Wonders of the Universe

CHAPTER 2

STARDUST

THE ORIGINS OF BEING

What are we made of? This is an old question, maybe one of the oldest, and one that thinkers and scientists have been working hard to answer since ancient times. This work continues today, and it may be that by the time you read this book the story of the search for the building blocks of the Universe will have another chapter. Such is the power, excitement and rate of progress of modern science. This chapter is the story of how those building blocks were created in the very early Universe, fused into more complex structures over billions of years in the furnaces of space, and delicately assembled by the forces of nature into planets, mountains, rivers and human beings.

The Large Hadron Collider (LHC) is the highest energy particle accelerator at CERN (the European particle physics laboratory near Geneva, Switzerland). In this huge machine, 27km (17 miles) in circumference, proton beams are accelerated so that they collide head-on. The resultant particles can be detected and recorded so that scientists can then try to understand how they fit together.

DAVID PARKER / SCIENCE PHOTO LIBRARY

The ancient Greeks thought deeply about the question of what we are made of, although they lacked the scientific methodology and technology to arrive at a definitive answer. This led to many competing hypotheses, including some that got close to our modern view: we are all made out of smaller pieces. That there are the smallest building blocks of matter (indivisible basic units that can be fitted together to build the world) was termed the ‘atomic hypothesis’, a theory usually credited to two thinkers – Leucippus and Democritus – in around 400 BC. They held that the world was created from an infinite number of different types of indivisible and indestructible atoms. Each had a different shape, allowing them to fit together neatly to build large objects. So, iron was made of one type of atom, water of another, human flesh of another, and so on. They thought atoms possessed the properties of their real-world substances – water atoms were slippery, while metal ones were shaped so that they locked together to produce very hard substances. We now know that this is not only wrong, but a gross overcomplication. While their hypothesis correctly stated that the world is made from smaller pieces, you don’t need an infinite number of atom types to build the complexity around us. A human is made of the same stuff as a rock; a fish of the same stuff as the Earth; the sky of the same stuff as the oceans. Enumerating the basic building blocks and understanding how they fit together is the province of the science of particle physics, and this quest continues at the Large Hadron Collider at CERN, in Geneva.

By early 2011, we had discovered that the Universe is composed of twelve basic building blocks, only three of which are required to build everything on our planet, including our bodies. These three components, known as the up and down quarks and the electron, can be assembled into the more familiar protons and neutrons – two up quarks and a down quark make a proton, and two down quarks and an up make up a neutron. In turn, the protons, neutrons and electrons make up the chemical elements – ninety-four of which are known to occur naturally – including the basic chemical elements hydrogen, carbon, oxygen, iron, gold and silver