SciFiFisher wrote:My brain went "BOING!" when I read this
I believe the correct sound is "Spung!"
(Obscure? Yes, but I bet you get it anyway.)
And yeah, the amount of empty space in "solid" matter is kind of impressive. An atom's electron cloud is about 4 orders of magnitude larger than its nucleus. Neutronium isn't even degenerate matter like in a white dwarf star, where the electrons are squished into soup; it has the electrons crushed right into the nucleons to create overall neutral matter, basically a gigantic blob of atomic nucleus held together by gravity.
You can go denser, too. Quark matter would theoretically remove the barriers between nucleons. Not sure how the size scales compare for that though.
Edit: for extra weirdness, see also
https://en.wikipedia.org/wiki/Exotic_star