Definition of radioisotope dating
Many isotopes have been studied, probing a wide range of time scales.
C and counting the amount of each) allows one to date the death of the once-living things.
The best estimate from this dating technique says the man lived between 33 BC. From the ratio, the time since the formation of the rock can be calculated.
The boat of a pharaoh was discovered in a sealed crypt and reassembled in a museum near the pyramids (see Fig. The age of our galaxy and earth also can be estimated using radioactive dating.
Perhaps you have heard of Ice Man, a man living in the Alps who died and was entombed in glacial ice until recently when the ice moved and melted.
The man's body was recovered and pieces of tissue were studied for their C content by accelerator mass spectroscopy.
For example, about 1.5 percent of a quantity of Uranium 238 will decay to lead every 100 million years.
By measuring the ratio of lead to uranium in a rock sample, its age can be determined.
Radioactive dating is a method of dating rocks and minerals using radioactive isotopes.
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.
Certain isotopes are unstable and undergo a process of radioactive decay, slowly and steadily transforming, molecule by molecule, into a different isotope.
This rate of decay is constant for a given isotope, and the time it takes for one-half of a particular isotope to decay is its radioactive half-life.