He even made a tweet directed at those who believe the Earth is flat, and the response from the Flat Earth society will leave you dumbfounded.
Elon Musk would have to have a working knowledge of Earth's shape in order for his math to work and his company to propel a spacecraft to Mars, which is a goal of SpaceX's. With all the news swirling around flat Earth conspiracy theories recently, Musk got a little philosophical on Twitter.
While pondering the exotic spectacle of the Martian sunset, the CEO asked the question: given there's such a thing as the Flat Earth Society, why doesn't the Red Planet have its own equivalent? "Why is there no Flat Mars Society!?" he tweeted, probably just to amuse himself and his followers, and likely never expecting to find a serious response.