Download The Big Bang

Dr. White
Mrs. Griffin
ASTRONOMY
Learning from Light: The Big Bang
Objective: Explain the origin of the universe
according to the Big Bang theory
http://www.rug.nl/museum/tentoonstellingen/archief/ruimte
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A. Electromagnetic radiation is energy released by
stars in the form of waves.
1. Many types, together known as electromagnetic
spectrum (visible light is only 1 kind)
2. Types have different wavelengths
http://www.yourdictionary.com/images/ahd/jpg/A4wavele.jpg
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3. Wavelength varies indirectly with energy content
4. ROYGBIV, which is more energetic red or violet?
http://www.spacetoday.org/images/DeepSpace/Telescopes/GreatObservatories/Chandra/ChandraSpectrum.jpg
Observe an exploded star at different wavelengths. Vis.
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B. Astronomers use a spectroscope to study types of star
spectra (sing. spectrum)
1. Continuous spectrum- source emits light of all wavelengths
2. Emission spectrum- source emits some wavelengths
3. Absorption spectrum- cool gases absorb some wavelengths
depending on their composition
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Define galaxy and describe the various types
A. Galaxies are clusters of millions to billions of stars
B. Ours is the Milky Way
C. Likely 50-100 billion galaxies
D. Many shapes exist
http://antwrp.gsfc.nasa.gov/apod/image/0402/skymt_payne_big.jpg
http://www.myastrologybook.com/[email protected]
The Universe
A. Includes all visible galaxies
B. Age thought to be 10-20 billion years old
C. ‘Big Bang’ is best theory of formation
1. Initial hot explosion
2. Gases & dust cooled & condensed locally into
planets, stars, & galaxies
3. Material still spreading out from explosion
4. Best evidence includes red shift of light from
other galaxies
The Universe
• Light from distant galaxies all appear to
have a longer wavelength than expected.
• The most obvious reason is that they are
moving away from us as they emit light so
the light looks ‘stretched’ to us.
Longer wavelengths
Shorter wavelengths
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The Moon
A look at our nearest
neighbor in Space
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It’s Just A Phase
• Moonlight is reflected
sunlight
• Half the moon’s surface is
always reflecting light
• From Earth we see
different amounts of the
Moon’s lit surface
• The amount seen is called
a “phase”
Waxing and Waning
•
•
•
•
•
•
•
•
•
New moon
Waxing Crescent moon
First Quarter moon
Waxing Gibbous moon
Full moon
Waning Gibbous moon
Third Quarter moon
Waning Crescent moon
New moon
last (third)quarter
waning Moon
moon orbit`s
earth
SUN
gibbous moon
crescent
earth
full moon
new moon
gibbous moon
crescent
waxing Moon
first quarter
The Reason For the Seasons
Seasons Misconception
• Many people carry the misconception that the
seasons are due to the distance of the Earth from
the Sun. However, consider the following facts:
– The Earth’s orbit around the Sun is nearly a perfect
circle. The Earth is slightly closer to the Sun in January
and farther from the Sun in July.
• Perihelion (closest to the Sun) is around January 3 when Earth
is about 91,405,436 miles from the Sun.
• Aphelion (farthest from the Sun) is around July 4 when Earth is
about 94,511,989 miles from the Sun.
What Causes Earth’s Seasons?
• Earth’s axis is tilted 23.5 degrees – it always points in the
same direction (Polaris, the North Star) as we orbit our Sun
once a year
• This tilt causes the hemispheres to alternate in the amount
of our Sun’s light and heat they receive through the year
http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml
Northern Hemisphere Summer
More daylight hours, more direct sunlight
http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml
SOLSTICES
SUMMER, JUNE 21
WINTER, DECEMBER 21
Where are the
overhead rays of the
sun on these days?
Which parts of the
earth are in darkness
and light? For how
long?
Notice these four
important parallels.
Where do they occur?
Why?
Tropic of Cancer at 23.5º N
Tropic of Capricorn at 23.5º S
Arctic Circle (66.5 º N)
Antarctic Circle (66.5º S)
EQUINOXES
VERNAL, MARCH 21
AUTUMNAL, SEPTEMBER 21
Rotation of the Earth
• Rotate west to east or ‘counter-clockwise’
(when viewed from the North Pole)
– sunset and sunrise
• Rotation period is 24 hours per solar day
(23 hours 56 minutes with respect to other
stars)
Revolution of the earth
• Period of revolution is 365.25 solar days
• Elliptical orbit (plane of the ecliptic)
Perihelion -
Aphelion -
91.5 million
miles
94.5 million
miles
(Jan. 4)
(July 5)
93 million miles average distance
Time
Standard Time
The International Date Line
Daylight Savings Time
Year = 365 1/4 days or 365 days 5 hrs. 48 min.
45.685 seconds
Solar Day = 24 hours on average. Changes
slightly with the elliptical orbit around the sun.
Standard Time
360o / 24 hr. = 15o standard zones (7.5o E and W from standard
meridian)
International Date Line
Cross W to E - gain day; E to W - lose day
International Date Line
A day is 24 hours,
but a date lasts for
48 hours!
At any given time on earth,
except Greenwich noon,
there are two dates on the
planet.
The new date starts at the IDL when midnight crosses the
IDL and moves westward around the planet for 24 hrs.
displacing the old date. Then it fades out as the “old” date
for 24 hrs.
Key Points
•
•
•
•
Size and Shape of Earth.
Latitude and Longitude
Explain the basic earth-sun relationships.
Equinoxes, solstices and the relationship among
–
–
–
–
seasons
the latitude of the sun’s direct rays, and
the intensity of solar radiation received
changes in Daylight and Darkness
Barycenter & Precession
• Precession – movement (wobble) of the axis of rotation of
an astronomical body (the axis slowly traces out a cone);
for the earth it occurs once every 26,000 years of earth
motion.
Precession “Wobble
Cone” (P)
Nutation “Wobble Cone
Wiggle” (N)
Rotational Axis {R}
Barycenter
• Barycenter – common center of mass around which 2
bodies revolve.
Hubble’s Law
H = v/d
Stars having a small d show a small v
Stars having a large d show a large v
OR
Nearer stars are moving away more slowly (smaller red shifts) More
distant stars are moving away more rapidly (larger red shifts)
Kepler’s Laws Of Planetary
Motion
• In astronomy, Kepler's laws of planetary motion are
three scientific laws describing orbital motion, originally
formulated to describe the motion of planets around the
Sun.
• Kepler's laws are:
– The orbit of every planet is an ellipse with the Sun at one of the
two foci.
– A line joining a planet and the Sun sweeps out equal areas during
equal intervals of time.
– The square of the orbital period of a planet is directly proportional
to the cube of the semi-major axis of its orbit.
1st
2nd
3rd