Why was Kyrie Irving carrying an atlas on Celtics' plane?

Kyrie Irving appears to have squeezed in some extra studying during the playoffs.

The Celtics star was seen boarding the team’s plane to Indiana on Thursday carrying a copy of “National Geographic’s Family Reference Atlas,” which contains over 1,000 maps and illustrations.

It’s ironic considering Irving infamously drew a lot of attention during the All-Star break as a member of the Cavaliers in 2017 when he said on a podcast he believes the Earth is flat. He later apologized in October for his remarks, claiming he “didn’t realize the effect” his comments would have.

“At the time I was innocent in it, but you realize the effect of the power of voice,” Irving said at the time. “And even if you believe in that, don’t come out and say that stuff. That’s for intimate conversations because perception, how you’re received, it just changes. Like, no I’m actually a smart-ass individual. … At the time, I just didn’t realize the effect. And I was definitely at that time a big conspiracy theorist. You can’t tell me anything.

“I’m sorry about all that, for all the science teachers and everybody coming up to me like, ‘You know I have to re-teach my whole curriculum?’ I’m sorry. I apologize.”

Irving added that he planned on keeping a low profile going forward, so it remains to be seen if he’s being serious or just trolling.

The Celtics hold a 2-0 series lead over the Pacers entering Thursday’s Game 3 matchup, with tipoff scheduled for 8:30 p.m. ET.