When did the following event happen?
German scientist Wilhelm Röntgen discovers a form of penetrating high-energy electromagnetic radiation that he names X-radiation due to its then unknown nature, later to be called X-rays.
Select a space in the timeline below.
1804
World population reaches one billion.
Note:
BCE means that the date is the number of years before the current era (CE/AD).
c. is short for 'circa' and indicates that the date is considered approximate.