I find it humbling that scientists have been able to piece together so much of the story from the Big Bang to you and me. Perhaps even more humbling is earning my living as a scientist who conducts research to identify tiny new bits of this story, so that I can add this new understanding to the remarkable insights so many other scientists have made. I am so impressed by this story that I decided I wanted to try to tell it in a way that makes it accessible to everybody, and not just other scientists. I want to do this because I have met so many people who are unaware of the remarkable progress of science and, because of this unawareness, are distrusting of it. Science can be difficult and intimidating, the language used is often technical, and the concepts can be hard to grasp. Although I personally enjoy reading texts on the chemistry of marine hydrothermal vents, or models of the first microseconds of our universe’s existence, I frequently have to look up the meaning of words despite three decades of working as a professional biologist. In this book, I want to explain things in words that the reader doesn’t have to look up.
Humans are mind-bogglingly complicated. If you or I were to be dismantled, bit by bit, with each type of bit placed in its own pile, the 30 or more trillion cells (the building blocks of all life) that your body consists of would form roughly 220 piles. One pile would consist of red blood cells, another of nerve cells, another of skin cells, and so on. Thirty trillion is a vast number, the first of many vast numbers that we will encounter in this book. It is nearly impossible to comprehend large numbers such as this, but we should at least try. Thirty trillion seconds is equal to 950,000 years, or 9,500 centuries. That amount of time is hard to imagine. We can comprehend a single second easily enough, but imagining 950 millennia in seconds is impossible. Yet 30 trillion is a small number compared with the number we get when we start breaking each cell down into its constituent parts: molecules. On average, each one of your 30 trillion cells contains over 40 million protein molecules that are key to you staying alive. Thirty trillion times forty million is 1.2 billion trillion (twenty zeros). Compared to other types of molecules in your cells, proteins are actually quite rare. The most common molecule in your body is water, with 99 per cent of all molecules and about 60 per cent of your weight (water is lighter than most of the types of molecules in your body) being H2O. The number of molecules in your body gets much larger still when we start to count all of them, and not just proteins. If we were to next dismantle every cell in each of the piles of cells and create new piles of molecules, we would end up with well over 30,000 separate heaps. Some of these heaps would contain vast numbers of molecules, others many fewer. For example, you have only about 0.003 g of cobalt in your body, yet it is essential to keep you healthy. Most cobalt atoms are found in molecules of B12, a vitamin that when deficient can lead to neurological problems, joint pain, blurred vision, and even depression.
We can continue our classification exercise further by breaking up molecules into their constituent parts, atoms, and creating a new set of piles. We would now end up with sixty piles. There would be a pile of carbon atoms, one of iron atoms, another of oxygen atoms, and so on. Next, we break up each atom in each of these piles into its component parts and create a new set of piles, and we end up with a pile of protons, a pile of neutrons and a pile of electrons – the names of the building blocks of atoms. Next, we can break the protons and neutrons into things called up quarks and down quarks, but we cannot divide these strange beasts, nor the electrons, any further.
Early in the universe’s history, these particles emerged from energy, so a final step could be to transform these piles of fundamental particles back into energy. If we were to do that, we would end up with a lot of energy from which all things, including us, developed. The universe started as a microscopic pinprick of intense energy. How did it get from there to you and me? I will describe the steps that had to happen. In summary, and avoiding too many spoilers, some of the energy morphed into the quarks and electrons. When quarks interact, they become more complicated particles called protons and neutrons, which themselves can interact to form even more complicated things called atomic nuclei. These atomic nuclei then interact with electrons to make atoms, which in turn can interact to form molecules. There is a vast number of different types of molecules in the universe, and way more than the 30,000 different types that make up you. Under some circumstances these molecules can interact to form planets, cells and living organisms. Different species of these organisms interact in a range of ways, and over billions of years these interactions between species resulted in some of these organisms evolving to become more and more complicated until, eventually, humans evolved.
Scientists have uncovered our understanding of the universe through observations and experiments. A well-designed experiment is a great way to test an idea or a hypothesis, and to find out new facts. Many people find science daunting, and yet we are all scientific experimentalists at heart. You might not believe me, so I will elaborate. If you have a practical problem to solve, you probably experiment with several different approaches before finding one that works. Do you bribe a child to tidy her bedroom, sternly instruct her to do so, withhold pocket money until it is done, or lead by example? None of these approaches worked with my children, but the application of trial and error brought me more success with cooking. By experimenting with the quantities of different ingredients, and by tweaking the oven temperature and cooking time, I learned to produce the perfect British snack, a scotch egg.
Scientists experiment much in the same way as I do in the kitchen. They tweak conditions in the lab to see how the result is affected. The scientific outcome won’t be a tidy bedroom or a tasty meal, but rather some insight into the way the physical, chemical or biological world works. Some experiments that scientists have conducted are monumental in proportion. The world’s biggest machine is called the Large Hadron Collider, or LHC. It is located at the Conseil Européen pour la Recherche Nucléaire (CERN), and it consists of a 27-kilometre circular tunnel under Switzerland. Huge electrically powered magnets inside the tunnel accelerate particles to a hair’s breadth of the speed of light, the universe’s upper speed limit, before smashing the particles together. Vast detectors in underground cathedral-sized caverns record the outcomes of these collisions. Analysis of the information collected has revealed subatomic particles that the universe is constructed from, and these discoveries have led to some physicists claiming we are on the verge of constructing a ‘theory of everything’ that describes all the interactions of all the particles in our universe. We do not yet have a theory of everything, but physicists, chemists, biologists, mathematicians, historians, archaeologists and researchers in numerous other fields have made astonishing progress.