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466 Chapter 15

The History of theUniverse

C H A P T E R

15Getting Started

15C H A P T E R

1 This is the Cat’s Eyes Nebula. Using technology thatallows them to see events that happened billions ofyears ago, scientists have collected evidence thatnebulas are one of the stages in the lives of stars. What is this amazing technology? Are the stars we see at different stages of their existence? What do weknow about the “birth” of stars? Are stars still beingformed? Do stars die?

2 The nebula shownhere, called theLagoon Nebula, is anursery for new stars.Scientists haveproposed thatplanets sometimesform at the sametime as stars, so oursolar system isprobably not the onlyplanetary system inthe universe. What istheir evidence? Whyis it so difficult toprove that there areplanets travellingaround other stars?How old is the solarsystem? How did theplanets form? Willthey last forever?

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3 Canadian astronomers join other astronomers in the searchfor answers to questions about the universe. Did the universehave a beginning? If so, when was it? What evidence do wehave that supports theories of the origin, growth,and future of the universe? If astronomers areunable to find direct evidence to supporttheir hypotheses, how could they useindirect evidence?

The History of the Universe 467

Using Indirect Evidence

Many scientists, from space scientists tochemists, are sometimes unable to makedirect measurements or collect directevidence for their investigations. Insteadthey use many kinds of indirect evidence.You have already used an indirect methodto measure distances that you could notmeasure directly. Now you can discoverfeatures of something you can’t see bygathering indirect evidence.

1. At a station set up by your teacher, a flat,horizontal board hides something from

your direct view. Observe carefully asone student at a time rolls a small steelball along the surface of the board.

2. Continue observing until you aresatisfied that you can describe what ishidden.

3. Draw a diagram of what you think ishidden beneath the board.

4. What is “indirect evidence”?

ReflectingThink about the questions in

, , . What ideas do you already

have? What other questions do you

have about the history of the universe?

Think about your answers and

questions as you read the chapter.

1 2 3

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468 Chapter 15

We say that stars have a “life” because theyevolve from clouds of gas and dust and followa predictable series of stages: they begin (are“born”), develop, and end (“die”). Each lifemay take billions of years or more, a length oftime that is difficult for humans to imagine.

Using modern instruments and looking atstars billions of light-years away, astronomershave been able to examine millions of stars atdifferent stages in their lives. Scientists haveput together many pieces of information, likethe pieces of a puzzle, to develop a theory ofthe life of a star.

One of the first pieces of informationcame in 1678 with Isaac Newton’s discovery ofgravity. We now know that gravity is a forcethat pulls objects toward each other. Themore mass an object has, the more gravity itexerts, so the Sun has stronger gravity thanEarth. But the force gets smaller as thedistance between objects increases.

All stars begin their lives in nebulas, whichare huge clouds of dust and gases, mainlyhydrogen and helium (Figure 1). The dustand gases swirl around, breaking into clumpsand contracting because of gravitationalforces. As the clumps bump into each otherand get bigger, their gravity gets stronger, andthey are able to attract more particles andpack more tightly together. Eventually, theclumps are dense and hot enough for nuclearfusion to start. They have become new stars.

Just as no two clouds on Earth areidentical, no two stars are identical. Althoughscientists understand the stages of stars fairlywell (Figure 2), our knowledge of the detailsis far from complete. That is part of theexcitement of studying astronomy. All theseideas are theories that are undergoingconfirmation, development, or change basedon further observations and evidence.

The Life of a Star

15.115.1

Graphing Gravity

What factors affect the force of gravitybetween two objects? Make a prediction.The equation for two objects interacting isF = (Gm1m2)/d2, where F is the force innewtons (N), G is a constant (6.67 × 10–11

Nm2/kg2), m1 is the mass of object 1, m2 isthe mass of object 2, and d is the distancebetween the centres of the objects.

1. Find the masses and radii of theplanets in our solar system andcalculate the force of gravity on a 1.0-kg rock at the surface of each one.

2. Determine the force of gravity on therock when its distance from the centreof Earth is 2, 4, 6, and 8 Earth radii.Plot a graph to show your discoveries.

3. How accurate was your prediction?

Figure 1

The Trifid Nebula has two separate regions. The pink regionhas a high concentration of hydrogen, and the bluish-violetregion is reflecting light from nearby stars. The dark patchesare caused by dust clouds located between the nebula andEarth.


Figure 2

Type of Star

Birth

Early Life

Major Partof Life

Old Age

Death

Remains

Small or Medium Star (mass thesame as the Sun’s or less; the mostcommon type of star)

Large Star (mass about 10 timesthe mass of the Sun; rare)

Extremely Large Star (mass about30 times the mass of the Sun; veryrare)

Forms from a small- or medium-sized nebula.

Forms from a large nebula. Forms from an extremely largenebula.

Gradually turns into a hot, denseclump that begins producing energy.

In a fairly short time turns into a hot,dense clump that produces largeamounts of energy.

In a very short time turns into a hot,dense clump that produces verylarge amounts of energy.

Uses nuclear fusion to produceenergy for about 10 billion years ifthe mass is the same as the Sun’s,or 100 billion years or more if themass is less than the Sun’s.

Uses nuclear fusion to produceenergy for only a few million years.It is perhaps 5000 times as bright asour Sun.

Uses nuclear fusion to produceenergy for only about one millionyears. It is extremely bright.

Uses up hydrogen and other fuels,and swells up into a large, cool redgiant.

Uses up hydrogen and other fuels,and swells to become a redsupergiant.

Uses up hydrogen and other fuels,and swells to become a redsupergiant.

Outer layers of gas drift away, andthe core shrinks to become a small,hot, dense white dwarf star.

Core collapses inward, sending theouter layers exploding as asupernova.

Core collapses, sending the outsidelayers exploding in a very largesupernova.

White dwarf star eventually coolsand fades.

Core material packs together as aneutron star. Gases drift off as anebula to be recycled.

Core material packs together as ablack hole. Gases drift off as anebula to be recycled.

The Life of Different Types of Stars

Note: These drawings are not to scale.

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Giants and Dwarfs

You can see in Figure 2 that when a star nears the end of its life it runs out of hydrogen and other fuels neededto produce energy. When this happens, the pressureholding the star together becomes reduced, so the starswells up while at the same time cooling down. Thus, in“old age” the star becomes larger and red. Stars the sizeof the Sun or smaller become red giants, while stars withmasses 10 times (or more) larger than the Sun’s becomered supergiants.

A star the size of the Sun or smaller is said to “die”when the nuclear reactions die down, the core shrinks,and the outer layers of the star drift away. The remainingmaterial becomes a white dwarf, a small star with ahigher temperature than red or yellow stars.

Supernovas

A supernova is an enormous explosionthat occurs at the end of a large star’slife. By this stage, the star has used upthe fuels needed to keep producingenergy by the process of nuclear fusion.With reduced pressure on the core, thecore collapses inward to become either aneutron star or a black hole (describedbelow). At the same time, shock wavescause the outer layers to explode outward in a rapidly expanding nebula of dust and gases.

Supernovas are rare events. A famous onewas observed in the year 1054 and wasrecorded in both China and India. It was sobright that people could see it even indaylight. It was visible for about 21 months.The gases spreading out from this supernovanow form the Crab Nebula, which can be seenin the constellation Taurus (Figure 3).

Since the telescope was first inventedabout 400 years ago, only one supernova hasever been seen with the unaided eye. Thisevent, now called Supernova 1987A (Figure 4),was discovered by a Canadian named IanShelton working at an observatory in Chile,South America.

Neutron Stars

When a star about 10 times the mass of theSun dies, the resulting core is called a neutronstar, an extremely dense star composed ofneutrons. The neutrons are so tightly packed,

Modelling a Black Hole

In a large, open area, securely tie a one-holed rubber stopper onto a 1-m length ofstring. Whirl the stopper around a finger(without hitting anybody!), allowing thestring to wind up on your finger until thestopper crashes into the finger.

1. In this model, what acts as the blackhole? What acts as the material near it?What force represents the force ofgravity?

2. What happens to the motion of therubber stopper as it gets closer andcloser to the finger? Relate this to whathappens to material near a black hole.

Figure 3

The supernova that created the Crab Nebula wasobserved in 1054. Other nebulas seen in the skyprovide evidence that supernovas have occurredmany times.

Did You Know

When our Suneventually swells

into a red giant star, itsouter layers will grow tobe about 100 times itspresent size swallowingup Mercury, Venus, Earth,and maybe even Mars.

Figure 4

Supernova 1987A, photographedthree years after the supernovawas first seen by Ian Shelton.Astronomers are observing thissupernova with great care. Whatthey learn from their observationsmay help them improve theirtheories about the lives of stars.

with no space between them, that a cupful of a neutronstar would have a mass of millions of kilograms. A pulsar isone type of neutron star. Pulsars emit pulses of very highenergy radio waves. Pulsars are very small, only about 20 km in diameter, but very dense, with about the samemass as a normal star. Pulsars rotate while emitting energyin the form of light and radio waves, like the rotating lightof a lighthouse—the effect is the energy reaches us aspulses. Today more than 400 pulsars have been identified.

Black Holes

When a star about 30 times the mass of the Sun dies, theresulting core is called a black hole, which is a small, verydense object with a force of gravity so strong that nothingcan escape from it. Even light cannot be radiated awayfrom its surface. That is why it is called a black hole(Figure 5).

Because light cannot escape the surface of black holes,they can exist undetected. Yet a Canadian astronomer,Tom Bolton, was able to confirm the existence of blackholes. What was his evidence? He observed a star thatappeared to be circling an invisible partner and noticedthat this partner was emitting X rays as it drew mattertoward itself from the star. These X rays confirmedBolton’s suspicions that the “invisible partner” was a blackhole. The word “hole” is misleading because it sounds asthough there is nothing there; it actually has a hugeamount of matter packed into a sphere only a fewkilometres across. It is so dense that a handful of it wouldhave a mass of perhaps 10 billion cars! This explains itsstrong gravitational pull. Perhaps “dark body” would be abetter name for this extremely rare type of object.

Figure 5

This is an artist's view of whathappens near a black hole. As ittwirls around, the hole attractsmaterials from a nearby startoward it. Why is this anexample of indirect evidence?


Understanding Concepts1. Describe how a star forms.

2. Describe the differences betweenthe life of a low-mass star and thatof a star 10 times the Sun’s mass.

3. What is a supernova?

Exploring4. Design and make a set of three-

dimensional models to illustratethe life of one of the types ofstars described in Figure 2.

5. Design a model of a black hole.Your model could use a circularmagnet, metal washers, andthread. If your teacher approvesyour design, try it. In what ways is it accurate?

Reflecting6. Describe why observing evidence

of a black hole is an example ofindirect evidence.

7. Think of circumstances in your lifewhere you draw conclusions usingindirect evidence. In eachsituation, what do you have toknow already, before you believethe indirect evidence?

How does the use of modelshelp to communicate theinformation in the challengeyou have chosen? What kindof models are most effective?

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You know how difficult it is to see the planets in our own solar system.Now imagine looking for planets travelling around stars other than ourown: other planetary systems. Planets are smaller than stars and do notemit light, so the task is not easy. Astronomers are continuallyusing newer and better technology and making use of bothdirect and indirect evidence to search for other planetarysystems in the universe. Learning about the formation ofplanets at various stages will help us better understand thedevelopment of the solar system and our own planet.

Evidence of Planetary Systems

What evidence do astronomers have of other planetarysystems? Shortly after its launch into orbit in 1983, the InfraredAstronomical Satellite or IRAS made some exciting discoveries.It detected a large cloud of tiny particles in orbit around thestar Vega. This was the first direct evidence that solid matterexists around a star other than our own Sun. Astronomersthought that the clouds of particles could be an early stage ofthe development of planets. Four months later, IRASdiscovered solid material orbiting another star.

More recently, the Hubble Space Telescope has obtainedimages of planetary systems being formed. Astronomers alsohave indirect evidence of other planetary systems. The pull ofgravity between a star and a nearby planet causes a slightwobble of the star’s motion. This wobble can be detected byobserving the star’s spectrum.

Formation of the Solar System

Figure 1 shows the steps that may have occurred in theformation of the Sun, planets, and other parts of our solarsystem. In its early stages, our solar system was part of a nebulaconsisting mainly of hydrogen and helium. Minute particles ofmatter, such as iron, rock, and ice, made up about 1% of thenebula. This solid matter formed as a result of neighbouringsupernova explosions from nearbystars.

Scientists think that our Sunformed about 4.6 billion years ago. At the same time, smaller clumps ofmatter began to contract in the outerregions of the solar nebula. Attractedby the force of gravity, the clumpsformed planets. This theory explainsthe formation of the gas giants

The Origin of the Planets

15.215.2

Figure 1

Astronomers think there were three mainstages in the formation of the solarsystem.

a Gravity caused components of arotating nebula to unite. Because ofits rotation, the nebula flattened outas it contracted.

b As the process continued, a bulgeformed toward the centre. This bulgelater became the Sun. Some of thedusty disk of cooler material furtherfrom the centre gathered together toform smaller chunks.

c These smaller chunks away from thebulge gradually grew into largerchunks, which eventually formed intoplanets.

Did You Know

The belt of asteroidslocated between

Mars and Jupiter likelywould have formed into aplanet if Jupiter’s strongforce of gravity hadn’tprevented the particlesfrom gathering together.


(Jupiter, Saturn, Uranus, and Neptune). The gas giants arecomposed mainly of hydrogen and helium gases: the samegases that make up much of the Sun. These planetsprobably formed in a way similar to the Sun—through theclouds of gases contracting due to gravity. But what aboutthe terrestrial planets? What is the current theory abouttheir formation?

The Terrestrial Planets and Minor Bodies

Mercury, Venus, Earth, and Mars are composed largely ofrock and iron, with little hydrogen and helium. In theearly stages of solar system formation, the gases in theinner regions of the solar system were probably too hot tocondense. The young Sun produced enough solar wind(bursts of charged particles) to blast most of the hydrogenand helium out of the inner regions of the solar system.Only the chunks of heavier matter—iron and rock—wereleft behind (Figure 2).

The terrestrial planets formed from those solid chunks.As chunks of solid matter circled the Sun, they eventuallycollided with one another and joined together. Duringmillions of years, some of the chunks grew in size untiltheir mass was large enough to have strong gravity. Themore massive chunks pulled in all the matter in the spacearound them. They eventually became the planets.

Over a long time (perhaps 10 million years), most ofthe matter in the solar system became concentrated intothe terrestrial planets and gas giants. The remainingmatter makes up the asteroids, meteoroids, and comets—the minor bodies. Studying these minor bodies providesinformation about the early stages of our solar system,before most of the matter formed into the planets.

Pluto’s origin is not certain as it has characteristics of aminor body, but is too far from the Sun to be explained bythe theory of formation for the terrestrial planets. It may bemore like a giant comet nucleus. The research is continuing.

Figure 2

3A

Research SkillsSKILLS HANDBOOK: 3A

The history of the terrestrial planets is

Understanding Concepts1. What force is responsible for

bringing together the particlesfound in space?

2. Describe, in order, the stages ofthe formation of the solar system.

3. (a) Which of the planets in thesolar system are thought tohave formed in a similarmanner to the Sun?

(b) Why is it unlikely that theother planets formed this way?

4. (a) What are the minor bodies ofthe solar system?

(b) What do astronomers hope tolearn from the minor bodies?

5. Assume that 10 years from nowastronomers discover planetstravelling around hundreds ofdifferent stars. Are the planetsthey discover more likely to begas giants or terrestrial planets?Explain.

Exploring6. Research the Kuiper Belt. Why is

its discovery a good example of atheory being supported byobservations? Why doastronomers think Pluto andNeptune’s moon Triton may havecome from the Kuiper Belt?

7. Research and report on the Oortcloud. Explain why comets providean opportunity to study what thesolar system may have been likebefore the planets formed.

8. Use an Internet resource toresearch recent discoveries ofplanetary systems. Make a visualdisplay of your discoveries.

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Paul Fjeld gives a thumbs up sign ashe steps out of the highperformance jet in which he has

just pulled 6 g’s. His call sign is “Fingers,”and he flies in jet fighters whenever he canas part of his research: Paul Fjeld is a

Canadian artist interested in space.Between 1971 and 1973 the Montreal Star newspaper sent a young

artist to cover the last three launches of Apollo. He convinced NASAto include him in their official Art Program; soon Fjeld got to gowhere even the press could not, including the Apollo simulator. Hisgreatest thrill was working in Mission Control during the 1975Apollo/Soyuz mission where he was made welcome and encouragedto “document what we were doing in a different way—for history.”

Fjeld’s first painting for NASA was of a crippled Skylab modulewith torn thermal shield and damaged solar arrays. Working withengineers from the manufacturer, he had to assess what the damagemight look like and prepare a visual image for the press. The CanadianSpace Agency has commissioned Fjeld to create large images of theInternational Space Station, the Canadarm, theSPDM (Figure 2, p. 499), and the varioussatellites. His work has appeared in NationalGeographic and on the cover of Aviation Week.

His favorite spacecraft is the Apollo LunarModule (seen in the painting with Armstrongand Aldrin). The skin of the insect-like robot isa paper-thin wrapping of aluminum. It is agreat subject to paint against the blackness ofspace. Actor Tom Hanks hired Fjeld to recreatethat lunar moment on a huge set for the TVseries From the Earth to the Moon.

What’s next for Paul Fjeld? Anotherpainting? A script for a movie? Whatever it is, itwill almost certainly involve his passion: space.

Explore

1. What skills and attitudes does the artistneed to capture what the camera cannotcapture?

2. If you were going to follow a similar careerpath, what would you study at secondaryand post-secondary school, and why?

3. When might humans again land on theMoon? Provide a rationale for your answer.

Space Artist

Career ProfileCareer Profile

”“I want to paint a picture as ifyou are actually there.


In this activity, you will use a model toillustrate the concept of an expandinguniverse. As you use the model, think of waysit might be improved.

Materials• 1 round balloon• black, fine point, felt tip pen• metric tape measure

Procedure

Copy Table 1 into your notebook.

Blow up the balloon to the size of anorange. While your partner keeps theballoon at that size by pinching theopening, use the felt tip pen to mark theballoon with four dots, each separated byabout 1 cm. Measure the exact distancesbetween the dots with the metric tape.Label the dots in order, A, B, C, D.

(a) Record the measured distancesbetween the dots in your data table.

Now inflate the balloon until it is aboutthe size of a basketball. Measure thedistances between the dots.

(a) Record the measured distances in yourdata table.

Calculate the distances A to C and B to Dfor both the first and second stages.

(a) Record these calculated distances inyour data table.

Look at how much the distances A to B, Bto C, and C to D increased when youinflated the balloon to the second stage.

(a) Compare those increases.

5

4

3

2

1

Suppose you continued to blow up theballoon.

(a) How do you think the change in thedistances A to B, B to C, and C to Dwould compare with the change fromthe first stage to the second stage?

Imagine that you are standing on dot Awhile the balloon is expanding.

(a) Which dot would appear to be movingaway from you most quickly?

(b)Which dot would appear to be movingaway from you most slowly?

(c) Would any dot appear to be movingtoward you?

Imagine that the dots on your expandingballoon are galaxies of stars in anexpanding universe.

(a) What difference would you expect tofind in how quickly nearby and distantgalaxies are moving away from Earth?

Now imagine that you are on a planet ingalaxy B looking at a planet in galaxy C.

(a) Do you think the spreading of thegalaxies would appear to be anydifferent from these two locations?Explain.

(b)If galaxy B is the Milky Way Galaxy, is itcorrect to say that galaxy B is thecentre of an expanding universe?Explain.

9

8

7

6

A Model of the Expanding Universe

15.3 Activity15.3 Activity

Table 1

Measured Calculateddistances (cm) distances (cm)

A to B B to C C to D A to C B to D

“Orange” stage ? ? ? ? ?

“Basketball” stage ? ? ? ? ?

Reflecting1. Although the balloon model was useful to

illustrate the concept of an expandinguniverse, it also had a major limitation.Identify the limitation and suggest a way toovercome it.

A balloon is a useful model in helping us imagine how the universeexpands: as the balloon expands, closely spaced dots on the surfacespread apart slowly; dots that are far apart spread apart more quickly.However, as a model, an expanding balloon has limitations. Forexample, galaxies are not found on a skin or membrane; instead, they are scatteredthroughout the universe.

How can we tell whethera galaxy is moving away fromus? After all, the galaxies arevery far away.

Before looking atevidence of an expandinguniverse, let’s review theproperties of light. Light is aform of energy that travels asa wave. Each colour has awavelength, which is thelength of one wave. Thevisible spectrum (Figure 1)consists of different colours,ranging from the longest wavelengths(red) to the shortest wavelengths (violet).

You already know that different starshave characteristic colours. The same istrue for galaxies: each galaxy emits its ownspectrum or range of colours in a patternthat astronomers recognize. As early as1912, astronomers observed evidence thatthe galaxies are moving away from Earthand from one another. This evidencecame from looking at the light spectra(patterns of colours) given off by nearbygalaxies. The spectrum of a moving objectin space is different from the spectrum ofan object that is not moving. An examplewill help explain this.

Imagine a duck bobbing up and downon the surface of a pond (Figure 2).Suppose the duck represents a source ofenergy. The ripples that spread out fromthe duck represent waves of energyemitted by the source. The distance fromthe top of one ripple to the top of thenext ripple represents one wavelength.

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Evidence of an Expanding Universe

15.415.4

Figure 1

The visible spectrum

Figure 3

Figure 2

a This model shows an energysource (the duck) sending outwaves (the water ripples)with a constant wavelength(the distance from the top ofone ripple to the top of thenext).

b Side view of the waves.

a The wavelengths becomeshorter in one direction andlonger in the other direction.

b A side view of the wavescreated by a bobbing duckmoving to the left.

Now, imagine yourself standing on the shore, watchingthe duck. If the duck swims toward you, the ripples infront of it are squeezed together and therefore haveshorter wavelengths (Figure 3). Meanwhile, the wavesbehind the duck are spread farther apart and so havelonger wavelengths. Even if you could not see the duckitself, you could observe from the changing wavelengthswhich way the duck was moving. Shorter wavelengthsindicate that the duck is moving toward you; longerwavelengths indicate that the duck is moving away fromyou. Of course you have to know what the wavelengthswould be if the energy source were stationary, relative toyou.

When astronomers look at a distant source of light,such as a galaxy, through a spectroscope, they recognizethe pattern of the spectrum but observe that the colours ofits lines are not the same as they would expect. The linesare moved toward the red end of the spectrum (Figure 4)meaning that they have a longer wavelength. Searching foran explanation, astronomers concluded that the light hasa longer wavelength than normal because the galaxy ismoving away from us. This movement, or shift, into thered end of the spectrum is called red shift.

The light energy from all distant galaxies shows redshift. However, there are different amounts of red shift.The greatest shifts occur for galaxies that are farthest awayfrom us. From this information, we can infer that allgalaxies are moving away from us and away from eachother. But what is causing this movement? Why is theuniverse expanding? Astronomers are investigating theanswers to these questions.

Understanding Concepts1. Copy Figure 5 into your notebook.

It is a pattern of ripples. Label theripples that have shorterwavelengths and those that havelonger wavelengths. Indicate thedirection of movement of the“object” causing the waves.Explain your answer.

2. What does “red shift” mean?

3. What evidence do astronomershave that the universe isexpanding?

4. If astronomers were to observe a“violet shift” for a certain star,what could they infer? Explainwhy.

5. If the duck in Figure 3a weretravelling from the top of thediagram toward the bottom, whatwould you observe? Draw adiagram and explain why.

Exploring6. How could you use water in a flat

container and a bobbing finger toillustrate changes in wavelengthas the source of the wavesmoves?

7. The scientific name for the causeof red shift is the “Dopplereffect.” Research this effect andrelate it to what you have learnedabout red shift. (The Dopplereffect relates to all types ofwaves, including sound waves.For now, focus on light waves.)

Figure 4

The top diagram represents the nine lines of a spectrum emitted by a stationarygalaxy. The second diagram represents the same nine lines of the samespectrum emitted by the galaxy if it were moving away from us rapidly. Thewavelengths of all the lines in the spectrum have shifted (moved) toward thered end. The bottom white light spectrum is shown for reference.

Figure 5


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Do you enjoy solving mysteries or putting the pieces of a puzzletogether? If so, perhaps a career in astronomy is ideal for you! One ofthe main goals of many astronomers is to solve the mystery of theorigin of the universe. These astronomers search for an answer to thequestion, “How did the universe begin?”

If stars go through cycles, beginning and ending as nebulas, doesthe entire universe also go through some type of cycle? Scientists donot know the answer to this question, but they have gathered enoughinformation to formulate a theory. This theory is based on evidencethat the size of the universe is not constant but is expanding. This isthe accepted theory, but it may be modified as more evidence iscollected and analyzed.

The study of the origin and changes of the universe is calledcosmology.

The Big Bang Theory

If the galaxies are moving apart, then presumably they used to becloser together. Still earlier, they must have been even closer together.Continue to move backward in time in your imagination and you willreach what we call “time zero.” Scientists estimate time zero as beingbetween 10 and 15 billion years ago. At that time, all the matter of theentire universe was packed together into one small, extremely dense,hot mass under enormous pressure. The event that occurred when theuniverse emerged from this state of enormous density and temperatureis known as the Big Bang (Figure 1). Scientists use the Big Bang theoryto describe the beginning of the universe that we know.

Scientists have more than just the red shift of distant galaxies asevidence of the Big Bang. They have also collected data that suggestthat, even today, the entire universe is “glowing” from that initialexplosive event, just as a piece of firewood continues to glow even afterthe fire has been put out. In 1965, for example, two scientists made an

The Origin of the Universe

15.515.5

Figure 1

These diagrams illustrate the Big Bang theory of the formation of the universe. The density ofthe material that made up the universe shortly after the Big Bang was immense. One cubiccentimetre of the material is estimated to have had a mass of one billion kilograms!


accidental discovery using a radio telescope. They detectedunexpected radiation coming from all directions in space.After checking that there were no defects in theirequipment, they concluded that this faint, unknownenergy is all that remains of the enormous amount ofenergy that exploded outwards at the time of the BigBang. The intense radiation from the tremendousexplosion has faded to only a faint “whisper” aftertravelling for thousands of millions of years through space.

The Big Bang theory can be used to explain ourobservation that the universe is expanding. But we stilldon’t know everything about how the universe began. Forexample, while scientists can describe what they thinkoccurred a fraction of a second after the Big Bang, they donot know what the universe was like (or even if it existed)just before the Big Bang explosion. Changing our theoriesabout the universe is a continuing scientific process as wetry to explain the new discoveries that astronomers makeyear after year (Figure 2).

However, the Big Bang theory is not the only way thatthe origin of the universe has been explained. In the past,many cultures have held different beliefs of their own.These beliefs, however, are not the same as scientifictheories—they cannot be tested, explored, and eithersupported or disproved by evidence. But each is a kind ofmodel that helps people understand how the world works.

Understanding Concepts1. How does the Big Bang theory

explain an expanding universe?

2. How does the development of theBig Bang theory illustrate thescientific process?

3. How could you use all thestudents in your class to act out amodel of the expanding universeshortly after the Big Bang?

Exploring4. Older theories about the universe

include the oscillating theory andthe steady state theory. Find outabout these theories, then writean article for a science magazinedescribing one of them. Drawillustrations representing thetheories to go with your article.

5. People in all parts of the worldhave had, and still do have, otherideas about the origin of theuniverse. Research and compareat least two contrasting culturalviews. Present your findings in acreative way.

Reflecting6. How does a scientific theory, such

as the Big Bang theory, differ froma belief?

Figure 2

The Antennae galaxies are a pair of galaxies whose collision has resulted in afirestorm of star birth activity. It is proving to be an excellent “laboratory” forstudying the formation of stars and star clusters.

The Big Bang theory is adifficult idea to conceptualize.What model or diagrams willyou use to explain it to thegeneral public?

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Figure 1 shows one of the most amazing images ever taken of outerspace. It is called the Hubble Deep Field. When you look at it, you arepeering back in time up to 8 billion years, into a part of the sky thatappears no bigger than a grain of sand resting on a fingernail of youroutstretched hand! Although this picture only shows you a tiny piece of the sky, it contains a lot of information. The only stars in thephotograph are the objects that appear to have spikes. (This featureresults from the wave nature of light.) All the other objects are galaxies.

The Hubble Deep Field

15.615.6 Case Study

Figure 1

This image was captured by the Hubble Space Telescope when it was aimed toward a part ofthe sky above the Northern Hemisphere.


(a) What can you infer about the number ofgalaxies in the universe? (In your answer,be sure to consider the concept of the“grain of sand” mentioned above.)

(b)Which types of galaxies can you see?

The image in Figure 1 was obtained by theHubble Space Telescope over a period ofabout 100 h. It is similar to a time-lapse photothat might be taken here on Earth.

(c) Why is time-lapse imaging important whenviewing faraway galaxies?

The “optical” portion of the Hubble SpaceTelescope includes a very large mirror,specially engineered with great precision.Unfortunately, there was an error in themanufacturing that was not detected until thetelescope was launched: the curvature of themirror was out by the thickness of a humanhair, so it could not focus as well as had beenhoped. Fortunately, astronauts were able tocorrect the problem in 1993 by adding asecondary mirror during a series of spacewalks. It was a delicate but successfuloperation. Other instruments have since beenadded to Hubble, improving its performancestill further.

(d)Why are more instruments added to theHubble Space Telescope, instead of beingput into orbit separately? What might bethe advantages of each alternative?

Advanced technology is needed to keep atelescope, travelling at almost 30 000 km/hwhile orbiting Earth, aimed steadily at onetiny spot for such a long time.

(e)Why wouldn’t the telescope naturally staypointed in the same direction? Make somepredictions.

This image sees deeper into space than anyprevious image. That is why it is called the“Hubble Deep Field.” The farthest objects,which are galaxies, are up to 8 billion light-years away. Galaxies 8 billion years ago hadless structured shapes than galaxies nowappear to have. This feature helps support the Big Bang theory.

Understanding Concepts1. How was the universe different 8 billion years

ago than it is now?

2. Explain how this image allows scientists to“peer back in time.”

Exploring3. If you were responsible for aiming the Hubble

Space Telescope to take a new Deep Fieldimage, in which direction would you aim it?Give reasons.

4. Research the problems with Hubble’s mirrorand how they were corrected. Draw a labelleddiagram to explain the repairs.

5. Research the costs involved with the HubbleSpace Telescope. Do you think it is a good usefor the money? Explain reasons for your opinionin a brief letter to a science magazine.

6. Find out what other Deep Field images havebeen taken. View the images on a NASA website.

(f) Explain how the less structured shape ofearly galaxies supports the Big Bangtheory.

Astronomers observe evidence of severalgalaxies colliding with each other shortly afterthe Big Bang.

(g)Propose a reason why galaxies in the pastwere more likely to collide than they arenow.

Studying such images in more detail will helpscientists better predict what might happen tothe universe in the future.

(h)If you were a scientist studying images likethis, what would you look for? Why?

Research SkillsSKILLS HANDBOOK: 3A

3A

482 Chapter 15

When you imagine an astronomer at work, you probablythink of someone gazing up at the sky or perhaps peeringthrough a telescope. Actually, today's astronomers spendmost of their time in front of computers. The computersanalyze the vast amounts of data that are collected by various instruments and reorganizethe information into forms that help theastronomer pick out what is important (Figure 1).Without computers, most research in astronomywould be slowed down because we would not beable to analyze information as fast as we arecollecting it. Computer technology has made alarge contribution to the extensive knowledge andunderstanding we now have of Earth and its placein the universe.

For example, an astronomer can study the glowingimage of an exploding star on a computer screen. Thecomputer created the image from data gathered by aseries of radio telescopes. The information is stored inthe computer, which creates a radio-wave “picture” of theexploding star—what you would see if you had eyes that could seeradio waves. Images like this give astronomers a new view of theuniverse. The astronomer may use the computer to display the imagein different ways to show certain features more clearly and to takemeasurements and make comparisons with previous data.

Computers are also essential in the radio search for extraterrestriallife. Only by using computers can scientists listen to all parts of space,at many different radio frequencies, for long periods of time. Scientistshope to detect radio signals that unknown beings might have sent fromother parts of the universe.

The Hubble Space Telescope (Figure 2) is constantly sendingcomputerized images of space to Earth. Astronomers can display theseimages on their computer screens, explore certain features, and makecalculations. They can also store the data, keeping it on hand for easyretrieval, should it be needed again.

As well as helping astronomers analyze, display, and store data,computers are used to control the operation of astronomicalinstruments. Imagine the problem of focusing on a galaxy when yourtelescope is moving along with Earth as it rotates. In the past,astronomers had to constantly turn their telescopes in the oppositedirection to Earth's rotation. Now, computers do all the calculationsand control the movement of the instruments.

Simulations are another important use of computers. Scientists mayapply known equations to simulate conditions deep within the Sun ortest models of the formation of the universe. Simulations can help

How Astronomers Use Computers

15.715.7

Did You Know

Earth may be the onlyplanet in our solar

system with the rightconditions to support life.But does life exist only onthis one planet in theentire universe? Scientistslook at many factors whentrying to determine if aplanet can support life. Inone ongoing investigation,a radio telescope scansthe sky 24 h a day. It islinked to computers thatsift through all theincoming radio signals in asearch for signs ofintelligent civilizations. Sofar, no signals have beenobserved, but researchcontinues. This kind ofsearch is called SETI,which stands for Searchfor ExtraTerrestrialIntelligence.

Figure 1

This is a false-colour image generated bycomputer using the image from a telescope. Itshows Eta Carinae—a dying star.


people learn about the universe and our own fragile andbeautiful planet as it travels in one tiny corner of a galaxythat contains about 400 billion stars.

Computers record large amounts of data, analyzethem, create pictures, do mathematical calculations, andoperate complicated astronomical instruments. They helpto bring the past into the present. But to someastronomers, the most exciting thing computers do iselectronically link scientists all over the world. Throughtheir computer networks, astronomers can share ideas,data, calculations, computer images, and the latestscientific information.

Understanding Concepts1. Why is the concept of an

astronomer continuously peeringthrough a telescope not validtoday?

2. In a chart, compare three usesastronomers make of computerstoday with how information usedto be managed.

3. Suggest how a computer couldhelp an astronomer analyzeimages of a star cluster.

Making Connections4. How can computers help in time-

lapse imaging of components ofthe sky? How do these imagesenhance our understanding of thehistory of the universe?

Exploring5. List concepts in the study of

astronomy that you think youcould understand better if youcould watch computer simulationsof the concepts. If a simulationprogram is available, try it out andevaluate its benefits.

Figure 2

This view of the Hubble Space Telescope shows the solar panels that changelight energy into electrical energy. Earth is seen in the background.

How can you use yourcomputer as a tool to help youin the challenge you havechosen?

Chapter 15 ReviewChapter 15 Review

484 Chapter 15

Key ExpectationsThroughout the chapter, you have hadopportunities to do the following things:

• Outline the current theory explaining theorigin, evolution, and fate of the Sun and otherstars. (15.1)

• Describe these components of the universe:nebulas; supernovas; neutron stars; black holes.(15.1)

• Outline the current theory explaining theformation of the solar system. (15.2)

• Describe and evaluate scientific evidence oforigin and evolution of the universe. (15.1,15.4, 15.5, 15.6)

• Plan ways to model answers to questions aboutthe history of the universe, and communicateresults. (15.3)

• Formulate and research questions related to thehistory of the universe, and communicateresults. (all sections)

• Describe how computers are used to enhanceour understanding of the universe. (15.7)

• Identify contributions of Canadian scientists tothe exploration of the universe. (15.1)

• Explore careers related to the exploration ofspace. (Career Profile)

KEY TERMS

Big Bang theory pulsarblack hole red giantcosmology red shiftgravity red supergiantnebula supernovaneutron star white dwarfplanetary system

Understanding Concepts1. Make a concept map to summarize the

material that you have studied in this chapter.Start with the words “Big Bang.”

2. (a) Arrange the following stages of the life of astar in the order in which they occur: blackhole; supernova; nebula; red supergiant.

(b) Is there more than one possible answer in(a)? Explain.

(c) Which type of star would go through thesestages?

3. (a) What is a nebula?(b) How are nebulas important to the

formation of stars and planets?

4. What process causes stars to reach “old age”?

5. What force leads to the formation of planets?

6. Why are white dwarf stars much morecommon than black holes in the universe?

7. Describe the relationship between a red giantand a white dwarf.

8. The following is a list of stages in the lives ofstars: white dwarf, supernova, red giant,neutron star, black hole.(a) Which of these stages, if any, will the Sun

pass through in the future?(b) Explain why the Sun will not pass through

the other stages.

9. (a) Since the invention of the telescope, howmany supernovas have been observed withthe unaided eye?

(b) How do astronomers benefit from studyingsupernovas?

10. Describe the Big Bang theory.

Reflecting• “Scientists use models and simulations to visualize

and explain the dynamic processes that form the

universe.” Reflect on this idea. How does it connect

with what you’ve done in this chapter? (To review,

check the sections indicated above.)

• Revise your answers to the questions raised in

Getting Started. How has your thinking changed?

• What new questions do you have? How will you

answer them?


11. Why is it difficult to observe planets in orbitaround distant stars?

12. Describe the current theory of the formationof the planets of our solar system. Illustrateyour answer with drawings.

13. (a) What is red shift?(b) How does red shift provide evidence for

the Big Bang?

14. What evidence besides red shift supports theBig Bang theory?

15. As scientists continue to observe the spectra ofstars and galaxies, what do you think theywould conclude if they observed thefollowing?(a) Red shift continued.(b) Red shift was no longer observed for any

star or galaxy.(c) A shift was observed toward the violet end

of the spectrum.

16. State, with reasons, whether you agree withthis statement: “Nebulas provide a goodexample of recycling in the universe.”

Applying Skills17. If you look at photographs of the Moon,

Mercury, Mars, and the moons of otherplanets, you will see evidence of collisions.(a) What is this evidence?(b) How does this evidence support the theory

of the formation of the solar system?(c) What evidence of collisions on Earth

supports the theory?

18. Describe examples in this chapter of indirectevidence used by astronomers.

19. Make a physical model or a computer modelto illustrate one of the concepts covered inthis chapter, such as the life of a star, or theexpanding universe.

20. The discovery of red shift supports the theoryof an expanding universe. However, it isindirect evidence, not proof, that galaxies aremoving away from each other. What otherinterpretations could there be of red shift?

21. Write at least five questions about the universethat you would like more complete answers to.

22. Choose one of the questions from your list in21. Describe how you would go about findingthe answer(s) to that question.

23. Research the most recent ideas about blackholes and prepare a presentation.

24. The light from two distant galaxies, A and B, isexamined through a spectroscope. The twoline spectra have a similar pattern of lines, butthe lines of Galaxy A’s spectrum have slightlylonger wavelengths than those of Galaxy B. (a) Draw what their two spectra might look

like. (b) What might you conclude about the

motions of the two galaxies, relative toEarth?

25. The star probe Stardust was launched in 1999to collect dust from the tail of comet Wild-2.Research the purpose and current status ofthis mission.

Making Connections26. Design a visual image that could be

attached to a space probe leaving the solarsystem. The image should communicateinformation about ourselves and our planet to intelligent aliens discovering the probe.Remember, they would not be able to read our written communications! Researchplaques that have been attached to probes that have already been launched.

27. Assume you have unlimited funds to carry out investigations to test one of the theoriespresented in this chapter. Which theory wouldyou test? How would you test it? Predict yourresults.

28. Some radio telescopes are used to try to detect intelligent life that may exist on planetsrevolving around other stars in the universe.What other methods could you suggest fortrying to find evidence of intelligent lifebeyond Earth (extraterrestrial intelligence)?Explain your answer.

29. Do you expect computers will be more or lessimportant in the study of astronomy in thefuture? Why?

chapter 15 the history of the universemrscoteohs.weebly.com/uploads/5/7/1/5/57154139/chapter...the...

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