Humans have known that the Earth is spherical for around 2,000 years, when Aristotle first considered it as a way to explain the horizon. That is, unless you ask a "flat earther".

As the moniker suggests, flat earth theorists are convinced that the planet we call home isn't globe-shaped. And although they are not decided on what shape they believe it really is, their ideas have been gaining traction in recent years.

In November, The Flat Earth Society, the most vocal proponents of the theory, responded to a tweet by Tesla and SpaceX chief Elon Musk, asking, "why is there no Flat Mars Society!?" prompting international headlines. Just days before, former England cricketer Andrew "Freddie" Flintoff tweeted that he had been listening to the Flat Earth Society podcast and that he was warming to their ideas. Rapper B.o.B., reality TV personality Tila Tequila and several NBA players have also come out as flat earthers.

And while this may seem hilarious, in a so-called post-truth world it is a worrying trend that people still believe the earth is flat despite proof - including photographic evidence and our observations of the stars - to the contrary.

Pete Svarrior is among The Flat Earth Society's members. He tells IBTimes UK he first encountered the group in 2010 with a generous dose of scepticism. By 2013 he says he was "fully convinced" that the Earth was indeed flat.

Surely, though, he doesn't really believe that the earth is flat? We asked him to find out.

You say that we can use our senses to prove the world isn't round, but if the earth is flat why hasn't anybody ever reached the edge?

First of all, there is no clear-cut agreement among Flat Earthers regarding whether or not there even is an edge. Some would argue that it's infinite. While I personally don't agree with this particular belief, I'm still a bit lost. Round Earthers say the Earth's centre is an inner core, about 1200km in radius, with a surface temperature comparable to that of the Sun. Do you think the argument of "okay, but how come no one's drilled into it yet" would be particularly convincing? I don't.

The conditions one would be subjected to beyond the Ice Wall [a 150-foot-tall wall that flat earthers believe encloses the perimeter of the Earth] are extremely hostile. The expectation that someone would venture out there, travelling for an unknown distance in unsurvivable conditions is just a strange standard of evidence when the Flat Earth Theory can be confirmed in much simpler ways.

Why does the Flat Earth Society reject what others would regard as proof that the world is round, e.g. photographic evidence?

Because if we accepted every unverified photo we receive as proof, we'd also have to acknowledge the existence of Alderaan [the planet in Star Wars] (well, at least historical existence).

If the earth is flat, what would be the benefit of maintaining the lie that it's curved?

There isn't one. The Round Earth misinformation was never intentional. It is far more likely that it was a simple side effect of trying to fabricate (parts of) a space programme. It was already understood that the Earth is round, so it made sense at the time to make the Earth appear round in any imagery produced.

Do you also believe that the other planets and celestial objects are flat?

No. Earth, to date, is the only known flat celestial body.

Do you genuinely believe that the earth is flat, or are you playing devil's advocate to invite people to question authority?

Surely a good devil's advocate wouldn't admit to being one? Obviously this sort of debate is very appealing for devil's advocates (for either side - round or flat), but the vast majority of long-term members are committed to the Earth's flat shape, or openly sceptical of our ideas. Myself, well, I hope my work speaks in my favour louder than any of my words could.

The Flat Earth Society member Pete Svarrior
The Flat Earth Society member Pete Svarrior Pete Svarrior

How does being a Flat Earther affect your daily life? Is it something that members are generally open about?

It definitely comes up in casual conversation, but it doesn't affect me particularly much. Some people see it as a peculiarity they'd rather ignore, others are very curious and won't miss an opportunity to argue the subject over a few beers. As long as friends and colleagues are concerned, we approach our differences with a smile. However, I have also had negative responses, some of them aggressive.

What evidence is there to prove that the earth is flat?

As you might expect, most of it is empirical and experimental. One of my favourite examples is the Bishop Experiment, though the Bedford Level Experiment is probably better-known due to its age. In short, both experiments rely on trying to observe the curvature of large bodies of water, and failing to find any.

Do you question the validity of anything else?

No, not really. I know some Flat Earthers are keen on other conspiracy theories, but I'm not one of them.

Please add anything else you feel is important

To quote prominent Flat Earther Mark Sargent: "Don't take my word for it – I could be a mental patient recently released from an institution." Research the subject yourself, and make up your own mind about what you wish to believe. We won't think any less of you for disagreeing with us - we hope this courtesy can be mutual.

This interview has been edited for brevity.