
Scientific reproducibility—the ability of researchers to obtain consistent results when repeating an experiment—sits at the heart of the scientific method. During my years at the bench and later as the leader of an Institute, it became clear that not all sciences struggle equally with this fundamental principle. Physics experiments tend to be more reproducible than those in life sciences, where researchers grapple with what many call a “reproducibility crisis.” Understanding why reveals something profound about the nature of these disciplines.
The State of Reproducibility Across Sciences
A 2016 Nature survey of over 1,500 researchers revealed the scope of the challenge: more than 70% of scientists have failed to reproduce another researcher’s experiments. The rates varied by field—87% of chemists, 77% of biologists, and 69% of physicists and engineers reported such failures. Notably, 52% of respondents agreed that a significant reproducibility crisis exists.
These numbers tell us something important: reproducibility challenges exist across all scientific disciplines, but they manifest with different severity. Physics hasn’t been immune to these issues, but it has been affected less severely than fields like psychology, clinical medicine, and biology. This isn’t a story of success versus failure—it’s a story of different sciences confronting different kinds of complexity.
The Physics Advantage
When a physicist measures the speed of light or the charge of an electron, they’re studying fundamental constants of nature. These values don’t change based on the lab, the researcher, or the day of the week. A particle accelerator in Geneva produces the same collision energies as one in Illinois. The laws governing pendulum motion work identically whether you’re in Cambridge or Kyoto.
This consistency extends beyond fundamental constants. Physics experiments typically involve controlled, isolated systems where researchers can eliminate or account for confounding variables. A physics experiment might study a single particle in a vacuum, far removed from the messy complexity of the real world. Precise measurement tools, refined over centuries, allow astonishing accuracy. NSF’s LIGO, for instance, can detect gravitational waves by measuring changes smaller than one ten-thousandth the width of a proton—equivalent to noticing a hair’s width change in the distance to the nearest star. The centuries of theoretical understanding that physics has developed makes the field less susceptible to reproducibility failures.
The Life Sciences Challenge
Life sciences researchers face a fundamentally different landscape. They’re not studying isolated particles obeying immutable laws; they’re investigating complex, adaptive systems shaped by evolution, environment, and chance.
Consider a seemingly simple experiment: testing how a drug affects cancer cells. Those cells aren’t uniform entities like electrons. Research has revealed extensive genetic variation across supposedly identical cancer cell lines. The same cell line obtained from different sources can show staggering differences—studies have found that at least 75% of compounds that strongly inhibit some strains of a cell line are completely inactive in others. Each cell line has accumulated unique mutations through genetic drift as they’re independently passaged in different laboratories.
The cells’ behavior changes based on how many times they’ve been cultured, what nutrients they receive, even the material of the culture dish. Research has documented profound variability even in highly standardized experiments, with factors like cell density, passage number, temperature, and medium composition all significantly affecting results. The researcher’s technique in handling the cells matters. Countless variables play roles that are difficult or impossible to fully control.
This complexity manifests in several ways:
Biological variability is the norm, not the exception. No two mice are identical, even if they’re genetically similar. Human patients are wildly variable. A treatment that works brilliantly for one person may fail completely for another with the “same” disease.
Emergent properties mean that biological systems exhibit behaviors that can’t be predicted simply by understanding their components. You can’t predict consciousness by studying individual neurons, just as you can’t predict ecosystem dynamics by studying single organisms.
Context dependence is paramount. A gene doesn’t have a single function—its effects depend on the organism, developmental stage, tissue type, and environmental conditions. The same protein can play entirely different roles in different contexts.
Reframing the “Crisis”
It’s worth questioning whether “crisis” is the right word for what’s happening in life sciences. Some researchers argue that the apparent reproducibility problem may be partly a statistical phenomenon. When fields explore bold, uncertain hypotheses—as life sciences often do—a certain rate of non-replication is expected and even healthy. A hypothesis that’s unlikely to be true a priori may still test positive, and subsequent studies revealing the truth represent science’s self-correcting mechanisms at work rather than a failure.
The complexity of biological systems means that two experiments may differ in ways researchers don’t fully understand, leading to different results not because of poor methodology but because of hidden variables or context sensitivity. This doesn’t excuse sloppy work, but it does suggest we should expect life sciences to have inherently lower replication rates than physics due to the nature of what’s being studied.
The Methodological Gap
These fundamental differences create practical challenges. Physics papers often provide enough detail for precise replication: “We used a 532nm laser with 10mW power at normal incidence…” Life sciences papers might say “cells were cultured under standard conditions”—but what’s “standard” varies between labs. One lab’s “gentle mixing” is another’s vigorous shaking.
The statistical approaches differ too. Physics can often work with small sample sizes because measurement precision is high and variability is low. Life sciences need larger samples to overcome biological variability, yet often work with small sample sizes due to cost, time, or ethical constraints. This makes studies underpowered and results less reliable.
Moving Forward
Recognition of reproducibility challenges has sparked essential reforms. Pre-registration of studies, open data sharing, more rigorous statistical practices, and standardized protocols all help. Some fields are developing reference cell lines and model organisms to reduce variability between labs. Journals are implementing checklists to ensure critical details are reported. These efforts are making a real difference.
Yet we must also accept that perfect reproducibility may be neither achievable nor always desirable in life sciences. Biological variability is a feature, not a bug—it’s the raw material of evolution and the reason life adapts to changing environments. The goal shouldn’t be to make biology as reproducible as physics, but to develop methods appropriate for studying complex, variable systems and to be transparent about the limitations and uncertainties inherent in this work.
Understanding the Divide
The reproducibility divide between physics and life sciences doesn’t reflect a failure in the life sciences. It reflects the reality that living systems are profoundly different from the physical systems that physicists study. Both approaches to science are valid and necessary; they’re simply tackling different kinds of problems with appropriately different tools.
Even physics, with all its advantages, sees nearly 70% of researchers unable to reproduce some experiments. The difference is one of degree, not kind. All science involves uncertainty, iteration, and gradual convergence on truth through many studies rather than single definitive experiments.
Understanding these differences helps us appreciate both the elegant precision of physics and the challenging complexity of life. And perhaps most importantly, it reminds us that the scientific method must be flexible enough to accommodate the full diversity of natural phenomena we seek to understand—from the fundamental particles that never change to the living systems that are constantly evolving.





