What are the four steps of scientific inquiry?
1) Observation
2) Develop hypothesis
3) Test hypothesis
4) Accept, reject, or modify hypothesis
What happens after a hypothesis is accepted?
Next step?
Critique by scientific community
Critical thinking--> what is it?
Example:
I’m 5 ft tall and I can slam dunk a basketball
How is critical thinking used in science and why is it important?
Establishes working hypothesis and theories
Check and balance system
Keeps science objective
How is a scientific law different from a Theory?
Law:
Truth that is often expressed as a mathematical equation
Laws of physics--> laws of nature
fundamental laws that underlie all physical phenomena in the universe
law of gravity
laws of mechanics or motion
laws of chemistry
laws of energy
How does science use laws
Bases to build hypothesis and theories
Explains occurrences in nature
Helps to understand how the natural world functions
Before the laws of nature were fully understood:
Catastrophism:
The earth’s surface is shaped by sudden and large catastrophic events
affects large areas at one time
Creates drastic changes to the Earth’s topography
1600: Archbishop Ussher suggested the earth was created October 23rd 4004 BC
James Hutton: Father of geology (1800’s)
No evidence for a beginning of the earth and no evidence for the end of the earth
Formulated the principle of Uniformitarianism
The physical, chemical and biological laws that operate today have operated in
the geologic past
“The present is the key to the past”
Hutton’s ideas required something that was not required by catastrophism…What?
Difficult to comprehend
hard to quantify the age of earth
Hypothesis on how a scientist could have estimated the age of the earth prior to radioactivity
Mid 1600’s
Relative time scale created by naturalists of time
relates one rock unit to another
no definite date is given to the rock units
Methods for doing this?
Principle of superposition
In an un-deformed sequence of sedimentary rocks each bed is older than the one on top
of it
What is a sedimentary rock?
Any rock created by “gluing” together sediments
created on the surface of the earth
mudstone, sandstone, limestone etc…
Principle of Horizontality
due to gravity, sedimentary rocks are laid down horizontally
deformation or tilting occurs after deposition
Principle of cross-cutting relationships
a rock unit or fault that cuts through another rock unit or fault is younger than the one it
cuts
Principle of inclusions
if there are two rock units and one rock unit has inclusions of the other, then the rock unit
being included is older
Erosion Markers
rocks are being deposited and eroded simutaneously
more erosion than deposition--> unconformity
unconformity--> missing geologic time
Principle of fauna successions
fossil organisms succeed each other in a definite and determinable order
can recognize any time period by its grouping of fossils
index fossils
How are fossils created
remains of a living creature
molds, casts, impressions, compressions, hard deposits, desiccation, mummification, freezing
Where are fossils found?
Shells?
Plants?
Bones?
Fossils are used to:
identify rock units over large areas--correlation
created first geologic time scale based on fossil record (more in a minute)
Say something about past environments
Geologic time table
created by relative age dating techniques
correlated rock units and fossils worldwide
completed around mid 1800’s
numerical dates added later