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.
The semi-major axis is the mean value of the maximum and minimum distances r max {\displaystyle r_{\max }} and r min {\displaystyle r_{\min }} of the ellipse from a focus â that is, of the distances from a focus to the endpoints of the major axis. In astronomy these extreme points are called apsis.