The Origins of the Universe for Dummies E-Book

Stephen Pincock

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2011

Seitenzahl: 513

Beschreibung

Do you want to learn about the physical origin of the Universe, but don't have the rest of eternity to read up on it? Do you want to know what scientists know about where you and your planet came from, but without the science blinding you? 'Course you do - and who better than For Dummies to tackle the biggest, strangest and most wonderful question there is! The Origins of the Universe For Dummies covers: * Early ideas about our universe * Modern cosmology * Big Bang theory * Dark matter and gravity * Galaxies and solar systems * Life on earth * Finding life elsewhere * The Universe's forecast

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The Origins of the Universe for Dummies

by Stephen Pincock and Mark Frary

The Origins of the Universe for Dummies®

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ISBN: 978-0-470-51606-5

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About the Authors

Stephen Pincock has been writing about science for the past 15 years, after finishing a degree in Microbiology at the University of New South Wales, Australia, and realising that while the whole science thing is utterly fascinating, he was less than eager to spend the rest of his life peering down a microscope.

Stephen’s currently a regular science contributor to TheFinancial Times and The Lancet among many other publications, and is the international correspondent for The Scientist. For quite a while he was an editor at Reuters Health.

Mark Frary is a science and technology writer. He studied astronomy and physics at University College London, writing a dissertation on the production of positronium. While there, he worked at the Mullard Space Science Laboratory on atmospheric plasma physics. After completing his degree, he moved to Geneva and worked on the OPAL experiment at the European particle physics laboratory CERN.

Mark co-wrote the book You Call This The Future?, a look at the 50 best science-fiction gadgets ever conceived and how they have become reality. He lives in Ampthill in Bedfordshire with his wife and two children.

Mark and Stephen are the authors of Codebreaker: The History of Secret Communication.

Dedication

We would like to dedicate this book to our long-suffering families: to Amanda, Daniel, Emily, Clare, Lola, and Seth with all our love.

Authors’ Acknowledgements

From Stephen: Throughout the writing of this book I’ve relied on the vital support of my lovely family, and I’d like to thank them all for their forbearance during those periods when, instead of being with them, I seemed to do little other than write.

I’m also very glad to have worked with the Wiley team on this project, including Rachael, whose encouragement was sometimes the only thing that got me through the work. Thanks also to the whole editing team, particularly Brian and his remarkable ability to carve lucid sentences from sometimes unpromising raw material!

Finally, thanks to Mark, whose talent and knowledge seemingly know no bounds.

From Mark: Thanks to my family and friends – in particular Clare, Margaret, Graham, mum, and dad – for giving me the time to write this book and for not minding too much about the late evenings and weekends working which should have been spent with them. Thanks also to my co-author Stephen Pincock, who has provided unstinting support and given me a huge number of welcome suggestions that have improved the book considerably.

I’m grateful to Jason Dunne, Rachael Chilvers, and the rest of the team at Wiley for giving this project the green light and for their encouragement and suggestions throughout the publishing process.

A big thanks also to Dr Carolin Crawford for her input on the technical aspects of this book.

Publisher’s Acknowledgements

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Contents

Title

Introduction

About This Book

Conventions Used in This Book

What You’re Not to Read

Foolish Assumptions

How This Book Is Organised

Icons Used in This Book

Where to Go from Here

Part I : In the Beginning: Early Ideas About Our Universe

Chapter 1: Exploring the Early Universe

Shifting Views – Scientifically Speaking

Contrasting Science and Religion

Defining Cosmology

Realising Why Now Is So Exciting

Chapter 2: Looking Up at the Stars: Early Beliefs

Making a Home for the Gods: Early Notions

Taking a Scientific Approach: Early Views

Moving the Sun to the Centre: The Copernican Revolution

Chapter 3: The Apple Drops: Newton, Gravity, and the Rotation of the Planets

Tycho Brahe, a Rising Star

Assisting – and Surpassing – Brahe: Johannes Kepler

The Universe Reveals Itself: Galileo

Watching Apples Fall: Isaac Newton

Part II : Modern Cosmology: Going Off with a Bang

Chapter 4: Bending the Universe: Magnets and Gravity

Confirming Newton’s Laws

Tripping the Light Electromagnetic: James Clerk Maxwell

Getting Rid of the Ether: Michelson and Morley

Getting Relative with Albert Einstein

Chapter 5: Measuring the Universe

Examining All Those Twinkling Little Stars

Classifying the Stars

Measuring Stellar Distances

Contemplating an Ever-Expanding Universe

Chapter 6: Cooking Up a Big Bang

Gathering the Ingredients for an Expanding Universe

Turning Up the Heat on Expansion

Checking the Oven: Looking for Fossil Radiation

Chapter 7: Letting It Rise: Expanding and Inflating the Universe

Going Back to the Beginning

Pondering the Horizon

Shaping the Universe

Imagining Inflation

Chapter 8: Thinking Differently About the Universe

Existing Forever: An Alternative to the Big Bang

Explaining the Universe in Other Ways

Part III : Building Your Own Universe

Chapter 9: Building Things from Scratch

What’s the Matter? Searching for the Most Basic Building Block

Venturing Beyond Electrons, Protons, and Neutrons: Quantum Mechanics

Probing the Concept of Probability

Antimatter

Getting to Know the Standard Model

Chapter 10: Forcing the Pace: The Roles of Natural Forces in the Universe

Forcing the Issue

Uniting the Forces of Nature

Giving Things Mass: The Higgs Field and Boson

Searching for GUTs and TOEs: Grand Unified Theories and Theories of Everything

Chapter 11: Shedding Light on Dark Matter and Pinging Strings

Addressing the Dark Elephant in the Room: Dark Matter

Getting Even Darker: Dark Energy

Stringing the Universe Along

Chapter 12: Playing with the Universe’s Chemistry Set

Strolling Through the Periodic Table

Making Helium and Hydrogen in the Big Bang

A Star Is Born

Classifying Stars by Their Chemistry

Creating Heavy Metals with Supernovae

Chapter 13: Making Stars, Solar Systems, Galaxies, and More

Making Stars

Forming Solar Systems

Creating Galaxies

Accounting for Everything in the Universe

Getting the Really Big Picture: Beyond the Milky Way

Chapter 14: Giving Birth to Life

Defining Life

Tracking the Very Beginnings of Life

Enjoying a Warm Bowl of Primordial Soup

Living in a Universe That’s ‘Just Right’

Chapter 15: Travelling Through Time

Exploring Past, Present, and Future

Turning Back Time

Venturing Back to before the Big Bang

Part IV : Asking the Tough Questions

Chapter 16: Explaining the Unexplainable

Watching Stars Die

Being Aware of Black Holes

Knowing Neutron Stars

Meeting Quasars, the Fascinating Hearts of Galaxies

Creating Parallel Universes

Chapter 17: Finding Life Elsewhere

Searching for Life in Our Solar System

Finding Planets with Life Outside Our Solar System

Finding Intelligent Life Elsewhere

Chapter 18: Coming to an End

Watching the Sun Burn Out

Contemplating the Fate of the Universe

Considering an Alternative Ending: The Big Rip

Part V The Part of Tens :

Chapter 19: Ten Different Beliefs about the Origins of the Universe

Judeo-Christian Creation: In the Beginning

Islamic Creation: Opening the Heavens and Earth

Hindu Creation: Cycles upon Cycles

Buddhist Creation: Cause and Effect without a Creator

Shinto Creation: The Earth, Young and Oily

African Folklore: Egg-centric Origins

Iroquois Creation: The Turtle Time Story

Adams: Life, the Universe, and Everything

Pratchett: Absurdity and Another Giant Turtle

In the World Before Monkey

Chapter 20: Ten Greatest Cosmological Advances

Cosmic Background Explorer (COBE)

European Particle Physics Laboratory (CERN)

Hubble Space Telescope

Super-Kamiokande

Wilkinson Microwave Anisotropy Probe (WMAP)

Chandra X-ray Observatory

Fermilab

Atacama Cosmology Telescope (ACT)

Mount Wilson Observatory

Keck Telescopes

Appendix: Understanding Scientific Units and Equations

Powers

Other Mathematical Conventions

Scientific Units

Non-SI Units

Key Equations

: Further Reading

Part I

In the Beginning: Early Ideas About Our Universe

In this part . . .

Before the advent of television, humans had plenty of opportunity to look up at the stars. With so much time on their hands to observe the heavens, it’s hardly surprising that early humans came up with some pretty elaborate explanations for why the night sky looks as it does. In this part, we explain some of the most popular ideas from the pre-scientific era.

Eventually, the Ancient Greeks put the study of the universe onto a scientific footing for the first time, believing they’d discovered the perfect answer for the workings of the universe, based on geometric shapes and a universe centred on the earth.

Much later, scientists eventually realised that the Greeks’ idea of the perfect heavens was somehow flawed. We show how the realisation by Johannes Kepler that planets moved in orbits that aren’t circles led to one of the most earth-shattering ideas of all time – gravity. With gravity, the modern science of cosmology was born.

Chapter 2

Looking Up at the Stars: Early Beliefs

In This Chapter

Seeing the universe through ancient eyes

Adopting a scientific approach with the Greeks

Starting a revolution with Copernicus

In this chapter we take you on a quick side-trip through time. We know that you bought this book to read about the origin of the universe as modern science understands it, and don’t worry, that’s still the destination. But getting a little perspective is always useful.

For most of history, humans have contemplated the origins of the universe, coming up with conclusions that are very different to modern, science-based explanations. Considering that humans have been able to study sub-atomic particles, measure radiation, or send satellites into space only in the last century or so, earlier thinkers had no option but to base their ideas on what they saw in the sky above them. As a result, for thousands of years, people put the Earth at the centre of things. Only when Copernicus arrived on the scene in the 15th century was this Earth-centric idea seriously challenged. Copernicus’s revolution paved the way for the modern era of cosmology, which we cover in Part II of this book.

This chapter ventures back to some of the earliest known human beliefs about the origins and workings of the universe and charts the gradual development of these beliefs. Read on; it’s an entertaining ride.

Making a Home for the Gods: Early Notions

Gazing up at the stars on a clear night and not feeling a sense of awe is almost impossible to do. And so, unsurprisingly, civilisations throughout history have told tales to explain the way the universe was made.

In a lot of cases, people bundled their explanations with a host of weird and wonderful creation stories. In some of these tales, the Sun and Moon are gods moving through the skies, whereas other tales suggest that the night represents the underworld. The following sections explore two fascinating visions of the universe – those of the ancient Babylonians and the Egyptians, civilizations that may predate by centuries the writing of the creation stories in the Bible.

Whatever the specifics of these stories, the general view was that the Earth lay at the heart of the universe and anything that shifted in the sky moved relative to the humans below, here on the ground.

Splitting a god’s carcass in two: The Babylonian creation story

One particularly gory example of a creation myth arose among the ancient Babylonian people, who lived on the plain between the Tigris and Euphrates rivers in an area occupied by modern Iraq, parts of Syria, Turkey, and Iran from roughly 2000 BC to 500 BC.

According to the Babylonian creation myth, known as Enuma Elish, the Earth was created after a fight between two gods – Tiamat, the monstrous embodiment of chaos, and the younger Marduk. In the battle, ferocious Tiamat opened her mouth to swallow her opponent, but Marduk seized the chance to fill her with hurricane winds. The winds filled Tiamat, leaving her vulnerable to Marduk’s arrows and lances.

The story goes on to explain that Marduk – stopping only long enough to sever Tiamat’s limbs, smash her skull, and slice her arteries – split Tiamat’s body ‘like a cockle-shell’ and used the top half to construct the arc of the sky and the bottom half to make the Earth.

After his bloody victory, Marduk then found conspicuous places for all the great gods in the sky, giving them starry aspects as constellations. Furthermore, Marduk opened Tiamat’s ribs to serve as gates in the east and west for the Sun to rise and set and to provide the Moon with a jewel-like lustre. The text, written around the 12th century BC, quotes Marduk’s instructions to the new moon (the point every 29 or 30 days when we only see the unilluminated side of the Moon, because it lies between the Earth and the Sun and its far side is lit). Here’s one translation: ‘When you rise on the world, six days your horns are crescent, until half-circle on the seventh, waxing still phase follows phase, you will divide the month from full to full.’ This is an accurate representation of how the phases of the Moon progress.

Gory fantasies aside, mind you, the Babylonians had a well developed mathematical system and were keen star watchers. They catalogued the movements of the stars and planets and recorded eclipses, mainly for the purposes of astrological prophesying. Their observations and predictions were surprisingly accurate given that they had little in the way of scientific instruments with which to make their recordings.

Making love among the stars: Egyptian gods in the sky

The ancient Egyptians (roughly 3100 BC to 30BC) had a complicated set of mythologies, but one of their best known myths is a creation story that starts with the primeval waters of the god Nun. (If you want to know more about the Egyptians’ mythology and scientific contributions, check out TheAncient Egyptians For Dummies by Charlotte Booth, published by Wiley.)

The story goes that from these waters, a mound appeared upon which sat the god Atum. Atum spat to produce the gods of air, called Shu, and moisture, called Tefnut. They in turn gave birth to the god and goddess of earth (Geb) and sky (Nut).

Geb and Nut were apparently bound at first in an eternal embrace, but Shu separated them, leaving Geb frozen in eternal torment, while Nut was lifted into her place in the sky. Shu positioned himself as the air separating them. Each day, the heavenly bodies entered Nut’s mouth, moved through her skies, and at dawn were reborn from her womb.

According to one version of the tale, Shu ruled that the pregnant Nut should not give birth any day of the year. The desperate Nut then pleaded to the god Thoth for help. Thoth gambled on her behalf with the moon-god Yah and won five more days to be added onto the year, which had up until then been 360 days long. Nut gave birth to one child on each of these days: Osiris, Isis, Set, Nephthys, and Horus-the-Elder. These extra days proved rather useful. Previously, with a 360-day year, priests had to declare an additional month every few years to get the year and seasons (as dictated by the movement of the Sun) back into step.

According to lore, Thoth taught the ancient Egyptians how to watch the heavens and gave them the names of 36 constellations. Careful monitoring of the sky was important stuff for the practically minded Egyptians who needed a regular calendar to help them get ready for the flooding of the Nile.

Taking a Scientific Approach: Early Views

Many ancient civilisations, like the Babylonians and Egyptians, took religious or spiritual views about their place in creation. The ancient Greeks, however, were the first to hold a distinctly different perspective on the universe.

The Greeks thought of the heavens as something that mere mortals could understand, rather than as belonging strictly to the realm of gods. In short, the Greeks took a scientific approach, laying the foundations upon which scientists continue to build much of today’s understanding of the universe.

Of course, the early Greeks had their gods too. One version of the Greek creation story, for example, involved Eros, the god of love, creating order out of chaos from which night and day, and eventually the Earth itself, arose. These gods were said to reside at the top of Mount Olympus, ruling the world at their whim.

But over the centuries, Greek thinkers began to realise that the stars in the night sky offered patterns that were stable enough to use to navigate ships. This realisation gradually opened their eyes to the fact that physical laws, not the random decisions of deities, governed the stars.

The following sections contain details of some of the ancient Greeks’ great physical discoveries and realisations.

Envisioning the harmony of the spheres: Pythagoras

At school you had to know Pythagoras’s theorem, which lets you calculate the lengths of the sides of a triangle, but Pythagoras and his followers were fascinated by many other topics involving numbers as well. This group, which lived in a kind of religious brotherhood beginning in the sixth century BC, felt sure that the universe was deeply mathematical in nature.

Pythagoras thought the shape of the universe was based on the sphere, the most perfect geometric object according to the Greeks because it could be defined by a single parameter, its radius. He considered the Earth to be at the centre of that sphere, around which the Moon, Sun, and planets moved on their own concentric wheels. He also thought that the speeds at which those heavenly bodies moved created perfect harmony.

A follower of Pythagoras, Philolaus, later came up with one of the first recorded concepts of the universe that didn’t put the Earth at its centre. Philolaus’s scheme had the Earth as a perfectly spherical object, which orbited in a circle around an invisible fire along with another nine heavenly bodies (see Figure 2-1). Still, most ancient Greeks continued to believe that the Earth was at the centre of things.

Figure 2-1: Philolaus’s view of the universe.

Pushing the limits: Anaxagoras of Clazomenae

Challenging the established thinking can be dangerous, as a fellow called Anaxagoras of Clazomenae found in around 450 BC when he offered new ideas on the origins and organisation of the cosmos.

Anaxagoras challenged the religious teachings of his day, specifically by saying that the Sun was a red-hot stone (instead of a god) and that the Moon reflected the Sun’s light. These two assertions, although spectacularly insightful, landed Anaxagoras in prison; but incarceration didn’t stop his radical thinking. He also thought that

The universe began with a swirling vortex, which started by separating the hot ‘ether’ (the fiery bits) from the cool air, giving rise to water, clouds, earth, and stones.

The circular motion of the universe made heavy, dense material congregate in the centre to form the Earth, while the violence of the spinning caused the fiery ether to tear stones away and kindle them into stars.

Anaxagoras is also remembered for coming up with the first accurate explanation for eclipses of the Sun and Moon, based on his spot-on thoughts about the Moon reflecting the Sun’s light.

Following a wandering star: Aristarchus of Samos

By the third century BC, another Greek philosopher called Aristarchus of Samos came up with a more accurate description of the way the universe works. Aristarchus based his thinking on the fact that Greek astronomers had noticed that two types of star existed:

Fixed stars, whose position in the sky relative to each other stayed constant.

Wandering stars, which moved around. (We get the word planet from the Greek word for wanderer, plan√t√s)

Aristarchus came up with a clever argument for explaining the two star types. First, he used geometry to make an estimate of the size of the Sun, coming to the conclusion that it must be enormously bigger than the Earth. Then he argued that no way existed for something so enormous to trail around circling the much smaller Earth.

Aristarchus proposed that the Earth must orbit the Sun. And what’s more, he deduced that the Earth itself must be spinning on its axis, in order to explain the apparent movement of the stars.

Now these insights were superb stuff. Aristarchus had nailed many of the key ingredients of the so called heliocentric, or Sun-centred, system that Copernicus (see the later section ‘Moving the Sun to the Centre: The Copernican Revolution’) made famous many centuries later.

Winning the day: Aristotle

Sadly, Aristarchus’s revelations were dismissed out of hand because they contradicted the views of Aristotle, who had raised a couple of pertinent questions when considering whether the Earth moved:

If the Earth is rotating, why do objects thrown upwards fall in the same place?

Why doesn’t the Earth’s rotation create really strong winds?

Aristarchus had hit upon a good description of our solar system, but his system was not widely accepted. Instead, Aristotle’s views prevailed.

Aristotle’s description of the way the universe works was laid out in his book On the Heavens. He argued that nine transparent concentric spheres encircle the Earth. The outermost sphere was the heavens, whose stars appeared in the same relative positions night after night (apart from rotating around the Earth, of course), whereas the rest contained the Moon, the Sun, and the five planets known at the time (Mercury, Venus, Mars, Jupiter, and Saturn).

Furthermore, Aristotle thought that the universe was not infinite in size because it moves in a circle; if the universe were infinite, it would be moving an infinite distance in a finite time, which is impossible. On the other hand, Aristotle said that the universe was eternal – in that it always has, and always will, exist.

Aristotle’s views dominated Western thought until the 16th century, even though his idea of perfectly circular motions didn’t really stand up to scrutiny. As the Greek empire expanded to the east, astronomical data collected by the Babylonians and Egyptians (who were both under Greek imperial rule at different times) became available to the Greeks. These records clearly indicated that the planets didn’t move in circles around the Earth at all.

Refining Aristotle’s system: Ptolemy

For centuries – more than a millennium, in fact – no one proposed any real challenges to Aristotle’s model for the universe.

But in the second century AD, a Greek astronomer called Claudius Ptolemy, who was born in Egypt and had Roman citizenship, added some refinements that made the Aristotelian scheme do a much better job of matching the movements of the planets across the skies.

Ptolemy’s first clever move was to move the Earth just slightly away from the centre of the cosmic spheres. This shift helped explain why the planets seemed sometimes to move closer to the Earth or farther away.

Another of Ptolemy’s achievements was to explain the odd movements of some planets, such as Mars, which seem to backtrack on themselves as they move across the sky – something referred to as retrograde motion. This backtracking in fact happens because the Earth orbits around the Sun more quickly than planets farther away, but Ptolemy had to figure out an explanation that had the Earth standing still.

His idea was that each planet moved around in a series of small circles, each of which in turn spun on larger spheres. At least one writer has likened this arrangement to a kind of Ferris wheel where capsules spin around on the big wheel. These systems of smaller circles were called epicycles. To explain the motion of the planets, Ptolemy added a complex set of supplementary orbits to the movement of some planets.

Although Ptolemy’s system was actually pretty good at explaining and predicting the movement of heavenly bodies, it wasn’t accurate. Of course, Ptolemy’s aim wasn’t really to describe the physical reality of the universe, only to find a way to chart the movements of the planets, Sun, and Moon. For more on Ptolemy’s work, see the sidebar on page 25.

Moving the Sun to the Centre: The Copernican Revolution

Polish church canon Nicolaus Copernicus kicked off a revolution in cosmology when he presented a model of the world in which the Sun was central, not the Earth (see Figure 2-2). Although Aristarchus had done something similar many centuries before (refer to the earlier section ‘Following a wandering star: Aristarchus of Samos’ for more information), Copernicus’s model was the one that eventually led to a change in the way humans view the universe.

Figure 2-2: Copernicus’s Sun-centred universe.

Copernicus first set out his plan on a short handwritten note known as the ‘Little Commentary’, or ‘Commentariolus’, which he circulated among friends and colleagues between 1508 and 1514. He wrote that if the Sun is assumed to be at rest and the planets are orbiting it, you can calculate the planets’ relative distances from the Sun based on the length of time it takes them to cross the sky. The circular orbit of the Earth around the Sun also explained the fact that the planets appear to change in size and helped make sense of the retrograde motion of some planets.

The ‘Commentariolus’ contained seven assumptions or axioms that underpinned Copernicus’s ideas:

The heavenly bodies don’t all move round the same centre. A key piece of evidence would be if anyone observed a Moon around another planet, as Galileo later did around Jupiter.

The Earth isn’t the centre of the universe, only of the Moon’s orbit and of terrestrial gravity. Heretic stuff, of course, but it would dramatically simplify the maths of orbits.

The Sun is the centre of the planetary system and therefore of the universe. This laid the foundations for the scientific understanding of planetary motion (that is, gravity).

Compared to the distance between the Earth and the fixed stars, the distance from the Earth to the Sun is negligibly small. Finally, someone had realised that the universe was immense.

The apparent daily revolution of fixed constellations (as opposed to those pesky wandering planets) is due to the Earth’s rotation on its own axis, the imaginary line joining the north and south poles. This was a revolutionary, counter-intuitive idea, but very, very clever.

The apparent annual motion of the Sun is due to the fact that the Earth, like other planets, revolves around the Sun.

The apparent ‘stations’ and retrograde motion of the planets are due to the Earth and planets revolving around the Sun.

The final version of Copernicus’s theories didn’t appear for another 30 years or so, when, in the year of his death, 1543, he published his treatise De Revolutionibus Orbium Coelestium Libri VI (Six Books Concerning the Revolution of Celestial Spheres).