But for humans whose life span rarely reaches more than 100 years, how can we be so sure of that ancient date? Even the Greeks and Romans realized that layers of sediment in rock signified old age.
But it wasn't until the late 1700s -- when Scottish geologist James Hutton, who observed sediments building up on the landscape, set out to show that rocks were time clocks -- that serious scientific interest in geological age began.
Though they are very tiny, polonium radiohalos have a huge message that cannot be ignored.
They point to a catastrophic origin for granites, consistent with the biblical timeframe for earth history and God’s judgment during the Flood.
Radiocarbon dating is one kind of radiometric dating, used for determining the age of organic remains that are less than 50,000 years old.
For inorganic matter and for older materials, isotopes of other elements, such as potassium, uranium, and strontium, are used.
A method for determining the age of an object based on the concentration of a particular radioactive isotope contained within it.
There are over forty such techniques, each using a different radioactive element or a different way of measuring them.
Measuring the uranium-to-lead ratios in the oldest rocks on Earth gave scientists an estimated age of the planet of 4.6 billion years.
Segment from A Science Odyssey: "Origins."Geologists have calculated the age of Earth at 4.6 billion years.
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. 1979, 1986 © Harper Collins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Cite This Source (rā'dē-ō-mět'rĭk) A method for determining the age of an object based on the concentration of a particular radioactive isotope contained within it.
For inorganic materials, such as rocks containing the radioactive isotope rubidium, the amount of the isotope in the object is compared to the amount of the isotope's decay products (in this case strontium).