OpenAstroChap01 (1).pptx - Survey of the Universe Chapter 1...

Survey of
the Universe
Click here for textbook
Chapter
1

Chapter 1
Science and the
Universe: A Brief Tour

1.1 The Nature of Astronomy
•
Astronomy is the study of the
sky.
•
Science is a progress report.
•
Our understanding of science
changes as we get new data.
The Orion Nebula

1.2 The Nature of Science
• Model: A simplified explanation of some natural phenomenon that can be used to
predict future results . Example: The heliocentric model can be used to predict where
the planets will be in the future.
•
Hypothesis: A proposed explanation that is narrow in scope and based on evidence
& reason. Example: The Nebular Hypothesis says our solar system was formed from
a collapsing cloud of gas.
•
Theory: a proposed explanation that is broad in scope and based on evidence &
reason.
•
Note: A theory is not an opinion! If someone dismisses a scientific theory as
“just a theory”, they don’t know what a theory is.
•
Example: The Nebular Theory says that planetary systems in general are formed
from collapsing clouds of gas.
•
Law: A mathematical rule that nature sometimes (or always) obeys. Example: from
Kepler’s 3
rd
Law, you can compute a planet’s orbital period from its orbital radius.

Notes on terminology:
Model, Hypothesis, Theory, Law
•
There is considerable overlap among the above terms.
•
In some cases, two or more of them are interchangeable.