One day, sitting around with a group of undergraduate physics students, I listened as one made the bold statement: “If it can be imagined, it can be done.” The others nodded in agreement. It sounded like wisdom. It took me all of two seconds to violate this dictum as I imagined myself jumping straight up to the Moon. I may have asked if the student really thought what he said was true, but resisted the impulse to turn it into an impromptu teaching moment. Instead, I wondered how pervasive this attitude was among physics students and faculty. So I put together a survey and in this post report what I found. The overriding theme: experts say don’t count on a Star Trek future. Ever.

The Survey

First, we’ll take a look at the questions in the survey. If you want to try it for yourself before being tainted with results, I have set up a separate survey at SurveyMonkey that you are welcome to try. If you’re reading this post on Do the Math (the original source), please identify yourself as a Do the Math reader when you fill out the survey here.

Let me clarify that I do not design surveys for a living, and may have made some rookie mistakes. But hey: this is just for my own enlightenment, and to the extent that others learn from the experience: great.

Here is the introductory text that survey takers saw:

Each question has the same set of options for answers, corresponding to timescales in which you might imagine humans likely accomplish some feat. By “likely”, I mean better than 50% probability, in your mind. The “eventually” qualifier might fold in your projection on the lifespan of humans or their direct evolutionary descendants. I am most interested in functional aspects of the phenomenon, rather than clever technicalities that many of us might proffer. For instance, teleportation may have been “shown” in quantum optics experiments, but teleporting a human from San Diego to Boston stands apart from this lab trick.

For each question, choices are (and the numbers will play a role):

No Opinion likely within 50 years likely within 500 years likely within 5000 years likely to happen for humans eventually unlikely to happen for humans < 1% likely to ever happen, or impossible

Note that answers 5 and 6 qualify as pessimistic: probably not ever. Answer 4 is a non-committal “probably.” It is easy to remember answers 1, 2, and 3 as a sort of scientific notation: 5×10x years.

Okay; here is the set of twenty questions:

What do you think is the likelihood that humans can:

Have widespread personal transport that can replace the task of driving with a fully-automated piloting system (auto-pilot)? See jet-packs as practical transportation devices on a daily basis? Carry out the bulk of transportation in personal flying machines, rather than being tied to the ground in cars (what are wheels, daddy?)? Routinely teleport live human bodies respectable distances—enough to revolutionize the way we travel? Come up with a means of interstellar travel that allows round-trips to locales tens of light-years away within years or decades, without having Earth (and its people) age substantially more than the traveler—thus operating outside the normal confines imposed by sub-luminal travel and special relativity (the equivalent of warp drive in Star Trek)? Use wormholes as tools to move across vast distances? Visit the vicinity of a black hole to study it up-close? Do astrophysics by traveling to sources (outside our solar system) rather than via telescopes? Be able to create local gravity (not just magnetic boots) in a spaceship by some means other than kinematically (e.g., rotation or acceleration of spacecraft)? Have a permanent colony on the Moon, where some might live their entire (normal-length) lives? Have a permanent colony on Mars, also with whole lives spent there? Terra-form a planet (like Mars) to make it human-habitable? Power our society with fusion, opening up practically inexhaustible supplies of deuterium on the planet (forget about tritium here—imagine D–D reactions)? Create our food without growing or raising it—like the Star Trek method of “replicating” food by patterning atoms/molecules appropriately, maybe straight from the source of energy? Have robots as common entities among us that can intelligently converse with us and perform sophisticated tasks (housework, transport repair, nanny for the kids)? I’m talking about C-3PO, nothing like today’s machines. Have cloaking devices that, at the flip of a switch, can render a macroscopic device like a car, plane, or spaceship impossible—or exceedingly difficult—to see from virtually any angle? Be able to travel back in time by an amount significant enough to change actions? Communicate with intelligent alien species (extra-terrestrial), sharing technology, history, etc.? Either physically visit or be visited by an intelligent alien species? Substantially eliminate disease and block aging so that we may routinely see lives exceeding 200 years?

Who’s the Expert?

I will be using the term “expert” to distinguish the level of knowledge/experience within the physics discipline. But don’t take the term too literally. There is no such thing as an expert on warp drive or teleportation—outside of geeky fan clubs, where one might find full blueprints of imaginary spaceships. But if you sought an opinion on the possibility or likelihood of these futuristic ideas having a chance of being realized (and on what timescale), what sort of expert might you seek?

Does somebody on your street or in your building know? Ask your neighbors and find out how relevant their knowledge base is to address these questions with any credibility. Somebody working in your community’s retail services might know something. No? The big-shots at big banks? Somebody in the government? Probably the NASA folks who aren’t busy actually doing a job in the here and now would have interesting insights. But in general, I think it is natural to seek the opinion of academics with a handle on fundamental limitations and possibilities. Academic researchers are among the only group whose job description is to explore the unknown and open new frontiers. These are the dreamers of the future, and the ones with the rigorous training to sort out the possible from fantasy.

And which academic department would you visit to query about teleportation, artificial gravity, or nuclear fusion? Theater? History? Psychology? Medicine? Chemistry? Physics? Yeah—that last one. So even though the questions are somewhat diverse and out of left field, let’s conclude that academic physicists at top research universities are as qualified a pool of experts as we’re likely to find for these topics.

I invited physics faculty at a handful of top-20 schools across the U.S. (using graduate program rankings from the US News and World Report) to participate in the anonymous survey. I promised that neither they nor their institutions would be revealed. I also invited physics graduate students and physics undergraduates to contribute, so that I could track attitudes as a function of age, expertise, or selected path in life.

Graphical Results

We’ll pick apart the results in a variety of ways. First, let’s get a look at all the questions in turn.

The answers are broken out in groups of three, with titles (and question numbers) relating to the above list. Each graphic has nine panels: three questions across, and three response groups down. This arrangement makes it easier to compare left-right shifts among the three populations surveyed. Each panel contains four numbers at left: median, mean, standard deviation, and percent pessimistic (answers 5 or 6). The first three statistics do not include the few “no opinion” answers, when they exist. The median and mean values are also marked on the distribution as dashed and dotted lines, respectively.

One note on the standard deviation: with only 6 numerical options (ignoring no opinion = 0), a completely uniform distribution (same number of responses for each answer) would score a standard deviation of 1.7. The most extreme possible standard deviation is 2.5, which would happen if responses were equally divided between the most extreme answers in a pathological bimodality.

So let’s dive in with the first three. I’ll offer some comments after each group. Then we’ll look at some aggregate characterizations and reflections.

Looking at the left-hand column, the grad students have a pretty strong consensus (low standard deviation) that autopilot cars will soon be commonplace. The median for all three groups says we might expect widespread autopilot cars within 50 years. Undergrads and faculty scored virtually the same mean, around 1.5. Loosely speaking, we could turn this into an expectation around 150 years using our 5×10x rule of thumb for numbers in the 1–3 range. No grads register as pessimistic on this count, and only 2% of undergrads and 4% of faculty think that autopilot cars are unlikely to ever happen. The results offer an important indication that the respondents are capable of rendering optimistic answers on futuristic ideas (i.e., ideas not implemented anywhere in the world now). It goes downhill from here.

I like the jetpack question, because jetpacks have come to symbolize angst in my generation for toys we were promised as kids that never materialized. On the whole, all three groups tilt pessimistic on jetpacks ever being a practical mode of transportation. The scores are pretty consistent across the board, with a median of 5 (likely never happen), a mean around 4.0, and identical standard deviations. Substantial bimodality appears in the undergrads, with the mode (tallest spike) actually putting jetpacks inside of 500 years. That same answer and bimodal tendency shows up in more expert opinions as well—just not as strongly.

Personal flying cars fare better than jetpacks, but a huge difference shows up in the pessimism score. Professors don’t buy it, on the whole (albeit with a bimodal split). The median response goes from 500 years among students to “probably never” among faculty. Our first dramatic difference. As a faculty member who is also a licensed pilot, I can say that flying is a gigantic departure from driving. Unleash the population into 3D space and watch the mayhem! (I would suggest erecting a strong shield over your house.)

Beam me up! Traveling to the other side of the world takes a whole day and is such a hassle! (Just wait until fossil fuels are scarce and see what you think then.) If we could just teleport ourselves as coded energy streams (or whatever) we’d finally be liberated—unless it turned out to cost $10 million a pop… What do physicists think? We see the usual gradient, with 85% of professors saying it’s not likely to ever happen (the bulk labeling it as impossible). The median marches from 4 to 6 among the three groups. The grad distribution resembles the faculty distribution, but the undergrad distribution is much more nearly uniform.

So what about faster-than-light interstellar travel (warp)? This looks pretty similar to teleportation, with a slightly higher fraction (91%) of faculty saying it’s essentially impossible. Student opinions are regressively softer.

When it comes to using wormholes to get around, majority opinion counts this as unlikely to ever happen. It’s almost a lock among faculty, except for one individual who thinks we’ll be doing this inside of 500 years! This same outlier registered identical answers for the previous two questions. We’ll see more of him/her later.

Will we ever be able to send a probe to visit a black hole and study it up close? Three-quarters of faculty say not likely. Grads are also skeptical on balance, but undergrads have a loud “someday” response. Note the steady march of median, mean, percent pessimistic, and tightening of standard deviation as we increase expertise. This pattern asserts itself often (e.g., the previous three questions as well), and we’ll call it the expert gradient.

This question is similar to the last, but expanded to cover any astrophysical object of interest outside our solar system (another star, nebula, cluster, pulsar, etc.). Not a single undergrad wants to claim this is <1% likely, and only 10% say it is unlikely to ever happen. Meanwhile, 62% of faculty members say don’t count on it ever happening. A small spike of physics professors think 500 years is reasonable. I’m betting against these folks being astro-familiar faculty, actually. Aside from the evolution of the standard deviation, the trends follow the expert gradient.

Switching gears a bit, if we do manage space travel beyond the Earth environs (obviously not guaranteed), will we be able to walk about in a simulated gravity environment by some means other than rotating or accelerating the spacecraft? I don’t count the cheap trick of magnetic boots either, which still leave your body weightless. I’m thinking the Star Trek non-gyrating ship with gravity pointing perfectly downward on all decks, ubiquitous crawl tubes, etc. We see the normal expert gradient on strong display. The undergrads are surprisingly bullish, many expecting results in 500 years. By contrast, the grad and faculty distributions share a similar character.

What about living a life off the Earth, in a lunar colony? The mode in all three says within 500 years, while the mean says somewhat longer. at least 80% of folks in each group think this will happen some day, although very few expect it to happen inside of 50 years. Pause for a second to reflect on the fact that 50 years after the space race began, we think it will be at least another 50 before we’re living on the Moon. I’m guessing this is a radical change in attitude compared to prevailing views in the 1960’s. An interesting departure from the expert gradient shows up here: undergrads are more skeptical than grads. This reversal may be due to the termination of the U.S. human spaceflight program during a stage in life (late high school, early college) when world views are forming and fluid. Perhaps this group has been more impacted by the shutdown than grad students whose noses are buried in research.

A somewhat similar pattern shows up on the subject of a colony on Mars. A comparable number think it will happen someday, and the undergrads are again a little more circumspect than grads. The mode shifts a bit, too. For the lunar colony, <500 years was a standout modal preference. It’s much less clear for Mars, becoming especially broad for faculty.

Speaking of living on Mars, what do physicists think about the likelihood of terraforming a planet like Mars? We get the expert gradient back, although no group trips over to a pessimistic balance. Let me just say that we have not identified a viable way to fix a 100 part-per-million CO 2 problem in our own atmosphere, with all the resources of Earth available to us. Transforming another planet’s atmosphere is a one-million parts-per-million problem with virtually no available industrial resources at hand. What I’m telling you is that I’m in the skeptical camp.

Coming closer to a Do the Math topic, what is the physicists’ view of nuclear fusion? It is often jokingly said to be perpetually 50 years in the future. Did 50 years win? No! The mean, median, and mode all roughly pick out the <500 year choice: most strongly so among professors. Virtually no one said it was unlikely to ever be realized, but comparably few expect fusion to be a viable solution on the scale of decades—which I note is the relevant timescale for the great energy challenge as we seek to transition away from finite fossil fuels.

How about feeding the world with synthesized food akin to the replicated food in Star Trek? Sort of a 3-d printer for food. The expert gradient re-emerges for this one, save the standard deviation. The faculty are on the fence on the pessimism score, perched at 50%. Not much buy-in for the 50 year timeframe, when population pressures, agricultural limits, and climate-change-induced crop failure may collide to produce food shortages.

Robots, anyone? Maybe androids would be a more apt term: an intelligent “being” with whom we could converse and count on to do complex, adaptive tasks that humans today perform. A strong vote emerges for <500 years, although interestingly the undergrads are the most wary of the lot. Perhaps robots are the new jetpack: a target of angst for still being so lame.

We hit some turbulence over cloaking devices, which I find surprising. The faculty response, in particular, shows a strong bimodality, reflected also in the large standard deviation. The mode for all three says <500 years, although a 33% pessimism score among the faculty drag their median to 4 (“someday”). For me, it’s the “from virtually any angle” that’s the killer. Devices have been built that divert microwave “light” around a small object in only one direction, employing a bulky apparatus much larger then the hidden object itself to accomplish. It’s no good cloaking if the cloaking device itself is an even larger target that itself is not cloaked. A shrub moving across the lawn raises suspicion even if the motive force cannot be clearly seen. But whatever. The respondents have a soft spot that I don’t share. I’ll get back to reporting the actual responses, rather than what I think they should have said.

When it comes to time travel, it appears we all got the memo. Not gonna do it. All three groups have the mean, median, and mode pointing to “impossible.”

What about opening a line of communication with aliens. And I don’t mean dolphins. Means and medians are pretty uniform in saying “someday,” but hardly anyone appears to expect it to happen in their own lifetimes. Grads and faculty register similar levels of pessimism about it ever happening at all, but neither crossing the 50% mark.

What about an actual close encounter with an alien? First piece of advice: don’t accept any blankets. This looks like a virtual copy of the previous response about alien communications. The grad response is so similar that it’s hard to confirm any differences at all. Curiously, the undergrad mean says it’s more likely we’ll shake hands than be pen-pals: suggesting an unannounced visit. The faculty barely tip into the “unlikely ever” category on balance, with 52% expressing this sentiment.

Finally, what can we expect in terms of aging? Will we solve the problem and extend life to 200 years or more? Almost no one says “impossible.” Students are nearly identical in outlook, expecting this to be common within 500 years, but not in time for them personally. Faculty think it will be much longer than this, but 84% think it will ultimately happen. It is worth pointing out that this question is perhaps less in the domain of physics than most of the other questions.

Group Attitudes

Group-wise, a somewhat predictable trend emerges—reflected by the “expert gradient” seen in many of the individual answers.

The median answer goes from 3.4 to 3.7 to 4.0 for undergrads through faculty: a steady progression toward more guarded outlooks. Meanwhile, we see a less steady progression of the mean—more clearly separating faculty from students—but still conveying the same overall story. Note the optimistic outlier in the faculty ranks. We saw this individual stand out on the wormhole question. Examining this person’s responses, it’s all 1, 2, and 3 responses, save one 4 for time travel. Nothing is off limits to this professor, and most things deserve a timescale. This individual is clearly out of step with the cohort, and tying the most optimistic undergrad: forever young.

Expert Gradient and Biggest Dissimilarities

Most questions show the “expert trend,” wherein the median, mean, and percent pessimistic increase with level, often accompanied by decreasing standard deviation.

Notable exceptions are the autopilot, flying cars, lunar and Martian colonies, fusion, and robots. Also, the roving astrophysics, synthetic food, and cloaking show most of the characteristics of the expert gradient, while the standard deviation increases with level of expertise.

The biggest differences between faculty and grad students crop up on questions pertaining to flying cars, cloaking, and studying astrophysical objects up close. The largest graduate-undergraduate discrepancy appears for the question about artificial gravity. The largest end-to-end discrepancies (faculty to undergraduate) relate to flying cars, artificial gravity, and warp drive.

Meanwhile the jetpack and time travel questions have the most similar statistics.

Expert Opinion, Summarized

The table below is organized in rank order according to median opinion among physics faculty members. Within each group sharing the same median, the mean is used as the sorting metric. Columns are given for the mean and percentage of pessimistic responses, followed by a verbal characterization of what the median expert says in response to the question. In cases where the mean is between 1–3, a timescale conversion is offered for the mean opinion.

Topic Mean % pessim. median disposition 1. Autopilot Cars 1.4 (125 yr) 4 likely within 50 years 15. Real Robots 2.2 (800 yr) 10 likely within 500 years 13. Fusion Power 2.4 (1300 yr) 8 likely within 500 years 10. Lunar Colony 3.2 18 likely within 5000 years 16. Cloaking Devices 3.5 32 likely within 5000 years 20. 200 Year Lifetime 3.3 16 maybe within 5000 years 11. Martian Colony 3.4 22 probably eventually (>5000 yr) 12. Terraforming 4.1 40 probably eventually (> 5000 yr) 18. Alien Dialog 4.2 42 probably eventually (> 5000 yr) 19. Alien Visit 4.3 50 on the fence 2. Jetpack 4.1 64 unlikely ever 14. Synthesized Food 4.2 52 unlikely ever 8. Roving Astrophysics 4.6 64 unlikely ever 3. Flying “Cars” 3.9 60 unlikely ever 7. Visit Black Hole 5.1 74 forget about it 9. Artificial Gravity 5.3 84 forget about it 4. Teleportation 5.3 85 forget about it 5. Warp Drive 5.5 92 forget about it 6. Wormhole Travel 5.5 96 forget about it 17. Time Travel 5.7 92 forget about it

Note that ten out of twenty are in the trash bin, with an eleventh precariously perched on the rim. Meanwhile grad students put 7 ideas in the trash, and undergrads only managed to get two fully in the can, a third hung on the rim. Thus 3, 7, and 11 ideas are essentially written off in a steady progression of pessimism with level of experience.

Optimistically, one might say that we just need to wait until the young can-do generation moves into the upper ranks and then we’ll get our teleportation: kick the old fogies out. Keep this thought train going, and if we just wait for current 5-year olds to come into power, we can look forward to living in giant sand castles on the Sun (where it is never bedtime), eating ice cream for every meal, surrounded by talking animals. We only have to wait a generation or two!

But just as kittens turn into cats, starry-eyed youths get a dose of reality when they try to actually do things in life.

The other noteworthy characteristic of the table above is that only one idea out of 20 is deemed likely to happen in the next 50 years. Only two ideas make the 500 year cut, and two or three more within 5000 years. I think this is an astounding result. After all, physicists are people too, and subject to the same psychological tendencies to extrapolate as the rest of the population.

The rate of progress in the last few hundred years has felt like an exponential headlong rush into an ever-more-brilliant future. But the practitioners of physics appear not to have fallen victim to the commonly expressed notion that a person 200 years ago could never have dreamed of the technology and capabilities we would have today; therefore we ourselves cannot possibly dream of the mind-boggling advances to be made in the next 200 years. Physicists appear to be willing to bet against the more outlandish notions.

A key element here is that we know a heck of a lot more about fundamental physics now than we did 200 years ago. Undoubtedly we have much yet to learn. But the frontiers 200 years ago pertained to everyday time, length, and energy scales. Today’s frontiers are at 10−18 m scales on one end, and at cosmological scales on the other. Ultra-high energy frontiers are increasingly hard to access, requiring monster machines like the LHC at CERN. The chances that new physics will intercede at human-familiar scales are increasingly slim as the boundaries of our knowledge push out. Most technological developments of the last 50 years have been based on incremental progress in manipulation of matter, rather than on fundamental breakthroughs in physics like electromagnetism, quantum mechanics, or general relativity from roughly a century ago.

So it appears to me that the respondents to the survey were doing more than extrapolating our recent joy ride into a shiny future. My guess is that they consulted their understanding of physics—combined with a sense of practicality—to address questions of time travel, warp drive, teleportation, etc. In other words, the responses cannot easily be written off as coming from a bunch of wet blankets.

Indeed, physicists get into the game motivated by the thrill of exploration and discovery in one of the few remaining frontiers. There is no selection effect for attracting pessimistic downers. Probably the opposite, in fact. Most are fans of science fiction at some level—at least to the point of having positive feelings toward classics like Star Trek and Star Wars. Despite this, their physics-informed opinions don’t paint those genres as likely future paths for us.

Escapism Won’t Help Us

A primary motivation for my performing this survey stemmed from a sense that un-allayed optimism (“If it can be imagined, it can be done”) is detrimental to our successful navigation of the challenges foisted upon us this century. I perceive that a pervasive attitude in our society is that “we’ll solve any big problem that comes our way: we’ve got brilliant scientists working on it.” I would bet that most members of our society would put us living on the Moon and Mars within a few hundred years. I think they would be shocked to learn that the experts largely disagree.

It matters. The belief that we can escape our Earthly bounds (and problems) impairs our commitment to take positive corrective action to address problems here on Earth. When I initially wrote the piece Why Not Space, I was blown away by the certainty expressed in many comments that we would of course break free of our evolutionary nursery. Fish crawls onto land; reptile takes flight; man jumps to the stars. A compelling storyline, yet likely completely wrong. Desolation and danger cut in the wrong direction to make space a natural leap. We don’t do so well away from our eggshell-thin biosphere. Even high mountains and ocean depths pose serious challenges to human survival. If we’re destined for space, why don’t we live undersea today?. Space is orders of magnitude more difficult still, leaving aside the stiff energetic barrier to getting there in the first place.

What we have in this survey is a reality check that calls to question our most ambitious dreams, and puts a pretty distant timescale on even the more tractable problems. As we face unprecedented, parallel challenges this century (energy, growth limits, food, water, population, climate change), we should be careful to check our hubris at the door. It appears that the physicists have largely done this already.