Hanover — Tuesday’s announcement of the 2018 Nobel Prize in Physics brought fresh attention to a technology that sounds like it came from the pages of a science fiction pulp novel: tools made of pure light.
But its origins, at least in part, are in a basement on the Dartmouth College campus.
Research on real-life optical tweezers and high-intensity laser pulses that can be used to move matter helped scientists from three countries — Canada’s Donna Strickland, France’s Gerard Mourou and the United States’ Arthur Ashkin — take home one of the highest honors in scientific world.
That honor was long overdue, according to one Dartmouth professor who knows both the subject and its history quite well.
“This prize did take me a little bit by surprise,” said Kevin Wright, an assistant professor of physics and astronomy at Dartmouth whose research is in the same field.
“I have known about these people for some time. I’m not certain, but speaking for myself I thought Art had been overlooked for a long time,” he said, referring to Ashkin.
Few outside the laser research community will know that the idea of “light pressure” underpinning the entire field owes its origins to the same Dartmouth campus laboratory where Wright works.
“It’s nice to work in a place with such history,” he said.
In 1900, Dartmouth researchers Ernest Fox Nichols and Gordon Ferrie Hull came together in the Wilder Laboratory with an impossible-sounding mission: to demonstrate, in a laboratory, that light could exert pressure on material objects.
They were working in the new three-story Wilder Laboratory, which today is part of the Sherman Fairchild Physical Sciences Center.
Though the Wilder Lab was considered state-of-the-art when it was built in 1899, it was rudimentary by today’s standards — steam-heated, with “lantern projectors” for physics lectures on the first floor and a telephone switchboard to allow researchers to speak to each other from 11 distinct laboratory rooms.
As with many scientific endeavors of the day, the biggest obstacle facing Nichols and Hull was their own instruments. To measure the tiny amount of force that might be exerted by a beam of light was considered almost impossible.
“All earlier attempts to experimentally observe this effect had been thwarted … even in the best vacuums achievable at the time,” according to a history of the Nichols-Hull experiments compiled for the “Pressure of Light” Symposium held at Dartmouth several years ago.
Nichols and Hull bought the best equipment they could assemble, including an unusually precise electronic circuit known as a Wheatstone bridge, ruling engines and galvanometers that could measure slight fluctuations in electrical charges and the position of objects. Each bit of data was carefully recorded by hand in logbooks (which still are preserved at the Rauner Library).
But the most important item in their arsenal had to be built from scratch — the Nichols radiometer. Just outside the painstakingly constructed bell jar, the scientists could use magnets to tweak the position of two small mirrors, suspended on wires made of quartz inside the vacuum. The mirrors acted as a kind of scale, and by comparing how they reacted when beams of light were directed at the mirrors’ shiny, and blackened, sides, they documented measurements that described, for the first time, the capacity of light to move matter.
Today, their work is considered one of the most important physics experiments of all time, and the Nichols radiometer is displayed at the Smithsonian Institution in Washington. The American Physical Society Historic Sites Committee has designated the building as a historic site.
Light of the Future
The Nichols-Hull experiment provided a foundation for generations of physicists.
Over just the last few decades, the ability to understand and manipulate light pressure has given rise to practical applications ranging from laser eye surgery to improvements in atomic clocks to the removal of detonators from old nuclear warheads. It holds promise for even more hard-to-believe applications, such as changing cloud compositions to affect rainfall.
In 1986, Ashkin used the technology to invent optical tweezers, which can pin a small sphere of glass, or a virus in place.
One person who is continuing to push the envelope of what light can do is Wright, who, before he came to Dartmouth, worked in the same facilities as Strickland and Mourou at the University of Rochester. Today, Wright works in the basement of the Wilder Laboratory, directly beneath the space where the Nichols radiometer did its work.
“The idea of holding a bacteria in a focused laser is still a kind of weird idea,” Wright said.
And yet, Wright goes further.
By using light as a tool to pin atoms into place, and relying on the precise measurements of an optical atomic clock, Wright has been able to delve deeply into the nature of quantum physics.
“My work is shaping those laser beams so that the atoms are arranged in space in various ways,” he said. The different configurations of atoms show different physical properties, which means Wright is essentially able to create designer materials that would seem almost magical to the average person.
Most of Wright’s research takes place in the lab, in “ultra-cold” chambers where the temperature has been chilled to nearly 460 degrees below — as close as is humanly possible to absolute zero.
Strange things happen to small particles in those temperatures.
For example, picture using a spoon to create a little whirlpool in a glass of water. In normal conditions, that water stops swirling, overcome by the force of friction. But in ultra-cold environments, a phenomenon called superfluidity allows the swirling to happen, in theory, forever.
Some particles also demonstrate another scientific holy grail — superconductivity, or the ability to conduct electricity without any loss of energy. Wright called those properties the “deep laws” of nature, playing out on a microscopic scale.
One challenge facing physicists, Wright said, is to maintain those properties in larger groupings of particles.
“In certain special materials, those deep laws actually come up to large scales and cause things to have very surprising and amazing properties,” he said.
College officials pointed out that Dartmouth also has ties to another one of this year’s Nobel winners, California Institute of Technology’s bioengineer Frances Arnold, whose work on protein enzymes earned her a half-share of the Nobel Prize in Chemistry, which was announced on Wednesday.
Much of the early media coverage has focused on the fact that Arnold and Strickland are women competing successfully in an arena that, historically, has a dramatic gender imbalance.
Strickland is only the third woman ever to receive a share of a Nobel Prize in physics (the first was Marie Curie in 1903), while Arnold is the fifth woman to receive a portion of the Nobel Prize in chemistry.
Every October, the most prestigious awards in science — million-dollar Nobel Prizes — are awarded by the Royal Swedish Academy of Sciences in up to six different categories of peace, economics, literature, medicine, physics and chemistry.
Between 1901 and 2017, 847 men — and only 49 women — had received prizes.
Wright said he and many of his colleagues hope this year’s awards herald a new, more equitable trend.
“There have been other prizes where, I think, a junior researcher, particularly a female researcher, was not recognized,” he said. “One prize does not make up for all the mistakes of the past, but it’s evidence that there is progress.”
Just last year, Arnold received an honorary Doctor of Science degree from Dartmouth, and the Robert Fletcher Award from the Thayer School of Engineering.
Joseph Helbe, dean of the Thayer School of Engineering, hailed Arnold in a public statement, saying her award “is a strong reminder of how a commitment to science and an understanding of interdisciplinary connections can improve life for all.”
And Arnold herself, speaking to students during the Thayer School’s 2017 Commencement Weekend investiture ceremony, described a landscape that marries the bell jars of the past to the superconductors of the future.
“We engineers build using what we have and know at the time,” Arnold said in her address. “Ignorance of underlying physics or chemistry can be circumvented with creativity and experimentation.”
She also hinted at what drives science — and scientists — to continue delving into the secrets of the universe.
“I have worked with, and drawn inspiration from, the greatest engineer of all time,” she said. “Nature.”
Matt Hongoltz-Hetling can be reached at firstname.lastname@example.org or 603-727-3211.