Radiocarbon dating age of earth Scyber sexo gratis webcam
The rates of decay of various radioactive isotopes have been accurately measured in the laboratory and have been shown to be constant, even in extreme temperatures and pressures.
These rates are usually expressed as the isotope's half-life--that is, the time it takes for one-half of the parent isotopes to decay.
Another line of evidence is based on the present-day abundances of the various isotopes of lead found in the Earth's crust. Three of these isotopes (lead 206, 207, 208) result from radioactive decay of isotopes of thorium and uranium.
The fourth, lead 204, is not the result of radioactive decay.
Therefore, their ages indicate when they were formed.
Because all parts of the solar system are thought to have formed at the same time (based on the solar nebula theory), the Earth must be the same age as the moon and meteorites--that is, about 4.6 billion years old.
The oldest rocks and soils from the moon are about the same age--4.6 billion years old.
Scientists assume that meteorites and moon rocks were not subjected to the extensive alteration that Earth rocks have undergone.
As magma cools, radioactive parent isotopes are separated from previously formed daughter isotopes by the crystallization process.
Over time, radioactive isotopes change into stable isotopes by a process known as radioactive decay.
Some radioactive parent isotopes decay almost instantaneously into their stable daughter isotopes; others take billions of years.
Recently, rocks over 3.96 billion years old have been dated from northern Canada, Wyoming, and China.
The ages of these oldest rocks still don't tell us how old the Earth is, but they do establish a minimum age.
The discovery gave scientists a tool for dating rocks that contain radioactive elements.