Download Scientific Theory and Scientific Law

Scientific Theory and Scientific Law
What is a THEORY?
 An explanation of a natural or physical phenomenon
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based on proven MULTIPLE hypotheses and verified
MULTIPLE times by independent researchers.
Often include laws in order to prove points.
Subject to changes as new evidence becomes available.
Most theories that you will discuss in a middle/high
school science class are well-confirmed and are unlikely
to be revised in any significant sense.
Theories that are less confirmed are abundant in pseudoscience fields like theoretical physics and cosmology,
such as String Theory.
Examples of Theories
 The Theory of Relativity: that the laws of physics
are the same for all observers.
 The Theory of Evolution by Natural Selection:
that the observed changes in species occur due to
selection of well adapted specimens over less well
adapted specimens.
 The Big Bang Theory explains
how the universe arrived at its present state
(expansion).
What is a LAW?
 Concise, factual (based on data) statement meant to
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prove an observation.
Can often be reduced to a mathematical statement, such
as E = mc²
Its truth is generally confined to a certain set of
conditions. For example, in the case of E = mc², c refers
to the speed of light in a vacuum.
Accepted to be true and universal by scientists.
They are used to make predictions.
Example: The product of the mass and acceleration of an
object are proportional to the force of the object. F =
MA
Examples of Laws
 Newton’s Law of Gravitation states the idea that any two
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objects, no matter their mass, exert gravitational force toward one
another. (**is used to support Einstein’s Theory of Relativity).
Newton's Laws of Motion: statements about how large objects
made of atoms behave when moving at low speeds relative to each
other.
The Laws of Thermodynamics: statements about entropy,
temperature, and thermal equilibrium.
Ohm's Law: the voltage across a purely resistive element is
equal to the current through the element times its resistance
Hubble's Law of Cosmic Expansion (Hubble's law)
established that the universe is made up of many galaxies, whose
movements trace back to the big bang (**is used to support the
Big Bang Theory).
Very Very Interesting…
 We know that Newton's Laws of motion are not, in
fact, 100% correct, but we still use them!
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They break down when the objects are very small or moving
very fast (relative to other objects).
 Why, then, do we keep them around?
 They are EXTREMELY good at predicting.
Engineers building skyscrapers need only consider Newton’s Laws.
 One can even travel throughout the Solar System using only
Newton’s Laws.
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Scientific Theories and Laws
To summarize:
 Laws tell us what happens (descriptions; can be math).
 Theories examine what happens and tell us how and
why it happens (explanations).
 Theories don't become laws; laws don’t become
theories. Both are important, but they tell us very
different things.
BOTH Scientific Theories and Laws
 Scientific Laws and Theories depend on basic elements of
the scientific method, such as a hypothesis, testing,
finding (or not finding) evidence, analyzing data and
developing conclusions.
 *Reminder: Hypothesis: A tentative statement such as
‘if A happens then B must happen because’ that can be
tested by direct experiment or observation. A supported
hypothesis can be expressed as a law or a theory.
A disproven hypothesis can sometimes be retested and found correct as measurements
improve.
 Eventually, other scientists
must be able to REPLICATE
the results if the experiment
is destined to become the
basis for a widely accepted law or theory.
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SO, both are accepted after continuous experimentation.
Question:
Mass can come from energy
and energy from mass (E= mc2)
 Is this a scientific
theory or a scientific
law?
 Scientific LAW
The speed of light in a vacuum
is constant and an absolute
physical boundary for motion
 Is this a scientific
theory or a scientific
law?
 Part of the THEORY of
relativity
Question:
Is a scientific theory or a scientific law more correct?
 Trick question! Both are equally proven to be true
through continuous experimentation.
Analyze the statements below. Law or Theory?
For every action, there is an equal and opposite reaction.
F = ma
Light is an electromagnetic phenomenon described by Maxwell’s
Laws
4. Earth’s magnetic field is generated by a conducting fluid in its core.
5. Matter cannot be created nor destroyed, only changed.
6. Energy cannot be created nor destroyed, only changed.
7. Momentum is the product of a body’s mass and its velocity.
8. The inverse-square law for gravity and Newton’s laws of motion
explain why orbits are ellipses.
9. Any two objects, no matter their mass, exert a gravitational force
toward one another that can be calculated.
10. There is a relationship between a planet's orbital period and its
distance from the sun.
11. The universe is constantly expanding outward in reaction to a huge
initial event producing matter, energy, and gravity.
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