But as a morning of shock slid into an afternoon of grief yesterday, everyone knew that the shuttle had not returned.
The sadness and foreboding associated with national calamity had returned, recalling the Challenger disaster, the Sept. 11 attacks and even the sniper shootings of last fall.
A Gaithersburg man brought his two young boys to the museum yesterday, canceling a play date. They stood with a group of 30 before the exhibit for Columbia, six hours after Houston received its last transmission.
"It seemed like the right thing to do," said Alan Cohen, 42, sons Ethan and Gabe in tow. "We want them to know it's not just a horrible thing that happened today, but that people were trying to make a difference."
He said he did not want his sons, who have lived through Sept. 11 and the sniper shootings in their short lives, to become desensitized to tragedy.
His comments were echoed by Doug Haviland, the uncle of Columbia astronaut Laurel Clark. Haviland, whose son was killed when the World Trade Center collapsed, said yesterday, "You sort of had that sickening feeling that here we go again."
President Bush ordered the American flag flown at half-staff. Others paid their respects as they could: At Beth El Congregation of Baltimore, Rabbi Mark G. Loeb asked all congregants to stand in prayer in recognition of the lost shuttle crew. Usually only those with sick relatives or friends stand.
Flowers were left in front of the Lyndon B. Johnson Space Center in Houston late yesterday, and on the road leading to the compound, the International Grill posted this message: "Families of our brave pioneers, our hearts are with you."
As dusk fell at the entrance to the space center, Roger Terrel and his sons joined three dozen people in mourning. Terrel has a friend who is a flight controller there, but he didn't know the shuttle was up until the friend had told him days ago.
"It's tough because, just like everyone says, we're like family here," said the 42-year-old veterinarian. His thoughts turned to the seven astronauts who died: "We think about the dreams they had and we think about their families, how expectant they were to get them back."
At Cape Canaveral, about 200 tourists crowded around former astronaut Bill Pogue, who was to give a talk on space flight. "We will go on," he told them.
Later, a crowd of 500 gathered for a moment of silence around the Astronaut Memorial, a black granite wall etched with the names of 17 astronauts killed in the line of duty. New wreaths were laid at the base of the memorial, next to one left from the 17th anniversary of the Challenger explosion last Tuesday.
"We've all hoped and prayed many times that no names would be added to this wall," said Stephen Feldman, president of the Astronaut Memorial Foundation.
Politicians of all stripes vowed yesterday that America would continue its exploration of space as they called the astronauts heroes. World leaders sent letters of condolence to Bush. The loss hit especially hard in India and Israel. The shuttle carried the first Israeli astronaut, Ilan Ramon, and an Indian-born woman, Kalpana Chawla.
"This terrible loss is a reminder that we can never take for granted the sacrifices of heroes," said Sen. John McCain, an Arizona Republican, in a statement. "A nation expresses its heartfelt grief for the loss of these brave astronauts."
In Bethesda, former astronaut John Glenn said he and his wife had just turned on their television to watch the shuttle's landing when word came that it was in trouble. Glenn became the first American to orbit Earth in 1962 and the oldest to travel in space in 1998.
"Anytime you lose contact like that, there's some big problem," he said. "Of course, once you went for several minutes without any contact, you knew something was terribly wrong."
At a Starbucks coffee shop just north of the Baltimore city line, real estate agent Alexander Foley compared the feeling of national tragedy to Sept. 11.
"It's not 5,000 people or 2,000 people, but I sort of look at it like it's the brightest minds in this country trying to forge their way into space, and it's risky," said Foley, 37, of Towson. "We're so advanced, we've been given the illusion that it's not so unsafe. But it is."
Reverberations were also felt in Russia, the only other space-faring nation. Russian cosmonauts expressed shock and sorrow over the tragedy, which claimed the lives of astronauts with whom they trained.
"I was shocked by this news even more because I knew all those who died personally," Cosmonaut Yuri Usachev told Itar-Tass yesterday. "We will send a delegation of Russian cosmonauts to pay the last tribute to our perished colleagues."
Meanwhile in Houston, Blanche Kadair-Carra, a 19-year veteran of Boeing-McDonnell Douglas who was part of that company's team that investigated the Challenger explosion, said she felt only "sadness and emptiness."
"It makes a big difference," she said, "to know there are children tonight without parents."
Sun staff writers Lynn Anderson, Douglas Birch, Alec MacGillis, Kate Shatzkin, Jason Song and Tanika White and the Associated Press contributed to this article.