American basketball player Kyrie Irving has apologised after months of spreading theories the Earth is flat.

Irving, who plays for the Boston Celtics in the NBA, has repeatedly made public statements in support of the easily disproved theory over the past 18 months.

Without saying he had abandoned his own belief that our species inhabits a flat disc-shaped world surrounded by an ice wall, Irving apologised for speaking about the theory publicly, saying he didn’t realise the effect it would have on people.

“At the time I was like huge into conspiracies, and everybody’s been there,” Irving said, eliciting laughs during an onstage interview at Forbes’ Under 30 Summit in Boston on Monday.

“Everybody’s been there – like ‘yo, what’s going on with our world?’ You click a YouTube link and it’s like, how deep the rabbit-hole goes.”

He said: “At the time, you’re like innocent in it but you realise the effect of the power of voice. And even if you believe in that, just don’t come out and say that stuff. That’s for intimate conversations because perception, and how you’re perceived, it changes.

"I’m actually a smart-ass individual. It’s not like I was just going around saying that. At the time, I just didn’t realise the effect. I was definitely at that time like ‘I’m a big conspiracy theorist! You can’t tell me anything!’

“So I’m sorry about all that. For all the science teachers and everybody coming up to me like ‘I’ve got to re-teach my whole curriculum’, I’m sorry. I’m sorry. I apologise.”

Irving first publicly spoke about flat-Earth theories during an appearance on a podcast in February 2017.

In the Road Trippin’ podcast, hosted by his teammates Richard Jefferson and Channing Frye, Irving said “the Earth is flat” three times, adding: “What I’ve been taught is that the Earth is round, but if you really think about it from a landscape of the way we travel, the way we move and the fact that – can you really think of us rotating around the sun, and all planets align, rotating in specific dates, being perpendicular with what’s going on with these ‘planets’ and stuff like this?”

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