Physics of Life

Biological physics, or the physics of living systems, brings the physicist’s style of inquiry to bear on the beautiful phenomena of life. Physics of Life—the National Academies’ first decadal survey on biological physics—presents a compelling vision for the next decade of science across the enormous range of phenomena encountered in living systems. The report makes recommendations about education, funding, and building a more inclusive community.



What is Biological Physics?

Biological physicists search for new, physical explanations for biological processes at both the microscopic (e.g. the function of molecules and cells) and macroscopic (e.g. the movement of swarms and the dynamics of ecosystems) levels.  They start by asking themselves,“What are the essential physical principles that enable the remarkable phenomena of life?”

Work in biological physics expands our ability to understand and explore the living world and has the potential to change our view of ourselves as humans.  Research in the field directly contributes to the scientific understanding underpinning a range of applications such as vaccine development, drug design, and robotics.  Moreover, many new developments in biological physics are deeply connected to progress in other fields, across physics, biology, and chemistry.

Biological physics has seen rapid growth as a field in recent years.  Over the past two decades, the number of PhD theses in biological physics has roughly tripled, with current numbers comparable to other subfields in physics.  This leads to a central conclusion of this report:

Biological physics now has emerged fully as a field of physics, alongside more traditional fields of astrophysics and cosmology, atomic, molecular and optical physics, condensed matter physics, nuclear physics, particle physics, and plasma physics.

Key Science Questions for the Next Decade

Organisms have to accomplish various tasks—for example, how to sense the environment, or how to move toward sources of food—and carrying out these tasks requires them to solve physical problems. Developing precise physical explanations for how organisms achieve these tasks is one of the central problems in biological physics.

Examples include:

  • Energy Conversion: From quantum dynamics in the first steps of photosynthesis to the classical mechanics of swimming and flying.
  • Mechanics, Movement, and the Physics of Behavior: From swimming bacteria and crawling worms to walking, flying, and robotics.
  • Sensing the Environment: From counting photons on a dark night to counting molecules in the environment and sensing tiny forces and displacements in the inner ear
  • Structures in Space and Time: From the assembly of viruses to growth and division in bacteria, and how the zebra gets its stripes.

Learn more in Chapter 1 of the report

Organisms and even individual cells need information about what is happening in their environment, and they need information about their own internal states. Understanding the physics of living systems requires us to understand how information flows across many scales, from single molecules to groups of organisms. The search for the physical basis of information transmission in living systems has led to foundational discoveries, pointing to new physics problems.

Examples include:

  • DNA Sequences: Efforts to understand how information within DNA is copied so reliably from one generation to the next, how is it “read” by the cell, and how it can be rewritten drive the development of new experimental tools and new Molecular
  • Concentrations: Experimental methods from physics have combined with those from chemistry and biology to provide an unprecedented ability to observe and manipulate molecular signals in living cells. Theoretical approaches elucidate the limits to molecular signaling and strategies for signal processing.
  • The Brain: The exploration of information flow in the brain has led to remarkable experimental methods for monitoring the electrical activity of neurons, an understanding of the molecular basis for this activity, and to a broad range of theoretical ideas about how information is represented and why.
  • Communication and Language: The biological physics community’s exploration of communication and the search for common physical principles spans from hydrodynamic trigger waves to language, from song birds to information-based search, and more.

Learn more in Chapter 2 of the report

Complex interactions at the cellular or molecular level can lead to unexpected results at much larger scales. How these “emergent” phenomena occur in livings system, how emergent phenomena of life are different from inanimate systems, and how to describe these phenomena through statistical mechanics are key areas of interest in biological physics.

Examples include:

  • Protein Folding, Structure, and Function: Dramatic progress in experimental methods for determining the structure of proteins, down to the position of every atom, sharpen theoretical questions about how these structure emerge from interactions among amino acids, and how the constraint of structure formation leaves its imprint on amino acid sequences.
  • Chromosome Architecture and Dynamics: Theory and experiment are coming together to understand how 10 feet of DNA pack into the tiny nucleus of every cell, the influence of this packing on cellular function, and the special state of matter formed by the chromosome.
  • Phases and Phase Separation: The startling discoveries of phase separation in cell membranes and cytoplasm have swept through the biological physics community, and the biology community more broadly, raising new questions and promising implications for medicine.
  • Cellular Mechanics and Active Matter: Biological physics builds bridges between the complex molecular components of a cell and its organized macroscopic movements. Theory and experiment meet in this arena of “active matter,” with implications for problems ranging from the development of embryos to the behavior of tumors and stem cells, potentially leading to new advances in cancer treatment.
  • Networks of Neurons: The effort to understand collective behavior in networks of neurons continues to occupy a significant part of the biological physics community, as experimentalists develop new instruments for quantitative exploration of network dynamics and theorists use neural networks as a source of new problems in statistical mechanics.
  • Collective Behavior: The striking collective behaviors in animal groups – from flocks of birds and swarms of insects to nest building ants and termites - provide examples of new physics, new kinds of ordering and surprising dynamics.

Learn more in Chapter 3 of the report

Making quantitative predictions about the behavior of a living system requires knowing many numerical facts, such as how many kinds of each relevant molecule are inside a cell and how strongly these molecules interact with one another. Understanding how organisms adapt, learn, and evolve around these parameters is important for many different problems in biological physics.

Examples include:

  • Adaptation: Our eyes adjust automatically to the brightness of the sun or the dark of night, and similar forms of adaption occur in all cells as they respond to the environment. New forms of adaptation continue to be discovered, often predicted by theory, and adaptation provides an example of how living system find the “sweet spot” in adjusting their mechanisms to achieve functional behaviors; theory gives new views of this general problem.
  • Learning: Learning is studied at all levels, from molecular mechanisms to human behavior, and the biological physics community engages across all these scales, often trying to build bridges. Theory shows how molecular complexity can support function, how the “aha!” effect can be understood as a phase transition, how the dynamics of learning is linked to the variability of behavior, and more, in each case connecting with new quantitative experiments.
  • Evolution: Biological physicists have explored evolutionary dynamics in theoretical studies, in laboratory experiments, and in surveys of the natural experiments that occur in viral populations across the world. This work provides tools for monitoring the spread of diseases, including covid-19, and identifies regimes in which evolution is predictable, contributing to the design of vaccines and changing our views of life more broadly.

Learn more in Chapter 4 of the report

Supporting the Field

Supporting future biological physicists at the undergraduate and graduate level is essential for the health of the field.  Even at well-resourced institutions, physics students can emerge with a degree and not even know that biological physics exists as a field.  Therefore, the report makes the following recommendations for physics departments, universities, and funding agencies:

  • Recommendation: All universities and colleges should integrate biological physics into the mainstream physics curriculum, at all levels.
  • Recommendation: University and college administrators should allocate resources to physics departments as part of their growing educational and research initiatives in quantitative biology and biological engineering, acknowledging the central role of biological physics in these fields.
  • Recommendation: Federal funding agencies should establish grant program(s) for the direct, institutional support of graduate education in biological physics.

To learn more and for a complete listing of the report’s recommendations related to education, check out Chapter 8 of the report.

Research in biological physics is supported by multiple agencies and foundations, but this support is fragmented, obscuring the breadth and coherence of the field. The Physics of Living Systems program in the Physics Division of the National Science Foundation (NSF) is the only federal program that aims to match the breadth of work in the field.  However, funding levels are dangerously close to the minimum needed for the health of the field.    To support the field of biological physics, the report makes the following recommendations for funding agencies:

  • Recommendation: Funding agencies, including NIH, NSF, DOE, and DoD, as well as private foundations, should develop and expand programs that match the breadth of biological physics as a coherent field.
  • Recommendation: The federal government should provide the National Science Foundation with substantially more resources to fulfill its mission, allowing a much needed increase in the size of individual grant awards without compromising the breadth of its activities.

To learn more and for a complete listing of the report’s recommendations related to funding, collaboration, and coordination, check out Chapter 9 of the report.

Improving attitudes and policies toward immigration, race, and gender is critical for addressing broader issues of justice and equity in the stewardship of resources for biological physics.

Science in the United States has long benefited from the influx of talented students and scientists from elsewhere in the world.  However, discussions of U.S. policy toward international students and scientists are being driven by concerns about national and economic security. Since 2016, applications to U.S. physics graduate programs from international students have decreased.  To support international students, the report recommends:

  • Recommendation: All branches of the U.S. government should support the open exchange of people and ideas. The scientific community should support this openness by maintaining the highest ethical standards.
  • Recommendation: Federal agencies and private foundations should establish programs for the support of international students in US PhD programs, in biological physics and more generally.

Inequalities of opportunity have an especially large impact on physics education.  The field of biological physics should aim to welcome, support, and nurture talented young people from around the world and from U.S. citizens of all ethnic groups.  In particular, the report recommends:

  • Recommendation: Federal agencies should make new resources available to support core undergraduate physics education for under-represented and historically excluded groups, and the integration of research into their education.
  • Recommendation: Recognizing the historical impact of HBCUs, MSIs, and TCUs, faculty from these institutions should play a central role in shaping and implementing new federal programs aimed at recruiting and retaining students from under-represented and historically excluded groups.
  • Recommendation: In implementing this report’s recommendations on introductory undergraduate education and its integration with research, special attention should be paid to the experience of women students.

To learn more and for a complete listing of the report’s recommendations related to building an inclusive community, check out Chapter 10 of the report.

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