Chapter Three, Unit D Cycles in the Solar System

Chapter Three, Unit DCycles in the Solar SystemSpace: the final frontier

Science Question of the DayWhy is it hot in the summer and cold in the winter?

AnswerThe Organization of the Solar SystemThe way we view the solar system has changed a lot over the years. Astronomers used to believe that the Earth was the ___________ of the universe with everything revolving around it.How self-centered of us!

The Organization of the Solar SystemPtolemy was the first to theorize a _________ model (and create a fairly well-working model) of how the planets, moons, and stars move in space.He believed Earth was at the center and all other celestial bodies moved around us. It wasnt until much later that Copernicus developed a new theory (the _________ theory) of how planets rotate around stars like the Sun. The problem with both Ptolemy and Copernicus theories was the way in which they described the motion of the planets as circular. Whats wrong with this??? The Organization of the Solar SystemThe planets travel in an _________ (a flattened circle) around the Sun.This was discovered by Kepler in the early 1600s. This theory was not widely accepted until many years later, however, when Galileo was able to observe planetary motion with the telescope!

Planetary Motion

Planetary Motion

Science Question of the DayWhy does Saturn have rings?

AnswerThe Structure of the Solar SystemOur solar system isnt just about planets and moons; there are also smaller bodies called _________, __________, and _______.An _________ is a chunk of rock and metal that orbits the sun. Asteroids are too small to be called planets, and lack the spherical shape that is characteristic of planets.Many of the largest in our solar system are named and studied by NASA.The Structure of the Solar SystemAnother body that is in our solar system is the _________.Meteors are too small to be considered asteroids.Meteors actually hit the Earth thousands of times a day!Our atmosphere usually burns them up before they hit the Earths surface, but when one does survive and hits the Earth it is called a meteorite. Many times we can see meteor showers at night.The Structure of the Solar SystemOne other fun item we have in our solar system are ________.Comets are balls of rock, ice, and frozen gasses that orbit the sun. They are different than asteroids because asteroids are made of _______ and ______, not gasses. When comets get close to the Sun, the heat causes the gasses to react and glow as well as melt some of the ice in the comet which makes it form a tail. We can see many comets from Earth when they pass close to our orbit around the Sun. Comets, Asteroids, and Meteors

Time for a little practiceRead Asteroids, Meteors, and Comets and answer questions 1-5.

Science Question of the DayWhat are black holes and how are they formed?

AnswerAstronomical Units and Light YearsThe distances in space are gigantic!You may think it takes a long time to get to Florida for your family vacation. Thats only a few hundred miles; try multiplying that times a million and then adding on some more to get to the Sun. Think about how many miles are between us and the farthest planet in our solar system, Neptune.How about from here to the closest Earth-like planet, Gliese 151 c which is ______ trillion miles away?!Astronomical Units and Light YearsInstead of measuring in miles, we measure distances within our own solar system in ______________ units or AUs.One AU is equal to the number of miles between Earth and the Sun, about 93 million miles. This makes it easier to write. Consider this example: Mars is 1.52 AU from the Sun versus Mars is 142,000,000 miles from the Sun.

Astronomical Units and Light YearsThe AU only works in our solar system, however.Stars in other solar systems are millions of times farther than the Sun to Earth, so we would have to use pretty large figures to describe that.Instead, we use a larger unit, __________ years, to measure distances outside of our solar system.A light-year is the equal to the distance light can travel in a vacuum in one year, 5.9 million million miles. Alpha Centauri (the closest star to our solar system) is 270,000 AU from Earth. It is easier to say it is 4.3 light years from Earth. Light Years and Time TravelThe cool thing about light years is that it allows you to look into the past.It takes 4.3 light years for light from Alpha Centauri to reach Earth, so when we look at the star, we are actually looking into the past 4.3 years.

Space, Distance, and Time

Lets do some calculations!We know that one AU is equal to about 93 million miles, so how many miles are the following planets from the Sun?

PlanetMilesAUMercury.39Venus.72Earth1.00Mars1.52Jupiter5.19Saturn9.49Uranus19.11Neptune29.92Time for a little practiceRead Measuring Distance in the Universe and answer questions 1 and 2 only.

Science Question of the DayThere is a definite beginning of time, therefore, there was something before the beginning. What do you think was before the beginning of the beginning?

AnswerThe Cycles of Planets: Axes RotationImagine if there were no rotation of our planet. What would it be like???

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The Cycles of Planets: Axes RotationImagine waking up in the morning to a black sky and and it continued month after month until finally the sun began to rise. The only problem is, the sun will now shine endlessly for months on end.This may sound fun, but think of the heat and drought this will cause.Not to mention how hard it will be to fall asleep with the sun streaming in!This is what the world would be like if it did not __________.Earths RotationBecause of Earths rotation on its _______, we have a day that lasts about 24 hours.The Earths axis is an imaginary line through the planets center from the ________ pole to the ________ pole. The rotation causes the Earth to ________ through daylight and dark areas. Every planet rotates on its axis, but they all rotate at different speeds.

Days and Years on PlanetsEven though our days are 24 hours, other planets rotate faster or slower making their days shorter or longer.Jupiter, for example, has a day that lasts only ________ hours. Venus, however, has a day that lasts as long as ________ Earth days. That is 5,832 hours!

Days and Years on PlanetsPlanets not only rotate on their axes; they also _______ around the Sun.Revolution is the movement of one object around another.An orbit is the path an object follows in its __________.The time in which it takes a planet to take a spin around the Sun is one year, but every year is different depending on the planet and how fast it travels around the Sun. Kepler discovered that the farther you are from the Sun, the slower the planets speed in revolution.

Days and Years on PlanetsFor example, Neptune is the farthest planet from the sun, and it takes it _________Earth Years to travel in its elliptical orbit around the Sun.The closer you are to the Sun, the faster your revolution will be. Mercury makes its way around the Sun in _______ Earth days.

Planetary Motion: Rotation and Revolution

Orbits (not the gum)Planets travel in an ellipse around the Sun. The Sun is not at the center of the ellipse, however, so that means that at certain points in a planets revolution it will be closer to the Sun than at other times.When it is at the closest point to the Sun in its orbit, it is at the perihelion.When it is at the farthest point to the Sun in its orbit, it is at the aphelion. OrbitsEven though the Earth is sometimes closer to the Sun than other points in time, this is not what causes the seasons.We are actually closest to the Sun during mid-winter in the northern hemisphere.The seasons are caused by the Earths tilt in its axis as we discussed earlier in this unit.

Why an ellipse?Lets think about the first law of motion for a minuteHow does this effect the planets revolving around the Sun?

Why an ellipse?The law states that an object in motion will stay in motion unless another outside force acts upon it.The planet is being propelled through space because of _______, but the Suns gravitational pull changes the motion and pulls it back.The inertia combined with _______ causes it to move in a curved path rather than a straight line.Planets Wobble on Their AxesWe have discussed two ways in which the planets move (rotation and revolution), but we are missing the last piece to our puzzle: _________.Precession is the wobble the Earth experiences every 26,000 years. The Earth is constantly moving like a top, but we dont notice it because it happens so slowly. We know it does happen because our North Pole Star changes every 26,000 years. Planets Wobble on Their AxesCurrently, our axis points to a North Star called ________.Because of its location, Polaris doesnt seem to move as Earth rotates. It appears to stay in one spot while all the other stars seem to move around it in fixed circles.Because it seems to never move, navigators use it to help guide them. Since we wobble, our North Star changes. During the time of the Ancient Egyptians it was Thuban. In the future, the North Pole star will be Vega.Science Question of the DayWhat do you think the Great Red Spot is on Jupiter?

AnswerSeasons and Climate on EarthWe know that Earth has seasons because at times it is tilted toward and away from the Sun and can absorb more or less energy and light.If the Earth were to _______ on a vertical axis, the seasons would be the same year round. Because of axial ______, the angle that a planets axis is tilted from a vertical point, the Suns rays are more intense at different points.

Overview of the SeasonsSummerTilted _______ the SunMore direct rays______ daysHeats atmosphere

Overview of the SeasonsFallAxial tilt neither _________ or _______ from SunSunlight angle less direct than in SummerDaylight and dark are almost equalTemperature begins to cool

Overview of the SeasonsWinterNorthern hemisphere pointed _______ from SunSuns rays are slanted and indirect_______ hours of daylightClimate grows cooler

Overview of the SeasonsSpringSimilar to FallAxial tilt neither _______ or ________ from SunRather than progressively growing cooler, the climate becomes warmer

Seasons and Climates on other PlanetsEarth has an orbit that is very close to ________, but other planets have more elliptical orbits.This effects their climate either making it warmer when it is at its perihelion, or cooler when it is at its aphelion.Planets also have tilts which can cause extreme seasons, or no season change at all. Seasons and Climates on other PlanetsMercury and Venus have the ________ axial tilt of all the planets, so they stay very hot and do not experience a change in seasons.Uranus and Pluto have extreme tilts, therefore they have _________ seasons.Some scientists believe that Uranus was hit with an object the size of Earth which changed its _______ tilt so it rotates on its side. Of course distance from the Sun also effects the climates on all planets. Seasons

Science Question of the DayWhy do we only see one side of the Moon?

AnswerMoon PhasesBefore we can really understand some of the other more complex theories, we need to understand facts that are very near and dear to us: facts about the moon and its movement.

Moon PhasesThe Moon never looks the same one night to the next.This is because the Moon goes through _______.Phases are different shapes the Moon seems to have when viewed from Earth.If the Moon produced its own light rather than reflecting light from the Sun, it would always appear as a round disk of light.

Moon PhasesOne _______ of the Moon is always lit by the Sun, but depending on where it is in its orbit, we see different amounts of its lit side.It takes _________ days for the Moon to go through its cycle of phases from New Moon to Full Moon and back again. Between the New and Full Moon the bright area appears to grow larger. These are called _________ phases.From Full Moon back to New Moon, the visible area gets smaller. These are called _________ phases.Moon Phases : 1 New MoonThe ______ Moon can barely be seen because the unlit half is facing Earth.Light from Earth does light this side of the Moon very dimly, so we can still make it out slightly.

Moon Phases: 2 Waxing CrescentThis is where the Moon begins to grow (waxing) in the night sky.It appears as a small sliver, kind of like a thumb nail, or crescent.

The ________ crescent Moon sets before Midnight!

Moon Phases: 3 First QuarterIn the First Quarter, we can see half of the Moons face lit. It is called f_______ quarter because the Moon is one-quarter of the way through its orbit.

Moon Phases: 4 Waxing GibbousIn this phase, we can see of the Moons face lit.

The ________ gibbous Moon rises in the afternoon and sets after midnight.

Moon Phases: 5 Full MoonThe Full Moon occurs when the Moon is __________ around in its orbit. The whole lit side is visible.

Moon Phases: 6 Waning GibbousWaning means that it is getting smaller. After the ________ Moon, the lit side of the Moon appears to grow smaller and smaller.The ________ gibbous Moonrises after sunset.

Moon Phases: 7 Third QuarterIn this phase, half of the Moons lit side is visible.This phase occurs when the Moon is ________ of the way through its orbit.

Moon Phases: 8 Waning CrescentThis is the last phase in the Moons cycle before the ________ Moon again. Notice that the side that was dark before the Full Moon is now lit during the phases after.

The ________ crescent can be seen in the early morning hours before sunrise.

Moon Phases

Time for a little practiceRead The Moon for homework, and answer questions