Why aliens might not “speak physics” the same way we do

One of the mightiest facts we’ve uncovered about the Universe is this: that no matter when we look at it, near or far, we observe and measure it playing by the same laws, rules, and being made of the same ingredients that we see here in our own backyard. It takes the Copernican principle — the notion that we, here on Earth, don’t occupy a special, privileged location — to the most general form imaginable. Copernicus famously recognized that the Earth wasn’t a privileged location, and was just an ordinary planet orbiting the Sun like Mercury, Venus, Mars, Jupiter, and Saturn were. Similarly, our cosmic location, including our time after the Big Bang and place in the Local Group, have nothing “special” about them. It’s a generally accepted principle, and one that’s consistent with the full suite of observable evidence.

Over the past few hundred years, humans have advanced, both scientifically and technologically, in tremendous leaps and bounds. Scientifically, we’ve discovered the fundamental forces that govern the Universe, the full suite of particles that make up the Standard Model, and have reconstructed nearly our entire cosmic history. Technologically, we can break the bonds of gravity that have so long tethered us to Earth, can send and receive signals across vast interstellar distances, and hope to someday send spacecraft and, eventually, even humans to other potentially inhabited worlds.

But if-and-when we find our first intelligent alien civilization, would they “speak the same laws of physics” that we do? That’s the big question that physicist Daniel Whiteson and his coauthor Andy Warner explore in their new book, Do Aliens Speak Physics? And Other Questions about Science and the Nature of Reality.

Someday, perhaps soon, humans hope to discover our first sign of alien life that began someplace other than Earth. If that life is intelligent, technologically advanced, and spacefaring, we often assume that they would have uncovered the same laws of physics that we know today. But in the new book, “Do Aliens Speak Physics?” this conventional wisdom is challenged in an intelligent, compelling, and humorous way.

From a physicist’s point of view, it might seem like arriving at the presently known laws of physics — the best and most successful framework we’ve ever found for accurately describing and predicting the behaviors observed in reality — is an inevitability for any alien civilization that becomes at least as advanced as we are. But is this necessarily true, or could it be another example of our human-centric bias: where we take what we’ve accomplished on Earth and view it as an inevitability for any similarly-advanced species that might exist elsewhere in the Universe?

Sure, the rules might be the same everywhere, as the Universe fundamentally uses the same fundamental ingredients and the same fundamental laws to form stars, planets, and whatever molecular machinery arises on those worlds all throughout the Universe. But given the enormous diversity of life that already exists on Earth, as well as the countless number of potential alternate outcomes that could have been in store for our world if just one or two random events led to different outcomes, it’s worth considering that realizations, epiphanies, and breakthroughs that we consider as “inevitable” might not have necessarily occurred in the same way for other intelligent civilizations.

I had the recent opportunity to speak to Daniel Whiteson about these topics, and what follows is a ten question Q&A excerpted from our full interview (available starting November 8th).

The MeerKAT array, the first step in the construction of the Square Kilometer Array, has already produced an unprecedented set of science images and data that takes us one step closer toward understanding our galactic center. The science of SETI and the science of astronomy and astrophysics have many overlaps as we seek to uncover all that’s out there in the Universe.

Ethan Siegel (ES): I guess it had never really occurred to me to think that an intelligent alien species that’s capable of becoming technologically advanced, that’s capable of conducting at least interstellar communication, if not outright interstellar travel, surely they would have at least uncovered the same laws of physics that we have here in our technological infancy in the 21st century. But as you argue in the book, that isn’t necessarily the case. Can you sort of explain to us why my thinking on this might be the naive point of view, and why intelligent aliens might not have necessarily developed the same rules of mathematics and the same laws of physics and discovered the same things that we have here on Earth?

Daniel Whiteson (DW): Yeah, it’s a super fun question to dig into. And one reason I think it’s exciting is that the answer you just described is very compelling. It’s very attractive. It’s very seductive. It suggests that like, as Newton expanded our concept of physics from the Earth into the heavens, that now we can describe the whole universe. And we think the same laws of physics apply, you know, to an apple and to the Moon and to distant galaxies. That also that might suggest that the inhabitants of those galaxies should find those same laws of physics. Now, if we meet up, we could have a conversation about physics and quantum gravity and work together on all of these mysteries that were like part of a galactic community.

That’s very exciting and you know that’s what I want to be true. But we should always be skeptical, especially of ideas that are flattering. That put us at sort of the center of the universe. We’ve made that mistake many times in assuming that there’s something special about us or about Earth. And so assuming that the way that we describe the universe, the way that we explain the phenomena that we see out there, is the only way to explain it, might be making that same mistake: might be confusing our description of the universe with the universe itself.

The WISPR data from the Parker Solar Probe, in monochrome, clearly matches the surface features seen by the significantly longer-than-optical wavelengths of the orbiter Magellan, shown in assigned color. The view of Venus from the Parker Solar Probe represents the first time the clouds of Venus have ever been seen parting, revealing the surface below.

ES: So I can, I can agree with a lot of that on the surface, certainly, right? When I look at how science has developed here on Earth, we were of course restricted in the early days of science to looking at what we could observe or measure or experiment on with our five senses, right? If aliens lived on a very cloudy planet, they might not use astronomy to sort of uncover what the laws of gravity are, and they might not make the connection between the things that happen on the surface of their world and what’s happening in the heavens above them the way Newton did.

But I do like to think that as we’ve gotten more advanced, as we’ve basically, you know, uncovered the types of technologies that would allow us to leave the bonds of our planet’s gravity, that would allow us to communicate ultra long distances across the galaxy. I think, well, surely aliens, even if they formulate it differently, even if they view it differently, for example, if they used Heisenberg’s matrix mechanics instead of the Schrodinger equation, or if they used Tomonaga’s quantum field theory formalisms instead of Feynman’s or Schwinger’s quantum field theory formalisms, surely they would still find the same laws of physics, because that’s one of the huge things we’ve been able to establish, is that the laws of physics that we see here and now on Earth actually appear to be the same everywhere and at all times across the universe.

Would you have a counterargument to make against that point of view?

DW: Boy, do I have lots of counter arguments. I understand that it’s hard to imagine things operating another way or aliens not doing science the way that we do. But in the same way, it’s hard to imagine, you know, somebody not starting their morning with coffee or sleeping on a bed the way that I do or organizing their family structure in a way that’s familiar to me. And these are cultural choices, obviously, right? But it’s still hard for us to break our break out of that sandbox and imagine other ways of living. And so just because it’s hard for us to imagine doesn’t mean, of course, that it’s impossible.

That’s the hard part: is trying to break out of that sandbox and really think about whether other ways are possible, whether our way of doing it is the only possible way or just the way that makes sense to us because it’s what we’re familiar with. So let’s start with what you stated: with perception. Do aliens perceive the same universe as we do, and could that influence their science? You know, there’s fascinating biological questions here about what senses aliens might natively evolve. Would they see the same visible spectrum as us? Would they develop senses for magnetic field or electric fields? These are really fun biological questions that depend on the details of their environment. And even here on Earth, you can already see an incredible spectrum. of different kinds of senses that animals on Earth develop.

We know that there are more senses out there than we humans have. And we also know more fundamentally that there’s a lot of the universe that we do not sense, right? Neutrinos we can’t interact with. Dark matter is most of the stuff in the universe and we have no senses that let us interact with it. It’s completely unavailable in our sensorium.

The periodic table of the elements is sorted as it is (in row-like periods and column-like groups) because of the number of free/occupied valence electrons, which is the number one factor in determining each atom’s chemical properties. Atoms can link up to form molecules in tremendous varieties, but it’s the electron structure of each one that primarily determines what configurations are possible, likely, and energetically favorable.

ES: I still have a hard time believing that they wouldn’t have investigated the same properties of nature, that they wouldn’t have found, for example, that atoms of different species exist and can be sorted into a type of periodic table, even if they draw their table differently, that elements in the same columns have similar properties. I have a hard time believing that they wouldn’t have gone further and uncovered what’s inside the atom and developed nuclear and particle physics. I have a hard time believing that they wouldn’t have found the same force laws governing the universe, even if they didn’t have a concept of force and just talked about it as a derivative of a potential or as the impetus provided by a field or, or some other equivalent formalism.

DW: You might argue, “Okay Daniel, we’re not just using our raw senses anymore. We’re using technological eyeballs, we can see in the infrared, we have ultraviolet space telescopes, we’ve detected dark matter, we have essentially expanded our ability to interact with the universe via technology,” which is true. But what I wonder if we really expanded is our way to conceive of the universe, because in your mind your senses build a model of the universe.

Like, look at the room that you’re in right now. Your vision and your sound and all of your senses have put together in your head a model of what’s around you. You know that’s lacking. You know that, for example, you’re not describing the dark matter or the neutrinos or most of the electromagnetic radiation that is around you. The model you’ve built is limited. And it turns out that every time that I think that this affects strongly the way that we build a model of physics as well, because every time we develop one of these technological eyeballs, we end up translating its output back into our native sensorium.

When you look at images the from from the James Webb Space Telescope, for example, you don’t see them in the raw infrared. They would just look black to you. Their color is shifted. When we hear about gravitational waves, they are played to us as sound because [that’s how] we can experience them. And so I think that there is a way that we express our understanding of the universe that is fundamentally defined or influenced by the senses that we did natively evolve to, because we tend to translate everything back into that language. in physics is about explaining the unfamiliar in terms of the familiar.

We try to express, “what is a photon?” We describe it in terms like waves and particles and sort of things. None of these things are fully appropriate because a photon has no exact intuitive analog. So all this is to say that I think that our senses might be different from aliens’, and those senses can really influence the way we think about the physical universe and the way we explain it. Not just the model you make in your head of your room, but also the physical model that we build of the universe. And so I think that’s one starting place to wonder whether our biological history, our evolutionary path to these set of senses has somehow influenced the way that we describe the universe.

If each time a quantum decision were made, our timeline split to allow for two (and only two) possible outcomes, then the number of overall possibilities would increase incredibly rapidly, depending on which combinations of outcomes and what order-of-interactions are allowed. These possibilities cannot all fit within our physical, observable Universe, but the mathematical structure known as a Hilbert space, leveraged in quantum mechanical calculations, can contain them all.

ES: I agree with a lot of this: that our senses do inform not just how we make sense of the other phenomena in the world, but how our intuition works. And I feel like this is both a blessing and a curse for us. I will tell you something that will probably not go over very well with my audience: I find it just deathly boring is when people argue over interpretations of quantum mechanics, that people argue which interpretation is best. By going into this quantum realm, we have finally encountered something that is foreign to our intuition, yet we can write down the rules it obeys and we can calculate everything that’s calculable about this system and what the probability distribution of outcomes of this system will be under a huge variety of experimental conditions.

And yet, that’s not enough for us. We have this idea that that people need to somehow make sense of it as though describing it physically is not exactly how you make sense of it. We have this need to make it fall in under a more intuitive framework. And honestly, I think that’s where we go wrong. I would assert that it would only make sense that what aliens would derive as physics would be what what a mathematician would call “isomorphic” or “holomorphic” to our own interpretation of physics: to our own view of how it works. Maybe they have different ways of describing it, maybe they have different terms that they use and maybe they have different observables that they measure. But at the end, it’s going to be an equivalent underlying law.

DW: Well, you know, my personal feelings are that we don’t know, of course, we can’t know, and I’m excited to meet the aliens and actually find out. I think my role here today is to argue the other side of this and to suggest that there’s a broader spectrum of possibilities than we might initially imagine. Would aliens have developed an alternative theory? And I agree with you that a lot of the questions that people struggle with like about quantum mechanics those are the philosophical implications of the physics, and you don’t strictly need to talk about that if you just want to do the physics. If all you’re going to do is do the calculations and predict the experiments you don’t really care about like, “what is real” and “what does it mean, man?”

But I think that that ignores what physics is about for some people. For some people, yes, it’s just let’s predict the outcome of the next round of experiments at CERN or in space. But for a lot of people, physics is there to answer those questions, to tell us how the universe works, what is the story, what’s going on behind the scenes. And I think that in the end, that’s actually a little bit inescapable. Even if you want to just take the mathematics and use it to calculate, that mathematics and that theory is always doing something, is always telling us something about the invisible aspects of the universe. The mechanics are going on behind the curtain.

Take General Relativity: there’s this notion that space has a metric on it and this has this invisible curvature, which is the reason why things are moving. And that describes reality very, very well, but it’s kind of an invisible machinery we have added to the universe that we use to make these calculations. And so when you ask, could aliens have another theory of physics and does it have to be completely isomorphic to ours? There’s not a known answer to that question. And philosophers of physics argue about this endlessly.

Is possible to have another theory of physics which is not isomorphic: which doesn’t just map directly like from fields to “schmields,” maybe they have a completely different set of concepts. Is it possible to do that? Well, in principle, it should be. I mean, any set of data you have, if you measure the trajectory of a ball flying through the air, you can always explain it with one curve. And there’s always an infinite set of other curves you could use to describe the same data. Because you don’t have infinite data about where the ball went, you could fit lots of different curves to it. And even if you did have infinite data, would always be gaps in those data measurements. It’s always something you don’t know. And so, in principle, there is always an alternative hypothesis that could explain the data.

Is gravity a force? Is it just the curvature of space? And so I think it is difficult to imagine aliens coming up with a very precise set of machinery that can predict the outcome of experiments at CERN and quantum experiments and General Relativity down to 17 digits without using the same machinery or machinery that we could map to ours. That doesn’t mean that it’s impossible. To me that’s exciting because it tells us something about the nature of truth. Like what happens if aliens show up and they have a completely different theory that cannot be mapped to ours and yet is just as effective? That would be mind blowing. It would tell us that our description of the universe is just a description, not the description. It is difficult to imagine, and I’m personally skeptical that it’s the case, but we have no strong argument, no proof that there is a unique description of the universe.

Instead of an empty, blank, three-dimensional grid, putting a mass down causes what would have been ‘straight’ lines to instead become curved by a specific amount. In general relativity, space and time are continuous, with all forms of energy contributing to spacetime’s curvature. No matter how far away you get from a point mass, the curvature of space never reaches zero, but always remains at a non-zero value, even at infinite range.

ES: I can imagine aliens out there that have a completely different way of looking at the world, of perceiving the world, of interacting with the world, and maybe a different set of mathematical machinery that’s either more restrictive or less restrictive than our own. For example, if we work in physics, we say the sum of all of the probabilities of every possible outcome occurring have to add up to 100%. But if aliens didn’t have that concept of probability, or if aliens had a more restrictive concept of probability, perhaps they would have wound up with a completely different way to formulate, you know, their sets of outcomes.

Perhaps if aliens hadn’t developed complex numbers or the quaternions or the octonions, they would have said, well, you you can’t use these complex numbers in your calculations, but we pull the real part out of this and we have a formula for working with this in terms of oscillations that we use instead. And that’s how we devise it. Maybe they don’t have fields and maybe they don’t have potentials, but I have a very hard time believing that they wouldn’t have something that that would give an extremely close approximation to what our close approximation of reality looks like.

Because that’s really what physics is at the heart of it, is it’s not saying “this is reality.” It’s saying this is the best model of reality that we have come up with for interpreting the full suite of data. And I would argue that unless the intelligent aliens are also doing some version of that, then they wouldn’t be doing science and they also wouldn’t be able to reach the level of technological advancement that we ascribe to an alien civilization that would be capable of either reaching us through an interstellar journey or communicating with us through interstellar communication

DW: Well, I think, Ethan, that you’re probably very unusual among physicists. I think the vast majority of physicists are not comfortable saying physics is just the model and we have no idea what reality is. That’s very sort of agnostic about the nature of the answers to the questions I think a lot of people have. For example, if I walk around CERN and ask folks, “Hey, is the Higgs boson real or is it just part of our model to describe our experiments?” They would look at me like, you know, did you have some bad coffee or something you need to go back to sleep for your jet lag? Of course the Higgs boson is real. They won a Nobel Prize for predicting it and then we discovered it. Because I think a lot of people naturally make that leap to say, look, our physics is very accurate and therefore it’s describing reality. It’s not just a very effective model.

I think there is an important distinction for a lot of people. And that’s really what this question is asking. Do aliens do physics the same way we do is asking about the universality of our physics. Is it just a model and is it the only possible model? I want to come back to this question of like, do those sharks have to do science in order to communicate with us? And do we have to use mathematics as a foundation of our language?

Do we have to have developed science the same way? Assume that aliens are doing science and they’re using mathematics and they see the world the same way we do and they’re interested in the same things that we are and they ask the same questions and they would accept the same kind of answers. Even in the best case scenario for your human/alien scientific overlap, we might still not have a lot in common depending on the order of in which science develops.

You’re the kind of person who’s played Civilization or SimCity or whatever, there’s this sort of natural instinct to believe that the way we’ve developed our understanding of the universe is the only way: that it’s sort of linear. You find this out, then you find that out, then you get gunpowder, dot dot dot, spaceships. But, you know, history shows us that there’s a lot of randomness and disorder. In fact, as you say, a lot of the reasons we figure stuff out is because as mathematicians developed the tools we needed, not because they cared. They were just nerding out about numbers or patterns. For example, all of the developments in geometry at the end of the 1800s, those folks didn’t care about gravity. They were just interested in surfaces and geometry and thinking about these things. And then Einstein was like, Hey, this is exactly the tool I need to solve this problem. And there’s lots of other examples.

Essentially, that the questions we’re asking, the path that we’re going on to understanding the universe is not the only path. Even in a scenario where we have essentially complete perfect biological and philosophical overlap with the aliens, I think we’ll be surprised to find how different their trajectory was.

A cross-section of the Wealden Dome, in the south of England, which required hundreds of millions of years just to explain the erosion features observed, with fossils of past life found in the different layers. The chalk deposits on either side, absent in the center, provide evidence for an incredibly long geological timescale required to produce this structure: longer than any contemporary explanation for the Sun’s energy could have provided in the late 19th century. This was noted by none other than Charles Darwin in the mid-1800s, and would present a puzzle that would not be resolved until the process powering the Sun, nuclear fusion, became understood.

ES: I agree with that. I think that’s very likely, actually. I think that the order in which we discovered things here on Earth is probably unique to us, here, on Earth. For example, when we first discovered, geologically, what the age of the Earth was, we ran into this problem that we did not yet understand how the stars worked and how the universe worked. And so we were left with the uncomfortable conclusion, about 130 years ago, that the Earth was about twice as old as the universe was. That obviously was a flaw in our understanding: of the age of the universe. But perhaps, for an alien, it would be much much easier to determine the age of the universe than it is to determine the age of their home planet based on the order that they discovered things. So it’s quite possible that things would have developed very differently.

But I would throw back at you, if I wanted to argue the other side, that when we run into paradoxes where we discover something and it contradicts a different discovery that we’d made previously, then we look at that as an opportunity to advance our understanding. Because both of those things can’t be true at once. The Earth can’t be more than 4 billion years old if the universe is younger than 2 billion years old. It was that sort of tension that led us to uncovering how stars actually work, where they get their energy from: in the science of nuclear physics. So I think in terms of the order of operations, or the order of discovery, that things are almost guaranteed to be different elsewhere. But in terms of the laws you wind up with or their equivalent, I have a really hard time believing that aliens would not have reached the same level of sophistication that we’ve reached. It seems like when you uncover something about the universe that surprises you, you’re compelled to investigate it.

DW: So, you know, do aliens have to be curious? You described science as being motivated by our human curiosity. And I totally agree with you. And I think that something a lot of people don’t appreciate is how much personal, subjective emotion there is in what questions we choose to investigate. Why am I a particle physicist? Because to me, the deepest question in the universe, the most interesting one, the one I decided to spend my life investigating is the question of what are the fundamental bits and bobs of the universe?

That’s the thing I would ask an oracle if I could speak to it. Other people want to slosh around in the rainforest getting wet socks and studying how spiders swing through trees and even more power to them. I’m so glad that we have a diversity of curiosity in science, but that’s personal. It’s subjective. It’s that people go in different directions because they’re curious about these things and that curiosity is human, but we don’t know if it’s exclusively human. Would aliens have to be curious about the universe the same way?

There’s no mathematical proof of that. That’s the question of what we have in common with aliens. We could find aliens that are just, you know, piles of slime on rocks. We could find aliens that seem to be intelligent, but we can’t really make a connection with them the way we can’t even with like whales and dolphins here on Earth. We might find aliens that are very technological and you ask, “Do those species have to be, if they’re technologically advanced and can communicate with us or come visit us, do they have to also have discovered the same stuff as us?” I think it’s very likely that curiosity and developing a sort of mental model of the universe is common because it’s such a powerful accelerator. You want to develop technology and space travel… like it seems hard to imagine that you could do so efficiently without also understanding how the universe works. So you can, rather than stumbling blindly through technological exploration, you can be thoughtful about it.

This to-scale diagram shows the relative masses of the quarks and leptons, with neutrinos being the lightest particles and the top quark being the heaviest. No explanation, within the Standard Model alone, can account for these mass values. We now know that neutrinos can be no more massive than 0.45 eV/c² apiece, meaning that the difference between a neutrino’s mass and an electron’s mass is more than three times as large as the difference between the electron’s mass and the top quark’s mass.

ES: I’m not saying necessarily that everyone gets fascinated by radioactive decay the same way we do or gets fascinated by the physics going on inside the Sun. But I bet you at some point aliens would have discovered neutrinos and anti-neutrinos. I bet you at some point they would have discovered CP violation in the weak interactions. I bet you at some point they would have discovered the Sakharov conditions for generating a matter-antimatter asymmetry in the universe, it seems like if you look at the universe at a certain level of detail or with also knowing certain other things about the universe, you’re pretty much guaranteed to say, “Hey, I see something funny here. I see something that doesn’t line up with the basic predictions or assumptions I would have made previous to this. Let me investigate it further.”

That spirit, that curiosity is what leads to science and it’s why I’m so fond of reminding people that if we lost all of the scientific knowledge we ever gathered here on Earth, that we lost all of the data, we lost all of the methods, we lost all of the records of every experiment, measurement, observation that was ever taken or conducted, we could go out, observe the universe today and reach those same conclusions from scratch just by starting science over again. It might take a while and we might not follow the same path to get there, but we would eventually find the same laws governing reality because the same laws govern reality everywhere and at all times. And I don’t think you’re arguing against that.

DW: I think this is really fascinating because, you know, ask yourself, instead of talking about muons and anti-muons, zoom out a little bit and ask yourself, “Would aliens develop the Navier-Stokes equations?” You know, “Would aliens have developed Newton’s approximation to to Einstein’s gravity?” These are effective theories. They only work in certain situations. They’re not a fundamental description of the way universe works. They work in a certain phase of the universe, when the temperature is right, when the speeds are correct, when the density is correct. They’re effective and they’re powerful, but they’re not reality in any way.

It turns out that all of our theories of physics are like that. Even our description of what we now call fundamental physics, of electrons and neutrinos, these are effective theories. We don’t know what’s going on underneath. We don’t know if this is the deepest layer of reality. In fact, we suspect strongly that it’s not, that these are morally equivalent to Navier-Stokes equations and other effective theories of the universe. And in that sense, they’re valid within some boundaries.

The way that the Navier-Stokes equation works really well for fluids, but once you freeze it, it’s totally irrelevant. Once you boil it in the vapor, it doesn’t work very well. Only in certain boundaries does that effective theory apply. That’s also true for all of our theories of physics. They apply within certain boundaries. You make some assumptions and then you can derive effective laws of physics with assuming on the grounds of those assumptions and that limits the applicability of those theories. And what we don’t know is if each of those effective theories of physics is like a patch to some greater truth or if they’re just effective descriptions. You can’t start from, for example, the Standard Model and predict the weather, right? It’s totally impossible to make these leaps.

In fact, only with a few cases like the ideal gas law, can we start from particles and derive some sort of zoomed out effective theory? So we’re left with this patchwork of explanation of the universe that is very powerful within boundaries. But we don’t know if we could eventually stitch it together into some larger truth or if that larger truth even exists or if all we have are these effective theories. And so if what we’re doing is just describing the universe with effective theories, then what the theory will come with depends on the patch you’re looking at.

Are we curious about this kind of phenomenon? Only if aliens are curious about fluids are they going to develop Navier-Stokes equations. So if you expect aliens to show up and talk to us about fluid dynamics, you might be very disappointed. And so the other things that you mentioned, CP violation, et cetera, those also exist within the context of our effective theories. And if aliens have taken a different approach, different assumptions, zoomed in on a different level or chosen a different patch of the universe to focus on, they could have a very different set of effective theories that also work to describe the universe, right? But could be sort of incoherent when we try to bring them together with our set of physics.

This reconstruction of particle tracks shows a candidate Higgs event in the ATLAS detector at the Large Hadron Collider at CERN. Note how even with the clear signatures and transverse tracks, there is a shower of other particles; this is due to the fact that protons are composite particles, and due to the fact that dozens of proton-proton collisions occur with every bunch crossing. At higher energies, discoveries that don’t appear at lower energies become possible. Modern particle detectors are like a layer-cake, with the ability to track the particle debris in order to reconstruct what happened as close to the collision point as possible.

ES: I actually agree with all that you said here this time and I want to go back to something you brought up earlier where you talked about imagining going through the hallways at CERN and asking other physicists, is the Higgs boson real? Because, you know, what I would say is if you would go up to me and ask me, the Higgs boson real? I would probably tell you it is real. I probably wouldn’t say, well, it’s our best approximation of what reality is. But I would say it’s real in the sense that any other particle in the standard model is real. If you would ask me about that in detail, I would say, “Well, listen, I know that this is our best approximation of reality. Within the framework that we currently understand reality, at the deepest or most fundamental level, the Higgs boson is a particle just as much as the photon is a particle or a gluon is a particle or a quark or an electron is a particle. These are particles because we can measure certain properties that they have and they behave particle-like under certain sets of conditions.”

What you just brought up now is something I often communicate to people in just a slightly different language, is that I say every physical theory that we’ve ever concocted has an established range of validity. It has this set of conditions that this is a good model of reality under. And if you go outside that range of validity, suddenly it may or may not hold. There are plenty of things that we have as our current best approximation of reality and beyond a certain limit, whether that’s in energy, in temperature, in density, whatever. We don’t know if those laws still hold, if those rules still hold. We don’t know or where those rules break down.

But I also think that if you’re going to invent, you know, rocketry and interstellar travel, you are going to need to understand what matter is made from and how it combines together in ways that lead to the release of energy: energy that will allow you to propel yourself across interstellar distances. I like to think that if you want to transmit a broadcast of sufficient power and that’s sufficiently targeted that you know where to send this high-power signal to in order to effectively communicate, similarly, you would need to have some basic understanding of physics at least that’s equivalent to how we understand it or you wouldn’t be able to get there. Now, you might be able to concoct some clever biology where they can do this without even needing to know that they’re doing it, and then I would argue to you, “Well, is that alien species even technologically advanced, or are they just really really fortunate with the types of organs that their history of life on their world endowed them with?”

DW: Yeah, it was really fun and in the book I actually write a bunch of these little counterfactual hypothetical situations. So the book is not just like, “here’s a bunch philosophical questions” like “here’s an example of what first contact might be like with aliens that are different in some weird way that’s hard for us to grok.”

I think that you’re right about the question of what people in the hallways of CERN would say, because I think that most physicists don’t think much about the question of “What is real?” and “What does real mean?” Because in the end, it’s a philosophical question, right? When we’re asking, “is the Higgs boson real,” we’re asking about the difference between it being in our model and it being there when we’re not looking. And that’s not a science experiment you can do. You can’t conduct an experiment to find out what would happen if you didn’t do an experiment. It’s really a question of philosophy.

I think that that philosophy gets a sort of a bad name in physics most of the time. I think that around the holidays, certain people are probably dismissive of philosophy, like, “Whatever, we’re just doing the calculations. Who cares about the philosophical questions?” And yet they have strong philosophical opinions about what real is. I think if you explain this to people, what we mean by, “is it there where we’re not looking?” They’ll be like, “Of course it’s there. What are you, crazy stuff, smoking banana peels?” So I think businesses in general have strong philosophical opinions yet tend to look down on philosophy weirdly. But I think that philosophy really informs these questions. And it really helps us think about what our assumptions are.

There’s a class of philosophers who argue that all we have are patchwork explanations of the universe. That between the patches, there is no methodological explanation for it. There’s this book by Nancy Cartwright called “How the laws of physics lie,” which suggests that you can’t even test what’s happening between the patches because because the experiments are too complicated. Take a simple example. Drop a penny outside, and, can you describe it? Yes, you can use Newton’s equations to describe it. Okay, now turn it into a leaf. Can you describe it? Sure, you can add air resistance. Your theory has to get a little bit more complicated, but you can still describe it. Okay, now add a tornado. So the leaf is very, very complex interactions and add 10 leaves and have them stuck together by rubber bands. And I can keep adding details to this situation until it becomes impossible for us practically to make a prediction for what’s going to happen.

We’re already there in our atmosphere, right? We can predict the weather a few days out, but not a week or two weeks. so Nancy Cartwright’s argument essentially is that there’s always some situation where we are incapable of predicting what happens. And so it might be that there are corners of the universe where, as she says, what happens, happens by half. And to me, that’s very alien to imagine that the universe could be not following some laws, that there isn’t some set of rules out there that determines what really happens?

But Cartwright’s argument essentially is we can’t know that; that’s a philosophical assumption. That’s a philosophical position: to say the universe has to be logical. has to follow laws. So far, in our experience, it has, but again, we’re not guaranteed. And so one of the questions of this book is to help us get our assumptions and wonder, well, which of the things that we assume are ironclad, and which are we just assuming? And which things do we actually have data to support? And a lot of people, it turns out, feel just as strongly about philosophical opinions as topics that we do have data to support them.

It’s possible to write down a variety of equations, like Maxwell’s equations, that describe the Universe. We can write them down in a variety of ways, but only by comparing their predictions with physical observations can we draw any conclusion about their validity. It’s why the version of Maxwell’s equations with magnetic monopoles (right) doesn’t correspond to reality, while the ones without (left) do. The displacement current term (the second term in the fourth equation) arose from Maxwell’s attempt to fix the incompleteness in electricity and magnetism that existed prior to his work: an important theoretical leap that turned out to accurately reflect reality.

ES: I would argue that there are conditions that we’ve encountered many times in science that lend itself towards a greater picture of unification. And I would say one of these things was when Newton among others, recognized that the law of gravitation that governs how bodies fall here on Earth, as investigated by Galileo and others, is the same law of gravitation that causes the planets to orbit the sun and the moons to orbit the planets. This was a huge insight, and yet it’s extremely profound. I have a very hard time imagining that aliens wouldn’t notice that insight.

It was a remarkable insight in the 19th century when Faraday and Ampere and Maxwell brought the previously unrelated phenomena of electricity and magnetism together, under the same footing, where we now know it as electromagnetism. Moreover, there’s the fact that they are not completely symmetric: because we have fundamental electric charges, positive and negative charges, but we don’t have fundamental magnetic charges, we don’t have north and south magnetic monopoles. Looking at these ideas where unification has helped, going all the way into modern particle physics and noticing that, oh, the electric force at the weak nuclear force are not separable, but they are intimately related to one another. The electroweak force is the correct scheme for unifying these. They lead to the predictions of, among other things, the W, Z, and Higgs bosons, which agree with reality in contrast to all of the other possible predictions that are out there.

I would say it’s reasonable to expect aliens would get this far. And I say this as someone who, honestly, I don’t think physics has gotten very far. Like it’s amazing what we’ve done. I could spend my lifetime learning all the incredible details of what we’ve done. But I also look at all the unexplored territory out there. I look at the, you know, 15 orders of magnitude between where the Large Hadron Collider has gotten us and where the Planck scale is. I look at the nine orders of magnitude between the highest energy cosmic rays and where the Planck scale is. And I say, wow, there’s so much more physics out there to be investigated. I look at the fact that we have a fundamental limit on our particle sizes of they’re no bigger than 10^-19 meters. And then I go, where’s the Planck scale? What? 10^-35 meters? Look how much more of nature we have to investigate out there.

I look at us still the way Isaac Newton looked at himself: that we are like children playing on the shore of the great cosmic ocean, where we’ve just waded into the waters, but not even up to our necks. And we look at the pretty pebbles and we say, look at this beautiful cosmic ocean. And yet we are so profoundly ignorant of the full ocean that’s out there. I would say, honestly, Daniel, if we meet intelligent aliens and they are not far more scientifically and technologically advanced than we are, it would be a huge disappointment.

DW: I know. It’s so frustrating to imagine that they could be out there, right now, and they could have answers to these questions. They could just beam them at us, or show up and explain to us. And I think that’s the fantasy that fuels this book for me: is that I want that to be true. I want them to show up and fast forward us into our scientific future. And essentially this is wondering, “What could that scientific future be? And what surprises are lying in wait for us?” Because I’m almost certain that there are some fundamentals, some assumptions we’re making about the nature of the universe that are wrong.

The history of our scientific development is discovering, one by one, that our intuition has misled us and that assumptions we’ve made about the way the universe has to work — like things have to have a location and a velocity at all points in time, if things are here and then there they have to go from here to there — that just make sense, of course it’s true and totally reasonable, statements like that have been upended of course by experiments that have shown us that the universe doesn’t operate that way at the smallest scale. And so we need to maintain that skepticism, even in the face of statements that seem to make obvious sense. If we don’t know, for sure, if we haven’t proven them, then we can’t rely on them.

So take your argument that we certainly can model that tornado of leaves because we’ve modeled two things and then three things and then four things. And as we keep pushing our computational abilities, things do eventually work. That’s true, but there’s always something we haven’t modeled. Just because we can do two and three doesn’t mean we can do 47,000. It’s possible that some other dynamics emerges in those scenarios that are not describable by our physics. And Nancy Cartwright makes this extra leap, which I struggle with, I will admit, but philosophically, I think she has some standing to say that we don’t know that there even are laws that describe those scenarios because, by construction, we can’t test them because we define them to be in the places that are too complex, too chaotic for us to model.

There will always be such corners of the universe, because all of our theories rely on some assumptions, some approximations, and have some boundaries. And so it’s not necessarily true that we can grow those theories together to make them make sense of the universe. And on the other hand, you’re right that we have this incredible, compelling history of unification of ideas coming together and clicking together in the most satisfying way to reveal something deeply true about the universe. That’s really powerful, and suggests something else about the universe that I think a lot of people feel we must have in common with aliens.

It’s generally assumed that at some level, gravity will be quantum, just like the other forces. While the semi-classical approximation for computing the decay of black holes involves performing quantum calculations in the classical background of Einstein’s curved space, that approach might not be valid for capturing the full suite of physical behavior that the outgoing radiation possesses, particularly as far as information is concerned.

ES: As for Nancy Cartwright’s assertion: she may be right. There may be problems out there where you need to understand laws that we have not yet uncovered in order to solve them. But the leaves in the tornado is not one of them. So that’s that’s not an example I’m gonna bite on. If we understand the laws of physics, and the boundary conditions, and the initial conditions of our system, then with enough computational power, we could predict those leaves and their motion arbitrarily far into the future. And I have no problem asserting that as far as the “without numbers” point of view goes.

I think it’s probably fine that you can make that coarse level of “almost science” work. But what separates, for me, modern science from any ancient philosophy that we attempt to do science with is, the quantitative footing. That science doesn’t just ask you what happens. It says, “How much?” “In what amount?” “By what quantity, by what measure?” Bringing those things together, answering the “how much” question, “what happens and by how much,” that’s what makes it science. That’s what makes things go. That’s what allows us to be efficient. That’s what allows us to make accurate predictions to, you know, 10, 15, 17 significant figures that then go out and agree with experiments. And where they disagree, that shows us where there are the flaws in our theories. If all we had was this qualitative explanation, you know, it might make some ancient philosopher like Plato very, very happy that we’ve, we’ve come this far, but for modern science, we demand much, more than that.

DW: Let me touch on the core issue: the method of science itself. You refer to this process of modern science, which I think you’re contrasting with ancient ways of thinking that are just sort of exploratory and wondering about the universe and investigating things in our minds. I think it’s illuminating to remember that what we call modern science is very new. The way that we talk about science, way that you and I have a career as scientists, we have institutions in our culture, at least for now, that we call scientific institutions, and the process of science itself, the way we go about it, is fairly new in our development.

But we have been asking questions and checking things. There’s this story that the Greeks weren’t scientific, but they did experiments. Like Eratosthenes measured the radius of the Earth using a stick and shadows. That’s an experiment. He was quantitative about it. So I think the development of science itself is more gradual than people like to think, which is important to consider becauseit suggests that maybe science isn’t, like, at some final plateau. I think a lot of people imagine, “Okay, we found science and now we’re sciencing.” But the process itself of science is developing, it’s continuing to change. And it’s hard to imagine that in a thousand years or a million years, if we’re still here, humans will still be doing science the way that we are doing it now.

It’s likely they’ll have some other new addition to the process or direction they’ve taken, which makes it vastly more powerful to interrogate the universe and reveal its structures. In the way that adding empiricism, or adding simulations, has to our modern process of science. And so if we’re talking about “are aliens scientific?” well, maybe they are, but likely it’s very, very different from the ways that we are scientific. They could look back at us and imagine like, “Wow, your science is all really primitive. You can’t haven’t even figured out that you should do X, Y and Z things that we haven’t imagined.”

And so I think also it’s possible that aliens are scientific in a different way. If we’re open to imagining that the developments of science, the levels of knowledge that have been revealed by the process of science, could go in very different ways. If you reran the Earth as an experiment a thousand times (or of course on alien planets), then also the process of science itself could develop in a different order or go down a different path. And what we call science, what we view and find so important as our method of discovering the universe, could be culturally very different on an alien planet.

You know, let me end just by with a silly example. I imagine that when aliens come, once the linguists have figured stuff out that, you know, we’re going to be at the chalkboard talking with their physicists, but do they even have physicists? Do they have creatures who spend their lives investigating these questions? Maybe they have a very different social structure, and who will they send to talk to us? If alien physicists came to earth 500 years ago, we might send our priests or something to them. So it’s funny to imagine. Is there even the alien equivalent of you and me? Who are the alien Daniel and Ethan that we could talk to if they even did arrive?

Daniel Whiteson’s new book, Do Aliens Speak Physics? And Other Questions about Science and the Nature of Reality, is currently available for preorder. It officially goes on sale November 4th, 2025.