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 apparent magnitude is how bright the star appears to us, but  stars are all at different distances so that a star that is really  bright might look dim because it is ver â¦ y far away. So the absolute  magnitude measures how bright the star would look if it was placed  at a standard distance of 10 parsecs.   When the absolute magnitude is greater than the apparent magnitude,  it just means that it is closer than 10 pc.  Absolute magnitude is the brightness of an object as seen from a predete â¦ rmined distance, depending on the object.    For planets, the distance used is 1 AU (Astronomical Units). Stars and galaxies use 10 parsecs which is about 32.616 light years.