Über die Autorin bzw. den Autor

PAUL HALPERN, PhD, is Professor of Physics at the University of the Sciences in Philadelphia. He is the author of numerous books, including The Great Beyond and What's Science Ever Done For Us?, both available from Wiley.

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"Paul Halpern makes the search for mysterious particles pertinent and exciting by explaining clearly what we don't know about the universe, and offering a hopeful outlook for future research."
—Publishers Weekly

"Paul Halpern is a gifted writer who brings science and scientists alive. This is a wonderful introduction to the world of high-energy physics, where gigantic machines and tiny particles meet."
—Kenneth Ford, retired director of the American Institute of Physics and author of The Quantum World: Quantum Physics for Everyone

"Professor Paul Halpern takes the reader on a stimulating odyssey on topics ranging from particle physics and dark matter to unexplored dimensions of space. . . . Buy this book and feed your mind!"
—Dr. Cliff Pickover, author of Archimedes to Hawking and The Math Book

"With clarity and a Sagan-esque gift for explanation, Paul Halpern traces the story of how physicists use immensely powerful machines to probe the deepest mysteries of existence. Halpern also conclusively debunks the ludicrous claims that the Large Hadron Collider and other high-energy physics experiments threaten to destroy anything—except our residual ignorance about the nature and workings of our wondrous universe."
—Mark Wolverton, author of The Science of Superman and A Life in Twilight: The Final Years of J. Robert Oppenheimer

The biggest news in science today is the world's largest and most powerful particle-smasher, the Large Hadron Collider, and the anticipation of finally discovering the Higgs boson particle. But what is the Higgs boson and why is it often referred to as the God particle? Why are the Higgs and the LHC so important? Getting a handle on the science behind the LHC can be difficult for anyone without an advanced degree in particle physics, but you don't need to go back to school to learn about it. In Collider, award-winning physicist Paul Halpern provides you with the tools you need to understand what the LHC is and what it hopes to discover.

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Collider

John Wiley & Sons

Chapter One

When in the height heaven was not named, And the earth beneath did not yet bear a name, And the primeval Apsu, who begat them, And chaos, Tiamut, the mother of them both Their waters were mingled together, And no field was formed, no marsh was to be seen; When of the gods none had been called into being, And none bore a name, and no destinies were ordained ... —ENUMA ELISH, THE BABYLONIAN EPIC OF CREATION, TRANSLATED BY L. W. KING

Hidden among the haze of cosmic dust and radiation, buried in the very soil we walk upon, locked away in the deep structure of everything we see, feel, or touch, lie the secrets of our universal origins. Like the gleaming faces of a beautiful but impenetrable diamond, each facet of creation offers a glimpse of a wonderful, yet inscrutable, unity. With probing intellect, humankind longs to cut through the layers and reach the core of truth that underlies all things. What is the universe made of? What are the forces that affect our universe? How was the universe created?

Ancient Greek philosophers offered competing explanations of what constitutes the tiniest things. In the fifth century BCE, Leucippus and Democritus, the founders of atomism, argued that materials could be broken down only so far before their basic constituents would be reached. They imagined these smallest, unbreakable pieces, or "atoms," as possessing a variety of shapes and sizes, like an exotic assortment of pebbles and shells. Another view, proposed by Empedocles, is that everything is a mixture of four elements: fire, water, air, and earth. Aristotle supplemented these with a fifth essence, the void. For two millennia these classical elements were the assumed building blocks of creation until scientific experimentation prodded Europe toward an empirical view of nature.

In his influential book The Sceptical Chymist, Robert Boyle (16271–691) demonstrated that fire, air, earth, and water couldn't realistically be combined to create the extraordinary range of materials on Earth. He argued for a new definition of the term "element" based on the simplest ingredients comprising any substance. Chemists could identify these, he argued, by breaking things down into their most basic parts, rather than through relying on philosophical speculation. Boyle's clever insight challenged experimenters to discover, through a variety of methods, the true chemical elements—familiar to us (in no particular order) as hydrogen, oxygen, carbon, nitrogen, sulphur, and so forth. Whenever children today combine assorted liquids and powders in their chemistry sets, set off bubbling reactions, and concoct colorful, smelly, gooey by-products, they owe a debt to Boyle.

Boyle was an ardent atomist and a meticulous experimenter. Refusing to accept the hypothesis on faith alone, he developed a clever experiment designed to test the concept that materials are made of small particles—which he called corpuscles—with empty space between them. He started with a curved glass tube, exposed to the air on one end and closed on the other. Filling the open end with mercury, he trapped some of the air in the tube and pressed it into a smaller and smaller volume. Then, by slowly removing the mercury, he noted that the trapped air expanded in inverse proportion to its pressure (a relationship now called Boyle's law). He reasoned that this could happen only if the air was made of tiny components separated by gaps.

Manchester chemist John Dalton was an earnest young Quaker whose research about how different substances react with one another and combine led him to the spectacular insight that each chemical element is composed of atoms with distinct characteristics. Dalton was the first, in fact, to use the word "atom" in the modern sense: the smallest component of a chemical element that conveys its properties.

Dalton developed a clever visual shorthand for showing how different atoms combine. He depicted each type of element as a circle with a distinctive mark in the center—for example, hydrogen with a dot, sodium (which he called "soda") with two vertical lines, and silver with the letter "s." Dalton counted twenty elements; today we know of ninety-two natural elements and at least twenty-five more that can be produced artificially. By arranging his circular symbols into various patterns, he showed how compounds such as water and carbon dioxide could be assembled from the "Lego blocks" of elements such as hydrogen, oxygen, and carbon. In what he called the law of multiple proportions, he demonstrated that the elements forming particular substances always combined in the same fixed ratios.

Dalton also attempted to characterize atoms by their relative weights. Although many of his estimates were off, his efforts led to simple arithmetical ways of understanding chemistry. In 1808, Scottish chemist Thomas Thomson combined oxalic acid (a compound of hydrogen, carbon, and oxygen) with several different elements, including strontium and potassium, and produced a variety of salts. Weighing these salts, he found proportionalities corresponding to differences in the elements he used. Thomson's results, published in his book A System of Chemistry, helped Dalton's theories gain wide acceptance in the scientific community.

One thing that Dalton's theories couldn't do was predict new elements. Arranging atoms in order of their relative weights didn't offer enough information or impetus for scientists to infer that others existed. It's as if a mother brought three of her sons to a new school to register them and reported only their names and ages. Without saying more about her family, the teachers there would have no reason to believe she had other kids that were older, younger, or in between.

Indeed the family of elements was much larger than Dalton surmised. By the mid-nineteenth century the number of known elements had tripled to about sixty. Curiously, some of these had shared properties—even ones associated with much different atomic weights. For example, sodium and potassium, though separated in terms of weight, seemed to react with other substances in similar ways.

In the late 1860s, Russian chemist Dmitry Mendeleyev decided to write a state-of-the-art chemistry textbook. To illustrate the great progress in atomic theory, he included a chart depicting all of the then-known elements in order of weight. In a bold innovation, he listed the elements in table form with each row representing elements with similar properties. By doing so, he illustrated that elements fall into patterns. Some of the spaces in what became known as the periodic table he left blank, pointing to elements he predicted would later be discovered. He was absolutely right; like a solved Sudoku puzzle, all of the gaps in his table were eventually filled.

Science didn't realize the full significance of Mendeleyev's discovery until the birth of quantum mechanics decades later. The periodic table's patterns reveal that the Democritean term "atom" is really a misnomer; atoms are indeed "breakable." Each atom is a world unto itself governed by laws that supersede Newtonian mechanics. These laws mandate a hierarchy of different kinds of atomic states, akin to the rules of succession for a monarchy. Just as firstborn sons in many kingdoms assume the throne before second-born sons, because of quantum rules, certain types of elements appear in the periodic table before other kinds.

The atom has sometimes been compared to the solar system. While this comparison is simplistic—planetary orbits don't obey quantum rules, for one thing—there are two key commonalities. Both have central objects—the Sun and what is called the atomic nucleus—and both are steered by forces that depend inversely on the squares of distances between objects. An "inverse-square law" means that if the distance between two objects is doubled, their mutual force diminishes by a factor of four; if their distance is tripled, their force weakens ninefold, and so forth. Physicists have found that inverse-square laws are perfect for creating stable systems. Like a well-designed electronic dog collar it allows some wandering away from the house but discourages fleeing the whole property.

While scientists like Boyle, Dalton, and Mendeleyev focused on discovering the ingredients that make up our world, others tried to map out and understand the invisible forces that govern how things interact and transform. Born on Christmas Day in 1642, Sir Isaac Newton possessed an extraordinary gift for finding patterns in nature and discerning the basic rules underlying its dynamics. Newton's laws of mechanics transformed physical science from a cluttered notebook of sundry observations to a methodical masterwork of unprecedented predictive power. They describe how forces—pushes and pulls—affect the journeys through space of all things in creation.

If you describe the positions and velocities of a set of objects and delineate all of the forces acting on them, Newton's laws state unequivocally what would happen to them next. In the absence of force or with forces completely balanced, nonmoving objects would remain at rest and moving objects would continue to move along straight lines at constant speeds—called the state of inertia. If the forces on an object are unbalanced, on the other hand, it would accelerate at a rate proportional to the net force. The extent to which an object accelerates under the influence of a net force defines a physical property called mass. The more massive a body, the harder it is for a given force to change its motion. For example, all other factors being equal, a tow truck's tug would have much less effect on a monstrous eighteen-wheeler than it would on a sleek subcompact car.

Newton famously showed that gravity is a universal force, attracting anything with mass to anything else with mass. The moon, the International Space Station, and a bread crumb pushed off a picnic table by an ornery ant are all attracted to Earth. The more massive the objects, the greater their gravitational attraction. Thus, mass serves two purposes in physics—to characterize the strength of gravity and to determine the accelerating effect of a force. Because mass takes on both roles, it literally cancels out of the equation that determines the effect of gravitational force on acceleration. Therefore bodies accelerate under gravity's influence independent of their masses. If it weren't for the air whooshing by, an aquatic elephant and a mouse up for a challenge would plunge from the high diving board into a swimming pool straight below them at the same rate. The fact that gravitational acceleration doesn't depend on mass places gravity on different footing from any other force in nature.

The concept of attractive forces offers a means by which large objects can build up from smaller ones—at least on astronomical scales. Take scattered bits of slow-moving material, wait long enough for attractive forces to kick in and they'll tend to clump together—assuming they aren't driven apart by even stronger repulsive forces. Attraction offers a natural way for matter to build up from tiny constituents. Therefore it's not surprising that Newton subscribed to the atomist view, believing that all matter, and even light, is made up of minute corpuscles.

In his treatise on optics Newton wrote, "It seems probable to me that God in the beginning formed matter in solid, massy, hard, impenetrable, movable particles of such sizes and figures and with such other properties and in such proportion to space as most conduced to the end for which he formed them. And that these primitive particles being solids, are incomparably harder than any porous bodies compounded of them, even so hard as never to wear or break in pieces; no ordinary power being able to divide what God himself made one in the first creation."

Newton's belief that God fashioned atoms reflected his deeply held religious views about the role of divinity in creation. He believed that an immortal being needed to design, set into motion, and tweak from time to time an otherwise mechanistic universe. His example, in line with the views of the similarly devout Boyle, showed that atomism and religion were compatible.

As Newton demonstrated, the solar system is guided by gravity. Gravity is important on astronomical scales, but it is far too weak a force on small scales to hold atoms together. The force that stabilizes atoms by holding them together is called the electrostatic force, part of what is known as the electromagnetic interaction. While gravity depends on mass, the electrostatic force affects things that have a property called electric charge.

The renowned eighteenth-century American statesman Benjamin Franklin was the first to characterize electric charge as either positive or negative. Influenced by Franklin and Newton, British natural philosopher Joseph Priestley proposed that the electrostatic force, like gravity, obeys an inverse-square law, only depending on charge instead of mass. While gravity always brings objects together, the electrostatic force can be either attractive or repulsive; opposite charges attract and like charges repel. These conjectures were splendidly proven in the 1780s by French physicist Charles-Augustin de Coulomb, for whom the law describing the electrostatic force is named.

Like the electrostatic force, magnetism is another force that can be either attractive or repulsive. The analogue of positive and negative electric charges is north and south magnetic poles. The ancients were familiar with magnetized iron, or lodestone, and knew that by suspending such a material in the air it would naturally align with the north-south direction of Earth. The term "magnetism" derives from the Greek for lodestone, just as "electricity" stems from the Greek for amber, a material that can be easily electrically charged.

Newton's model of forces envisioned them as linking objects by a kind of invisible rope that spans the distance between them. It's like a boy in a first-floor alcove of a church pulling a thin cord that manages to ring a bell in its tower. We call this concept action at a distance. In a way, it is an extension of the Democritean concept of atoms moving in an absolute void. Somehow, two things manage to influence each other without having anything in between to mediate their interaction.

British physicist Michael Faraday found the notion of action at a distance not very intuitive. He proposed the concept of electric and magnetic fields as intermediaries that enable electric and magnetic forces to be conveyed through space. We can think of a field as a kind of ocean that fills all of space. Placing a charge in an electric field or pole in a magnetic field is like an ocean liner disturbing the water around it and disrupting the paths of other boats in its wake. If you were kayaking off the coast of California and suddenly began rocking back and forth, you wouldn't be surprised to see an approaching vessel generating major waves. Similarly, when a charge or pole feels a force it is due to the combined effect on the electric or magnetic field of other charges or poles.

A child playing with a bar magnet in a room illuminated by an electric lightbulb would probably have little inkling that the two phenomena have anything to do with each other. Yet as Danish physicist Hans Christian Ørsted, Faraday, and other nineteenth-century researchers experimentally explored, electrical and magnetic effects can be generated by each other. For example, as Ørsted showed, flipping an electrical switch on and off while placing a compass nearby can deflect its magnetic needle. Conversely, as Faraday demonstrated, jiggling a bar magnet back and forth near a wire can create an electrical current (moving charge) within it—a phenomenon called induction. So a clever enough child could actually light her own play space with her own bar magnet, bulb, and wire.

It took a brilliant physicist, James Clerk Maxwell, to develop the mathematical machinery to unite all electrical and magnetic phenomena in a single theory of electromagnetism. Born in Edinburgh, Scotland, in 1831, Maxwell was raised on a country estate and grew up with a fondness for nature. He loved walking along on the muddy banks of streams and tracing their meandering courses. In his adult life, as a professor at King's College, University of London, he became interested in a different kind of flow, the paths of electric and magnetic field lines fanning out from their sources.

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Excerpted from Colliderby Paul Halpern Copyright © 2010 by John Wiley & Sons, Ltd. Excerpted by permission of John Wiley & Sons. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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