All Acronyms. CTA - Control Terminal Agency [Internet]; April 13, 2017 [cited 2017 APR 13]. Available from: https://www.allacronyms.com/CTA/Control_Terminal_Agency.
There are almost 120 known elements. For example, you are made up of billions of billions of atoms but you probably won't find more than 40 elements (types of atoms) in your body. Chemists have learned that over 95% of your body is made up of hydrogen (H), carbon (C), nitrogen, oxygen, phosphorus (P), and calcium (Ca).
Do we know exactly how many people there are in the world today? No. There are so many people on this planet that counting them up, exactly, is impossible. However, experts believe there are more than 7 billion people in the world today. This is a fairly reliable estimate. World population in 2014 was over 2 times greater than it was in 1965, 4 times greater than 1910, and 10 times greater than 1730.