I didn't assume relativity was true, I explained why it's true.
I went into detail about the Sun being out in Australia when it's not out in America, and "up" being towards the Sun in Australia, while at the same time, "up" would be a different direction in America... and you ignored it. Why did you ignore it?The only option is you're trolling.
If you're on the moon, where is up? If you're on Mars, where is up? The same direction as "up" is on Earth? If you're in Australia, where is up? The same "up" as it is in America? How? Australians have daylight while Americans have night. "Up" to them may be to the Sun. So "up" to an American at night would also be to the Sun? How can that be when the Sun is not visible?
Nothing is contradicting my brain, experience, or intuition. My last paragraph is using my brain, experience, and intuition to explain to you that there can't be one definite "up" or "down". It's always relative. There is no preferred reference frame in the Universe. If you're floating in space no where near the Earth, how do you know if you're facing up or down? You can't, because there is no such thing as up or down in space.