1.2. the scientific method -...

Copyright © 2010 Pearson Education, Inc.

1.2. The Scientific Method

As this course will involve many

laboratory investigations, let us

review…


Science

• Science seeks explanations - to mysteries!

– to explain (understand) the past and present,

and to predict the future

• To aid decision-making

• To develop technology, to make life better

• Science is a body of knowledge, but it is

also a process – an endless quest

– A discovery typically raises more questions

– Progress is made by continual questioning

• Though questioning established science without

reason (logical or observational) can impede

progress


The Scientific Method

An organized (systematic) way to make progress

through continual observing, questioning, and

revising ideas

Figuring out how nature works without the User’s

Manual – by trial and error!

Four Steps of the Scientific Method:

1. Observe (question and research)

2. Hypothesize (propose an explanation)

3. Test (experiment)

4. Conclude


1. Observe and Question • To the curious, an observation leads to a question.

“Why is the desktop black and the whiteboard white?”

• Describe the observations in a precise way.

• Research: Look for an existing answer in the

“peer-reviewed scientific literature” (what

professionals have observed, tested and thought).

– Become an expert!

– Be critical! Not everything you read or hear is correct.

Observations trump theory.

“Study nature, not books.” ---Louis Agassiz

– There can be discrepancies, especially on the Internet!

Conflicting answers identify the need for an explanation.


2. Hypothesize

Draw inferences from what you’ve observed and

read, and if unsatisfied, propose your “best guess”

hypothesis. Do not be afraid to be creative!

• Inference: a logical interpretation of observations

• Hypothesis: a proposed explanation for a set of

observations that can be verified or rejected by

experiments (that makes a prediction)

– An equation can be a hypothesis. The math

makes a prediction, which data can verify.


Mathematics: The Language of Science

• Ideas of science are unambiguous when

expressed in mathematical terms.

• Scientific observations are unambiguous when

quantified with accuracy.

• Equations express the exact relationships

between properties, and allow quantitative

prediction.


Models

Model: A representation

• Physical model: a 3-D object

• Conceptual model: an analogy

– E.g. “light waves”

• Mathematical model: an equation that describes

and predicts

• Numerical model: A computer simulation, that

solves equations and displays them graphically


Which of these is a scientific hypothesis

(that could be proved wrong)?

a. Atoms in proper proportions make us feel good.

b. Atoms are in all the stars in the universe.

c. An atom is the smallest bit of matter in a

material.

d. Distant galaxies have atoms not found on Earth.

Answer: c. Statement c has, in fact, been proved wrong.

Protons and electrons, for example, are smaller than

atoms. But it is an idea that is testable.


Which of these is a scientific hypothesis?

A. The Moon is made of green cheese.

B. Atomic nuclei are the smallest particles in nature.

C. A magnet will pick up a copper penny.

D. Cosmic rays cannot penetrate the thickness of your

Physics textbook.

Answer:

All are scientific hypotheses!

All have tests for proving wrongness, so they pass the test of

being a scientific hypothesis.


3. Test = Experiment

• Make precise measurements to test your

hypothesis.

• Describe your method and results in an orderly,

logical and precise way.

“It was 82 ºF”, not “It was hot”.

• Repeat the experiment several times.

1. In order to prove or disprove a hypothesis,

experimental results must be reproducible.

2. Variability in the outcome of an experiment allows the

uncertainty to be quantified, which is important.


Independent Variables and

Dependent Variables In an experiment, if possible, change only one thing

at a time, to isolate the effect of that single change.

The quantity you change, x, is the independent variable.

The quantity you measure, y, which is affected by x, and is

therefore interpreted as a mathematical function of the

independent variable, y(x), is the dependent variable.

Which should be your dependent vs. independent

variables depends on cause-and-effect, your

hypothesis and your ability to control and accurately

measure variables.

Ideal Gas Law: P × V = n × R × T


4. Conclude • Was your hypothesis correct?

• A hypothesis is considered validated if it is able

to account for known observations and to

correctly predict new observations. It may lead to:

• Theory: an explanation for a set of verified

hypotheses that makes accurate predictions

– Considered true, but subject to revision or

modification

• Law: a description of specific relationships (a

verified mathematical equation) that is widely

applicable, has been tested repeatedly and has

not been contradicted


4. Conclude (cont.)

This step takes a lot of integrity!

• Results may not be as expected. That is

OK.

• We learn by our mistakes.

• Must be willing to dispel or revise theories.

Or not.

• The truth will out.


Lab Report/Article Format

1. Introduction: Question, Short Review of

Previous Work, and Hypothesis

2. Methods

1. List of Materials

2. Experimental Procedure

3. Results: Data Tables and Observations

4. Analysis of Data, including Uncertainty

5. Conclusions


The Scientific Attitude

The scientific attitude is one of

• inquiry.

• experimentation.

• willingness to admit error.


The Scientific Attitude

Scientists

• are experts at changing their minds.

• must accept experimental findings.

• test for erroneous concepts.

• seek to understand objections and

positions of antagonists.


Science requires…

• Creativity (openness to new possibilities)

• Logic (objectivity, dispassion)

• Order (systematic method)

• Precision (quantification)

• Integrity (courage, humility)

• Trust and Skepticism (questioning)

Keep an open mind, but bound by logic, math,

observation, consistency with other evidence


Science as Putting a Puzzle

Together

Sometimes a piece is put in the

wrong place!


The Cutting Edge of Science

The Cutting Edge of Research

Established

Science

Scientists at the forefront of

research often disagree. It

is good that they do! This

allows an exploration of

alternative hypotheses and

even alternative theories.

Eventually, the different

strands of knowledge get

woven together into what is

considered Established

Science.

Disagreement does not

invalidate science, but is

part of the process.


A person who says, “that’s only a theory!” likely

doesn’t know that a scientific theory is a

A. guess.

B. number of facts.

C. hypothesis of sorts.

D. synthesis of well-tested hypotheses and facts.

Answer: D.

The word “theory” in everyday speech is

different than its use in science.

In science, only a vast, experimentally verified

body of knowledge is a theory.


Belief and Science

• “Science is built on proof, not belief”

– True on the community level, but not on the

individual level

• There is a vast body of scientific work; it would

be impossible to “prove it for yourself”

• Progress in science takes belief (trust) in others

• Another’s work is deemed “trustworthy” if it

appears logical, precise, impartial, and agrees

with what you do “know” (consistency)

• Trustworthiness comes from honesty


The Scientific Community

• Publish results to make them known to the scientific

community

– Discoveries that remain hidden are useless

• Often the impact (application) of basic research is not

realized until many years later

– To get credit, to get $ to do more research

– When publishing a report, provide a bibliography to

demonstrate awareness of the latest research, how

the new results fit in with it, and to give credit where

credit is due

• Peer-review: a scientific report is sent to several other

experts in the field to look it over for errors, oversights

and impartiality i.e. quality control for trustworthiness

– Only after it is approved (judged) by experts will it be

published (as is, edited with revisions, or rejected)


Summary

Know these terms:

• The Scientific Method (4 steps)

• Inference

• Hypothesis, Theory and Law

• Model (4 kinds)

• Dependent Variable

• Independent Variable

• Peer-review

• Lab Report/Article Format (5 parts)


Dependent vs. Independent Variable

The higher I drop a book from, the louder

the sound it will make (on a scale of 1 to 10).

• Is this a hypothesis?

– Yes. But…

– the method is imprecise. Use decibels.

• What is the independent variable?

– Height of drop.

• What is the dependent variable?

– Loudness (intensity in decibels).


The Scientific Method

Observation First Theory


New Observation

retrograde motion

of Mars New Hypothesis


New Theory Nicolaus Copernicus,

1543. Actually the

heliocentric model

was proposed as an

alternative hypothesis

by Aristarchus of

Samos (c. 250 BC)

but remained a

hypothesis for almost

two millennia! It was

verified by the precise

observations of N.C.

that agreed with what

the math predicted.

1.2. the scientific method -...

Documents