What is the Universe Part 1
Where did Our solar System come from?
-stars and clouds form from interstellar clouds (nebulae) of gas and dust, mostly made of helium and hydrogen. -we can see theses all over the Milky Way Galaxy. -clouds begin to condense when gravitational pull of the matter in the clouds grow stronger. -this is likely how our solar system came to be. -tiny condensed particles of matter from within the interstellar cloud that started it all began to clump and bind a few billion years ago. -as the diameters of these objects grew, they became planetesimals. -as growth continued, some planetesimals were destroyed through meter collisions, but some survived and became the eight planets of our solar system. -the third planetesimal from the Sun became Earth. -scientists theorize that the first planet to form in our system was Jupiter, a gas giant and the fifth planet from the sun. -Jupiter kept growing larger and pulling remaining dust and debris from space into its orbit, like other gas giants. -this is likely why the interior planets (including us) remained small and rocky and initially without any satellites (moons). -some debris didn't get pulled into planetary orbit and makes up what is commonly known as an asteroid belt (between Mars and Jupiter). .What Happened To the "extra" Matter"
-some matter did not get pulled into a planetary orbit during the formation of or solar system. -meteor= "space trash" brunt up by our mesosphere. -meteorite="space trash" that comes in contact with Earths surface. -comets=small, icy bodies with highly eccentric orbits around the sun. -periodic comets=repeatedly orbit in the inner solar system (example): Haleys comet last seen in the year 1986, expected to been seen again in 2061 What is A Galaxy -galaxy: cluster or bunch of billion stars. There are 100 billion galaxies in the universe. -our neighboring galaxy, Andromeda, is 2.5 million light years from Earth! -we belong to the local group, a cluster of about 35 galaxies. Edwin Hubble -born in small-town Missouri 1889. -attend high school in Chicago, excelling academics and athletics. -attended college on scholarship, continuing sports and earned two degrees in mathematics and astronomy. -went to Oxford University of Law and quickly realized he wasn't satisfied and went back to school for his astronomical doctorate. -as soon as he was finished with his third degree he was drafted during WWI and didn't begin his career as an astronomer in California until 1917. -first person to see *other galaxies *develop a system to classify other galaxies *explain redshift *define the Big Bang Theory -also refined Einstein's of relativity. |
How Do We Know The Universe Is Expanding?
-Edwin Hubble discovered most galaxies use redshifts in their spectra. -redshift of an object in space depend on distance from Earth. -the farther away an object is, the faster it is moving. How Does The Night Sky Tell Us About The Past? -because many galaxies are so distant, it takes a long time for light to reach Earth. -(example): when we see sunlight, we are really seeing light the Sun produced eight minutes ago. Models Of The Universe -Big Bang Theory (Edwin Hubble): the universe began as a point and has been expanding ever since. (not really an explosion but an expansion). -Steady State Theory (Fred Hoyle): new matter has been created such that when objects in space move, new objects fill that void. (conflicts with the law of conservation of matter). Which Theory Is Right? -BOTH theories have observational tests to support them. -BUT evidence weighs in favor of the Big Bang. -if the universe began as a highly compressed point (as stated by Big Bang), then high temperatures and pressure would have created a great deal of high energy radiation. -in 1965, scientists discovered persistent background noise in a radio antenna caused by weak radiation. -this is believed to be remnant of the Big Bang, as the energy has shifted over time. -Steady State supporters have no explanation of this. What is Going To Happen To Our Universe?
1) Closed Universe (Big Church)-expansion will stop and shift to contraction. 2) Open Universe-expansion will continue forever. 3) Flat Universe (Big Chill)-expansion will slow to a halt in an infinite amount of time, but never contract. -the constant interaction between gravity (pressure in) and expansion (pressure out) will determine what happens. -one approach to determining the fate of the universe is to measure how much expansion has already slowed, using redshift of distant galaxies. -latest evidence: expansion has started to speed up again! We don't know what's causing it! -most evidence points to a flat universe. |
What Is The Universe Part 2 (motion in space)
The Heliocentric Model
-5000 ago until the 1500s, a geocentric view of planetary motion was widely accepted. -polish astronomer Nicholas Copernieus developed the first heliocentric model in which the planets orbit the sin in circles. Problems With The Geocentric Model - assumed that the planet and stars orbited a stationary Earth. -could not explain the apparent retrograde motion of some planets (Mars). -retrograde motion= planets further from the sun move slower in their orbit due to less gravitational pull and appear to move backwards. From Circles to Ellipses -danish astronomer Tyeho Brahe studied the movement of Mars taking nightly measurements WITHOUT a telescope Brahe's Apprentice -Johannes Kepler was in the right place at the right time and use Brahe's data to proposed the first of a set of three laws that are named after him. Kepler's Laws -all planets move around the sun in ellipses. - imaginary lines connecting the sun to each planet sweeps equal areas in equal time. -the relationship between a planets ellipse and its orbital period is: P2= a3 (where P equals the orbital period and a equals the length of the semi-major axis). |
Eccentricity
-due to its elliptical orbit, a planet is not at a constant distance from the sun. -Perihelion= closest to. -Aphelion= farthest from. Kepler's Second Law a planet sweeps out equal area in equal time. Kepler's Third Law -the farther a satellite is from the object it is revolving around: 1. The longer it will take to complete an orbit 2. The greater the distance it will travel to complete the orbit. 3. The slower its average speed of motion. Newtons Laws (Physical Science Review!) 1. An object in motion tends to stay in motion UNLESS an outside forces act upon it. 2. An object accelerates in the same direction of the force applied. 3. For every action, there is an equal and opposite reaction. Kepler+Newton -gravity pushes planets towards the sun. -the gravitational force holding the planets on their Why does the night sky change? Parallax -an apparent change in the direction of an object, caused by a change in observational position that provides a new line of sight. Procession -Earths wobble on its tilted axis -it takes the Earth about 26000 years to wobble -it is caused by a tug of war on Earth by the Sun and the Moon, but the Moons pull is stronger due to proximity. |
What is the Universe Part 3
What make Our Moon Weird?
-Large in comparison to the planet the it orbits. -27% the radius of Earth. -great distance from Earth (most moons are closer). -solid rocky composition (most are icy). Moon vs. Earth differences -the moon can get reaaalllly hot and cold (127 C, -173 C), but because it has no atmosphere, it does not retain heat in the absence of the sun. -no erosion wind or water similarities -areas of high elevation (highlands) and low elevations (maria and craters). -very similar mineral content. How was the Moon Formed? -capture theory: as the solar system was forming, an object come too close to the forming Earth and got sucked into our gravitational pull. -simultaneous Formation Theory: the moon and Earth formed at the same time and in the same area (thats why compositions are similar). -impact theory: the moon formed as a result of the collision of Earth and A Mars-sized object about 4.5 billion years ago. Debris from merged together to form the moon (most widely accepted). Motions of the Moon -it takes 27.3 days to orbit around Earth; it also takes 27.3 days to complete one revolution on its own axis causing a moon "day" and a moon "year" to be the same length of time. -the sames side of the moon always faces Earth. The "far side" of the moon always faces away from the Earth. Phases of the Moon: -the moon does not produce its own light, in\stead it reflects the light from the sun. -the moon has 8 phases and goes through the whole set once a month, or 29.5 days -What Causes Phases? the phase of the moon you see depends on how much of the sunlit side of the moon faces Earth. |
The Cycles of the Phases:
-from one full moon to the next it takes about 29.5 days -the 8 phases of the moon in order are: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, Waning Crescent. Eclipses -when the Moons hits Earth or Earths shadow hits the moon, an eclipse occurs. -there are 2 types of eclipses: solar (sun) eclipse and lunar (moon) eclipse. -the type of eclipse is named for what is being blocked form Earth. Solar Eclipse -the umbra is the darkest and smallest part of the shadow and is coned shaped (total darkness). -the penumbra is the largest part of the shadow (partial darkness). -Total Solar Eclipse -only people in the umbra experience a total solar eclipse. -Partial Solar Eclipse -in the penumbra, people only see a partial eclipse; since part of the sun is still visible, it is not safe to look directly at the eclipse. Lunar Eclipse -during a full Moon the Earth blocks the suns light from reaching the Moon making the Moon look dark from Earth. -Total Lunar Eclipse -when the Moon is in the Earths umbra, there is a total Lunar eclipse. -Partial Lunar Eclipse -the Moon passes partly into the umbra of the Earths shadow. The Tide Cycle -the Moons gravity pulls Earths water towards itself and away from two opposite places, creating low tides. -all 4 tides rotate in a 35 hour cycle. Spring and Neap Tides -Spring Tides occur twice a month, one at full moon, one at new moon. -the combined force of the sun and moons gravity make a tide with the most intense high and low tide. -Neap Tides happen 2 times a month, one at first quarter moon and one at third quarter moon. -the sun and Earth are at right angles and creates tides with the least intense difference between high and low. (Its like tug-of-war between the moon and sun). |