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HISTORICAL GEOLOGY UNIT 3 LECTURE AND STUDY GUIDE

OUR UNIVERSE (Revised 1/15)

UNIT 3 HOMEWORK WEB HIT HOMEWORK – answer questions with a minimum of four complete sentences

For any Unit Web Hits and Unit Web Videos, go to the “DMC HOME” website; in Search box –type “Geology”,

select “Vernon Kramer”, scroll down to GEOL 1404 or 1304, select “Syllabus”, select “ Web Hit”, click on icon for web

site

OR: go to DMC Home website, select “Degrees, Certificates, Courses”, scroll down to Natural Sciences and select

“Geology”, select “Faculty Listings”, select “Walter Vernon Kramer”, find “Geol 1404 or 1304”, select “Syllabus”, and

there you can find the Web hit”, click on icon of interest for web site

[IF NONE OF THE WEB SITES COME UP, YOUR COMPUTER PROBABLY NEEDS TO BE REBOOTED (RESTARTED)

APPS OF POSSIBLE INTEREST: To locate stars, planets: For Android users, Google “skymap”

and find lots of apps – some are free; For Apple (iPhone, etc.) users, Goggle “sky walk” or “iPhone

astronomy app” some are free

Our Universe

-A collection of matter, time and energy

The Big Bang

-The dominant scientific theory about the origin of the Universe

-Big Bang: At the beginning of this event 13.7 billion years ago, all of the observable matter, energy,

space and time were concentrated in one point. What happened before the Big Bang is only

conjecture because at the beginning of time, all matter, and energy was contained in that single point

- a. With quantum physics, we have not been able to go back further in time than 10-43 second; at that

time all known matter and anti-matter in our universe would have been collected in a mass smaller

than a proton

- b. At 10-43 second, the point source instantaneously “inflated” from the size of a proton to the size of

a grapefruit and this is known as the “period of inflation”; there was no visible light

- c. At 10-34 second, quarks and other subatomic particles began to form after almost all antimatter was

eliminated; there still was no visible light and space is expanding

- d. At 10-10 second, larger subatomic particles began to form (still no light) and space continues to

expand

- e. At 10-5 second, protons and neutrons began to form (still no light) and space is very large

- f. During 1 – 3 minutes, atomic nuclei of hydrogen, helium nuclei and some lithium nuclei formed

from protons and neutrons, but still no light. After three minutes, the distance that space itself

expanded is almost unbelievable!

- g. ~ At 300,000 years, nuclei of (H) hydrogen, some (He) helium and a little (Li) lithium captured

electrons and atoms were formed; light became visible for the first time throughout the known

universe

- h. With the Hubble Ultra Deep Field, we have been able to find small galaxies only a few million

years old

- i. – At one billion years; matter is clumping to form the large galaxies and many stars; galaxies began

to form pairs, groups, clusters and superclusters

- j. – Within 2-5 billion years; our own Milky Way Galaxy would form, but our sun and Earth would

have to wait another 8-10 billion years to be created

- k. Now our universe is about 13.7 billion years old and here you are at Del Mar College

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-The universe was not concentrated in a point at the time of the Big Bang, but the observable universe

was concentrated in a point. Then space itself expanded, not the galaxies. There is no center of our

universe because all positions are equivalent.

If I accept you as you are, I will make you worse; however if I treat you as though you are what you

are capable of becoming, I help you become that.

Evidence for the Big Bang

-1. Physics predicted that, with a Big Bang event, the cosmic abundances of atoms in space should be

mostly H, some He and a little Li. – and this is what we have detected!

-[cosmic = universe or universal]

-2. With a Big Bang, we should see indications that the universe is expanding with large “red shifts of

cosmological light” from distant galaxies. With a special instrument attached to a telescope, we can

see the visible colors or “spectra” of light colors (resembles rainbow colors). Here we will see many

black lines on the spectra that are caused by absorption of light by hydrogen gas within the stars and

galaxies. With stars and galaxies moving away from us, we will see the black lines move toward the

red end of the rainbow colors (or red shifted). The further the movement of the black lines toward the

red, the larger the red shift. This large shift would mean the universe is expanding faster

Thus the universe is expanding and the speed of expansion increases with distance away from us as

determined by the red shifts. In fact, the further a galaxy is away from us, the faster the galaxy is

moving away from us. Our universe has been expanding for billions of years.

A star or galaxy moving toward us shows a blue shift with the hydrogen absorption lines.

Picture showing red shift caused by expansion

-3. The Cosmic Microwave Background Radiation (CMB) is the temperature or energy left over from

the Big Bang (the temperature of space itself has been cooling ever since the Big Bank)

- [kelvin – temperatures commonly used for space; absolute zero -459 0F represents minimal atomic

movement]

-The WMAP satellite studies show that the CMB temperature is really at 2.7 kelvin, and a picture of

this temperature shows that the CMB is “lumpy”. The remaining heat is not evenly distributed

within our universe. It was because of this uneven distribution of heat that allowed for formation of

galaxies.

- About 1% of TV static comes from the Big Bang (actually from the CMB)

The tragedy of life doesn't lie in not reaching your goal. The tragedy lies in having no goals to

reach. Benjamin Mays

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Microwave radiation left over from Big Bang

Expanding Space

- Space itself is expanding in all directions.

- Space can be compared to raisins (galaxies) in bread dough (space); the raisins (galaxies) stay the

same size as the bread dough (space) rises and expands to form bread

- How long will space continue to expand? We can observe that at one time, the expansion of space

was beginning to slow down.

- Space can either expand forever or come back into a “Big Crunch”

- But latest evidence suggests that rate of expansion for our universe is increasing and will probably

expand forever

“Concept Test” about space expansion

What Makes Up the Known Universe

- Visible and detectable matter and energy make up 4%- 5% of our known universe

- Undetectable “dark matter” forms about 25% of our universe

- Undetectable “dark energy” forms about 70% of our universe

- Dark energy is opposite of gravity and apparently forces bodies apart

Light Speed

- Light travels at 186,000 miles per second

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- Light year: the distance that light travels in one year (6 trillion miles)

- Nothing can travel faster than light

- Light takes 8.3 minutes to travel from the sun to Earth

Galaxies

- Edwin Hubble (1929) was the first to prove that galaxies were generally star systems that were

located outside of our own galaxy; later our space telescope would be named after him

- Galaxy: a vast collection of stars, dust, gas and black holes

- Some galaxies formed directly from dust and stars in a few hundred million years

-Other galaxies formed from mergers of star groups or smaller galaxies

Hubble galaxy tuning fork diagram

Galaxy Types

- Uses Hubble “tuning fork” classification (remember there are lots of classifications

- 1. Elliptical Galaxy: (E above) massive, featureless galaxy that form 13% of all galaxies; has billions

to trillions of stars; + 100,000 light years across; these galaxies generally represent a collect of old

stars in a very crowded neighborhood.

- M87 elliptical galaxy, about 120,000 light years across, is largest known galaxy with more than 2.7

trillion stars

- 2. Spiral Galaxies (Spiral: S above and Barred Spiral: SB above); 34% of all galaxies; barred spiral

galaxies have a central “bar”;spiral appearance, + 100,000 light years across and a 1,000 light years

thick; contains hundreds of billions of stars; spirals commonly have a central region of old yellow

stars, with younger blue stars and dust along the spiral arms

- 3. Irregular Galaxies: 54% of all galaxies; averages 1,500 light-years across; a few hundred million

stars; since they are so relatively small, irregulars are difficult to observe over the vast reaches of

space.

Collisions

- Telescopic observation show that galaxies can collide and pass through one another. Galactic

collisions are fairly common in our Universe

Grouping of Galaxies

- Galaxies often form pairs and groups and will be gravitationally bound to one another

- Cluster: large, gravitationally bound “structure” formed by a collection of hundreds to thousands of

galaxies

- Large galaxy clusters can cause the light from other galaxies far behind them to “bend”

- Einstein Cross: galactic phenomena of a single distant galaxy appearing to be multiple galaxies

because of the frontal galaxy’s gravity bending light

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- Einstein Ring: galactic phenomena of one galaxy appearing to be a ring because of the frontal

galaxy’s gravity bending of its light

- Superclusters: groups of cluster of gravitationally bound galaxies that could involve millions of

galaxies

- There are probably more than (+) 350 billion galaxies

- There are probably more than 300 billion trillion stars

- Most of the visible universe is empty space; the largest structure of our visible universe is empty

space

- As a footnote: There is a feature call the “great wall of galaxies” that we do not understand. This

“wall” is 500 million light years long, 200 million light years wide and about 15 million light years

thick.

Great walls (super-clusters) of galaxies

- Video of millions of galaxies

-Concept exam about seeing a galaxy

Nebula

- Nebula: Gas and dust collected in galaxies that can block visible starlight, and we can find this will

all spiral galaxies

- A famous example is the Eagle Nebula more than 7,000 light years away

- This nebula contains more than 150 know molecules including water, ammonia, cyanide, amino

acids, minerals, methanol, formaldehyde, etc.

- Often called molecular clouds

- Our solar system may have evolved from such a cloud.

- Famous nebula include the Carina Nebula, Lagoon Nebula and the Horse head Nebula

Horse head nebula

Milky Way Galaxy

- Our Milky Way Galaxy is a barred spiral galaxy that is more than 100,000 light years wide, with 200-

400 billion stars and lots of molecular clouds

- It takes our solar system about 250 million years to make one orbit about the galaxy; so we have been

around our galaxy at least 16 times.

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- The disk of the Milky Way is about 1,000 light years thick

- There is a massive “black hole” at our galactic center, called Sagittarius A* (star) with a mass of

more than four millions suns

Milky Way Galaxy

Components of Typical Barred Spiral Galaxy (like the Milky Way)

- Earth is located about 28,000 light years from the center of our galaxy

- Has a halo of globular clusters

- Has a flat disk with dust and gas lanes

- Has a central bulge of old stars

- Has a central black hole

Our galaxy and globular clusters

The surest way not to fail is to determine to succeed.

Globular Clusters

- Globular Cluster: vast collection of stars (some have a million stars) that orbits in and out the galactic

disk

- All galaxies have globular clusters that orbit in and out of the parent galaxy; some galaxies have

thousands of globular clusters.

- Milky Way has 146 globular clusters

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Large Magellanic Cloud

Magellanic Clouds

- Small and Large Magellanic Clouds: Two dwarf, irregular galaxies being captured by the Milky Way

Galaxy. These are only visible from the southern hemisphere

Andromeda Galaxy

Andromeda Galaxy

- Neighboring galaxy that is twice the size of the Milky Way, about 2.5 million light years from the

Milky Way

- Andromeda is moving toward the Milky Way Galaxy at a speed of 300,000 miles per hour and will

collide with the Milky Way in about 5 billion years. Even though more than 450 billion stars will be

involved with the collision, only four or five stars will actually collide.

-Video simulation of the Milky Way and Andromeda Galaxy colliding

Raw Materials for a Solar System

- The original universe was composed of only 3 elements (H, He, Li) yet our sun is composed of 92%

H, 7.8% He and 0.2% of other elements.

- Our sun (star) is so hot that over its lifetime, the sun will create at least 10 elements including carbon,

oxygen, neon, magnesium, silicon, sodium, aluminum and sulfur.

- The remaining 90 elements are created from giant exploding stars called supernovas

- It is these elements that collect in space as molecular clouds or nebula that will eventually form solar

systems and us

- Concept exam about elements

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Solar Systems - General

- Presented a brief explanation of the formation of our solar system

- Star and planetary systems that form from collapsing gas and dust clouds, within a galaxy

- Planetesimal: any of the innumerable small bodies that orbit a star

- Protoplanet: a planet in the process of accretion

- Planet: (one example) an object that has a total mass between that of Mercury and 10 Jupiter masses

- Solar System: a series of planetary bodies that orbit a central star

Shape and Motion of Our Solar Systems

- Our Solar systems represent disk-shaped systems with a sun at the center

- All planets orbit our star in a counterclockwise direction (as viewed from top)

- Almost all our solar system moons also revolve and rotate in a counterclockwise direction (from top)

Our Sun

- Our nearest star is the sun

- Diameter is 865,000 miles (109 times that of Earth)

- The sun contains 99.8% of the mass of the solar system

- Composition of mass: 73.4% Hydrogen; 25% Helium; 0.8% Oxygen; 0.2% Carbon

- Energy source is nuclear fusion, changing 700 million tons of hydrogen to helium every second

- Surface temperature is about 11,000 0F with its interior at 27 million degrees

- The sun is 4.6 billion years old

- Distance from the Earth is 93 million miles

- It takes light 8.3 minutes to reach Earth

- Video of our Sun

Classification of Stars

- Stars are classified according to the Russell-Hertzsprung Chart, starting with the main sequence

“dwarf” stars like our sun

- Small red and brown stars can have 1/100th the mass of our Sun’s mass

- Smallest stars include white dwarfs which are burned-out stars that become the size of Earth

- Based on temperature and brightness, our sun is an average size yellow star

- Red giant star are old age suns

- There are two types of super-giant stars: the blue super-giant stars that can have the mass of 100 suns;

they are so massive that their life times are measured in millions of years instead of billions of years.

- The red super-giants such as Betelgeuse have a size that would envelope Jupiter’s orbit.

Russell-Hertzsprung diagram

Fate of Stars

- If star mass –s (less tan) < ~ 4 times the mass of the sun; the star will become a red giant whose size

will envelope Earth’s orbit, afterwards the star will become a white dwarf

- In another 5 billion years, the sun will become a red giant and envelope Earth’s orbit

- If star mass is (greater than) > ~ 4 times the mass of the sun, may eventually explode in a supernova

and become a neutron star or a black hole

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Nearest Star Other Than the Sun

-Proxima Centura: located four light years away

Other Planets Not in Our Solar System (Exoplanets)

- There are more than 909 known exoplanets (Feb. 2013), surrounding more than 700 stars and 2,740

candidate planets for a total of 3,649 planets (this number increases almost every month). We do

have a few telescope pictures of exoplanets (star HR 8977).

- Many of these planets were detected by “star wobbles”. Wobble uses the Doppler shift of light which

is bluish when moving toward us and reddish when moving away from us.

- Also, we are locating planets with the Kepler Space Telescope (KST) launched in 2010. The KST

uses using the “transit method” which measures the dimming of star light by a passing planet. So far,

the Kepler Space Telescope has found over 2,700 candidates for exoplanets (Feb. 2013).

- The number of possible planets in our galaxy may exceed 160 billion.

- Almost all planets discovered to date, are larger than Jupiter with 2 possible Earth-size planets.

Concept exam about exoplanets

Our Solar System of Planets

Take a Quick Tour of Our Solar System of Planets (Pages 14-16)

The Four Inner Rocky Planets Orbiting Our Sun

Inner rocky planets

Mercury: Smallest rocky planet, lies 138 million miles at its closest point; one year = 87 Earth days,

no atmosphere, it is cratered like our moon; there are signs of old volcanic activity; it is 40%

larger than Earth’s moon, and is the only planet without a gaseous atmosphere. The Messenger

Space Probe passed by Mercury in 2009 and took detailed pictures. Messenger began orbiting

the planet in March 2011 with amazing pictures. We see evidence of recent impacts and the

mysterious “spider-web crater”. We also see evidence of faulting, indicating that Mercury still

has a liquid interior like Earth. Mercury has no moon.

Venus: Earth size diameter but only 0.8 Earth’s mass; it is the nearest planet to Earth at 25 million

miles at its closest point, one year = 244 Earth days and 1 day = 244 Earth Days (retrograde axis

of rotation); has no known surface water, has an acid and CO2 atmosphere that is 90 times

Earth’s atmospheric pressure; has a surface temperature of 800 oF. (hotter than Mercury). Its

surface is not visible in normal light but has been mapped with satellite radar. In the 1970s

Russia landed several probes that were able to take a few pictures. The surface resembles a

rocky desert. The Venus Express Space Probe is currently orbiting and studying Venus and has

discovered water coming from the planet. Venus is the only planet that spins clockwise with its

orbit. Venus has no moon.

Two videos of Venus

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Earth: Dominated by blue oceans and white clouds – to be discussed in detail later this semester

Mars: This planet is 91 million miles from Earth at its closest orbit. ½ size of Earth but only 1/10 of

Earth’s mass; 1 year = 686 Earth days and 1 day = 1 Earth day; has extinct volcanoes, sand

dunes, and ancient river valleys; a thin atmosphere of CO2; a cold surface temperatures (23

degrees to -123 degrees F) with glaciers on the North and South Poles. An active US mobile

probe - Opportunity that landed in 2004, is still actively touring and exploring the actual surface

of Mars. The Spirit probe, on the opposite side of the planet ceased operations in 2010. The two

aforementioned probes discovered evidence of past liquid water on Mars. The Phoenix Mars

Lander (5/2008) landed near the Mars North Pole and discovered water ice below the Martian

soil. There are several satellites currently orbiting Mars and taking pictures and surveying for

minerals. The mobile probe Curiosity arrived to Mars in August 2012. You can tour Mars with

Google Mars. Mars has two tiny moons. (You can view Kramer’s Science Seminar of January 15, 2008 for more information about minerals and mining on Mars)

- Videos of the landing of the probes on Mars

Outer gas giants

The Outer Giant Gas Planets – or The Jovian Planets

Outer giant gaseous planets (which may have rocky cores possibly larger than Earth and all these

giants have atmospheres thousands of miles thick).

Jupiter: (435 million miles from Earth) is larger (has more mass) than all other solar system planets

combined; and could be considered a failed star. Some suggest that Jupiter could have a rocky

core maybe 10 times the mass of Earth. Jupiter is 11 times the diameter of Earth (could hold

1,000 Earths) and has 318 times more mass; one year = 12 Earth years and one day = 9 Earth

hours. The Galileo Space Probe ended 9/2003 with much data and many pictures of the planet

and all of its moons. A thin ring system circles the planet; massive storms dominate its

atmosphere

When I hear somebody sigh that life is hard, I am always tempted to ask, Compared to what?

Saturn: (2.7 billion miles from Earth) with its famous rings is 10 times larger and 95 times heavier

than Earth; one year = 29 Earth years and one day = 10 Earth hours. We will discuss some of its

moons later. The Cassini Space Probe is currently orbiting this planet and studying its many

moons and rings. There are years in which the Saturn rings are not visible from Earth, because of

the “swaying” of Saturn.

Uranus: (5.4 billion miles from Earth) rotates on its side; is 4 times larger and 86 times heavier

than Earth; 1 year = 84 Earth years and 1 day = 17 Earth hours. Uranus was visited by the

Voyager 2 Space Probe in 1986. This planet also has a set of rings circling the planet.

Neptune: (10 billion miles from Earth) is 4 times larger than Earth and 17 times heavier; 1 year =

165 Earth years and 1 day = 16 Earth hours. Neptune was visited by the Voyager 2 Space Probe

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in 1989. Neptune was discovered in 1846 will complete its first orbit in 2011 (since discovery).

Neptune also has a set of rings orbiting the planet.

some plutoids

Plutoids

The discovery of 2003 UB 313 (now called Eris) changed our definition of planets. Plutoid Eris is

larger than Pluto, and has a 560 year orbit. More than 200 other classified Plutoids have been

discovered. This is why Pluto was reclassified!

As of June 2008, large “heavenly bodies” beyond the general orbit path of Neptune will be

classified as Plutoids.

- Pluto (whose diameter is ½ the width of the US) was first reclassified as a dwarf planet, as well as its

largest moon Charon and two smaller moon Hydra and Nix and two smaller moons. Pluto is now

classified as a Plutoid. The New Horizons Space Probe should reach Pluto in 2015 for our first

close-up view of that demoted planet.

Dwarf Planets

- On June 2008, large “heavenly bodies” within the orbit of Neptune will be reclassified as Dwarf

Planets.

- The large asteroid Ceres is now classified as a dwarf planet. The Dawn Space Probe reached the

giant asteroid Vestra July 2011 and taken incredible pictures of the asteroid. Dawn should reach

Ceres by 2015 for our first close up view of that asteroid.

larger moons

Moons of the Solar System

- Our solar system of (8) planets probably have more than 169 moons. (Mercury = 0; Venus = 0;

Earth = 1; Mars = 2; Jupiter = +63; Saturn = +60; Uranus = 27; Neptune = 13)

- Two moons (Ganymede and Titan) are actually larger than the planet Mercury

- There are 9 moons larger than Pluto

- Most of these moons are composed of (water and some methane) ice, commonly with rocky cores.

- So Earth is not the only heavenly body to contain water and ice.

- The Jupiter moon Ganymede and the Saturn moon Titan are larger than the planet Mercury.

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- Jupiter has a moon (Io) with active volcanoes and another moon (Europa) with a partially frozen

ocean.

- Ganymede has a thin atmosphere of oxygen.

- Both Ganymede and Callistro have liquid oceans beneath their icy crusts.

- Video of Io

- We listened to radio waves that came from the Jupiter moon Ganymede.

- The four largest moons of Jupiter are visible from Earth using binoculars.

- Saturn has a special moon (Titan) that has a methane atmosphere and visible river systems and lakes

created by methane rain (in 2005, the Huygens Space Probe landed on this moon and took pictures).

- Enceladus, a tiny moon of Saturn have been found to have volcanoes spewing out water

- Neptune also has a special moon (Triton) that has a nitrogen atmosphere and clouds and active

volcanoes.

- As of 2012, Pluto now has five moons.

- An even plutoids Eris has its own moon Dysnomia,

- Concept exam about moons

some large asteroids

Asteroids

- Asteroid: Rocky and metallic objects that orbit the sun but are too small to be considered as a planet

- There is a belt of tens of thousands of rocky asteroids, mostly between Mars and Jupiter. The mass of

all of the asteroids is less than the mass our moon.

- Some asteroids have been found to have their own moons, such as Ida with its moon Dactyl.

- The US has landed a probe on Near Earth Orbit (NEO) crossing asteroid Eros. The Japanese have

sampled the asteroid Itokawa (2005) that is composed of many loosely held fragments of rocks.

- There are less than a dozen people searching and keeping track of potentially dangerous asteroids in

Earth crossing orbits (NEO). For far, they have located more than 700 asteroids that are of some

concern. (Remember that an asteroid Chicxulub collided with Earth and wiped out the dinosaurs).

iron meteorite

Meteorites

Meteorite: a rock that formed elsewhere in the solar system and then landed on a planet

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Composition:

1. Stony meteorite: composed of silicates and oxides; comprise 94% of all meteorites; most of

these meteorites are chondrites which contain small spherical structures

2. Iron meteorite: metallic meteorites composed of iron and some nickel; they form about 5%

of all meteorites. Several iron meteorites were found on the surface of Mars by a rover.

3. Stony-iron meteorites: rare, less than 1%; they are composed of mixed iron and stone

Meteor impacts on Earth:

- Meteorites have crashed into homes and cars, but not a single person has been killed by a

meteorite (but a dog was killed in Africa)

- About 500 baseball sized meteors reach the Earth’s surface each year.

- Thousands of meteorites have been found in Antarctica each year

Barringer Crater

Meteor Craters:

- There are 170 well documented meteor craters of various ages on Earth.

- Barringer Meteor Crater of AZ is ½ mile across and about 20,000 – 50,000 years old.

- Manicouagan Crater in Canada (+200 million years old) is Earth’s largest visible crater at 42

miles diameter

- At Marquez, TX, near College Station is a deeply buried 58 million year old crater

- Meteor Crater at Odessa TX is the third largest crater in the US (25,000 years old)

- Footnote: over 230 meteorites have been found in Texas; more than any other state

Comets

- Comet: A body containing a mixture of ice, gas and rock that periodically enters and leaves the Sun’s

planetary system

- Two types of comets: Short Period and Long Period

Nothing is particularly hard if you divide it into small jobs. Henry Ford

-Two origins of comets: the Kuiper Belt and the Oort Cloud

- Oort Cloud:

- An immense spherical “cloud” of ice, gas, dust and rocks that surround the solar system

- May extend outwards to three light years

- Origin for long period comets with periods (orbits) of more than 200 years

-Kuiper Belt:

-Disk-shaped region of ice, gas, dust and rock past the orbit of Neptune

-Origin for short-termed comets with periods (orbits) less than 200 years

Has an estimated 35,000 objects greater than 600 miles in diameter

- Pluto is often considered to be a Kuiper Belt object

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- Quaoar is an 800 mile diameter Kuiper object

Sketch of location for Kuiper Belt & Oort Cloud

comet

- Parts of a Comet:

- Coma: long visible luminous, gassy, dusty “tail” of a comet

- We have close-up satellite pictures of comets, so that we can see their nucleus

- About ½ of a comet is composed of frozen water, carbon dioxide, carbon monoxide,

ammonia, methane and formaldehyde with the remaining being rock

- In 2005, the US impacted Comet Temple 1 with a probe

- There are almost 1,000 known comets

- Halley’s Comet has a 75 year orbit that passed Earth in 1986 and will pass again in 2061

- In 1994, Comet Shoemaker-Levy broke apart and impacted Jupiter, leaving temporary Earth-sized

scars

- Meteor showers and shooting stars are sand-sized particles, derived mostly from debris left in comet

orbits. When Earth crosses an older orbit, we see lots of shooting stars.

- In 1903, a comet impacted Tunguska, Russia, lucky to hit in an unpopulated area

- On average, Earth is probably hit with a comet every 300 years.

Space Distances – How Far Is Far, Far Away?

- Size and distance comparison: using an orange as our Sun, Earth would be represented as a sand

grain that would be more than 30 feet away from that orange.

- Our next nearest star (Proxima Centuri) can be compared to another (smaller) orange that would be

located more than 1,000 miles away from the larger orange. (From Corpus Christi to Tucson)

- MOST OF THE UNIVERSE IS EMPTY SPACE

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front and back of moon

Our Moon

- Before or shortly after the Earth was formed, a planet the size of Mars impacted Earth and blasted

rock debris into space. Within a few thousands years, the “space debris” accreted into the moon.

- Our moon is very large compared to the planet it revolves around.

- The moon is about 1/4th the size of Earth’s diameter

- The moon lies about 240,000 miles from Earth and orbits the Earth in about 28 days

- The moon completes one wobbly rotation per month, and the same side always faces Earth

The Difficult is that which can be done immediately; the Impossible is that which takes a little

longer.