An outspoken celebrity scientist has crossed the gangway of one of the most famous flights of fancy in all of Christendom – a full-scale Noah's Ark now open for business in America's Deep South.

TV presenter, boffin and avowed anti-Creationist Bill Nye "the Science Guy" came face to face with his polar opposite, Ken Ham, at the freshly-opened " Ark Experience " in Frankfort, Kentucky last week.

According to Aussie expat and curator of the Cincinnati Creationist museum Mr Ham, Nye wasn't particularly impressed by the $132m erection.

"Bill challenged me about the content of many of our exhibits, and I challenged him about what he claimed and what he believed," Ham reported on Facebook .

One bone of contention between the pair was no doubt the mechanical animal exhibits featured in the 155m-long ark's hull, which include dinosaurs. That's because the Answers in Genesis ministry, of which Ham is the president, believes the world is no more than 6000 years old.

"It was a clash of world views," Ham said in the social media post.

It's not the first time his and Nye's world views have clashed. In 2014 the pair agreed to a public debate at the Creation Museum, which was held in front of a packed house and viewed by millions around the world.

"I held strongly to the view that it was an opportunity to expose the well-intending Ken Ham and the support he receives from his followers as being bad for Kentucky, bad for science education, bad for the US, and thereby bad for humankind," Nye said of the event, and it looks as if there's been nary a trickle under the bridge since then.

"I publicly prayed for Bill," Ham wrote of Nye's trip to the ark. "I did ask him if we could be friends, but he said we could be acquaintances with mutual respect, but not friends."

In addition to the disagreement between scientists and Creationists, the ark's construction has stirred up ill-feeling among Kentuckians who feel the government-funding of the project crosses a boundary.

"It’s a clear violation of separation of church and state," local man Jim Helton said, referring to sales tax incentives worth tens of millions granted to Answers in Genesis earlier this year.

"What they’re doing is utterly ridiculous and anywhere else, I don’t think it would be allowed … Basically, this boat is a church raising scientifically illiterate children and lying to them about science," Helton told News Observer .

For the triumphant Ham, however, those details matter not now that his dream is finally afloat.

"I believe this is going to be one of the greatest Christian outreaches of this era in history," he said.