WASHINGTON -- It was an offer President Barack Obama couldn't refuse.
"You're welcome to try this out if you like," the Oakland Park, Fla., high school student said.
With that, a president who often laments a lifestyle that denies him the pleasure of driving eagerly hopped on the blue-and-silver bicycle in his dark blue suit and pedaled away, never mind that the machinery didn't take him anywhere.
"Only because these guys really want this," Mr. Obama said, gesturing to the small group of reporters and photographers brought to a White House garden to watch the president go from exhibit to exhibit at his third White House science fair. He said afterward that it's "one of my favorite events during the course of the year."
As Mr. Obama pedaled, Payton Karr and Kiona Elliot, Northeast High School classmates, explained their pedal-powered water filtration system. The collapsible, transportable emergency water-sanitation station filters E. coli and other harmful pathogens from contaminated water. In emergencies, the device can be assembled and broken down in less than an hour and can produce enough water for 20 to 30 people during a 15-hour period.
The pair were among some 30 student teams invited to the White House to show off projects that won top honors in U.S. science, technology, engineering and math competitions.
Rockets and robots were among the exhibits, too, as was a fully functioning prosthetic arm that Easton LaChapelle, 17, of Mancos, Colo., made mostly with parts generated from a 3-D printer. He said it cost just a few hundred dollars to make, far less than the $80,000 replacement arm he said had inspired him.
The arm apparently functioned until a few minutes before Mr. Obama stopped at Easton's exhibit in the State Dining Room. Easton told Mr. Obama that he'd planned for the prosthetic arm to shake the president's hand. Mr. Obama shook hands with the disembodied arm anyway, "because it was working," he said.
Three pint-sized students from Flippen Elementary School in McDonough, Ga., told Mr. Obama about the "Cool Pads" they created to help football players stay cool on the field. Evan Jackson, 10, Alec Jackson, 8, and Caleb Robinson, 8, developed the pads for the shoulders, helmet, armpits and groin with built-in temperature sensors to help keep players from overheating. Gatorade is in there, too, so players don't have to leave the field to hydrate.
Mr. Obama called their invention "pretty spiffy."
During more formal remarks after he visited a dozen exhibits, the president praised the students and their projects, which included new ways to detect cancer, create alternatives to burning wood for fuel and breeding new types of algae.
"Young people like these have to make you hopeful about the future of our country," he said.
Mr. Obama also announced a new effort to link AmeriCorps national service members with nonprofit groups that promote science, technology, engineering and math. Since taking office in 2009, he has been pushing to increase the number of students, including girls, and teachers who pursue these fields.
American teenagers aren't doing as poorly on international science tests as adults believe, a survey released Monday found.
More Americans than not wrongly think U.S. 15-year-olds rank near the bottom on international science tests, according to a Pew Research Center for the People and the Press poll. U.S. students actually rank in the middle among developed countries.
Even so, Americans are more likely to pick math or language skills over science when they are asked which subject they think deserves greater attention.
Education advocates have long warned that U.S. students need more science education if they are to keep pace with international peers. That perhaps has yielded the impression that U.S. students don't stack up to other nations on international tests.
About 35 percent of those surveyed by Pew correctly said U.S. 15-year-olds are about in the middle, and 7 percent incorrectly said Americans ranked among the top nations. Yet the plurality, 44 percent, wrongly said U.S. teens were ranked at the bottom of other developed nations.
International tests find U.S. scores aren't measurably different from the average of all other nations. Among 33 countries measured in the 2009 Program for International Student Assessment, 12 had higher scores and nine had lower ones. Another 12 had scores that weren't that much different than U.S. scores.
The Pew survey also asked participants an open-ended question about which single subject they thought deserved greater emphasis in elementary and secondary schools. Some 30 percent suggested math and arithmetic. Another 19 percent said English, grammar, writing and reading. Science was the top choice for just 11 percent of participants.