Not long after the turn of the millennium, my wife, Kathy, and I were sitting in a McDonald's restaurant eating our Big Macs and looking at the world outside the window. We could see automobile traffic rolling by on an asphalt roadway, wooden and metal poles with power and telephone wires strung from one to the next, brick and wooden and concrete buildings lining the streets, people wearing jeans and T-shirts trudging along on concrete sidewalks, and the occasional bus or truck spewing clouds of black smoke as they accelerated from stoplights. The predominant color nearly everywhere was gray.

That was the moment when it truly hit me that we were now living in the 21st Century. And nothing had changed.

Science fiction promised us air cars, jet packs, even teleportation booths! It promised us doors that dilated, sidewalks that slid, buildings that blossomed! And things were supposed to be colorful, made of plastic and glass and chrome-plated metal. And they were supposed to be clean. Concrete? Wheels? Gasoline? Smoke? Overhead wires? No way. Power would be beamed from atomic generators to any gadget that needed it, from ground level all the way up to 30,000 feet, which would be the penthouse apartment in an average apartment building.

What the bleep happened to the future?

First let's dispel the notion that science fiction is supposed to predict the future. Aside from waterbeds and...and...well, aside from waterbeds, we've done a pretty poor job at that. If science fiction has a purpose other than entertainment, it's probably to inspire the future, by writing about how things could be if we did this or that. A secondary purpose is to prevent the future, by writing about how things can go wrong if we continue down our current path. But the "golden age" of science fiction,¹ from the 1930s into the 1950s (some include the 1960s), was filled with stories about a future with flying cars and limitless energy and weather control and so on, so much so that we began to think that was what the future would look like.

Why didn't it happen that way?

Some of that stuff was simply impossible. A six-mile-high apartment building would have to be half a mile wide to withstand the stress of high-altitude winds, and even then it would have to be made of improbably strong material. Beamed power is so wasteful that even a nuclear power plant couldn't keep up with the losses (never mind the health hazards of that much radiation zapping around). Carbon fiber is an amazing building material, but concrete is still far cheaper.

And air cars are ridiculously impractical.

Imagine what it would really be like if everybody could zip directly from point A to point B in three dimensions. Computer technology (which, by the way, we failed miserably to predict) could probably keep us from crashing into one another, but the air would be filled with flying SUVs. They would be going right over your house and converging on popular shopping malls, restaurants, and theaters like bats entering a cave at dawn. With their windows open. With air-sick kids inside. The moment flying cars become a thing, I'm investing heavily in umbrellas and yard canopies.

Of course we could regulate where they could fly, essentially making roadways in the sky. Which would negate the freedom we expect when we think of flying cars. You think you're frustrated now when you get behind a creeping granny on a packed expressway? Imagine the frustration when you could fly right over them, but aren't legally allowed to.

But there's an even more basic reason why air cars haven't happened yet, and may very well never happen. Flying is insanely more energy-intensive than rolling.

A car rests on wheels, which rest on the ground. The Earth pushes upward on the wheels and keeps them from sinking in, with absolutely no energy expenditure on the part of the car. In the air, there's nothing like that. Without energy keeping it up, the car will sink through the air, and do so at a rapid clip. Wings aren't magical devices; they simply push downward on the air and keep the aircraft aloft as long as there's enough energy in the form of forward motion to do so.

You can use really big wings and slow down that motion until updrafts are strong enough to keep your car aloft. That's how sailplanes work. But sailplanes aren't flying cars. Moreover, they're dependent on weather, terrain, and pilot skill, and you'd be hard pressed to take off in one from a shopping mall parking lot.

Besides, who wants a flying car with wings? We want something like in Blade Runner. We want it to lift off vertically from our landing pads, quickly gain altitude, then smoothly transition into forward motion. Fast forward motion.

The closest thing I've seen to that is a car with ducted fans that point downward for takeoff, then tilt to provide forward thrust once the car is in the air. The fans have to spin really fast and the propellers have to move a lot of air in order to lift not just their own weight, but the weight of the car, its pilot, three kids, their gym bags, and a load of groceries. The prototypes I've seen sport engines that look and sound alarmingly like exposed blender blades. I don't know about you, but I don't think I want one in my neighborhood, much less in my garage.

Jet engines are little better. They're basically just better-enclosed propeller systems with extra thrust from their pressurized exhaust. You've heard what they sound like on takeoff. Do you want everybody in your neighborhood making that kind of racket every morning on their way to work?

Don't even get me started on helicopter blades.

How about maglev? Magnetic fields lift high-speed trains...but only a few centimeters off the tracks. And you definitely need tracks. Unlike rockets, magnets do need something to push against, and Earth's magnetic field is far too weak to support anything denser than a magnetized air gel (if such a thing even exists; I just made that up).

How about rockets? Spacecraft take off and land on rockets, now that SpaceEx has figured out how to do the landing part. (Talk about a technology inspired by science fiction!) Since cars don't need to go all the way into orbit, wouldn't they be a lot easier to propel with the same technology?

In a word: No. Rockets are hugely inefficient. They gulp fuel like a tank rupture, are difficult to keep running for longer than a few minutes at a time, and burn themselves up in short order. One of the chief problems with private aviation as it exists today is the inordinate amount of time aircraft owners need to spend on maintenance, because you don't want to take off in an airplane that might fail on its way to your destination. Rocket maintenance is even worse. You'd need a mechanic on duty 24/7.

And then there's the need for a blast pit in every back yard, and the lack thereof in any of the national forests you'd undoubtedly set on fire if you took your air car on a camp trip.

But I confess I'd love to watch two frenzied holiday shoppers fighting over a parking space at the shopping mall with rocket-powered air cars.

What we need is a better way to lift something into the air. Cavorite would do nicely, but alas, H. G. Wells forgot to write down the formula. More to the point, since gravity is not a force but a warpage of space, blocking gravity is theoretically impossible anyway. (There's a reason why they named the anti-gravity mineral in Avatar "unobtainium.")

But as I pointed out in my column on space drives a few months ago, warping space is actually possible. Planets and stars and neutron stars and black holes do it all the time, and stuff falls into them all the time. If we were to make a pucker in space right above our vehicle, the increased gravity gradient would pull the car into the pucker. And if the pucker generator was in the car, the pucker would lift upward with the car, which would continue to fall upward into the rising pucker. Such a gadget would revolutionize just about everything, but would unfortunately be advertized as "the better pucker upper."

There's just one little problem with the "pucker-up drive." To generate one gravity of pull say ten feet overhead would take about, oh, a bazillion terawatts of energy. More than the energy usage of the entire world today.

Remember last issue's column on batteries? Imagine the battery that could power that.

Okay, so air cars are ridiculously impractical. How about all that other stuff we were supposed to get in the 21st Century? Sliding sidewalks, dilating doors, clothing with fins. Why didn't any of that happen?

I see several reasons. One is that slidewalks are grossly inefficient, just like flying cars. You have to keep the mass of the entire walkway moving, and even with nearly frictionless bearings or magnetic levitation, that's still going to take a lot of energy. Dilating doors are sexy, but they're a trip hazard and a clonk-your-head hazard. Clothing with fins would be hard to launder, and if you were wearing a finned shirt it would be hard to put on a jacket when you got cold. And so on.

But there's a more insidious reason, one that I think is ultimately much more responsible for why the 21st century is still filled with concrete and overhead wires and internal combustion engines.

Remember when I said that one of science fiction's jobs, if it has any, is probably to prevent the future rather than to predict it? Since the 1960s, that has become its main job. Perhaps its only job. Cautionary tales abound nowadays, and it's damned hard to find an upbeat, optimistic story about the future. Magazine editors (including our own) complain about that all the time. They can't get enough positive stories anymore.

Okay, I get that we live in troubled times. 2001, the second year of the new millennium, saw terrorism rear its ugly head to a degree few of us even thought possible. America predictably overreacted and we've been at war ever since. Our reliance on fossil fuels and our relentless rise in population have conspired to raise the global temperature enough to threaten life as we know it. The very nature of scientific inquiry is under attack from people who don't want to know what science is discovering. Politics has become so polarized there seems no middle ground anymore. And so on. It's truly grim out there.

You think this is any different from any other time? In the 1930s, we were still clawing our way out of the Great Depression. In the 1940s we were fighting World War II. The 1950s saw the Cold War and nuclear proliferation. Remember duck-and-cover drills? Yet the science fiction of those days was generally upbeat. We looked ahead to a future that would be happier than the era we lived in.

There was a time when science fiction writers told stories about bright, bold, exciting futures with fanciful technology and utopian societies. Not so much anymore. Nowadays we write stories about what would happen if we were to continue down our current path, and we make those stories grim enough to deter travel down that path. Yet nobody offered a better path. For lack of inspiration we did continue down our current path, and here we are.

Air cars and slidewalks and dilating doors may not be practical, but certainly we can do better than this. It just takes some imagination, and the foresight to write about it.

Time, says I, for some upbeat stories again.

¹  Some say the golden age of science fiction is twelve.
 

Jerry Oltion has been a science nut since he was old enough to spell "curious." He has written science fiction almost as long, and has done astronomy somewhat less. He writes a regular column on amateur telescope making for Sky & Telescope magazine, and spends many, many nights a year out under the stars.