Time is relative To a kid a year seems like a mighty long time to wait for a present or a vacation But to the Earth a year is like a split-second Compared to an individual person or even compared to the human race Earth is unimaginably old The study of the Earth itself what it is made of and all that lies beneath the ground is the science of geology Geologists call the ground we walk on Geologists call the ground we walk on Earth’s crust Like a pie crust Earth’s outermost layer is a thin shell which is even thinner under the ocean and thicker where there is dry land 6
HUMAN TIME VS GEOLOGICAL TIME The late paleontologist Stephen J Gould once said if a person’s outstretched arms represented all of time since the Earth formed the amount of time humans have witnessed could fi t on the tip of a single fi ngernail Not even the nail itself just the tip of the nail Everything else happened before humans were around to notice In other words nearly all of Earth’s life is prehistoric So how do people know things about Earth from all that prehistoric time Those answers come from a variety of sources but many of the most astounding discoveries of prehistoric life on Earth come from paleontologists Paleontologists are like detectives trying to solve a case about the history of living things on this planet 8
Fossils of some of Earth’s earliest known humans found by researchers at Atapuerca a cave system in Spain are relatively new fossils even though they are thought to be more than a half million years old 9
