solar_system

This presentation is for upper primary. It goes through the structure of our Solar System, and compares the different planets. Remember the more data that comes in from different probes can change the different “facts.” Science tries not to be dogmatic, and follows the data that new satellites provide scientists.

There are several theories on the formation of the Solar System and associated planets. The most evidence points to a “Nebular Hypothesis. ” Approximately 4.6 billion years ago, the solar system was a cloud of dust and gas known as a solar nebula. Gravity collapsed the material in on itself as it began to spin, forming the sun in the center of the nebula.

The lecture today will go over how we discovered information about our Solar System. We will look at how objects move and how humans observed this movement.

We will look at real evidence (meteorites) as well as mathematical calculations based on observation.
We will take a quick journey of our solar system including planets and their moons and other objects.
We will look at our immediate system and what you can observe from our place on Earth.

Slide 3. How are objects moving in space?

Ptolemy was an astronomer and mathematician. He believed that the Earth was the center of the Universe. The word for earth in Greek is geo, so we call this idea a "geocentric" theory. Even starting with this incorrect theory, he was able to combine what he saw of the stars' movements with mathematics, especially geometry, to predict the movements of the planets. His famous work was called the Almagest.

In order to make his predictions true, he worked out that the planets must move in epicycles, smaller circles, and the Earth itself moved along an equant. None of this was true, but it made the math work for his predictions. This flawed view of the Universe was accepted for many hundreds of years.

One of the most influential Greek astronomers and geographers of his time, Ptolemy propounded the geocentric theory in a form that prevailed for 1400 years. However, of all the ancient Greek mathematicians, it is fair to say that his work has generated more discussion and argument than any other. We shall discuss the arguments below for, depending on which are correct, they portray Ptolemy in very different lights. The arguments of some historians show that Ptolemy was a mathematician of the very top rank, arguments of others show that he was no more than a superb expositor, but far worse, some even claim that he committed a crime against his fellow scientists by betraying the ethics and integrity of his profession.

We know very little of Ptolemy's life. He made astronomical observations from Alexandria in Egypt during the years AD 127-41. In fact, the first observation which we can date exactly was made by Ptolemy on 26 March 127 while the last was made on 2 February 141.

Early civilizations were always intrigued with the interaction of the Earth, Moon and Sun. Philosophers such as Aristotle tried to make sense of how we became to be.

He is sometimes called the grandfather of science. He studied under the great philosopher Plato and later started his own school, the Lyceum at Athens. He believed in a geocentric Universe and that the planets and stars were perfect spheres though Earth itself was not. He further thought that the movements of the planets and stars must be circular since they were perfect and if the motions were circular, then they could go on forever. Today, we know that none of this is the case, but Aristotle was so respected that these wrong answers were taught for a very long time. Aristotle, outside of astronomy, was a champion observer. He was one of the first to study plants, animals, and people in a scientific way, and he did believe in experimenting whenever possible and developed logical ways of thinking. This is a critical legacy for all the scientists who followed after him.

The Heliocentric Theory is when the planets revolve a fixed Sun. The main proponent was Nicholas Copernicus.

The Polish priest Copernicus revived the idea of a Sun-centered solar system believing that it could explain the motion of the planets more simply.

Copernicus still thought that all heavenly motions must be composed of uniform circular motions, Well over a thousand years later, Nicolaus Copernicus came up with a radical way of looking at the Universe. His heliocentric system put the Sun (helio) at the center of our system. He was not the first to have this theory. Earlier starwatchers had believed the same, but it was Copernicus who brought it to the world of the Renaissance and used his own observations of the movements of the planets to back up his idea. His ideas, including the revelation that the Earth rotates on its axis, were too different for most of the scholars of his time to accept. They used only parts of his theory. Those who did study his work intact often did so in secret. They were called Copernicans

Born in Pisa, Italy approximately 100 years after Copernicus, Galileo became a brilliant student with an amazing genius for invention and observation. He had his own ideas on how motion really worked, as opposed to what Aristotle had taught, and devised a telescope that could enlarge objects up to 20 times. He was able to use this telescope to prove the truth of the Copernican system of heliocentrism. He published his observations which went against the established teaching of the Church. He was brought to trial and, although he made a confession of wrong-doing, he was still kept under house arrest for the rest of his life. But it was too late to lock away the knowledge that Galileo shared. Other scientists, including Sir Isaac Newton and Johannes Kepler, seized its importance and were able to learn even more about the ways of the world and the heavens beyond.

The right type of lenses used for a telescope, were first invented in Holland in the early part of the 1600's. In 1609 Galileo Galilei (1564-1642), an Italian, heard of the invention of spyglasses or refracting telescope. He used lenses in his "optic" tube, which allowed him to see objects that were invisible to the unaided eye. Galileo was able to see stars of the Milky Way, mountains on the Moon, phases of Venus and many other important observations that would lead him to the laws of inertia (a body under no constraint moves in a straight line). Galileo's inquiry on motion would be used by Sir Isaac Newton to uncover more mysteries of the Universe. In 1632 Galileo published a book attacking the current theories of the Earth. He was tried in court and was forced to deny that the Earth moves. He was put under house arrest for his remaining years.

The design of the first optical telescopes in the 1570's was a simple design. There was one concave and one biconvex lens fitted inside a tube. The lenses bend the light as it passed through the glass and made the image 3 to 4 times larger. Galileo in 1609 made a telescope with 20-power refracting telescope. It created quite an international commotion because he discovered the valleys and mountains of the moon and discovered 4 moons of Jupiter. This design could make an image larger, but the tube had to be larger and the lenses needed to be larger. Astronomers were creating monster telescopes up to 150 feet long with a lens of 1 meter (3.28 ft). That was just too large!

Kepler's laws of planetary motion
1. All planets move in elliptical orbits, with the Sun at one focus.
2. The Law of Equal Areas in Equal Time: A line that connects a planet to the Sun sweeps out equal areas in equal times.

3. The Law of Harmony: The time required for a planet to orbit the Sun, called its period, is proportional to long axis of the ellipse raised to the 3/2 power. The constant of proportionality is the same for all the planets.

Kepler's theories were even more revolutionary than the ideas of Copernicus.

Early ideas about the Solar System were based on everyday experience. We do not feel the Earth move, so it is reasonable to think that the Earth stands still. We can see the Sun and Moon rise and set, so it is reasonable to think that they orbit around the Earth.

Kepler's discovery of elliptical orbits was even more revolutionary than Copernicus' theory. For the first time theories were expected to match exactly with observation, no matter how bizarre those theories might be.

First, all planets orbit the Sun in ellipses. Before Kepler, everyone assumed that planetary orbits were composed of circular motions. By studying the orbit of Mars, Kepler realized that this was not true.

Second, planets move faster when they are closer to the Sun and slower when they are further away. The imaginary line between the planets and the Sun sweep out equal areas in equal times.

Third, the time it took for a planet to orbit the Sun depends on its distance from the Sun.

Today we realize that Kepler's Laws suggest that planets are being 'pulled' by the Sun, and that further away from the Sun, its pull gets weaker. However, Kepler did not have the mathematics available to work this out.

Isaac Newton did because he invented the mathematics. Newton realized that the Sun's gravity was pulling on the planets, while his mathematical brilliance allowed him to show how this force explained all of Kepler's laws.

With one equation, Newton could explain both the law of gravity described by Galileo, and the laws of planetary motion described by Kepler.

Slide 9. This slide goes from the Sun to planets to Kuiper Belt to Oort Cloud

Beyond the gas giant Neptune lies a region of space filled with icy bodies. Known as the Kuiper Belt, this chilly expanse holds trillions of objects, remnants of the early solar system. Dutch astronomer Jan Oort first proposed in 1950 that some comets might come from the solar system's far suburbs. That reservoir later became known as the Oort Cloud. Earlier, in 1943, astronomer Kenneth Edgeworth had suggested comets and larger bodies might exist beyond Neptune. In 1951, astronomer Gerard Kuiper predicted the existence of a belt of icy objects that now bears his name. Astronomers are now hunting in the Kuiper Belt for a so-called "Planet Nine," a hypothetical world in the Kuiper Belt, after evidence of its existence was unveiled on Jan. 20, 2016. It is thought to be about 10 times the mass of Earth and 5,000 times the mass of Pluto.

The Kuiper Belt is an elliptical plane in space spanning from 30 to 55 times Earth's distance from the sun, or 2.5 to 4.5 billion miles (4.5 to 7.4 billion kilometers).

Scientists estimate that thousands of bodies more than 100 km (62 miles) in diameter travel around the sun within this belt, along with trillions of smaller objects, many of which are short-period comets. The region also contains several dwarf planets — round worlds too large to be considered asteroids and yet not qualifying as planets because they're too small, on an odd orbit,

Despite its massive size, the Kuiper Belt wasn't discovered until 1992 by NASA scientist Dave Jewitt and Jane Luu.

This slide can be used is multiple ways. It has details on the planet itself, shows pictures of the planet, and some pictures of their moons.

The planets are all named for men except for Venus. Venus rotates opposite of all the other planets, hence the woman’s name. The names of the planets are either from the Greek or Roman gods.

The Sun, the planets, and countless minor objects such as asteroids and comets make up the Solar System. The Solar System is dynamic, always moving. Almost all of its components revolve around the Sun, held in orbit by immense gravitation attraction of the Sun. All of the planets, and many smaller objects also rotate, or spin on an axis.

The planets can be divided into two groups. Mercury, Venus, Earth and Mars form the terrestrial planets. They are small and are composed of rock and metal, like the Earth. Jupiter, Saturn, Uranus, and Neptune are grouped as the Jovian or gas giant planets, because of their large sizes and gas-rich compositions. There is most likely a solid core in the gas giants, but this has not been confirmed.

In the last decade, a wealth of new information on each of the planets has become available. The table on the next page summarizes several characteristics of each planet. Note that the temperature given for Venus is a direct measurement from a Russian spaceship for daytime. For Jupiter, Saturn, Uranus, and Neptune, the temperatures are averages.

PLANET	diameter (km)	length of day	length of year	lowest surface temp C°	highest surface or mean temp C°
MERCURY	4,880	59 days	88 days	-170	+449
VENUS	12,100	243 days	224.7 days	?	+465
EARTH	12,740	24 hours	365.25 days	-88	+56
MARS	6,794	24.5 hours	687 days	-63	20
JUPITER	143,200	10 hours	11.86 yrs	?	-145
SATURN	120,000	10.5 hours	29.46 yrs	?	-178
URANUS	51,800	15.5 hours	84 yrs	?	-195
NEPTUNE	49,500	18.5 hours	165 yrs	?	-201
PLUTO (dwarf)	2,500	6.5 days	248 yrs	?	-330?

Slide 11. You may want to discuss that although Pluto was thought to be a planet, it does not fit into the definition. It is now considered one of the many dwarf planets found in the Kuiper Belt. This pictures just shows some of the dwarf planets and compares them to the size of our Moon.

The Moon and the Earth are held together by gravity. The Earth is much more massive than the Moon causing the Moon to orbit the Earth. The Moon revolves (orbits) eastward looking in the sky from Earth. Each orbit takes 27.3 days. The Moon also rotates, or spins on an internal axis once every 27.3 days. The rotation and revolution take the same amount of time generally due to gravitational attraction of the Moon to the Earth. It makes one rotation per revolution. The Earth/Moon system also revolves around the Sun, taking 365.25 days (or a year) to complete one orbit.

The Moon’s orbit around the Earth is slightly elliptical or oval-shaped. At its closest point (perigee), the Moon is 363,000 kilometers from the Earth. At its maximum distance (apogee), the Moon is 405,000 kilometers away.

The elliptical orbit of the Moon may reflect its origin. Current evidence suggests that the Moon formed after the collision of the Earth with a protoplanet early in the Solar System’s history. The debris from this collision coalesced to form the Moon. Computer models suggest that the early orbit of the Moon may have been highly elliptical, and became rounder with time. Due to the rotation, both the Earth and Moon are slightly wider at the equator than between the poles. They are not perfect spheres, which makes their orbits a little erratic. The Moon’s internal structure is slightly uneven, which would also contribute to an elliptical orbit.

Actually, the Moon appears to wobble a bit (due to its slightly non-circular orbit) so that a few degrees of the far side can be seen from time to time, but the majority of the far side was completely unknown until the Soviet spacecraft Luna 3 photographed it in 1959.

The gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious is the tides. The Moon's gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side. Since the Earth, and particularly the oceans, is not perfectly rigid it is stretched out along the line toward the Moon. From our perspective on the Earth's surface we see two small bulges, one in the direction of the Moon and one directly opposite. The effect is much stronger in the ocean water than in the solid crust so the water bulges are higher.

The revolving Earth/Moon system takes almost 365 days to go around the Sun. This is an Earth Year. The Moon takes 27.3 day to go around the Earth. This is a lunar month.

This slide shows the difference in rotation on its axis. It takes the Earth only 24 hours (Earth Day), but it takes the Moon 650 hours (27 days) to rotate once (Lunar Day). They go in the same direction (counterclockwise). The axis of the Earth is tilted more than the Moon (dotted lines)

The Moon is the Earth's satellite. Students are familiar with the Moon because they see it at night. However the Moon changes its shape from night to night. There also seems to be a cycle to these changes. Every month the Moon goes through a cycle of phases from new (cannot see it) to full (can fully see.) It takes 27.3 days for the Moon to complete one orbit of the Earth. The Earth also moves relative to the Sun at the same time the Moon is revolving around the Earth, so the Moon must complete more than one orbit to return to the same phase as seen from Earth. The time that the Moon takes to complete one cycle or "phases of the Moon" is 29.5 days.

Each spot on the Moon is subjected to two weeks of day light, during which the surface temperature reaches about 100 degrees centigrade (boiling point). The next two weeks are night and temperatures fall to -170 C. The Moon has no atmosphere. There is evidence that there is water ice in some deep craters near the Moon's south pole which are permanently shaded.

There are two primary types of terrain on the Moon: the heavily cratered and very old highlands and the relatively smooth and younger mare (or maria). The mare (which comprise about 16% of the Moon's surface) are huge impact craters that were later flooded by molten lava. Most of the surface is covered with regolith, a mixture of fine dust and rocky debris produced by meteor impacts. For some unknown reason, the mare are concentrated on the near side.

This is just a few from Earth through the complete cycles. This is a lunar month.

This is a time lapse and shows the motion of the month during a lunar month. Ask students what phase they are looking at.

The Big Bang theory is an effort to explain what happened at the very beginning of our universe. Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe. The big bang theory is an effort to explain what happened during and after that moment.