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.
Physicists and astronomers sometimes call this axis the abscissa, although that term is more commonly used to refer to coordinates along the-axis. SEE ALSO: Abscissa, Ordinate, Origin, Right-Handed Coordinate System, y-Axis, z-Axis CITE THIS AS: Weisstein, Eric W. x-Axis.. From MathWorld --A Wolfram Web Resource.