"This is the smartest group of kids I've ever seen," he said.
Hall and teammates Chris Johnson and Brian Bogusevic couldn't help but be impressed by the questions being asked of astronaut Clayton Anderson by a group of fifth-grade students who joined the Astros on a behind-the-scenes tour of NASA's shuttle mock-up facility at the Johnson Space Center on Thursday.
"Some of these kids are asking questions I would have no idea of asking when I was in the fifth grade," Hall said.
It was impossible to tell if the fifth-graders from Bauerschlag Elementary in League City, Texas, were more impressed with the Astros or the astronaut, but the first day of the team's annual winter caravan was a success for everyone.
Hall, Johnson and Bogusevic joined former players and broadcasters Jim Deshaies and Larry Dierker on three caravan stops Thursday, including the trip to NASA to get a tour of the facility the astronauts use to prepare for a mission into space.
Johnson took as many photos as he could, using his cell phone camera, to send back to his buddies in Florida, which is where the Astros will be in about five weeks for the start of Spring Training.
"This is awesome," he said.
The Astros will train in Florida for about six weeks to get ready for the upcoming season, which is nothing compared to what Anderson has to do to prepare for a mission. Anderson, who spent 152 days in space on the international space station in 2007, had to prep for years to be ready for his assignment.
Anderson held a question-and-answer session with the players and kids and touched on a various range of topics, including what kind of fuel is used to send the space shuttle 250 miles into orbit, what subjects he studied to become an astronaut and what the astronauts do to stay in shape in space.
"It's good to learn about what these guys have to go do to become an astronaut, and the time it takes and the actual engineering and physics behind it is very informative," Hall said. "A lot of this stuff I never knew. ... It's very informative and something I'll remember."
The lesson wasn't lost on 10-year-old student Erika Schwibinger.
"To hear it from an astronaut's perspective, it was really nice to hear what he had to say," she said.
The tour enabled the players and the kids to receive the kind of access the public doesn't usually get. Bogusevic, who stands 6-foot-3, emerged from one of the cramped shuttle mock-ups glad that he has much more room to operate in the outfield of Minute Maid Park.
"Coming here and getting a behind-the-scenes tour of NASA is very interesting and a lot fun," he said. "If I was [a kid] I would be more impressed with the astronauts, because I'm more impressed with the astronauts myself."
As Deshaies entered one of the mock-ups, he joked: "One small step for man."
Hall hopes the kids will be ready for whatever opportunities come their way in the future, whether it's on a baseball field or outer space.
"I think definitely some of the kids have an athletic mind and some of the kids are asking questions I never would have been able to ask, which means they're pretty educated kids," Hall said. "I think they have a lot of interest in becoming astronauts or doing other things that it takes to do a lot of studying."
When the children got back on the bus to head back to school, Hall, Johnson, Bogusevic, Dierker and Deshaies were transported to another NASA building to sign autographs for employees. But the time spent learning about the space program left a positive mark on Johnson.
"Coming to see this stuff is incredible," he said. "I'm kind of like a kid right now."
Bauerschlag principal Trudy Knight hopes it left an indelible memory on her kids, too.
"What a learning experience," Knight said. "All baseball players and athletes are idols of children, and that was the draw to get them here. If we can get them to be interested in science on top of that, that's even better."
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.