Instant Egghead Guide: The Universe: The Universe (Instant Egghead Guides) - Softcover

Instant Egghead Guide: The Universe
CHAPTER ONE MATTER AND ENERGY ELECTRONS, PROTONS, AND NEUTRONS THE BASICS The world, as any egghead knows, is made of atoms. And the raw ingredients of atoms are called subatomic particles. We encounter a number of particles in this book, but to understand matter, from the book in your hands to the core of a star, we need a good grasp of these three: electrons, protons, and neutrons. So let's get to know them. The electron is an elementary particle, which means it can't be broken down into other particles. It is very tiny--it may have no size at all, in fact--and has very little mass. (All matter has mass, which is a measure of the oomph it takes to get something moving.) An electron carries a negative electric charge, which is the opposite of a positive charge. Like charges repel; opposite charges attract. Unlike electrons, protons and neutrons are not elementary particles; they are made of smaller particles called quarks, which we get to later. Protons are positively charged, and neutrons are electrically neutral. Protons and electrons pair up due to their electric attraction but the proton dominates the relationship because it has the mass of some 1,800 electrons. Neutrons are slightly heavier than protons but otherwise identical. ON THE FRONTIER Everything we see, including Earth and the stars, is made of atoms, but as it turns out, there's a lot of additional matter we can't see. Scientists call it dark matter, and it's completely invisible. The only reason we think it's there is because of its effects on the other stuff in the universe. Figuring out the identity of dark matter is one of the biggest challenges in science today. But let's put that on the shelf for the moment. Studying the behavior of ordinary matter will take us a long way toward understanding how the universe came to be the way it is. COCKTAIL PARTY TIDBITS All subatomic particles of a single type are identical. It's impossible to tag one of them the way you would tag a penguin or a seal to study its migratory patterns. So if you discover something about one particle, it applies to all the rest. It's a law of nature! The charge of an electron is one of the fundamental physical constants. We can't explain it from more basic principles; we can only measure it. American physicists Robert Millikan and Harvey Fletcher were the first to measure the charge of an electron in 1909 by suspending droplets of oil in an electric field. (They were slightly off but, hey even eggheads make mistakes.) ATOMS THE BASICS The structure of an atom is a bit like the solar system. At the center is a dense nucleus made of protons and neutrons. Electrons orbit the nucleus in a complicated way that is more like a cloud than like planets. (But more on that later.) The nucleus is positively charged, so it attracts electrons to it, one for each proton. As long as the number of protons and electrons is the same, the atom is electrically neutral, which is good, because otherwise we'd be walking around shooting sparks everywhere. If an atom gains or loses electrons, say from friction or heat, it becomes electrically charged and we call it an ion. Atoms come in 94 naturally occurring types, called elements, distinguished by the number of protons in the nucleus, called the atomic number. Hydrogen, with a single proton, is the lightest element. Because electrons are so light, more than 99.9 percent of an element's mass comes from its protons and neutrons. All elements exist in multiple forms with slightly different masses, called isotopes. The difference is the number of neutrons in the nucleus. Some isotopes are unstable; they break down into other elements in a process called radioactive decay. All natural elements have radioactive isotopes mixed in with them. Researchers can estimate the age of fossils, space rocks, andother ancient samples by comparing the ratio of isotopes in the specimen. ON THE FRONTIER Because atoms are so tiny, we should be forgiven for needing thousands of years to prove their existence. In the nineteenth century, scientists found they could explain the behavior of gases and liquids by assuming that atoms knocked one another around like billiard balls. Today we can detect atoms directly thanks to special tools such as the electron microscope, which scans surfaces using a thin beam of electrons. In 2008, University of California, Berkeley, researchers boosted the sensitivity of electron microscopy enough to pick out single hydrogen atoms--the lightest of all--suspended on an extremely flat surface. COCKTAIL PARTY TIDBITS If you could enlarge an apple to the size of Earth, the atoms inside it would be as big as the original apple. Bite on that! The idea of atoms dates back thousands of years to early eggheads such as Democritus of Greece, who argued that matter must be made of particles that can't be split into smaller pieces. (The word atom comes from the Greek for "uncuttable.") They were half right. Atoms are the smallest units of elements, not matter. THE ELEMENTS THE BASICS Elements are substances that can't be broken down into simpler substances. We classify the elements based on their location in the periodic table of elements, bequeathed to schoolchildren everywhere by Russian chemist Dmitri Mendeleev in 1869. Today we know they represent different types of atoms. The modern periodic table is arranged in rows and columns. Elements in the same column have similar chemical properties. For example, the alkali metals--lithium, sodium, potassium, and so on--are so highly reactive that they explode on contact with water; the noble gases--helium, neon, argon, and so on--are all inert, meaning they resist forming molecules. The rows are trickier. Electrons orbit the nucleus in different regions called shells, which can fill up as seats do around a table. An atom likes to have a full shell. The chemistry of an element depends on how close its outermost shell is to full. If an atom has one electron too few or too many, it may just grab another electron (or give away its own) and become an ion. Some elements are common, others very rare. If you can name an element, it's probably common. Earth and other rocky planets are made of silicon, iron, carbon, nitrogen,phosphorous, and a host of less common elements. Earth's atmosphere consists mainly of nitrogen and oxygen. ON THE FRONTIER Elements heavier than fermium (100 protons) are generally unstable, lasting anywhere from days to hours to a few seconds or less. In 2006, a team from Lawrence Livermore National Laboratory in Berkeley synthesized superheavy element 118 by colliding isotopes of californium (98 protons) and calcium (20 protons). It decayed into lighter elements in .9 milliseconds. The periodic table proved its virtues yet again in 2007, when Swiss researchers reported that short-lived, superheavy element 112 ("ununbium") formed bonds with gold atoms in the same way as zinc and mercury, its column-mates on the table. COCKTAIL PARTY TIDBITS The most abundant elements in the universe are hydrogen and helium. You can actually buy most of the elements online, even some of the radioactive ones. There are people who collect elements as a hobby. The elements Earth is made of (including those in our bodies) were born about five billion years ago inside dying stars that exploded and spread their ashes into space. MOLECULES THE BASICS A molecule is a combination of elements bonded together into one unit. When two atoms don't have enough electrons individually to fill their outer orbitals, they can achieve fullness by pooling electrons, like pushing two tables together in a restaurant. A hydrogen atom has one electron but needs two to be full. If two hydrogen atoms share their two electrons, both are happy. The sharing of electrons is known as a covalent bond. Molecules made of two or more elements are called compounds. Some famous examples include water, which is made of two hydrogen atoms bonded to an oxygen atom (abbreviated H2O) and carbon dioxide (CO2) . Atoms of the same element can also form molecules, such as hydrogen (H2), oxygen (O2) , and ozone (O3). Those elements that are blessed with fullness (helium is one) don't like to make molecules of any kind. In other words, they're chemically inert. Molecules are never perfectly electrically neutral. Some atoms in a molecule may hog the shared electrons. An example is the oxygen atom in water. The electrons stick closer to oxygen than they do to the hydrogen atoms, which have smaller nuclei. So the oxygen has a partial negative charge, and the hydrogen atoms have partial positive charges. As a result, water molecules tend to stick together by lining up their positive and negative ends. ON THE FRONTIER Among the elements, one of the best sharers is carbon. It needs eight electrons in its outer shell but it only has four. So it likes to make four bonds, typically with other carbon atoms but also with hydrogen, oxygen, nitrogen, and other elements. There's a whole science of carbon sharing, called organic chemistry. Life on Earth is made of carbon molecules, also called organic molecules. We eat them, break them down, and build new ones to run our bodies. When searching for alien life, scientists think we should be looking for signs of carbon chemistry, or at least the possibility of it. COCKTAIL PARTY TIDBITS Not all compounds are molecules. When two ions are joined together, it's called an ionic compound or a salt. Table salt is made of positively charged sodium and negatively charged chlorine. Wall-climbing geckos have evolved to take advantage of a weaker kind of intermolecular bonding. Their feet are covered in millions of bristlelike setae, designed to maximize the Van der Waals interaction, which occurs when electrons on adjacent molecules twitch back and forth simultaneously. In one of Albert Einstein's most cited papers, he calculated the size of molecules by analyzing Brownian motion, the zigzag path of pollen and other tiny grains in liquid. CHEMICAL ENERGY THE BASICS It takes energy to break chemical bonds. But like relationships, some molecules are easier to break apart than others. Pump enough heat into any molecule and its atoms will split and go their separate ways. That's why Bunsen burners come in so handy in chemistry class. Freed from their molecular shackles, elements can reshuffle themselves to form new, more stable molecules. This process is called a chemical reaction. Chemical bonds are a source of energy. In an exothermic reaction, broken bonds release their energy as heat. This is what happens when you start a fire or run an engine. Heat from friction, a match, or a spark plug splits apart some hydrocarbon molecules, which release their energy as heat, which splits apart more molecules and so on. The same basic thing happens in our bodies. We eat hydrocarbon molecules (sugars and fats) and the body uses specially shaped molecules called enzymes to break them apart. The energy released by the broken bonds is channeled in complicated ways to do everything from moving our muscles, growing and repairing our cells, to powering our brains. (See the Instant Egghead Guide: The Mind for more on what happens in that thing.) ON THE FRONTIER We get most of our electrical power from burning fossil fuels. But there are other ways to extract chemical energy, such as the fuel cell, a device that generates a current by passing protons (aka hydrogen ions) through a membrane and fusing them with oxygen to make water. Not coincidentally, this is similar to how our bodies use oxygen. Our cells strip high-energy protons from hydrocarbon molecules, use them to make a kind of current to power the cells, and then combine them with oxygen to make water. Spent carbon molecules are exhaled as CO2. COCKTAIL PARTY TIDBITS In endothermic reactions, molecules suck heat from their surroundings and convert the energy into chemical bonds. That's how cold packs work. Exothermic reactions are useful for blowing things up. Breaking the bonds in molecules of tri-nitro-toluene (TNT) will release a lot of energy very quickly on their surroundings. The atoms in a molecule are constantly vibrating. Heat drives chemical reactions because it makes atoms vibrate more. STATES OF MATTER THE BASICS Here on Earth, every material--elemental or compound--comes in one of three states: solid, liquid, and gas. States of matter exist because molecules stick to one another via weak chemical bonds such as those between water molecules. Those links give them properties that they don't have as individual particles, such as hardness or wetness. The temperature at which a substance melts (or boils) depends on the strength of its chemical ties. Molecules in rock are fused together much tighter than those of water. Molecules are constantly jiggling, which we call heat or temperature (which are not quite the same thing, as we will see). In a solid, molecules aren't jiggling enough to overcome the links between them. They hold their shapes, like a bunch of LEGO bricks stuck together. Turn up the heat and the molecules will begin shaking so much they break free of their neighbors and start to mill around like when you poke around in a tray of loose LEGO bricks. The solid has become a liquid, which flows but doesn't change volume. In a gas, the bonds between molecules have broken entirely. They float around with no overall shape and their volume expands with temperature. A hot gas is less dense than a cold gas. That's why hot air rises. ON THE FRONTIER When a gas gets very hot--we're talking thousands or millions of degrees--heat vibrations shred some of the atoms apart into electrons and nuclei. This electrically charged cloud is called plasma. It's what the sun and stars are made of, which means it's the most common state of matter in the universe. Plasma-screen TVs work by generating a plasma that emits light. On a larger scale, scientists are working on creating powerful magnetic fields to control plasma to make nuclear fusion reactions. COCKTAIL PARTY TIDBITS A single air molecule at room temperature collides with other molecules more than a billion times per second. Microwave ovens work by generating electric fields that rapidly oscillate back and forth, causing atoms to vibrate. When helium is chilled to nearly - 459 degrees Fahrenheit, it loses all viscosity and becomes a superfluid, capable of climbing up the sides of a container like some kind of liquid alien life form. CONSERVATION OF ENERGY THE BASICS The word energy comes up a lot these days. But what is it? We know it comes in many forms. We eat food to give ourselves energy; we burn fossil fuels so electrical energy will come out of our wall outlets. To an egghead, the common denominator is that energy is the capacity to cause a change. It's a basic property of matter. One of the most fundamental observations researchers have ever made is that no matter how energy is transformed, the amount you end up with is always the same as the amount with which you started. This is called conservation of energy. The different forms of energy boil down to two basic types. Moving objects have kinetic energy, which they impart to whatever they bump into. When you walk, you add energy to the sidewalk by jostling the atoms beneath your feet. Sound energy is the kinetic energy of waves of molecules spreading outward like ripples in a pond. Even when an object is at rest,...