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.
Photo by: Darsie Creative Commons. The semimajor axis is half of the major axis in an ellipse at its longest diameter, a line running through its center and the foci. The semimajor axis runs from the center to the ellipseâs edge through a focus. It is that measure of the orbitâs radius at its most distant points. In the case of a circle, it then becomes the radius itself. We can think of it as any ellipseâs long radius. In the world of astronomy, the semimajor axis is known to be part of an orbit. For objects within the solar system, this axis is directly related to the orbital periods, which is noted in Keplerâs third law.