What's It Called ...

[sherrardk]

... When a glass ball, half-filled with liquid rolls on a surface and the liquid stays level? Thank you

[jomifl]

I think gravity has already been discovered ...hence the name 'gravity'.

[jno]

and gravity has Sandra Bullock

[Old_Geezer]

I thought 1¼" internal diameter would've been enough :-( not so.