Can A Cannonball Float?
Yes, it can.
However, it depends on the density of the liquid or fluid you are putting the cannonball in. If the object is less dense than the liquid you are putting in, it will float. In fact, there is a planet that is less dense than water. Saturn. If you had a large enough ocean, Saturn would actually float in it.
But what liquid is dense enough (at room temperature) to allow a cannonball float?
Strange as it sounds, a cannonball will float in liquid mercury because the cannonball is less dense than mercury.
You can watch a cannonball floating in mercury here:
This also might raise the question, “what is the densest liquid?”
At room temperature and pressure, it’s mercury. It’s 13.3 times more denser than water. Though, with more heat and pressure, you can turn solids into denser liquids. Osmium is the densest naturally occurring element known and will turn into a liquid at a scorching 5500°F (3033 °C). It’s twice as dense as lead.
The densest matter known may be neutronium. The stuff that makes up neutron stars. A single teaspoon of this matter would weigh about 10 million tons! But it may not even be the densest matter. Scientists have proposed that an even denser material may exist. Quark matter.
Quarks are the building blocks of neutrons and protons. This matter would be so dense, that even neutrons are not stable. They fall apart into quark matter or ‘strange matter’. Some scientists theorize that when a neutron star gets denser, but not dense enough to become a black hole, it becomes a quark star.
But wait, there may be something even more exotic than that! According to some string theorists, a black hole may not actually be a ‘hole’ at all. They postulate that when a neutron star or quark star is even denser, the quarks break down into the components that make them up. Vibrating strings.
These objects are called ‘Fuzz balls‘. These hypothetical ‘fuzz balls’ aren’t rips in time and space like black holes and they don’t have a singularity. But are still so dense, that light cannot escape the pull of it’s gravity.