The Earth’s MotionThe Earth’s Motion

Chapter 2Chapter 2

Does the Earth MoveDoes the Earth Move How do we know that the earth is How do we know that the earth is

moving?moving? How do you know that when in a car that How do you know that when in a car that

the car is moving?the car is moving? If the earth is moving why don’t we fall If the earth is moving why don’t we fall

off?off?

The Geocentric The Geocentric TheoryTheory

The earth is the center and the universe The earth is the center and the universe moves around the earth.moves around the earth.

Ancient astronomers found seven Ancient astronomers found seven heavenly objects that were different:heavenly objects that were different: Moon, Mercury, Venus, Sun, Mars, Jupiter Moon, Mercury, Venus, Sun, Mars, Jupiter

and Saturn (in that order)and Saturn (in that order) These objects moved slowly among the These objects moved slowly among the

stars, which were the outermost layerstars, which were the outermost layer

The Geocentric TheoryThe Geocentric Theory Ancient astronomers believed that the sun’s Ancient astronomers believed that the sun’s

sphere turned once each day.sphere turned once each day. The other planets turned nearly once each day, The other planets turned nearly once each day,

but at slightly different rates.but at slightly different rates. This explained the independent paths of the planets.This explained the independent paths of the planets.

The moon’s sphere turned much more slowly The moon’s sphere turned much more slowly allowing it to change position rapidly.allowing it to change position rapidly. Explained why the moon rises about 50 minutes Explained why the moon rises about 50 minutes

later each night.later each night.

Geocentric ScientistsGeocentric Scientists Hipparchus – Greek astronomer around Hipparchus – Greek astronomer around

190-120 BC.190-120 BC. Created one of the earliest catalogs of 850 Created one of the earliest catalogs of 850

stars. stars. Developed a mathematical geocentric Developed a mathematical geocentric

model.model.

Geocentric Geocentric ScientistScientist

Ptolemy – a.k.a Cladius Ptolemaeus – AD Ptolemy – a.k.a Cladius Ptolemaeus – AD 85-165 - Alexandrian (Egyptian) 85-165 - Alexandrian (Egyptian) astronomer.astronomer. Presented the geocentric theory in a large Presented the geocentric theory in a large

collection of writing titled collection of writing titled The Greatest The Greatest CompilationCompilation – a.k.a. – a.k.a. AlmagestAlmagest

Geocentric theory is sometimes referred to as Geocentric theory is sometimes referred to as the Ptolemaic theory because he played such a the Ptolemaic theory because he played such a large role in attempting to improve the theory.large role in attempting to improve the theory.

Problems with Geocentric Problems with Geocentric TheoryTheory The Planets sometime appear to be large, The Planets sometime appear to be large,

bright, and close compared to other times bright, and close compared to other times when they seem smaller, dimmer, and when they seem smaller, dimmer, and farther away.farther away. Ptolemy tried to shift each planet so that the earth Ptolemy tried to shift each planet so that the earth

was no longer the center causing an eccentric was no longer the center causing an eccentric (off-center circle).(off-center circle).

Astronomers were offended by this because it was Astronomers were offended by this because it was not a symmetrical and in their eyes not a beautiful…not a symmetrical and in their eyes not a beautiful…but it did make the model closer to the observations.but it did make the model closer to the observations.

Problems with Geocentric Problems with Geocentric TheoryTheory

Model also could not explain why it Model also could not explain why it appeared that planets had retrograde appeared that planets had retrograde motion.motion. Planets slowed down, stopped, and then Planets slowed down, stopped, and then

appeared to back up.appeared to back up. The planets would trace a backward loop The planets would trace a backward loop

and then resume their forward motion.and then resume their forward motion.

Problems with Geocentric Problems with Geocentric TheoryTheory

Ptolemy explained Ptolemy explained retrograde motion by imagining that each retrograde motion by imagining that each

planet moved in small circles called epicycles. planet moved in small circles called epicycles. The planets continued to revolve around the The planets continued to revolve around the

earth also.earth also. He called the normal forward path the deferent He called the normal forward path the deferent

so that it did not get confused with the so that it did not get confused with the epicycle.epicycle.

http://videos.howstuffworks.com/hsw/20230-distance-and-time-ptolemy-video.htmhttp://videos.howstuffworks.com/hsw/20230-distance-and-time-ptolemy-video.htm

Major Objections to Major Objections to Geocentric TheoryGeocentric Theory

Inaccuracy – astronomers tried MANY Inaccuracy – astronomers tried MANY different values for the distances of the different values for the distances of the planets as well as their speeds to explain planets as well as their speeds to explain the was observed.the was observed.

Complexity – the more they tried to Complexity – the more they tried to change for the explanation the more change for the explanation the more confusing it became.confusing it became.

The Heliocentric The Heliocentric TheoryTheory

The RenaissanceThe Renaissance Fourteenth, Fifteenth, and Sixteenth centuries Fourteenth, Fifteenth, and Sixteenth centuries

brought the great rebirth of learning.brought the great rebirth of learning. Renewed interest in every area of culture: art, Renewed interest in every area of culture: art,

literature, music, drama, geography, science, and literature, music, drama, geography, science, and medicine.medicine.

Also, a reawakening for the Bible.Also, a reawakening for the Bible. Gutenberg printing press allowed for books to be Gutenberg printing press allowed for books to be

reprinted more easily.reprinted more easily.

The Heliocentric TheoryThe Heliocentric Theory Sun centered as opposed to Earth Sun centered as opposed to Earth

centered.centered. The sun remains still and everything The sun remains still and everything

revolves around it with the exception of revolves around it with the exception of the Earth’s moon.the Earth’s moon.

The Earth’s moon revolves around the The Earth’s moon revolves around the Earth.Earth.

Heliocentric ScientistsHeliocentric Scientists Copernicus Copernicus AquinasAquinas GalileoGalileo KeplerKepler NewtonNewton TychoTycho

CopernicusCopernicus Polish – formulated the heliocentric theoryPolish – formulated the heliocentric theory

Born during the renaissance.Born during the renaissance. Disillusioned by the many “tricks” that must be Disillusioned by the many “tricks” that must be

played to get the Geocentric Theory to work.played to get the Geocentric Theory to work. Author of “Author of “The Six Books Concerning the The Six Books Concerning the

Revolutions of the Heavenly Spheres”Revolutions of the Heavenly Spheres” or or “The “The Revolutions”Revolutions” for short. for short.

Answered many arguments that critics tried.Answered many arguments that critics tried.

Copernicus’ ArgumentsCopernicus’ Arguments CriticsCritics

Spinning earth would fly apartSpinning earth would fly apart

Birds would be left behindBirds would be left behind

If earth revolved around sun If earth revolved around sun then the nearer stars would then the nearer stars would shift their position compared to shift their position compared to distant stars when viewed from distant stars when viewed from different placesdifferent places

AnswersAnswers Rotating sky more likely Rotating sky more likely

to fly apart because of to fly apart because of sizesize

Earth drags along the Earth drags along the atmosphere including atmosphere including birdsbirds

They do indeed shift and They do indeed shift and it can be seen with a it can be seen with a telescopetelescope

Copernicus’ ArgumentsCopernicus’ Arguments Also addressed the issue of planets Also addressed the issue of planets

appearing to move backwards.appearing to move backwards. Proved that as the earth caught up to a slower Proved that as the earth caught up to a slower

moving planet such as Mars or Jupiter, it would moving planet such as Mars or Jupiter, it would appear to make the planet go backwards as the appear to make the planet go backwards as the earth went by.earth went by.

Heliocentric Theory is also called the Heliocentric Theory is also called the Copernican Theory because of his Copernican Theory because of his advances.advances.

Tycho BraheTycho Brahe Danish noblemanDanish nobleman One of the most accurate astronomical One of the most accurate astronomical

observers is history.observers is history. He did not agree with Copernicus, but his He did not agree with Copernicus, but his

observations helped to establish the observations helped to establish the Heliocentric theory as superior.Heliocentric theory as superior.

Built an observatory on the Isle of Hven near Built an observatory on the Isle of Hven near Copenhagen and studied for the next 20 years Copenhagen and studied for the next 20 years the positions of stars and planets.the positions of stars and planets.

Johannes KeplerJohannes Kepler

German astronomer, Outstanding Christian German astronomer, Outstanding Christian and brilliant mathematicianand brilliant mathematician

Joined Tycho’s staff in 1600 in Prague after Joined Tycho’s staff in 1600 in Prague after protestants were persecuted and forced to protestants were persecuted and forced to leave Austria.leave Austria.

He recognized the brilliance of Tycho’s He recognized the brilliance of Tycho’s work.work.

Devised three laws that described the Devised three laws that described the planetary motion.planetary motion.

Johannes KeplerJohannes Kepler First two laws published in a book “New First two laws published in a book “New

Astronomy” in 1609.Astronomy” in 1609. Third law came in 1618.Third law came in 1618. His major contribution to the Copernican His major contribution to the Copernican

theory was his mathematical proof that the theory was his mathematical proof that the orbits of the planets were actual ellipitical.orbits of the planets were actual ellipitical.

Very important that his work glorify God.Very important that his work glorify God. http://videos.howstuffworks.com/hsw/23314-the-history-of-astronomy-laws-of-planetary-http://videos.howstuffworks.com/hsw/23314-the-history-of-astronomy-laws-of-planetary-

motion-video.htmmotion-video.htm

GalileoGalileo First to use a telescope for astronomyFirst to use a telescope for astronomy First to observe that Venus has phases like First to observe that Venus has phases like

the moon.the moon. First to observe Saturn’s rings, but he did not First to observe Saturn’s rings, but he did not

identify them as rings.identify them as rings. Discovered the four largest moons of Jupiter.Discovered the four largest moons of Jupiter. Jupiter’s moons helped solidify the sun Jupiter’s moons helped solidify the sun

centered and earth rotating around it theorycentered and earth rotating around it theory

GalileoGalileo Galileo’s book Dialogue on the Two Chief Galileo’s book Dialogue on the Two Chief

World Systems was banned by the Catholic World Systems was banned by the Catholic church.church.

The church had accepted the geocentric The church had accepted the geocentric theory and centered their doctrine around it.theory and centered their doctrine around it.

He was tried before the Catholic Inquisition He was tried before the Catholic Inquisition and placed on house arrest for the rest of and placed on house arrest for the rest of his life.his life.

NewtonNewton

English mathematician and physicist that English mathematician and physicist that described the force between the sun and described the force between the sun and the celestial objects around it.the celestial objects around it.

Was inspired to formulate the law of Was inspired to formulate the law of gravity by an apple falling from a tree.gravity by an apple falling from a tree.

Described that the more mass an object Described that the more mass an object has the more force it exerts on other has the more force it exerts on other objects.objects.

NewtonNewton Law of Universal Gravitation – Any two bodies Law of Universal Gravitation – Any two bodies

attract each other with a force proportional to attract each other with a force proportional to the product of their masses and inversely the product of their masses and inversely proportional to the square of the distance proportional to the square of the distance between them.between them.

Gravity provides the force that holds the Gravity provides the force that holds the planets in orbit around the sun and the moons planets in orbit around the sun and the moons around the planets.around the planets.

http://videos.howstuffworks.com/hsw/19121-exploring-gravity-the-law-of-universal-http://videos.howstuffworks.com/hsw/19121-exploring-gravity-the-law-of-universal-gravitation-video.htmgravitation-video.htm

FoucaultFoucault

French physicist who determined the speed of French physicist who determined the speed of light.light.

Hung a pendulum in the Pantheon to prove Hung a pendulum in the Pantheon to prove that the earth rotates.that the earth rotates.

The swing of the pendulum changed as the The swing of the pendulum changed as the earth rotated.earth rotated.

http://www.classzone.com/books/http://www.classzone.com/books/earth_science/terc/content/visualizations/earth_science/terc/content/visualizations/es0403/es0403page01.cfm?es0403/es0403page01.cfm?chapter_no=visualizationchapter_no=visualization

AquinasAquinas Italian philosopherItalian philosopher Thought he could reconcile the natural Thought he could reconcile the natural

philosophy and thinking of the ancient philosophy and thinking of the ancient pagans with Christianity.pagans with Christianity.

Chapter 2 part BChapter 2 part BEvidence That the Earth Evidence That the Earth MovesMoves Two motions:Two motions:

Rotates – spins around an imaginary line Rotates – spins around an imaginary line (axis)(axis)

Revolves – moves around the sun in its orbitRevolves – moves around the sun in its orbit Both motions can be proven from Both motions can be proven from

observationsobservations

Evidence of RotationEvidence of Rotation The sun, moon, planets, and stars rise in The sun, moon, planets, and stars rise in

the east and set in the west.the east and set in the west. Northern stars move counterclockwise in Northern stars move counterclockwise in

circles centered on the North Starcircles centered on the North Star

Earth’s ShapeEarth’s Shape Earth’s Shape – slightly flattened at the Earth’s Shape – slightly flattened at the

poles and bulging at the equator; 7928 poles and bulging at the equator; 7928 miles around equator but 7901 miles miles around equator but 7901 miles around the poles.around the poles.

Jupiter and Saturn spin the fastest and Jupiter and Saturn spin the fastest and show this effect the greatest; can see show this effect the greatest; can see through a telescope that these planets through a telescope that these planets are not round.are not round.

Earth’s ShapeEarth’s Shape Mercury and Venus, the slowest spinning Mercury and Venus, the slowest spinning

planets appear the most spherical.planets appear the most spherical. Inertia – the tendency of moving matter Inertia – the tendency of moving matter

to continue moving in the same direction.to continue moving in the same direction. The planet’s surface is moving fastest at The planet’s surface is moving fastest at

the equator which explains the bulge at the equator which explains the bulge at the equator. the equator.

Spinning DemoSpinning Demo

Wind Patterns and Wind Patterns and Projectile PathsProjectile Paths Wind patterns would be much simpler if the Wind patterns would be much simpler if the

earth did not rotate; the warm air from earth did not rotate; the warm air from equator would move toward poles and equator would move toward poles and cooler air from higher latitudes would move cooler air from higher latitudes would move toward equator; straight north and south.toward equator; straight north and south.

Coriolis effect – tendency for objects Coriolis effect – tendency for objects moving in straight path to curve moving in straight path to curve

Surface of the earth moves at different Surface of the earth moves at different speeds at different latitudes.speeds at different latitudes.

Foucault PendulumFoucault Pendulum Understood inertia – an moving object Understood inertia – an moving object

continues moving in the same direction continues moving in the same direction unless acted upon by an outside force.unless acted upon by an outside force.

At the poles the earth turns at a rate of 15° At the poles the earth turns at a rate of 15° per hour, 90° per six hours, 360° in 24 hoursper hour, 90° per six hours, 360° in 24 hours

At the equator the you would not see the At the equator the you would not see the degree changes because the earth is moving degree changes because the earth is moving with the point of attachement.with the point of attachement.

Direct ObservationDirect Observation Astronauts on the moon saw the entire Astronauts on the moon saw the entire

surface of the earth within 24 hours. surface of the earth within 24 hours. Since the moon does not revolve around Since the moon does not revolve around the earth each day it could only mean the earth each day it could only mean that the earth was rotating.that the earth was rotating.

Evidence of the Earth’s Evidence of the Earth’s RevolutionRevolution Evidence that supports both theories Evidence that supports both theories

includes the sun’s apparent path through includes the sun’s apparent path through the stars and the earth’s seasons.the stars and the earth’s seasons.

Sun’s APPARENT Motion Sun’s APPARENT Motion - Ecliptic- Ecliptic When looking at an object in front of a When looking at an object in front of a

moving background it can appear that the moving background it can appear that the object is the one moving.object is the one moving.

The sun appears to be moving when you The sun appears to be moving when you look at the sun with the stars in the look at the sun with the stars in the background. background.

Really the stars are the objects moving; Really the stars are the objects moving; they rise approximately 4 minutes earlier they rise approximately 4 minutes earlier each day.each day.

SeasonsSeasons Why do we not experience summer when Why do we not experience summer when

the earth is closest to the sun?the earth is closest to the sun? The tilt of the earth’s axis!The tilt of the earth’s axis!

Three reasons why summer is warmer:Three reasons why summer is warmer: Day is longer so heat is absorbed longerDay is longer so heat is absorbed longer Sun rays are more concentrated; absorb Sun rays are more concentrated; absorb

more energy per square kilometermore energy per square kilometer Higher angle sun rays lose less energy to the Higher angle sun rays lose less energy to the

atmosphere as the travel a shorter distanceatmosphere as the travel a shorter distance

SolsticesSolstices and Equinoxes and Equinoxes Summer Solstice – June 21 – Summer Solstice – June 21 –

Sun is directly over the Tropic Sun is directly over the Tropic of Cancer; sun’s apparent of Cancer; sun’s apparent northward motion stops; northward motion stops; appears to move southward.appears to move southward.

Winter Solstice – December Winter Solstice – December 21 – Sun is directly over the 21 – Sun is directly over the Tropic of Capricorn; sun’s Tropic of Capricorn; sun’s apparent southward motion apparent southward motion stops; appears to move stops; appears to move northward.northward.

Solstices and Solstices and EquinoxesEquinoxes Vernal Equinox - ~March Vernal Equinox - ~March

21 – The sun is directly 21 – The sun is directly over the equator.over the equator.

Autumnal Equinox - ~ Autumnal Equinox - ~ September 22 – The Sun September 22 – The Sun is directly over the is directly over the equator.equator.

These dates can These dates can fluctuate by a day fluctuate by a day because of leap year.because of leap year.

Stellar ParallaxStellar Parallax Stellar – means starsStellar – means stars Parallax – the Parallax – the

apparent shift of apparent shift of nearby stars among nearby stars among farther stars as the farther stars as the earth’s position earth’s position around the sun around the sun changes.changes.

Eye Demo:Eye Demo:

Stellar ParallaxStellar Parallax Wilhelm Bessel first discovered a star’s Wilhelm Bessel first discovered a star’s

parallax in 1838.parallax in 1838. The closer the star the less parallax is The closer the star the less parallax is

observable. The first star observed for observable. The first star observed for parallax was 67 trillion miles away.parallax was 67 trillion miles away.

Meteoric EvidenceMeteoric Evidence

The meteors are generally brighter and The meteors are generally brighter and more plentiful after midnight.more plentiful after midnight. The observer is on the leading side of the earth The observer is on the leading side of the earth

as it races along its orbit, logically causing more as it races along its orbit, logically causing more collisions on the “front” side of the earth.collisions on the “front” side of the earth.

If the earth were stationary there wouldn’t be an If the earth were stationary there wouldn’t be an explanation that could satisfy this observation.explanation that could satisfy this observation.

CalendarsCalendars The first recording of a time reference was The first recording of a time reference was

Genesis 1:5, “The evening and the morning were Genesis 1:5, “The evening and the morning were the first day”the first day”

Lunar – totally based on the moon’s phases Lunar – totally based on the moon’s phases (Muslims)(Muslims)

Lunisolar – based on both the moon’s phases Lunisolar – based on both the moon’s phases and the solar year (Hebrew and Chinese)and the solar year (Hebrew and Chinese)

Solar (Julian) – based only on the sun. Used for Solar (Julian) – based only on the sun. Used for all national governments. all national governments.

Gregorian – Currently used Gregorian – Currently used

Units of TimeUnits of Time Day – 24 hoursDay – 24 hours Week – 7 days – the most scheduling done Week – 7 days – the most scheduling done

in weekly referencesin weekly references Month – 30 or 31 days (exception Month – 30 or 31 days (exception

February)February) Season – 3 months – spring, summer, Season – 3 months – spring, summer,

autumn, winterautumn, winter Year – 12 months or 365 ¼ daysYear – 12 months or 365 ¼ days