Transcript The Scientific Method

The Nature of Science
Questions for Consideration
How do scientists solve problems?
 What are some aspects of a scientific
experiment?
 What is the difference between a scientific
law, a hypothesis, and a theory?
 What is the importance of scientific
literacy?

How Do Scientists Solve Problems?

The myth of “the scientific method”.
 Not
just one method for problem-solving.
 “Scientific method” often taught in school is a
simplified procedure for building knowledge.
 Real
science can be much more exciting and
complex.
 No specified order for building knowledge.
How Do Scientists Solve Problems?

Online Homework Assignment:
 Visit
the following site:
 http://www.undsci.berkeley.edu
 Answer
the questions on the worksheet you
have been given.
 Due Friday, January 30, 2009.
 For
a copy of the worksheet, click below:
What Are Some Aspects of a
Scientific Experiment?

Variables – factors that can change.
 Manipulated
variable – changed by the
experimenter.
 “Independent
variable”
 Responding
variable – observed by the
experimenter.
 “Dependent

variable”
Control
 Variables
that are kept constant.
 Ensures that the impact of another factor can
be better understood.
Example
A contract research organization (CRO) is being
paid to find out if a new drug for tuberculosis
yields better results than the standard
treatment.
 They organize a double-blind study:



One group of patients is given the new drug.
One group of patients is given a placebo.


Placebo: A “sham” therapy that does not actually contain any
sort of medication.
Both groups’ progress is compared to the progress of
patients who receive the standard therapy.
Example

In the clinical study, what is the CRO
attempting to find out?
 If
the new TB drug is more effective than the
standard treatment.

What is the control group?
 The

placebo group is the control group.
What is the responding variable?
 The
health of the group that receives the drug
(compared to the health of the group that
receives the standard treatment).
Fact, Hypothesis, Law, Theory

Fact


Hypothesis



A proposed explanation for observations.
Can be supported or refuted by further testing.
Law


An observation.
A concise statement that describes a relationship in
nature.
Theory



A broadly supported explanation for a set of observed
phenomena.
Theories CANNOT be 100% proven.
They are generally accepted as true unless disproven.
The Nature of Science

Science:
 is
tentative.
 doe NOT follow a single method.
 is goal-oriented.
 uses laws to describe and theories to explain.
 is creative.
The Tunguska Event

On June 30, 1908 there was a large
explosion above the Tunguska region in
Russia.
 At
about 7:17 am local time, eyewitnesses
near Lake Baikal in Russia reported seeing a
column of intense blue light moving across
the sky.
 A few minutes later, they saw a bright flash of
light and heard loud bangs, like artillery fire.
The Tunguska Event

Witnesses closer to the explosion were knocked
off their feet by the shockwave.




They reported intense heat and pressure from the
blast.
Windows were broken hundreds of kilometers from
the blast site.
Tremors from the explosion were registered at seismic
stations all across Europe and Asia.
The explosion is thought to have been
equivalent to 10 – 15 Megatons of TNT, or about
1000 Hiroshima A-bombs.

It is also thought that the explosion happened about
5 – 10 kilometers above the Earth’s surface.
The Tunguska Event
The Tunguska Event

What caused the Tunguska event?

There have been many proposed explanations, or
hypotheses:






An alien spaceship exploded high above the Earth.
A small black hole hit the Earth.
An asteroid or comet entered Earth’s atmosphere and
exploded.
A top-secret superweapon was being tested or deployed by
the US or Russia.
A chunk of antimatter entered Earth’s atmosphere and selfdestructed when it contacted normal matter.
A huge amount of natural gas was released from the Earth’s
crust and exploded in the air.
The Tunguska Event

Scientists actively debate various hypotheses and
attempt to use available evidence to develop a
theory.


The current theory: a comet or asteroid exploded in the
lower atmosphere.
Supporting evidence:



Asteroids and comets do exist.
Particles from outer space enter Earth’s atmosphere
every day.
When they do, they burn up or explode because of the
heat generated by the compressed air in front of them.
The Tunguska Event

Supporting evidence:




A larger object (a few tens of meters across) would
release energy consistent with the Tunguska blast.
Fragments found embedded in downed trees are
consistent with asteroid and comet composition.
Eyewitness reports are consistent with an asteroid or
comet impact.
Also, the asteroid/comet impact hypothesis is
parsimonius.

it doesn’t require the existence of things that must be
assumed without evidence, like alien spaceships or
secret superweapons.
The Importance of Scientific Literacy

You are going to see ten true-false
statements that will test your scientific
literacy.
 Try
to determine whether each statement is
true or false.
The Statements
 1.
TRUE
Science only produces tentative conclusions that can
change.
 2. Science has one uniform way of conducting research
False
called “the scientific method”.
 3. When being scientific one can have faith only in what is
TRUE
justified by empirical evidence.
false
 4. To be scientific one must conduct experiments.
 5. An experiment can prove a theory true.
false
 6. Scientific theories are just ideas about how
false
something works.
 7. An accepted scientific theory is a hypothesis that has
TRUE been confirmed by considerable evidence and has
endured all attempts to disprove it.
TRUE
 8. Scientists construct theories to guide further research.
 9. Scientists work alone without sharing data or ideas.
false
 10. Imagination and creativity are used in all stages of
TRUE
scientific investigations.
What Is The Importance of Scientific
Literacy?

Scientific literacy makes you an informed
person:
 It
helps you make decisions in elections.
 It keeps you from being fooled by people who
make fraudulent claims.
 It keeps you from being worried about things
you don’t really have to worry about.
What Is The Importance of Scientific
Literacy?
If somebody tells you that the world is
going to end in 2012, be skeptical.
 If somebody tells you that vaccines cause
autism in children, ask for evidence.
 If somebody tells you that the Large
Hadron Collider will destroy the world,
consult a real scientist to find out.
 Examine the evidence for yourself and
make your own informed decisions.

Skepticism
The truth is out there...but so is this garbage.