Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Astronomy EEn.1.1 Explain the Earth’s role as a body in space Astronomy: Part 1 EEn.1.1.1 Explain the Earth’s motion through space, including precession, nutation, the barycenter and its path about the galaxy. Big Bang Theory • Hubble’s Law (1920’s) – All other galaxies objects of the universe are moving away from our galaxy • Redshift vs. Blueshift? – https://www.youtube.com/watch?v=th_9ZR2I0_w &index=95&list=PL908547EAA7E4AE74 How The Universe Came To Be… • The Big Bang Theory • Scientists believe that everything in the universe was together compressed as an infinitely small volume • 15 billion years ago in an explosive moment, the small volume began expanding at and incredible rate – In moments, the universe was already the size of the solar system Big Bang Theory Continued • After thousands of years of EXPANDING and cooling, matter was able to combine into separate entities forming galaxies and stars • Our Sun was created from a nebula – A swirling cloud of gas and dust – With the force of gravity, the cloud began collapsing on itself – The temperature increased to the point where nuclear reactions could occur- this is the birth of our Sun Nebular Hypothesis • Kant and Laplace (1800’s) – Theory that our Solar System originated from the collapse of a Nebula – http://csep10.phys.utk.edu/astr161/lect/solarsys/ nebular.html Formation of Our Solar System Formation of Our Solar System • Astronomers use Earth-based observations and data from probes to derive theories about how our solar system formed. • The significant observations related to our solar system’s formation include the shape of our solar system, the differences among the planets, and the oldest planetary surfaces, asteroids, meteorites, and comets. How did our Solar System form? A Collapsing Interstellar Cloud • Stars and planets are formed from clouds of gas and dust, called interstellar clouds or a nebula. • The interstellar clouds consist mostly of gas, especially hydrogen and helium that often appear as blotches of light and dark. • Many interstellar clouds can be observed along the Milky Way in regions that have relatively high concentrations of interstellar gas and dust. A Collapsing Interstellar Cloud • Our solar system may have begun when interstellar gas started to condense as a result of gravity and became concentrated enough to form the Sun and planets. – The collapse is initially slow, but it accelerates and the cloud soon becomes much denser at its center. – Rotation slows the collapse in the equatorial plane, and the cloud becomes flattened. – The cloud eventually becomes a rotating disk with a dense concentration at the center. Sun and Planet Formation • The disk of dust and gas that formed the Sun and planets is known as the solar nebula. • The dense concentration of gas at the center of this rotating disk eventually became the Sun. • In the disk surrounding the Sun, the temperature varied greatly with location. • As the disk began to cool, different elements and compounds were able to condense depending on their distance from the Sun which impacted the compositions of the forming planets. Formation of Our Solar System Sun and Planet Formation Merging into Planets – Jupiter was the first large planet to develop in the outer solar system. – As its size increased, its gravity began to attract additional gas, dust, and planetesimals. – As each gas giant acquired material from its surroundings, a disk formed in its equatorial plane, much like the disk of the early solar system. – In the disk, matter coalesced to form satellites. Formation of Our Solar System Sun and Planet Formation Merging into Planets – The inner planets also formed by the merging of planetesimals. – These planetesimals were composed primarily of refractory elements, so the inner planets are rocky and dense. – The Sun’s gravitational force is theorized to have swept up much of the gas in the area of the inner planets, preventing them from acquiring much additional material. – The inner planets initially ended up with no satellites. Formation of Our Solar System Sun and Planet Formation Debris – The amount of interplanetary debris thinned out as it crashed into planets or was diverted out of the solar system. – The planetesimals in the area between Jupiter and Mars, known as the asteroid belt, remained there because Jupiter’s gravitational force prevented them from merging to form a planet. Formation of our Solar System • Once our Sun was born… • The dust particles in our galaxy began to combine to form clusters • The clusters stick together to form rocks • Accretion occurs- gravity causes the rocks to combine forming planets • This completed the formation of our Solar System approximately 5 billion years ago • Evidence Supporting the Big Bang Theory – Everything is made of the same types of matter and elements – Red Shift Parts and Pieces of the Universe Universe: Everything! As far as you can see and then more! Galaxies: Groups of stars, dust, and gases held together by gravity. (Gravity is just an attraction between objects with mass!). We live in the Milky Way galaxy (100 billion stars!) Solar System: Planets orbiting a star. Our star is the SUN! The Universe’s Hierarchy • The Universe is made of billions of galaxies • Each galaxy contains approximately 500 billion stars • Some stars have planetary systems that rotate around it (similar to our solar system) • Each planet functions as a satellite – A celestial body orbiting a planet or object • The Earth is a satellite of our Sun More about gravity….. Gravity is a force that - holds us to the Earth - causes objects to fall to the ground - causes earth to go around the sun - causes the Sun to be pulled towards the center of the Milky Way Galaxy Gravity acts between any two objects even if they are far apart! The Greeks led the way! 600 BC – 150 AD: the Greeks used observations to develop philosophical arguments to explain natural events. Aristotle (350 BC) concluded that the Earth was round because it always cast a curved shadow on the moon when it passes between the sun and the moon. Greek Models of the Universe Geocentric Model: At first the Greeks though that Earth was motionless at the center of the universe and all planets orbited Earth. Heliocentric Model: Then they believed that the Earth and other planets orbited around the sun. Ptolemaic System: Later, they were able to account for the movement of the planets. Modern Astronomy was born! • Copernicus (around 1500) concluded that Earth is a planet just like the other 5 planets that were known at the time. He proposed a solar system model with the sun at the center and the planets orbiting in circles around it. • Keplar (around 1600) discovered three laws of planetary motion and determined that the orbits were elliptical rather than circular. Kepler’s First Law • Kepler -showed that planets revolved around the sun in an ELLIPSE rather than a CIRCLE. • This is an oval shape that is centered on two foci points • The major axis is the line that passes through both foci • Each planet has a different orbital size • Astronomical unit- a planet’s average distance from the Sun Kepler’s Second Law – An imaginary line sweeps out from the SUN to all of the planets EQUAL amounts of AREA in equal amounts of time. • Kepler’s Third Law – He found a mathematical relationship between a planet’s ellipse and its orbital period. – Kepler’s third law states P 2 = a 3, where P is a unit of time measured in Earth years, and a is a unit of length measured in astronomical units. Eccentricity • A planet in elliptical orbit is not at a constant distance from the Sun • Perihelion- when a planet is closest to the Sun in its orbit • Aphelion- when a planet is furthest away from the Sun in its orbit • Eccentricity- the length of the major axis of the elliptical orbit • This defines the exact shape of each planet’s orbit Motion in the Universe (Reference: www.astrosociety.org) Think about this… 1. The earth makes one complete rotation in about 24 hours (1000 miles/hour) 2. The earth makes one complete revolution around the sun in 1 year (66,000 miles/hour) 3. The sun (and the Earth!) move about toward the bright star Vega (43,000 miles/hour) 4. AND..the galaxy is spinning! Our sun (and the earth!) take one galactic year to make it around the Milky Way. (483,000 miles/hour). 5. Speed limit of the universe: 670,000,000 miles/hour (aka the speed of light!) Let’s discuss Earth’s motion.. • • • • • Precession Nutation Barycenter Rotation Revolution Precession (wobbling) A slow motion of Earth’s axis that traces out a cone over a period of 26,000 years. Earth’s rotation axis is not fixed! Today, the North Star is “Polaris”. In 13,000 years, the North Star will be “Vega. Precession is mostly caused by the gravitational influence of the sun and the moon pulling in the equatorial bulges of the earth Precession • Precession is the change in direction of the axis but not any change in tilt. • Change of tilt does not affect the seasons. Nutation • Nutation- a wobble of the precessional axis. • Slight change of 1/2° each way – • Occurs every 18 year period due to the gravitational pull of the moon. – This can increase seasonal affects Nutation (a wiggle in the wobble!) Barycenter • The common center of mass around which two or more bodies revolve • Due to the pull of the planets, the Sun is not still in the solar system; it rotates around a center of mass Earth-Moon Barycenter • The moon does not orbit the exact center of the Earth, but a point on a line between the Earth and the Moon about 1,710 km below the surface of the Earth. This is where their masses balance. The Sun never strays….. • The Sun never strays too far from the solar system’s barycenter! • Remember, the sun is not stationary in our solar system, but moves as the planets tug on it (gravity). Barycenter Rotation • Rotation is the turning, or spinning, of a body on its axis. • Rotation gives us day and night Daily Motions • The sun and moon rise and set everyday due to the Earth’s Rotation – The length of a day is the time needed for the Earth to make one complete turn on its axis – The time period from sunrise to sunset is called the solar day • This also controls our timekeeping system • Evidence for the Earth’s rotation include Foucault Pendulums and the Coriolis Effect Rotation of the Earth Affects Earth’s Shape The rotation of the Earth contributes to the shift of the shape of our planet. It is not a perfect sphere, but is flattened at the poles and has a bulge around the equator. Shape of the Earth • The Earth is NOT a perfect sphere but an ellipse. • The circumference of the Earth is larger around the equator than around the poles • There is an equatorial bulge created by the Earth’s rotation • A point on the equator is rotating faster than a point at the poles • This also causes a lower gravitational pull towards the equator – This is why many space stations/ launches are closer to the equator Revolution Earth revolves around the sun in an elliptical orbit. It takes a year for this to occur. Since the orbit is elliptical, Earth’s distance from the sun varies. Earth is closest to the sun at perihelion. Earth is farthest from the sun at aphelion. Annual Motions • The Earth year is 365.25 days- this is how long it takes for the Earth to orbit the Sun • The plane in which the Earth orbits about the Sun is the ecliptic – The Earth’s axis is tilted to the ecliptic about 23.5° • The Earth’s axis stays fixed even as the Earth orbits the Sun • At different times throughout the year, the Sun appears to be further away from the Earth. – This is the Earth’s altitude- the distance from the observers horizon to the object in the sky Earth • The Earth’s distance from the Sun allows water to exist in all three states of matter – Solid, liquid, and gas – This allows for life on the planet • The Earth’s dense atmosphere and a mild greenhouse effect makes conditions suitable for life The MOON REVOLVES AROUND EARTH in one MONTH. Motions of the Moon • One complete cycle of the moon goes through all of the phases – This lasts for 29.5 days ABOUT ONE MONTH. • Everyday the tide rises and falls due to the moon’s gravity and orbit – The effects of the tides can be increased by the Sun’s gravitational pull The Effects of Orbits • There is NOT always a solar eclipse, because the orbits have to line up in order to block the sun • The distance between the Sun, Earth, and Moon changes periodically – Perigee- the closest point in the Moon’s orbit to the Earth – Apogee- the furthest point in the Moon’s orbit to the Earth