Why do scientists hypothesize that earth is about 4.5 billion years old?

Answer 1

Scientists have concluded from abundant evidence and the analysis of that evidence, that he earth is about 4.5 billion years old. This is more than merely a hypothesis, since they have the evidence for their conclusions.

Scientists realised nearly two hundred years ago that the earth must be at least a few million years old. Early in the nineteenth century, Charles Lyell examined the great volcano of Etna on Sicily and studied the historical records of frequent eruptions. He noticed that each time it erupted, a new layer of lava would be added, causing the mountain to grow at a measurable rate. By knowing the height of the volcano, its approximate rate of growth and the frequency of eruptions, Lyall determined that the volcano must be several hundred thousand years old. At the edge of the volcano, under the first lava flows, he found fossil shells that were virtually identical to the shells of molluscs still found in the Mediterranean Sea. From this, he deduced that the fossils were geologically recent, that a hundred thousand years was geologically short and that the age of the earth must be immense.

In 1862, Lord Kelvin announced that he had calculated the time it would take the world to cool down from its molten state. He calculated that this was between 20 and 400 million years, but later refined his calculations to within the range 20 to 100 million years. With the subsequent discovery of radioactivity, it was soon realised that the uranium present in the earth could have prolonged its cooling for as long as necessary to harmonise with other methods.

Samuel Haughton, an Irish geologist, calculated that sediments were deposited on the ocean floor at the rate of "one foot in 8,616 years". He then calculated a minimum duration of around 2000 million years. Unwilling to accept such a long period, he scaled it back, by a factor of 10, to just 200 million years.

In the early years of the twentieth century, Rutherford established the age of a rock as 500 million years, by measuring the amounts of radium and helium present. Strutt soon realised that some of the helium would have escaped as the rocks were crushed for analysis, leading to false short estimates of the ages of the rocks - they were really even older than the initial estimates.

In the late 1930s and early 1940s, using the new techniques and the world's most advanced mass spectromoter, Alfred Nier dated some rocks at up to 2570 million years old.

The oldest things so far found on earth are zircon crystals found in Western Australia, that are more than 4 billion years old.

Some Young-earth Creationists have incorrectly claimed that Noah's Flood could have altered the rates of decay for radioactive elements found in rocks on the earth, so that the earth is really only a few thousand years old. However, any effect from a Flood on the earth would not have affected rocks on the moon or in outer space. Zircon rock collected from the surface of the moon has now been identified as more than 4.5 billion years old. Material from meteorites has also been dated to approximately 4.5 billion years old. These figures support the calculations for the age of the earth.

Answer 2

Moon rocks have been dated 3.45 million years old, and the Moon is a sMoon rocks have been dated 3.45 million years old, and the Moon is a splintered chunk of Earth.plintered chunk of Earth.