The material that formed the earth was created in a supernova explosion approximately 6 billion years ago. The two most common isotopes of uranium, 238U and 235U were created in roughly equal amounts. Today, the earth contains more than 100 times as much 238U as 235U. Which isotope has a longer half-life? a. 235U has a longer half-life because more of it have decayed.
b. 235U has a longer half-life because less of it have decayed.
c. 238U has a longer half-life because less of it have decayed.
d. 238U has a longer half-life because more of it have decayed.