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 term absolute magnitude usually refers to the absolute visual magnitude, Mv of the star, even though the term âvisualâ really restricts the measurement of the brightness to the wavelength range between 4,000 and 7,000 Angstroms.