What Scripture says
Genesis never states the age of the earth. Any figure has to be worked out.
The young-earth calculation adds up the ages in the genealogies of Genesis 5 and 11, then the later history of Israel. In the 1650s, Archbishop James Ussher arrived at 4004 BC for creation. Others got similar dates, all within a few thousand years. Exodus 20:11 links God’s six days of creation with the human week.
The old-earth reply is that biblical genealogies often skip generations:
- Matthew 1:8 says “Joram the father of Uzziah”, but 1 Chronicles 3:11–12 shows three kings in between. “Father of” can mean ancestor.
- Luke 3:36 includes a Cainan between Arphaxad and Shelah who isn’t in Genesis 11.
- Matthew arranges his list in neat sets of fourteen (Matthew 1:17), which shows genealogies could be shaped for a purpose.
If the lists are selective, they can’t be used as a clock. Peter reminds readers that “with the Lord one day is as a thousand years” (2 Peter 3:8), though that verse is about God’s patience, not the age of the earth.
What the evidence says
Science
Mainstream science dates the earth at about 4.54 billion years, and the universe at about 13.8 billion. The evidence comes from many independent methods.
Radiometric dating
Some atoms are unstable and decay into other atoms at steady, measured rates. Uranium-238 decays to lead-206 with a half-life of about 4.5 billion years; potassium-40 decays to argon-40 with a half-life of about 1.25 billion years. By measuring how much parent and daughter material is in a rock, scientists can calculate how long the decay has been going on.
- Several methods agree. Different elements, decaying at very different rates, give consistent ages for the same rocks.
- Isochron dating uses several samples from the same rock to check whether the starting conditions were what was assumed, reducing the need for assumptions.
- The oldest pieces. Tiny zircon crystals from Jack Hills in Western Australia date to about 4.4 billion years. Meteorites, which formed with the solar system, date to about 4.57 billion. In 1956 Clair Patterson used meteorites to arrive at about 4.55 billion years, a figure that has barely changed.
Counting layers
Some natural records add a layer every year, which can be counted directly:
- Tree rings. Overlapping tree-ring records from living and dead trees go back about 12,000 years continuously.
- Ice cores. Greenland ice shows annual layers for over 100,000 years. Antarctic ice cores go back about 800,000 years.
- Lake sediments. Lake Suigetsu in Japan has tens of thousands of annual layers, cross-checked with carbon dating.
Other evidence
- Starlight. Light from the Andromeda galaxy takes about 2.5 million years to reach us. Supernova 1987A is about 168,000 light-years away, measured geometrically.
- The sea floor. Magnetic stripes on the ocean floor record reversals of the earth’s magnetic field as continents slowly drift apart, at a few centimetres a year.
- Coral reefs and rock layers take very long times to build under present conditions.
The young-earth response
Young-earth scientists dispute these conclusions:
- Changing decay rates. The RATE project (1997–2005), run by young-earth scientists, argued radioactive decay was greatly accelerated in the past, especially during creation week and the flood. Its own authors acknowledged that such acceleration would release enormous heat, a problem they couldn’t yet solve.
- The flood. A global flood could have laid down many rock layers quickly, making the earth look older than it is (see 2.8).
- A mature creation. God may have created a fully functioning world with apparent age: trees with rings, starlight already on its way, just as Adam was created as an adult.
- Starlight solutions. Young-earth physicists have proposed models in which time ran differently in the early universe, though these remain debated even among young-earth scientists.
- Problem data. They point to helium retained in zircon crystals and carbon-14 detected in coal and diamonds as evidence for a young earth. Mainstream scientists attribute these to contamination and other causes.
These views have a small number of scientific defenders and are rejected by the wider scientific community.
Summary of methods
| Method | What it measures | Ages found |
|---|---|---|
| Uranium–lead | Decay in zircon crystals | Up to 4.4 billion years on earth |
| Meteorites | Decay since the solar system formed | About 4.57 billion years |
| Ice cores | Annual layers and trapped air | Up to about 800,000 years |
| Tree rings | Annual growth rings | About 12,000 years continuously |
| Starlight | Distance divided by the speed of light | Millions to billions of years |
History
Before modern geology, most Christians assumed a young earth. But an old earth wasn’t forced on the church by skeptics. Many early geologists in the 1700s and 1800s were Christians, and by the late 1800s, many conservative evangelicals accepted an old earth, including several authors of The Fundamentals (1910–1915). The modern young-earth movement grew from Whitcomb and Morris’s The Genesis Flood (1961).
Where they meet
Christians land in different places:
- Young earth (6,000–10,000 years): reads the genealogies as complete and the days as ordinary days, and interprets the scientific evidence through creation and the flood.
- Old earth: accepts the scientific age and reads the genealogies as selective and the days as non-literal (see 2.5).
Both believe God created. The difference is how to read Genesis and how to weigh the scientific evidence.
What’s still open
- Whether the genealogies are complete or selective.
- How to read the days of Genesis 1 (see 2.5).
- For young-earth views: how to account for the size and agreement of the scientific evidence.
- For old-earth views: how to account for death before the Fall (see 2.7).
Bottom line
Mainstream science dates the earth at about 4.5 billion years. Young-earth views (6,000–10,000 years) read the genealogies as complete; old-earth views read them as selective. Genesis gives no stated age, and faithful Christians disagree, so this is rated Debated.