What is the current scientific age of the Earth?

• A. ~4.5 Billion Years old
• B. ~13.8 Billion years old
• C. ~2.5 Billion years old
• D. ~100 Million years old

Answer: (A)

Dating Earth's age comes from radiometric dating of the oldest rocks and meteorites. Radioactive isotopes decay at predictable rates, so by measuring the amounts of parent and daughter isotopes, scientists estimate how long the material has been since it solidified. The oldest solid materials in the solar system are meteorites, whose ages cluster around 4.56 billion years. Earth formed from the same solar nebula not long after, so its age is estimated at about 4.54 to 4.56 billion years, often rounded to ~4.5 billion years. The other numbers don’t fit what we observe: the universe itself is ~13.8 billion years old, and Earth’s oldest rocks are far older than 100 million years or 2.5 billion years. So the ~4.5 billion years answer best reflects the evidence.