Chapter 4 Notes Jessica Brandon

Chapter 4 making sense of the universe understanding motion, energy, and gravity.

4.1 describing motion: examples from everyday life

*****How do we describe motion?******

-precise definitions to describe motion:

-Speed: rate at which objects moves

-Velocity: speed and direction

-Acceleration : any change in velocity units of speed/time.

Acceleration of gravity

-All falling objects accelerate at the same rest ( not counting friction of air resistance)

-On earth speed increases 10 m/s with each second of falling.

- Galileo showed that g is the same for all falling objects, regardless of their mass.

Momentum and force

-Momentum= massX velocity

-A net force changes momentum, which generally means an acceleration (change in velocity)

-The rotational momentum of a spinning or orbiting object is known as angular momentum.

Question: is the net acting on each of the following?

Answer: a car coming to a stop (yes) a elevate moving at a consent speed ( no)

****How is mass different from weight?****

-Mass: the amount of matter in an object

-Weight: the force that acts on an objects

Question: on the moon..

Answer: your weight is less your mass is the same.

Why are astronauts weightless on earth?

-There is gravity in space

-Weightlessness is due to a constant state of free-fall

4.2 newtons laws of motions

*****How did newton change our view of the universe?*****

-Sir Isaac newton he realized the same physical laws that operate on earth also operate I the heavens

-He discovered laws of motion and gravity

-Much more: experiments with light first reflecting telescope, calculus.

*****What are newtons three laws of motions?*****

-Newton's first law of motion: an object moves at constant velocity unless a net force acts to change its speed or direction.

- Newton's second law of motion: force=mass X acceleration.

-Newtons third law of motion: for every force there is always an equal and opposite reaction force.

Question: is the force that earth exerts on you large, smaller, or the same as the force you exert on it?

Answer: earth and you exert equal and opposite force on each other.

4.3 conservation laws in astronomy

*****What keeps a planet rotating and orbiting the sun?***

Conservation of momentum

-The total momentum of interacting objects cannot change unless an external force is acting on them

-Interacting objects exchange momentum through equal and opposite forces.

Conservation of angular Momentum

-The angular momentum of an object cannot change unless an external twisting force (torque)  is acting on it

-Earth experiences no twisting force as it orbits the sun,

****Where do objects get their energy?*****

-Energy makes matter move

-Energy is conserved but it can... Transfer from one object o another. Change in form.

-Types of energy: kinetic(motion) radiative(light) stored of potential

-Energy can change type but cannot be destroyed

-Thermal energy: the collective kinetic energy of many particles for example in a rock, in air, in water.

-Thermal energy is related to tempura true but is not the same as temperature is the average kinetic energy for the particles in a substance must also lead to a higher total energy.

-Thermal energy is a measure of the total kinetic energy of all particles in a substance. It therefore depends on both temperature and density.

Gravitational potential energy

-On earth it depends on... An objects mass, the strength of gravity, the distance an object could potentially fall.

- in space an object or gas cloud has more gravitational energy when it is spread out than when it contracts

-A contracting cloud converts gravitational potential energy to thermal energy.

-Mass energy: mass itself is a form of potential energy e=mc square

-A small amount of mass can release a great deal of energy.

-Concentrated turn into spontaneous turn into particles for example in particles accelerators.

Conservation of energy

Energy can be neither created nor destroyed

It can change form or be exchanges between objects.

****4.4 the force of gravity****

What determines the strength of gravity

The universal law of gravitation.

1. Every ,ass attracts every other mass

2. Attraction is directly proportional to the product of their mass.

3. Attraction is inversely proportional to the square of the distance between their centers.

How does newtons law of gravity extend keplers laws?

-Keplers  first two laws apply to all orbiting objects not just planets

-Ellipses are not the only orbiting path. Orbits can be... Bound (ellipses) unbound: parabola or hyerbola.

-Newtons generalized keplers third law.. Newtons version of keplers third law: if a small object orbits a large one and you measure the orbiting objects orbital period and distance then you can calculate the mass of the large object

Example: calculate the mass of the sun from earth orbital period (1 year).

How do gravity and energy together allow us to understand orbits?

-Total orbital energy (gravitational + kinetic) stays constant if there is no external force

-Orbits cannot change spontaneously

-less gravitational  energy more kinetic energy

Changing an orbit

-So what can make an object gain or lose orbital energy? Friction or atmospheric drag. A gravitational encounter.

Escape velocity

-If an object gains enough orbital energy, it may escape (change from a bound to unbound orbit)

-Escape velocity from earth 11 km/s from sea level (about 40,00 km/hr)

How does gravity cause tides?

-the moons gravity pulls harder on near side of earth than on far side

-the difference on the moon gravitational pull stretches earth

-size of tides depend on the phase of the moon

Tidal friction

-Tidal friction gradually slows earths rotation (and makes the moon get farther from the earth)

-moon once orbited faster ( or slower) tidal friction caused it to lock in synchronous rotation.

Chapter 4 Quiz Jessica Brandon

How do we describe motion?

·      With speed, velocity, and acceleration. Speed equals the distance divide time. To get velocity you do speed plus the direction. Acceleration is the change in velocity. Momentum is also used to describe motion which is mass times velocity. Force causes a change in momentum, which means acceleration.

How is mass different from weight?

·      The difference is mass is equal to the quantity of water and weight is the force acting on mass. Objects are weightless when in free-fall.

How did Newton change our view of the universe?

·      Newton discovered the laws of motion and gravitation. He also realized these same law of physics were identical to the universe and on earth

What are Newton's three laws of motion?

·      Newton’s three laws… His first law was that objects move at a constant velocity if no net force is acting. His second law is that force equals the mass times the acceleration. Newton’s third law was for every force there is an equal and opposite reaction force.

What keeps a planet rotating and orbiting the Sun?

·      What keeps a planet rotating and orbiting the sun is the law of conservation of angular momentum.

Where do objects get their energy?

·      Objects get their energy by conservation of energy. Which is the energy cannot be treated or destroyed it can only be transformed from one type to another. Energy comes in three basic types.

What determines the strength of gravity?

·      Directly proportional to the product of the masses. Inversely proportional to the square of the separation.

How does Newton's law of gravity extend Kepler's laws?

·      His law applies to other objects, not just the planets. His laws include unbound orbit shapes parabola and hyperbola. We can no measure the mass of other systems.

How do gravity and energy allow us to understand orbits?

·      Gravity is what determines the orbits. Orbiting objects cannot change its orbit without energy being transferred.

How does gravity cause tides?

·      What gravity does to the tides is stretches earth along earths-moon line because the near side is pulled harder then the far side.

Chapter 4 Notes: Olivia Ward

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

4.1 Describing Motion: Examples from Everyday Life

How do we describe motion?

• Speed: Rate at which objects move. Speed = distance / time (units of meters / seconds)
• Velocity: Speed and direction
• Acceleration: Any change in velocity; units of speed / time (m / s^2)
• Acceleration of Gravity
  
  • All falling objects accelerate at the same rate (not counting friction in air resistance).
• Acceleration of Gravity (g)
  
  • Galileo showed that g is the same for all falling objects, regardless of their mass.
  • Feather and hammer drop
• Momentum and Force
  
  • Momentum = mass X velocity
  • A net force changes momentum, which generally means an acceleration (change in velocity).
  • The rotational momentum of a spinning or orbiting object is known as angular momentum.
• Question: Is a net fore acting on each of the following?
  
  • A car coming to a stop: Yes
  • A bus speeding up: Yes
  • An elevator moving up at a constant speed: No
  • A bicycle going around a curb: Yes
  • A moon orbiting Jupiter: Yes

How is mass different from weight?

• Mass: The amount of matter in an object
  
•  Weight: The force that acts on an object
• Question: On the Moon...
  
  • A. Your weight is the same; your mass is less.
    B. Your weight is less; your mass is the same.
    C. Your weight is more; your mass is the same.
    D. Your weight is more; your mass is less.

Why are astronauts weightless in space?

• There is gravity in space.
• Weightlessness is due to a constant state of free falling.

4.2 Newton's Law of Motion
How did Newton change our view of the universe?

• He realized the same physical laws that operate in the heavens - one universe.
• He discovered laws of motion and gravity.
• Experiments with light (optics), first reflecting telescope, calculus

What are Newton's three laws of motion?

• First law of motion: An object moves at constant velocity unless a net force acts to change its speed or direction.
• Second law of motion: Force = mass X acceleration
• Third law of motion: For ever force, there is always an equal and opposite reaction force.
• Question: Is the force the Earth exerts on your larger, smaller, or the same as the force you exert on it?
  • A. Earth exerts a larger force on you.
  • B. You exert a larger force on Earth.
  • C.  Earth and you exert equal and opposite forces on each other.

• Question: A compact car and a large truck have a head-on collision. Are the following questions true or false?
  • The force of the car on the truck is equal and opposite to the force of the truck on the car. : True
  • The momentum transferred from the truck to the car is equal and opposite to the momentum transferred from the car to the truck.: True
  • The change of velocity of the car is the same as the change of velocity of the truck.: False

4.3 Conservation of Laws in Astronomy
What keeps a planet rotating and orbiting the Sun?

• Conservation of Momentum
  • The total momentum of interacting objects cannot change unless an external force is acting on them.
  • Interacting objects exchange momentum through equal and opposite forces.

• Conservation of Angular Momentum
  • Angular momentum = mass X velocity X radius
  • The angular momentum of an object cannot change unless an external twisting force (torque) is acting on it.
  • Earth experiences no twisting force

  Where do objects get their energy?

• Energy makes matter move and is conserved, but it can transfer from one object to another
• Basic types of energy:
  
  • Kinetic (motion)
  • Radiative (light)
  • Stored / potential
  • Energy can change type but cannot be destroyed
• Thermal Energy: The collective kinetic energy of many particles
  • Thermal energy is related to temperature but is not the same. Temperature is the average kinetic energy of the many particles in a substance.
  • Thermal energy is a measure of the total kinetic energy of all the particles in a substance. It therefore depends on both temperature and density.
• Gravitational Potential Energy
  • On Earth, gravitational it depends on:
    
    • An object's mass (M)
    • The strength of gravity (g)
    • The distance an object could potentially fall
  • In space, an object or gas cloud has more gravitational energy when it is spread out than when it contracts.
    
    • A contracting cloud converts gravitational potential energy to thermal energy.
• Mass Energy
  
  • A small amount of mass can release a great deal of energy.
  • Concentrated energy can spontaneously turn into particles (particle accelerator).
• Conservation of Energy
  • Energy can be neither created nor destroyed.
  • It can change form or be exchanged between objects.

4.4 The Force of Gravity
What determines the strength of gravity?

• The Universal Law of Gravitation
  
  • Every mass attracts every other mass.
  • Attraction is directly proportional to the product of their masses.
  • Attraction is inversely proportional to the square of the distance between their centers.

How does Newton's law of gravity extend to Kepler's laws?

•  Kepler's first two laws apply to all orbiting objects, not just planets.
• Ellipses are not only orbital paths.
  
  • Bound (ellipses)
  • Parabola
  • Hyperbola
• Third law: If a small object orbits a larger one and you measure the object's orbital period and average the orbital distance, then you can take the mass of the larger object.

How do gravity and energy together allow us to understand orbits?

• Total orbital energy (gravitational kinetic) stays constant if there is no external force.
• Orbits can't change spontaneously.
• Changing an orbit can make an object gain or lose orbital energy:
  
  • Friction or atmospheric drag
  • Gravitational encounter
• Escape velocity
  
  • If an object gains enough orbital energy, it may escape (change from a bound to unbound orbit).
  • Escape velocity from Earth ≈ 11 km/s from sea level

How does gravity cause tides?

• The Moon's gravity pulls harder on the near side of Earth than the far side.
• The difference in the Moon's gravitational pull stretches Earth.
• Tides and Phases
  
  •  Size of tides depends on the phase of the Moon
• Tidal Friction
  
  • Tidal friction gradually slows Earth's rotation (makes the Moon get further from Earth).
  • Moon once orbited faster; tidal friction caused it to lock in synchronous rotation.

Allison Thompson Chapter 4 notes

chapter 4

***How so were describe motion?
-Speed
*rate at which objects move
-Velocity
* speed and direction
-Acceleration
* any change in velocity.
Acceleration
*All falling objects accelerate not counting friction of air resistance

*Galileo showed that g is They same for all falling objects regardless of mass.

*Momentum is mass x velocity

*A net force changes momentum which generally means acceleration (change in velocity)

*They rotational momentum of a spinning or orbiting object known as angular momentum.


thought question

Is net force acting on each of  They following?
1. A car coming to a stop. Yes
2. A bus speeding up. Yes
3. A elevator moving up at a constant speed. No
4. A bicycle going around a curve. Yes
5. A moon orbiting Jupiter. Yes

**How is mass different from weight?
Mass
-the amount if matter in an object
Weight
- The amount of force that acts on an object.
 Thought question
On the moon your weight is less, but your mass is the  same.

Why are astronauts weightless in space?
-There is gravity in space
- Weightlessness is due to constant state of free-fall.




Chapter 4.2

*How did Newton change our view if the universe?
 He realized the same physical laws that operate on Earth also operate in the heaven
He discovered laws of motion and gravity
 Much more: Experiments with light first reflecting telescope calculus....

Newton's laws of motion
1. An object moves at constant velocity unless a net force acts to change its speed or direction.
2.Force = mass x acceleration
3.For every force there is always an equal and opposite reaction force.

though question

Is the force the earth exerts on you larger, smaller, or the smae as the force ypu exerts on it?
 Earth and you exert equal and opposite forces on each other.

A compact car and a large truck have a head-on collision. Are the following questions true or false?
1. The force of the car on the truck is equal and opposite to the force of the truck on the car. True
2. The momentum transferred from the truck to the car is equal and opposite to the momentum transfered from car to truck. True
3. the change of velocity of the car is the same as change of velocity of the truck. False.


Chapter 4.3
 *what keeps a planet rotating and orbiting the sun?
 Conservation of momentum
 Total momentum of interacting objects cannot change unless an external force is acting on them.
 Interacting objects exchange momentum through equal and opposite forces.

*What keeps a planet rotating and orbiting the sun?
angular momentum= mass x velocity x radius
 The angular momentum of an object cannot change unless an external twisting force (torque)

*Where do objects get their energy?
Energy makes matter move.
energy is conserved but I can....
-transfer from one object to another

Kinetic (motion)
Radiative (light)
Stored or potential
**energy can be Stored but not destroyed **

Thermal Energy
*thermal energy is related to temperature but is NOT the same. temperature is the average Kinetic energy of the particles in substances.
*thermal energy is a measure of the Kinetic energy of all the particles in a substance. it therefore depends on both density and temperature.

gravitational potential energy.
 On earth it depends on....
*an objects mass
*strength of gravity
* distance an object could potentially fall.

in space an object or gas cloud has more gravitational energy when it is spread out than when it contracts.
a contracting cloud converts gravitational potential energy to thermal energy.

Mass-Energy
*Mass itself is a form of potential energy.
 a small amount of mass can release a great deal of energy.
concentrated energy can spontaneously turn into particles.

Conservation of energy
*energy can be neither created nor destroyed


chapter 4.4
*What determines the strength of gravity?
The universal law of gravitation
1.every mass attracts every other mass.
2.Attraction is directly proportional to the product of their masses
3.Attraction is inversely proportional to square of the distance between their centers

*Kepler's first two laws applied to all objects not just planets
*ellipses are not only orbital paths. Orbits can be bound or unbound.
*Newton generalized Kepler,s third law
*if  a small object Orbits a large one and you measure the objects.

*How do gravity and energy together allow us to understand Orbits
 Total orbital energy stays constant if there is no external force
orbit cannot spontaneously change

*Friction and atmospheric drag can change orbit. Also gravitational encounters.
*Escape velocity
If an object gains enough orbital energy it may Escape

How does gravity cause tides?
The moon's gravity pulls harder on near side of earth than on far side.
The difference in the moon's gravitational pull stretches earth.

Tides and Phases
-size of tides depends on the phase of the moon
Tidal Friction gradually slows earths rotation
Moon once orbited faster; tidal Friction caused it to lock in synchronous rotation

Beware of Errant Asteroids - NYTimes.com

Beware of Errant Asteroids - NYTimes.com:

"ON Feb. 15, an asteroid designated 2012 DA14 will pass safely within about 17,200 miles of Earth’s surface — closer than the communication satellites that will be broadcasting the news of its arrival. The asteroid is about 150 feet in diameter and has a mass estimated at about 143,000 tons."

'via Blog this'

Chris McGown Notes

Chris McGown Notes

Chris McGown Notes

Chris McGown Notes

Chris McGown Notes

Chris McGown Notes

Chris McGown Notes

Chris McGown Notes

Chris McGown Quiz

Heavy Snow and Winds Batter Northeast - NYTimes.com

Heavy Snow and Winds Batter Northeast - NYTimes.com:

 "A ferocious storm system pummeled the Northeast on Saturday, burying some parts of region in more than two feet of snow and leaving more than 650,000 homes and businesses without power, mostly in New England."

'via Blog this'

Quiz

1. How do we describe motion?
2. How is mass different from weight?
3. How did Newton change our view of the universe?
4. What are Newton's three laws of motion?
5. What keeps a planet rotating and orbiting the Sun?
6. Where do objects get their energy?
7. What determines the strength of gravity?
8. How does Newton's law of gravity extend Kepler's laws?
9. How do gravity and energy allow us to understand orbits?
10. How does gravity cause tides?

Big Storm and Its Disruptions Descend on the Northeast - NYTimes.com

Big Storm and Its Disruptions Descend on the Northeast - NYTimes.com:

"A mammoth winter storm descended on the Northeast Friday night, bringing with it whipping winds and snowfall that forecasters said could set records in many places."

"South of Interstate 78 and along the Jersey Shore, where the hurricane hit hardest, there was only rain Friday morning. But seas were rough, and forecasters warned that there could be coastal flooding at high tide, scheduled to hit around 6 p.m. Friday."

'via Blog this'

Chapter 3 Quiz Jessica Horn

1. How did Copernicus, Tycho, and Kepler challenge the Earth centered model?

• Copernicus created a Sun-centered model of the solar system
• This model was designed to replace the Ptolemaic model
• Unfortunately, this model was no more accurate than Ptolemy's because Copernicus still used perfect circles
• Tycho's accurate, naked-eye observations provided needed data
• This needed data improved on Copernicus's model
• Kepler developed a model of planetary motion that fit Tycho's data 

  

2.What are Kepler's three laws of planetary motion?

1. Kepler's first law: The orbit of each planet around the Sun is an ellipse with the Sun at one focus.
2.  Kepler's second law: As a planet moves around its orbit, it sweeps out equal areas in equal times. This means that the planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun. 
3. Kepler's third law: More distant planets orbit the Sun slower averages speeds, obeying the relationship.

3.How did Galileo solidify the Copernican revolution?

• Galileo's experiments and telescopic observations overcame remaining objections to the Copernican idea of Earth orbiting the Sun
• Although these results were not immediately accepted, Galileo's findings sealed the case for the Sun centering the solar system

4.How can we distinguish science from nonscience?

     

•  Defining science can be surprisingly difficult. Science, in Latin, means "knowledge." But not all knowledge comes from science. The idealized scientific method is based on proposing and testing a hypothesis, or an educated guess. But science rarely proceeds in this idealized way. For example: sometimes we start by "just looking" then coming up with possible explanations. Sometimes we follow intuition rather than a particular line of evidence. Hallmarks of Science #1: Modern science seeks explanations for observed phenomena that rely solely on natural causes (A scientific model cannot include dive intervention). Hallmarks of Science #2: Science progresses through creation and testing of models of nature that explain the observations as simply as possible (simplicity = "occam's razor). Hallmarks of Science #3: A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations.  

 5.What is a scientific theory?

•   The word "theory" has a different meaning in science than in everyday life. In science, a theory is NOT the same as a hypothesis. A scientific theory must: explain a variety of observations with a few simple principles  be supported by large, compelling body of evidence, NOT have failed any crucial test of its validity. Darwin's Theory of evolution meets all the criteria of scientific theory. This means after more than 100 years of testing, Darwin's theory stands stronger than ever, having successfully met every scientific challenge to its validity. 

6.What does the universe look like from Earth?

• As stars and other celestial objects appear to lie on a great celestial sphere that surrounds Earth, this sphere is divided constellations with well defined borders
• From any location on Earth, human s see half of the celestial sphere that appears to be the dome of our local sky
• In which, the horizon is the boundary between Earth and the sky
• The zenith is the point directly overhead
• The meridian runs from due south to due north through the zenith

   

7. Why was planetary motion so hard to explain?

• Because of apparent retrograde motion
• This motion occurs when Earth passes by or is passed by another planet in its orbit
• But it posed a major mystery to ancient people who assumed Earth to be the center of the universe

8.Why did the ancient Greeks reject the real explanation for planetary motion?

•  They rejected the idea that Earth goes around the sun because they could not detect the stellar parallax
• To most Greeks, it seemed unlikely that the stars could be so far away as to make parallax undetectable to the naked eye
• Even though that is the case

9.In what ways do all humans use scientific thinking?

• As demonstrated in an organized manner, humans use scientific thinking in their everyday lives.
• Scientific thinking relies on the same type of trial-and-error techniques that are used in everyday situations

10.How did astronomical observations benefit ancient societies?

• Ancient societies used astronomical observations to keep track of time and seasons, which provided the crucial skills for people who depended on agriculture for survival
• Astronomical observations also aided in navigation

Sources: Textbook and Notes

Chapter 3 Quiz: Olivia Ward

1. How did Copernicus, Tycho, and Kepler challenge the Earth centered model?

Copernicus proposed the Sun-centered model and used the model to determine the layout of the solar system. The model used circular orbits. Tycho compiled the most accurate measurements of the planet positions but still thought the Earth was the center of the solar system but recognized that the other planets go around the Sun. Kepler discovered that planets do not have circular orbits, and instead of ellipse shaped orbits.

2. What are Kepler's three laws of planetary motion?

The first law is that the orbit of each planet around the Sun is an ellipse instead of the originally thought of circular orbit. The Sun is a focus of the ellipse. The second law is as a planet moves around its orbit, it sweeps out equal areas in equal times. A planet travels faster when it's closer to the Sun and slower when it's farther away.

3. How did Galileo solidify the Copernican revolution?

Galileo overcame three major issues of the Copernican view. His experiments proved that objects in air would stay moving with Earth and that they will stay in motion until a force acts to slow them down. He saw spots on the Sun as well as mountains and valleys on the Moon, which disproved the idea of heavenly perfection. It was also proven that the stars were further than originally thought and that not all objects orbit Earth.

4. How can we distinguish science from non-science?

 Not all knowledge comes from science. Science is based on the proposition and testing of a hypothesis which observes natural causes. Scientific experiments can only progress from the creation and testing of models. The hypothesis cannot be based on the supernatural.

5. What is scientific theory?

A scientific theory must explain a wide variety of observations, be supported by a largely compelling body of evidence, and not fail any tests of validity.

6. What does the universe look like from Earth?

 From Earth, we can see half of the celestial sphere which allows us to see different parts of the universe. The universe has over 2,000 stars and 88 constellations which can be seen at different times of the year.

7. Why was planetary motion so hard to explain?

Planetary motion was so hard to explain because of retrograde, which means the planets are moving backwards. Planets typically move eastward but occasionally move westward.

8. Why did the ancient Greeks reject the real explanation of planetary motion?
   
   The ancient Greeks rejected the real explanation of planetary motion because they believed that the Earth was the center of the universe and that the heavens were perfect, which only allowed objects to travel in perfect circles.
   
   
9. In what ways do all humans use scientific thinking?

All humans use scientific thinking in their day to day observations and do simple trial-and-error experiments to develop upon these observations. Scientific observations unintentionally begin at a young age, especially for children observing the force of gravity.

10. How did astronomical observations benefit ancient societies?
    
    Ancient societies were able to keep track of time throughout the day as well as the seasons which allowed for agricultural practices and religious events that accompanied a particular season to take place. Navigation was also highly based on the stars.

Chapter 3 Notes: Olivia Ward

The Science of Astronomy

3.1 The Ancient Roots of Science

In what ways do all humans employ scientific thinking?

• Scientific thinking is based on everyday ideas of observation and trial-and-error experiments.

How did astronomical observations benefit ancient societies?

• In keeping track of time and seasons
  
  • For practical purposes, including agriculture
  • For religious purposes
•  In aiding navigation
• Ancient people of central Africa (6500 BC) could predict seasons from the orientation of the crescent moon: Dry seasons / wet seasons based on angle of moon
• Days of the week named for visible planets in English, French, and Spanish

What did ancient civilizations achieve in astronomy?

• Daily time keeping
• Tracking the seasons and calendar
• Monitoring lunar cycles
• Monitoring planets and stars
• Predicting eclipses
• Egyptian Obelisk: Shadows tell time of day
• England: Stonehenge (completed around 1550 BC)
• Mexico: Templo Mayor
• New Mexico: Anasazi kiva aligned north-south
• Southwestern United States: "sun dagger" marks summer solstice
• Scotland: 4000 years old- stone circle; Moon rises here every 18.6 years
• Peru: Lines and patterns, some aligned with stars
• Machu Picchu: Structures aligned with solstices
• Southern Pacific: Polynesians were very skilled in the art of celestial navigation.
• France: Cave paintings from 18,000 BC may suggest knowledge of lunar phases (29 dots).
• China: Earliest known records of supernova explosions (1400 BC): Tortoiseshell inscription

3.2 Ancient Greek Science
Why does modern science trace its roots to the Greeks?

• Our mathematical / scientific heritage originates with civilizations of the Middle East.
• Greeks were the first people to know to make models of nature.
• They tried to explain patterns in nature without resorting to myth or the supernatural.
• The Greek Geocentric model (400 BC)
• Eratosthenes measures the Earth (240 BC)

How did the Greeks explain planetary motion?

• Underpinnings of the Greek Geocentric model:
  
  • Earth at the center of the universe
  • Heavens must be perfect: objects move on perfect circles
• Plato and Aristotle
• This Geocentric model made it difficult to explain the retrograde motion of planets.
  
  • Over 10 weeks, Mars appeared to stop, back up, then go forward again.
• The most sophisticated Geocentric model was from Ptolemy:
  
  • Sufficiently accurate to remain in use for 1500 years.
  • Arabic translation of Ptolemy's work named Almagest (the greatest compilation)
  •  The planets nearly do go backward in this model.

• Question: Which of the following is not a fundamental difference between the Geocentric model and the Sun-centered model of our solar system?
  
  • A: Earth is stationary in the Geocentric model but moves around the Sun in the Sun-centered model.
  • B: Retrograde motion is real in the Geocentric model but only apparent in the Sun-centered model.
  • C: Stellar parallax is expected in the Sun-centered model but not in the Earth-centered model.
  •  D: The Geocentric model is useless for predicting planetary positions, whereas even the earliest Sun-centered models worked almost perfectly.
    

How did Islamic scientists 'preserve' and extend Greek science?

•  The Muslim world enhanced the knowledge they received from the Greeks while Europe was in the Dark Ages.
• House of Wisdom in Baghdad was a great center of learning around 800 AD.
• With the fall of Constantinople in 1453, Eastern scholars headed to Europe bringing their knowledge which helped to ignite the European Renaissance.

3.3 The Copernican Revolution
How did Copernicus, Tycho, and Kepler challenge the Earth-centered idea?

• Copernicus (1473-1543)
  • Proposed the Sun-centered model
  • Used the model to determine the layout of the solar system (planetary distances in AU)
  • The model was no more accurate than the Ptolemaic model in predicting planetary positions because it still used perfect circles.

• Tycho Brahe (1546-1601)
  • Compiled the most accurate naked eye measurements ever made of planetary positions (1 arcminute)
  • He could not detect stellar parallax, thus still thought Earth was the center of the solar system but recognized the other planets go around the Sun.
  • He hired Kepler, who used Tycho's observations to discover the truth about planetary motion 
•  Johannes Kepler (1571-1603)
  
  • First tried to match Tycho's observations with circular orbits.
  • An 8 arcminute error led him to ellipses: "A complete reformation in astronomy"

What are Kepler's three laws of planetary motion?

• First law: The orbit of each planet around the Sun is an ellipse with the Sun at one focus.
• Second law: As a planet moves around its orbit, it sweeps out equal areas in equal times. A planet travels faster when it is nearer to the Sun and slower when it is farther away from the Sun.
• Third law: More distant planets orbit the Sun at slower average speeds, obeying the relationship: p^2 = a^3
  • p = orbital period in years
  • a = average distance from Sun in AU
• Question: An asteroid orbits the Sun at an average distance of 4 AU. How long doe sit take to orbit the Sun?
  
  • A: 4 years
  • B: 8 years
  • C: 16 years
  • D: 64 years

How did Galileo solidify the Copernican revolution?

• He overcame major objections to the Copernican view. Three key objections rooted in the Aristotelian view:
  
  • Earth could not be moving because objects in the air would be left behind.
  • Non-circular orbits are not perfect as the heavens should be.
  • If Earth were really orbiting the Sun, we'd detect stellar parallax.
• Overcoming the first objection (nature of motion)
  
  • Galileo's experiments showed that objects in air would stay moving with Earth.
  • Aristotle thought that all objects naturally came to rest.
  • Galileo showed that objects will stay in motion unless a force acts to slow them down (Newton's first law of motion).
• Overcoming the second objection (heavenly perfection)
  
  • Tycho's observations of comet and supernova already challenged this idea.
  • Using his telescope, Galileo saw sunspots on the Sun, mountains and valleys on the Moon (imperfections)
• Overcoming the third objection (parallax)
  
  • Tycho thought he had measured stellar distances, so lack of parallax seemed to rule out an orbiting Earth.
  • Galileo showed stars must be further than Tycho thought - in part by using his telescope to see the Milky Way.
  • If stars were much farther away, then lack of detectable parallax was no longer so troubling.
  • Galileo also saw four moons orbiting Jupiter, proving that not all objects orbit Earth.
  • His observations of phases of Venus proved that it orbits the Sun and not Earth.
• Galileo Galilei
  
  • 1633: The Catholic Church ordered him to recant his claim that Earth orbits the Sun.
  • His books were removed from the Church's index of banned books in 1824.
  • 1992: He was formally vindicated by the Church.

3.4 The Nature of Science
How can we distinguish science from non-science?

• 'Science' comes from Latin 'scientia' meaning knowledge.
• The idealized scientific method - based on proposing and testing hypothesis
• Hallmarks of science #1: Modern science seeks explanations for observed phenomena that rely on natural causes. (A scientific model cannot include divine intervention.)
• #2: Science progresses through the creation and testing of models of nature that explain the observations as simply as possible.
• #3: A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations

What is a scientific theory?

•  In science, a theory is not the same as a hypothesis.
• A scientific theory must:
  
  • Explain a wide variety of observations with few simple principles
  • Be supported be a large, compelling body of evidence
  • Not fail any crucial tests of validity
• Question: Darwin's theory of evolution meets all of the criteria of a scientific theory. This means:
  
  • A: Scientific opinion is about evenly split as to whether evolution really happened.
  • B: Scientific opinions run about 90% in favor of the theory of evolution and about 10% is opposed.
  • C: After more than 100 years of testing, Darwin's theory stands stronger than ever, having met every scientific challenge of validity.
  • D: There is no longer any doubts about the validity of Darwin's theory.

Chapter 3 Quiz Jessica Brandon

Astronomy Quiz #2

1.    How did Copernicus, Tycho, and Kepler challenge the Earth centered model?

Copernicus used the model to determine the layout of the solar system planetary distance in AU. The model was no more accurate than the Ptolemaic model in predicting planetary position because it still used perfect circles.

Tycho he compiled the most accurate naked eye measurement ever made of planetary position. He still could not detect stellar parallax and thus still thought earth must be the center of the solar system but recognized that other planets go around the sun he then hired kepler.

Keples first tried to match tychos observation with circular orbits, but an 8-arcmintue discrepancy led him eventually to ellipses

2.    What are Kepler's three laws of planetary motion?

First law: the orbit of each planet around the sun is an ellipse with the sun at one focus

Second law: as a planet moves around it orbit it sweeps out equal times

This means that a planet travels faster when it is nearer to the sun and slower when it is farther from the sun.

Third law: more distant planets orbit the sum at slower average speeds obeying the relationship

3.    How did Galileo solidify the Copernican revolution?

overcame major objections to Copernican view. Three key objections rooted in Aristotelian view were: 1. Earth could not be moving because objects in air would be left behind. 2. Non-circular orbits are not “perfect” as heavens should be. 3. If Earth were really orbiting Sun, we’d detect stellar parallax.

4.    How can we distinguish science from nonscience?

Not all knowledge comes from science. The idealized scientific method based on proposing and testing hypotheses. Hypothesis= educated guess

But science rarely proceeds in this idealized way for example...

Sometimes we start by just looking then coming up with possible explanation

Sometimes we follow our intuition rather than a particular line of evidence.

5.    What is a scientific theory?

The word theory has a different meaning in science than in everyday life. In

science a theory is NOT the same as a hypothesis. The scientific method must

explain a wide variety of observation with a simple principles that is

supported by a large compelling body of evidence

6.    What does the universe look like from Earth?

With the naked eye, we can see more than 2,000 stars as well as the milky-way, a faint band of lights encircling the celestial sphere which is the sky.

7.    Why was planetary motion so hard to explain?

Planets usually move slightly eastward from night to night relative to the stars, but sometimes they go westward relative to the stars for a few weeks. We see apparent retrograde motion when we pass by a planet in its orbit.

8.    Why did the ancient Greeks reject the real explanation for planetary motion?

Most Greeks concluded that earth must be stationary, because they thought the stars could not be so far away as to make parllax undetectable.

9.    In what ways do all humans use scientific thinking?

Scientific thinking involves the same type of trial and error thinking that we use in our everyday live, but in carefully organized way.

10. How did astronomical observations benefit ancient societies?

Keeping track of time and seasons. For practical purposes, including agriculture. For religious and ceremonial purposes.