Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Radiometric dating now allows us to determine Earth's age to an accuracy of about (a) a billion years; (b) 20 million years; (c) a few thousand years.

Short answer

The best answer is (b) 20 million years.

Step-by-step solution

Understand Radiometric Dating

Radiometric dating is a method used to date materials such as rocks or carbon by comparing the relative abundance of specific radioactive isotopes they contain. This method allows scientists to estimate the age of samples by measuring the decay rate of radioactive isotopes present in them.

Determine Typical Accuracy

Radiometric dating methods, such as uranium-lead dating, have greatly improved over the years. Through precise measurements and improved instrumentation, these methods can now pinpoint dates to a high degree of accuracy, often within tens of millions years for older samples like those of planetary age.

Compare Options

Evaluate each answer choice based on our understanding of radiometric dating: (a) a billion years: too broad; lacks precision. (b) 20 million years: good precision, typical for radiometric dating. (c) a few thousand years: extremely precise, but difficult to achieve on a grand geological scale without better technology.

Choose the Best Answer

Given the options and our understanding of radiometric dating capabilities, option (b) "20 million years" is the most accurate representation of the current accuracy attainable in determining Earth's age.

Key concepts

Earth's Age

The age of Earth is a fascinating topic that captures the curiosity of many. Scientists have worked extensively to determine how old our planet is. One of the most reliable methods is radiometric dating, allowing researchers to estimate Earth's age to about 4.5 billion years.
Using sophisticated equipment and techniques, scientists measure the decay of radioactive isotopes in rocks to get these estimates. This process gives a clear picture of how long Earth has been around. Each layer of sediment and rock formation contributes clues to our planet's grand history.
Understanding Earth's age helps us learn about the formation of the solar system and the evolution of life on our planet. These insights are crucial for geologists, paleontologists, and astronomers as they piece together Earth's past, providing answers to questions about its origin and changes over eons.

Radioactive Isotopes

Radioactive isotopes play a vital role in radiometric dating. These are variants of elements that have unstable nuclei, which means they eventually decay over time. This decay allows scientists to track the time that has passed since the rock or fossil was formed.
Here’s how it works:

• Natural elements in rocks contain radioactive isotopes.
• As time passes, these isotopes decay into different elements or isotopes at a constant rate, known as a half-life.
• By measuring the remaining amount of radioactive material and comparing it to the amount of decay product, scientists can determine the age of the sample.

The predictability of this decay process makes radioactive isotopes extremely useful for dating rocks and fossils accurately. Understanding this process helps us appreciate the precision with which scientists can unravel Earth's history from the materials found within its crust.

Uranium-Lead Dating

Uranium-Lead Dating is one of the most common radiometric methods used to date ancient rocks, and it is particularly effective for determining Earth's age.
It involves several steps:

• Uranium isotopes like Uranium-238 and Uranium-235 decay to stable lead isotopes, each at a different, measurable rate.
• The half-life of Uranium-238, for instance, is about 4.5 billion years, making it ideal for dating the oldest rocks.
• This method can be precise to within 20 million years for rocks that are billions of years old, providing clues about early Earth conditions and processes.

Uranium-Lead dating's robustness and reliability come from cross-checking results with different isotopic series and analyzing multiple samples simultaneously. This makes it an invaluable tool for geologists and paleontologists, aiding them in reconstructing Earth's history with a level of detail that was previously unattainable.