Concrete is the most common artificial composite material of all and typically consists of loose stones (aggregate) held with a matrix of cement. Concrete is a very robust material, much more robust than cement, and will not compress or shatter even under quite a large compressive force.
2) Y-axis contains absolute brightness Why do astronomers use the H-R Diagram? Astronomers use H-R Diagrams to classify stars and to understand how stars change over time.
Physical properties. 1  The cone shows possible values of wave 4-vector of a photon. The time axis gives the angular frequency (radâsâ1) and the space axes represent the angular wavenumber (radâmâ1). 2  In this illustration, one photon (purple) carries a million times the energy of another (yellow).