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The theories and laws of earth science

The Theories and Laws of
Earth Science
© Lisa Michalek
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
• Eventually, other scientists
must be able to duplicate
the results if the experiment
is destined to become the
basis for a widely accepted law or theory.
Scientific Theories and Laws
• A Scientific Theory is a testable statement
about how nature operates.
• A Scientific Law can often be reduced to a
mathematical statement, such as E = mc² with
a certain
set of conditions
(like in a vacuum).
The Big Bang Theory
• The Big Bang Theory explains
how the universe arrived at its present state.
• Based on research performed by Edwin Hubble, Georges
Lemaitre, Albert Einstein, and others, the big bang
theory hypothesizes that the universe began almost 14
billion years ago with a massive expansion event.
• At the time before the Big Bang, the universe was
confined to a single point, encompassing all of the
universe's matter. The expansion of the universe from the
Big Bang continues today, as the universe keeps
expanding outward.
• In 1965, two astronomers using radio telescopes
detected cosmic noise, or static, that didn't go away and
was detectable throughout the universe.
Hubble's Law of Cosmic Expansion
• Edwin Hubble proved that there were other
galaxies besides the Milky Way, he also
discovered that these galaxies were zipping
away from our own, a motion he called
• Edwin Hubble proposed Hubble's Law of Cosmic
Expansion (Hubble's law).
• This law established that the
universe is made up of many
galaxies, whose movements
trace back to the big bang.
Kepler's Laws of
Planetary Motion
• For centuries, scientists battled with one another
and with religious leaders about the planets'
orbits, especially about whether the planets
orbited our sun.
• In the 16th century, the scientist Copernicus
described his controversial idea of a heliocentric
solar system, where planets revolved around the
sun, not the Earth.
• But it would take Johannes Kepler, building on
work performed by others, to establish a clear
scientific foundation for the planets' movements.
Kepler's Laws of
Planetary Motion
• Kepler's three laws of planetary motion, were
formed in the early 17th century and describe
how planets orbit the sun.
• Kepler’s first Law, the law of orbits, states that planets orbit
the sun elliptically.
• Kepler’s second Law, the law of areas, states that a line
connecting a planet to the sun covers an equal area over
equal periods of time. In other words, if you're measuring the
area created by drawing a line from the Earth to the sun and
tracking the Earth's movement over
a period of time, the area will
be the same no matter where
the Earth is in its orbit when
measurements begin.
Kepler's Laws of
Planetary Motion
• Kepler’s third Law, the law of periods, allows us
to establish a relationship between a planet's
orbital period and its distance from the sun.
Because of this law, we know that a planet
close to the sun, like Venus,
has a much briefer orbital
period than a distant planet,
such as Neptune.
Law of Gravitation
• More than 300 years ago
Sir Isaac Newton proposed the idea that any
two objects, no matter their mass, exert
gravitational force toward one another.
• The benefit of the universal law of gravitation is
that it allows us to calculate the gravitational
pull between any two objects.
• For example, this ability is useful when
scientists are, planning to put a satellite in orbit
or charting the course of the moon.
Newton's Laws of Motion
• Newton’s first of the three laws states an object in
motion stays in motion unless acted upon by an
outside force. For a ball rolling across the floor, that
outside force could be the friction between the ball
and the floor.
• The second law establishes a connection between an
object's mass and its acceleration.
• The third law states, for every action
there is an equal and opposite
reaction. That is, for every force
applied to an object or surface,
that object pushes back
with equal force.
• The theory that Earth's physical structure is the
result of currently existing forces that have
operated uniformly (in the same way) since
Earth formed about 4.5 billion years ago.
• Mountains rise, valleys
deepen, and sand grains
collect now the same
way they uplifted, eroded,
and deposited over the
past millions of years.
Law of Original Horizontality
• This idea was first written by Nicolas Steno
in the 1660’s and states the fact that younger
sediments overlie older sediments.
• This principle states that sedimentary layers
are initially deposited in water in horizontal
layers due to gravity.
Law of Stratigraphic Succession or
Law of Superposition
• The 2nd law written by Nicolas Steno states
that the layer of earth sediment on the
bottom is the oldest, and each layer of
sediment gets younger as we reach the top.
Law of Lateral Continuity
• The 3rd law written by Nicolas Steno states
that the horizontal strata extend laterally until
they thin to zero thickness at the edge of their
basin of deposition.
Cross-Cutting Relationships
• This law states that the earth layer being cut is
older than the ‘thing’ doing the cutting, such as
a magma intrusion (Dike) in the image below.
• Described another way, an event
that cuts across existing rock
is younger than the disturbed rock.
• This law was developed
by Charles Lyell (1797-1875).
Principle of Inclusion
• This Law described by James Hutton states
that fragments of rock (Rock A) that are
contained (or included) within a host rock
(Rock B) are older than the host rock.
• The intruding rock (Rock A)
must have been there first
to provide the fragments.
Law of Faunal Succession
• In 1790, William Smith observed that fossils
found in the rock layers appeared in a
predictable sequence.
• From this observation this law was developed
and stated that
fossils occur in a
definite, consistent
sequence in the
geologic record.