The Lost Worlds of Planet Earth Ortelius hypothesized the idea that land masses may have been connected in the past, Alfred Wegener who hypothesized the idea of a super-continent Pangaea and continental drift despite the prevailing idea of flooded land-bridges at the time, and Bruce C. Heezen and Marie Tharp who discovered the Mid-Atlantic Ridge that supported the theory of plate tectonics. Tyson describes how the landmasses of the earth lay atop the mantle, which moves due to the motion and heat of the earth's outer and inner core. Tyson moves on to explain the asteroid impact that initiated the Cretaceous–Paleogene extinction event, leaving small mammals
Earth mass the Earth are cited only beginning in the second half of the 19th century, mostly in popular rather than expert literature. An early such figure was given as "14 quadrillion pounds" ("14 Quadrillionen Pfund") [] in Masius (1859). Beckett (1871) cites the "weight of the earth" as "5842 quintillion tons" []. The "mass of the earth in gravitational measure" is stated as "9.81996×6370980" in "The New Volumes of the Encyclopaedia Britannica" (Vol. 25, 1902) with a "logarithm of earth's mass" given as "14.600522" []. This is the gravitational parameter in m·s (modern value ) and not the absolute mass. Experiments