Theory & Law
• •MISCONCEPTION: If evidence supports
a hypothesis, it is upgraded to a theory. If
the theory then garners even more
support, it may be upgraded to a law.
• In other words: Theories don’t graduate
into laws and laws don’t get “down graded”
into theories.
SCIENTIFIC LAWS
• Are statements of fact meant to explain, in concise terms, an
action or set of actions.
• Are generally accepted to be true and universal, and can
sometimes be expressed in terms of a single mathematical
equation.
•
Are similar to mathematical postulates. They don’t really need
any complex external proofs; they are accepted at face value
based upon the fact that they have always been observed to be
true.
Give me some examples of
scientific laws!
• Newton’s Three Laws of Motion
• The Laws of Thermodynamics
• Boyle's law of gases
• The law of conservation of mass and energy
• Hooke’s law of elasticity
• Galileo's law of free fall
• Kepler's three laws of planetary motion
• Newton's law of gravitation
Laws, continued
• Great examples! But I’m still not sure
I can identify a law if I saw one.
No problem! Here’s a quick way of
classifying laws:
• They have the following universal form:
"in all cases when condition of kind A are
realized, conditions of kind B are realized
as well."
• This means laws are suited to mathematical formulas!
So when one condition happens, the result can be
predicted.
Example: If something is thrown up,
then it will fall back to earth at a
certain speed.
More law clarification
• Not ALL laws can be expressed
mathematically, but they’re a good
guide to classifying laws as
statements of absolute truth.
•
Example: Newton’s Third Law says
“For every action, there is an equal
and opposite reaction.”
• This can be expressed as:
F12 = -F21
HYPOTHESIS
Scientists design investigations based on testable questions they have
developed. These questions list specific things that will be involved in their
investigation.
A hypothesis is a statement that predicts the
outcome of an investigation.
(If we do this, then this will happen.)
The purpose of a hypothesis is to organize an experiment. If the hypothesis is
carefully formed, all the steps of the scientific method follow - the hypothesis
provides the structure.
Give me some examples!
Examples are:
• If the temperature of a gas is increased,
then the volume will increase.
• If the length of a pendulum increases, then
the period of swing will decrease.
• If runners drink water and run in a race,
then they will run faster than runners who
drink a sports drink.
Notice a pattern?
• Be careful - Not all "if-then" statements are
hypotheses.
• For example the statement:
"If you warm yeast, then more gas will be produced" is a
prediction, not a hypothesis.
You have not answered the questions:
• What is being tested?
• What is related to what?
• Is temperature a variable?
• Is yeast a variable?
• Is gas production a variable?
Hypothesis continued:
The Differences between a Hypothesis, Theory, and Belief
Hypothesis
A hypothesis is a tentative explanation or idea about how things work. It
guides you in further work to get a better answer.
•
For example:
"If a trip was made to the moon then it would be found that the moon is
made of cheese."
How could we test this hypothesis?
•
•
•
•
Construct a rocket to go to the moon and return with samples.
Make a cheese pizza substituting the moon samples for the cheese.
Ask people to eat the pizza and see if they can tell any difference from
pizza made with real cheese.
Most likely conclusion: Hey, this pizza tastes like dirt.
SCIENTIFIC THEORIES
• This one is perhaps the
most “controversial” of the
terms we’ve looked at so
far.
• Why? Simply because
people mistake a scientific
theory for the every day
use of the term “opinion”.
SCIENTIFIC THEORIES
• A "theory" is not an insult (as in the silly saying "it's
just a theory"). A theory is simply the most elaborate
form of consistent scientific knowledge not yet
disproved by experiment.
• In experimental sciences, a theory can never be
"proved", it can only be "disproved" by
experiment.
• This is precisely was makes a theory scientific. A
statement that cannot be disproved by experiment may
still be highly respectable but it's simply not part of any
experimental science.
All of these theories are well documented
and proved beyond reasonable doubt:
•
•
•
•
The theory of evolution
The theory of relativity
The atomic theory
The quantum theory
A theory is more like a scientific law than a hypothesis. A
theory is an explanation of a set of related observations
or events based upon proven hypotheses and verified
multiple times by detached groups of researchers. One
scientist cannot create a theory; she can only create a
hypothesis.
Laws vs. Theories
•
The biggest difference between a law and a theory is that a
theory is much more complex and dynamic.
A law governs a single
action, whereas a
theory explains an
entire group of
related phenomena.
An analogy can be made using a slingshot and
an automobile.
•
A scientific law is like a slingshot. A slingshot has but one moving partthe rubber band. If you put a rock in it and draw it back, the rock will
fly out at a predictable speed, depending upon the distance the band is
drawn back.
•
An automobile has many moving parts, all working in unison to perform
the chore of transporting someone from one point to another point. An
automobile is a complex piece of machinery. Sometimes, improvements
are made to one or more component parts. A new set of spark plugs
that are composed of a better alloy that can withstand heat better, for
example, might replace the existing set. But the function of the
automobile as a whole remains unchanged.
•
A theory is like the automobile. Components of it can be changed or
improved upon, without changing the overall truth of the theory as a
whole.
Putting it together
• Where do scientist begin? With the
scientific method. Before conclusions
can lead to a law or formula, it must be
tested!
• Data and conclusions are drawn from
data gotten from experimenting.
• Here are the steps to experimenting:
What happens when people draw
conclusions from nothing in
particular?
Those are beliefs!
• Beliefs guide your actions because they’re based on your
history. They’re not based on anything besides thinking a
thing is so.
» Is this science? NO
• You may believe that all dogs are friendly and this might
prompt you to pet any and all dogs you see. But not all dogs
are friendly. So your belief may be based on your past
experiences/family/religion/habits, etc. but are not at all
scientific.
• The result – NO conclusions can be drawn from what you
believe.
Science draws conclusions from the facts that are
found from experimenting.
Everyday theories are not scientific. The
conclusion is offered first, then facts are found
to support that.
That’s not science folks.