Kyrie Irving apologized Monday for saying last year that the Earth is flat, explaining he "didn't realize the effect" his comments would have.

The Boston Celtics point guard, speaking at Forbes' Under 30 Summit in Boston, was asked at the conference to state once and for all which side he is on in the "debate" over the Earth's shape.

Kyrie apologizes for saying the world is flat. #Under30Summit pic.twitter.com/uJH3fNbPqS — Nicole Yang (@nicolecyang) October 1, 2018

Irving explained he was big into conspiracy theories in February 2017 when he made his comments, and the attention he received made him realize the "power of voice."

"Even if you believe in that, don't come out and say that stuff. That's for intimate conversations because perception and how you're received, it changes. I'm actually a smart-ass individual," he said.

Irving said he also didn't understand the impact his comments would have on others.

"At the time I didn't realize the effect. I was definitely at that time, 'I'm a big conspiracy theorist. You can't tell me anything.' I'm sorry about all that. For all the science teachers, everybody coming up to me like, 'You know I have to reteach my whole curriculum!' I'm sorry. I apologize. I apologize," he said.

Irving, then with the Cleveland Cavaliers, made headlines last year after discussing conspiracy theories on the "Road Trippin' with RJ & Channing" podcast with then-teammates Richard Jefferson and Channing Frye.

"Even if you believe in that, don't come out and say that stuff. That's for intimate conversations because perception and how you're received, it changes."

"This is not even a conspiracy theory," Irving told Jefferson and Frye while recording the podcast on an airplane. "The Earth is flat. The Earth is flat. ... It's right in front of our faces. I'm telling you, it's right in front of our faces. They lie to us."

He later reiterated those beliefs to ESPN's Arash Markazi and commented that it was "hilarious" to him that his comments became a "social phenomenon."