Science: 50 Essential Ideas

By Anne Rooney

An essential addition to any science lover's library.

The perfect gift for budding scientists.

• Language: English
• Publisher: Arcturus Publishing
• Release date: Jan 1, 2023
• ISBN: 9781398821637

Anne Rooney

Anne Rooney writes books on science, technology, engineering, and the history of science for children and adults. She has published around 200 books. Before writing books full time, she worked in the computer industry, and wrote and edited educational materials, often on aspects of science and computer technology.

Book preview

1. Uncuttables

The atomic theory of matter

If you look at everything surrounding you right now, you’ll see a huge variety of different matter – and some you won’t see at all, as the air isn’t visible. We now have a well-established theory that matter is made of tiny particles called atoms, fully supported with evidence. The Ancient Greeks are the first people known to have thought about the organization of matter.

‘UNCUTTABLES’

Our modern word ‘atom’ comes from the Ancient Greek atomos, an adjective that means ‘uncuttable’. The philosophers Leucippus and Democritus are credited with introducing the idea 2,500 years ago that matter is made of very tiny particles that can’t be further divided. According to Democritus, everything is made of tiny particles that exist in a void. These particles, atoms, can’t be created or destroyed, but they can move around. Atoms, he claimed, are of different sizes, shapes and orientations and can temporarily link to others, providing the variety of different types of matter. As the clusters of atoms break up and the atoms regroup into new clusters, matter changes.

Paradoxes of divisibility

Robert Boyle was a proponent of atomism in the 17th century.

BACK TO BASICS

Atomism next surfaced in 17th-century Europe, particularly in the work of Anglo-Irish chemist Robert Boyle. Boyle regarded atoms as all being alike in respect of their impenetrability, but differing in size, shape and motion. Size and shape are primary properties of matter. Secondary properties, including colour, smell, elasticity, density and so on, he considered to be produced by the particular combination and arrangement of atoms. Boyle also referred to ‘natural minima’ or ‘least parts’, as being the smallest particles of a substance that have the substance’s secondary properties. These weren’t (usually) the same as atoms, though they might sometimes come close to our concept of molecules. For Boyle, as for the ancients, all atoms were made of the same material, regardless of the type of matter they eventually found themselves in.

This view was shared by Isaac Newton, too. He made atoms subject to his laws of movement, so that between collisions, atoms would observe the laws of momentum and inertia. Newton accounted for the density of matter of different types by how closely packed atoms are in it, but he also allowed that there is a lot of space within atoms, as light can pass through gold leaf even though gold is very dense. But Newton introduced forces to the purely mechanistic atoms of Boyle. Newton’s atoms could be held together in matter by forces of attraction, or could dissociate because of repulsion. This idea could explain how one chemical would displace another in a reaction – if there was a greater attraction between A and C than between A and B, A would combine with C and B would be somehow thrown out. This explanation, though, couldn’t be used to make predictions: it couldn’t tell you what would happen between A and D.

In the 18th century, forces became more important in all areas of science. Ruđer Bošković, from what is now Croatia, went so far as to strip atoms of materiality and make them centres of force – including gravity – so that they could still confer mass on matter.

ATOMS, AT LAST

A connection between atoms and chemistry was successfully made, at last, by the English chemist John Dalton. He suggested that the chemical elements are made up of ‘ultimate particles’, or atoms, with each element having its own unique design of atom. When Antoine Lavoisier compiled the first modern list of elements (see page 28), he didn’t link the idea to atoms.

Dalton used the proportions in which chemicals combine to tell him the relative atomic weights of elements, using hydrogen as the basis (atomic weight 1). He was mistaken when he assumed that elements combined in the ratio 1:1 – so assuming one hydrogen atom combined with one oxygen atom to make water, rather than two hydrogen atoms with one oxygen atom. He dropped the traditional assumption, starting with Democritus, that all atoms are made of the same substance and differ only in properties such as size and mass. In Dalton’s system, atoms of different elements were all made of different types of stuff.

John Dalton first proposed that each chemical element has its own unique design of atom.

Dalton devised symbols for the atoms of 20 elements. Of these, six are now recognized as compounds.

Final proof that atoms exist came with Albert Einstein’s explanation of an observation made by the botanist Robert Brown in 1827. While examining pollen grains under a microscope, Brown had seen them moving randomly around on their own. It became known as Brownian motion, but its cause was unknown. Brown had been unable to explain it, though he’d seen the same movement with other tiny particles, including some that were not from living things. In 1905, Einstein explained the motion: it’s produced by the tiny light particles being jostled by the random movements of water molecules. The molecules are too small to see, but we see the effect of their collisions with pollen grains.

2. Into the void

The existence of a vacuum

We now take for granted that we can create a vacuum – a space containing nothing. But for a long time, the idea of the void was highly contentious.

THE SPACE WITHIN MATTER

The idea that there might be empty space was first debated by the Ancient Greeks. When Democritus described a world made up of atoms, he had them existing in a void, something we would recognize now. But not all thinkers agreed with him. On one side were those, like Parmenides and Aristotle, who claimed that there is no empty space, but matter is entirely continuous. Parmenides argued on this basis that movement and change don’t exist. As it’s fairly clear that things do move and change, Democritus’s view of a world where atoms can move through the void sounds more compelling.

The possibility or impossibility of a void remained a philosophical debate for many centuries. In some cases, it even seemed to be ruled by the meaning of words: nothing can’t exist because ‘existence’ requires the presence of some matter. Eventually science won out over philosophy with a practical demonstration. In 1654, the German scientist Otto von Guericke resolved the question by inventing and demonstrating a pump to create a vacuum. He fitted two metal hemispheres together to make a closed sphere and withdrew all the air from it. In a spectacular public demonstration, two teams of horses were unable to pull the hemispheres apart. The reason is not that the vacuum ‘sucks’ the halves together, but that the pressure of the air outside the hemispheres pushes them hard together. The horses are trying to pull against air pressure.

As evidence emerged of the existence of atoms, our understanding of the world returned to something like Democritus’s void containing particles of matter. Where atoms are more densely packed, the matter they make tends to be a solid. In between solid objects, there could be liquids or gases (or empty space). In liquids and gases, atoms are more widely spaced and move more freely.

OUTER SPACE

Some of the Ancient Greeks accepted that outside Earth there might be empty space, and most people now think of outer space as a vacuum. It is close to being a perfect vacuum. There is very little matter in the gaps between stars, planets and other bodies. Gravity draws any stray matter towards other clumps of matter, making space very uneven in terms of the density of matter in it. There are very dense concentrations of matter (such as Earth) and then some very empty areas between star systems and between galaxies. The average density of space is just under six protons per cubic metre, but in the cosmic void – the space between crowded areas – it’s less than one atom per cubic metre.

Von Guernicke’s dramatic demonstration of the Magdeburg hemispheres proved a vacuum is possible.

In quantum mechanics, a vacuum must have no matter particles and also no photons. As space is everywhere, subject to the cosmic microwave background radiation (see page 44), there is no true vacuum in this sense.

3. Pass it on

The principle of heredity

It’s obvious by looking around at family, pets, farm animals and even in the garden that one generation of organisms passes on features to the next. Many of us look like our parents, our children and our siblings. As humans, we have exploited inherited characteristics in agriculture for millennia, since long before we had any understanding of how characteristics were passed on.

The earliest farmers bred from their most productive animals and saved seed from their best crop plants, slowly changing the nature of crops and livestock so that now they bear little resemblance to their wild ancestors. The first investigation of patterns of inheritance, though, came fewer than 200 years ago.

THE MONK AND THE PEAS

In a monastery garden in Brno (now in the Czech Republic) in 1857, an Augustinian monk called Gregor Mendel began a careful study of pea plants to investigate the inheritance of characteristics. He focused on seven different features of the plants, including flower colour, seed colour and seed shape. For each characteristic he began by breeding two lines of peas, one with each version of a feature: for instance, white flowers or mauve flowers. Once he had established his true-breeding lines for each feature, he began to cross-breed plants and keep track of the outcomes.

He found that in all seven features, the first generation of crosses (for instance, tall pea × short pea), produced only one form (tall pea, in this case). Breeding from the next generation, he found a mix, but always in the ratio 3:1 (so three tall peas to one short pea). He called the feature that was always seen in the first generation, and was most frequent in the second, the dominant trait. The other he called the recessive trait. He concluded that a pea plant has two heritable ‘factors’ for each feature. A dominant factor will always mask a recessive factor, so if a plant inherits one tall (dominant) and one short (recessive) factor, it will grow tall. For a recessive factor to be expressed, the plant needs two copies of it.

Mendel explained inheritance in terms of the two parents each contributing one factor to the offspring. If both are dominant, or one is dominant and one recessive, the offspring will show the dominant trait. If both are recessive, it will show the recessive trait. This was clear to him from the ratio of features in the second generation.

Inheritance of height in pea plants over two generations.

A mystery unravelled

MIX AND MATCH

Mendel found that the features he was studying were inherited separately, so a plant might have the recessive trait for height but the dominant trait for flower colour, for example. This led him to conclude that the factors for different features are split separately when egg and sperm cells (called gametes) are created. Each new pea plant gets, separately, a factor for each feature from each parent. It’s a matter of chance which of each parent plant’s two factors goes into each gamete and so which a particular pea plant inherits.

Although Mendel had worked out the mathematics of inheritance, he had no idea of the mechanics of it. How exactly did an organism inherit features from its parents? That remained unknown. Mendel published his findings in 1866, with data from 30,000 pea plants, but for 35 years it lay unnoticed.

FROM MENDEL TO MORGAN

In 1869, just a few years after Mendel published his work, the Swiss chemist Friedrich Miescher discovered a substance in the nuclei of white blood cells which he named nuclein. It is now known as DNA. He realized it was important but had no idea what it did. No one made the connection with Mendel’s work on heredity. Indeed, no one made any connections at all with Mendel’s work until 1900 when three botanists independently rediscovered it and carried out experiments that supported his findings. It still didn’t immediately appeal to evolutionary biologists as Charles Darwin had talked of evolution coming about through the blending of features of both parents, and clearly Mendel’s model didn’t allow any blending.

Soon after, the young American biologist Walter Sutton closely observed meiosis (the cell-division process that makes gametes) in grasshopper cells and realized that the chromosomes split up in exactly the way that Mendel’s explanation required. He suggested in 1902 that chromosomes are how Mendelian inheritance works. A pair of chromosomes has two genes for each characteristic. When the chromosomes separate in meiosis, each chromosome has one gene for each characteristic. When an egg is fertilized, a corresponding chromosome contributed by the other parent brings the second gene. This is now known as the Sutton–Boveri theory of inheritance. (Theodor Boveri came up with much the same idea at the same time.)

Thomas Morgan demonstrated this conclusively through experiments with fruit flies. In 1911, he showed that particular genes are carried on particular chromosomes. Morgan’s PhD student, Alfred Sturtevant, took this further, producing the first gene map, which shows where specific genes appear on chromosomes of the fruit fly.

By explaining the biochemical mechanism of inheritance, Mendel and those who came after him provided an explanation for evolution, but also opened the door for new developments previously undreamt of: genome sequencing, genetic engineering and genetic medicine.

Morgan and Sturvesant mapped regions of a fruit fly gene to the effects of different mutations in the fly.

4. Cutting the uncuttables

Atomic structure

For centuries, everyone accepted that atoms are ‘uncuttable’ – it was part of their definition. But we now know that atoms are made of subatomic particles: one or more electrons in orbit around a nucleus that contains protons and – in all elements except hydrogen – neutrons. The protons and neutrons are themselves made up of quarks.

MAKING MODELS

The first subatomic particle discovered was the electron, found by J.J. Thomson in 1897. He determined that the ‘cathode rays’ physicists had been experimenting with were actually streams of tiny, negatively charged particles, much lighter than the

Reviews for Science

[pomo58 · Rating: 5 out of 5 stars]

Science: 50 Essential Ideas, by Anne Rooney, is a simple and straightforward book that serves as an excellent introduction to some basic scientific concepts.This book is not, and doesn't set out to be, an in-depth look at these ideas. This volume can serve many purposes. The first that come to mind for me are an introductory text for young readers (ideally with parents/guardians reading with them) and as an overview for those who just want a better understanding of science in general.For any reader this can act as a jumping off point for whatever concepts intrigue them. While not having a bibliography each entry has key words and names that can be used to search online or in a textbook. From there, the possibilities are endless. I would certainly recommend this for anyone wanting to have a basic intro to important science ideas, whether for themselves or their children. I also think those of us with education in the sciences can benefit from having a book that makes us step back and see these concepts from a general perspective, we can often get bogged down in whatever specific areas we like and lose the bigger picture that first sparked our interest. We can then, one hopes, share that excitement with others.Reviewed from a copy made available by the publisher via NetGalley.