EARTH SCIENCE
WRITTEN WORK25%PERFORMANCETASK50%QUARTERLYASSESSMENT 25%
Marjorie B. Regalado
Objective
◦Describe the structure andcomposition of the Universe
◦Explain the red-shift and howit used as proof of anexpanding universe
Terms
◦a. Baryonic matter - "ordinary" matter consisting ofprotons, electrons, and neutrons that comprisesatoms, planets, stars, galaxies, and other bodies
◦b. Dark matter - matter that has gravity but doesnot emit light.
◦c. Dark Energy - a source of anti-gravity; a forcethat counteracts gravity and causes the universeto expand.
Terms
◦d. Protostar- an early stage in theformation of a star resulting from thegravitational collapse of gases.
◦e. Thermonuclear reaction - anuclear fusion reaction responsiblefor the energy produced by stars.
Terms
◦f. Main Sequence Stars - stars that fuse hydrogenatoms to form helium atoms in their cores;
◦outward pressure resulting from nuclear fusion isbalanced by gravitational forces
◦g. light years - the distance light can travel in ayear; a unit of length used to measureastronomical
◦distance
◦the Universe is at least 13.8billion of years old and theEarth/Solar System at least4.5-4.6 billions of years old.
◦But how large exactly is abillion?
◦How long will it takethem to spend 1billion pesos if theyspend 1 peso persecond?
Origin of the Universe
◦composition,
◦structure,
◦accelerating expansion,
◦cosmic microwave backgroundradiation (CMBR)
Structure, Composition, and Age
◦The universe as we currently know itcomprises all space and time, and allmatter & energy in it.
◦It is made of 4.6% baryonic matter (“ordinary” matterconsisting of protons, electrons, and neutrons: atoms,planets, stars, galaxies, nebulae, and other bodies),24% cold dark matter (matter that has gravity butdoes not emit light), and 71.4% dark energy (a sourceof antigravity)
◦Dark matter can explain whatmay be holding galaxiestogether for the reason that thelow total mass is insufficient forgravity alone to do so while darkenergy can explain the observedaccelerating expansion of theuniverse.
◦Hydrogen, helium, and lithium are the threemost abundant elements.
◦• Stars - the building block of galaxies born outof clouds of gas and dust in galaxies (fig. 4).
Instabilities within the clouds eventually resultsinto gravitational collapse, rotation, heating up,
and transformation to a protostar-the core of afuture star as thermonuclear reactions set in.
◦Stellar interiors are like furnaces where elementsare synthesized or combined/fused together.
◦Most stars such as the Sun belong to the so-called “main sequence stars.” In the cores ofsuch stars, hydrogen atoms are fused throughthermonuclear reactions to make helium atoms(fig. 4). Massive main sequence stars burn uptheir hydrogen faster than smaller stars. Stars likeour Sun burnup hydrogen in about 10 billionyears.
◦Hydrogen and Helium as themost abundant elements in theuniverse.
◦Having the lowest mass, theseare the first elements to beformed in the Big Bang Model ofthe Origin of the Universe.
• Forming He from H gives off lots
of energy(i.e. a natural hydrogen
bomb).
• Nucleosynthesis requires veryhigh T.
The minimum T for H fusion is5x106oC.
◦• The remaining dust andgas may end up as theyare or as planets,asteroids, or other bodiesin the accompanyingplanetary system.
◦A galaxy is a cluster of billions of starsand clusters of galaxies formsuperclusters. In between the clusters ispractically an empty space.
◦This organization of matter in theuniverse suggests that it is indeedclumpy at a certain scale.
◦But at a large scale, it appearshomogeneous and isotropic.
◦Based on recent data, theuniverse is 13.8 billion years old.
◦ The diameter of the universe is
possibly infinite but should be atleast 91 billion light-years (1 light-year = 9.4607 × 1012 km).
Its density is 4.5 x 10-31 g/cm3.
C. Expanding Universe
◦• In 1929, Edwin Hubble announced hissignificant discovery of the “redshift” (fig. 5)and its interpretation that galaxies aremoving away from each other, hence asevidence for an expanding universe, just aspredicted by Einstein’s Theory of GeneralRelativity.
Edwin Hubble
◦• He observed that spectral lines ofstarlight made to pass through a prismare shifted toward the red part of theelectromagnetic spectrum, i.e., towardthe band of lower frequency; thus, theinference that the star or galaxy must bemoving away from us.
Red shift asevidence for anexpandinguniverse. Thepositions ofthe absorptionslines for helium forlight coming fromthe Sun (A) areshifted towards thered end ascompared withthose for a distantstar (B).
◦This is similar to the Dopplereffect for sound waves: to astationary observer, thefrequency or pitch of areceding source decreasesas it moves away.
◦• This evidence forexpansion contradictedthe previously held view ofa static and unchanging
◦universe.
◦• Isotropic - having physical properties
◦that are the same when measured in
◦different directions
◦• Two ways by which astronomers
◦estimate the age of the universe
◦:1) by estimating the age of the looking
◦oldest stars; and 2) by measuring the
◦rate of expansion of the universe and
◦extrapolating back to the Big Bang.