lesson #3

Lesson #3
E.Q: What is Scientific Inquiry?

Objectives

•You will have 5-10 minutes to share within your tablemates your research.

•You will stand up and move to a different table just with your paper. 5-10 minutes to share with you new tablemate your research. (Make sure your last tablemates are not in the new table with you)

•You will share with Mr Correa one of your concepts, one from your initial team and one from your other team

•hypothesis

•theory

•objectivity

•repeatability

•experiment

•scientific method

Physics terms

Modern society has a vast and evolving body of
knowledge about the natural world. We
describe this knowledge through models:

•physical models: “The Earth orbits the Sun.”

•mathematical models: “The force of gravity is
given by the following equation . . .”

•conceptual models: “The Sun is surrounded
by a gravitational force field.”

The nature of science

Physics is both a process and a
body of knowledge.

•Knowledge includes facts,
like the mass of an electron.

•This knowledge is gained
through a skill-based process
known as scientific inquiry.

Scientific inquiry

Scientific inquiry is a process of proposing
and testing potential explanations to
“discover” which ones are true laws of nature.

A scientist might find that when she shines
light on a mirror at an angle θ, the light always
reflects from the mirror at the same angle.

If she tries this for different angles and
mirrors, she will discover that it is always true:
it is the law of reflection.

Scientific inquiry

A hypothesis is a tentative, testable
explanation for observable physical
phenomena.

Most hypotheses are incomplete or
wrong when first proposed.

Hypotheses are still important because
they provide something that can be
tested and revised.

Hypothesis

A theory is a comprehensive, well-established and
highly reliable explanation of a natural, physical
phenomenon.

Theory

Hypotheses vs. theories

Example:

Newton hypothesized that light is a particle that
bounces off a surface like a billiard ball.

Hypotheses vs. theories

Example:

Newton hypothesized that light is a particle that
bounces off a surface like a billiard ball.

Others proposed that light behaves like a wave.

Example:

Newton hypothesized that light is a particle that
bounces off a surface like a billiard ball.

Others proposed that light behaves like a wave.

Neither hypothesis is completely correct; both were
combined to form a modern quantum theory of light.

Hypotheses vs. theories

Theory vs. hunch

In everyday language you might use the word theory to
describe a hunch that you have about something.

A scientific theory is very different from your hunch.

In everyday language you might use the word theory to
describe a hunch that you have about something.

A scientific theory is very different from your hunch.

•A scientific theory has been tested again and again against
the harshest criticism and always comes up correct.

•The findings have repeatability – other experimenters

who test the theory always observe the same results.

Theory vs. hunch

The scientific method is the process of proposing theories and
rigorously testing them.

A tentative hypothesis becomes a theory only if the outcome of
every single related experiment or observation, made by multiple
researchers, agrees with the hypothesis.

Scientific method

Scientific method

Do these adjectives describe theories, hypotheses, or both?

Test your knowledge

____ a. tentative
____ b. testable
____ c. capable of being observed or supported by

experimental evidence

____ d. well-established
____ e. highly-reliable
____ f. based on natural, physical phenomena
____ g. subject to change

Do these adjectives describe theories, hypotheses, or both?

Test your knowledge

____ a. tentative
____ b. testable
____ c. capable of being observed or supported by

experimental evidence

____ d. well-established
____ e. highly-reliable
____ f. based on natural, physical phenomena
____ g. subject to change

H
B
B

T
T
B
B

Some findings have broad impact
on other scientists and on society.

Each scientist builds on the results of others
and, in the end, deepens our understanding of
the universe.

Let’s look at a few examples.

Impact of scientists
on society

1927:

Georges
Lemaitre

proposes a
Big Bang

theory.

The Big Bang

1927:

Georges
Lemaitre

proposes a
Big Bang

theory.

1948: Alpher and
Herman predict
the universe’s

temperature
based on the

theory.

The Big Bang

1927:

Georges
Lemaitre

proposes a
Big Bang

theory.

1948: Alpher and
Herman predict
the universe’s

temperature
based on the

theory.

The Big Bang

1964: Penzias

and Wilson
verify the
predicted

temperature.

1927:

Georges
Lemaitre

proposes a
Big Bang

theory.

1948: Alpher and
Herman predict
the universe’s

temperature
based on the

theory.

1964: Penzias

and Wilson
verify the
predicted

temperature.

1992: Smoot and
Mather measure

variations in

radiation that led

to present-day

clusters of
galaxies.

The Big Bang

1927:

Georges
Lemaitre

proposes a
Big Bang

theory.

1948: Alpher and
Herman predict
the universe’s

temperature
based on the

theory.

Scientific theories are subject to change as new areas
of science and new technologies are developed.

The Big Bang

1964: Penzias

and Wilson
verify the
predicted

temperature.

1992: Smoot and
Mather measure

variations in

radiation that led

to present-day

clusters of
galaxies.

Near-Earth objects

A geological team found high concentrations
of iridium in rock from the time of dinosaur
extinction.

A geological team found high concentrations
of iridium in rock from the time of dinosaur
extinction.

Only asteroids contain that much iridium.

Theory: dinosaur extinction was
caused by the impact from a giant
asteroid.

Near-Earth objects

Climate change

Many scientists are currently engaged in
research about global temperature changes
and rising sea levels.

Many scientists are currently engaged in
research about global temperature changes
and rising sea levels.

Societal impact:

These findings have led to broad societal
discussions about our impact on Earth’s
climate.

Climate change

In the process of building scientific theories, scientists must
analyze, evaluate and critique scientific explanations.

Tools for analyzing a scientific explanation:

•observational evidence

•logical reasoning

•experimental testing

Scientific analysis

Scientific explanations may be analyzed and
evaluated through observational evidence.

Observational evidence

Example: Observations of the
phases of Venus support the
explanation that both Earth and
Venus orbit the Sun.

The observations of Venus satisfy the
criteria for scientific evidence: they are
objective and repeatable.

Observational evidence

Scientific explanations may be analyzed and
evaluated through observational evidence.

Example: Observations of the
phases of Venus support the
explanation that both Earth and
Venus orbit the Sun.

Scientific explanations may be analyzed
and evaluated through logical reasoning.

Example: The explanation for
the seasons is that Earth’s
rotational axis is tilted about
23°.

Logical reasoning

How does logical reasoning allow
us to analyze this explanation?

If this explanation for the seasons is true
then it logically follows that:

An observer at noontime in
Austin, Texas (30°N latitude)
should see the Sun . . .

•at 53° from vertical in winter.

•at 7° from vertical in summer.

This is exactly what is observed!

Logical reasoning

Scientific explanations may be analyzed and evaluated through
experimental testing.

A well-designed experiment allows you to change one variable to
determine precisely how other variables respond.

Experimental testing

Scientific explanations may be analyzed and evaluated through
experimental testing.

A well-designed experiment allows you to change one variable to
determine precisely how other variables respond.

Experimental evidence must be
carefully critiqued. What are the key
questions a researcher should
consider when evaluating the quality
of experimental results?

Experimental testing

Experimental evidence must be carefully critiqued.

•Is the experiment objective? Are the observations unbiased?

•Could other variables have caused the observed effects?

•Do other researchers observe the same result?

•Has the data been analyzed to understand the uncertainties
in measurement? Are the observed effects greater than the
uncertainties in measurement?

Critiquing experimental results

ALL measured data contains some degree of uncertainty.

This uncertainty, or error, is the unavoidable difference between a
measurement and the true value of the quantity being measured.

But if physics is based on measurement, and all
measurements contain uncertainty, then how can we
ever be confident about scientific explanations based
on experimental evidence?

Uncertainty in measurement

Let’s say a student wants to test this
scientific explanation:

He drops a heavy stone and a light stone
and collects this data on the time to fall.

The student argues that this data
supports his explanation. His friend
says he’s wrong. What is the evidence
for each view? Who is right?

heavy objects fall faster
than light objects.

A test case

Ask yourself:

•What is the observed “effect”?

•What is the uncertainty in the
data? What caused the
uncertainty?

•Is the observed “effect”
significant compared to the
uncertainty in the data?

A test case

•The values for the heavy rock vary
by more than a tenth of a second.

•The average value for the two rocks
differs by only two hundredths of a
second.

A test case

This experiment does not support the
explanation because the experiment
finds no significant difference between
the heavy stone and the lighter stone.

Uncertainty can never be
eliminated.

Taking lots of data allows you
to quantify the uncertainty.

Empirical evidence must
always be evaluated with
respect to uncertainties
before any conclusion can
be made.

Quantifying uncertainty

Logic

How do you know a statement is true?
How is a scientific argument made?

How do you know a statement is true?
How is a scientific argument made?

The if-then structure: If Earth is round then it should be possible to
travel in the same direction and end up back at your starting place.

The if-then argument

How do you know a statement is true?
How is a scientific argument made?

The if-then structure: If Earth is round then it should be possible to
travel in the same direction and end up back at your starting place.

Many steps in scientific inquiry use this kind of reasoning.

The if-then argument

•It is a way to propose potential consequences of a theory being true.

•A proposed consequence is an observable test for the truth of the
theory. If the the consequence is actually observed, the theory is
supported. If the consequence is not observed, the theory is known
to be at least partly incorrect.

Propose an if-then statement involving some aspect of science
that you are familiar with.

Write down your statement.

Discuss your statement with your group.

Try it yourself

Why do things happen?

More logic

We believe the things that occur have causes that may be understood
by humans.

Cause and effect: Objects start to move because unbalanced forces
act on them.

Cause and effect

We believe the things that occur have causes that may be understood
by humans.

Cause and effect: Objects start to move because unbalanced forces
act on them.

Many explanations in science use this kind of structure.

Cause and effect

•The effect is something that happens (things start to move).

•The cause explains why or how something happens the way it does
(an unbalanced force acts).

Identify something that happens in the natural world or in technology.

Write down a statement of cause and effect that outlines at least one
potential cause for the effect you describe.

Discuss your statement with your group.

Try it yourself

1. State, in your own words, the definition of science.

Include the following ideas in your answer: evidence, testable
explanations, predictions, natural phenomena, knowledge

Assessment

1. State, in your own words, the definition of science.

Assessment

Answers will vary but should include ideas found in
the definition:

“Science is the use of evidence to construct testable
explanations and predictions of natural phenomena,
as well as the knowledge generated through this
process.”

2. You see an icicle hanging from a branch or roof and notice that the ice

forms in ripples on the surface of the icicle. Which of the following is
a valid way to test a hypothesis about these ripples?

Assessment

A. Do research for information on the internet.

B. Look for information in textbooks or at a library.

C. Ask a teacher or another knowledgeable person.

D. Do an experiment by creating icicles at different temperatures.

2. You see an icicle hanging from a branch or roof and notice that the ice

forms in ripples on the surface of the icicle. Which of the following is
a valid way to test a hypothesis about these ripples?

Assessment

A. Do research for information on the internet.

B. Look for information in textbooks or at a library.

C. Ask a teacher or another knowledgeable person.

D. Do an experiment by creating icicles at different temperatures.

Assessment

a) The speedometer on a car reads 57 miles per hour.

b) A photograph shows the planet Venus at a specific

position in the evening sky.

c) A newspaper headline announces the discovery of a

previously unknown fundamental particle

d) You notice that the temperature outside is 27ºC.

e) A teacher tells you that the atomic mass of carbon is

12.0 grams per mole.

3. Which of the following could be scientific evidence?

Assessment

a) The speedometer on a car reads 57 miles per hour.

b) A photograph shows the planet Venus at a specific

position in the evening sky.

c) A newspaper headline announces the discovery of a

previously unknown fundamental particle

d) You notice that the temperature outside is 27ºC.

e) A teacher tells you that the atomic mass of carbon is

12.0 grams per mole.

3. Which of the following could be scientific evidence?

Assessment

4. How did Penzias and Wilson contribute to our understanding of the

origins of the universe?

4. How did Penzias and Wilson contribute to our understanding of the

origins of the universe?

Assessment

In 1964, Penzias and Wilson used a microwave antenna to
measure the universe’s temperature. Their findings matched
the temperature predicted by Alpher and Herman in 1948 and
confirmed the Big Bang theory.