Why do cats love to knock things off of tables,shelves,desks etc?

As many of you cat owners can attest to, cats just love to knock shit over. Why is this? Are our cats performing test of gravity? Maybe they’re doing complex physics trying to determine the velocity that objects will reach when dropped from a certain altitude. Or are they just trying to get our attention? I personally think this is the most likely explanation (replace men with cats and it all makes sense :P). What do you guys think?