The Hollow-Face illusion (also known as Hollow-Mask illusion) is an optical illusion in which the perception of a concave mask of a face appears as a normal
almost an hour, leading to arguments that it must be hollow like a bell. Lunar seismology experiments since then have shown that the lunar body has shallow
as a hollow-body electric guitar, is a type of electric guitar designed to be played with a guitar amplifier featuring a fully or partly hollow body and