What separates a human from an iron mine?
A human and iron ore are both made of atoms, and both are rich in oxygen. The difference lies not in the atoms but in their arrangement, in the information that builds it and in the flow of energy that keeps it standing. This page shows the difference with interactive graphics.
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Same atoms, different mix
Each square is one percent. By mass, two-thirds of a human is oxygen; by number of atoms, hydrogen is the majority.
Human body
- Oxygen (O) 65%
- Carbon (C) 18.5%
- Hydrogen (H) 9.5%
- Nitrogen (N) 3.2%
- Calcium (Ca) 1.5%
- Phosphorus (P) 1%
- Other 1.2%
Iron ore (hematite, Fe₂O₃)
- Iron (Fe) 69.9%
- Oxygen (O) 30.1%
Real iron ore also contains sand, clay and other minerals; pure hematite is used for comparison.
What they share
Your body holds about 4 grams of iron, and iron ore is full of oxygen. An iron atom in your blood and one in a mine are identical: both were made in dying stars.
So where is the difference?
Order
Iron ore is a crystal: the same small pattern repeated billions of times. You are a non-repeating, layered order: molecules, membranes, cells, tissues, organs. Like diamond and graphite: same atom, different arrangement, a completely different thing.
Information
Each of your cells carries two copies of a DNA recipe about 3 billion letters long. The recipe says how atoms should be arranged, and it is passed on to your children. In 1944 the physicist Erwin Schrödinger described hereditary material as an “aperiodic crystal”: an order that can carry information because it does not repeat.
Energy
A stone left alone stays a stone. Your order stays standing only by constantly spending energy: about 2,000 kilocalories a day, roughly a 100-watt light bulb. Cut the flow of energy and the order falls apart.
Flow
Your atoms keep changing: you breathe, eat, drink and shed. Most of the atoms in your body are swapped for others within a few years (with exceptions such as tooth enamel and some brain cells). You are less an object than a pattern: like a waterfall or a candle flame, the shape stays while the material flows through.
Copying and change
Living things make copies of themselves; the copies come out slightly different, and those that fit their surroundings best multiply more. Over billions of years this process led from bacteria to humans. A crystal can grow too, but it can only repeat the same pattern.
Order and energy: try it yourself
On the left, a crystal: the same pattern repeats and stays put when left alone. On the right, a living pattern: particles constantly flow in and out, and the shape holds only while energy flows. Cut the energy and watch.
Energy is flowing: the shape holds.
Your atoms: count them
Enter your weight and we'll estimate the atoms in your body. Nothing leaves this page.
One more link: living things made iron ore
The world's largest iron deposits formed 2.5–1.8 billion years ago. Oxygen released by photosynthesising bacteria rusted the iron dissolved in the ocean; the rust sank and piled up layer upon layer. So the ore we mine to make steel today was partly made by those early life forms, your very distant relatives.
The story of iron →Frequently asked questions
If everything is made of atoms, what separates a human from an iron mine?
Less the kind of atoms than their arrangement. Iron ore is a crystal that repeats the same small pattern and stays that way if left alone. A human is an arrangement built from the information in DNA, kept standing only by constant energy use, with atoms constantly replaced, and able to copy itself. Like diamond and graphite: same atom, different order, a completely different thing.
Where did the atoms in our bodies come from?
Hydrogen comes from the Big Bang; elements such as carbon, nitrogen, oxygen, calcium and iron come from inside stars and their explosions. That is why “we are stardust” is not a metaphor but literally true.
What is the difference between steel and iron?
Steel is iron with less than 2% carbon added. The carbon atoms make it hard for layers of iron atoms to slip, so steel is much harder and tougher than pure iron.
Do atoms die?
Almost all the atoms in your body are stable and can last unchanged for billions of years. When a living thing dies, its atoms do not disappear; they pass into soil, air and other living things and join new arrangements.