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 measure of the intrinsic brightness of objects. The apparent magnitude of the object [fit were at a distance of ten parsec s. The absolute magnitude of Sirius is +1.4.