At the podium in the front of the room, a professor was sliding her notes into a briefcase.

The kids gaped at the size of the room. Rows and rows of chairs faced white boards that went across the whole front and sides of the room. Equations and diagrams and scientific terms filled most of them.

Maya turned in a full circle. “This is like, fifty times the size of our school’s classrooms!”

Simon nodded. “I used to tag along with my dad to some of his classes. These huge lecture halls are so cool, you can hear from every seat, even in the back rows.”

Maya beamed. “I bet the acoustics in here are great for singing.”

“Someone stop her before she starts belting out show tunes,” Cooper said.

Maya elbowed him playfully. “Ha! You should be so lucky.”

“There’s our clue!” Gabby shouted, pointing to the back of the room. Just like the college kids had said, a small old-fashioned blackboard was nailed to the back wall. They could see it had purple chalk on it, but couldn’t read it from across the room.

As they all ran down to get a closer look, Chelsea and Jamal couldn’t help reading things on the boards. Chelsea stopped next to a drawing of a large rock. “I wonder what this has to do with physics,” she said.

“I’m happy to explain, if you like,” a woman’s voice said from behind them. She had a cool British accent that definitely didn’t sound like their teachers from New Jersey! They turned in surprise to find the professor, her now-packed briefcase dangling from her hand.

“Oh!” Chelsea said. “I’m sorry if we’re bothering you.” She gestured to her fellow Trackers. “We’re kind of on a mission.”

“I can see that,” the professor said with a smile as the others were already crowding around the rear blackboard, talking excitedly. “My lecture today was actually on astrophysics, which uses the laws of chemistry and physics to try to understand how the universe works.” She pointed at the large image of the rock. “People might think rocks are boring, but their formation tells us a lot about the planet’s earliest days.”

“They’re not boring to me,” Chelsea said. “I collect them!”

The professor’s smile widened. “Did you know that when you pick up an igneous rock you could be holding something as old as the solar system itself?”

“Wow!” Chelsea exclaimed. She couldn’t wait to check her collection when she got home!