Category: Science

Part 3 of a series – Emergence

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Here’s a simple diagram of a hydrogen atom. The little black ball is the nucleus, a proton, 10 000 times smaller than the atom as a whole, the white part represents an electron, spread out like a cloud around the nucleus. The proton and the electron were once thought of as fundamental particles that had no underlying structure. For the electron that remains true. The proton on the other hand consists of three quarks, but for the purposes of chemistry we can still think of it as ‘fundamental’.

A hydrogen atom can react with other atoms in quite specific ways. New and more complex behaviour emerges as atoms combine. Here are some of those emergent properties:

• Two atoms of hydrogen can combine as a molecule of hydrogen, a gas that can become explosive when mixed with air.
• Two hydrogen atoms and an oxygen atom can combine as a water molecule. Everyone knows that pure water is safe to drink.
• Four hydrogens and a carbon atom can combine as a molecule of methane gas. This is the domestic gas that we use for cooking and for heating our homes. Methane is also a powerful greenhouse gas, contributing to global heating.
• Three hydrogens and a nitrogen atom can combine as a molecule of ammonia, a poisonous gas that dissolves readily in water.
• Two hydrogens and a suphur atom can combine as a molecule of hydrogen suphide, a gas that smells like rotten eggs.

There are many other molecules that include hydrogen.

Protons, and similar particles called neutrons can combine in larger numbers to make heavier and larger nuclei surrounded by much larger clouds of electrons (we’re leaving out a great deal of detail here). Together, these are the various chemical elements; there are more than 100 different kinds. Sodium, oxygen, phosphorus, chlorine, nitrogen, lead, iron, gold, sulphur, copper, tin and so on.

Chemistry

So – Take 100 different atoms and combine them together in various ways and you can clearly see that many, many different molecules are possible. Imagine 100 different kinds of Lego bricks and you begin to see the range of possibilities. There are rules of chemistry that restrict the combinations that can form, but even allowing for those rules, the number of possible molecules is huge . Here are some examples.

• Sulphuric acid – two hydrogens, a sulphur, and four oxygen atoms
• Table salt – one sodium and one chlorine atom
• Bleach – two chlorine atoms
• Laughing gas – two nitrogens and two oxygen atoms

We see chemistry appearing as soon as we have atoms. Chemistry just isn’t there in the world of subatomic particles like protons, neutrons and electrons. Like every object you can think of, we are made of atoms in complex chemical combinations so it’s quite hard for us to imagine a universe without chemistry. And atoms began emerging very early in the formation of the universe, perhaps 18 000 years after the origin. Chemistry started around 370 000 years as the universe continued to cool and atoms were able to begin combining ever more freely. At first hydrogen, helium and a small amount of lithium were the only elements available, all the others up to iron formed inside stars, while exploding stars (supernovae) generated the heavier elements and scattered these and the lighter elements far and wide. Once that had happened, perhaps 500 million years ago, the full range of atoms were available and chemistry took off in earnest.

Atoms are emergent, beginning to form once the universe became cool enough. And chemistry emerges given the presence of atoms and even lower temperatures. Could atoms and chemistry have been predicted given the presence and behaviour of subatomic particles? Perhaps. But it would have taken a real genius, a physicist with great foresight and imagination. But physicists are made of atoms and complex chemistry – so the real answer must be ‘no’!

That’s the thing about emergence – new kinds of objects and new processes ’emerge’ when the materials and conditions to do so exist. Sometimes emergence is rapid, even sudden. But as we shall see in a future post, sometimes it’s very slow indeed, or long delayed even after the possibility of emergence has existed for a very long time. Chemistry emerged quickly once atoms and low enough temperatures became available. So the opportunity was ‘slow’ to occur, but the emergence was immediate thereafter. We can think of these things separately – emergence opportunity, emergence delay, and emergence rate.

See also:

• Chronology of the universe (Wikipedia)
• Atom (Wikipedia)
• Chemistry (Wikipedia)

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