A Simple Method of Calculating the Age of the Earth ${ } ^ { 235 } \mathrm { U }$

question 17

Essay

A simple method of calculating the age of the earth is based on the natural abundances of ${ } ^ { 235 } \mathrm { U }$ and ${ } ^ { 238 } \mathrm { U }$ . It is assumed that the quantities of these two isotopes were equal at the time that the earth formed, and measurements show that the natural abundances at present are $0.72 \% { } ^ { 235 } \mathrm { U }$ and $99.28 \% { } ^ { 238 } \mathrm { U }$ . Using the assumptions above and the half-lives of these two isotopes, $7.1 \times 10 ^ { 8 }$ for ${ } ^ { 235 } \mathrm { U }$ and $4.51 \times 10 ^ { 9 }$ years for ${ } ^ { 238 } \mathrm { U }$ , calculate the age of the earth.

---

Definitions:

Scroll Arrows

Visual indicators on a scrollbar that allow a user to move the viewable area of a window or a document up, down, right, or left.

Portrait Orientation

A page or screen layout where the height is greater than the width, commonly used for documents and mobile-device displays.

Slide Layouts

Pre-designed templates that define the positioning of elements such as text, images, and objects on a slide in presentation software.

Paragraph

A distinct section of text, often dealing with a single theme, that starts on a new line and is usually indented.