What is Uranus?
In chapter 934 Brook said he found a Poneglyph in Odens Castle but since it wasn't red it wasn't a Road Poneglyph.
In chapter 846 we learned that Big Mamma has 2 normal poneglyphs alongside a road poneglyph.
Brook made rubbings of these poneglyphs in chapter 855.
So there's a 1 in 3 chance we'll learn what Uranus is soon. Or at least by the end of Wano.
Before it's officially revealed I want to place my bet on what I think Uranus is.
This theory was originally much longer and much more convoluted than it is now. But then I did some more research on the god Uranus and I came up with a pretty simple and obvious answer.
The god Uranus was known as the Rainmaker so the ancient weapon Uranus makes rain. No lightning or hurricanes or whirlpools. Just rain. Because in some myths Uranus was the Greek version of God in the story of Noah's Ark. He flooded the Earth and killed most of all life just by making it rain.
Now that I think of it Poseidon and Pluton are equally simple. Poseidon was the god of horses in mythology. Shirahoshi controls sea kings. As a kid I watched the Disney version of Hercules and watched Hades rowing around the Underworld on a boat. In the One Piece world both Shirahoshi and Pluton have the power to sink islands. If Uranus is a device that can make a biblical scale flood then it can sink islands too. So that's it really. Let me know what you think.