Ch 2 The Ordered Universe

• Classwork Notes • Keep until due date• Must be in order

• Must have title page with contents list

The Night Sky

1. Why do planets seem to wander in the night sky?

Orbit the sun. we are the 3rd planet therefore 5 planets are outside of our orbit.Retrograde motion

Night Sky

2. North starWabbling causes precession north star changes over time

Night Sky

3 StonehengeCircle 0f sarsen stone 20 miles away from the hills, 50

tons 1 ton = 2000 lb 50 tons = 100,000lb1lb = 454 g = .5kg 50 tons = 105 lb = 5 x 10 4 kg = 5 x 107 g

Night Sky

4 Spread of disease Swin flu! It’s the common cold on steroids. Ticks!

Mosquito! Fleas!Ancient AstronautsDo you think “People” aliens built the Pyramids? If

so or not describe an exp. To prove it.

Topic: The Birth of Modern Astronomy

Objective: Notes on 4 major people who influenced the belief of the solar system

Standard: Physics Motion/Newton1. Relative position v. Actual of stars (fixed background2. What causes the streaky motion of meteors and

others?3. Ptolemy and Copernicus4. Brahe and Kepler5. Elliptical and the other’s

The Birth of Modern Astronomy

1. Relative position v. Actual position of stars (fixed background

Stellar Aberration

The aberration of starlight was discovered in 1727 by the astronomer James Bradley while he was searching for evidence of stellar parallax, which in principle ought to be observable if the Copernican theory of the solar system

1.

• The observed displacement was greatest for stars in the direction perpendicular to the orbital plane of the Earth

The Birth of Modern Astronomy

Apparent Displacement of Stars• Newton's days, astronomers have tried to

find how far the stars were by the parallax method,

• using the diameter of the Earth's orbit as a baseline.

The Birth of Modern Astronomy

• …measure the positions of stars at times half a year apart

• Representing two positions of the Earth separated by 300,000,000 km

• check whether the positions of stars in the sky changed.

• Indeed, the positions did change. The trouble …observations did not make much

sense!

The Birth of Modern Astronomy

• Jean Picard, French astronomers, • made possible precise observations • “crosshairs in the telescope eyepiece”• In 1680, the observed positions of stars were not always the

same. • John Flamsteed, the astronomer royal of Britain--head of

the Royal Observatory in Greenwich--confirmed those shifts.

• Polaris, the pole star, seemed to travel annually around an ellipse whose width was 40",

40 seconds of arc.

The Birth of Modern Astronomy

2. What causes the streaky motion of meteors and others?

"shooting star," glowing trail, celestial debris entering our atmosphere. Meteors things in space, meteorite in our atm. Meteoroid on the ground

The Birth of Modern Astronomy

The Birth of Modern Astronomy

3. Ptolemy and CopernicusPtolemy propounded the geocentric theory in a

form that prevailed for 1400 years. observations -Alexandria in Egypt AD 127-41.Pty -by 'Theon the mathematicianTheon of Smyrna

The Birth of Modern Astronomy

3. Copernicus• 1473-1543 Copernicus is said to be the

founder of modern astronomy. • He made his celestial observations from a

turret situated on the protective wall around the cathedral, observations were made "bare eyeball," De Revolutionibus, the earth rotated on its axis and around the sun

The Birth of Modern Astronomy

4. Brahe and Kepler

• Brahe never really accepted the Copernician , • The five known planets circled the Sun• Brahe's theory of planetary motion was incorrect

Johannes Kepler, used the data that he collected about the stars in developing the correct description of planetary motion.

The Birth of Modern Astronomy

5. Elliptical and the other’s

The Birth of Mechanics

Left hand side 1. Mechanics2. Galileo Galilei3. Speed, Velocity, Acceleration4. G-force

The Birth of Mechanics

1. MechanicsThe motion of objects,Speed 65 mphVelocity 65 mph EastAcceleration 2 mph2 westForce 6.5 N does need a directionMomentum 600 lb mi/h

The Birth of Mechanics

2. Galileo GalileiItalianPhysicist late 16th centuryTelescope, jupiters moons reasoning for Elliptical orbitsEllipse have “two centers” Focus , foci

The Birth of Mechanics

3. Speed, velocity, accelerationSpeed = distance / Time units m/sVelocity = displacement / time What is the difference between distance and

displacement? Acceleration = Velocity / time

= displacement/ time2

The Birth of Mechanics

4. G-force Gravitational force need mass to apply G = g =

Newton’s Laws

1. First law- constant unless force applied2. Second Law- F= ma units kg m/s2

3. Third Law- F12 =-F21

4. Laws at work shuttle launch – 17,000 km/hr

Momentum

1. P = mv2. Conservation of linear momentum3. Angular momentum4. Inertial guidance systems

1. p = mv

p = momentum units kg m/s or Ns

Mass = kgVelocity or speed both v = 1 x 10-15 m/sp = 102 Ns

P/v = m = 102 Ns / 1 x 10-15 m/s102-(-15) = 10 17 kg

2. Conservation of linear momentum

• Linear = line linear momentum in 2-dimensionsp= # x + #y Steps 5 m north then steps 2 m east

5m x + 2m y = DV = D/t t= 3 s V= 5m/3s x + 2m / 3s y m= 3 kg P= mv =3 kg {5m/3s x + 2m / 3s y} P= 5kgm/s x + 2kgm/s y

3. Angular momentum

• p= #cos θ x + #sin θ y • Momentum has some curve • Constant momentum occurs when angle

doesn’t change

4. Inertial guidance systems

• Gyroscope, …. Segway• Keeps the object from falling over• The gyroscope spins to keep it up right• There are three circles spinning for the 3

dimensions

Universal Force of Gravity

1. Gravitational constant G2. Weight v mass3. G v g

1. Gravitational constant G

Bottom p. 52 Equation Form Also Symbolic formForce on object (Netwon) =

= G (Nm2/kg2) m1 m2/ D2

10-11 = .0000000001

2. Weight v mass

Weight = changesMass = sameW = mgg= plant Earth gravity = 9.8 m/s2

W = 150 lb 1st change to kg = 68.1 kgm= w/g= 68.1 kg / 9.8 m/s2

you cant do this weight is in ……newtonsW = mg = 68.1 kg 9.8 m/s2 = 667.38 N

3. G v g

• G world universe planet Earth• g Planet Earth • G 6.7 x 10 -11 (Nm2/kg2) • g = 9.8 m/s2

• The differences between the two g’

Key terms

• Mechanics • Speed• Velocity• Acceleration• Netwon’s laws of motion• Uniform motion• Force• Mass• Gravity• Netons Law of universal gravitation• Weight

Review q 1-11

Discussion Q 1-8

Problems 1-8

Investigations 1-8

www resources

• 1. www kelper.arc.nasa.gov/johannes.html• 2. www.wam.umd.edu/~tlaloc/archastro• 3. Es.rice.edu/ES/humsoc/Galileo