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.
To illustrate, let f(t) denote the left hand side of the alignment equation, with the radii r1 = 0.387, r2 = 0.723, and r3 = 1, corresponding to the orbits of Mercury, Venus, and Earth. The function f(t) versus t is as shown below for a typical five-year period.