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 Hertzsprung-Russell diagram shows absolute magnitute or brightness against it's colour (which is an indication of temperature) . This shows the main sequence, which describes the typical life of a star. The Hertzsprung-Russell diagram shows absolute magnitute or brightness against it's colour (which is an indication of temperature) .