Tag Archives: PublicPerception

Is Everything Really Astonishingly Simple?

Neil Turok gave a talk last week, entitled The Astonishing Simplicity of Everything. In it, he argued that our current understanding of physics is really quite astonishingly simple, and that recent discoveries seem to be confirming this simplicity.

For the right sort of person, this can be a very uplifting message. The audience was spellbound. But a few of my friends were pretty thoroughly annoyed, so I thought I’d dedicate a post to explaining why.

Neil’s talk built up to showing this graphic, one of the masterpieces of Perimeter’s publications department:

Looked at in this way, the laws of physics look astonishingly simple. One equation, a few terms, each handily labeled with a famous name of some (occasionally a little hazy) relevance to the symbol in question.

In a sense, the world really is that simple. There are only a few kinds of laws that govern the universe, and the concepts behind them are really, deep down, very simple concepts. Neil adroitly explained some of the concepts behind quantum mechanics in his talk (here represented by the Schrodinger, Feynman, and Planck parts of the equation), and I have a certain fondness for the Maxwell-Yang-Mills part. The other parts represent different kinds of particles, and different ways they can interact.

While there are only a few different kinds of laws, though, that doesn’t mean the existing laws are simple. That nice, elegant equation hides 25 arbitrary parameters, hidden in the Maxwell-Yang-Mills, Dirac, Kobayashi-Masakawa, and Higgs parts. It also omits the cosmological constant, which fuels the expansion of the universe. And there are problems if you try to claim that the gravity part, for example, is complete.

When Neil mentions recent discoveries, he’s referring to the LHC not seeing new supersymmetric particles, to telescopes not seeing any unusual features in the cosmic microwave background. The theories that were being tested, supersymmetry and inflation, are in many ways more complicated than the Standard Model, adding new parameters without getting rid of old ones. But I think it’s a mistake to say that if these theories are ruled out, the world is astonishingly simple. These theories are attempts to explain unlikely features of the old parameters, or unlikely features of the universe we observe. Without them, we’ve still got those unlikely, awkward, complicated bits.

Of course, Neil doesn’t think the Standard Model is all there is either, and while he’s not a fan of inflation, he does have proposals he’s worked on that explain the same observations, proposals that are also beyond the current picture. More broadly, he’s not suggesting here that the universe is just what we’ve figured out so far and no more. Rather, he’s suggesting that new proposals ought to build on the astonishing simplicity of the universe, instead of adding complexity, that we need to go back to the conceptual drawing board rather than correcting the universe with more gears and wheels.

On the one hand, that’s Perimeter’s mission statement in a nutshell. Perimeter’s independent nature means that folks here can focus on deeper conceptual modifications to the laws of physics, rather than playing with the sorts of gears and wheels that people already know how to work with.

On the other hand, a lack of new evidence doesn’t do anyone any favors. It doesn’t show the way for supersymmetry, but it doesn’t point to any of the “deep conceptual” approaches either. And so for some people, Neil’s glee at the lack of new evidence feels less like admiration for the simplicity of the cosmos and more like that one guy in a group project who sits back chuckling while everyone else fails. You can perhaps understand why some people felt resentful.

A Tale of Two CMB Measurements

While trying to decide what to blog about this week, I happened to run across this article by Matthew Francis on Ars Technica.

Apparently, researchers have managed to use Planck‘s measurement of the Cosmic Microwave Background to indirectly measure a more obscure phenomenon, the Cosmic Neutrino Background.

The Cosmic Microwave Background, or CMB is often described as the light of the Big Bang, dimmed and spread to the present day. More precisely, it’s the light released from the first time the universe became transparent. When electrons and protons joined to form the first atoms, light no longer spent all its time being absorbed and released by electrical charges, and was free to travel in a mostly-neutral universe.

This means that the CMB is less like a view of the Big Bang, and more like a screen separating us from it. Light and charged particles from before the CMB was formed will never be observable to us, because they would have been absorbed by the early universe. If we want to see beyond this screen, we need something with no electric charge.

That’s where the Cosmic Neutrino Background comes in. Much as the CMB consists of light from the first time the universe became transparent, the CNB consists of neutrinos from the first time the universe was cool enough for them to travel freely. Since this happened a bit before the universe was transparent to light, the CNB gives information about an earlier stage in the universe’s history.

Unfortunately, neutrinos are very difficult to detect, the low-energy ones left over from the CNB even more so. Rather than detecting the CNB directly, it has to be observed through its indirect effects on the CMB, and that’s exactly what these researchers did.

Now does all of this sound just a little bit familiar?

Gravitational waves are also hard to detect, hard enough that we haven’t directly detected any yet. They’re also electrically neutral, so they can also give us information from behind the screen of the CMB, letting us learn about the very early universe. And when the team at BICEP2 purported to measure these primordial gravitational waves indirectly, by measuring the CMB, the press went crazy about it.

This time, though? That Ars Technica article is the most prominent I could find. There’s nothing in major news outlets at all.

I don’t think that this is just a case of people learning from past mistakes. I also don’t think that BICEP2’s results were just that much more interesting: they were making a claim about cosmic inflation rather than just buttressing the standard Big Bang model, but (outside of certain contrarians here at Perimeter) inflation is not actually all that controversial. It really looks like hype is the main difference here, and that’s kind of sad. The difference between a big (premature) announcement that got me to write four distinct posts and an article I almost didn’t notice is just one of how the authors chose to make their work known.

Don’t Watch the Star, Watch the Crowd

I didn’t comment last week on Hawking’s proposed solution of the black hole firewall problem. The media buzz around it was a bit less rabid than the last time he weighed in on this topic, but there was still a lot more heat than light.

The impression I get from the experts is that Hawking’s proposal (this time made in collaboration with Andrew Strominger and Malcom Perry, the former of whom is famous for, among other things, figuring out how string theory can explain the entropy of black holes) resembles some earlier suggestions, with enough new elements to make it potentially interesting but potentially just confusing. It’s a development worth paying attention to for specialists, but it’s probably not the sort of long-awaited answer the media seems to be presenting it as.

This raises a question: how, as a non-specialist, are you supposed to tell the difference? Sure, you can just read blogs like mine, but I can’t report on everything.

I may have a pretty solid grounding in physics, but I know almost nothing about music. I definitely can’t tell what makes a song good. About the best I can do is see if I can dance to it, but that doesn’t seem to be a reliable indicator of quality music. Instead, my best bet is usually to watch the crowd.

Lasers may make this difficult.

Ask the star of a show if they’re doing good work, and they’re unlikely to be modest. Ask the average music fan, though, and you get a better idea. Watch music fans as a group, and you get even more information.

When a song starts playing everywhere you go, when people start pulling it out at parties and making their own imitations of it, then maybe it’s important. That might not mean it’s good, but it does mean it’s worth knowing about.

When Hawking or Strominger or Witten or anyone whose name you’ve heard of says they’ve solved the puzzle of the century, be cautious. If it really is worth your attention, chances are it won’t be the last you’ll hear about it. Other physicists will build off of it, discuss it, even spin off a new sub-field around it. If it’s worth it, you won’t have to trust what the stars of the physics world say: you’ll be able to listen to the crowd.

Journalists Are Terrible at Quasiparticles

TerribleQuasiparticleHeadlineNo, they haven’t, and no, that’s not what they found, and no, that doesn’t make sense.

Quantum field theory is how we understand particle physics. Each fundamental particle comes from a quantum field, a law of nature in its own right extending across space and time. That’s why it’s so momentous when we detect a fundamental particle, like the Higgs, for the first time, why it’s not just like discovering a new species of plant.

That’s not the only thing quantum field theory is used for, though. Quantum field theory is also enormously important in condensed matter and solid state physics, the study of properties of materials.

When studying materials, you generally don’t want to start with fundamental particles. Instead, you usually want to think about overall properties, ways the whole material can move and change overall. If you want to understand the quantum properties of these changes, you end up describing them the same way particle physicists talk about fundamental fields: you use quantum field theory.

In particle physics, particles come from vibrations in fields. In condensed matter, your fields are general properties of the material, but they can also vibrate, and these vibrations give rise to quasiparticles.

Probably the simplest examples of quasiparticles are the “holes” in semiconductors. Semiconductors are materials used to make transistors. They can be “doped” with extra slots for electrons. Electrons in the semiconductor will move around from slot to slot. When an electron moves, though, you can just as easily think about it as a “hole”, an empty slot, that “moved” backwards. As it turns out, thinking about electrons and holes independently makes understanding semiconductors a lot easier, and the same applies to other types of quasiparticles in other materials.

Unfortunately, the article I linked above is pretty impressively terrible, and communicates precisely none of that.

The problem starts in the headline:

Scientists have finally discovered massless particles, and they could revolutionise electronics

Scientists have finally discovered massless particles, eh? So we haven’t seen any massless particles before? You can’t think of even one?

After 85 years of searching, researchers have confirmed the existence of a massless particle called the Weyl fermion for the first time ever. With the unique ability to behave as both matter and anti-matter inside a crystal, this strange particle can create electrons that have no mass.

Ah, so it’s a massless fermion, I see. Well indeed, there are no known fundamental massless fermions, not since we discovered neutrinos have mass anyway. The statement that these things “create electrons” of any sort is utter nonsense, however, let alone that they create electrons that themselves have no mass.

Electrons are the backbone of today’s electronics, and while they carry charge pretty well, they also have the tendency to bounce into each other and scatter, losing energy and producing heat. But back in 1929, a German physicist called Hermann Weyl theorised that a massless fermion must exist, that could carry charge far more efficiently than regular electrons.

Ok, no. Just no.

The problem here is that this particular journalist doesn’t understand the difference between pure theory and phenomenology. Weyl didn’t theorize that a massless fermion “must exist”, nor did he say anything about their ability to carry charge. Weyl described, mathematically, how a massless fermion could behave. Weyl fermions aren’t some proposed new fundamental particle, like the Higgs boson: they’re a general type of particle. For a while, people thought that neutrinos were Weyl fermions, before it was discovered that they had mass. What we’re seeing here isn’t some ultimate experimental vindication of Weyl, it’s just an old mathematical structure that’s been duplicated in a new material.

What’s particularly cool about the discovery is that the researchers found the Weyl fermion in a synthetic crystal in the lab, unlike most other particle discoveries, such as the famous Higgs boson, which are only observed in the aftermath of particle collisions. This means that the research is easily reproducible, and scientists will be able to immediately begin figuring out how to use the Weyl fermion in electronics.

Arrgh!

Fundamental particles from particle physics, like the Higgs boson, and quasiparticles, like this particular Weyl fermion, are completely different things! Comparing them like this, as if this is some new efficient trick that could have been used to discover the Higgs, just needlessly confuses people.

Weyl fermions are what’s known as quasiparticles, which means they can only exist in a solid such as a crystal, and not as standalone particles. But further research will help scientists work out just how useful they could be. “The physics of the Weyl fermion are so strange, there could be many things that arise from this particle that we’re just not capable of imagining now,” said Hasan.

In the very last paragraph, the author finally mentions quasiparticles. There’s no mention of the fact that they’re more like waves in the material than like fundamental particles, though. From this description, it makes it sound like they’re just particles that happen to chill inside crystals, like they’re agoraphobic or something.

What the scientists involved here actually discovered is probably quite interesting. They’ve discovered a new sort of ripple in the material they studied. The ripple can carry charge, and because it can behave like a massless particle it can carry charge much faster than electrons can. (To get a basic idea as to how this works, think about waves in the ocean. You can have a wave that goes much faster than the ocean’s current. As the wave travels, no actual water molecules travel from one side to the other. Instead, it is the motion that travels, the energy pushing the wave up and down being transferred along.)

There’s no reason to compare this to particle physics, to make it sound like another Higgs boson. This sort of thing dilutes the excitement of actual particle discoveries, perpetuating the misconception of particles as just more species to find and catalog. Furthermore, it’s just completely unnecessary: condensed matter is a very exciting field, one that the majority of physicists work on. It doesn’t need to ride on the coat-tails of particle physics rhetoric in order to capture peoples’ attention. I’ve seen journalists do this kind of thing before, comparing new quasiparticles and composite particles with fundamental particles like the Higgs, and every time I cringe. Don’t you have any respect for the subject you’re writing about?

Outreach as the End Product of Science

Sabine Hossenfelder recently wrote a blog post about physics outreach. In it, she identifies two goals: inspiration, and education.

Inspiration outreach is all about making science seem cool. It’s the IFLScience side of things, stoking the science fandom and getting people excited.

Education outreach, by contrast, is about making sure peoples’ beliefs are accurate. It teaches the audience something about the world around them, giving them a better understanding of how the world works.

In both cases, though, Sabine finds it hard to convince other scientists that outreach is valuable. Maybe inspiration helps increase grant funding, maybe education makes people vote better on scientific issues like climate change…but there isn’t a lot of research that shows that outreach really accomplishes either.

Sabine has a number of good suggestions in her post for how to make outreach more effective, but I’d like to take a step back and suggest that maybe we as a community are thinking about outreach in the wrong way. And in order to do that, I’m going to do a little outreach myself, and talk about black holes.

The black hole of physics outreach.

Black holes are collapsed stars, crushed in on themselves by their own gravity so much that one you get close enough (past the event horizon) not even light can escape. This means that if you sent an astronaut past the event horizon, there would be no way for them to communicate with you: any way they might try to get information to you would travel, at most, at the speed of light.

Einstein’s equations keep working fine past the event horizon, but despite that there are some people who view any prediction of what happens inside to be outside the scope of science. If there’s no way to report back, then how could we ever test our predictions? And if we can’t test our predictions, aren’t we missing the cornerstone of science itself?

In a rather entertaining textbook, physicists Edwin F. Taylor and John Archibald Wheeler suggest a way around this: instead of sending just one astronaut, send multiple! Send a whole community! That way, while we might not be able to test our predictions about the inside of the event horizon, the scientific community that falls in certainly can. For them, those predictions aren’t just meaningless speculation, but testable science.

If something seems unsatisfying about this, congratulations: you now understand the purpose of outreach.

As long as scientific advances never get beyond a small community, we’re like Taylor and Wheeler’s astronauts inside the black hole. We can test our predictions among each other, verify them to our heart’s content…but if they never reach the wider mass of humanity, then what have we really accomplished? Have we really created knowledge, when only a few people will ever know it?

In my Who Am I? post, I express the hope that one day the science I blog about will be as well known as electrons and protons. That might sound farfetched, but I really do think it’s possible. In one hundred years, electrons and protons went from esoteric discoveries of a few specialists to something children learn about in grade school. If science is going to live up to its purpose, if we’re going to escape the black hole of our discipline, then in another hundred years quantum field theory needs to do the same. And by doing outreach work, each of us is taking steps in that direction.

What’s the Matter with Dark Matter, Matt?

It’s very rare that I disagree with Matt Strassler. That said, I can’t help but think that, when he criticizes the press for focusing their LHC stories on dark matter, he’s missing an important element.

From his perspective, when the media says that the goal of the new run of the LHC is to detect dark matter, they’re just being lazy. People have heard of dark matter. They might have read that it makes up 23% of the universe, more than regular matter at 4%. So when an LHC physicist wants to explain what they’re working on to a journalist, the easiest way is to talk about dark matter. And when the journalist wants to explain the LHC to the public, they do the same thing.

This explanation makes sense, but it’s a little glib. What Matt Strassler is missing is that, from the public’s perspective, dark matter really is a central part of the LHC’s justification.

Now, I’m not saying that the LHC’s main goal is to detect dark matter! Directly detecting dark matter is pretty low on the LHC’s list of priorities. Even if it detects a new particle with the right properties to be dark matter, it still wouldn’t be able to confirm that it really is dark matter without help from another experiment that actually observes some consequence of the new particle among the stars. I agree with Matt when he writes that the LHC’s priorities for the next run are

  1. studying the newly discovered Higgs particle in great detail, checking its properties very carefully against the predictions of the “Standard Model” (the equations that describe the known apparently-elementary particles and forces)  to see whether our current understanding of the Higgs field is complete and correct, and

  2. trying to find particles or other phenomena that might resolve the naturalness puzzle of the Standard Model, a puzzle which makes many particle physicists suspicious that we are missing an important part of the story, and

  3. seeking either dark matter particles or particles that may be shown someday to be “associated” with dark matter.

Here’s the thing, though:

From the public’s perspective, why do we need to study the properties of the Higgs? Because we think it might be different than the Standard Model predicts.

Why do we think it might be different than the Standard Model predicts? More generally, why do we expect the world to be different from the Standard Model at all? Well there are a few reasons, but they generally boil down to two things: the naturalness puzzle, and the fact that the Standard Model doesn’t have anything that could account for dark matter.

Naturalness is a powerful motivation, but it’s hard to sell to the general public. Does the universe appear fine-tuned? Then maybe it just is fine-tuned! Maybe someone fine-tuned it!

These arguments miss the real problem with fine-tuning, but they’re hard to correct in a short article. Getting the public worried about naturalness is tough, tough enough that I don’t think we can demand it of the average journalist, or accuse them of being lazy if they fail to do it.

That leaves dark matter. And for all that naturalness is philosophically murky, dark matter is remarkably clear. We don’t know what 96% of the universe is made of! That’s huge, and not just in a “gee-whiz-cool” way. It shows, directly and intuitively, that physics still has something it needs to solve, that we still have particles to find. Unless you are a fan of (increasingly dubious) modifications to gravity like MOND, dark matter is the strongest possible justification for machines like the LHC.

The LHC won’t confirm dark matter on its own. It might not directly detect it, that’s still quite up-in-the-air. And even if it finds deviations from the Standard Model, it’s not likely they’ll be directly caused by dark matter, at least not in a simple way.

But the reason that the press is describing the LHC’s mission in terms of dark matter isn’t just laziness. It’s because, from the public’s perspective, dark matter is the only vaguely plausible reason to spend billions of dollars searching for new particles, especially when we’ve already found the Higgs. We’re lucky it’s such a good reason.

Only the Boring Kind of Parallel Universes

PARALLEL UNIVERSES AT THE LHC??

No. No. Bad journalist. See what happens when you…

Mir Faizal, one of the three-strong team of physicists behind the experiment, said: “Just as many parallel sheets of paper, which are two dimensional objects [breadth and length] can exist in a third dimension [height], parallel universes can also exist in higher dimensions.

Bad physicist, bad! No biscuit for you!

Not nice at all!

For the technically-minded, Sabine Hossenfelder goes into thorough detail about what went wrong here. Not only do parallel universes have nothing to do with what Mir Faizal and collaborators have been studying, but the actual paper they’re hyping here is apparently riddled with holes.

BLACK holes! …no, actually, just logic holes.

But why did parallel universes even come up? If they have nothing to do with Faizal’s work, why did he mention them? Do parallel universes ever come up in real physics at all?

The answer to this last question is yes. There are real, viable ideas in physics that involve parallel universes. The universes involved, however, are usually boring ones.

The ideas are generally referred to as brane-world theories. If you’ve heard of string theory, you’ve probably heard that it proposes that the world is made of tiny strings. That’s all well and good, but it’s not the whole story. String theory has other sorts of objects in it too: higher dimensional generalizations of strings called membranes, branes for short. In fact, M theory, the theory of which every string theory is some low-energy limit, has no strings at all, just branes.

When these branes are one-dimensional, they’re strings. When they’re two-dimensional, they’re what you would normally picture as a membrane, a vibrating sheet, potentially infinite in size. When they’re three-dimensional, they fill three-dimensional space, again potentially up to infinity.

Filling three dimensional space, out to infinity…well that sure sounds a whole lot like what we’d normally call a universe.

In brane-world constructions, what we call our universe is precisely this sort of three-dimensional brane. It then lives in a higher-dimensional space, where its position in this space influences things like the strength of gravity, or the speed at which the universe expands.

Sometimes (not all the time!) these sorts of constructions include other branes, besides the one that contains our universe. These other branes behave in a similar way, and can have very important effects on our universe. They, if anything, are the parallel universes of theoretical physics.

It’s important to point out, though that these aren’t the sort of sci-fi parallel universes you might imagine! You aren’t going to find a world where everyone has a goatee, or even a world with an empty earth full of teleporting apes.

Pratchett reference!

That’s because, in order for these extra branes to do useful physical work, they generally have to be very different from our world. They’re worlds where gravity is very strong, or world with dramatically different densities of energy and matter. In the end, this means they’re not even the sort of universes that produce interesting aliens, or where we could send an astronaut, or really anything that lends itself well to (non-mathematical) imagination. From a sci-fi perspective, they’re as boring as can be.

Faizal’s idea, though, doesn’t even involve the boring kind of parallel universe!

His idea involves extra dimensions, specifically what physicists refer to as “large” extra dimensions, in contrast with the small extra dimensions of string theory. Large extra dimensions can explain the weakness of gravity, and theories that use them often predict that it’s much easier to create microscopic black holes than it otherwise would be. So far, these models haven’t had much luck at the LHC, and while I get the impression that they haven’t been completely ruled out, they aren’t very popular anymore.

The thing is, extra dimensions don’t mean parallel universes.

In fiction, the two get used interchangeably a lot. People go to “another dimension”, vaguely described as traveling along another dimension of space, and find themselves in a strange new world. In reality, though, there’s no reason to think that traveling along an extra dimension would put you in any sort of “strange new world”. The whole reason that our world is limited to three dimensions is because it’s “bound” to something: a brane, in the string theory picture. If there’s not another brane to bind things to, traveling in an extra dimension won’t put you in a new universe, it will just put you in an empty space where none of the types of matter you’re made of even exist.

It’s really tempting, when talking to laypeople, to fall back on stories. If you mention parallel universes, their faces light up with the idea that this is something they get, if only from imaginary examples. It gives you that same sense of accomplishment as if you had actually taught them something real. But you haven’t. It’s wrong, and Mir Faizal shouldn’t have stooped to doing it.

What Counts as a Fundamental Force?

I’m giving a presentation next Wednesday for Learning Unlimited, an organization that presents educational talks to seniors in Woodstock, Ontario. The talk introduces the fundamental forces and talks about Yang and Mills before moving on to introduce my work.

While practicing the talk today, someone from Perimeter’s outreach department pointed out a rather surprising missing element: I never mention gravity!

Most people know that there are four fundamental forces of nature. There’s Electromagnetism, there’s Gravity, there’s the Weak Nuclear Force, and there’s the Strong Nuclear Force.

Listed here by their most significant uses.

What ties these things together, though? What makes them all “fundamental forces”?

Mathematically, gravity is the odd one out here. Electromagnetism, the Weak Force, and the Strong Force all share a common description: they’re Yang-Mills forces. Gravity isn’t. While you can sort of think of it as a Yang-Mills force “squared”, it’s quite a bit more complicated than the Yang-Mills forces.

You might be objecting that the common trait of the fundamental forces is obvious: they’re forces! And indeed, you can write down a force law for gravity, and a force law for E&M, and umm…

[Mumble Mumble]

Ok, it’s not quite as bad as xkcd would have us believe. You can actually write down a force law for the weak force, if you really want to, and it’s at least sort of possible to talk about the force exerted by the strong interaction.

All that said, though, why are we thinking about this in terms of forces? Forces are a concept from classical mechanics. For a beginning physics student, they come up again and again, in free-body diagram after free-body diagram. But by the time a student learns quantum mechanics, and quantum field theory, they’ve already learned other ways of framing things where forces aren’t mentioned at all. So while forces are kind of familiar to people starting out, they don’t really match onto anything that most quantum field theorists work with, and it’s a bit weird to classify things that only really appear in quantum field theory (the Weak Nuclear Force, the Strong Nuclear Force) based on whether or not they’re forces.

Isn’t there some connection, though? After all, gravity, electromagnetism, the strong force, and the weak force may be different mathematically, but at least they all involve bosons.

Well, yes. And so does the Higgs.

The Higgs is usually left out of listings of the fundamental forces, because it’s not really a “force”. It doesn’t have a direction, instead it works equally at every point in space. But if you include spin 2 gravity and spin 1 Yang-Mills forces, why not also include the spin 0 Higgs?

Well, if you’re doing that, why not include fermions as well? People often think of fermions as “matter” and bosons as “energy”, but in fact both have energy, and neither is made of it. Electrons and quarks are just as fundamental as photons and gluons and gravitons, just as central a part of how the universe works.

I’m still trying to decide whether my presentation about Yang-Mills forces should also include gravity. On the one hand, it would make everything more familiar. On the other…pretty much this entire post.

Pics or It Didn’t Happen

I got a tumblr recently.

One thing I’ve noticed is that tumblr is a very visual medium. While some people can get away with massive text-dumps, they’re usually part of specialized communities. The content that’s most popular with a wide audience is, almost always, images. And that’s especially true for science-related content.

This isn’t limited to tumblr either. Most of my most successful posts have images. Most successful science posts in general involve images. Think of the most interesting science you’ve seen on the internet: chances are, it was something visual that made it memorable.

The problem is, I’m a theoretical physicist. I can’t show you pictures of nebulae in colorized glory, or images showing the behavior of individual atoms. I work with words, equations, and, when I’m lucky, diagrams.

Diagrams tend to work best, when they’re an option. I have no doubt that part of the Amplituhedron‘s popularity with the press owes to Andy Gilmore’s beautiful illustration, as printed in Quanta Magazine’s piece:

Gotta get me an artist.

The problem is, the nicer one of these illustrations is, the less it actually means. For most people, the above is just a pretty picture. Sometimes it’s possible to do something more accurate, like a 3d model of one of string theory’s six-dimensional Calabi-Yau manifolds:

What, you expected a six-dimensional intrusion into our world *not* to look like Yog-Sothoth?

A lot of the time, though, we don’t even have a diagram!

In those sorts of situations, it’s tempting to show an equation. After all, equations are the real deal, the stuff we theorists are actually manipulating.

Unless you’ve got an especially obvious equation, though, there’s basically only one thing the general public will get out of it. Either the equation is surprisingly simple,

Isn’t it cute?

Or it’s unreasonably complicated,

Why yes, this is one equation that covers seventeen pages. You're lucky I didn't post the eight-hundred page one.

Why yes, this is one equation that covers seventeen pages. You’re lucky I didn’t post the eight-hundred page one.

This is great for first impressions, but it’s not very repeatable. Show people one giant equation, and they’ll be impressed. Show them two, and they won’t have any idea what the difference is supposed to be.

If you’re not showing diagrams or equations, what else can you show?

The final option is, essentially, to draw a cartoon. Forget about showing what’s “really going on”, physically or mathematically. That’s what the article is for. For an image, just pick something cute and memorable that references the topic.

When I did an article for Ars Technica back in 2013, I didn’t have any diagrams to show, or any interesting equations. Their artist, undeterred, came up with a cute picture of sushi with an N=4 on it.

That sort of thing really helps! It doesn’t tell you anything technical, it doesn’t explain what’s going on…but it does mean that every time I think of the article, that image pops into my head. And in a world where nothing lasts without a picture to document it, that’s a job well done.

Sorry Science Fiction, Quantum Gravity Doesn’t Do What You Think It Does

I saw Interstellar this week. There’s been a lot of buzz among physicists about it, owing in part to the involvement of black hole expert Kip Thorne in the film’s development. I’d just like to comment on one aspect of the film that bugged me, a problem that shows up pretty frequently in science fiction.

In the film, Michael Caine plays a theoretical physicist working for NASA. His dream is to save humanity from an Earth plagued by a blight that is killing off the world’s food supply. To do this, he plans to build giant anti-gravity spaceships capable of taking as many people as possible away from the dying Earth to find a new planet capable of supporting human life. And in order to do that, apparently, he needs a theory of quantum gravity.

The thing is, quantum gravity has nothing to do with making giant anti-gravity spaceships.

Michael Caine lied to us?

This mistake isn’t unique to Interstellar. Lots of science fiction works assume that once we understand quantum gravity then everything else will follow: faster than light travel, wormholes, anti-gravity…pretty much every sci-fi staple.

It’s not just present in science fiction, either. Plenty of science popularizers like to mention all of the marvelous technology that’s going to come out of quantum gravity, including people who really should know better. A good example comes from a recent piece by quantum gravity researcher Sabine Hossenfelder:

But especially in high energy physics and quantum gravity, progress has basically stalled since the development of the standard model in the mid 70s. […] it is a frustrating situation and this makes you wonder if not there are other reasons for lack of progress, reasons that we can do something about. Especially in a time when we really need a game changer, some breakthrough technology, clean energy, that warp drive, a transporter!

None of these are things we’re likely to get from quantum gravity, and the reason is rather basic. It boils down to one central issue: if we can’t control the classical physics, we can’t control the quantum physics.

When science fiction authors speculate about the benefits of quantum gravity, they’re thinking about the benefits of quantum mechanics. Understanding the quantum world has allowed some of the greatest breakthroughs of the 20th century, from miniaturizing circuits to developing novel materials.

The assumption writers make is that the same will be true for quantum gravity: understand it, and gravity technology will flow. But this assumption forgets that quantum mechanics was so successful because it let us understand things we were already working with.

In order to miniaturize circuits, you have to know how to build a circuit in the first place. Only then, when you try to make the circuit smaller and don’t understand why it stops working, does quantum mechanics step in to tell you what you’re missing. Quantum mechanics helps us develop new materials because it helps us understand how existing materials work.

We don’t have any gravity circuits to shrink down, or gravity materials to understand. When gravity limits our current technology, it does so on a macro level (such as the effect of the Earth’s gravity on GPS satellites) not on a quantum level. If there isn’t a way to build anti-gravity technology using classical physics, there probably isn’t a way using quantum physics.

Scientists and popularizers generally argue that we can’t know what the future will bring. This is true, up to a point. When Maxwell wrote down equations to unify electricity and magnetism he could not have imagined the wealth of technology we have today. And often, technologies come from unexpected places. The spinoff technologies of the space race are the most popular example, another is that CERN (the facility that houses the Large Hadron Collider) was instrumental in developing the world wide web.

While it’s great to emphasize the open-ended promise of scientific advances (especially on grant applications!), in this context it’s misleading because it erases the very real progress people are making on these issues without quantum gravity.

Want to invest in clean energy? There are a huge number of scientists working on it, with projects ranging from creating materials that can split water using solar energy to nuclear fusion. Quantum gravity is just about the last science likely to give us clean energy, and I’m including the social sciences in that assessment.

How about a warp drive?

Indeed, how about one?

That’s not obviously related to quantum gravity either. There has actually been some research into warp drives, but they’re based on a solution to Einstein’s equations without quantum mechanics. It’s not clear whether quantum gravity has something meaningful to say about them…while there are points to be made, from what I’ve been able to gather they’re more related to talking about how other quantum systems interact with gravity than the quantum properties of gravity itself. The same seems to apply to the difficulties involved in wormholes, another sci-fi concept that comes straight out of Einstein’s theory.

As for teleportation, that’s an entirely different field, and it probably doesn’t work how you think it does.

So what is quantum gravity actually good for?

Quantum gravity becomes relevant when gravity becomes very strong, places where Einstein’s theory would predict infinitely dense singularities. That means the inside of black holes, and the Big Bang. Quantum gravity smooths out these singularities, which means it can tell you about the universe’s beginnings (by smoothing out the big bang and showing what could cause it), or its long-term future (for example, problems with the long-term evolution of black holes).

These are important questions! They tell us about where we come from and where we’re going: in short, about our ultimate place in the universe. Almost every religion in history has tried to answer these questions. They’re very important to us as a species, even if they don’t directly impact our daily lives.

What they are not, however, is a source of technology.

So please, science fiction, use some other field for your plot-technology. There are plenty of scientific advances to choose from, people who are really working on cutting-edge futuristic stuff. They don’t need to wait on a theory of quantum gravity to get their work done. Neither do you.