Learning Activity 1a: Law vs. Theory
Unit A: Earth’s Place in the Universe
Learning Target:
1a) I can compare and contrast law and theory in science. (DOK1-2)
Teacher Notes:
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If you had a better source in your text book you could use it
If you have advanced students they could create a Venn diagram to compare and contrast
law, theory, and hypothesis
Below is what should be on the Venn diagram
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THEORY
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Explanation
supported with repeated testing
valid as long as no evidence
contradicts it
can be disproven
‘accepted hypothesis’
ex: big bang theory
ex: nebular theory of formation of
the solar system
theory of evolution
ex: asteroid hit Tunguska Siberia in
1908
LAW
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 both describe
an observable
phenomenon –
are based on
observations
and/or data
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Describes
Generalizes a body of
observation
occurs in many observations
and experiments
no exceptions at the time the
law is made
ex: Newton’s Law of Gravity
Newton’s Laws of Motion
Kepler’s Laws of Planetary
Motion
Archimedes Buoyancy
Principle
Hubble’s Law of Cosmic
Expansion
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Learning Activity 1a: Law vs. Theory
Unit A: Earth’s Place in the Universe
Learning Target:
1a) I can compare and contrast law and theory in science. (DOK1-2)
DIRECTIONS: Use the reading below to create a Venn diagram that compares and contrasts law and
theory in science. When creating the Venn diagram be sure to include descriptors of law and theory as
well as examples.
Law vs. Theory
Words have precise meanings in science. For example, 'theory', 'law', and 'hypothesis' don't all
mean the same thing. Outside of science, you might say something is 'just a theory', meaning
it's supposition that may or may not be true. In science, a theory is an explanation that generally
is accepted to be true. Here's a closer look at these important, commonly misused terms.
Hypothesis
A hypothesis is an educated guess, based on observation and/or data. It is usually found in the form of
If… then… because… which indentifies an independent variable, a dependent variable, and a reasonable
explanation. Usually, a hypothesis can be supported or refuted through experimentation or more
observation. A hypothesis can be disproven, but cannot be proven to be true.
Example: If you see no difference in the cleaning ability of various laundry detergents, you might
hypothesize that cleaning effectiveness is not affected by which detergent you use. You can see this
hypothesis can be disproven if a stain is removed by one detergent and not another. On the other hand,
you cannot prove the hypothesis. Even if you never see a difference in the cleanliness of your clothes
after trying a thousand detergents, there might be one you haven't tried that could be different.
Theory
A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with
repeated testing. The theory includes a plausible explanation for the observations and/or data. A theory
is valid as long as there is no evidence to dispute it. Therefore, theories can be disproven. Basically, if
evidence accumulates to support a hypothesis, then the hypothesis can become accepted as a good
explanation of a phenomenon. One definition of a theory is to say it's an accepted hypothesis.
Example: It is known that on June 30, 1908 in Tunguska, Siberia, there was an explosion equivalent to
the detonation of about 15 million tons of TNT. Many hypotheses have been proposed for what caused
the explosion. It is theorized that the explosion was caused by a natural extraterrestrial phenomenon,
and was not caused by man. The event occurred – it was observed. The possible explanation is generally
accepted to be true, based on the evidence scientists now at this point in time. If new evidence is
discovered that cannot be explained by this theory, then this theory will have to be changed or
discarded.
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Law
A law generalizes a body of observations. At the time it is made, no exceptions have been found to a
law. Scientific laws are often represented by a mathematical equation. Scientific laws describe things,
but they do not explain them. One way to tell a law and a theory apart is to ask if the description gives
you a means to explain 'why'.
Example: Consider Newton's Law of Gravity, which basically states that any two objects in the Universe
exert gravitational attraction on each other. According to Newton, that gravitational attraction is
proportional to the masses of the objects and inversely proportional to the distance between the two
objects. It is often shown as a mathematical equation:
Newton could use this law to predict the behavior of a dropped object, but he couldn't explain why it
happened.
As you can see, there is no 'proof' or absolute 'truth' in science. The closest we get are facts,
which are indisputable observations. Note, however, if you define proof as arriving at a logical
conclusion, based on the evidence, then there is 'proof' in science. I work under the definition
that to prove something implies it can never be wrong, which is different. If you're asked to
define hypothesis, theory, and law, keep in mind the definitions of proof and of these words can
vary slightly depending on the scientific discipline. What is important is to realize they don't all
mean the same thing and cannot be used interchangeably.
Source for the above reading: http://chemistry.about.com/od/chemistry101/a/lawtheory.htm
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