Gravity. It's not just a suggestion... It's the LAW! - Funny Humor Joke Science Poster Gravity. It's not just a suggestion. It's the LAW! - Funny Humor Joke Science Poster 12" x 18" Poster on High Quality heavy 80lb satin cover paper:durable & can stand up to all kinds of abuse & pucker and wrinkle like others do. This new poster is a PosterEnvy EXCLUSIVE! That means you won't find it anywhere else! We ship orders out FAST (usually with 24 hours) in heavy duty cardboard tubes! PosterEnvy has sold thousands of unique posters to thousands of happy customers around the world!