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.
A HertzsprungâRussell diagram plots the actual brightness (or absolute magnitude) of a star against its color index (represented as BâV). The main sequence is visible as a prominent diagonal band that runs from the upper left to the lower right.