Reading: Textbook Chapter 19-21 p. 650-769
Origin of the Universe
What is the Universe? The Universe is the sum of all space, matter, and energy that exist, that have existed in the past and that will exist in the future.
When we look out at the universe, we see the universe now as it was in the past. The sun is 8 light-minutes away, Pluto is more than 5 light-hours away and other galaxies and stars are beyond that .
Most of the universe is empty space. There is almost nothing between objects in space. Space is a vacuum with no air or air pressure.
Go to History.com and Explore The Universe.
We know that the universe is expanding. The spectral lines observed by telescopes almost always appeared to have shifted to the red end of the spectrum. This effect, called the red shift, is part of the Doppler effect that states when a luminous object is moving away from the observer the wavelengths stretch longer and and shift to the red end of the spectrum. It has been observed that almost every galaxy is moving away from Earth and each other.
The big bang theory states that the universe began with a gigantic explosion 10 billion to 20 billion years ago. Radiation dominated the early universe. The universe expanded and cooled enough for hydrogen and helium atoms to form. This allowed stars and galaxies to from. Our solar system is thought to be 4.6 billion years old.
The future of the universe is uncertain.
The Solar System
The Formation of the Solar System
The first model of the solar system put Earth in the center. Aristotle explained the phases of the moon and eclipses by using a model of the solar system with Earth in the center, "Earth-Centered model.
Copernicus proposed a heliocentric, or sun-centered model. It was Isaac Newton and his theory of gravity that explained that a force keeps the planets and all satellites in orbit around the sun. The sun is our closest star. His theory also states that every object in the universe exerts a gravitational force on every other object.
The Nebular Model for the Formation of the Solar System
A. The solar system may have begun as a nebula, a large cloud of dust and gas in space.
B. The solar nebula begins to rotate, flatten and get warmer near its center.
C. As particles collide with each other the clump together to form planetesimals in the swirling disk.
D. Because of their greater gravitational attraction, the larger planetismals begin to collect the dust and gas.
E. Smaller planetismals collide with the larger ones and the planet begin to form.
F. The remaining dust and gas are gradually removed from the solar nebula, leaving the planets around a hot gaseous center of the solar system, our star the sun.
Go to the assignments section and do questions 1-5.
What are stars? A star is a large celestial body that is composed of hydrogen and helium gas and that emits light. The nearest star to Earth is the sun, all other stars are outside of our solar system. Stars are driven by nuclear fusion reactions. Energy moves slowly through the layers of a star.
The brightness of a star depends on the star's temperature, size and distance from Earth. We learn about star's by studying light. A star's color is related to its temperature. Dark spectral lines appear on a spectrum when light passes through hydrogen gas or helium gas. The spectral lines reveal the composition of stars.
Stars are formed by a cloud of gas and dust that collapsed inward and began to spin. These clouds are called nebula. About 30 million years after the cloud collapsed, its center has reached 15 million kelvin and has become a protostar. As stars continue to go through nuclear fusion from hydrogen gas combining to make deuterons and then two deuterons making helium, the star will eventually run out of hydrogen.
When a star begins to run out of hydrogen it begins to die. Scientists estimate that the sun can continue nuclear fusion for another 5 billion years.
The sun will become a red giant before it dies. It will appear red because its surface is cooler. The outer gases will expand and eventually leave the star. What remains is a small very dense start about the size of Earth, called a white dwarf.
Supergiant stars evolve faster, develop hotter cores and form iron cores. When the core becomes mostly iron the star explodes creating a supernova.
Go to The Stars to learn more about types of stars and how they are formed.
Go to assignments and do questions 6-10.
The Milky Way and Other Galaxies
Galaxies are a collection of stars, dust, and gas bound together by gravity. Galaxies contain millions or billions of stars.
Our solar system is in the Milky Way Galaxy. Our solar system is located within a spiral arm, about 26,000 ly from the center, or about half of the distance to the edge.The next closest galaxy is the Andromeda Galaxy. It is 2.2 million ly from Earth. This galaxy is visible to the unaided eye as a faint blur. New stars form in galaxies because of the gas and dust located between stars called interstellar matter.
Types of Galaxies
Spiral - a spiraling disk of stars, gas, and dust with a bulge in the middle and spiraling arms extending out, an example is the Milky Way Galaxy shown below.
Elliptical - a no spiraling arms and are spherical or egg shaped, an example is the Messier 87 Galaxy shown below.
Irregular - lack regular shape and do not have a well-defined structure, an example would be the Wolf-Lundmark-Melotte Galaxy shown below.
Go to assignments and do questions 11-15.
The solar system is the sun and all the planets and other bodies that travel around it. The sun makes up 99% of the mass of the solar system. The nine planets and their moons make up the other 1%. The solar systems has many other small objects; meteoroids, asteroids, comets, gas, and dust. Gravity holds the solar system together.
The Nine Planets
Planets can be seen because their surfaces or atmospheres reflect sunlight. A satellite is an object in orbit around a body that has a larger mass. The moon is Earth's satellite because the Earth has a larger mass. Satellites orbit planets. All of the planets in our solar system have moons except Mercury and Venus.
The inner planets are called terrestrial planets. Terrestrial planets are ones nearest the sun, highly dense, rocky, smaller, and higher temperatures. The inner planets include Mercury, Venus, Earth, and Mars.
Mercury has extreme temperatures from 670 kelvin during the day to 103 kelvin at night. It has almost no atmosphere and no water.
Venus can be seen from Earth near sunset or sunrise as the morning star or evening star. Thick carbon dioxide clouds on Venus cause a runaway greenhouse effect, trapping in the sun's heat and causing the planet to be very hot. The surface of Venus has mountains and plains.
Earth has ideal conditions for living creatures. It is the only planet that has large amounts of liquid water on its surface. The atmosphere protects Earth from radiation and sustains life. The atmosphere and the distance from the sun make Earth a great planet for living things. Most calendars are based on Earth's orbit around the sun and have a 365-day year. Some ancient cultures have based calendars on the moon.
Mars has a small region of polar icecaps.
It has a very thin atmosphere, composed mostly of carbon dioxide. Mars has two small satellites, Phobos and Deimos. Mars' mass is 10% of Earth's and it is very cold. Mars has the largest volcanoes in the solar system. The asteroid belt divides the inner and outer planets. An asteroid is a small, rocky object that orbits the sun, usually in a band between the orbits of Jupiter and Mars.
The outer planets are gas giants, Jupiter, Saturn, Neptune, and Uranus. Pluto is the only outer planet that is not a gas giant and its classification as a planet has come into question by scientists. The outer planets, except Pluto, are much larger than the inner planets and have thick, gaseous atmospheres, many satellites and rings. All the gas giants have rings and satellites.
Jupiter is the largest planet in the solar system. It takes about 12 Earth years for Jupiter to orbit the sun. Its atmosphere appears to be jet streams and huge storms, like the Great Red Spot.
Saturn has the most extensive ring system. The rings are narrow bands of tiny particles of dust,rock, and ice. Saturn is 95 times the mass of Earth and takes over 29 Earth years to orbit the sun. Saturn may still be forming. Saturn radiates more energy than the sun due to helium entering the central core from its outer layers. Saturn has 30 satellites.
Uranus and Neptune are blue giants. Methane gas gives both Uranus and Neptune the blue color. Uranus and Neptune have a thick atmosphere of hydrogen, helium, and methane. These gases are very cold due to the distance from the sun.
Uranus has the most extreme season in the solar system. The few clouds in the atmosphere show winds speeds of 200 to 500 km/h.
Pluto is the oddball planet and has recently been declared by some scientists to not be a planet. They believe it is a large satellite or asteroid.
Go to assignments and do questions 16-21.
The moon orbits Earth at a distance of 385, 000 km. The moon's surface is covered with craters, mostly caused by asteroid collisions early in the history of the solar system. The maria, or large, dark patches on the moon are seas of lava that flowed out of the moon's interior, filled the impact crater, and cooled to solid rock.
The moon has phases because it orbits Earth. Phases are the changes in the illuminated area of one celestial body as seen from another celestial body. The moon phases are shown below.
Moon phases are not caused by Earth's shadow. Eclipses occur when Earth, the moon and the sun line up. An eclipse is an event when the shadow of one celestial body falls on another. Eclipses on Earth are named for the object that is blocked. In a solar eclipse the sun is blocked by the new moon's shadow and a lunar eclipse is when the moon is blocked by Earth's shadow.
The moon affects Earth's tide. The moon's gravitational pull is strongest on the side near the moon, the water and land is pulled toward the moon, which creates a bulge. The movement of the water is more noticeable as it creates
Go to assignments and do questions 22-26.
Earth's Interior and Plate Tectonics
What is Earth's Interior like?
Earth is composed of an inner core, an outer core, a mantle, and a crust. The crust is the part we live on. Since it is relatively cool, it is made up of hard, solid rock. The continental crust averages 12- 25 miles deep. It is deepest on high mountains about 50 miles deep. Beneath the crust lies the mantle, a layer of rock that is denser than the crust and about 1800 miles thick. Earth center, the core, has two layers, the inner core which is solid metal and the outer core that is liquid metal. Earth's interior gets warmer with depth. The Earth's core is about 10, 800 degrees Fahrenheit. Radioactive elements contribute to Earth's high internal temperature. The radioactive isotopes of uranium, thorium and potassium release energy as their nuclei break up.
Alfred Wegener found that several continents' coastlines seem to fit together like a puzzle.
The supercontinent formed when all the continents were connected he called Pangaea. Wegener used fossil evidence to show that the same kinds of animals lived on continents that are now oceans apart. Evidence for Wegener's ideas came later. Continental drift theory was ignored until the 1960's when alignment of oceanic rocks supported the theory of moving plates.
Earth has plates that move over the mantle. The lithosphere is approximately 60 miles thick and is made up the crust and upper portion of the mantle. The lithosphere is made up of about seven large pieces called tectonic plates. The theory describing the movement of plates is called plate tectonics. Tectonic plates move at speeds ranging from 1 to 16 cm per year. It is unknown exactly why tectonic plates move. Some scientist believe that the plates are being moved around by convection currents in the asthenosphere or hot, plastic portion of the mantle.
Mid-oceanic ridges result from divergent boundaries, when two plates move apart. Hot rock rises from the asthenosphere and cools, forming new lithosphere rock. Oceanic plates dive beneath continental plates at convergent boundaries, when two plates come together. Subduction is the process by which one lithospheric plate move beneath another as a result of tectonic forces. Subduction of ocean crust generates volcanoes. Colliding tectonic plates create mountains. Transform fault boundaries, two plates slide along each other, can crack Earth. The crack where rock moves is called a fault.
Go to assignments and do questions 27-30.