After the many ramblings I made regarding Dark Matter previously, I want to turn around and think about Baryonic Matter again. Ordinary Matter is something that physicists know much more about than the mysterious Dark Matter and Dark Energy, even though in reality they do make up more than 95% of our known Universe. We are more knowledgeable about Baryonic Matter because of its presence all around us, after all, it is everything we can see and detect: from forms of life, elements in the Earth’s crust and mantle, buildings, cars, the Earth, the Sun, all of the stars… you get the idea.
Now, the stuff that makes up the matter. Firstly what comes to our mind may be elements, which are a table of 100 odd substances that are often called the “primary constituents of matter”. These elements can be identified through their chemical properties and are placed in the Periodic table in order of increasing atomic number (the number of protons in its atom’s nucleus).
Atoms are another level down from the elements of the periodic table, which distinguishes different types of atoms. Atoms themselves is another study on its own. In the early 20th Century, Rutherford and a couple other physicists discovered an awful lot that directly correlates to our modern understanding of the atom through an experiment – firing alpha particles at a piece of gold leaf.