LESSON 1: THE UNIVERSE and SOLAR SYSTEM
CONTENT STANDARD The learners learners demonstrate demonstrate an understanding understanding of 1. the for format mation ion of of the univ univers erse e PERFORMANCE STANDARD Learning Competency 1. Describe Describe the the historica historicall developmen developmentt of theories theories that that explain the origin of the (S11ES!a1". SPECIFIC LEARNING OBJECTIVES #t the end of the lesson$ the learners %ill be able to& Describe the structure and composition of the 'niverse State the di)erent hypothesis that preceded the *ig *ang Theory of the +rigin +rigin of the 'niverse. 'niverse. Explain the redshift and ho% it used as proof of an expanding universe Explain the *ig *ang Theory and evidences supporting the theory. • •
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INTRODUCTION
,hat is sho%n in the picture-
INTRODUCTION is
The 'niverse at least 1./
billion of years old and the Earth0 Solar System at least .2.3 billions of years old. #ny explanation of the origin of the 'niverse should be consistent %ith all information about its composition$ structure$ accelerating expansion$ cosmic micro%ave bac4ground radiation among others.
STRUCTURE/COMPOSITION/ and AGE •
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The universe as %e currently 4no% it comprises all space and time$ and all matter 5 energy in it. !t is made of .36 baryonic matter (7ordinary8 matter consisting of protons$ electrons$ and neutrons& atoms$ planets$ stars$ galaxies$ nebulae$ and other bodies"$ 96 cold dar4 matter (matter that has gravity but does not emit light"$ and :1.6 dar4 energy (a source of antigravity" Dar4 matter can explain %hat may be holding galaxies together for the reason that the lo% total mass is insu;cient for gravity alone to do so %hile dar4 energy can explain the observed accelerating expansion of the universe.
ed or combined0fused together. ?ost stars such as the Sun belong to the socalled 7main se@uence stars.8 !n the cores of such stars$ hydrogen atoms are fused through thermonuclear reactions to ma4e helium atoms (=g. ". ?assive main se@uence stars burn up their hydrogen faster than smaller stars. Stars li4e our Sun burn up hydrogen in about 1A billion years.
The remaining dust and gas may end up as they are or as planets$ asteroids$ or other bodies in the accompanying planetary system. # galaxy is a cluster of billions of stars and clusters of galaxies form superclusters. !n bet%een the clusters is practicallyan empty space. This organi>ation of matter in the universe suggests that it is indeed clumpy at a certain scale. *ut at a large scale$ it appears homogeneous and isotropic.
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*ased on recent data$ the universe is 1./ billion years old. The diameter of the universe is possibly in=nite but should be at least B1 billion light years (1 light year B.3A: 1A19 4m". !ts density is .2 x 1A1 g0cm.
ADDITIONAL INFO:
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INFO TIP 5 !sotropic having physical properties that are the same %hen measured in di)erent directions I T%o %ays by %hich astronomers estimate the age of the 'niverse& 1" by estimating the age of the loo4ing oldest stars and 9" by measuring the rate of expansion of the universe and extrapolating bac4 to the *ig *ang 0
CHARACTERISTICS OF THE UNIVERSE 10 UNIVERSE IS E6PANDING !n 1B9B$ Ed%in
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Med shift as evidence for an expanding universe. The positions of the absorptions lines for helium for light coming from the Sun (#" are shifted to%ards the red end as compared %ith those for a distant star (*".
70 COSMIC BAC8GROUND RADIATION •
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There is a pervasive cosmic micro%ave bac4ground (C?*" radiation in the universe. !ts accidental discovery in 1B3 by #rno Nen>ias and Mobert ,oodro% ,ilson earned them the physics Hobel Nri>e in 1B:/. !t can be observed as a stri4ingly uniform faint glo% in the micro%ave band coming from all directions blac4body radiation %ith an average temperature of about 9.: degrees above absolute >ero.
ORIGIN OF THE UNIVERSE 10 NON 9 SCIENTIFIC THOUGHT #ncient Egyptians believed in many gods and myths %hich narrate that the %orld arose from an in=nite sea at the =rst rising of the sun. The Ouba people of Central #frica tell the story of a creator god ?bombo (or *umba" %ho$ alone in a dar4 and %atercovered Earth$ felt an intense stomach pain and then vomited the stars$ sun$ and moon. !n !ndia$ there is the narrative that gods sacri=ced Nurusha$ the primal man %hose head$ feet$ eyes$ •
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and mind became respectively.
the
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earth$
sun$
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moon
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T$i+ i+ +i,i(a #' #$! D'..(! E!-# *' +'und a&!+: #' a +#a#i'na ')+!&!% #$! *!;u!n- ' .i#-$ '* a !-!ding +'u-! d!-!a+!+ a+ i# ,'&!+ aa0 •
The no% discredited steady state model of the universe %as proposed in 1B/ by *ondi and ould and by
<0 BIG BANG THEORY
'nli4e hypotheses in the sciences$ religious beliefs cannot be subJected to tests using the scienti=c method. Gor this reason$ they cannot be considered valid topic of scienti=c in@uiry.
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The monotheistic religions of Pudaism$ Christianity$ and !slam claim that a supreme being created the universe$ including man and other living organisms.
70 STEADY STATE MODEL
#s the currently accepted theory of the origin and evolution of the universe$ the *ig *ang Theory postulates that 1./ billion years ago$ the universe expanded from a tiny$ dense and hot mass to its present si>e and much cooler state. The theory rests on t%o ideas& eneral Melativity and the Cosmological Nrinciple. !n
EinsteinKs eneral Theory of Melativity$ gravity is thought of as a distortion of spacetime and no longer described by a gravitational =eld in contrast to the La% of ravity of !saac He%ton. eneral Melativity explains the peculiarities of the orbit of ?ercury and the bending of light by the Sun and has passed rigorous tests. The Cosmological Nrinciple assumes that the universe is homogeneous and isotropic %hen averaged over large scales. This is consistent %ith our current largescale image of the universe. *ut 4eep in mind that it is clumpy at smaller scales. The *ig *ang Theory has %ithstood the tests for expansion& 1" the redshift 9" abundance of hydrogen$ helium$ and lithium$ and " the uniformly pervasive cosmic micro%ave bac4ground radiationthe remnant heat from the bang.
Big Bang Ti,!(in!
E&'(u#i'n '* #$! Uni&!+! a--'ding #' #$! Big Bang T$!'
The uniform nature (even in all direction" of the C?* precludes propagation from a point source (i.e. from ancient stars as explained by the steady state model".
?isconception& The 7bang8 should not be ta4en as an explosion it is better thought of a simultaneous appearance of space every%here. The theory does not identify the cause of the 7bang.8
Grom time >ero (1./ billion years ago" until 1A second later$ all matter and energy in the universe existed as a hot$ dense$ tiny state (=g. :". !t then under%ent extremely rapid$ exponential inQation until 1A9 second later after %hich and until 1A seconds from time >ero$
conditions allo%ed the existence of only @uar4s$ hadrons$ and leptons. Then$ *ig *ang nucleosynthesis too4 place and produced protons$ neutrons$ atomic nuclei$ and then hydrogen$ helium and lithium until 9A minutes after time >ero %hen su;cient cooling did not allo% further nucleosynthesis. Grom then on until /A$AAA years$ the cooling universe entered a matterdominated period %hen photons decoupled from matter and light could travel freely as still observed today in the form of cosmic micro%ave bac4ground radiation. #s the universe continued to cool do%n$ matter collected into clouds giving rise to only stars after /A$AAA years and eventually galaxies %ould form after 1AA million years from time >ero during %hich$ through nucleosynthesis in stars$ carbon and elements heavier than carbon %ere produced. Grom B./ billion years until the present$ the universe became dar4energy dominated and under%ent accelerating expansion. #t about B./ billion years after the big bang$ the solar system %as formed.
INFO TIP: !t %as previously thought that the gravity %ould eventually stop the expansion and end the universe %ith a 7*ig Crunch8 and perhaps to generate another 7bang8. This %ould occur if the density of the universe is greater than the critical density. *ut if it is lo%er$ there %ould be not enough gravitational force to stop or reverse the expansionthe universe %ould expand forever leading to the 7*ig Chill8 or 7*ig Gree>e8 since it cools during expansion. The recent observation of accelerating expansion suggests that the universe %ill expand exponentially forever. Submitted %or4 may be evaluated using the follo%ing criteria&
Logical discussion of scienti=c concepts used for the argument (e.g. e)ects of gravity$ expansion" consistent discussions of pros and cons. Logical buildup of reasoning to support the choice.
