See how the eclipse transformed America, city by city

A group of professors and students traveled from the United States to El Salto to conduct the most thorough experiment ever using an eclipse to test Albert Einstein’s theory of relativity. Einstein’s idea held that the massive sun would bend the light of surrounding stars more than previously estimated, proving that matter can pull and warp space and time.

The researchers used five telescopes to measure that effect more closely than ever, measuring stars that appear so close to the sun’s edge they can only be viewed during an eclipse.

After a countdown in Spanish, the sun darkened, and the data collection began. “TOTALITY,” yelled Sam Jeffe, a third-year physics major at Willamette University as it appeared in the telescopes’ lenses. “And it’s clear!”

Researchers will feed the data into the computer program, which will analyze the position of the stars and determine how the sun bent the light around them. But, for now, more than half the battle was done.

On U.S. soil, totality first came into view in the border city of Eagle Pass, Tex., where a crowd gathered at a football field erupted into cheers as the skies darkened above them.

A singer crooned, “I’m walking on sunshine!” People put on protective glasses and craned their necks toward the sky. Many began to clap.

Vita Garza Flores, 76, traveled from Northern California to see the eclipse in the city where she was born. She brought her daughter and brother along with her.

She grabbed her eclipse glasses, positioning them across her sunglasses: “Wow!”

Students from Uvalde High School were also among the citizen scientists using the eclipse to learn more about the sun and its effects on Earth.

They joined Southwest Texas Junior College’s STEM club in participating in a program known as the Citizen Continental-America Telescope Eclipse. Called Citizen CATE, it will combine short videos of the eclipse taken via telescope into an hour-long movie that NASA says will detail magnetic structure within the sun’s corona and reveal its density. That will help scientists to measure the strength of the solar wind — charged particles that can disrupt electricity grids and produce auroras when they reach Earth.

In Russellville, NASA gathered scientists and broadcast the eclipse’s progress live online. Tourists gathered there, too, wearing T-shirts that declared, “I got mooned at the eclipse.”

A jazz band from Arkansas Tech University played. NASA hosted workshops and Q&A sessions with scientists, at least one of whom has been to space: Among the visitors were Mike Massimino, a veteran of NASA space flight missions to upgrade the Hubble Space Telescope in 2002 and 2009.

Carbondale, Ill., earned the title of “eclipse crossroads of America,” having fallen in the path of totality for a 2017 solar eclipse as well as the event on Monday. This time, at least, the skies were clear for totality, and a full stadium of eclipse fans burst into collective screams when the moment came.

“This is so much better than 2017,” a one commentator on NASA’s live broadcast noted. “It’s so much darker than 2017.”

To many of those who experienced it, the eclipse was a spiritual event. In Bloomington, Buddhist monks marked it with a puja ceremony, a “ritual honoring and promoting inner and planetary healing,” according to the Tibetan Mongolian Buddhist Cultural Center.

Eclipse watchers flocked to Yellowwood Lake where they could experience the eclipse in nature.

When the last pulses of the sun’s rays make their way to Earth before an eclipse enters totality, they appear like a brilliant diamond set on a golden ring. In Tiffin, that meant a chance for some “unforgettable” weddings at an event called “Elope at the Eclipse.”

Crowds flocked to landmarks across the path of totality for a memorable view. At Niagara Falls, despite a thick blanket of clouds, people gathered on the banks of the Niagara River and trained their phone cameras toward the sky. Streetlights turned on, if only briefly, when darkness descended.

The moon’s shadow reached North America at the beaches of Mazatlan, Mexico, just after 2:07 p.m. Eastern time. Just about 90 minutes later, it crossed the wilderness of northern Maine, on its way toward Canada, and then, the North Atlantic.

A total solar eclipse will next dim communities in the contiguous United States in 2044, but only in parts of Montana and the Dakotas. The country will have to wait one more year for the next coast-to-coast phenomenon, a total eclipse that will stretch from California to Florida on Aug. 12, 2045. It will be a Saturday.