How actually thinking about something for a moment can reveal its utter implausibility.
As many people get most of their information from a screen, it’s not surprising that a lot of folk are seduced by ideas that seem plausible (because we’ve seen them on a TV show or in a movie) yet are to all intents and purposes totally impossible. While we’d all like to boogie around the galaxy as if it were merely a more colorful road trip, the reality is that nature has some hard and fast rules.
That’s why there will never be a perpetual motion machine, or anti-gravity chewing gum. It’s also why humankind is highly unlikely ever to colonize space. The physiological impact is simply overwhelming, and there’s zero need for us to be up there when robots can do the job far better, for far longer, for far less engineering hassle, and for far less money, than we ever could.
And it’s also why stock favorites such as the Dyson Sphere and the Alcubierre Drive will never be developed anywhere by any civilization, ever.
To understand why this is so, let’s review the basics.
We can begin with the Dyson Sphere. Freeman Dyson, presumably after ingesting a few too many mushrooms, came up with a thought experiment that tried to answer the question: how could a putative alien technological civilization meet its presumed enormous energy needs?
Rather than contemplate the fact that there are likely very many ways in which advanced technological civilizations could generate significant amounts of energy, and that as technology progresses the energy requirements diminish due to improved efficiencies, Dyson decided to extrapolate from his own situation decades ago when everyone was worrying about Peak Oil. Which is like a Neolithic intellectual assuming that an advanced technological civilization would naturally start very big fires, perhaps consuming entire forests, in order to heat its advanced caves and wooden huts.
Dyson proposed encircling a sun with an enormous sphere, the inside of which would be irradiated by the sun and therefore capture a significant percentage of its energy output. Lo and behold: loads of energy!
Seems simple, right? And as simplicity is always highly appealing for the human brain, a lot of people over the years have jumped up and down enthusiastically and embraced the idea without considering its inherent implausibility. In the spirit of killjoys everywhere, let’s take a look at why the Dyson Sphere is actually a very silly idea.
Let’s begin by making some heroically positive assumptions. Let’s assume that the star system in question has a huge asteroid belt that contains all the necessary elements for the construction of our Sphere. This means we won’t have to destroy multiple planets in order to obtain the requisite building materials. So an asteroid belt perhaps ten thousand times the size and density of our own would do the trick. This also means we won’t need to expend colossal amounts of energy boosting the materials out of a planetary gravity well. As our energy debt for creating even a fraction of our Sphere will be literally astronomical (think: using up a Jupiter-sized mass, at the very minimum) every little saving helps.
Let’s further assume that we won’t cause any significant perturbations by shifting all this mass. Of course we will, but let’s play pretend because otherwise this whole flimsy house of cards will collapse before we’ve even begun. And let’s assume our alien civilization has some really clever way to move all this mass so that it only needs to consume a Jupiter-sized planet to supply the power. Oh, and let’s further assume that consuming a Jupiter-sized planet (likewise by force of magic) doesn’t create huge gravitational problems for the planets remaining in the system.
Now let’s assume all our smelting and building can be done with minimal energy (we’re layering pretend on top of pretend here just in order to get started, which tells us how flimsy this Dyson idea really is). So now we’ve created the panels we need for our energy trap. Let’s assume we’re actually going to create a Dyson Pledge Ring, because a Sphere was never going to be possible even with our massively generous game of Let’s Pretend. But maybe, just maybe, our game can at least result in a ring around the star to capture a still-significant portion of its solar radiation.
Our alien civilization clearly doesn’t have to worry about climate change, because the amount of solar emissions being blocked by our Dyson Pledge Ring will cool their planet by a global average of at least 20 Celsius and usher in a catastrophic Ice Age (or Methane Age, or whatever they have on their hypothetical planet that’s liquid enough to permit organic molecules to bump into each other and begin the long process of forming life). Admittedly this catastrophic Ice Age will be nothing compared to the complete extinction of all life in the system were a full Sphere to be attempted, but still: covering their entire planet with a blanket of ice many kilometers thick may not be everyone’s cup of brewed methane.
Our assumption here is that our alien world orbits a red dwarf as 80% of all suns are of this type. It further assumes our alien world was capable of giving rise to life, which means some sort of liquid on its surface or just below an ice layer. The math changes if we make less favorable assumptions, but it never gets any better than this.
At a pinch, the desperate sci-fi enthusiast may hope that our intelligent technological alien civilization has decided to wreck a nearby solar system instead of inflicting all this misery on their own system. In which case: how is all that lovely power going to be transmitted to the home world? We’ve just created a technological problem that will absorb an enormous amount of additional energy. It’s really starting to look like we need so much energy in our game of Let’s Pretend that the resulting Dyson Ring may not be worth the effort.
All in all, when we pause to think through just a few of the most obvious problems with a Dyson Sphere, it becomes starkly evident that any alien technological civilization capable of addressing the enormous problems it would pose would already have the means not to need a Dyson Anything in the first place.
Now let’s move on to the ever-popular Alcubierre Drive.
Why do we need one in the first place? Well, the universe has this really annoying problem built into it: nothing can travel faster than the speed of light, which is approximately 300,000 kilometers per second.
That means if we want to go from our solar system to the nearest star Alpha Centauri 4.3 lightyears away, it would take us four years and nearly four months to get there. That is, it would if we could attain lightspeed, which we can’t do because only massless particles can travel at the speed of light. Our very best future tech perhaps could achieve 20% of light speed a few hundred years from now. Which turns our journey into one lasting a minimum of twenty years. This isn’t looking particularly hopeful. And frankly we couldn’t even get close to that speed because the power required would be enormous, and the more power we need the more mass we need to generate it, and the more massive our craft the more power we’d need, and so on in a continuous self-defeating loop of simple physical impossibility.
Hence the appeal of the Alcubierre Drive, which basically says, “Hey, let’s not try to move through space. Let’s warp space around us!” The universe in total can expand faster than the speed of light, even though each little bit of the universe is expanding only relatively slowly. That’s why we live in a light cone, beyond which the universe doesn’t exist for us as nothing that happens outside the light cone can ever affect us (even gravity moves at the speed of light). So the Alcubierre concept basically avoids the limitation of the speed of light by aiming to warp spacetime so as to achieve an overall velocity that, to any outside observer, is greater than 300,000 kps.
Thanks to General Relativity we know that all mass warps spacetime to some extent. The more mass, the more warping. Thus Sagittarius A*, the supermassive black hole at the center of our galaxy, warps spacetime far more than our sun does. The Alcubierre Drive uses energy (because E = mc²) instead of mass to achieve the same warping, though the details of how this would be done amount to handwaving and are likely not physically possible. But we’re playing Let’s Pretend here.
Now the big question is: how much energy would we need to warp spacetime enough to get from here to Alpha Centauri? Let’s assume our spacecraft is very, very small and therefore the spacetime distortion we require is the smallest possible. Let’s also pretend we know how to stop the craft and its occupants from being crushed into a free quark/gluon plasma by the enormous forces necessary to do all the warping. And now let’s pretend we can somehow accommodate at least a Jupiter’s worth of mass inside our tiny craft and at the same time magically avoid having to warp spacetime enough to contain all this mass. Because if we don’t play this Let’s Pretend game, we’re back to the problem we had before, which is: the more energy we need, the more mass we have to contain and the more mass we have to contain, the more energy we need.
So here we are with our magical mass-free mass as an energy source and our magical spaceship that can somehow withstand the enormous forces we are going to create (even though we have zero idea how we’re going to create them).
Now we run into a more serious problem: Bekenstein-Hawking radiation. Even empty space is full of potential energy, with tiny particles and anti-particles popping in and out of existence at the Planck scale. In empty space these particles annihilate each other almost instantaneously but right at the edge of the event horizon of a black hole, one half of the particle-antiparticle pair can be sucked into the black hole while the other radiates away into space. This is how black holes eventually lose mass and evaporate. The same phenomenon would occur with our Alcubierre Drive.
Only there’s a very substantial problem: the smaller the event horizon, the more intense the effect. This means that while the supermassive black hole at the center of our galaxy will take 10¹¹ years to disappear, our little spacecraft with its very small event horizon will be losing mass-energy at a significant rate. In other words, not only do we have all the problems we’ve elucidated so far but we have an even worse problem: our space boat is leaking. So we’ll need an even greater amount of mass-energy because our method of trying to get from A to B is intrinsically self-evaporating.
And these are just a few of the many problems inherent in the notion of warping spacetime in order to avoid the lightspeed limit.
Why does all this matter? Surely sci-fi is harmless entertainment for young people and it doesn’t matter if the science is in fact merely fiction?
Yes and no. At its best, sci-fi is a way to reframe our own experiences so that we can see things about ourselves we might otherwise miss. The science fiction of Doris Lessing is a good example, shining a light on gender and cooperation issues that only today are we beginning to appreciate more fully. Asimov’s short story about a future in which everyone has their own planet and thus can’t cope with real physical proximity seems tailor-made for our own virtual age in which young people text and share videoclips but can’t make eye contact with one another.
On the other side of the sci-fi spectrum is what we can call Cowboys In Space. Here there’s little or no examination of important themes but merely a standard Hollywood action trope wrapped up in tinfoil hats and shiny spaceships. These tales ignore physics and physiology because it’s really just the same old Western with quasi-scientific trappings. The problem with this intellectual pablum is that many people don’t understand enough of reality to see that what they’re being shown cannot ever happen.
So they grow up and, if they’re lucky enough to be able to gull enough foolish venture capitalists, they start talking about building billionaire panic rooms on Mars. Or they write articles about how the human race will be “saved from extinction” by rushing off to colonize the stars (or rather, the planets around the stars). Meanwhile the only environment for which we’re actually adapted is literally burning and we’re doing nothing to stop it.
This would seem to be a very non-intelligent approach to our very real and very urgent problems.
So perhaps if we spent less time fantasizing about impossible things and spent a little more time looking for ways to mitigate the enormous harms we’re inflicting on our home planet, we’d have a more suitable channel into which we can pour our enthusiasms and energies and imaginations.
Because there’s nothing “out there” for us. It’s all right here, right now, and we’re shitting all over it.