Porphyry, any igneous rock consisting of large crystals in a mass of much smaller crystals. The large and small crystals usually are of different minerals; the rock is generally named according to its major component (for example: granite porphyry). When cut and polished, porphyry has a beautiful pattern and contrast of colors. It is used for tombstones and ornamental panels.
We take much for granted about our universe, like it's getting bigger. What if the universe stopped expanding and started collapsing inward with a giant crunch?
The big bang theory is well-known, but there are many misconceptions about it. Like what? Let's start with this one: There was no bang.