Lead, South Dakota. About an hour north of my campsite in the Black Hills and just east of the Wyoming border, this little former mining town has been my destination for more than a month, ever since I ran across an obscure event posting online. It is the reason I came this way and why I spent so long exploring the state. And it has hills that would put San Francisco to shame.
It also has one of the deepest gold mines in the country, which is what brought me here. Not the gold, but what they turned the mine into. The deepest, largest, and most accurate neutrino detector in the world. And this one day only, they were giving tours.
For me, an amateur astrophysics nerd extrordanaire, this was better than finding gold.
It would be a whole day of reveling in nerdiness: a series of science talks aimed at adults by the scientists themselves. They had kids activities, too, and I also like cool science demos with household ingredients, but based on the advertisement, I had high hopes that this would be more. I was looking forward to learning and discussing particle physics concepts at a level aimed at an intelligent, adult public. I don’t have a Ph.D. in physics, I’m sorry to say, but I don’t need one to grasp the overarching concepts, and I appreciate when scientists also get a kick out of sharing their research with people who are interested.
With high hopes and unabashed enthusiasm, I arrived the afternoon before “Neutrino Day X” to scope out where the various activities would be held, as they were all around town, where to find parking, wi-fi, that sort of thing.
But first things first. Now that I was back in a town for the first time in a week and a half, my absolute first priority was food. I was so happy to be in an actual grocery store again, with fresh produce and off the powwow’s diet of fried chicken, fry bread, beef stew, and increasingly creative meals from my thinning pantry, that I went a little overboard. Well, at least I ate well for several days!
With the needs of the flesh taken care of, I headed to the visitor center of Sanford Labs (not Stanford) and looked around at their info displays before the crowds were due to arrive the next day. I got a finalized schedule from one of the volunteers who was setting up and asked her for any tips. She said that people start lining up for hoistroom tickets by seven in the morning, so of course, I got there at 6:15. Because I needed to make sure I got on the first tour bus in order to make all the other events I wanted that day.
I had the whole day planned out so as to take the underground lab tour and still attend every lecture, with routes between the different locations mapped out. The town is small and most of the events were somewhere on the main street, but that was still a mile or so long, up—or down—a very steep hill.
In the morning, the next eager beaver showed up around 7:30 and the line didn’t start forming behind us until almost 8. You know how when you want something badly, you overestimate how many other people want it too? Yeah, that was me. When they opened the ticket booth at precisely 8:00, I got ticket number one.
The trolley–it was an actual trolley–took us to the hoistroom. The room where the operator controls the hoist. That was it. So. Yeah.
Someone talked (yelled) for about 15 minutes about the (very loud) turbines and winches that raise and lower the “cages” in the mine chutes, which is how the scientists and all their equipment (and formerly the miners) get to and from the labs.
The way the flyer and schedule were worded, one of the event locations was “Sanford Underground Research Facility,” via shuttle only, and you needed shuttle tickets for the hoistroom tours, the hoistroom being how you get underground, so I thought we were going to actually get to go underground, but apparently not. And the “Underground Facility” was in a building aboveground near the hoistroom. So, that was it. We got to see the winches. Oh, well. That was disappointing, but the rest of the day was still in store.
Next up: a live video chat with the scientists at Fermilab in Chicago. Cindy Joe and Peter Shanehan talked with us on a surprisingly good live video feed from about 350 feet underground, and their colleague Kurt Riesselmann was on site at our end to facilitate.
They explained about the experiment that Sanford Labs and Fermilab are embarking upon together, but before I get to that, a little background will help put it in context.
Like, what is a neutrino detector doing in an old gold mine? And what is a neutrino, anyway?
Well, neutrinos are tiny subatomic particles similar to electrons, but much smaller. They also have no charge and a very small mass, weighing almost nothing. And they are very, very difficult to find because they don’t interact very often with other matter.
So you need an incredibly sensitive detector to pick out even a few, but a detector that sensitive will also pick up a lot of other particles, cosmic rays and the like, and that will mess with the data. Putting the lab a mile underground lets the Earth act as free shielding for the experiment, blocking out all the other particles that are traveling through space so that the detector isn’t getting a lot of static-like interference and can pick up just the neutrinos.
They can get away with this because neutrinos aren’t stopped by a mile of the Earth’s crust. Even if the Earth’s crust were made of solid lead it wouldn’t stop more than a handful of neutrinos. In fact, if you could somehow make a block of solid lead a light year long in every direction—that’s 63,000 times the distance from here to the Sun—that gigantic block of lead would only stop about half of the neutrinos going through it. In science speak, this is what physicists mean when they say that neutrinos “interact weakly.”
In fact, trillions of neutrinos passed through your body in the time it took you to read each word in this sentence, yet in your entire lifetime there is only about a 1 in 4 chance that just one neutrino will interact in any way with a single atom in your body. And don’t worry, if it ever happens, it’s completely harmless to you.
That also means that the vast majority of the neutrinos flying through the neutrino detector will pass right through it and never be detected. Scientists can only detect something if it interacts: if it bumps into another atom or hits an electron or does something, if there is some way, somehow, to know it is there. So even with a really big, super sensitive detector a mile underground, it is only picking up a few of the trillions of neutrinos that are going through it every second.
Although neutrinos are the most abundant particle in the universe after photons (light), they pass right through normal matter without so much as bumping into it most of the time. So, how do they find more of them? Build a bigger, more sensitive detector. Not a particularly original approach, granted, but effective.
Dr. Ray Davis began conducting neutrino experiments in Homestake Gold Mine in the 1960s when it was still an active mine, and the experiments have been getting bigger and more elaborate ever since. And they have been effective. Dr. Davis detected cosmic neutrinos for the first time with those early detectors, winning a Nobel Prize in 2002 for his work, yet there is much that we still don’t know about neutrinos. The current detector, and the experiment they are running with it, called the Large Underground Xenon (LUX) experiment, has been in operation since 2013 and is the most sensitive dark matter detector in the world. Yet it is not nearly sensitive enough.
An international team of more than 1,000 scientists from over 150 institutions in 27 countries are working together to invent the next generation neutrino detector, called the Deep Underground Neutrino Experiment, or DUNE. Yes, many scientists are also science fiction fans.
The basic plan is to use the particle accelerator at Fermilab, outside of Chicago, that is already in place and running neutrino experiments, and redirect it so that it shoots a beam of protons to smash into a graphite target, causing the protons to break up, or “decay,” into smaller particles, including neutrinos that will continue traveling on the original course. Headed through 800 miles of the Earth’s crust all the way to the biggest, baddest, most awesome detector that they have yet to build, at Sanford Labs in South Dakota.
The labs then see what neutrinos they can measure with their new fancy detector and compare that to the information from when they sent it at Fermilab, and can use that to confirm or reject a bunch of different theories, and maybe even get surprised and learn some new stuff. The new detector will also be able to detect neutrinos from neutron stars, supernovae, black holes, and more. Here’s a video of how it will work when it is complete.
This experiment is what Joe, Shanehan, and Riesselmann were telling us about during the live video feed. Sanford Labs is still running the LUX experiment, as well as another called MAJORANA, and other scientists are doing other cool experiments down in the converted mine shafts, like artificially growing the world’s purest copper with electricity and learning about radiation and seismic monitoring and all sorts of things, but the big push right now is to get DUNE up and running.
They broke ground last year and it sounds like (I could be wrong about this) most or all of the funding has already been committed, so the big hurdle at this point is primarily engineering.
Which conveniently brings us to the next talk of the day, “Engineering for Deep Science.” Chris Mossey is Deputy Director for LBNF Fermilab, the facility that will be sending the particle beam from Chicago, IL, 800 miles underground to Lead, South Dakota, and as such is partially responsible for coordinating efforts for this, the largest international science project ever planned on U.S. soil.
“This is going to be the world’s flagship neutrino facility,” Mossey said. “And it’s going to be the first internationally conceived, constructed and operated mega-science project in the United States. Hopefully, it will help us understand better why the universe is the way it is.”
What I took away from his talk was that the extraordinary range of engineering challenges involved in letting scientists do all this and other extremely expensive and complicated experiments has enormous benefits to the public and to our economy. That if you let scientists dream and play at whatever they are interested in, they will frequently run into a case of “I want to do this thing that is currently impossible, so how do we make it happen?”
And they’ll get together with other scientists and engineers and people in all sorts of different disciplines and collaborate and invent new technologies and solutions to do the things they’ve dreamed up, yet those are not single-use technologies.
They are then used by everyone else for all sorts of other things that make our lives better and that create jobs and whole new industries and that fuel our economies in ways never before dreamed of, all because we let scientists play and dream and invent expensive experiments to learn seemingly obscure knowledge. And what they learn then fuels all sorts of other new technologies and creates new dreams and new challenges and the cycle continues.
This is how we got plastic, by the way. And computers, the internet, texting, water filters, cordless medical instruments, hand-held vacuum cleaners, safety grooving on highways, shoe insoles, memory foam mattresses, solar panels, the ear thermometer, scratch resistant lenses, invisible braces, improved protective gear for firefighters, food safety improvements, fire-resistant steel coatings for high-rise buildings, prosthetic limbs, programmable coffee makers, and tons more.
In fact, a great deal of what has been invented or improved upon since the 1960s or so has either been a direct spinoff of technology from NASA and other scientific experiments in a wide variety of fields, or indirectly because it is using the technologies that they created, like laptop computers, water purifiers, industrial sealants, cleaning solvents, LED lights, manufacturing processes, improved home insulation, tracking systems, the whole global satellite network, and much, much more.
As a case in point, Mossy was telling us about some of the engineering challenges unique to the DUNE project. Remember how I told you that the only way in or out of the labs is through the old mine chutes? Well, that isn’t a very big opening. The elevator style cages were meant to carry about 10 guys, not a 62.7′ x 59′ x 216.5′ steel structure.
So they will have to take all the pieces down separately and assemble everything in the caverns a mile underground. So every piece needs to somehow be able to not only fit down the chutes, but then to turn from going downward to going sideways to get out the door at the bottom. Like moving an oversized couch down a hallway and into an apartment with a sharp turn in the doorway. So the engineers are working right now to figure out how to get every beam of steel and every piece of construction equipment down into the mines to build not one, but four, of these:
Yet before they can start getting all of these down there, they will first have to make several of the mining caverns much, much bigger. Which means excavating approximately 875,000 tons of rock over the course of about three years. That’s about the same as eight Nimitz class aircraft carriers, according to Mossey, a retired Navy rear admiral.
And once all the rock is up and the equipment is down and the steel structures are all built, they have to clean the insides of the structures better than you’ve ever cleaned anything in your life, so that not a stray electron is out of place to throw off the delicate instruments and mess with their data.
Then they’ll have to pump down 70,000 tons of liquid argon and keep it at -300 degrees F, day and night, every day of the year. Which means the underground caverns will need intense cooling systems for the liquid cryogens, which means a lot of power, as well as everything else the scientists and support staff would need anywhere else to work and be safe: a cyberinfrastructure, water, lights, ventilation of course, and more.
That’s a lot of engineering challenges. And I have no idea what solutions they’ll come up with, but I have no doubt that they will be eagerly seized upon by a host of other people and industries to make new, better stuff for the rest of us. Because we let the scientists play.
And what they hope to learn from the experiment itself is potentially revolutionary. Not to sound overly-dramatic or anything, but they are hoping to learn nothing less than why our universe and everything in it exists at all.
Cabot-Ann Christofferson told us more about this in the next live video chat from her lab a mile below where we were sitting. Christofferson is a chemist who oversees the copper electroforming that is needed for the MAJORANA Demonstrator Project, the other primary neutrino project that is currently running in Sanford Labs.
So, why do neutrinos matter? Pun intended. Sorry, I couldn’t resist.
Here’s the short version. Everything that you see around you, the people, bananas, the chair you are sitting on, the screen you are reading this on, the light that lets you see, and your eyeballs, everything, is made of matter. And matter is made up of tiny particles like the electrons, protons, and neutrons that make up atoms, which you are probably familiar with from science classes, yet scientists have found lots of other particles as well, including muons, taus, quarks, neutrinos, etc.
Here’s where it starts sounding like science fiction, but I promise this is science fact. All particles have an opposite, usually called an anti-whatever particle. Like the anti-quark, anti-neutrino, anti-tau, except anti-electrons are called positrons. Anyway, when a particle collides with its anti-particle, they annihilate each other leaving only pure energy.
Discoveries by Albert Einstein and other physicists tell us that when the universe was first formed at the Big Bang, particles and their anti-particles, matter and antimatter, were created in exactly equal amounts. Scientists call this symmetry. But if there really were equal amounts, then they all would have just annihilated each other and nothing would have been left but energy. No matter. No universe. No Earth. No people to wonder about this stuff.
Why didn’t that happen? Why are we here to ask? The leading theory is that some particles might behave differently from their anti-particles and therefore not annihilate each other as often as most of the ones we know about, and in fact we already know that quarks don’t do this.
If there were enough particles and anti-particles at the beginning of the universe that behaved differently from their opposites, called asymmetry, it might have been just enough for the entire early universe to be thrown off balance, again, just enough, that even though most of the particles and anti-particles did annihilate each other, a small percentage were left over.
That small percentage makes up the entire universe we see today. (So the original amount of matter must have been incomprehensibly huge before most of it destroyed itself).
What particles could have made the difference? Quarks behave differently from their anti-quarks—in science speak this is called “charge-parity violation,” or CP violation for short—but quarks couldn’t have made a big enough difference. Neutrinos might have.
Because there are a lot of them. I mean A LOT. If you count up all the protons, neutrons, and electrons in the entire universe and multiply that by 1 billion, that’s how many neutrinos there are. So if they behave differently from their opposites, if they have charge-parity violation, that could have made enough of a difference in the early universe that not all the other particles hit their opposites and annihilated each other, leaving some leftover to eventually create us.
This is just one of the big mysteries that physicists are trying to solve: how we came to exist.
The MAJORANA Demonstrator Project is part of that. They are looking for a rare form of radioactive decay called “neutrinoless double-beta decay,” that could confirm this theory that neutrinos played a critical role in the early universe and are why we are here now.
This is the kind of stuff that gets me super excited about physics. The questions themselves fascinate me, and also the fact that people not much different from me are able to think up the crazy experiments needed to actually try to answer some of these kinds of questions. And that other people are able to figure out how to make those experiments happen, making up technologies to do it that don’t yet exist.
I wanted to study physics in college but sadly came to terms with the fact that my math skills weren’t up to par, yet I still eagerly devour these kinds of science-for-the-public events, books, articles, etc. Neutrino Day was definitely my favorite science day event I’ve been to, and the keynote speaker at the end of the day did not disappoint.
Capping off a day about the boundaries of extreme physics research, Ariel Waldman inspired many in the audience with her message that science isn’t reserved just for scientists.
She called her talk, “The Hacker’s Guide to the Galaxy,” and meant that the boundaries of what we think of as doing science are becoming broader. The scientists at the heart of the research will always need a firm educational foundation, but they are not the only ones who can contribute. Anyone with a keen interest, useful skills, and a willingness to help can take part meaningfully in a variety of ways.
She told us about a few examples, including a project that she co-founded, Science Hack Day. In cities all around the world, people are getting together for a two-day-all-night event where anyone excited about making weird, silly or serious things with science come together in the same physical space to see what they can prototype within 24 consecutive hours. No qualifications needed except your own desire to join in. See if there is one coming to your city, or if not, you can help organize one!
If you are interested in contributing more formally to current scientific research projects, check out Space Hack. The site is a directory of ways for citizen scientists (i.e. no formal degree necessary) to aide the researchers. Some needs are as low-key as letting SETI use your your computer’s idle time to analyze radio telescope data. Or you can classify images of sunspots to help predict solar eruptions that could disrupt satellites or our electrical grid. Or comb through photos of asteroids to see if they have a tail and are actually comets. Or go through data from the Kepler space telescope to find planets orbiting other stars. If you identify a planet, you’ll be invited to be a co-author on the discovery paper submitted for publication.
They need people to transcribe the logbooks from the Harvard Computers, a group of women who famously revolutionized star classification and astronomy. And to build an online interactive database of our early spaceflight missions. And to tag the location of pictures taken by astronauts of the Earth at night, to create maps that will assist governments and local authorities in making decisions to reduce light pollution. Many projects need help from people like you and me. This isn’t playing around with some cheap, DIY science kit. This is being a part of real, cutting-edge science.
For those already working in the sciences who want to broaden their field of research, NASA Innovative Advanced Concepts funds interdisciplinary, often radical solutions to current aeronautics challenges. Just browsing through the current and past projects was fun and the awesome ideas people have come up with renewed my hope in our ability to tackle the problems we face today with incredible solutions that I can’t even imagine but that someone out there is working on.
Waldman herself embodies her message. She has no formal science background but sits on the council for NASA Innovative Advanced Concepts and works to promote individual and community involvement in furthering science and space exploration in clever new ways.
At the end of her talk she fielded questions from the audience. The very last question asked was about when or how or what it would take to get a manned mission to Mars. I don’t remember the question exactly, but I do remember her answer as it both impressed and inspired me.
She started by mentioning how most people don’t realize the level of technical difficulties involved—that getting to Mars is not just like going to the Moon but a little farther. It is a whole new level of challenge. And though we don’t currently have the technology to be able to meet all the challenges involved, it is realistically within our reach in the near future. But not by any one country alone.
It will take the resources and minds and determination of many countries working together. Just as the nation banded together in the ’60s to put a man on the Moon, the entire world will need to band together to send humans to Mars. So that if we do accomplish this feat, it will mean that we have managed to learn how to put aside or overcome many of our differences and work together on such a resource-intensive and long term project that getting to Mars will be a testament to our growth as a species, and this gives her hope for the future of humanity.
And that, my friends, gives me hope as well.
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If you are interested in exploring any of this more, check out:
When we left Earth The Discovery Channel documentary that inspired Ariel Waldman to start getting involved in NASA public relations.
Hidden Figures Waldman also recommended this movie and I enthusiastically concur. An incredible and inspiring untold true story about three women at NASA who were instrumental in one of history’s greatest operations – the launch of astronaut John Glenn into orbit.
Another directory of online collaborative research is Zooniverse, with projects in biology, climate, history, literature, nature, medicine, the arts, and much more.
To learn more about neutrinos and the mysteries they might solve, visit All Things Neutrino.
Here’s an animation that explains how they make a beam of neutrinos.
To see live data from another neutrino detector, called NOvA, that is working on a different experiment in Ash River, MN, see NOvA live event display. The setup here is similar to the DUNE experiment, where Fermilab shoots a beam of neutrinos 500 miles through the Earth to Ash River, but this experiment is trying to learn different things about neutrinos. Here is a good video describing the NOvA experiment. And a time-lapse video of the NOvA detector construction.
Also, next year’s Neutrino Day 11 is well worth a visit. It’s the second Saturday in July every year. Maybe you’ll see me there!