When the sun disappears behind the moon for a few minutes on Monday afternoon, Chris Hansen plans to be in South Carolina, ready to observe with a camera, a digital thermometer and some crickets he bought at Petco.
Myles McKay, an analyst at the Space Telescope Science Institute in Baltimore, also plans to be in the Palmetto State, manning one of 68 telescopes stationed across the United States in a citizen science project to capture images of the haze of plasma that surrounds the sun during a total solar eclipse.
Thousands of miles away in Idaho, Matthew Knight hopes to use the darkness to scan for comets using just his eyes — covered by sun-filtering safety glasses when necessary, of course. Knight, an assistant research scientist at the University of Maryland, specializes in "sun-grazers" — comets that are normally difficult to detect within the sun's glow, but can appear in the darkness of totality.
The first total solar eclipse to cross the United States since 1918 is expected to be the most-studied ever. Though the periodic cosmic spectacle has stirred deep thought for as long as human beings have been around to gaze skyward, eclipses still present scientists the opportunity to gain new knowledge.
"A lot of people don't realize just how useful eclipses are scientifically," said Nicola Fox, project scientist for NASA's Parker Solar Probe at the Johns Hopkins Applied Physics Laboratory. "There's an awful lot of stuff that can be done during eclipses that can't be done during any other time."
With so much to observe and so little time to observe it, researchers are enlisting thousands of volunteers to take pictures, shoot video, make observations and gather data.
The effort includes projects such as Citizen CATE, which McKay is joining, and Google's Eclipse Megamovie, to which Hansen plans to contribute. Both are efforts to stitch together images of the eclipse captured from the ground along its 2,500-mile path from Oregon to South Carolina.
Other researchers will watch the eclipse in both visible and infrared light and look for eruptions of charged particles from the sun's surface peeking out from behind the moon.
Still others will turn their focus toward Earth, watching animal behavior and monitoring changes in the weather or in radio signal noise.
For those who don't have experiments to conduct, the eclipse is still rare and special enough that they are flocking to the path of totality, where the sun will be completely obscured for two or three minutes.
Baltimore lies outside that cross-continental band. Viewed from Maryland, the moon will hide up to 80 percent of the sun — impressive, astronomers say, but not enough to satisfy their intense curiosity.
"So many of our faculty and students are heading to the path of totality that we had some difficulty finding volunteers to hold our simple observing event here on campus," said Elizabeth Warner, director of the University of Maryland Observatory in College Park.
Solar eclipses occur when a new moon, the monthly phase during which the moon and sun are on the same side of Earth, coincides with a syzygy, when the sun, moon and Earth are aligned on the same plane. It happens a couple dozen times each decade.
But only about one in four eclipses is total, when the moon is perfectly aligned between the sun and Earth, and is close enough to Earth that it can fully block out the sun. During totality — a period that will last up to two and a half minutes Monday — the sky darkens, allowing rare glimpses of the sun's corona, and of a starry sky in the middle of the day.
Rarer still are total solar eclipses that happen to be visible from the United States. Paths of totality have crossed parts of the country eight times since 1900, but Monday's will be the first in a century to track all the way from coast to coast. Total solar eclipses will cross the continental United States twice more in the next 30 years, on April 8, 2024, and Aug. 12, 2045.
Hansen has been looking forward to Monday's eclipse for five years. His interest in the phenomenon goes back still further, to the partial solar eclipse that hooked him on astronomy some 30 years ago.
"I'll never be able to forget it," the 41-year-old Bolton Hill man said.
Anticipating the hordes of eclipse watchers expected to descend upon the mostly quiet towns and countryside in the eclipse's path, Hansen began making plans early. He scoured maps for the best sites in South Carolina, about nine and a half hours down Interstate 95, and booked his hotel in June. He'll be traveling with friends to Columbia, S.C., which will experience roughly two minutes of darkness.
He is taking the digital thermometer to record the temperature drop, and the camera to take photos and video of the eclipse and the shadow bands — wavy lines of light that sweep across the landscape in the moments before totality.
He's taking the crickets to see if the pitch darkness fools them into chirping.
Hansen plans to submit his photos to the Eclipse Megamovie, a project of Google and the University of California, Berkeley, to collect crowd-sourced photos from citizen scientists.
Google, Berkeley and the Astronomical Society of the Pacific trained more than 1,000 amateur astronomers to shoot the eclipse from the path of totality. Google will stitch the pictures together to create a "high-tech flip-book" of the eclipse's progress across the country.
Researchers plan to study the video to learn more about the corona.
"You get to see these amazing structures," said Dan Zevin, a public education specialist at Berkeley's Space Sciences Laboratory. "There are processes happening near the surface of the sun we don't have a complete handle on," including coronal mass ejections, which spew charged particles from the sun's surface, and can affect power grids on Earth.
To McKay and hundreds of volunteer citizen scientists across the country, spotting a coronal mass ejection Monday would be like hitting the jackpot.
Citizen CATE, a project of the National Solar Observatory in Sunspot, N.M., has trained them to set up $3,700 worth of equipment to capture more than 1,000 images at each of 68 sites across the country. The goal is to create a 90-minute animation of the sun's corona, the aura of plasma that surrounds the sun.
McKay got involved with the project as a student at South Carolina State University. A native of the Bronx, he saw few stars until he moved upstate during middle school. Now the 24-year-old works at the Space Telescope Science Institute at Johns Hopkins, where he helps keep the Hubble Space Telescope calibrated.
Studying physics in high school convinced him he wanted a future in astronomy, and eventually led him to help conduct a test run for Citizen CATE during a total solar eclipse in Indonesia last spring.
"It was really magnificent," McKay said.
The Indonesians threw festivals to celebrate the occasion. When totality began, the revelers cheered, applauded and blasted car horns.
McKay, looking upward, could make out a small bright spot — a solar prominence — at the edge of the moon.
"I definitely want to see it again," he said.
A total eclipse is scientists' best chance to study the corona because the sun's brightness normally hides its fainter details from view. In ordinary times, solar researchers use coronagraphs — telescopes equipped with disks that cover the sun's face — to study it as best they can. But a coronagraph can't see as much as a telescope observing an eclipse can.
NASA's Parker Solar Probe mission will sweep through the corona two dozen times over seven years. The data it collects should dramatically improve scientists' understanding of the million-degree corona.
Fox, the project scientist, says the eclipse is the next best thing — and she's not about to miss it.
She acknowledges the irony, but admits the truth: The leader of NASA's foremost solar science mission has never seen a total solar eclipse. She planned to take vacation time, if she had to, and head for Nebraska. It turned out NASA TV planned to broadcast nearby, so she'll be taking part, as she has in past eclipses. But this time that won't mean missing the event itself.
"I'm not going to be inside a TV studio again," she said. "I'm very excited."
It will also be a first total eclipse for Jeff Marx, a physics professor at McDaniel College. He works with students on experiments of all types, including some observing the moon, but never any studying the sun.
He and his 13-year-old son plan to help with Monday's solar exploration from somewhere in the Carolinas or Tennessee, depending on weather forecasts. They will contribute to a couple of citizen science projects — Life Responds, an effort by the California Academy of Sciences to document animal behavior during the eclipse, and GLOBE Observer, a NASA-sponsored program that studies changes in weather and cloud formation.
Marx has seen several partial solar eclipses, and they were mesmerizing enough to convince him that he couldn't miss totality this time around.
"There's an old saying about eclipses," he said. "Once you've seen one, you want to see them all."