Australia is upside down to us, so why don't they just fall off?

Because Kangaroos.

They fixed this many years ago with a special Velcro like surface, before that Australians had to concentrate really hard all the time on staying on the ground and when they forgot they would start to float up into the sky and had to grab hold of things quickly.

They said duct tape can stick anything together.. guess that still holds up to this day.. let's all have an international duct tape holiday

2 words - Superglue shoes.

Something round can not be upside down and earth has a gravitational pull that's why nothing can fall off

sƃuᴉɥʇ ɹǝƃuɐɹʇs ɟo ǝɯoɥ 'ɐᴉlɐɹʇsn∀