Modern physics offers a remarkable lens on reality. In just over a century, it has decoded the architecture of atoms, traced the early history of the universe, and produced laws that seem to hold everywhere, from Earth’s crust to distant galaxies. It is tempting to believe that these theories aren’t just accurate, but inevitable – that any sufficiently intelligent civilization would eventually uncover the same truths.
The author used to believe that, too. But lately, questions have arisen about whether physics is less a window onto universal reality and more a mirror, reflecting the particular kind of minds we happen to have. This unsettling thought emerges when you ask a deceptively simple question: would alien scientists, shaped by a different biology or culture, arrive at the same physics that we have? Or might they develop something that works just as well, but appears utterly foreign – built on concepts and assumptions we would struggle to recognize?
This question sits at the heart of the book, “Do Aliens Speak Physics?”, which imagines various scenarios of first contact, each designed to probe a foundational assumption of modern physics. In developing it, often in conversation with philosophers of science, a surprising realization has formed: many pillars of physics that feel hardwired may actually be contingent. Recognizing this doesn’t weaken science; it may be how we make it better.
The author has spent a lifetime doing physics. When not teaching at the University of California, Irvine, they work at the CERN particle physics laboratory near Geneva, Switzerland, analyzing data from the Large Hadron Collider. A few years ago, conversations with philosophers forced a revisit of a question not seriously considered since student days: what is physics, really?
The Nature of Physics and Its Limitations
At its core, physics aims to explain how the universe works – not just what we observe, but what lies behind those observations. It looks for patterns, builds models that expose hidden structure, and, ideally, distills everything down to a small set of rules from which the rest follows. By that measure, it has been spectacularly successful.
Yet physics never describes the universe in full. It describes carefully chosen versions of it. Consider predicting the path of a comet. In principle, one could account for every gravitational tug, the slow loss of material as ice sublimates, even the way an irregular shape causes the comet to tumble. In practice, decisions must be made about what to include and what to ignore. There is no single correct model – only models that are good enough for the question at hand.
This is true throughout physics. Even our most precise theories rely on approximations and assumptions that make the mathematics tractable. It is not clear that the theories we treat as fundamental truly are. They may simply be effective descriptions that work at human scales. There is no guarantee that, by probing nature ever more finely, we will eventually strike bedrock.
If physics depends on choices – about simplification, representation, and emphasis – then alien physicists might reasonably make different ones. This leads to several compelling hypothetical scenarios.
Questioning Our Understanding of Time and Causality
Imagine aliens arrive on Earth, having mastered interstellar travel. They touch down near Paris. A delegation of linguists and scientists is sent to greet them, hoping for a technological windfall. The delegation returns empty-handed.
The lead physicist explains, “They can’t share their technology because of what will happen 74 years from today.” The implication is disturbing. These aliens do not experience time as a flowing sequence but as a complete structure, something navigable rather than endured. Human physics, by contrast, is built on the idea that the present generates the future, with causes preceding effects. The universe computes itself forward, moment by moment.
But what if that picture is merely a human convenience, rather than a cosmic necessity? We know that any workable physics must obey certain constraints. A universe that allows unrestricted messages from the future quickly collapses into a paradox. However, within those limits, the structure of time may be more flexible than we usually admit.
Hints of this already exist in our own theories. Quantum entanglement links distant particles so that measuring one appears to instantaneously fix the state of the other, despite the fact that no information can be exchanged between them. This alone strains our intuitions. Matters become stranger when relativity enters the picture. Observers moving at different speeds disagree about the order of events. In some frames of reference, one measurement appears to influence another before it occurs.
The standard response is to insist that nothing physically problematic has happened: no faster-than-light signals, no causal contradictions. But that reassurance relies on clinging tightly to a classical notion of causality that quantum mechanics has never fully respected. Some physicists have taken a more radical approach. In so-called retrocausal interpretations of quantum mechanics, future events are allowed to help shape the present. Measurements don’t merely reveal outcomes; they help define them, even backward in time. The universe no longer computes itself strictly step by step.
If aliens had a radically different construct of time, they might adopt such ideas naturally, rather than treating them as unsettling exceptions. And perhaps we may eventually need to do the same.
The Plurality of Scientific Theories
Now, imagine aliens invite us aboard their ship for a scientific conference. Earth sends its brightest minds. We present our best theories. The aliens listen politely, then respond. One group describes a framework that reproduces all known experiments using unfamiliar concepts. A second presents another, incompatible approach. Then a third. Each works. Each is internally consistent. None can be reduced to the others.
Finally, someone asks the obvious question: which one is true? The aliens seem puzzled. “All of them,” they say. “Why choose?”
Human science assumes that competing theories must ultimately fight it out, with only one surviving as the correct description of reality. When multiple explanations fit the data, we design experiments to eliminate all but a single winner. This strategy is powerful and often effective. But it is a preference, not a logical necessity.
Science today often tolerates pluralism more than it admits. Weather forecasting is a striking example. Modern meteorology relies on suites of models, each tuned to different assumptions and scales. These models routinely disagree, and experts decide which to trust depending on context. No single model is treated as the uniquely correct one.
Another example comes from classical mechanics. At school, we learn Newton’s laws as a story about forces pushing and pulling objects through space. But the same motions can be derived in a very different way, by tracking how energy flows through a system, or by assuming that nature somehow “chooses” the path that minimizes a quantity called “action”. To most physicists, these are just alternative ways of doing the same sums.
Philosophers of science, however, would point out that each framework elevates a different concept to center stage – force, energy, optimization – and offers a different account of what, at bottom, is driving the motion. The fact that these pictures cannot be told apart by experiment shows that empirical success alone may not be enough to tell us which account, if any, deserves to be called the “true” one.
This suggests an alternative vision of science – not a march towards a single, final theory, but a toolbox of frameworks, each useful in different situations. Aliens might adopt such an approach from the outset, without ever feeling the need to crown a single description as the truth.
Technology Preceding Scientific Understanding
Finally, imagine that aliens arrive by opening a wormhole. The technology is astonishing. Surely they must possess deep insights into gravity, perhaps even quantum gravity. But what if they don’t?
What if their space-bending technology is the result of millions of years of trial and error rather than theoretical understanding? They know how to build it and how to use it, but not why it works – and they may not care. This sounds implausible only because we are used to thinking of technology as the offspring of science. Historically, the relationship often ran the other way. Humans made steel, glass, and antibiotics long before understanding the underlying chemistry or biology. Cathedrals were built before calculus.
The tight coupling between science and technology that we take for granted is a recent and culturally specific achievement. It is tempting to assume that any intelligent species would be driven to ask “why.” But that urge may reflect human psychology rather than a universal feature of intelligence. Other species might value reliability over explanation, or usefulness over understanding. They could build extraordinary technologies without ever developing anything recognizable as physics – not because they failed to take the next step, but because the step never seemed necessary.
Rethinking Our Assumptions
These scenarios are speculative. But they point to something easy to forget. Physics is the cumulative result of many human choices: about what counts as an explanation, which inconsistencies matter, and which questions are worth asking at all. It reflects our history, our tools, and our values as much as it reflects the structure of the universe.
Recognizing that doesn’t diminish physics. It does the opposite. The more aware we are of the assumptions baked into our theories and methods – about time, causality, truth, and explanation – the more freedom we gain to rethink them.