Last Saturday I went to the march for science here in Philadelphia. I was late and it was raining. By the time I arrived marchers were already streaming away from Penn’s Landing, the ink on their signs running in the rain. But a committed core sat huddled under umbrellas and plastic raincoats to hear speeches by a pediatrician, an environmental scientist, a paleontologist, a scientific entrepreneur, and a doctor, among others. Some of the marchers wore white lab coats. Others carried earth globes, or nerdy signs with formulas. One woman had a sign that said “I am not a scientist but I play one in this march.”

When I was a girl, I loved to visit the lab where my father worked as a molecular biologist. I didn't visit very often but I have vivid memories of it. I remember the strange chemical smell, the cluttered lab benches (pipettes, test tubes, note pads, a soft drink…) and the high stools. He would show me the freezers where they stored samples in little round glass Petri dishes, enormous freezers with large silver handles that you could walk into. He introduced me to his colleagues who wore odd aprons and latex gloves. Later on, early in medical school, I toyed with the idea of following in his path. I signed up to assist a researcher who spend his time looking through an electron microscope, something novel and cutting edge at the time, a device that allowed you to peer deep, deep inside cells and view the three-dimensional architecture of things like ribosomes and mitochondria. He was fascinated by it. I thought it was the most boring thing I had ever done.

It was not until much later when as a graduate student I took courses in epidemiology and in the social and behavioral determinants of health, that I discovered that there was a different kind of science, a science that was not necessarily based in the laboratory. It was a science about why some populations are healthier than others. It was a fascinating science because of its ambitious comprehensiveness (from biology to sociology) and its impatient commitment to action (what can we do with this?). It was the science of public health.

I won’t deny the beauty and intellectual appeal of understanding for its own sake. Not all science needs to be utilitarian. In this science is similar to art. But if we want to manage and change our world so that it is better for all of us we need to understand it. This understanding is what science is about. Purposeful action cannot happen without understanding. Public health is a perfect example of this.

Several of the speakers at the march last Sunday spoke about the importance of funding science, of all that science has accomplished and done to make our world better, of the dangers to our planet and our world as we know it if we ignore science and defund it. They spoke about science as an economic engine.

All this is true. But in my mind the most important thing about the emerging movement in defense of science is not about funding for science or supporting the institutions that depend on it. It is not about technology and economic growth. It is about the basic principles of science: the search for truth, the constant questioning of assumptions, and the core belief that knowledge is key to effective action.

It was refreshing to see scientists as common people in the street. It was refreshing to see common people who are not scientists supporting science. Science is one of the many things we can do as a society to improve our lives and make our world better. It is not better or more important than other things we do, but it is critical to our well-being, our survival, and our desire to create a better world for all of us.