Instant Egghead Guide: The Universe: The Universe

Instant Egghead Guide: The Universe: The Universe

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Everything from quarks to galactic superclusters delivered to your eyeballs at the speed of light (any faster would be impossible)

Take a tour of the wonder and majesty of the universe, from the smallest subatomic particles to the possibility of infinite universes. According to some prominent physicists, it's possible that, right now, someone who looks just like you is reading the back of a book just like this one in a parallel universe. And your double thinks it looks really interesting...

Whether you're a fan of Scientific American's wildly popular 60-Second Science Podcast or just curious about science, you're going to want to dust off your Dad's telescope and warm up your particle accelerator after enjoying the same bite-sized knoweldge in The Instant Egghead Guide to the Universe.

Product Details

ISBN-13: 9780312386375
Publisher: St. Martin's Press
Publication date: 07/21/2009
Series: Instant Egghead Guides Series
Edition description: First Edition
Pages: 240
Product dimensions: 5.06(w) x 7.10(h) x 0.63(d)

About the Author

JR MINKEL is a staff editor at Scientific American.

George Musser is the astronomy editor at Scientific American magazine and author of The Complete Idiot's Guide to String Theory.

Read an Excerpt

Instant Egghead Guide: The Universe





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.


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.


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.)



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.


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.


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.



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.


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.


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.



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.


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.


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.



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.)


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.


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.



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.


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.


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.



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, it has the potential to cause a change. We say it has potential energy, which is the other basic type of energy. It comes from gravity and other forces. A glass of water in your hand has the potential to fall. It has gravitational potential energy. Chemical bonds store chemical energy.


Essentially all the energy on Earth comes from the sun. Light from the sun heats the ground, the atmosphere, and our bare arms. Plants capture solar energy and turn it into hydrocarbons, which we eat or feed to animals so we can eat them. Fossil fuels are just ancient plants and animals squished to goo in Earth's crust.

We can tap the sun's energy directly using solar cells, materials that absorb light and turn it into electricity. In principle, they are a cleaner source of energy than oil and other fossil fuels, which produce the greenhouse gas carbon dioxide when we burn them. Other ways of tapping nonfossil fuel energy include windmills, waterfalls, and even heat from inside Earth.


The conversion of one type of energy to another can take many forms. Researchers have discovered that blasting liquids with ultrasound can generate bubbles that collapse so forcefully, they produce temperatures of millions of degrees.

German surgeon Julius Robert von Mayer codiscovered the conservation of energy in 1842, after observing that his patients in the Dutch East Indies had redder blood than his usual patients, indicating they needed less oxygen to maintain their temperature.



A very common form of energy is heat. We mentioned that heat and temperature are not the same thing. Temperature is the average amount of jiggling in a group of molecules. The water molecules in a mug of hot coffee are jiggling more violently than those in a glass of cold milk. Heat is temperature in motion. When you mix cold milk with hot coffee, the coffee molecules knock around the milk molecules until they are all jiggling by the same amount.

Heat can do work. As gas molecules vibrate, they bump into whatever's around them. Heating a gas makes the vibrations more violent, and the gas will expand if it's in a container that will let it. If not, its pressure rises, meaning the gas molecules knock into the container more frequently and violently. A car's engine works by burning air mixed with gasoline, which pushes a piston that ultimately turns the wheels.

No matter how carefully you operate a machine, you can never avoid wasting some energy as heat. It doesn't matter if the machine in question is a human-built device such as a car or a computer, an evolved organism such as a bacterium, or a denizen of the universe such as a star. Without a fresh infusion of energy now and then, it will eventually wind down and stop running. This idea is called the second law of thermodynamics.


The light emitted from an object can tell you its temperature. Jiggling molecules emit infrared light, which our bodies sense as warmth. When the temperature of an object rises past a certain point, it emits visible light. Think of a glowing coal. The color of a heated object (the frequency of light it emits most intensely) depends only on its temperature. This is called blackbody radiation, and it's how we infer the temperature of the sun and other stars. Stars cool very slowly—over millions to trillions of years—because there's not much matter around them to be heated.


Early chemists thought heat was a hypothetical fluid, which they called caloric or phlogiston.

A rubber band makes for a snappy lesson in thermodynamics. When you stretch it, it heats up. (Try touching it to your lips.) You've converted mechanical energy to heat.

The temperature of space comes from a faint glow of microwaves called the cosmic microwave background. If you put a thermometer in space, it would come to read 2.7 kelvins, or nearly -459 degrees Fahrenheit.



An implication of the second law of thermodynamics is that a system starved of fresh energy tends to become more "disordered" or mixed together over time. Entropy is a measure of how much mixing has taken place.

According to the second law, entropy can only increase or stay the same, never decrease, for any system that's isolated from its environment, be it the coffee in a thermos or a star in outer space. Differences in temperature "want" to smooth themselves out. Entropy tends to increase.

In the world of molecules, entropy is related to the number of different ways the same molecules can be mixed together. It's like having a messy room. There are many different ways for a room to be messy. The clothes can be hanging off the chair or on the floor; candy wrappers can be on the table or under the bed. But there are many fewer ways to have a clean room. The clothes have to be folded and hung up. The wrappers go in the wastebasket.

But as soon as you stop doing work, things start to get messy again. It's the same with molecules. Leave a bottle of perfume open, and perfume molecules will tend to jiggle themselves into the air. It's extremely unlikely they would all randomly jiggle back into the bottle.


Entropy is related to the passage of time. The laws of physics don't seem to differentiate between going forward in time or going back. The only thing keeping vibrating perfume molecules from going back into the bottle is statistics. It's just way, way too unlikely. If we saw it happen, we'd say time was running in reverse. Scientists believe we experience the passage of time because the universe is gradually getting more disordered.


German physicist Ludwig Boltzmann came up with a formula that relates entropy to the different possible configurations of a group of molecules. He had it engraved on his tombstone.

We said life doesn't violate the second law. Living things are definitely highly ordered, but they derive their order by creating more disorder around them than they contain within.



The nucleus is small, even by atomic standards. If a hydrogen nucleus were the size of a marble (about a centimeter across), its electron would lie 100 yards away. What could possibly be going on in a space that small, you might wonder. Just you wait. The nucleus is really the coolest part of the atom. Seemingly stable, it can shoot out pieces of itself, fuse with other nuclei, and even explode into showers of other particles.

Maybe you were wondering why the nucleus exists at all. If like charges repel, shouldn't the mutual electric repulsion of all those positively charged protons blow the nucleus apart? It turns out there's an even stronger force that counters the electric repulsion. It's called the strong force, and it makes protons and neutrons stick together like refrigerator magnets.

Protons packed too tightly? Just add neutrons and voilà: instant glue. Up to a point, anyway. If a nucleus has more than 83 protons, no amount of neutron glue can bind it together forever. It will eventually break down in a process called radioactive decay. A second nuclear force—the weak force—is responsible for one kind of radioactivity.


We mentioned that the nucleus could melt. At the Relativistic Heavy Ion Collider (RHIC) in Long Island, New York, researchers smashed gold nuclei together at 99.99 percent light speed. When the nuclei struck one another, they melted into a cloud of quarks, particles inside protons and neutrons—and gluons, another kind of particle that "glues" quarks together, naturally enough. The mixture is called the quark-gluon plasma, and it's the hottest, densest matter scientists have ever made. Researchers believe the universe was full of quark-gluon plasma a few microseconds after the Big Bang.


Incoming! English physicist Ernest Rutherford discovered the nucleus in 1909 by firing so-called alpha particles at gold foil. Light and positively charged, the alpha particles seemed to be striking small, positively charged nuggets; Rutherford likened it to cannon shells bouncing off tissue paper.

The nucleus may also come in shells like electrons in an atom. Superheavy elements are thought to be stable because they have "magic" numbers of protons and neutrons that fill up their nuclear shells.

The quark-gluon plasma has a temperature of trillions of degrees and a pressure of 1030 Earth atmospheres.



Radioactivity is a process that transforms one element into another. It occurs because the nucleus is under a lot of strain from the repulsion between protons and needs to relieve the pressure somehow. Elements heavier than bismuth (number 83 on the periodic table) are always radioactive, but all elements have radioactive isotopes.

When a radioactive isotope decays, it can gain or lose protons in one of two ways. In alpha decay, a helium nucleus (known as an alpha particle) quite literally burrows its way out of the nucleus, in a process called quantum tunneling. The alpha decay of uranium (element 92) yields thorium (element 90), for example. Beta decay is a little weirder. In it, a neutron morphs into a proton (via the weak force mentioned earlier) and emits an electron, called a beta particle. Two beta decays turn thorium back into a lighter isotope of uranium.

The intrinsically radioactive elements do a kind of alpha-beta shuffle—losing protons and then gaining them back—until they become lead, which has a stable nucleus. But it doesn't happen overnight. Radioactive samples decay at a rate called the element's half-life, the time it takes for half the atoms in a sample to break down. (The individual atoms decay at random.) The half-life of uranium is 4.5 billion years, which is about the age of Earth.


Alpha and beta particles are hazardous because they can plow into our bodies and strip electrons from important molecules, potentially killing cells or causing mutations that might lead to cancer. Former Russian secret service agent Alexander Litvinenko was poisoned in 2006 in Great Britain using polonium-210, an alpha-emitting radioactive isotope with a half-life of 138 days. Little did his poisoners know that tests were sensitive enough to pick up traces of the isotope.


Radioactive isotopes are hot, literally. A gram of polonium can produce enough alpha particles to heat itself to more than 900 degrees Fahrenheit. New Horizons, a NASA probe on a mission to Pluto, is powered by 24 pounds of plutonium-238 oxide.

Neutrons are unstable outside of the nucleus. Left to themselves, they would decay (a fancy word for transform) into protons in about 15 minutes on average.

Alpha and beta particles were named for their ability to penetrate matter. (Scientists didn't know their true identities.) A sheet of paper will block alpha particles but it takes an aluminum plate to halt beta particles.



When nuclei are crushed together and heated to millions of degrees they can fuse together to form heavier nuclei in a process called (duh) nuclear fusion. In the process, they liberate a tremendous amount of energy. The sun and other stars get their energy by fusing hydrogen into helium. Without fusion, the sun would not shine the way it does.

In the simplest fusion reaction, hydrogen nuclei fuse to form helium. As with a campfire, the reaction requires heat to get started. Protons resist coming together because of their electric repulsion. But when heated above 10 million degrees, they begin to rattle so violently that they touch, and once that happens, the nuclear forces kick in, turning protons into neutrons and linking them together into a helium nucleus.

In stars, it takes four protons to make helium through a series of reactions called the proton-proton cycle. The process is self-sustaining because it gives off a lot of energy. Where does the energy come from? A helium nucleus is 0.7 percent lighter than the sum of the masses of two protons and two neutrons. That missing mass has to go somewhere, and according to Einstein's equation E = mc2, mass is equivalent to energy. The excess mass is converted to energy.


Researchers would like to harness fusion to make electricity. Cooking matter to the temperatures required for fusion turns it to plasma, a hot gas of electrons and nuclei, which is dangerous and hard to contain. Gravity solves that problem in a star, but here on Earth we have to be more creative. Now an international team has finally begun work on a prototype fusion reactor called ITER, the International Thermonuclear Experimental Reactor, in southern France. In the works for more than 20 years, the $15 billion project is designed to generate a powerful doughnut-shaped magnetic field, called a tokamak, to heat and contain the plasma for sustained fusion reactions.


Remember the Moby song about people being made of stars? It's true. Fusion in stars is the source of all the elements heavier than lithium (number three on the periodic table, after helium).

All the elements up through iron were made in the final week of a star's life. The elements from cobalt through uranium were made in the last moment before a star exploded in a supernova.

INSTANT EGGHEAD GUIDE: THE UNIVERSE. Copyright © 2009 by Scientific American. All rights reserved. For information, address St. Martin's Press, 175 Fifth Avenue, New York, N.Y. 10010.

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