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.
Two stars of the same absolute magnitude usually do not have the same apparent magnitude because one may be much farther from us than the other. The other â¦ that is farther away will appear dimmer. To compare absolute brightness, astronomers determine what magnitude the stars would have if they were at a standard distance of about 32.6 light years.