a reminder as stated in the syllabus: “bringing someone else's clicker to class to answer for...

A ReminderA ReminderAs stated in the syllabus:

“Bringing someone else's clicker to class to answer for him/her is considered academic misconduct for both parties involved.”

As stated in the syllabus:

“Bringing someone else's clicker to class to answer for him/her is considered academic misconduct for both parties involved.”

A Scientific Theory is…A Scientific Theory is… an established model repeatedly tested with observations

and experiments quantities involved are well known abstract explanation of observations

Contrast this with a hypothesis, which is only an unverified educated “guess” that requires testing.

A theory is a comprehensive explanation of a large set of observations.

an established model repeatedly tested with observations and experiments

quantities involved are well known abstract explanation of observations

Contrast this with a hypothesis, which is only an unverified educated “guess” that requires testing.

A theory is a comprehensive explanation of a large set of observations.

Scientific TheoryScientific Theory

A theory is the highest “honor” that an idea can obtain.

A hypothesis can become a theory after extensive testing, but a theory will never “graduate” to become a fact. It is always subject to revision in light of new evidence.

A theory is the highest “honor” that an idea can obtain.

A hypothesis can become a theory after extensive testing, but a theory will never “graduate” to become a fact. It is always subject to revision in light of new evidence.

E.g., Fact: I see a cup fall to the ground. Theory: The gravitational attraction between the cup and the Earth caused the cup to fall to the ground.

The Scientific Method

The Scientific Method

1 Question2 Hypothesis

a tentative explanation

3 Prediction4 Test5 Result – becomes a

theory after repeated confirmation.passes test fails test

1 Question2 Hypothesis

a tentative explanation

3 Prediction4 Test5 Result – becomes a

theory after repeated confirmation.passes test fails test

modify

Hallmarks of ScienceHallmarks of Science

Seeks explanations based on natural causes The simplest models are usually favored

(Occam’s Razor) Models must be predictive and falsifiable by

anyone, and repeatable

A model that is not testable is not a useful model, nor is a model that is unfalsifiable. important point

Seeks explanations based on natural causes The simplest models are usually favored

(Occam’s Razor) Models must be predictive and falsifiable by

anyone, and repeatable

A model that is not testable is not a useful model, nor is a model that is unfalsifiable. important point

Hallmarks of ScienceHallmarks of Science A good theory must not only explain all known

existing observations, but needs to make new predictions that are verifiable (or falsifiable).

Example of a good theory: Big Bang Theory

A good theory must not only explain all known existing observations, but needs to make new predictions that are verifiable (or falsifiable).

Example of a good theory: Big Bang Theory

It is not enough to just explain the previously known facts, a good theory must also predict future observations important key concept

Big Bang TheoryBig Bang Theory

Fit the available data at the time it was developed (e.g., velocities of galaxies in the Universe).

Predicted (in the 1950s) that the radiation left over by the Big Bang should be redshifted into the microwave part of the electromagnetic spectrum in the form of a cosmic microwave background.

This is exactly what was detected in 1965 by Penzias and Wilson with a microwave antenna.

Fit the available data at the time it was developed (e.g., velocities of galaxies in the Universe).

Predicted (in the 1950s) that the radiation left over by the Big Bang should be redshifted into the microwave part of the electromagnetic spectrum in the form of a cosmic microwave background.

This is exactly what was detected in 1965 by Penzias and Wilson with a microwave antenna.

Which is is the most important quality of a good

theory?


theory?

A)its simplicity compared to competing theories

B)how well it explains existing observations

C)how long it has been the prevailing theory

D)its ability to make testable predictions that are later verified by new observations.






theory?


theory?





A) and B) are necessary for a good theory, but D) is the most crucial property of a good theory.





A) and B) are necessary for a good theory, but D) is the most crucial property of a good theory.

Pseudoscience/Non-Science

Pseudoscience/Non-Science

Fails to make testable predictions, or does not yield results beyond that expected from chance:

Failed Predictions Untestable

Astrology Cryptozoology

ESP/psychic ability Aliens built the pyramids

Homeopathy Anthropomorphic fallacy

Numerology

Fails to make testable predictions, or does not yield results beyond that expected from chance:

Failed Predictions Untestable

Astrology Cryptozoology

ESP/psychic ability Aliens built the pyramids

Homeopathy Anthropomorphic fallacy

Numerology

Often, these ideas have no theoretical foundation on why they should work.

These ideas cannot be proven right or wrong.

Is Pseudoscience Alive Today?


$3 billion spent on homeopathy by Americans in 2007





39 people followed Marshall Applewhite to their deaths in an attempt to hitch a ride on a spaceship behind Comet Hale-Bopp in 1997







Hoopla over December 21, 2012, the Mayan calendar, Harold Camping/Rapture, arrival of Planet X/Nibiru

see conspiracy websites: abovetopsecret.com

godlikeproductions.com



Hoopla over December 21, 2012, the Mayan calendar, Harold Camping/Rapture, arrival of Planet X/Nibiru

see conspiracy websites: abovetopsecret.com

godlikeproductions.com

Myth of Fact?Myth of Fact?

Time slows down for objects moving at a high velocity.


Time slows down for objects moving at a high velocity.

Fact! Einstein’s theory of relativity predicts that time dilates and length contracts as velocity increases.

This has been confirmed with atomic clocks flown on commercial airplanes (J.C. Hafele and R. E. Keating, Science 177, 166 (1972)).


In the southern hemisphere, water goes down sinks or toilets in the opposite direction as in the northern hemisphere because of the Coriolis effect.


In the southern hemisphere, water goes down sinks or toilets in the opposite direction as in the northern hemisphere because of the Coriolis effect.

Myth! The Coriolis effect only matters on very large (hundreds of km) length scales, not the diameter of your sink.

Myth of Fact?Myth of Fact?If you hook up your TV to an external antenna such as rabbit ears and set to channel where you don’t see any reception, you can see and hear the Big Bang.

Myth of Fact?Myth of Fact?If you hook up your TV to an external antenna such as rabbit ears and set to channel where you don’t see any reception, you can see and hear the Big Bang.

Fact!About 1% of the static you see is cosmic microwave background radiation left over from the Big Bang.

Chapter 3 Study GuideChapter 3 Study Guide1) Many ancient cultures knew the night sky and

Sun/Moon movements for agricultural/religious reasons, but only the Greeks tried to model the Universe.

2) Greeks knew how large, round Earth was.

3) Plato/Aristotle/Ptolemy developed Greek Earth-centered Universe, since they could not detect stellar parallax.

4) Greeks assumed heavens were “perfect” described by perfect circles, model stood for 1500 years.

5) Greeks needed epicycles (smaller circles-in-circles) to explain retrograde motion of planets – very contrived.

Chapter 3 Study GuideChapter 3 Study Guide6) In Renaissance, Copernicus introduced concept of a

Sun-centered Universe….but still insisted on perfect circular orbits still needed epicycles, not any more accurate.

7) Tycho Brahe – best observer of era, hired Kepler, pet moose

8) Kepler - Breakthrough discovery that elliptical orbits are required.

9) Kepler’s 1st Law – planets orbit on elliptical orbits with Sun at one focus.

10) Kepler’s 2nd Law – planets sweep out equal areas in equal time periods planets move faster when near Sun

Chapter 3 Study GuideChapter 3 Study Guide10) Kepler’s 3nd Law – square of planet’s period

equals the cube of the semi-major axis of orbit (P2 = a3) more distant planets travel more slowly

11) Galileo – pointed telescope toward sky, solidified Sun-centered model – sunspots, phases of Venus, Moon craters (imperfections), moons of Jupiter

12) Scientific theory – explains facts, will never become fact

13) Theory can be refuted at any time with new evidence,

forcing theory to be revised.

14) Crucial property of good theory it makes predictions

that can be tested, i.e., Big Bang Theory

Chapter 4 Making Sense of the Universe:

Understanding Motion, Energy, and Gravity

Chapter 4 Making Sense of the Universe:

Understanding Motion, Energy, and Gravity

How do we describe motion?

How do we describe motion?

Precise definitions to describe motion:

• Speed: Rate at which object moves

€

speed = distancetime

units of ms ⎛

⎝ ⎜

⎞

⎠ ⎟

Example: 10 meters/second

• Velocity: Speed and direction Example: 10 meters/second, due east

• Acceleration: Any change in velocity - units of speed/time2 (meters/second

per second)

Speeding up and slowing down is an acceleration. Turning in your car is an acceleration because your direction is changing (even if your speed is constant).

Force and accelerationForce and acceleration

Force = mass * acceleration

• Accelerations are caused by forces

That’s why you feel a force on your body when you speed up, slow down, or turn a corner – you are changing your velocity, and a change in velocity is an acceleration.

In which of the following situations are you not

experiencing a net force?


experiencing a net force?A) After you’ve jumped off a diving board.

B) As you apply the brakes on your bike.

C) As you round the corner on a curved road.

D) While you’re moving upward in an elevator at constant velocity.

A) After you’ve jumped off a diving board.





experiencing a net force?


experiencing a net force?A) After you’ve jumped off a diving board.




A) After you’ve jumped off a diving board.




If velocity isn’t changing, there is no net force!

MomentumMomentum

Linear momentum = mass * velocity - a force is needed to change momentum, which changes the velocity, which means an acceleration

Angular momentum = mass * velocity * radius - rotational momentum of spinning/revolving objects

- a top spinning in place has no linear momentum, but it does have angular momentum - a spinning top moving in a straight line has both linear and angular momentum

Linear momentum = mass * velocity - a force is needed to change momentum, which changes the velocity, which means an acceleration

Angular momentum = mass * velocity * radius - rotational momentum of spinning/revolving objects

- a top spinning in place has no linear momentum, but it does have angular momentum - a spinning top moving in a straight line has both linear and angular momentum

We will talk about angular momentum throughout this course – understand it.

Why do objects move at constant velocity if no net force

acts on them?

Why do objects move at constant velocity if no net force

acts on them?

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

Total gray ball + yellow ball momentum is conserved – it can be exchanged, but not destroyed (without an external force).

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

Total gray ball + yellow ball momentum is conserved – it can be exchanged, but not destroyed (without an external force).

Objects continue at constant velocity because of conservation of momentum.

Conservation of Angular Momentum

Conservation of Angular Momentum

The angular momentum of an object cannot change unless an external twisting force is acting on it.

Earth experiences no twisting force as it orbits the Sun, so its orbit will continue indefinitely.

Conservation of angular momentum is important for solar system formation, star formation, black hole accretion, etc., etc.

The angular momentum of an object cannot change unless an external twisting force is acting on it.

Earth experiences no twisting force as it orbits the Sun, so its orbit will continue indefinitely.

Conservation of angular momentum is important for solar system formation, star formation, black hole accretion, etc., etc.

Angular momentum = mass * velocity * radius

Angular momentum conservation also explains why objects rotate faster as they shrink in radius.

Mass * velocity * radius = constant

If radius (arm length) goes up, velocity must go down to conserve angular momentum

If radius (arm length) goes down, velocity must go up to conserve angular momentum

Angular momentum cannot be created or destroyed, only transferred between objects.

Important concept!

a reminder as stated in the syllabus: “bringing someone else's clicker to class to answer for...

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