Solid, in physics and chemistry, one of the three states of matter. The other two states of matter are gas and liquid. A solid tends to maintain its shape without a container. Some solids are harder than others. True solids are crystalline; that is, the atoms of which they are composed are arranged in definite, three-dimensional patterns. They have definite melting temperatures. Some substances, such as glass and tar, that appear to be solid are amorphous—they do not have a crystalline atomic structure. These substances soften and melt over a range of temperatures; they are not true solids.
Has this ever happened to you? The meteorologist calls for a massive snowstorm, but the flakes fail to arrive. Chaos theory can shed light on why forecasts fail (and why our orderly world may not be so orderly after all).
To the uninitiated, the LHC can look like a junk drawer ... a junk drawer that's full of tiny, rapidly decaying particles that move at light speed. How do scientists know what's where?