Astronomy Astronomy

In the beginning In the beginning

Pre-test Pre-test

True or False:True or False: 1) Greek Astronomers (600BC-150AD) 1) Greek Astronomers (600BC-150AD)

used telescopes to observe stars. used telescopes to observe stars. Answer: False Answer: False 2) What lies at the center of our solar 2) What lies at the center of our solar

system? system? A) sun A) sun B) Mars B) Mars C) Earth C) Earth D) the moonD) the moon Answer: AAnswer: A

Pre-test Pre-test

What is a rotation?What is a rotation?A) movement around an object A) movement around an object B) turning and spinning of a body on it’s B) turning and spinning of a body on it’s

axisaxisC) The wobble of a body on it’s axisC) The wobble of a body on it’s axisD) WTBW…these are all correctD) WTBW…these are all correctAnswer: BAnswer: B

Pre-test Pre-test

What is the approx. rotational period of the What is the approx. rotational period of the Earth?Earth?

A) 24hrs B) 12hrs C) 30days D) 365daysA) 24hrs B) 12hrs C) 30days D) 365daysAnswer: AAnswer: AApprox. how long does it take for the Approx. how long does it take for the

moon to go through all of it’s phases?moon to go through all of it’s phases?A) 24hrs B) 12hrs C) 30days D) 365daysA) 24hrs B) 12hrs C) 30days D) 365daysAnswer: C Answer: C

WTBWWTBW

How old is the Universe?How old is the Universe?How many stars are in the Universe?How many stars are in the Universe?What ancient civilizations contributed to What ancient civilizations contributed to

astronomy?astronomy?

History of AstronomyHistory of Astronomy 66

IntroductionIntroductionWestern astronomy divides into 4 periodsWestern astronomy divides into 4 periods

Prehistoric (before 500 Prehistoric (before 500 B.C.B.C.))Cyclical motions of Sun, Moon and stars observedCyclical motions of Sun, Moon and stars observedKeeping time and determining directions developsKeeping time and determining directions develops

Classical (500 Classical (500 B.C.B.C. to to A.D.A.D. 1400) 1400)Measurements of the heavensMeasurements of the heavensGeometry and models to explain motionsGeometry and models to explain motions

Renaissance (1400 to 1650)Renaissance (1400 to 1650)Accumulation of data lead to better modelsAccumulation of data lead to better modelsTechnology (the telescope) enters pictureTechnology (the telescope) enters picture

Modern (1650 to present)Modern (1650 to present)Physical laws and mathematical techniquesPhysical laws and mathematical techniquesTechnological advances accelerateTechnological advances accelerate

History of AstronomyHistory of Astronomy 77

Prehistoric AstronomyPrehistoric Astronomy In summary, basis of prehistoric In summary, basis of prehistoric

astronomy:astronomy:Rising and setting of Sun, Moon, and starsRising and setting of Sun, Moon, and starsConstellationsConstellationsAnnual motion of SunAnnual motion of SunMotion of planets through zodiacMotion of planets through zodiacPhases of the MoonPhases of the MoonEclipsesEclipses

The Roots of AstronomyThe Roots of Astronomy

• Already in the stone (4500-2000BC) and bronze ages (3600-1700BC), human cultures realized the cyclic nature of motions in the sky.

• Evident in hieroglyphics and cuneiforms

• Monuments dating back to ~ 3000 B.C. show alignments with astronomical significance.

• Those monuments were probably used as calendars or even to predict eclipses.

Great Pyramids ~2589-2504BC

StonehengeStonehenge

• Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices

• Probably used as calendar.

Summer solstice

Heelstone

• Constructed: 3000 – 1800 B.C.

Other Examples All Over the WorldOther Examples All Over the World

Big Horn Medicine Wheel (Wyoming)

Other Examples All Over the World (2)Other Examples All Over the World (2)

Caracol (Maya culture, approx. A.D. 1000)

Ancient Greek AstronomersAncient Greek Astronomers

• Unfortunately, there are no written documents about the significance of stone and bronze age monuments.

• First preserved written documents about ancient astronomy are from ancient Greek philosophy.

• Greeks tried to understand the motions of the sky and describe them in terms of mathematical (not physical!) models.

Ancient Greek Astronomers Ancient Greek Astronomers

Models were generally wrong because they were based on wrong “first principles”, believed to be “obvious” and not questioned:

1. Geocentric Universe: Earth at the Center of the Universe.

2. “Perfect Heavens”: Motions of all celestial bodies described by motions involving objects of “perfect” shape, i.e., spheres or circles.

History of AstronomyHistory of Astronomy 1717

Early Ideas of the HeavensEarly Ideas of the HeavensAncient Greek AstronomersAncient Greek Astronomers

Through the use of models and observations, Through the use of models and observations, they were the first to use a careful and they were the first to use a careful and systematic manner to explain the workings of systematic manner to explain the workings of the heavensthe heavens

Limited to naked-eye observations, their idea Limited to naked-eye observations, their idea of using logic and mathematics as tools for of using logic and mathematics as tools for investigating nature is still with us todayinvestigating nature is still with us today

Their investigative methodology is in many Their investigative methodology is in many ways as important as the discoveries ways as important as the discoveries themselvesthemselves

Eratosthenes (~ 200 B.C.):Eratosthenes (~ 200 B.C.):Calculation of the Earth’s radiusCalculation of the Earth’s radius

Angular distance between Syene and Alexandria:

~ 70

Linear distance between Syene and Alexandria:

~ 5,000 stadia

Earth Radius ~ 40,000 stadia (probably ~ 14 % too large) – better than

any previous radius estimate.

A value of 25,000 mi. for A value of 25,000 mi. for the circumferencethe circumference

History of AstronomyHistory of Astronomy 1919

Early Ideas of the HeavensEarly Ideas of the HeavensThe Shape of the EarthThe Shape of the Earth

Pythagoras taught as early as 500 Pythagoras taught as early as 500 B.C.B.C. that that the Earth was round, based on the belief that the Earth was round, based on the belief that the sphere is the perfect shape used by the the sphere is the perfect shape used by the godsgods

By 300 By 300 B.C.B.C., Aristotle presented naked-eye , Aristotle presented naked-eye observations for the Earth’s spherical shape:observations for the Earth’s spherical shape:Shape of Earth’s shadow on the Moon during an Shape of Earth’s shadow on the Moon during an

eclipseeclipseA traveler moving south will see stars previously A traveler moving south will see stars previously

hidden by the southern horizonhidden by the southern horizon

History of AstronomyHistory of Astronomy 2020

Early Ideas of the HeavensEarly Ideas of the Heavens Distance and Size of the Sun and MoonDistance and Size of the Sun and Moon

The sizes and distances of the Sun and Moon The sizes and distances of the Sun and Moon relativerelative to Earth were determined by Aristarchus to Earth were determined by Aristarchus about 75 years before Eratosthenes measured the about 75 years before Eratosthenes measured the Earth’s sizeEarth’s size

These These relativerelative sizes were based on the sizes were based on the angular angular sizesize of objects and a simple geometry formula of objects and a simple geometry formula relating the object’s diameter, its angular size, and relating the object’s diameter, its angular size, and its distanceits distance

Aristarchus realizing the Sun was very large Aristarchus realizing the Sun was very large proposed the Sun as center of the Solar System, proposed the Sun as center of the Solar System, but the lack of but the lack of parallaxparallax argued against such a argued against such a modelmodel

Once the actual size of the Earth was determined, Once the actual size of the Earth was determined, the the absoluteabsolute sizes and distances of the Sun and sizes and distances of the Sun and Moon could be determinedMoon could be determined

Presentations Presentations Sing itSing it Take a current song or Broadway number Take a current song or Broadway number change the lyrics to fit your topicchange the lyrics to fit your topicWrite itWrite it Create a literary piece, a series of sonnets or Create a literary piece, a series of sonnets or ballad that reflects your topicballad that reflects your topicPaint itPaint it Take your topic and create a masterpiece Take your topic and create a masterpiece that represents all components of your topic that represents all components of your topic Dance itDance it Interpretive dance that leaves no question Interpretive dance that leaves no question about the interaction in your topic.about the interaction in your topic.Kid BookKid Book Create a children’s book that tells the story Create a children’s book that tells the story of your topic through illustrations and word. of your topic through illustrations and word. Old Reliable/New Reliable)Old Reliable/New Reliable) Tri-fold poster/power Tri-fold poster/power point. point.

Renissance Astronomy…Renissance Astronomy…Group Project Group Project

So what is up There…up there, So what is up There…up there, down there, over there?down there, over there?

Where are we?Where are we?How many stars are out there?How many stars are out there?How many planets are there…really?How many planets are there…really?How can we see black holes?How can we see black holes? Is there anything else out there?Is there anything else out there? Is there really a “Global Killer”Is there really a “Global Killer”

YOU ARE HERE.

A sound that was never heardA sound that was never heard

The Big Bang Model is a broadly accepted The Big Bang Model is a broadly accepted theory for the origin and evolution of our for the origin and evolution of our universe.universe.

It postulates that 15 billion years ago, the It postulates that 15 billion years ago, the portion of the universe we can see today was portion of the universe we can see today was only a few millimeters across only a few millimeters across Singularity Singularity

It has since expanded from this hot dense state It has since expanded from this hot dense state into the vast and much cooler cosmos we into the vast and much cooler cosmos we currently inhabit. currently inhabit.

WTBWWTBW

What is the name of the widely accepted What is the name of the widely accepted theory about the start of the universe?theory about the start of the universe?

What is the name of the point at which What is the name of the point at which everything started?everything started?

What ancient civilizations contributed to What ancient civilizations contributed to modern astronomy?modern astronomy?

History of the Big BangHistory of the Big Bang

In 1927, the Belgian priest Georges Lemaître In 1927, the Belgian priest Georges Lemaître was the first to propose that the universe began was the first to propose that the universe began with the explosion of a primeval atom. with the explosion of a primeval atom.

His proposal came after observing the red shift His proposal came after observing the red shift in distant nebulas by astronomers to a model of in distant nebulas by astronomers to a model of the universe based on relativity. the universe based on relativity.

Years later, Edwin Hubble found experimental Years later, Edwin Hubble found experimental evidence to help justify Lemaître's theory. He evidence to help justify Lemaître's theory. He found that distant galaxies in every direction are found that distant galaxies in every direction are going away from us with speeds proportional to going away from us with speeds proportional to their distance. their distance.

History Continued History Continued

We can see remnants of this hot dense matter We can see remnants of this hot dense matter as the now very cold cosmic microwave as the now very cold cosmic microwave background radiation (with high powered background radiation (with high powered telescopes) which still pervades the universe telescopes) which still pervades the universe and is visible to microwave detectors as a and is visible to microwave detectors as a uniform glow across the entire sky. uniform glow across the entire sky.

Although the Big Bang Theory is widely Although the Big Bang Theory is widely accepted, it probably will never be proved; accepted, it probably will never be proved; consequentially, leaving a number of tough, consequentially, leaving a number of tough, unanswered questions. unanswered questions.

General Theory of RelativityGeneral Theory of Relativity

The first key idea dates back to 1916 when The first key idea dates back to 1916 when Einstein developed his General Theory of Einstein developed his General Theory of Relativity which he proposed as a new theory of Relativity which he proposed as a new theory of gravitygravity. .

His theory His theory generalizesgeneralizes Isaac Newton's original Isaac Newton's original theory of gravity, c. 1680, in that it is supposed theory of gravity, c. 1680, in that it is supposed to be valid for bodies in motion as well as bodies to be valid for bodies in motion as well as bodies at rest. at rest.

Newton's gravity is only valid for bodies at rest Newton's gravity is only valid for bodies at rest or moving very slowly compared to the speed of or moving very slowly compared to the speed of light (usually not too restrictive an assumption!). light (usually not too restrictive an assumption!).

RelativityRelativity A key concept of General Relativity is that A key concept of General Relativity is that

gravity is no longer described by a gravitational gravity is no longer described by a gravitational "field" but rather it is supposed to be a distortion "field" but rather it is supposed to be a distortion of space and time itself. of space and time itself.

Physicist John Wheeler put it well when he said Physicist John Wheeler put it well when he said "Matter tells space how to curve, and space tells "Matter tells space how to curve, and space tells matter how to move." matter how to move."

Originally, the theory was able to account for Originally, the theory was able to account for peculiarities in the orbit of Mercury and the peculiarities in the orbit of Mercury and the bending of light by the Sun, both unexplained in bending of light by the Sun, both unexplained in Isaac Newton's theory of gravity. In recent years, Isaac Newton's theory of gravity. In recent years, the theory has passed a series of rigorous tests. the theory has passed a series of rigorous tests.

WTBWWTBW

Who is responsible for the Theory of Who is responsible for the Theory of Relativity?Relativity?

How is gravity explained in the Theory of How is gravity explained in the Theory of Relativity?Relativity?

What did the theory of relativity explain?What did the theory of relativity explain?What is the distance between the Sun and What is the distance between the Sun and

Earth?Earth?

The UniverseThe Universe

The Universe is made up of millions of galaxies. The Universe is made up of millions of galaxies. Also out in space is background radiation from Also out in space is background radiation from all the explosions and nuclear fusion going on all the explosions and nuclear fusion going on within stars and nebulae. within stars and nebulae.

The universe has a whole lot of empty space. In The universe has a whole lot of empty space. In fact, there is so much space even between fact, there is so much space even between single stars in a galaxy that it is difficult to single stars in a galaxy that it is difficult to measure in miles or kilometers. measure in miles or kilometers.

Space DistanceSpace Distance Scientists use a distance measurement in space that is Scientists use a distance measurement in space that is

expressed as the distance light will travel in the course of expressed as the distance light will travel in the course of a year a year

a light year. a light year. Light travels at a speed of about 186,000 miles per Light travels at a speed of about 186,000 miles per

second. second. That means that light can travel 7.5 times around the entire That means that light can travel 7.5 times around the entire

world in just 1 second!world in just 1 second! In a year's time, light can travel six trillion miles In a year's time, light can travel six trillion miles

(6,000,000,000,000). (6,000,000,000,000). It takes over 4 years for the light from the nearest star to reach It takes over 4 years for the light from the nearest star to reach

the Earth (Proxima Centuri)the Earth (Proxima Centuri)