User:Astronomymaster

Account created for participation in Phy 1060

All project information taken from textbook: *Astronomy

My Miraheze thread https://wright068.miraheze.org/wiki/Main_Page



Notes on Chapter 4
Please feel free to comment or change any notes, these are a work in progress and will constantly be added to

Chapter 4 key objectives: Identify why the earth is different temperatures in different places, why the seasons occur, the lunar phases and what they mean, and the earths motion cause and effects

4.1 Key objectives: Latitude and longitude, right ascension + declination

 * Latitude and longitude create a grid on the earth to easily find any location based on 360 degree circles around the globe
 * Earth is always rotating to the east
 * Meridian are great circles that are perpendicular to the equator
 * Greenwich, England is the prime Meridian- located at longitude 0
 * Equator is latitude 0, making the north pole 90 N and the south pole 90 S
 * Declination and Right Ascension (RA) do the same thing as latitude and longitude but used on a hypothetical Celestial Sphere
 * Celestial Sphere makes the whole universe (that we know) into a massive sphere so that we can add circles to it and map the universe
 * RA lines can be measured in degrees or time, 1 hour of time is equal to 15 degrees thus making 24 hours 360 degrees

4.2 Key objectives: Learn how the seasons differ with the latitude on the earth, learn how the tilt of the earth on its axis causes the seasons

 * Seasons are caused by varying amounts of sunlight (see figure to right)
 * Seasons in the southern hemisphere are opposite of those in the northern hemisphere
 * Earths distance from the sun DOES NOT effect the changing seasons, in North America earth is closest to the sun in January
 * Earth is on a 23.5 degree tilt
 * Summer Solstice (June 21) is when the sun shines directly on the northern hemisphere, causes us warmer weather and longer days
 * During the northern summer solstice the north pole has up to 24 hours of sunlight while the south pole has 24 hours of dark
 * If the earth were tilted less the seasons would be less extreme
 * March 21- Sep 21 (halfway between solstices) everywhere on earth gets approx. 12 hours of sunlight

4.3 Key Objectives: Explain the difference between solar and sidereal day, explain the reason for time zones

 * Solar day = rotation of the earth with respect to the sun
 * Sidereal day= rotation of the earth with respect to the stars
 * Solar day is slightly longer than a sidereal day because the earth not only has to rotate in a circle but also travel around the sun, this time is approx. equal to 1/365 of a day or about 4 minutes
 * Apparent solar time = time that is defined by the actual position of the sun in the sky, or below the horizon
 * Because the exact length of a solar day can vary from year to year it became necessary to abandoned the solar day once cloths that ran at a uniform rate were invented
 * This ended up creating Mean Solar Time which is based on the average value of a solar day over one year
 * Noon is of course when the sun is at the highest point in the sky and due to the sun being at its highest point at different times in different places it created the need for time zones
 * 24 global time zones
 * Russia and China only use one time zone for their entire country
 * Daylight savings time is of course only there to prolong sunlight into the evening hours and does not actually add more sun to the day
 * The International Date Line is there to set an official date so you couldn't hypothetically go forward or backward in time, when you cross it you either advance a day or go back a day

4.4 Key Objectives: Understand the calendar and explain origins of modern calendar

 * Tropical year- Basic period of revolution of the earth = 365.2422 days
 * Stonehenge was an early calendar used to align sun or moon during critical times of the year
 * Our calendar is originally derived from ancient Sumerians it was later revised by the Romans and dubbed the Julian Calendar which has 365 day years except every 4th year there is 366 days
 * This calendar was slightly off and by the 16th century the world was off by approx. 11 days causing Galileo to work on a revised calendar
 * The Gregorian calendar (created by Galileo) made centuries divisible by 400 only leap years thus 17-1900 which were divisible by 4 but not 400 were not leap years
 * To this day we use the Gregorian Calendar

4.5 Key Objectives: Explain cause of lunar phases and understand how the moon moves around the earth

 * The phase the moon is in depends on the angle the sun's rays hit the moon
 * New Moon is when the moon is in the same direction as the sun
 * The moon is the distance of 30 earths away from us
 * When the earth's shadow falls on the moon is causes a lunar eclipse
 * The moon rotates on its axis at exactly the same time it takes to revolve around the earth so we can only ever see one side of it
 * Scientists call the above effect: Synchronous Rotation
 * Therefore every side of the moon gets equal sun, but we can only ever see one side. There is no dark side to the moon

4.6 Key Objectives: Describe what causes tides

 * Gravity from the moon slightly pulls at the earth causing tides
 * Gravity from moon is too insignificant to truly effect anything besides water
 * Moon does not lift, compress, or expand water, it flows towards the place the earth is closest to the moon, and the polar opposite side
 * This causes the water to pile together in these areas
 * Sun also effects the tides, but only about half as much as the moon
 * Neap Tides: Tides that are lower than usual because the sun is partially cancelling out the moon

4.7 Key Objectives: Describe what causes eclipses, difference between a total and partial solar eclipse, and why lunar eclipses are so much more common

 * Solar eclipse- Moon blocks the sun
 * Lunar eclipse- Moon passes through the shadow of the earth
 * Umbra- cone within wich a planets shadow is darkest
 * Penumbra-lighter more diffuse region of darkness
 * Total Solar eclipse- Moon completely covers the sun
 * Solar eclipse are more rare because the moon and sun travel different paths in the sky
 * Lunar eclipses happen once almost every 4 full moons
 * we can predict ecplipses centuries in advance

Chapter 4 Quiz
{Why were latitude and longitude created?} -To easily find the equator +To easily find location based on 360 degree circles around the globe -To easily find the prime meridian -To easily locate the hemispheres

{Where is the prime meridian?} -Quebec, Canada -Munich, Germany -New York, USA +Greenwich, England

{In what direction is the earth always rotating?} -towards the North +towards the East -towards the South -towards the West

{Seasons are caused by what?} -Distance from the sun to your location on earth -The Earths rotation +Varying amounts of sunlight -The Earths tilt

{What is it called when the sun shines directly on the northern hemisphere?} +Summer solstice -Winter solstice -Spring equinox -Fall equinox

{How many time zones does the Earth consist of?} -9 -18 -50 +24

{What two countries only use one time zone for their entire country?} +Russia + China -India + Korea -Australia + Mexico -Norway + Ireland

{What does daylight savings time do?} -Saves time -Adds more sun to the day +Prolongs sunlight into the evening hours -Removes sunlight from the day

{What is Mean Solar Time?} +Average value of a solar day -Markings that indicate time by the position of a shadow -Time found by the position of the sun in the sky -Average time between planets and the sun

{How long is a tropical year?} -365 days +365.2422 days -366 days -366.2432 days

{What calendar do we use today?} -Stonehenge -Greek -Mayan +Gregorian

{What calendar was used to align the sun or moon during critical times of the year?} +Stonehenge -Greek -Mayan -Gregorian

{What causes the phases of the moon?} +Angle of suns rays on the moon -The oceans tides -Gravitational pull -Rotation of the Earth

{When is there a new moon?} -When the moon is the opposite direction of the sun +When the moon is the same direction as the sun -When you can see all lit parts of the moon -When the moon is in opposition

{Why is there no 'dark side' of the moon?} +Every side gets equal sun, but we only ever see one side -The moon is always glowing -The moon is always rotating -There is a dark side of the moon

{What do scientists refer to as the effect that causes us to only see one side of the moon?} -Earth's rotation -Synodisch rotation +Synchronous rotation -Sidereal rotation

{What causes tides?} +Gravity from the moon pulling the Earth -Wind and other weather -The Earth's rotation -The Earth's gravity

{What is most effected by the moons gravity?} -Air -Sunlight +Water -Hydrogen

{Other than the moon what else effects tides?} -Wind +Sun -Jupiter -Carbon

{Which term describes tides being lower due to the sun cancelling the moons gravity?} -Low Tide -Rip Tide -High Tide +Heap Tide

{A cone in which a planets shadow is darkest is called...} -Aurora -Lunation +Umbra -Perigree

{How often do lunar eclipses occur?} +Every 4 full moons -Every 2 years -Every 2 full moons -Every 4 months

{Why are solar eclipses so much rarer than lunar?} -Part of the sun covers the moon -Earth's rotation prevents us from seeing them -Sun is too much bigger than the moon +Moon and sun travel different paths in the sky

{A penumbra is________} -Steady flow of particles streaming from the sun -Dark, inner part of sunspot +Lighter, more diffuse region of darkness in a planets shadow -A distant, but bright object

Comment: I like over half your questions. That "aint" bad, because I can ignore the ones I don't like. Keep up the good work!Guy vandegrift (discuss • contribs) 04:07, 9 March 2018 (UTC) S

Notes on Chapter 25
Please feel free to comment or change any notes, these are a work in progress and will constantly be added to until completion of the project

25.1 Key Objectives: Describe how and how we determine the Milky Way Galaxy's structure, Identify main components of the galaxy

 * 1610 Galileo made his first telescope survey of the Milky Way Galaxy
 * Hard to map our galaxy from within due to an extreme amount of dust and also hard to tell where we are due to being in the middle of it
 * 1785 Herschel was the first to realize that most of the starts lay on a flattened structure, and hypothesized that the Milky Way was a disc with the sun near the center
 * 1917 Shapley realized that the sun was not in the center of Milky Way
 * We now know that the Milky Way is a disc with a series of spiral arms
 * We can tell this due to infared imaging
 * There is a bulge of stars in the center of the Milky Way
 * Dark Matter- invisible mass within the Milky Way, we can only tell it is there because of its gravity
 * Milky Way is made up of disks and halos, halos being the outermost parts of the galaxy

25.2 Key objectives: Compare models for formations of spiral arms

 * Radio observations revealed 2 major arms in Milky Way
 * Sun is on a short arm called the Orion Spur
 * Galaxy is rotating like our solar system
 * Differential Galactic Rotations= Objects farther from the central bulge of our galaxy move slower around the galaxy
 * New galaxies do not have a spiral structure

25.3 Key Objectives: Describe attempts to determine mass of galaxy, how do we know about dark matter

 * Earth orbits the Milky Way every 225 million years
 * We use information about the Suns orbit around the galaxy to estimate its mass
 * Milky Way is approximately 100 billion times the mass of the sun when we use this method
 * Hard to weigh the Milky Way due to dark matter
 * Scientists have no idea what dark matter is made up of, can only detect it is there due to the gravity it gives off
 * Some scientists hypothesize it is made of subatomic particles not yet detected on earth

25.4 Key Objectives: Describe radio and x-ray observations- Discuss how these can be used to determine mass of central bulge

 * There is a black hole in the center of our galaxy with a mass approximately equal to 4.6 billion suns
 * Radio imaging allowed us to take our first look at Sagittarius A (region that is the center of our galaxy)
 * Some stars can form near the 'super massive black hole' at the center of our universe, and scientists aren't sure how
 * No star formations directly in the galactic center
 * Scientists prove that the black hole in center of galaxy exists by observing gravity from that area, and noticing it is far greater than anything we know of could exert. BUT they can't actually see the black hole to prove it
 * Kepler's 3rd law combined with observations of starts orbits around the center of the galaxy allow us to estimate the black holes mass
 * Rotation of dust around Sagittarius A show its size to be less than .3 AU
 * Where did super massive black hole come from theories include: Dust and gas collapsed to form it--- massive star explosion--- many starts collapsed together at the same time
 * Once black hole was formed it fed off of other nearby stars to get to the mass it is now, and it is still growing consistently

25.5 Key Objectives: Distinguish between pop 1 and pop 2 stars, explain why oldest stars in galaxy don't have many heavy elements

 * Stars on galaxies spiral arms are bright blue and pop 1 starts
 * Stars on halos and global clusters are pop 2
 * Pop 1= Stars of all ages
 * Pop 2= Only older stars
 * Older stars are less abundant in materials because when they were forming and growing there were not as many resources for them to acquire
 * The sun is a pop 1 star

25.6 Key Objectives: Describe how the collapse of 1 cloud and mergers with other galaxies formed the Milky Way

 * Oldest stars in our galaxy are 13 billion years old so we assume that's how old our galaxy is
 * Protogalactic clod collapsed to form a thing rotating disk which collapsed and clumped together due to gravity to form starts and our early galaxy
 * Our galaxy began to slowly tear apart other less massive galaxies that got too close
 * Evidence of at least 12 galaxies that the Milky Way has 'eaten' so far
 * In 3 billion years the Andromeda galaxy will 'eat' the Milky Way galaxy

Chapter 25 Quiz
{In 1610 Galileo made his first telescope survey of what?} -Andromeda Galaxy +Milky Way Galaxy -Black Eye Galaxy -Messier 82

{What best describes the Milky Way Galaxy?} -Eliptical -Lenticular -Irregular +Disc with a series of spiral arms

{What is in the center of the Milky Way?} +Bulge of stars -Moons -Planets -Halos

{What is the invisible mass within the Milky Way referred to as?} -Space -Dust +Dark Matter -Hydrogen

{The sun is located on a short arm of the Milky Way galaxy called...} -Annular +Orion Spur -Aerolite -Taurus Ring

{T/F The Galaxy rotates around the center similar to our solar system} + True - False

{New Galaxies do not have...} + A spiral structure - An abundance of stars -A lot of dust -Large amounts of gas

{How often does the Earth orbit the Milky Way?} -225 billion years -25 million years +225 million years -25 billion years

{Which is one way we estimate the Milky Ways mass?} -Balance +Sun's orbit around the galaxy -Radius -Gravitational force

{How big is the Milky Way's estimated mass?} -100 billion x mass of earth -10 billion x mass of sun -10 billion x mass of earth +100 billion x mass of sun

{What allowed us to take our first look a Sagittarius A?} -Telescope -Supernova +Radio imaging -Wavelengths (similar to echolocation)

{What allows us to estimate the 'super massive black hole's' mass ?} +Keplers third law -Newtons law -A scale -Telescope

{How do we know Sagittarius A is less than .3 AU in size?} -Disks -Gravity -Gasses +Rotation of dusts

{What color are the majority of stars on the galaxies spiral arms?} -Purple -Green +Bright blue -Yellow

{What population star is the Sun?} -Pop 3 +Pop 1 -Pop 4 -Pop 2

{Why are older stars less abundant in heavy molecules?} -Left the planet +Not many for them to acquire when they were growing -Stolen by new stars -Unknown to scientists

{How old are the oldest stars in our galaxy?} -33 billion years old -10 million years old -50 million years old +13 billion years old

{What did our galaxy do to other smaller galaxies that got too close?} -Pushed them away +Slowly tore them apart and absorbed their stars -Traveled around them -Began rotating around them

{How many galaxies has the Milky Way 'eaten' so far?} -3 -25 +12 -100 or more

{What galaxy will inevitably 'eat' the Milky Way in about 3 billion years?} -San Andreas +Andromeda -Sagittarius A -Messier 82 