Earth’s age is still an open question—well, depending on who you talk to.
In Jewish and Christian traditions, religious scholars report that the Bible, interpreted literally, suggests that the world is roughly 6,000 years old—a claim that is frequently cited by young-Earth creationists. Teasing an answer out of other religious traditions is a bit more difficult. For example, Muslim scholars note that the Qurʾān, or Koran, hints that each of the six days of creation presented in the biblical book of Genesis lasted somewhere between 1,000 and 50,000 years, but there are few other references to Earth’s age in Islamic tradition. According to some Hindu texts, Earth has been around for more than 150 trillion (with a t) years!
Scientists have used radioactive dating techniques to determine the approximate ages of Earth’s oldest known rocks and minerals. They estimate that Earth formed more than 4.4 billion years ago. Although no one knows when the outer crust of the planet began to form, some scientists believe that the existence of a few grains of zircon dated to about 4.4 billion years ago confirm the presence of stable continents, liquid water, and surface temperatures that were probably less than 100 °C (212 °F). Geologists have created an informal time interval, the Hadean Eon, which extends from about 4.6 billion to about 4 billion years ago to describe the period in which Earth formed from the accretion of some of the early solar system’s gases, dust, rocks, and other debris.