Download Astronomy, Chapter 1 Learning Target #1 Explain the motion of the

Astronomy, Chapter 1
Learning Target #1
Explain the motion of the sun, the moon, the earth and stars in the sky with the
use of models
a) Identify factors that determine the strength of the force of gravity between two objects
b) Identify factors that combine to keep the moon and Earth in orbit
c) Explain and identify what causes the cycle of seasons
d) Explain and identify what causes day and night to occur on Earth
e) Explain how the calculation of a year and a month show stability in our system so that we
can make predictions
Why is Earth and other planets in our solar system formed in a spherical shape?
Gravity attracted particles toward its center while it was in a liquid or gaseous state
What is gravity?
It is a force that attracts all objects toward each other
What influences the amount of gravity of an object?
The larger the object, the larger its gravitational pull will be
How is the force of gravity measured?
Measured in units called Newtons
What two factors does the strength of the force of gravity between two objects depend on?
1) The mass of the objects
2) The distance between the objects
What is mass?
a) Amount of matter in an object
b) Mass and Weight are NOT the same
Who was the first person to answer the question of what keeps the Earth and Moon in orbit?
Isaac Newton
a) Newton realized that there must be a force acting between Earth and the moon that
kept the moon in orbit
b) Newton was the first person to realize that gravity occurs everywhere
What keeps the Earth and Moon in orbit?
Newton’s law of universal gravitation
Every object in the universe attracts every other object
What factors keep the Moon and Earth in orbit?
Combination of Gravity and Inertia
What is gravity in relation to the moon and Earth?
Earth exerts a gravitational force on the moon, large enough to keep it in orbit.
The moon also exerts a gravitational force on Earth.
What is inertia in relation to the moon and Earth?
Tendency of an object to resist a change in motion
Most places outside the tropics and polar regions have four distinct seasons: winter, spring,
summer, and autumn
But, there are great differences in temperature from place to place
Why does Earth have seasons?
Its axis is tilted
It revolves around the sun
What would have to different for Earth not to have any seasons?
Earth’s axis would have to be straight up and down relative to its orbit
What causes temperatures in the summer to be higher than temperatures in the winter?
More of the Sun’s rays directly hit a particular region on Earth during the summer than during
the winter.
The figure above shows the Earth at two different positions in its orbit around the sun.
If Texas is in the Northern Hemisphere which is the top half of the Earth, which position
corresponds to summer and which position corresponds to winter?
A is winter because it is tilted away from the sun
B is summer because it is tilted toward the sun
What are characteristics of Earth’s tilted axis?
a) Earth’s axis is always tilted at an angle of 23.5 degrees from the vertical
b) As Earth revolves around the sun, the north end of its axis it tilted away from the sun for
part of the year and toward the sun for part of the year
c) Summer and winter are caused by Earth’s tilt as it revolves around the sun.
d) Seasons are NOT caused by changes in Earth’s distance from the sun. Earth is actually
farthest from the sun when it is summer in the Northern Hemisphere
e) Daytime is longer than nighttime during the summer than during the winter.
f) Certain regions on Earth can experience non-stop daylight for six months of the year
g) The Northern and Southern hemispheres experience opposite seasons
How does Earth move?
Two ways
a) Rotation
b) Revolution
What is a rotation?
The spinning of Earth on its’ axis
What is an axis?
An imaginary line that passes through Earth’s center and the North and South Poles.
What are unique characteristics about Earth’s rotation?
Earths rotates eastward, making the sun appear to move westward
It takes about 24 hours to rotate once which makes 1 day = 24 hours
What unit of time on Earth is based on the rotation of the Earth?
Day
What is a revolution?
The movement of one object around another.
What is a year?
Once complete revolution of Earth around the sun is called a year.
a) Earth follows a path (orbit) as it revolves around the sun
b) Earth’s orbit is NOT circular, it is a slightly elongated circle or ellipse
What causes day and night to occur on Earth?
The spinning of Earth on its axis, called rotation, causes you to experience day and night
 Earth spins in a counterclockwise motion
How does the calculation of a year, a day, or month show stability in our system?
It shows that patterns are in place so that scientists can make predictions about type of things
to expect during a year, a day, or a month
 Patterns show us what is going to reoccur
Learning Target #2
Identify the parts of our solar system (planets, moons, asteroids) and show the gravitational
relationship they have with our system
How does gravity affect our solar system?
 Kepler's three laws of planetary motion describe the orbits of objects about the Sun.
The Law of Ellipses, The Equal-Areas Law, and The Harmonic Law
 The force of gravity or the gravitational pull is what enables movement in the solar
system.
 The gravity of the sun tries to pull objects to it, although they keep moving away.
 Gravity plays a crucial role over the entire history of our Solar System, from its very
beginnings as a condensation inside a Giant Molecular Cloud (GMC) right up to the
present day.
 Gravity is very weak but acts over very large length scales
even across the universe.
 The large scale of interaction between bodies is the key to understanding gravity over all
things large in the universe.
 The gravitational pull of the Sun keeps the planets in orbit around it.
What is the solar system composed of?
Sun, planets, asteroids, comets, and other objects in orbit around the Sun.
What is the sun?
 It is a star located in the center of the solar system
 It is the largest object in our solar system
 It is an enormous ball of gas that produces energy by fusing hydrogen into helium in its
core
 More than 99% of all matter in the solar system is contained in the sun
 The energy produced by the Sun comes from nuclear fusion reactions from the Sun’s
core.
 The gravitational pull of the Sun keeps the planets in orbit around it.
 The largest object in our solar system
 It is so hot that the huge amount of hydrogen is undergoing a constant star-wide nuclear
reaction, like in a hydrogen bomb.
 Even though it is constantly exploding in a nuclear reaction, the Sun and other stars are
so large and have so much matter in them that it will take billions of years for the
explosion to use all the "fuel" in the star.
How are planets in our solar system classified?
Inner or Outer planets
Which planets are inner planets and why?
Mercury, Venus, Earth, and Mars, also known as terrestrial planets
They are similar in size to Earth and are made up mainly of rock
These planets have orbits that lie inside the orbit of the asteroid belt
Which planets are outer planets and why?
Jupiter, Saturn, Uranus, Neptune
They are all gaseous giant planets with thick atmospheres
They are made up of light elements such as hydrogen and helium
These planets have orbits that lie outside the orbit of the asteroid belt
What is the order of planets in relation to the Sun?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune
Which planet is closest to the Sun?
Mercury
Which planet is the 5th largest?
Earth
Which planet is the 3rd closest to the Sun?
Earth
Why is Venus referred to as Earth’s twin?
Only because of their similar sizes and masses
How many moons does each planet have?
Mercury &Venus = 0
Earth = 1
Mars = 2
Jupiter = 62
Saturn = 33
Uranus = 27
Neptune = 13
Which planets only have 1 moon?
Earth
Which planet has the largest number of moons?
Jupiter
Which planet is known for a large storm that appears as a giant red spot on its surface?
Jupiter
Which planet is the only one known to have liquid water?
Earth
What objects revolve around the sun?
Comets
Meteoroids
Asteroids
Planets
Pluto used to be considered a planet, but with new evidence it has been reclassified. What is
Pluto labeled as now by scientists?
Dwarf planet
Which of the objects that revolve around the sun is considered the largest?
Planets
What are asteroids?
Small, rocky objects that mostly lie in a belt located between the orbits of Mars and Jupiter
 The asteroid belt is used as dividing line that separates the inner and outer planets
 Asteroids vary greatly in size and are mostly made up of stone, iron and nickel
 Smaller than planets, but larger than meteoroids
What are meteoroids?
Sand to boulder-sized particles of debris in the Solar System
 A mass of rock in space
 They are classified as stony, stony iron, & iron
 They become visibly bright when they enter Earth’s atmosphere
What are comets?
Made mainly of rocky particles and water ices
 As their orbits approach the sun, parts of comets vaporize and form tails
 Almost all of the solar systems comets are located in the Kuiper Belt (beyond Neptune)
and the Oort Cloud (beyond what used to be known as the planet Pluto)
 Are usually smaller than planets, moons, & asteroids
 Made mostly of dust particles, frozen water, and frozen gas
Learning Target #3
Explain the phases of the moon
a) Identify the moon’s cycle in relationship to a month on Earth (full moon, new moon) using
diagrams
b) Explain how many days it takes for a moon to go through one cycle
…such as how long it would take for a new moon or full moon to occur during the next cycle
c) Compare/contrast a solar and lunar eclipse
d) Identify factors that create tides
e) Explain different types of tides that occur on Earth
What causes of the phases of the moon?
The changing relative positions of the moon, Earth, and sun
Why is a day and a year on the moon the same length?
The moon rotates once on its axis in the same amount of times as it revolves around Earth.
Also, the same side of the moon always faces Earth
The length of the moon’s day is shorter than the 29.5 days between consecutive full moons
What is the relationship of the Earth and the Moon?
The moon orbits the Earth
Why does the moon not produce light?
Does not produce light, it reflects light from the sun
What are the phases of the moon?
a) The different shapes of the moon you see from Earth (changes in Moon’s visibility)
b) The whole (entire) set of phases that a moon goes through represents one complete revolution
around Earth
c) The phase of the moon we see depends on how much of the sunlit side of the moon faces Earth
What is each phase of the moon?
a) New Moon
The side with sunlight faces away from Earth making it appear completely dark (no light
anywhere)
29.5 days after the last new moon, the cycle is complete, and a new moon begins
Moon is on same side of Earth as the Sun
b) Waxing Crescent Moon (the light is growing)
c) First Quarter Moon (the light is growing)
d) Waxing Gibbous Moon (the light is growing)
d) Full Moon (happens about once every month)
e) Waning Gibbous Moon (the light is shrinking)
f) Third Quarter Moon (the light is shrinking)
e) Waning Crescent Moon (the light is shrinking)
Position at a full moon of Earth, moon, and sun
Position at a new moon of Earth, moon, and sun
The full moon doesn't occur on the same day of every month because the moon takes 29½
days, and not specifically a month, to orbit the Earth. (As a result of this, you get to witness two
full moons in a single calendar month every three years.) On the day of the full moon, it is at its
best appearing very bright and full from the planet. On a new moon day, on the other hand, it
appears as if there is no moon in the sky, unless you use a telescope to get a glimpse of it.
What is an eclipse?
When an object in space comes between the sun and a third object, it casts a shadow on that
object
What are two types of eclipses?
1. Solar
2. Lunar
What is a solar eclipse?
It occurs when the moon (new moon) passes directly between the Earth and the sun, blocking
sunlight from Earth.
What are characteristics of a total solar eclipse?
The very darkest part of the moon’s shadow is called the umbra which is cone-shaped.
From any point in the umbra, light from the sun is completely blocked by the moon.
The moon’s umbra is long enough so that its point can reach a small part of Earth’s surface.
What are characteristics of a partial solar eclipse?
The moon cast a shadow called the penumbra.
Part of the sun is visible from Earth.
It is not safe to look directly at the sun because the extremely bright part of the sun remains
visible
What is a lunar eclipse?
Occurs at a full moon when Earth is directly between the moon and the sun
Earth blocks sunlight from reaching the moon
Why does a lunar eclipse happen only during a full moon?
The moon is closest to Earth’s shadow at that time
What is a total lunar eclipse?
Earth’s shadow has an umbra and a penumbra. When the moon is in Earth’s umbra, you see a
total lunar eclipse (Sun – Earth – Moon)
What is a partial lunar eclipse?
This occurs when the moon passes partly into the umbra of Earth’s shadow.
What is a tide?
The rise and fall of ocean water that occurs every 12.5 hours or so. The water rises for about 6
hours, then falls for about 6 hours, in a regular cycle
What causes tides?
Differences in how much the moon’s gravity pulls on different parts of Earth along with some pull from the Sun
Describe the relationship of the moon and Earth during the high and low tide?
Two bulges of water form, one on the side of the Earth closest to the Moon and one on the
opposite side of Earth. The reason two bulges form is because the Moon’s gravity pulls harder
on parts of Earth closer to the Moon than on parts farther away.
What is a spring tide?
These combined forces produce a tide with the greatest difference between consecutive low
and high tide. (high tide and low tide are at its lowest)
When does a spring tide occur?
a) This occurs because of the gravity of the sun and the moon pulling in the same direction
b) This occurs twice a month, at a new moon, and at a full moon
What is a neap tide?
A tide with the least difference between consecutive low and high tides
a) The sun’s pull is at right angles to the moon’s pull.
b) Happens during a quarter moon
c) Medium sized tides that occur across Earth’s surface
When does a neap tide occur?
d) This happens during the moons first quarter and during the third quarter phase
Which phase of the moon produces highest tides?
Full Moon
Which phase of the moon produces the least variation in tides?
First Quarter Moon