Some people believe Earth is only about 6,000 years old. Rocks, meteorites and Moon rocks all contain natural clocks, and they all say about 4.5 billion years. A flood over the whole planet would have left clues everywhere, and those clues aren't there.
Earth is about 4.54 billion years old, with an uncertainty of less than 1%.1 Several independent methods agree. A single worldwide flood about 4,500 years ago would have left evidence in rocks, ice, trees, and DNA that isn't there. And many Christians, including large denominations and Christian science groups, accept the old-earth science.6
"Young-earth creationism" is one specific reading of Genesis. It is not what all Christians believe. Plenty of believers, including the scientists at BioLogos, accept an old Earth. This page is aimed at the specific claims of the young-earth view, not at Christianity as a whole.
How we know: the 4.54 billion year clock
Earth's oldest rocks have been recycled by plate tectonics, so they can't give the exact age directly. Instead, scientists date meteorites, which formed at the same time as the rest of the solar system, and which have stayed largely unchanged since.1 The key evidence:
| What | Age |
|---|---|
| Earth (best estimate) | 4.54 billion years (±<1%) |
| Meteorites and solar system | 4.53–4.58 billion years |
| Oldest Moon rocks | 4.4–4.5 billion years |
| Oldest zircon crystals on Earth | up to 4.3 billion years |
| Oldest rock found on Earth (Acasta Gneisses) | about 4.03 billion years |
The "best age" comes from lead isotope ratios in the Canyon Diablo iron meteorite.1 The point is that independent lines agree: meteorites, Moon rocks, and Earth minerals, measured by different labs with different methods, land in the same range.2
Try it: a radioactive clock
Notice the pattern: the clock doesn't speed up or slow down with temperature, pressure, or chemistry in any way that matters here. The decay rate is set by the inside of the atom. That's why the method has been checked across rocks of known age and across different isotope pairs.
The flood
The young-earth view says a global flood about 4,500 years ago laid down most of the rock layers. Here is what the evidence says. Details are from Science Meets Religion and from a Baptist geologist-informed editorial.34
- Dating. Radiometric dates of the fossil layers are in the millions of years, and they agree across different places.
- Fossil order. A flood doesn't sort fossils into the exact order we find. Dinosaurs could have reached high ground, and human remains and tools would not be found only near the top.
- The Ark. Using the biblical size of 300 × 50 × 30 cubits (about 155 × 26 × 16 m), the animals alone would weigh about 400,000 kg if only yearlings were taken, and about 5 million kg if adults were taken. Add food and water for a year, which multiplies the load.
- Where animals live. Kangaroos, sloths, koalas and dodos live far from the Middle East. How would they have gotten to the Ark and back?
- No signature. A global flood would have left silt and rounded rocks everywhere. Tree rings, coral reefs, ice cores, lake sediments and the seafloor show no such event.
- DNA. Genetic data show no sign that all species shrank to a handful of animals about 4,500 years ago.
- Mount Ararat. Lava flows there cut across five layers of sedimentary rock. The lava is younger than the layers it cuts, so the layers can't all be a single year's flood deposit.4
- The Grand Canyon. The roughly 5,000-foot sequence contains raindrop prints, ripple marks, mud cracks, tracks, and fossils. These need calm, shallow, or dry conditions over long periods, not violent flood waters.4
Real floods occurred, but they were regional: the Mediterranean refilled about 5.3 million years ago; the Black Sea flooded roughly 150,000 km² between 7500 and 5500 BCE; the Persian Gulf filled around 12,000 BCE.3
The starlight problem
We can see galaxies millions and billions of light-years away. Light travels at a finite speed, so seeing something a million light-years away means the light left it a million years ago. If the universe were 6,000 years old, we shouldn't see those galaxies yet. Young-earth organizations offer several answers (for example, that light was created already "in transit," or that the speed of light changed), and each has been criticized by physicists and by other creationists. The Talk.Origins Archive keeps a detailed index of such claims and replies.5
Young-earth writers argue that scientists assume the past worked like the present (uniformitarianism), and that different assumptions about the starting conditions give different ages. Mainstream scientists answer that radiometric dating is cross-checked many ways and that the assumptions are tested, not simply made. Meanwhile, old-earth Christians such as those at BioLogos argue that Genesis was never meant as a science textbook, so no conflict arises.6
Sources
- USGS, Age of the Earth: 4.54 billion years, uncertainty under 1%; lead isotopes in the Canyon Diablo meteorite; oldest Earth rock (Acasta Gneisses) 4.03 Ga; oldest zircons up to 4.3 Ga; Moon rocks 4.4–4.5 Ga; meteorites 4.53–4.58 Ga.
- Talk.Origins Archive, G. Brent Dalrymple, How Old Is the Earth?: radiometric dating "atomic clocks within the rocks", agreement between Earth, Moon, and meteorite ages. (A 1980s-era FAQ, so decay-constant details are dated; the overall result is consistent with the USGS figure.)
- Science Meets Religion, Are Noah's ark and flood literal scientific facts?
- Hal Ostrander, Baptist Standard, 5 reasons Noah's flood doesn't explain a young Earth (relying on geologists Carol Hill and Stephen Moshier).
- Talk.Origins Archive, Young-earth claims and responses.
- BioLogos, an organization of Christians who accept evolution and an old Earth: Genesis 1 and a Babylonian Creation Story (an example of the old-earth Christian view of Genesis).
- Uranium-238 half-life (≈4.47 billion years) is a standard physical constant; the decay demo is a teaching simplification.