which allowed scientists to determine that Earth was at least 4.3 billion years old?
a. the electrical conductivity of uranium irons.
b. the radioactive decay of uranium to lead.
c. magnetic field surrounding zircon
d. chemical reactivity of zircon irons
b. the radioactive decay of uranium to lead.
The correct answer is b. the radioactive decay of uranium to lead.
Scientists determined that Earth is at least 4.3 billion years old by studying the radioactive decay of uranium to lead. Uranium is a naturally occurring radioactive element that decays over time into lead at a known rate. By measuring the ratio of uranium to lead in rocks or minerals, scientists can calculate how long it has been since the rock or mineral formed. This technique, known as radiometric dating, has provided scientists with evidence that Earth is approximately 4.3 billion years old.
The correct answer is b. the radioactive decay of uranium to lead.
To determine the age of Earth, scientists use a method called radiometric dating, which relies on the natural decay of radioactive isotopes. In this case, the decay of uranium to lead is used.
Here's how scientists determine the age using this method:
1. Uranium is a naturally occurring element found in many rocks. There are two isotopes of uranium: uranium-238 and uranium-235.
2. Uranium-238 is unstable and undergoes a series of radioactive decays, eventually transforming into lead-206. This process is known as a radioactive decay chain.
3. The rate at which uranium-238 decays to lead-206 is well understood and constant over time. This process is characterized by the half-life of uranium-238, which is approximately 4.5 billion years.
4. By measuring the ratio of uranium-238 to lead-206 in a rock sample, scientists can determine how much of the uranium has decayed and calculate the age of the rock.
5. This method is often applied to zircon minerals found in rocks, as zircon incorporates uranium into its crystal structure during its formation. As uranium-238 decays, it produces lead-206, which remains trapped within the zircon crystal.
6. By analyzing the ratio of uranium to lead isotopes in a zircon crystal using various laboratory techniques, scientists can calculate the age of the crystal and, by extension, the age of the rock in which it is found.
So, in summary, the radioactive decay of uranium to lead is the method used by scientists to determine that Earth is at least 4.3 billion years old.