In recent years, John Eiler has partnered with colleagues in disparate scientific fields to make discoveries in paleontology, archaeobiology, atmospheric chemistry, climatology, martian geology, and more. Along the way, he has helped develop and refine instruments that reveal previously hidden facets of chemistry, and opened up new areas for scientific exploration.
“My inclination is to be constantly in motion and working in a segment of the scientific community where I can create something that really feels new to me,” Eiler says.
Jonas Zmuidzinas’s new favorite saying is a phrase that’s been running through his mind a lot lately. A physicist at Caltech who develops instrumentation for use in astronomy, he spends an inordinate amount of his waking hours thinking about noise—but not in the way you might expect. For the average person, thinking about noise might mean trying to ignore the loud neighbors on a Sunday morning or using sound-cancelling headphones on a flight full of babies.
But for many scientists and engineers, a broader definition also assigns the term to the fluctuations in a measured signal that can obscure or reduce its clarity. “For people like myself who build instruments and detectors, noise is at the heart of what we do,” says Zmuidzinas. That’s because in engineering, for example, fluctuations, or noise, can arise from the random motions of atoms or electrons, and can manifest as heat or electronic static. And that can lead to malfunctioning machines. A clearer understanding of noise sources and ways to minimize it in circuits can lead to more efficient microchips and to telescopes that are capable of probing structures in the universe that were previously beyond reach.
“We listen for changes in the separation of mirrors over the 4-kilometer length of each laser-interferometric detector. But thermal energy in the 0.4 millimeter diameter glass strings that hold up 40-kilogram mirrors also causes ringing sounds that we call ‘violin modes.’ And a hiss comes from the quantum nature of the light: fluctuations in the nothingness of empty space that interfere with our pure laser beam.”
Rana Adhikari, professor of physics, talks about noises from the Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors. The aim of LIGO is to measure the stretching and squeezing of space-time. Scientists listen to the detector outputs—which are sometimes disturbed by things from the earth, such as earthquakes or traffic—using headphones.
When you have a question about your health or your finances, you go to a doctor or an accountant for advice; you figure they have the knowledge you need to get the answers you’re looking for. But what about when you’re wondering where to go for dinner in a new city? Rather than hiring an expert chef to individually rate each restaurant—a pricey and time-consuming endeavor—you’d probably find it far more practical and efficient to trust the recommendations of the thousands of local diners who’ve already voluntarily rated the restaurants online.
Today, crowdsourcing—in which many individuals work toward the collective goal of narrowing down a large amount of information—has indeed made it easier to choose a good restaurant or pick a movie you’ll likely enjoy. But the concept has also found an application in areas of research where numerous scientists have collected far more data than they could ever analyze on their own.
By taking this data to the crowd, researchers at Caltech have found a way to engage the public while also allowing so-called citizen scientists to investigate a variety of research topics—from very tiny cells on Earth to massive star clusters in our galaxy.
“Experiments in T5, one of the GALCIT Hypersonics Group facilities, begin with a siren…to alert the building. Sometimes it’s mistaken for an earthquake warning. A few seconds later the tunnel fires, accelerating gas to the velocities required to simulate planetary entry flows. The gun shot-like sound and vibrations can be heard and felt through the building.”
Joanna Austin, professor of aerospace, uses pistons and explosives in large test tunnels to compress gases. She studies the mechanics involved in compressible flows, which come into play in problems ranging from the logistics of a spacecraft’s entry into a planet’s atmosphere to the hows and whys of volcanic eruptions.
For their 1966 song, “Good Vibrations,” the Beach Boys assembled an unusual mix of instruments—including a jaw harp, a cello, and an Electro-Theremin—to produce one of their biggest hits. By arranging sound waves in a unique and particular way, they were able to elicit a positive response.
Many doctors and researchers have the same goal. After all, the same “excitations” that helped the Beach Boys usher in an era of feel-good pop—the sound waves that propagate through air and water, bringing notes of music to our ears—are also noninvasively able to explore body tissues, helping to visualize babies in the womb, heal back pain, or even deliver chemotherapeutics to targeted tumors.
“The tsunami causes the ionized gas that is out there to resonate — ‘sing’ or vibrate like a bell.”
Edward C. Stone, the David Morrisroe Professor of Physics, characterizes the sounds of “tsunami waves” that helped signal Voyager I’s entrance into interstellar space. These waves of pressure are caused by coronal mass ejections from the sun. Stone is the project scientist for the Voyager mission based at Caltech.
Today, when there is an outbreak of disease, the first reports of it are likely to be online, through Facebook or Twitter. And as word in cyberspace goes viral, it can map closely to the spread of the actual virus in the physical world. That’s the conclusion of NYU researcher Rumi Chunara (BS ’04), whose paper analyzing Twitter and other online activity surrounding the 2010 outbreak of cholera in Haiti made waves in the public health world.
The “noise” depicted on the cover of the June issue of E&S magazine is a screenshot from a video representation of Richard Wagner’s “Ride of the Valkyries,” which is played at ear-splitting volume at 7 a.m. on the dot every morning during finals week at Caltech. The video above was created for E&S by motion-graphics designer Ryan Luse.
Earthquake-prone Southern California would benefit greatly from having highly accurate ground maps of shaking activity during and after earthquakes—all that’s required is the installation of professional-grade seismometers covering every block. Unfortunately, the units cost several thousand dollars each, so the plan is unlikely at best.
That’s why, in 2011, Professor of Geophysics Rob Clayton decided to get the crowd involved, creating the Community Seismic Network (CSN). The network asked residents of the greater Pasadena area to volunteer to host small, inexpensive seismic sensors in their homes. After being plugged into the volunteer’s home computer, the sensor—which is only about the size of a loaf of bread—begins sending information about seismic events to the CSN researchers.
The CSN is a more passive form of crowdsourcing. Ordinarily, the sensors just sit in the corner of someone’s house recording data and waiting for a seismic event to happen, but when an event occurs, the sensor’s little on-board detectors will detect movement and send a notice—or “pick”—to researchers via the attached computer. “When there is an event, we get hit with a bunch of picks coming in that contain the amplitude of the event, and from that we can make a map of ground acceleration over the entire region covered by the network,” he says.
Maps like these are important guides for first responders like medical staff and firefighters; since the region with the most severe shaking is often the region with the most damage, the ground acceleration map could help responders decide which area is in the greatest need of immediate help. And the more volunteers that offer to host a sensor, the more accurate the map can be.
“We want to have a high density of sensors in the area because we believe that the kind of acceleration from an earthquake varies on a scale of one kilometer—so if we’re a kilometer apart, you’re going to experience a different acceleration than I am,” Clayton says. “Oftentimes people try to attribute irregular patterns of damage to poor building materials, and although that’s a factor, I also think it’s because the ground shakes differently in different places.”
So far, the CSN has distributed more than 500 sensors in the greater Pasadena area—and Clayton and his colleagues are working on new projects that will expand the sensors’ reach even further. For example, sensors are now housed in 100 schools in the L.A. Unified School District with the goal of expanding to all of the more than 1,000 schools in the district.
In order to get a broader reach, Matt Faulkner, one of Clayton’s former graduate students, has been working on an app to exploit the accelerometers that are already installed on most cell phones for purposes including fitness tracking and gaming. “The initial problem with these accelerometers is that if I drop the phone to the floor, that is larger than an earthquake is going to put it through. So simple motions you can do to a phone cause it to have a signal that is larger than the thing you’re trying to measure,” Clayton says. But Faulkner found a clever way to develop algorithms that can separate anthropogenic motions—like running or riding a bike—from earthquake motions.
The app hasn’t yet been fully deployed, but if Clayton and his colleagues could get seismic information from every cell phone in Los Angeles, they project it would give the some of most detailed information about earthquakes ever made available.
“Sometimes the general idea of trusting crowdsourcing during a natural disaster can make problems,” Clayton says. “Often, people talk about only the worst damage and only the things that are most out of the ordinary, and the same thing is true of earthquakes. If you rely on eyewitness speculation, they can say, ‘Well, I wasn’t personally affected, but I saw lots of damage up there.’ That doesn’t work, but having actual sensors in the crowd is part of the solution.”
“It sounds kind of like a cross between a car alarm and an angry squirrel, with some drums in the background.”
Ralph Adolphs, Bren Professor of Psychology and Neuroscience and professor of biology, describes the sound of the pulse sequence used for functional imaging of the human brain at Caltech’s Brain Imaging Center.