Answer:
These atoms will decay as the rock ages, and by measuring the ratio of radioactive isotopes within the rock, scientists can figure out how long it has been around. In 1913, geologist Arthur Holmes published “the Age of the Earth,” the first major effort to date the planet using radiometric dating.
Answer:
The Nazis began experimenting with poison gas for the purpose of mass murder in late 1939 with the killing of patients with mental and physical disabilities in the Euthanasia Program.
The Ethnologue is an encyclopedic reference work cataloging all of the world’s 7,105 known living languages