age of the Earth

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age of the Earth

The oldest rocks found in the Earth's crust have been assigned ages of 3.96 billion (109) years from radioisotope studies, but other properties of the rocks support the belief that the planet shares a common origin with the rest of the Solar System, about 4.57 billion years ago. The cycling of the crustal material by plate tectonics (see Earth) and the eroding effects of ice, water, and wind mean that none of the earliest rocks survive intact and that evidence of an early meteoritic bombardment, so apparent on the Moon, Mercury, and Mars, is absent. See Earth; Solar System, origin.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
References in periodicals archive ?
Religious men at that time started to question the age of earth, for it must be millions of years old for all that lived at that time and the stars were really distant suns.
It is based on the Gojoseon period (roughly the Bronze Age of Earth).
The entertaining introduction discusses the history of paleontology, including nineteenth-century arguments about the age of Earth. "101 American Fossil Sites You've Gotta See " also features a short history of life on Earth, from microbes in 3-billion-year-old chert to massive mammals of the Pleistocene ice ages.
The American public already has difficulty accepting scientific facts about climate, evolution, and the age of Earth. Your publication should be supporting critical scientific thinking and not supernatural theories of the universe.
In fact, chemical and biological conditions in this middle age of Earth history were sufficiently static to earn this interval an unflattering nickname-'the boring billion.'
A major effect of this work will be to decrease all previous uranium-lead (U-Pb) age determinations, by up to 700,000 years for samples that are about 4.5 billion years old -- the age of Earth. In particular, the new 238U/235U ratio will allow geologists to place more accurate limits on the exact timing of a broad range of geological processes, from the initial formation of our planet, continents and economic mineral deposits, to past evolutionary events and climate change.
If Earth were compressed into 24 hours If the age of Earth compressed into then the first humans would appear just 40 seconds before midnight.
It is about four billion years old, just 500 million years younger than the estimated age of Earth. It is possible that this rock was formed when the very earliest life was appearing on Earth, and perhaps on Mars.
That's the consensus of two independent research teams that used the same radioactive-dating technique to estimate the age of Earth and some of its neighbors.
Hugh Strawn, who works for the alliance's sister organization, the Property Loss Research Bureau, contends that the global-warming theory is based on data that is only 100 years old and that it is an infinitesimal period of time compared with the age of Earth. The bureau believes any slight warming could be just a natural change that has occurred before in history.
Although the average age of Earth's surface is only about 500 million years, the oldest rocks geologists have found on our planet formed 3.8 billion years ago.
Uranium-lead isotope dating places surrounding rock at around 1.7 billion years old, somewhat less than half the age of Earth. But that "makes the fossils a good 800 million years older than the next organisms that look clearly like true multicellular algae," says Harvard University algologist Andrew H.