Transcript Ast

The Scientific Method
The Scientific Method
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7 steps of the scientific method
1.
2.
3.
4.
5.
6.
7. Report you findings
Observation
May be the most important step.
Before you can really do anything, you must first
notice that something needs to be done.
Observation is really recognizing a discrepancy.
Astronomers who relied on their powers of
Observation:
Galileo, Newton, Ptolemy
Statement of the problem
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Always written as a “
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” question.
What is the effect of increased temperature on cricket
chirps?
What is the effect of increased speed on fuel
consumption?
 Stating the observed discrepancy in the manner of
a question allows one to develop an answer.
 What questions lead to a cause and effect. “Why”
questions can be answered with a simple
“because”.
hypothesis
Defined as an __________________
 The hypothesis is what you think is the best
answer to the question you posed when you
stated the problem.
 Best when written as a cause and effect.
 When developing a hypothesis, always keep in
mind the original observation, and the problem
that you are trying to answer.
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Designing an experiment
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Experiment- is
which addresses a
particular problem.
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What are some things to think about when
designing an Experiment?
Things to think about when
designing an experiment
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Materials that are readily available
Parts of an experiment
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Control: Aspect of the experiment that is held
constant so as to have a standard of
comparison.
_________________: the factor that is adjusted
by the experimenter.
: The factor which changes
as a result of the independent variable
 The
dependent variable depends on
the independent variable
Experiment (continued)
: part of the experiment
that is used as a control.
 Constant:
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: group with in the
experiment which all things are the same
as the control group except for one aspect,
which is referred to as the _________.
Collect and analyze data
After the experiment has been conducted,
data must be collected and analyzed.
Things to think about:
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Draw Conclusions
Conclusions are judgments based on an
experience and the interpretation of data.
Conclusions can be different.
We all have different experience
Some conclusions are better than others.
The difference between a good astronomer and
an average astronomer may be the ability to
draw relevant conclusions.
Report findings
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In the field of Astronomical research this entails
writing papers
Basically you are responsible for informing the
community of your results
You recognized a gap in our knowledge about
the world around us. Once you know the
information you need to tell the public so as to fill
the gap.
That means being able to properly communicate
The cyclical nature of science
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If your hypothesis is not proven correct by
your experiment you must reject it, and
draw whatever conclusions that you can
then develop a new hypothesis and
experiment.
Theory
When conclusions associated with a
specific hypothesis are continuously
supported by many different experiments
then the hypothesis is considered a theory
 When a theory is continually support and
considered to be a rule of nature then it is
said to be a law.
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The Nature of Science
Types of reason
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: reasoning from a particular set of
facts to a general rule.
: suggesting something is true about
a specific case from a known general rule.
Types of research
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: controlled experiments that result
in counts or measures. Numerical data
: observational data often
descriptions of observations of animal behavior.
Science and Society
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Society must take responsibility for how a scientific
discovery is used.
But science is limited to addressing questions that can
be answered using the scientific method, and the
methods MUST be ethical.
A scientist does NOT decide what is ethical and what is
not, rather society dictates the ethical guidelines that a
scientist must adhere to.
Ethics- is a study of the standards of right and wrong.
Technology- The application of scientific research to
society’s needs and problems.
Metric System
International system of
measurements
In 1975 the United States passed the
Metric Conversion Act. The intent was for
the U.S. to use the metric system like the
rest of the world. What happened instead
was that metric units were placed on
labels in addition to the standard units
 We will use metric units in this class
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Prefixes
 Prefix Symbol
x factor
Kilo
 Deci
 Centi
 Milli
 Micro
 Nano
1000
0.1
0.01
0.001
0.000001
0.000000001
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k
d
c
m
n
Units of Measure
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Length
Meter (m)
 1 meter = 100 centimeters (cm)
 10mm=1cm=0.1dm=0.01m=0.00001km
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 Examples
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7 m = 700 cm = 7000 mm
7 m = 0.007 km
92 m = 0.092 km
550 cm = 5.50 m
3.6 m = 3600 mm
Units of Measure
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Notice there were no units for EXTREMELY large distances.
In astronomy there are SEVERAL units of measure for great
distances:
Astronomical Unit (AU) – The average distance between the
Earth and the Sun.
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1 AU = 1.5 x 1010 m or 150 million km
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Light year - (NOT A UNIT OF TIME!) The distance that light
travels in a year.
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Mercury = 0.4 AU from the Sun
Earth = 1AU from the Sun
Pluto = 40 AU from the Sun
Light travels 9.46 x 1015 m in on year
Parsec – Distance at which an observer sees the maximum
angle between the Sun and the Earth to be one arc second.
(We may discuss this later, we most likely will not be using parsecs as a unit of
measure.)
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1 parsec = 3.26 light years (3.09 x 1013 km).
Units of Measure
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Mass
The amount of matter in an object
 We will work mainly in grams
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 1000
grams (g) = 1 Kilogram (kg)
 1 gram = 1000 milligrams (mg)
 Examples
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4.601 kg = 4601 g
9 g = 9000 mg
Units of Measure
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Volume: the amount of space an object
occupies.
SI (System International) for volume is the liter (L)
1000L = 1 kiloliters (kL)
We will mostly be using milliliters (ml)
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1000 mL = 1 L
The great thing about SI (System International) is
that 1 mL = 1cm3
Volume can be easily converted to mL or L from
the measurement of length
Meniscus – the curved surface of a liquid.
Units of Measure
Density= mass/volume
 Used to identify an object
 D = M/V
 Units is g/ml or g/cm3
 How many grams is a substance if it has a
density of 19.3 and a volume of 3.6 ml?
Answer = 69 g
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Units of Measure
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Time and Temperature
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Time is measured in seconds
Temperature is actually a measure of the kinetic
energy of a substance (how quickly the
molecules that make up a substance are
moving)
Temperature is measured in Kelvin or Celsius
We will use Celsius
Water freezes at 0oC and boils at 100oC
Body temp is about 37oC
Kelvin (K)
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Kelvin (K) is mostly used in Chemistry and Physics
O K is called absolute zero.
Absolute zero is when molecular motions stops. It
is impossible to get anything colder than absolute
zero. That means that there are no negative
temperatures in Kelvin.
To convert between Celsius (C) and Kelvin (K):
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C + 273 = K
K – 273 = C
Water boils at 373 K and freezes at 273 K
Odds and Ends
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Accuracy: how close your value is to the
actual value- this gets better with practice.
 Accuracy
depends on U
Precision: indicated by the number of
significant digits and depends on the
quality of the measuring instrument.
 Significant digits are the numbers off the
measuring device.
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The Basics
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Planet – A large body in orbit around a star. Must be mostly
have a
path.
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Examples: Our moon, Ganymede, Io, Europa.
Solar System – The Sun, planets, their moons and other bodies that orbit
the Sun.
Our Sun is a star.
– A massive, gaseous body held together by gravity and generally
emitting light.
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Planets in our solar system (9): Mercury, Venus, Earth, Mars, Jupiter, Saturn,
Uranus, Neptune, (Pluto).
– A body orbiting a planet.
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and
Normal stars generate energy by nuclear reactions in their interiors.
– The path in space followed by a celestial body.
ALL celestial bodies rise in the East and set in the West. A result of the
rotation of the Earth.
– The drift of a planet westward against the
background of stars.
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Normally planets shift eastward because of orbital motion.
The planet does NOT actually reverse its motion. The change in direction is
caused by the change in position from which we view the planet as the Earth
overtakes and passes it.
Solstice versus equinox
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- the path traced by the sun as it crosses
the celestial sphere.
Solstice (winter and summer) – The beginning of winter and
summer. The solstice occurs when the sun is at its greatest
distance north (in June) or south (in December) of the
celestial equator.
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Summer solstice – Near June 21
Winter solstice – Near December 21
– The time of the year when the number of
hours of daylight and night are approximately equal. The
spring and fall (vernal and autumnal) equinoxes mark the
beginning of spring and fall seasons.
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Spring (vernal) equinox – March 21 - start of spring
Fall (autumnal) equinox – Near September 21 - start of autumn
Eclipses
One will occur in Sept. - Visible in S. Am.
 Occurs when the moon happens to lie
exactly between the Earth and Sun, or
when the Earth lies exactly between the
Sun and Moon.
 All three bodies will be in a straight line
 There are two types of Eclipses
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Lunar Eclipse
 Solar Eclipse
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Eclipses
Lunar Eclipse – Occurs when the Earth
passes between the Sun and the Moon,
casting its shadow on the moon. (Fig 1.15)
 Solar Eclipse – Occurs when the Moon
passes between the Sun and the Earth,
blocking our view of the Sun. (Fig 1.14)
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Ellipse
Do not confuse an ellipse with an eclipse.
 An ELLIPSE is a geometric shape, similar
to a circle, but elongated in one direction.
 The path of the Earth’s orbit around the
Sun is in the shape of an ellipse.
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Historical Astronomers
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Ptolemy
Copernicus
Tycho Brahe
Johannes Kepler
Galileo Galilei
Newton
Doppler
Hubble
Herschel, William
LaPlace, Pierre-Simon
Halley, Edmund
Cassini, Giovani
Hipparchus of Nicaea
Hertzsprung