Board Thread:Theories and Speculation/@comment-3568954-20150602045122/@comment-2013124-20150607173959

First the physical size of the planet doesn't define it's gravity. Mass does, Earth is fairly heavy for it's size due to having a core that's a molten slug of iron. Even if it did anything that evolved on that planet would be born and bred to operate at that level. They'd be normal not superhuman. We know the world has nonsuperhumans because they're the ones that hire Shinobi.

Second there is no clear speed ever given at which ninja travel. I disagree with Rachin123's assessment that ninja never travel at supersonic speeds. But I also think it's unlikely that anyone can do it for 12 consecutive hours for several days at a time. If they could why Summon animals which can travel faster than humans?

The main reason I disagree with this theory lies in Chapter 700 and beyond. There's never any outside forces which shows up to investigate all the gravitational and thermal weirdness that went on during the war. 2 meteors the size of cities dropped on the planet. The moon falling from the sky only to be replaced by 9 smaller moons. That were then replaced with a moon just like the original one. Even if the technology level of anyone else on the planet was low someone would have set sail too see what the heck went on. We know those people have Chakra as well because the Sage of 6 Paths gave it to people all over the world. It stands to reason that the Planet of Naruto is smaller than our own or the boundries of countries are far larger.

Plus The Last shows us that the planet is Earth.