A couple years ago, I was at a house party in Ithaca where I met a first-year grad student who asked me what I was studying.

“Aerospace engineering,” I said.

“Cool,” he replied. “Just don’t ever work for Lockheed Martin.”

(Ha.) I asked him why not. His answer: “They build weapons.”

This student was also extremely frightened of the “Big Dog” robot, which had just exploded onto the Internet in a series of awesome demonstration videos on YouTube. Why? “Just imagine what the military will be doing with that. They’re funding it, you know.” Did he have any specific examples or concerns? No. And I pointed out how invaluable such a robot would be in, say, rugged-terrain search and rescue or disaster response efforts. But none of that mattered, this student insisted, because the project received military funding. Somehow, in his mind, if the Red Cross shelled out millions for the development of Big Dog, it would be okay – but not if that money came from the US Army.

This attitude struck me as extremely naive. (And not just because this first-year was wearing a chai.) Some of the best work in science, engineering, and medicine gets funding from the military, because the military is naturally interested in those things. But I don’t think that means that even the pacifists among us should abandon all those lines of inquiry. You see, I believe in the adage that technology is neither good nor evil – it’s how we choose to use it that defines our goodness or evilness.

I have long since come to terms with the fact that many of the engineering challenges and scientific problems that I want to solve have both military and civilian applications. I want to, for example, land robots on Europa or Titan. Doing such a thing will require precision guidance and pointing systems – exactly the same kinds of systems that could control ballistic missiles or smart bombs. Some of the same technologies that let us aim the Hubble telescope precisely enough to image galaxies billions of light-years away can aim the airborne cannons on an AC-130. The rockets that bring astronauts to the International Space Station, a peaceful, collaborative venture between many nations, operate on the same principles and use the same fuels and control systems that go into ballistic missiles. The key difference in all of these cases is in where we, the human operators of such devices, point them to go.

To take an extreme example: the most devastating weapon we are capable of producing is the nuclear warhead. It is a terrible weapon, and nobody in their right mind would tell you otherwise. Some activists out there are so vehemently set against this weapon that they oppose all use of nuclear power and all refinement of nuclear isotopes. But here’s the thing: high-grade plutonium isotopes are what power all interplanetary probes to the outer Solar System! (Beyond about Mars orbit, sunlight is too weak for solar panels to provide enough power for a spacecraft.) Our country has stopped refining high-grade plutonium, and this is actually a big problem in the planetary science community. Again, I want my Europa and Titan landers…and I can’t have them without a stash of plutonium-238!

(For those astute readers who point out that Pu-238 isn’t weapons-grade plutonium, I would argue that the refining techniques are the same. And, for good measure, here’s one of the most peaceful people ever to walk the face of the Earth explaining a constructive use of the nuclear weapons themselves. Though nowadays we view that concept as not very practical, the next iteration might be antimatter-powered rockets capable of taking humans across light-years – but these would be even more destructive if used as weapons.)

In my doctoral research, I worked on new technologies for spacecraft. Fortunately for my moral ideals, flux-pinning interfaces for modular spacecraft are something that we had a hard time coming up with direct military applications for. Nevertheless, they may exist: we thought of looking for a way to develop a device that uses flux pinning to grab onto a target spacecraft without touching it – tractor-beam style. That I am sure that DARPA would be interested in. We did even end up pursuing that idea down a related, non-flux-pinning line to a small-scale proof-of-concept demo. (Our target application was rescuing derelict or malfunctioning satellites.)

Recently, I heard an Air Force colonel refer to GPS, which is a military-developed technology, as a “weapons system.” Now that I’ve gone from university research into the commercial spacecraft industry, I contribute to systems like GPS satellites, so this observation hits close to home. How many people out there using Garmins or iPhones or Google Maps would have thought that they were using something that the military considers to be a weapons system? GPS guides aircraft, boats, and cars throughout the civilian community. It gives researchers a powerful tool to advance geoscience. (Did you know that nowadays we directly measure continental drift speeds with GPS?!) And keep in mind that GPS is what gives us the capability for automated farm equipment to efficiently produce more food, or aid workers to reach remote destinations, or emergency responders to locate missing people and map out disaster zones. I am more than happy to contribute to those endeavors!

So, do we use our knowledge of particle physics to make the most devastating weapons the world has ever known, or do we use it to power the probes that will help explain our origins and find our place in the universe? For me, the answer is clear; but it is also clear that science isn’t necessarily good or evil. (Neither are scientists, for that matter.) Making it one or the other is entirely up to human decisions.