If we ever meet aliens, would their physics be the same as ours? While this might seem like a purely hypothetical, abstract question, it has profound consequences for what the pursuit of scientific truth actually is. Professor of Physics and Astronomy at the University of California, Irvine, Daniel Whiteson, argues that if alien physics is different from ours, then our theories are not as objective and universal as we often believe.

The boldest claim of modern physics is not due to Einstein or Heisenberg. It’s Newton’s great leap to extend the reach of physics from Earth to the heavens. The same laws of physics that apply to apples, he claimed, should also govern the motion of the moon and the planets. While biology is limited to describing action on Earth, physics since Newton purports to describe the Universe. The ambition of this project is staggering: the laws of physics deduced by humans—who have hardly left our tiny little cosmic rock—should somehow determine how the entire cosmos interacts and evolves.

And yet this is not hubris—it is well supported by the data. Distant galaxies do seem to obey the same rules that apply locally. The second law of thermodynamics, which was worked out by nineteenth-century scientists experimenting with primitive engines and flasks of gas, has recently been verified to also be valid when massive black holes merge more than a billion light-years distant.

But would the denizens of those galaxies agree with humanity’s description of physics? Does the universal applicability of our laws mean they must also be discovered by others? If aliens ever visit us, could physicists achieve what biologists could never dare to hope for, an interstellar scientific conference? Could aliens help leap us forward a thousand, million, or billion years into our scientific future? Is there a single scientific path for civilizations to walk?

Many physicists, including the late Carl Sagan, make a leap well beyond Newton’s bold claim, arguing that, because our laws seem to hold everywhere, they must be discovered by everyone. String theorist Thomas van Riet, for example, is sure that “aliens will discover string theory. I don’t even doubt it.”

It’s very tempting to believe that unraveling the secrets of nature is a universal project that would be shared by the scientists of alien species across the galaxy. It’s delicious to imagine that if our species met up we could share notes on this glorious galactic journey of discovery, and crack some of the puzzles that continue to befuddle us, about the origins of the Universe, or the conflicts between quantum theory and relativity.

But is Sagan’s leap as well-justified as Newton’s? It’s awfully flattering to imagine that our human scientific tradition has unearthed physical laws which bear no trace of our humanity, which any intelligent species would have to similarly uncover. Without examples of alien scientific traditions to compare to, what justifies this extrapolation from the singular example of human science? Are human physics and math the only way to think about the Universe—­or are they just the only way we can imagine it?

A lesson from biology

Nothing would be as illuminating as spending an afternoon at a chalkboard with alien visitors. But until that day arrives, we can only study our local example for clues that it is the only way forward, or that it might be a product of our biology, psychology, or pure random history.