“Far better is it to dare
mighty things, to win
glorious triumphs, even
though checkered by
failure than to rank with
those poor spirits who
neither enjoy much nor
suffer much, because
they live in a gray
twilight that knows not
victory nor defeat.” –
Theodore Roosevelt
The Solar System
Modeling the Solar System
Geocentric Model aka Ptolemaic Model
Ancient Greeks
• Earth is at the center of the Universe.
• The Earth stood still & never moved.
• Stars are on a separate sphere orbiting the
Earth
was named after the philosopher Claudius Ptolemy
who lived circa 90 to 168 A.D.
• 7 objects moved differently in the sky known as
the “wanderers” or planetai. Sun, Moon, Mercury,
Venus, Mars, Jupiter & Saturn
Ptolemy
» Designed an updated model of the
geocentric model.
» The planets orbit in circles around the
Earth & also travel in circles on the
orbit.
Both the Earth moving (spinning)
and gravity affect the wind. But the
primary cause of the wind is
temperature differences, not the
moving of the Earth or gravity.
Heliocentric Model
Nicholas Copernicus
» Earth revolves around the Sun.
» Moon revolves around the Earth.
» Earth rotates on an axis.
» Planets revolved around the Sun.
» Planets have circular orbits.
If the Earth suddenly stopped spinning, everything not attached
would go flying off to the east, parallel to the surface of the
Earth. The speed would depend upon your latitude. Only the
people at the poles would be safe. You wouldn't go flying off into
space because the 1000 mph maximum (at the equator) isn't
enough to overcome gravity, which would still be present. If you
survived, the resulting six month day and six month night would
probably take care of you pretty quick.
Tycho Brahe died of a ruptured bladder because he refused to excuse himself at a banquet as
it would have been rude.
Tycho had his nose cut off in a duel. He
wore a gold and silver prosthetic nose
Tycho Brahe & Johannes Kepler
 Brahe charted the motions of celestial
bodies before telescopes.
 Mathematician Kepler used Brahe’s
data to form the Laws of Planetary
Motion:
1. The path of a planet around the Sun
is an ellipse.
2. A planet will travel faster
when it is closer to the Sun
& cover a greater distance
than when it is farther away.
3. The more distant the
planet’s orbit is from the
Sun, the longer it takes to
make a single revolution.
Revolutionary Periods
Mercury = 88 Earth days
Earth = 365.25 days
Jupiter = 11.86 Earth years
Pluto = 248 Earth years
Nebula Theory: Formation of the Solar System
1. More than 4.6 billion years ago, the solar system
was a cloud (nebula) fragment of gas, ice, &
dust.
The Sun shifts it's magnetic field every 11 years, and it has
already happened for this solar cycle. The Earth's magnetic
field flip is much more erratic and has happened
approximately 25 times in the last 5 million years. It's been
about 740,000 years since the last flip, however, so we're
long overdue. There is evidence that we may be heading
towards a reversal (the dipole magnetic field is weakening
and the higher order terms are increasing), but we can't
predict when it would happen. Depending upon how
quickly the field reversal happens, it could cause problems
for things like electric power lines and oil pipelines, and if
the field goes to near zero, it might cause a higher
background radiation at the ground, but there is no
evidence that previous reversals have had any major
biological effect. The forces due to the interaction of the
solar and terrestrial magnetic fields are only very small
perturbations.
2. Gradually, this cloud fragment contracted into a
large, tightly packed, spinning disk. The disk’s
center was so hot & dense that nuclear fusion
reaction occur forming the Sun.
Planetary objects and
satellites do not, as a rule,
blow up. If the Moon did,
you could expect large
chunks of it to hit the Earth
at pretty high speeds. Very
messy. After a while, the
survivors might see a very
pretty ring of debris about
the Earth.
Parachutes use air resistance to slow down a descent.
Since there is no air on the Moon, they would be
completely ineffective. The parachute would fall at the
same rate as a rock.
3. The rest of the material in the disk cools
enough to clump into scattered solids.
It is estimated that within the entire Universe there are
more than a trillion galaxies (the Milky Way itself
contains 100 billion stars). This means that there are
probably about 100 (to the 22nd power) stars in the
entire cosmos.
Our sun is a second or possibly 3rd generation star
A new star is born in our galaxy every
18 days
Scientists believe that we can
only see about 5% of the matter in
the Universe. The rest is made up
of invisible matter (called Dark
Matter) and a mysterious form of
energy known as Dark Energy.
4. Finally, these clumps collided & combined to
become the planets, dwarf planets, comets,
asteroids, etc.
» The planets all orbit on the same plane called
the ecliptic.
» The 8 planets occasionally line up in a straight
line.
Astronomers have discovered more than 150 planets outside our solar
system, ranging from 100 to 1,000 times Earth's mass.
Gravity and the Solar System
Galileo
The sun emits
enough energy to
melt a bridge of
ice 2 miles wide, 1
mile thick, and
extending the
entire way from
the Earth to the
Sun, in one
second.
» Believed that objects fall to the
Earth at the same rate despite the
object’s weight.
»Air resistance slows down falling
objects.
The Sun consumes about 600 million tons of hydrogen per second. (That's
6 x 108tons.) This would mean the Sun consumes the mass of the Earth in
about 70,000 years.
The Earth and the Moon eventually will be "locked" together with
each only having one side constantly facing the other. (Right now the
same side of the Moon faces the Earth, but all sides of the Earth see
the Moon. In the future this will not be true!) Life on Earth will be
quite different then, but this won't occur for billions of years yet.
When it does occur, the Moon's orbit will be 50% larger than it is now,
and a month will be about 50 days.
Sir Isaac Newton
 Law of Universal
Gravitation
» Gravity is a force
generated between two
objects.
» Gravity depends on the
mass of each object &
the distance between
them.
Most of the visible light from the Sun comes just
from the fact that it is hot. The surface (what we
see) is about 5800 Kelvin. The center is over
15,000,000 Kelvin.
Sun contains all of the naturally occuring elements,
although some are very, very rare. The Sun is mostly
hydrogen (90%), and helium (9%). Everything else is
only 1% of the Sun.
Gravity Equation
F = G
m 1 x m2
r2
F is gravitational force
r is the distance between the 2 masses
m is the mass of an object
G is the Gravitational Constant
G= 6.673 x 10 -11
m1
r
m2
Albert Einstein
 Theory of General Relativity
» Matter tells space how to curve.
» Curved space tells matter how to move.
» Everything moves in the straightest possible
line in curved space-time.
Gravitational time dilation has been experimentally measured
using atomic clocks on airplanes. The clocks aboard the
airplanes were slightly faster with respect to clocks on the
ground. The effect is significant enough that the Global
Positioning System’s satellites need to have their clocks
corrected.
• I do not believe that civilization will be wiped out
in a war fought with the atomic bomb. Perhaps
two-thirds of the people of the earth will be
killed.
• I know not with what weapons World War III will
be fought, but World War IV will be fought with
sticks and stones.
• Insanity: doing the same thing over and over
again and expecting different results.
• Only two things are infinite, the universe and
human stupidity, and I'm not sure about the
former.
The Planets & their Moons
Distances in the Solar System
 Astronomical Units
 Distances in space are millions of
miles/kilometers in the solar system.
 One astronomical units (AU) is the
distance between the Earth & the Sun.
1 AU = 93 million miles = 150 million km
Terrestrial Planets
Mercury
• .39 AU from the Sun
• Named after the Roman messenger
god (Hermes)
• Covered in craters & cliffs, similar
to the Moon.
• No true atmosphere; trace
amounts of sodium & potassium.
• As cold as -170oC in the dark & as
hot as 425oC in the light.
Mercury is the most iron rich planet in the Solar
System with an iron core like Earth.
Earth and moon from Messenger (on it’s way to
Mercury)
The sun's rays are about seven times as strong on Mercury as
they are on the Earth.
Venus
• .72 AU from the Sun
Its atmosphere is made up mostly of
• Named after the Roman
carbon dioxide. It has clouds made of
sulfuric acid!
goddess of love & beauty
(Aphrodite)
• Thick atmosphere of CO2
which causes a severe
greenhouse effect
producing temperatures
well over 400oC. (Hottest
planet)
• Air pressure is 90 times
greater than the Earth’s.
• Similar to Earth’s size.
Venus is known as Earths' twin sister because of
its similar size and proximity to each other.
 Has retrograde rotation (rotates backwards)
 Takes longer to rotate than to revolve around the
Sun. (Day is longer than its year.)
 Covered with inactive volcanoes.
 3rd brightest object in Earth’s sky.
The pressure at the
centre of the Earth is
27,000 tons per square
inch.
The Sun is 330,330 times larger
than Earth.
Earth
• 1.0 AU from the Sun
• Also known as Gaia, Terra,
or Home.
• More than 70% of Earth’s
surface is covered in water.
• Only planet known to have
life in existence.
• Has a natural satellite
(Moon/Luna.)
Earth spins at ~1100 mph, revolves around the sun a
~67,000 mph, moves (with the solar system) around the
Milky Way at ~45,000 mph, the Milky Way hurtles through
space at ~500,000 to 660,000 miles per hour.
At this moment, the earth is in the middle of the Pliocene-Quaternary glaciation which
began ~2.58 mya. We are in an interglacial period which started btw 10k and 15k
years ago and my last ~50k years before global glaciations begins again.
Mars is red because it is
covered in iron oxide (rust).
In 1996 NASA, while studying the ALH
84001 meteorite of Martian origin
found in Antarctica in 1984, announced
that fossilized micro-organisms from
Mars might be present in it.
Mars
• 1.5 AU from the Sun
• Named after the Roman
god of war (Ares)
• Iron oxide (rust) in the soil
gives it a reddish color.
• Polar ice caps made
mostly of frozen CO2 (dry
ice) & some water.
• Mars is half the size of the
Earth.
• Global dust storms.
• Ranges from -125oC at
night & 20oC during the
day.
Phobos
• Olympus Mons, the
largest volcano in the
solar system is on Mars.
• Thin Martian
atmosphere of Nitrogen
& CO2
• Mars has two small
moons (Phobos and
Deimos) that came from
the asteroid belt.
Deimos rises and sets twice a day.
Deimos
Phobos, is moving closer and closer
to Mars. Scientists think that one day
it will crash into Mars.
Jupiter
Saturn (- rings)
Uranus
Neptune
Earth, Venus, Mars, Mercury, the Moon...
Jupiter's core is non-metal, but due to the
immense pressure inside Jupiter, the core has
become a metal. This metal is liquid metallic
hydrogen.
Jovian Planets
Jupiter
• 5.2 AU from the Sun
• Named after the Roman king
of the gods. (Zeus)
• Completely made of
Hydrogen & Helium gas (gas
giant)
• Largest of the solar planets.
• Swirling bands of rotating
clouds in the upper
atmosphere.
About 1300 Earths would fit inside Jupiter and the Sun could hold about 1000 Jupiters.
Jupiter acts as a huge vacuum
cleaner, attracting and absorbing
comets and meteors. Some
estimates say that without Jupiter’s
gravitational influence the number of
massive projectiles hitting Earth
would be 10,000 times greater.
• Large rotating hurricane called the Great Red
Spot. (2 Earth sizes)
• 4 faint rings in orbit.
• 2.5 times greater in mass than all of the other
planets combined.
• Has at least 63 natural satellites, 4 largest are
known as the Galilean Moons.
The Great Red Spot has been
observed for over 300 years!
Jupiter is so big that twice the
mass of the rest of our Solar
System's planets combined
would still not be enough to
equal its mass.
 Ganymede
» Largest moon in the solar system (bigger
than Mercury, but less mass.)
» Covered with a crust of rock & ice that is
heavily cratered.
» Thin atmosphere of Oxygen.
 Callisto
» 3rd largest moon in the solar system
» Most heavily cratered object in the solar
system.
» Thin atmosphere of CO2.
 Europa
» Covered in a shell of ice
» A deep ocean beneath the ice shell.
» Thin atmosphere of Oxygen.
Europa orbits Jupiter every 3.5 days and is phase locked -- just like
Earth's Moon -- so that the same side of Europa faces Jupiter at all
times.
However, because Europa's orbit is eccentric (i.e. an oval not a circle)
when it is close to Jupiter the tide is much higher than when it is far
from Jupiter. Thus tidal forces raise and lower the sea beneath the ice,
causing constant motion and likely causing the cracks we see in
images of Europa's surface from visiting robotic probes.
This "tidal heating" causes Europa to be warmer than it would otherwise be at its average distance of about
780,000,000 km (485,000,000 miles) from the sun, more than five times as far as the distance from the Earth to
the sun. The warmth of Europa's liquid ocean could prove critical to the survival of simple organisms within the
ocean, if they exist.
 Io
» About the size of the Earth’s Moon.
» Most volcanically active body in the
solar system. Erupts sulfur.
» Thin atmosphere of Sulfur dioxide.
» No craters. Why?
Saturn
 9.6 AU from the Sun
 Named after the Roman god of agriculture.
(Cronos)
 Made of Hydrogen & Helium (gas giant)
 Flattened poles from spinning very fast.
 Less dense than water.
If you put Saturn in water it would float
• Most elaborate system of rings (rock & ice
debris)
• 14 or more rings.
• 56 or more natural satellites.
One of Saturn's moons - Rhea, appears to have a system of rings itself!
Mimas
Titan
Dione
 Titan
» 2nd largest moon in the solar system.
» Has a thick, dense atmosphere mostly of
Nitrogen & some methane.
» Surface is “squishy” & has lakes of
liquid hydrocarbons.
Saturn's moon Titan
has hundreds of
times more oil and
natural gas than all
the known reserves
on Earth.
Even though Neptune is further
Uranus
from the sun, Uranus is the coldest
planet in the solar system.
• 19.2 AU from the Sun
• Named after the Greek god of the sky.
• Gas giant made of Hydrogen, Helium &
methane.
• Rotates on its side.
• System of rings.
• 27 or more moons.
Uranus was originally named Georgium Sidus or “George’s Star”.
On Uranus, each
pole gets around 42
years of continuous
sunlight, followed by
42 years of
darkness.
Neptune
• 30.1 AU from the Sun
• Named after the Roman god of the sea
(Poseidon)
• Gas giant made of Hydrogen, Helium,
& methane.
(the methane makes it blue)
• Near-supersonic & dynamic storms.
• Faint ring system.
• 13 known moons
Neptune is the stormiest planet. The winds there can
blow up to 1,240 miles per hour, that is three times as
fast as Earth's Hurricanes.
Neptune is so far away that it took
the space probe Voyager 2, 12
years to reach it.
 Triton
» Icy, rocky surface.
» Coldest body in the solar system (- 37oC)
» Icy volcanoes & geysers erupting Nitrogen,
dust & methane
Dwarf Planets
Ceres
• 2.7 AU from the Sun
• Largest object in the asteroid belt (950km in
diameter.)
• Classified an asteroid for over 150 years.
• It is believed to have a rocky core, icy water
mantle, & a thin, dusty crust.
Technically, Pluto's name is now 134340
Pluto
after being declassified as a planet.
• 39.4 AU from the Sun
• Named after the Roman god of the underworld
(Hades)
• Second largest dwarf planet in the solar
system.
• Pluto’s companion, Charon , is half the size &
doesn’t orbit around Pluto.
• Pluto & Charon are small enough to fit inside
the United States.
Pluto is smaller than the
Earth's moon.
Some astronomers believe that
Pluto was once a moon of Neptune
but it somehow escaped into its
own orbit.
Eris
• 67.7 AU from the Sun
• Largest known dwarf planet in the solar
system with a diameter of 2400km.
• At least one moon, Dysnomia.
Other Possible Dwarf Planets
 Orcus
 Sedna
 Charon
 Possibly 43 others
Other Solar Objects
Comets
– Large chunks of frozen gases, rock & dust
orbiting the Sun. (Dirty snowball)
1. Nucleus – main portion of the comet
2. Coma – thawed gases & dust form a bright
cloud surrounding the nucleus.
3. Tail – solar winds push away the gases of the
coma forming a blue ion tail & a yellowish-white
dust tail.
If one were to capture and bottle a
comet's 10,000 mile vapor trail, the
amount of vapor actually present in the
bottle would take up less than 1 cubic
inch of space.
Mark Twain was born a year that Halley’s Comet was visable. He died the next time it came by Earth
Nucleus
Coma
Ion Tail
Dust Tail
A comet is a dirty snowball hurtling through space
Famous Comets
 Halley’s Comet
"Delavan's Comet of 1914, whose path was not
accurately determined. ...is not expected to return for
perhaps 24 million years."
» Most famous comet
» Returns roughly every 76 years.
Halley's comet is known to have
appeared in 1066 - the year which
began the Norman Conquest - and
is shown on the Bayeux Tapestry.
Apart from heralding the Battle of
Hastings, comets are also said to
have accompanied the deaths of
Attila the Hun (453 AD), Emperor
Valentinian (455 AD) and
Charlemagne (814 AD) - not to
mention the Fire of London (1666)
and the birth of Napoleon (1769).
 Comet Hale-Bopp
» Comet discovered by amateur astronomers.
» Last seen Spring of 1997.
The comet’s orbit was ~4,200
years but it passed close
enough to Jupiter to change
it’s orbit. It is now
~2,533 years
It will next return to
the inner solar
system around the
year 4385.
It was visible to the
naked eye for a record
18 months, twice as long
as the previous record
holder, the Great Comet
of 1811.
 Comet Shoemaker-Levy 9
» Broke into several pieces and collided with
Jupiter in 1994.
» They created several dark marks in the
atmosphere that eventually disappeared.
The comets that pass close to the Sun originally
came from one of two places: either the Oort
Cloud or the Kuiper Belt. You can think of the
Oort Cloud as a giant spherical shell surrounding
the Sun that's filled with about 1 million million
comets (a 1 followed by 12 zeros).
Asteroids
– Large chunks of rock material left over
from the formation of the solar system.
– Most asteroids are found in the asteroid belt
between Mars & Jupiter.
If an asteroid hit the Earth, the effect would be similar to gathering
ALL the worlds’ nuclear weapons together, and detonating them.
There are hundreds of thousands of asteroids orbiting the Sun. A few
of them are larger than 200 kilometers (125 miles) in diameter, but
the majority of them are about the size of a pebble.
Carbonaceous or C-type Asteroids: More than 75 percent
of asteroids fall into this category.
Meteoroids, Meteors, & Meteorites
– Meteoroids are pieces of rock & dust left
behind by orbiting comets.
– Small meteoroids that burn up in the Earth’s
atmosphere are called meteors or “shooting
stars.”
– Larger meteoroids that don’t burn up in the
atmosphere and hit the Earth are called
meteorites.