Download Ch 28-31

Ch 28-31
Earth’s Role as a Body in Space
Lesson 1
Earth’s Position and Movement
Through Space
(You Are Here →)
Earth’s Position in Space
What is Earth’s position within the
hierarchy of the universe?
A. Earth’s Position in the Universe
Earth’s Position in the Universe…
●
●
●
●
●
●
Earth →
Solar System (3rd planet from Sun) →
Milky Way Galaxy (the Orion Arm) →
Local Group (about 40 galaxies)
Supercluster (Virgo)
Universe!
http://www.atlasoftheuniverse.com/
Earth’s Motion through
Space
How is Earth’s motion related to
the origin of the galaxy and its
solar system?
The Origin of Our Expanding
Universe
1. The Big Bang Theory
– universe began as
a point & has been
expanding ever
since
Notice how the galaxies
in each successive
picture are moving
apart from the
singularity?
en.wikipedia.org
The Origin of the Milky Way
2. Astronomers hypothesize that
the galaxy began as…
A rotating, spherical
cloud in space …
a. Our solar system
continues to orbit the
center of the Milky Way
because… it
developed in the
plane of the disk
that orbited the
central nuclear
bulge of stars
http://www.google.com/imgres?imgurl=http://casswww.ucsd.edu/archive/public/tutorial/images/mw.jpg&imgrefurl=http://casswww.ucsd.edu/archive/public/tutorial/MW.html&usg=__
The Milky Way
●http://www.atlasoftheuniverse.com/
The Milky Way
●
http://www.astropix.com/HTML/D_SUM_S/MILKYWAY.HTM
b. A Diagram – Milky Way Galaxy Formation
●
●
http://lcogt.net/education/article/milky-way-galaxy
http://astronomy.nju.edu.cn/~lixd/GA/AT4/AT423/HTML/AT42304.htm
The Origin of the Solar System
3. Our solar system began when…
…a rotating, interstellar cloud of gases
(nebula) collapsed (due to gravity) &
formed a sun & orbiting planets
a. Earth orbits the Sun because
… it was located outside the center of
the spinning nebula
The Eagle Nebula
A solar nebula
is…
A disk of dust
& gas (mostly
hydrogen &
helium) that
can form a star
and planets
http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-astro-nebula.html
A Diagram - Origin of the Solar
System (Draw this!)
• http://csep10.phys.utk.edu/astr161/lect/solarsys/nebular.html
Early stages of
rotating cloud of
gas & dust
Rotating cloud
flattens as it
contracts
Sun forms in center & planets form within flattened
cloud. Radiation from the Sun drives away the
“atmosphere” of hydrogen gas from the inner planets.
Star formation has NEVER
been observed! (just
hypothesized!)
Lesson 2
Kepler’s Laws and
Earth’s Orbit
Think About It…
How would Earth be different
if its orbit was more oval
than circular?
Focus Question
How do Kepler’s laws
describe Earth’s orbit?
Kepler’s Laws (Introduction)…
Johannes Kepler, working
with data painstakingly
collected by Tycho Brahe
(from 1576-1601) without
the aid of a telescope,
developed three laws
which described the
motion of the planets
across the sky.
http://www.nmspacemuseum.org/halloffame/images.php?image_id=131
Unless otherwise noted, the info on the slides on Kepler’s laws was taken from the
following website: http://hyperphysics.phy-astr.gsu.edu/hbase/kepler.html
1. Kepler’s First Law…
The Law of Orbits: All planets move in elliptical orbits,
with the sun at 1 focus.
a. An ellipse is … oval shape centered on 2 points
instead of 1 point.
b. The orbital period of a planet is … how long it
takes for it to travel a complete orbit around the
Sun.
c. We call this a year!
Examples of Ellipse Eccentricity
Planetary orbit
eccentricities
Mercury
.206
Venus
.0068
Earth
.0167
Mars
.0934
Jupiter
.0485
Saturn
.0556
Uranus
.0472
Neptune
.0086
Pluto
.25
2. Kepler’s Second Law…
The Law of Areas: A line that connects a planet to the Sun
sweeps out equal (=) areas in equal (=) times.
a. Earth sweeps out a longer path when it is closer to
the Sun.
b. Earth moves fastest when it is closest to the Sun.
http://phet.colorado.edu/en/s
imulation/my-solar-system
http://www.mathacademy.com/pr/prime/articles/kepler/index.asp
3. Kepler’s Third Law…
The Law of Periods: The square of the orbital
period of any planet is proportional to the
cube of the semi major axis of its orbit.
a. P² = a³ (P = orbital period = unit of time in Earth
yrs, a = length of the semi major axis)
b. If you know the distance of a planet to the Sun,
you would be able to figure out its… orbital
period.
c. Basically… The closer a planet is to the Sun, the
shorter its orbital period is.
Kepler’s Third Law
Kepler’s Third Law
●
●
Another way of thinking about this is that
…The closer a planet’s orbit is to the
Sun, the shorter its year will be. (Write
that in the margin!)
For Examples: Appendix J on p. 921…
●
●
●
●
●
Mercury’s year is 88 (Earth) days
Venus’ year is 224 (Earth) days
Earth’s year is 365 (Earth) days
Mars’ year is 686 (Earth) days
Neptune’s year is 60,189 (Earth) days!!
Kepler’s Laws Short Video
https://www.youtube.com/watch?v=5a2mcE-tzKE
… a very short clip with a nod to Star Trek
https://www.youtube.com/watch?v=x3ALuycrCwI
… a longer clip (14 minutes) covering the history
behind Kepler’s work and the development of
the laws named after him
Practice! Orbit Eccentricity
The eccentricity of an ellipse can be defined as the ratio
of the distance between the foci to the major axis of the
ellipse.
● The more eccentric an orbit, the more of an oval it is.
● The eccentricity is zero for a circle.
● Of the planetary orbits, only Pluto has a large
eccentricity.
●
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=175
Mini-Lesson 2: Barycenter
The True Center of the Solar
System!
Mini Lesson 2: Barycenter and
Earth’s Orbit…
Barycenter is …the center of
mass between a planet and
the Sun.
1. The law of universal gravitation states
that…
●
every pair of bodies in the
universe attracts each other
with a force related to…
● …mass (the more mass
they have, the stronger the
pull) AND
● …distance (the farther
apart they are, the weaker
the pull)
Barycenter, Universal Gravitation,
and the Wobbling Sun
●
The Sun wobbles around in its orbit
because…
●
… the 8 planets are pulling on it as they orbit
it!
The Wobbling Sun (Draw this
on your Study Guide!)
Barycenter and Earth’s Orbit…
2. A planet, such as Earth, actually orbits…
its barycenter with the Sun
3. The Sun orbits …
the barycenter of the solar system. (It is NOT
stationary in the sky as planets orbit it.)
4. Draw this!
See next slide.
http://www.barewalls.com/pv-605547_Barycenter-Diagram.html
Modeling Barycenter
– http://spaceplace.nasa.gov/barycenter/
Lesson 3
Earth’s Rotation
Day and Night
Earth’s Slightly Squashed Shape
Think About It…
How would Earth’s day be
different if it did not rotate
on its axis?
Focus Questions…
What causes the day and
night cycle?
What motion and force
causes Earth’s slightly
squished shape?
Earth’s Rotation Causes Day and Night
1. Earth’s axis is…
o
… the imaginary line
that goes through
the N & S poles.
2. Day and night are
caused by…
o
… the rotation of
Earth on its axis spinning towards &
away from the Sun.
(23.9345 hrs)
3. When the Sun “rises” …
▪ … we are actually spinning TOWARDS it
▪ Sun “rise” on Myrtle Beach (looking
towards the east over the Atlantic Ocean)
4. When the Sun “sets” …
▪ … we are actually spinning AWAY FROM it
▪ … sun “set” over Ft. Lauderdale, FL
(looking towards the west while on the
Atlantic Ocean)
Think About It… Why are there 24
hours in a day?
Earth spins…
15 degrees each
hour
There are 360 degrees
in a circle (the
circumference of
Earth).
360 divided by 15 is 24
so there are 24
hours in a day!
http://huntingtonastro.wikispaces.com/file/view/earth-rotation.png/199559520/earth-rotation.png
Still Thinking About It…
The exact amount of time it takes Earth to
spin one time on its axis is…
●
23.9345 hours (Write this in the margin!)
If an Earth day was 5832.5 hours long (like
that of Venus!) then…
●
●
It would take 243 days for Earth to spin one
time on its axis!
Our day and night would be much longer!
(And it would get really hot and really cold!)
Earth’s Rotation Causes Its
Slightly-squished Shape…
1. What motion causes
Earth to take the
shape of an oblate
spheroid?
Earth’s rotation
2. What force causes
the Earth’s mass to
move outward from its
center at the equator
as Earth rotates?
centrifugal force
Earth’s Rotation and Its Shape…
http://www.cleonis.nl/physics/phys256/equatorial_bulge.php
Earth’s Rotation Causes Its
Slightly-squished Shape…
3. There is a slight
bulging at the
equator
and a slight squishing
at the poles.
4. This causes the
circumference at the
equator to be slightly
larger than that of the
poles.
Earth’s Rotation and Its Shape…
5. Draw this →
Notice the
equatorial diameter
is 42 km more
than the polar
diameter!
Simulation: http://www.cleonis.nl/physics/phys256/equatorial_bulge.php
Lesson 4
The Seasons
Think About It…
During which month is Earth
closest to the Sun?
Focus Question (and Answer!)…
What causes the seasons?
The tilt of the Earth on its axis
as it revolves around (orbits)
the Sun.
Earth’s Orbit and Seasons…
1. The ecliptic is…
● …the plane on
which Earth
orbits around
the Sun
http://en.wikipedia.org/wiki/Ecliptic
Earth’s Orbit and Seasons…
2. The tilt of Earth’s axis relative to the ecliptic
is 23.5 degrees.
http://republicanredefined.com/2010/03/02/chile-quake-shifted-earths-axis-and-made-days-shorter/
The Tilt of All the Planets!
http://climatechangepsychology.blogspot.com/2011/07/chris-colose-milankovitch-cycles.html
http://www.exploratorium.edu/ancientobs/chaco/HTML/TG-shadows.html
3. Draw The Seasons! P. 760
Earth’s Orbit and the Seasons!
4a. What causes summer in the northern
and southern hemispheres?
●
when it is tilted toward the Sun during Earth’s
orbit
4b. What causes winter in the northern and
southern hemispheres?
●
when it is tilted away from the Sun during
Earth’s orbit
Earth’s Orbit and Seasons…
5 . The seasons in the northern and
southern hemispheres are opposite each
other because…
●
When 1 hemisphere is tilted towards the Sun,
the other is tilted away from it
http://www.onlytoptens.com/wp-content/uploads/2011/08/top-10-documentaries-march-of-the-penguins.jpg
Seasons - Perihelion
6. Earth is closest to the Sun in January
a. Our winter!
b. This is called perihelion
http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=2517
Seasons - Aphelion
7.
And farthest from
the Sun in July a. our summer!
b. This is called
aphelion
But in Antarctic it is
winter (which
makes it tough on
the penguins!)
Lesson 5
Changes in The Seasons –
Precession and Nutation
Think About It…
What would happen to the
average temperatures during
our winter if Earth was tilted
MORE on its axis ?
Focus Question…
What circumstances can
bring about a long term
change in the seasons?
Precession
Precession is…
● the wobble in Earth’s
rotational axis.
1. One full cycle of
precession takes…
● 26,000 years!
2. The force that causes
precession is…
● the sideways pull of
the Moon & Sun on
the Earth’s bulging
equator.
The Moon’s orbit is tilted 5° which
over time pulls on Earth…
http://earthsky.org/astronomy-essentials/what-is-the-ecliptic
Precession…
3. Our current north
star is…
● Polaris
● In about 12,000
years, our new
north star will
be…
● Vega
http://www.wwu.edu/skywise/a101_precession.html
Precession and Our Seasons…
4. Draw this!
Aphelion
Perihelion
Winter
Summer
July
In 14,000 yrs
January
Aphelion
Perihelion
Summer
Winter
July
Present
January
http://earth.usc.edu/classes/geol150/stott/variability/orbitalchanges.html
A New North Star and Our
Seasons…
5a. Winters in the N. hemisphere will be…
●
●
in June, July, and August
It will be colder here because Earth will be
farthest from the Sun.
5b. Summers in the N. hemisphere will be…
●
●
in December, January, and February
It will be warmer here because Earth will be
closest to the Sun.
Precession Clips…
●
http://www.youtube.com/watch?v=0qHjtp4cdCA
●
●
3 minute clip: demonstration of precession
http://www.youtube.com/watch?v=Dw4Xhw4q4ec
●
Very short model of precession
http://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.html
Nutation…
Nutation is…
… a change in the
angle of tilt of Earth’s
axis
1. Present tilt of Earth’s
axis is 23.5°.
2. The tilt can vary from
22.1° to 24.5 °.
http://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_99/bilskemp/natural_variability.html
Nutation…
3a. If the angle of tilt
decreased to 22.1…
there would be less of a
temperature difference
b/tw seasons.
3b. If the angle of the tilt
of Earth’s axis
increased to 24.5…
there would be more of a
temperature difference
b/tw seasons.
4. Draw
Nutation
p. 373
Lesson 6
Tides
Think About It… Tides Lesson
How would Earth’s oceans be
affected if Earth did not
have a moon?
Focus Question…
What forces and heavenly
bodies cause the tides?
Tides…
Tides are caused by…
●
the gravitational attraction among Earth,
the Moon, and the Sun.
1. Tides are…
the periodic rise and fall of sea level.
a. High tide…
● highest
level to which the water rises
b. Low tide…
● lowest
level of the water
http://www.amusingplanet.com/2012/03/tides-at-bay-of-fundy.html
Tides: Bay of Fundy…
Low
Tide
High
Tide
http://www.srh.noaa.gov/jetstream/ocean/fundy_max.htm
http://www.listentothewind.com/fundy-bay-drive-and-sights/
Bay of Fundy National Park, New
Brunswick, Canada
High Tide
Same Rocks…
Low Tide
Bay of Fundy: A Perspective
Mr. Koeval on the Shore!
Tide Coming In…
A bit more…
Notice the water level on the
rocks…
Tide’s In!
2. What forces & heavenly
bodies cause the tides?
●
●
●
gravitational pull of
Moon on oceans
facing it causes high
tide
“centrifugal swish”
oceans facing away
from Moon experience
less of a pull (high tide)
The sides of Earth NOT
directly facing toward
or away from the Moon
experience low tide.
The Cause of
Tides…
The Cause of Tides…
3. What motion causes tides at location to
change every 6 hours?
● Earth’s rotation on it’s axis
4. The times of tides vary each day
because the moon orbits the Earth
every 28 days
Tide Simulation:
http://astro.unl.edu/classaction/animations
/lunarcycles/tidesim.html
http://loneswimmer.com/2010/08/23/tides-for-swimmers-part-1-theory/#jp-carousel-535
Spring Tide…
●
●
Twice a month, the Earth, Moon, & Sun
align (line up) causes the Moon & Sun to
pull together on Earth’s oceans.
Higher high tides / lower low tides
Neap Tide…
●
●
Twice a month,
the Earth, Moon,
& Sun will form
a right angle
which causes
the Moon & Sun
to pull from
different
directions on
Earth’s oceans.
Evens the tides
http://www.yourdictionary.com/neap-tide
http://csep10.phys.utk.edu/astr161/lect/time/tides.html
Compare the Spring Tides & Neap Tides
http://mail.colonial.net/~hkaiter/Moon_Phases_Tides.html
5. Draw the Tides… (as seen from
above the North Pole!)
Lesson 7
Energy Reactions
Think About It…
Is it possible to make electricity
by using the same process
that powers the Sun?
Focus Question…
What process powers the Sun
and what forms of Energy
does that process produce?
What is the difference between
fusion, fission, & combustion?
A Little Bit About the Sun…
How many Earths could be lined up edge to
edge to fit across the Sun?
●
●
109 (and 1 million Earths would fit IN it!)
Pic on next slide…
The Sun makes up…
●
99% of the mass of the solar system!
A pair of dice with the density of the Sun…
●
would weigh 2 pounds!
The solar interior is made of…
… plasma (one of the 4 states of matter)
Great Sun Pic from NASA…
Fun Sun Facts by NASA…
●
https://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun
BTW… Our Sun is basically a stable hydrogen bomb – or a giant fusion reactor!
Fusion
1. Fusion is…
– the fusing of smaller, lighter hydrogen atoms to
form a larger, heavier helium atom (which
releases energy)
Fusion…
a. Fusion occurs in the stars! (our Sun)
bi. During fusion, the two atoms that fuse to
form a helium atom are the H isotopes
deuterium & tritium
Fusion…
b. During Fusion (continued)…
ii. The mass that is lost when
two hydrogen nuclei fuse to
form helium …
●
… gets converted into energy
iii. The theory of special relativity
(e = mc²) by Albert Einstein
relates mass to energy!
http://www.nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-bio.html
Fusion Reaction – Draw this!
http://www.teachertube.com/viewVideo.php?video_id=174422
Fusion and Electricity Production…
China claims fusion reactor test
a success
Government hopes fusion
provides clean, limitless
energy source …
●
“BEIJING - Scientists on
Thursday carried out China's
first successful test of an
experimental fusion reactor,
powered by the process that
fuels the sun, a research
institute spokeswoman said.
●
China, the United States and
other governments are pursuing
fusion research in hopes that it
could become a clean,
potentially limitless energy
source.
●
Fusion produces little
radioactive waste, unlike
fission, which powers
conventional nuclear reactors.”
http://www.msnbc.msn.com/id/15043462/
updated 3:22 p.m. ET, Thurs., Sept. 28, 2006
Fission
2. Fission is…
– splitting of bigger, heavy atoms (like uranium
or plutonium) into smaller, lighter atoms
2a. Fission Differs From Fusion…
a. Fission differs from
fusion in that…
Fission is SPLITTING
atoms, not FUSING
atoms.
The Radioactive Boy Scout
is a warning about
investigating fission in
your backyard shed!
http://www.dangerouslaboratories.org/radscout.html
2b.Fission
2b. Fission
is used
on Earth …
– in nuclear
power plants
& submarines
(to generate
electricity)
www.pollutionissues.com
Fusion and Fission: Nuclear Reactions
2c. Fusion and fission are nuclear reactions
because…
➢ …the nuclei of atoms are fusing (in fusion) OR
splitting (in fission). (Remember… That’s the
center part of the atom where protons and
neutrons are located)
➢ New atoms are made in both types of reactions.
Fission – Draw this!
http://en.wikipedia.org/wiki/Combustion
Combustion
3. Combustion is… burning of a fuel in presence
of O2 (oxygen) to produce energy (heat & light)
a. It is a chemical reaction which recombines atoms.
(FUEL)
Methane
Combustion used in…
Vehicles
Fireplaces
Power Plants
(Belews Creek)
http://www.news-record.com/news/article_73ce9953-637d-5c7c-bfdd-49fee0a35773.html
http://en.wikipedia.org/wiki/Volkswagen_New_Beetle
Power Plants…
3c. In the
approximately 1,600
power plants in our
country that use
combustion, the fuels
used are mostly…
✓ coal & natural gas
✓ Belews Creek is
coal-fired.
Combustion – Draw it!
Fuel
+
oxygen
→
carbon
dioxide
+ water
Lesson 8
The Sun’s Energy
Think About It…
How does the Sun harm
living things?
(What types of energy
from the Sun are
harmful?)
One of the Effects of Ultraviolet
Radiation!
Focus Question…
How are the harmful forms of
radiation from the Sun
deflected away or filtered so
that they don’t reach living
things?
The Sun’s Energy…
1. Electromagnetic radiation consists of …
● … electric & magnetic disturbances that
travel through space as waves.
2. The electromagnetic spectrum…
● …organizes forms of EM energy by
wavelength
3. The Sun produces electromagnetic radiation
across the spectrum…
● radio waves, microwaves, infrared energy
(heat), visible light, ultraviolet radiation, xrays, & gamma rays
The Electromagnetic Spectrum…
4. The shorter the wavelength, the more harmful
the energy!
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
The Ozone Layer…
5. Which gas blocks
ultraviolet radiation
from the Sun?
● Ozone (O3)
a. It is found in the
stratosphere.
b. Chlorofluorocarbons
(CFCs) damage O3.
c. These are found in
aerosols, coolants, &
cleaners.
http://mmedia.pl/ozone-layer-diagram-for-kids
http://www.theozonehole.com/ozonedestruction.htm
Ozone and CFCs: Animation 1
http://www.theozonehole.com/ozonedestruction.htm
Ozone and CFCs: Animation 2
Solar Wind and Earth’s Magnetic Field
1. Solar wind is…
● …a supersonic plasma (Remember,
that’s charged particles or ions) that
flows outward from Sun at high speeds
&…
● …bathes planets in a flood of highenergy particles. (Which isn’t very good
for us!)
Solar Wind
What protects us from the deadly solar wind?
http://www.cnn.com/2013/06/27/world/europe/star-trek-shield
http://www.youtube.com/watch?v=zoK-tPS_bYE
http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=10984
Solar Wind and Earth’s
Magnetic Field…
2. Earth’s magnetic field protects us from the
solar wind by…
●
deflecting these particles and trapping them in
two huge rings (Van Allen belts)
http://www.redorbit.com/education/reference_library/space_1/solar_system/2574610/van_allen_radiation_belt/
Earth’s Magnetic Field…
3. Draw and label this!
The Strength of Earth’s Magnetic
Field…
●
●
●
Our magnetic field is decreasing by 5% a
century
Jupiter has a super-strong magnetic field
What would happen if our magnetic field
was much stronger? Take a look…
https://www.youtube.com/watch?v=etPXBm
0zRvM
Solar Wind and Earth’s Magnetic
Field…
4. The auroras are
created when…
● … high-energy
●
particles in Van
Allen belts collide
with gases in
Earth’s atmosphere
& give off light
See next slide…
The Auroras…
http://www.lovethesepics.com/2011/02/24-amazing-auroras-aurora-borealis-aurora-australis/
Lesson 9
Energy For Earth…
Think About It…
What would happen to Earth if
the Sun were turned off today?
Focus Question…
How does the Sun’s energy
warm Earth’s surface and
atmosphere?
Energy For Earth…
1. Radiation is …
transfer of
energy through
space by EM
waves (visible
light, ultraviolet
radiation, &
other)
http://virtualskies.arc.nasa.gov/weather/images/2b1.png
Energy For Earth…
1a. The Sun’s energy reaches Earth by the
process of radiation.
1b. About 50 % of the Sun’s energy is
absorbed by Earth’s surface.
1c. Remember –
ozone blocks
most of the UV
radiation.
http://ossfoundation.us/projects/environment/global-warming/earths-radiation-budget
Differential Heating…
1d. Which heats up and cools down
more slowly – water or land?
● This is called differential heating.
● This is what moderates the climate
in coastal areas.
● In winter, the ocean acts like a
giant heater and in summer, the
ocean acts like a giant air
conditioner.
Differential Heating and North
Carolina…
Our moderate coast – The Outer Banks!
2. Conduction is…
the transfer of energy
that occurs when
molecules collide
a. Air molecules just
above Earth’s
surface are warmed
by conduction.
b. Energy moves from
your hand to your
desk. Why?
Energy for
Earth…
Heat waves over hot sand!
http://visualparadox.com/wallpapers/dryseason1600.htm
Energy for Earth…
3. Convection is…
●
a.
b.
c.
the transfer of
energy by the flow of
a heated substance
Warm air will rise.
When the warm air
gets high enough, it
cools and sinks.
This creates a
convection current.
http://avstop.com/ac/fig5-9.jpg
Energy For Earth…
Copy the diagram your teacher
draws on the board!
Energy for Photosynthesis…
1.
2.
3.
4.
5.
During photosynthesis,
solar energy is
transformed into
chemical energy (food).
This occurs in plants,
algae & some bacteria.
For this to occur, there
must be water, CO2,
Energy source: sunlight.
In plants, this occurs in
chloroplasts.
http://abhsscience.wikispaces.com/Photosynthesis+TD
6. Draw Photosynthesis…
Food From the Sun!
http://wowk.images.worldnow.com/images/19108684_BG1.jpg