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| c. 13.7 billion years ago |
| | | Hydrogen and helium nuclei form in the first three minutes, with perhaps another 300,000 years before they combine with electrons to form atoms | |
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| c. 13 billion years ago |
| | | As gravity exerts its pressure within parts of the expanding fireball, subnuclear particles merge into more complex elements | |
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| c. 450 BC |
| | | Empedocles states that all matter is made up of four elemental substances - earth, fire, air and water | |
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| c. 420 BC |
| | | The Greek philosopher Democritus declares that matter is composed of indivisible and indestructible atoms | |
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| c. 380 BC |
| | | A Greek text, attributed to Polybus, argues that the human body is composed of four humours | |
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| c. 300 BC |
| | | Epicurus postulates a universe of indestructible atoms in which man himself is responsible for achieving a balanced life | |
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| c. 250 BC |
| | | The first alchemists, working in Alexandria, are also the world's first experimental chemists | |
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| c. 1040 |
| | | A Chinese manual on warfare includes the earliest known description of gunpowder | |
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| 1648 |
| | | The Dutch chemist Jan Baptist van Helmont suggests that there are insubstantial substances other than air, and coins a name for them - gases | |
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| 1662 |
| | | British chemist Robert Boyle defines the inverse relationship between pressure and volume in any gas (subsequently known as Boyle's Law) | |
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