The Origin of Time

Author: A.G. Smith / Country: Mainland China
Publisher:
Publish Date: 2006-05-01
Features: Scholars with a thirst for knowledge have long been curious about the age of the Earth and the organisms that have lived on it, continuously exploring these mysteries. In 450 BC, the Greek historian Herodotus discovered fossils of marine bivalves in the Libyan Desert, which baffled people because bivalve animals cannot live on land. Herodotus concluded that this desert might have once been the seabed of the Mediterranean Sea. Since many of the species in the fossils had gone extinct, Herodotus posed another question: How long ago did these marine bivalves live? Later, religious authorities believed that the fossil record preserved traces of plants and animals that existed before the Great Flood. Some people argued that, according to the Bible, God created the heavens and the Earth on October 23, 4004 BC, on a Sunday. However, many found this explanation unconvincing.
In the 19th century, Europeans began studying rock layers (also called strata). They discovered that each layer of rock contained fossils of different species. From this, they concluded that different rock layers and their included fossils formed in different eras. Due to the numerous layers of rock, they believed that the Earth was much older than people had imagined. In the Arctic, people found fossils of tropical plants; in Brazil, they discovered remnants of the Ice Age. These discoveries proved that the Earth had undergone significant changes over vast stretches of time.
In 1858, Darwin published On the Origin of Species, where he explained the changes in the Earth. Darwin's theory proposed that the Earth existed in the universe long before people had imagined, millions of years earlier. Around 1900, the discovery of radioactivity provided geologists with a more precise method for determining the Earth's age. How do geologists use radioactivity to calculate time? In nature, many radioactive elements, such as radium and uranium, decay at a fixed rate, eventually turning into lead. Geologists can determine the age of rocks by measuring the amount of uranium in them and comparing it to the amount of lead they contain, thus deducing when the rocks formed.
Today, scientists believe that the Earth formed between 2 billion and 5 billion years ago. Radioactivity is also used to determine the age of animal and plant remains. All living organisms contain the radioactive element carbon-14, which decays at a certain rate. By measuring the amount of decay, scientists can determine the age of plants and animals. P7-P10