russia’s Strategic Missile Forces want to be able to use their vulnerable land-based missiles before they can be destroyed. So the cold war may be over, but the Doomsday Machine that came out of the confrontation with the Soviets is still with us—and on a hair trigger.”

—Frank von Hippel, emeritus professor at the Woodrow Wilson School of Public and International Affairs at Princeton University and co-founder of Princeton’s Program on Science and Global Security

8. Will sex become obsolescent?

“No, but having sex to conceive babies is likely to become at least much less common. In 20 to 40 years we’ll be able to derive eggs and sperm from stem cells, probably the parents’ skin cells. This will allow easy preimplantation genetic diagnosis on a large number of embryos—or easy genome modification for those who want edited embryos instead of just selected ones.”

—Henry Greely, director of the Center for Law and the Biosciences at Stanford University

9. Could we one day replace all of the tissues in the human body through engineering?

“In 1995 Joseph Vacanti and I wrote for this magazine about advances in artificial pancreas technology, plastic-based tissues such as artificial skin and electronics that might permit blind people to see [see ‘Artificial Organs,’ by Robert Langer and Joseph P. Vacanti; Scientific American, September 1995]. All of these are coming to pass, either as real products or in clinical trials. Over the next few centuries it is quite possible that nearly every tissue in the body may be able to be replaced by such approaches. Creating or regenerating tissues such as those found in the brain, which is extremely complex and poorly understood, will take an enormous amount of research. The hope is, however, that research in this area will happen quickly enough to help with brain diseases such as Parkinson’s and Alzheimer’s.”

—Robert Langer, David H. Koch Institute Professor at the Massachusetts Institute of Technology

10. Can we avoid a “sixth extinction”?

“It can be slowed, then halted, if we take quick action. The greatest cause of species extinction is loss of habitat. That is why I’ve stressed an assembled global reserve occupying half the land and half the sea, as necessary, and in my book Half-Earth, I show how it can be done. With this initiative (and the development of a far better species-level ecosystem science than the one we have now), it will also be necessary to discover and characterize the 10 million or so species estimated to remain; we’ve only found and named two million to date. Overall, an extension of environmental science to include the living world should be, and I believe will be, a major initiative of science during the remainder of this century.”

—Edward O. Wilson, University Research Professor emeritus at Harvard University

11. Can we feed the planet without destroying it?

“Yes. Here’s what we need to do: reduce crop waste, consumer waste and meat consumption; integrate appropriate seed technologies and management practices; engage consumers about the challenges farmers face in both the developed and the developing world; increase public funding for agricultural research and development; and focus on advancing the socioeconomic and environmental aspects of farming that characterize sustainable agriculture.”

—Pamela Ronald, professor in the Genome Center and the department of plant pathology at the University of California, Davis*

12. Will we ever colonize outer space?

“That depends on the definition of ‘colonize.’ If landing robots qualifies, then we’ve already done it. If it means sending microbes from Earth and having them persist and maybe grow, then, unfortunately, it’s not unlikely that we’ve done that as well—possibly on Mars with the Phoenix spacecraft and almost certainly inside the Curiosity rover, which carries a heat source and was not fully baked the way Viking had been.

If it means having humans live elsewhere for a longer period of time, but not reproduce, then that’s something that might happen within the next 50 years or so. (Even some limited degree of reproduction might be feasible, recognizing that primates will be primates.) But if the idea is to construct a self-sustaining environment where humans can persist indefinitely with only modest help from Earth—the working definition of a ‘colony,’ according to the various European colonies outside of Europe—then I’d say this is very far in the future, if it’s possible at all. We currently have a very inadequate understanding of how to build closed ecosystems that are robust to perturbation by introduced organisms or nonbiological events (Biosphere 2, for example), and I suspect that the contained ecosystem problem will turn out to be much more challenging than the vast majority of space colonization advocates realize. There are a wide range of technical problems to solve, another being air handling. We haven’t bothered to colonize areas underwater on Earth yet. It’s far more challenging to colonize a place where there’s hardly any atmosphere at all.”

—Catharine A. Conley, NASA planetary protection officer

13. Will we discover a twin Earth?

“My money’s on yes. We’ve found that planets around other stars are far more abundant and diverse than scientists imagined just a couple of decades ago. And we’ve also found that the crucial ingredient for life on this planet—water—is common in space. I’d say nature seems to have stacked the deck in favor of a wide range of planets, including Earth-like planets. We just have to look for them.”

—Aki Roberge, research astrophysicist focusing on exoplanets at NASA Goddard Space Flight Center

14. Will there ever be a cure for Alzheimer’s?

“I am not sure if there will be a cure, per se, but I am very hopeful that there will be a successful disease-modifying therapy for Alzheimer’s disease within the next decade. We have now started prevention trials that are testing biological interventions even before people show clinical symptoms of the disease. And we don’t have to cure Alzheimer’s—we just need to delay dementia by five to 10 years. Estimates show that a five-year delay in the terrible and expensive dementia stage of the disease would reduce Medicare dementia costs by nearly 50 percent. Most important, that would mean that many older people could die while out ballroom dancing rather than in nursing homes.”

—Reisa Sperling, professor of neurology at Harvard Medical School and director of the Center for Alzheimer Research and Treatment

15. Will we use wearable technologies to detect our emotions?

“Emotions involve biochemical and electrical signals that reach every organ in our bodies—allowing, for example, stress to impact our physical and mental health. Wearable technologies let us quantify the patterns in these signals over long periods of time. In the coming decade wearables will enable the equivalent of personalized weather forecasts for our health: 80 percent increased probability in health and happiness for you next week, based on your recent stress/sleep/social-emotional activities. Unlike with weather, however, smart wearables can also identify patterns we might choose to change to reduce unwanted ‘storm’ events: Increase sleep to greater than or equal to nine hours per night and maintain current low-moderate stress, for a 60 percent reduced likelihood of seizure in the next four days. Over the next 20 years, wearables, and analytics derived from them, can dramatically reduce psychiatric and neurological disease.”

—Rosalind Picard, founder and director of the Affective Computing research group at the M.I.T. Media Lab

16. Will we ever figure out what dark matter is?

“Whether we can determine what dark matter is depends on what it turns out to be. Some forms of dark matter allow detection through small interactions with ordinary matter that have so far evaded detection. Others might be detectable through their influence on structures such as galaxies. I’m hopeful we will learn more through experiments or observations. But it’s not guaranteed.”

—Lisa Randall, Frank B. Baird, Jr., professor of science in theoretical physics and cosmology at Harvard University

17. Will we get control of intractable brain diseases like schizophrenia or autism?

“Diseases like autism and schizophrenia remain elusive because neuroscience hasn’t found a structural problem to fix. Some interpret this to mean future answers lie purely in biochemistry, not neural circuits. Others argue the key is for the neuroscientist to start to think in terms of overall brain architecture—not specific neural failures. Still, when thinking about the future, I am reminded of the Nobelist Charles Townes’s remark that the wonderful thing about a new idea is you don’t know about it.”

—Michael Gazzaniga, director of the SAGE Center for the Study of the Mind at the University of California, Santa Barbara

18. Will technology eliminate the need for animal testing in drug development?

“If human organs on chips can be shown to be robust and consistently recapitulate complex human organ physiology and disease phenotypes in unrelated laboratories around the world, as suggested by early proof-of-concept studies, then we will see them progressively replace one animal model at a time. That will eventually lead to significant reductions in use of animal testing. Importantly, these devices also will open up new approaches to drug development not possible with animal models today, such as personalized medicines and development of therapeutics for specific genetic subpopulations using chips created using cells from particular patients.”

—Donald E. Ingber, founding director, Wyss Institute for Biologically Inspired Engineering at Harvard University

19. Will gender equality be achieved in the sciences?

“Gender equality can be achieved, but we can’t just sit back and wait for it to happen. We need to ‘fix the numbers’ by recruiting more women into science and technology. We need to fix the institutions by implementing dual-career hiring, family-friendly policies, and new visions of what it means to be a leader. And, most importantly, we need to fix the knowledge by harnessing the creative power of gender analysis for discovery and innovation.”

—Londa Schiebinger, John L. Hinds Professor of History of Science at Stanford University

20. Do you think we will one day be able to predict natural disasters such as earthquakes with warning times of days or hours?

“Some natural disasters are easier to see coming than others. Hurricanes approach over days, volcanoes often build up to an eruption over days to hours, tornadoes strike within a few minutes. Earthquakes are perhaps the greatest challenge. What we know about the physics of earthquakes suggests that we will not be able to predict earthquakes days in advance. But what we can do is predict the damaging ground shaking just before it arrives and provide seconds to minutes of warning. Not enough time to get out of town, but enough time to get to a safe location.”

—Richard M. Allen, director, Berkeley Seismological Laboratory, University of California, Berkeley

*Editor's Note (8/22/16): This biographical note was edited after posting to correct an error in Ronald's title.