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230 Cards in this Set
- Front
- Back
Celestial Sphere
|
the illusion that stars lie on a sphere surrounding the earth
-greeks -illusion bc lack depth perception when look into space (bc stars so far away) -helps us map the sky |
|
Celestial Equator
|
projection of Earth's equator into space
(complete circle around celestial sphere) |
|
Celestial Poles
|
1)NORTH CELESTIAL POLE:
point directly above earth's N pole 2)SOUTH CELESTIAL POLE: point directly above earth's S pole |
|
Ecliptic
|
path the sun appears to follow when circling around the celestial sphere
-crosses celestial equator at 23.5* bc thats the TILT of earth's AXIS! |
|
Meridian
|
imaginary halr circle from S horizon through the zenith to N horizon
(zenith = direct pt overhead) -used as reference for locating objects |
|
Rotation
|
spinning of object around axis
(earth rotates once on axis a day) (axis = imaginary line from N pole to S pole thru center of earth) |
|
Revolution
aka Orbit |
orbital motion of one object around another
(earth orbits sun once each year) |
|
Precession
|
slowly / gradually changes orientation of earth's axis
-direction axis is pointing changes -bc axis now points to Polaris thats the north star (so N star will change over time) -does NOT affect amt of axis tilt (or season pattern) -causes constellations that correspond to the solstices & equinoxes to change (bc that depends on the direction earth's axis pts in space) --caused by gravity's effect on tilted, rotating object thats NOT a perfect sphere -stays upright bc rotating objects tend to keep spinning around same axis [law of conservation of angular momentum]-- prevents gravity from pulling top over |
|
Solar System
|
the sun and all the objects that orbit it
[planets moons, asteroids (rock chunks), comets (ice balls), & particles of interplanetary dust] |
|
galaxy
|
an island of stars in space
-a few hundred million to > a trillion stars (Milky Way = large: >100billion stars --our solar system = halway from center to edge of disk) **individual galaxies do not expand while universe continues to (due to gravity) |
|
Galaxy Clusters
|
groups of galaxies
(we're in the LOCAL GROUP) |
|
superclusters
|
areas where galaxy clusters are tightly packed
(we're in the LOCAL SUPERCLUSTER) -between these galaxy groupings is huge empty space |
|
Universe
|
sum total of all matter and energy
-including all superclusters and all voids between them |
|
"cosmic address"
|
-Earth
--Solar System ---Milky Way Galaxy ----Local Group -----Local Supercluster ------Universe |
|
Big Bang
(age of universe?) |
when universe expansion began
-produced only 2 elements: 1)HYDROGEN 2)HELIUM (14 billion years ago) -first / simplest atoms created -more complex atoms created in stars -when stars dies atoms expelled into space to make new stars / planets *we're starstuff* |
|
Scale of the Universe
|
-10 Billion Light Years across
-~10^22 stars in the universe |
|
Universe when Sun = grapefruit?
|
Earth = ballpoint
Jupiter = marble |
|
Life of Stars
|
Birth = in clouds of gas / dust
shine due to NUCLEAR FUSION: -atomic nuclei smash together and stick to make heavier nuclei (happens thruout life) DIE: when it exhausts all usable fuel for fusion ---->splits off & can eventually form new stars / planets |
|
all elements besides
Hydrogen & Helium were made by: |
1) NUCLEAR FUSION
or 2)NUCLEAR REACTIONS |
|
age of solar system?
|
~ 4.6 bya
|
|
speed of light
|
300,000 km/s
(light takes 8 min from sun to earth) |
|
light-years
|
10 trillion km / yr
---- measures how long it takes stars to reach us (bc so far away) *unit of DISTANCE not time* *the farther we look in the distance the further we look back in time* |
|
"observable universe"
|
portion of the entire universe that we can potentially observe
CONSISTS ONLY OF OBJECTS THAT LIE W/I THE PAST 14 BILLION LIGHT YEARS (beyond that - 15 bill light years would be looking to before the universe existed -- nothing to see) |
|
nearest star?
(other than our sun) |
Alpha Centauri
(4.4 light years away) -3 star system |
|
Earth rotates what direction
Sun & Stars appear to rise/set what direction? |
from WEST TO EAST
(counterclockwise from above N pole) --why Sun / Stars APPEAR to RISE in EAST & SET in WEST |
|
Ecliptic Plane
|
a flat plane defined by earth's orbital path
(1 AU = line from earth to sun on plane) |
|
Earth orbits sun what direction?
|
COUNTERCLOCKWISE
(same direction it rotates) |
|
*the entire milky way galaxy is rotating*
|
*also!**most of he mas of galaxy is located outside the visible disk in the galaxy's "halo"
--no light coming from it so termed "DARK MATTER" *some galaxies orbit the milky way* *milky way is moving toward the Andromeda Galaxy* |
|
Hubble Telescope
(date & 2 facts) |
1920s by Edward Hubble
discovered: 1)virtually ever galaxy outside our Local Group is moving AWAY from us 2)the more distant the galaxy the faster it appears to be moving away *due to the fact the ENTIRE universe is expanding |
|
Think about universe in 4 dimensions
|
1) length
2) width 3) depth 4) TIME |
|
1 km =
__ miles |
1 km = .62 miles
|
|
1 AU =
__ miles |
1 AU = 93,000,000 miles
|
|
1 Light-Year =
___ AU |
1 Light-Year = 63,000 AU
|
|
1 Parsec =
___ Light-Years |
1 Parsec = 3.26 light-years
|
|
"Parsec"
|
the distance to an object with an angle of ONE ARCSECOND
is 1 parsec (parsec is equiv to 3.26 light years) |
|
"Constellation"
|
region of the sky with well-defined borders
(set by IAU [international atronomical union]) --divided sky into 88 constellations |
|
"angular size"
|
the angle it appears to span your field of view
*each degree is divided into 60 arcminutes divided into 60 arcseconds* |
|
"angular distance"
|
angle appearing to seperate 2 objects
*each degree is divided into 60 arcminutes divided into 60 arcseconds* |
|
circumpolar stars
|
near north celestial pole
-never rise or set -ALWAYS above horizon -make daily counterclockwise circles |
|
"declination"
|
aka LATITUDE
-degrees N or S of the equator |
|
"right-ascension"
|
degrees East of the
Prime Meridian (prime meridian is 0* longitude) |
|
how long is ONE revolution
of earth? |
365 1/4 days
|
|
when in N hemisphere
all stars appear to rotate |
AROUND POLARIS
(the N star) |
|
at Equator all stars appear to move
|
vertically up & down
|
|
Summer Solstice
|
when sun is @ farthest pt North on Celestial Sphere
-moment when N hemisphere receives most direct sunlight |
|
Winter Solstice
|
when sun is @ farthest pt South on Celestial Sphere
-moment when N hemisphere receives least direct sunlight |
|
Vernal Equinox
|
day when sun is directly above celestial equator
(IN SPRING) -moment when N hemisphere goes from tipped away from the sun to tipped toward the sun |
|
Autumnal Equinox
|
when sun is directly above celestial equator
(IN FALL) -moment when N hemisphere goes from tipped toward the sun to tipped away from the sun |
|
in winter we are NOT farther from the sun
|
our part of the globe is simply tilted away from the sun,
causing us to receive less energy (longer shadows) |
|
one complete precession (wobble)
-how long? |
every 26,000 years
|
|
Lunar Eclipse
|
-moon passes thru earth's shadow
(earth between moon & sun) *red moon* |
|
Solar Eclipse
|
-moon's shadow moves across earth
(moon between sun and earth) *ring of sunlight* |
|
"parallax"
|
near objects appear in different places when viewed from different locations
-used by astronomers to determine distance |
|
Zodiac
|
the constellations along the ecliptic
(the ecliptic is the path the sun takes on the celestial sphere) |
|
during summer sunlight strikes at a steeper angle
|
the steeper angle makes sunlight more concentrated
-in summer the sun follows a longer and higher path thru the sky --->days longer w/ short midday shadows |
|
Qualities of the Equinoxes
|
-only 2 days of year that sun rises exactly due east and sets exactly due west
-2 days when sunlight falls EQUALLY on both hemispheres -(summer solstice = 1st day of summer) -reflect Northern seasons (equator gets most direct sunlight on 2 equinoxes and least on the solstices) |
|
why
N Hemisphere's seasons are more extreme than the S hemisphere's |
-most of earth's land lies in N hemisphere
--ocean resists temp changes -earth moves faster in orbit when closer to sun and slower when farther (moves slower during N hemisphere's summer -- when earth's farther from sun)(& N hemisphere's summer lasts couple days longer due to this) |
|
length of
Moon's orbit |
27 1/3 days
*moon's ~380,000 km from earth |
|
"lunar phases"
|
the cycle of the moon as it moves thru the sky
-thru cycle appearance & times of rising and setting change -phase depends on moon's position relative to sun as it orbits earth |
|
phases of moon result from 2 qualities
|
1) half the moon always faces the sun while other half faces away
2) as you look at the ball at different positions in orbit you see different combinations of bright & dark faces *different phases reach their highest pts @ different times |
|
waxing phases
|
phases from new to full
|
|
waning phases
|
phases from full to new
(waning = decreasing) |
|
moon phases listed
|
-new moon
-waxing crescent -1st Quarter -Waxing Gibbous -Full Moon -Waning Gibbous -3rd Quarter -Waning Crescent |
|
"synchronous rotation"
|
the fact that the moon rotates once on its axis in the same amt of time it makes 1 orbit around earth
**CAUSES US TO ALWAYS SEE THE SAME FACE OF THE MOON**(though see different phases) |
|
New moon occurs ....
|
when moon is between sun & earth
*if on moon you see full earth when its a new moon* {*always the OPPOSITE phase! if u were on moon*} |
|
moon passes thru ecliptic plane
|
only twice each orbit
|
|
"nodes"
|
the 2 pts in each orbit @ which moon crosses the ecliptic plane
|
|
2 conditions for an eclipse to occur:
|
1) phase of moon must be
full (for lunar) or new (for solar -bc these are the only phases in which earth moon & sun lie in a straight line) 2)the new or full moon must occur when the nodes of the moon's orbit are aligned w/sun and earth (because thats the only time new and full moons are on the ecliptic plane) |
|
"umbra"
|
where sunlight is completely blocked (central)
|
|
penumbra
|
where sunlight is only partially blocked
(lighter than umbra) |
|
lunar eclipse
when happens when total / when partial |
begins the moment moon's orbit carries it into earth's penumbra
(passes thru earth's umbra when perfectly alligned [total lunar eclipse]) Partial Lunar Eclipse: -only part of full moon passes thru the umbra Penumbral Lunar Eclipse: -moon passes thru earth's penumbra only |
|
"totality"
|
time when moon is entirely engulfed in the umbra in
LUNAR ECLIPSE dark and red (due to earth's atmosphere scattering some sunlight) |
|
Solar Eclipse
|
Total Solar Eclipse:
-anyone in the area where moon's umbra touches earth's surface Partial Solar Eclipse: -anyone w/i the moon's penumbral shadow (only part of the sun blocked from view) Annular Eclipse: -when moon's far away from earth & umbral shadow doesn't reach earth *RING OF SUNLIGHT AROUND DISK OF MOON* |
|
"eclipse seasons"
|
2 periods each year when nodes of moon's orbit are aligned w/ sun
|
|
"saros cycle"
|
eclipses recur in cycle of ~ 18 yrs & 11 days
|
|
5 planets to see w/ naked eye
|
Mercury
Venus -early evening / early morning Mars -reddish color Jupiter -2nd brightest when visible Saturn |
|
"apparent retrograde motion"
of the planets |
planets usually move eastward relative to stars but occasionally reverse course & move westward
|
|
"steller parallax"
|
apparent shifting of stationary object when looking from different locations (or different eyes)
*why greeks rejected a sun-centered model* -stars are so far away that stellar parallax is undetectable to naked eye [nearby stars should appear to shift back and forth against distant stars bc we view stars from different places in our orbit at different times] |
|
ancient astronomy
how old? |
17,000 BC
|
|
benefits of keeping track of astronomy
|
social / religious needs
agriculture (when to plant / harvest) religion (gods control heavenly events) |
|
ancient egyption astronomy
|
-used diurnal motions as a clock
-developed 365 day calandar -some pyramids associated w/ important celestial events |
|
babylonia
ancient astronomy |
-developed 60 based counting system
(still used for min, sec, angles) -tables of planetary motion -prediction of eclipses &heliachal rising (first appearance after being too close to sun) - |
|
china
ancient astronomy |
-records well preserved -- date back 3000 years
-oldest records of comets / eclipses / sunspots -**Recorded supernovae** -astronomy was tied to gov't -astr declined in imp after 1200 AD |
|
greeks
ancient astr |
-defined modern constelations & many star names
-developed mythological stories about constellations |
|
mayans of central america
ancient astr |
-complicated, highly accurate calandar system
-precise tables for motions of moon & venus -timed some wars on positions of venus & jupiter -predicted eclipses -milky way was "origin of all life" "world tree" -built many observatories correlated w celestial allignment |
|
Incas of S america
ancient astr |
Cuzco (capital) laid out to mimic sky &
point to specific horizon risings --sun's movement thru pillars marked time to plant at different altitudes --nearly every temple had astrological allignments |
|
Celts
ancient astr |
-stonehenge 2000 bc
--->prob not associated w/ astr calendar |
|
native N americans
ancient astr |
-tracked stars to predict season change
----indicated when time to relocate |
|
heliocentric universe
|
COPERNICUS
-planets revolve around sun |
|
geocentric universe
|
developed by ancient greeks
-advocated by church -didn't explain varying motion of the planets |
|
Copernicus
|
-heliocentric universe
-determined mercury & venus closer to the sun than earth -estimated rotation periods and distances between planets & sun [1] |
|
Brahe
|
-oversaw building of first modern observatory
-first to record detailed motions of planets -recorded magnitude / brightness of supernovae (exploding star) ----disproved greek notiont that stars are close to earth and never change [2] |
|
Kepler
|
worked w/ brahe
developed 3 laws of planetary motion: 1)a planet's orbit is an ellipse w/ the sun at one focus 2)planets speed up when near the sun 3) P^2 = a^3 (P = orbital period (yrs) a = length of semi-major axis) ---plants closer to sun have shorter year than those farther away |
|
Galileo
|
discovered jupiter's moons
(not only earth has satellites) -telescope observations supported heliocentric view -church put him under house arrest |
|
Newton
|
first to decribe
-physical motion -concept of gravity -unified physical view of the universe -invented calculus -until him no one understood why planets moved -developed model that showed gravity was responsible in keeping planets in orbit -mathematically proved kepler's 3 laws of planetary motion |
|
Newton's laws of motion
|
1) Law Of Inertia:
-obj at rest will remain at rest -obj in motion will remain in motion -unless acted upon by an outside force 2)F = (m)(a) -force = (mass) (acceleration) -force causes accelleration (change in velocity) -force causes change in momentum -weight = (mass)(g) 3)for every force there is an equal and opposite reaction force |
|
because of newton we now know....
|
earth has an equatorial bulge (from moon pulling on us)
-led us to discover neptune |
|
ealiest known astronomical records?
|
AFRICA
-predicted weather from moon -Carved Lunar Calendar |
|
Seven days a week from?
|
seven naked-eye objects that appeared to move among constellations:
Sun, Moon, & 5 planets recognized [mars, mercury, jupiter, venus, saturn] |
|
egyptions
|
obelisks determined time of day
-divided day & night into 12 parts ---> varied in length bc amt of daylight varies during the year -eventually built water-clocks (like hourglass) |
|
determining time of day at night
(ancient people) |
-by position and phase of moon
[first quarter moon sets ~ midnight] -positions of the stars [different constellations rise at different times during different months] |
|
the study of ancient structure in search of astronomical connections?
|
archaeoastronomy
-evaluates structures to see any particular astronomical allignments |
|
Pyramids
|
egyptions
--oriented with cardinal directions |
|
developed arithmetic for later astronomical calculations?
|
babylonians
|
|
Copernicus
|
SUN CENTERED MODEL
-adopted model that allowed him to calculate a planet's orbital period & distance from sun -beleived orbits must be perfect circles STILL |
|
BRAHE
|
observed a supernova (explosion of a distant star) -thought it was a nova (new star)
-proved it was farther away from the moon by measuring its parallax *Best set of naked-eye observations ever made -couldn't detect steller parallax --> concluded earth was stationary w/ sun orbiting it while other planets orbit the sun |
|
KEPLER
|
-hired by brahe
-ABONDONED IDEA OF CIRCULAR ORBITS -orbits are Ellipses -3 laws of planetary motion |
|
Keplers 1st
law of planetary motion |
the orbit of each planet is an ellipse with the sun at one focus
{tells us planet's distance from sun varies during orbit --closest @ perihelion --farthest @ aphelion} |
|
Keplers 2nd
law of planetary motion |
as a planet moves around orbit it sweeps out equal areas in equal times
{planets travel faster when they're closer to the sun -moves the greater distance @ perihelion & shorter distance @ aphelion in same amt of time} |
|
Kepler's 3rd
law of planetary motion |
more distant planets orbit the sun at slower speeds
obeying mathematical relationship p^2 = a^3 (p = planet's orbital period, a = avg distance in astronomical units) --suggested planetary motiomn might be the result of a force from the sun |
|
GALILEO
|
answered the 3 objections to a sun based model:::
-demonstrated moving objects remain in motion unless a force acts upon it [birds & such should stay w/ moving earth, not be left behind] -built a telscope - saw sunspots w/imperfections [heavens aren't perfect] -provided strong evidence that stars were far enough away to be unable to detect steller parallax |
|
Ancient Aristotle
model of the universe |
-all spheres responsible for celestial motion transparent & interconnected
-earth @ center explained by gravity -gravity pulled heavy things toward center of universe & allowed lighter things to float to heavens |
|
Astrology
|
the apparent positions of the sun moon and planets among the stars influence human events
-predictions far less reliable than astronomical ones -we know now that patterns of the stars in constellations are accidents -and constellations are only the apparent associations of the stars |
|
sidereal day
|
how long it takes for a star to go from its highest point one day to its highest point the next
(23 hrs 56 min) represents 360* rotation of earth |
|
solar day
|
our 24 hour day
-the time it takes the sun to make one circuit around the local sky (from its highest point one day to its highest point the next) *4 min longer than the sidereal *represent ~361* rotation of earth (makes the 4 min) |
|
synodic month
|
month comes from the moon's 29.5 day cycle
-the time required for each cycle of phases -not moon's true orbital period |
|
sidereal month
|
moon's true orbital period
-only ~ 27.33 days (how long it takes moon to complete orbit relative to position of distant stars) |
|
sidereal year
|
time it takes for earth to complete one orbit relative to stars
|
|
tropical year
|
20 min shorter than sidereal year
-in sync w/seasons -time from spring equinox to spring equinox (bc each year location of equinoxes and solstices shifts amoung the stars ~ 20 min worth) |
|
a planet's
"sidereal period" |
time planet takes to orbit sun
measured relative to stars |
|
planet's
"synodic period" |
time between when it's lined up with Sun one time and the next time its similar in alignment
|
|
conjunction
|
when planet is opposite the sun of earth
(planets closer to sun can experience this as "superior conjunction) |
|
opposition
|
when earth is between the sun and the planet
(planets closer to sun can experience this as "inferior conjunction"---they never have an opposition) |
|
apparent solar time
|
base time of sun's actual position in local sky (sundials)
-noon = precise moment when sun's highest in sky |
|
Newton's first law of Motion
|
objects in motion stay in motion
objects in rest stay at rest -unless acted upon by an outside force |
|
Newton's 2nd law
|
Force = (mass)(accelleration)
|
|
Newton's 3rd law
|
for every action there's an equal and opposite reaction
|
|
Newton
basics |
-explained why planets move
-developed model that gravity is keeping planets in their orbits -mathematically proved kepler's 3 laws -can now determine mass of objects, their orbits, how much force they exert on eachother -earth has an equatorial bulge (from moon pulling) -discovery of planet neptune -applications of calculus |
|
EINSTEIN
|
relativity
1905 & 1915 (special & general relativity theories) |
|
2 observations for relativity
|
1)your description of reality is the same regardless of the constant velocity you're moving
2)speed of light is constant and nothing is faster |
|
3 results of special relativity
|
1) length of object decreases as speed increases
2)clocks passing by you move more slowly than clocks at rest {time dilation} ---time and space cannot be seperated & equal the single entity of "spacetime" 3)mass of an object increases as it moves faster E = mc^2 |
|
newton was wrong!
|
newton's physics of gravity can describe small objects but don't work when applied to massive bodies or really fast speed
|
|
einstein says objects warp the space around them
|
gravity doesn't attract objects the curvature of space draws them together
|
|
even things without mass would be attracted toward a massive body
(says einstein) |
like light
-black holes |
|
Types of Energy
|
-Kinetic (energy of motion)
-Potential (stored) -----a)gravitational -----b)chemical -----c)electrical -thermal (heat) -radiative (light) -mass-energy (e = mc^2) |
|
mass-energy?
|
E = mc^2
|
|
laws of energy
|
1)can't be created or destroyed
2)can be converted from one form to another |
|
"phase changes"
|
occur when thermal (heat) energy is added to matter
-increasing thermal energy causes bonds to break -decreasing thermal energy produces stronger bonds |
|
plasma phase
|
extreme heat
-free electrons move amoung + ions -molecular dissasociation |
|
gas phase
|
atoms / molecules essentially unconstrained
|
|
liquid phase
|
atoms / molecules remain together but move freely
|
|
solid phase
|
atoms / molecules held tightly in place
|
|
electromagnetic radiation
|
aka LIGHT
|
|
speed of light?
|
300,000 km /sec
|
|
light properties?
|
both a Partical
and a Wave |
|
light's wave-like properties
|
-shadow edges aren't crisp
-different colors of light have different wavelengths |
|
light's partical-like properties
|
-can knock electrons of a surface
(photoelectric effect) ----film |
|
visual light
(optical spectrum) |
-blue = shorter wavelengths
-red = longer wavelengths -white light = all the colors -water & ice act as prisms seperating colors |
|
UV rays
|
waves short of our detection
(shorter than blue) |
|
IR (infrared) rays
|
waves long of our detection
(longer than red) |
|
Telescope types:
|
1)refractor
2)reflector |
|
refractor telescope
|
uses lenses to produce image
-good for close bright objects (planets, moon) DRAWBACKS: -lense causes distortion -different light wavelengths focus on different points -size limitations |
|
reflector telescope
|
uses mirrors to produce images
-better for distant dim fuzzy objects DRAWBACKS: -blocked light from secondary mirror -light focuses on different distances |
|
purposes of telescope
|
brighten
resolve (sharpness) magnify |
|
problems observing atmosphere from earth
|
atmosphere of dust/gas/h2o/ice causes stars to twinkle
-spherical atmosphere causes distortion of shape/position/color -light pollution |
|
hubble space telescope
|
-orbiting earth since 1993
-gathers UV, IR, & visible light (clear images of planets) |
|
Charge Coupled Devices
(CCDs) |
photographic film for astronomers
-silicon square divided into light sensitive cells (pixels) -viewed/processed on computers |
|
radio astronomy
(radio telescopes) |
telescopes can look @ radiowaves
-radio dishes can be combined to form better image -useful in detecting features like black holes |
|
metonic cycle
|
by ancient greek astronomer
-19 year cycle --bc takes 19 years for the lunar phases to repeat on the same dates |
|
18-year saros cycle
|
babylonians
--predicted eclipses |
|
sacred round
|
mayan cycle
260 days -eclipse prediction |
|
first proposed sun-centered modeL?
|
aristarchus
(greek) |
|
how did greeks explain "apparent retrograde motion"
for their geocentric modeL? |
"Ptolemaic Model"
-each planet moves around earth on a small circle that turns around a larger circle |
|
celestial coordinates
|
coordinates are
DECLINATION: [similar to latitude] -parallal to celestial equator -celestial equator = 0* -labeled POSITIVE or NEGATIVE (not N/S) RIGHT ASCENSION [similar to longitude] -0 = line that runs thru spring equinox (same as longitude) -measures in HOURS (not E/W) ---full circle = 24 hrs ----each hr represents 15* |
|
stars w/
declination of: 0* >0* <0* |
0*: lie on celestial equator
-rise due east - set due west >0*: rise N of due east -set N of due west <0*:rise S of due east -set S of due west |
|
flyby
mission |
spacecraft goes past planet & continues
|
|
orbiter
mission |
orbits planet its studying
-longer term study |
|
lander / probe
mission |
lands on surface
or probes atmosphere |
|
return
mission |
designed to return a sample
|
|
speed
|
how far it'll go in a certain amt of time
|
|
velocity
|
tell us speed AND direction
|
|
acceleration
|
if its velocity is changing
-a change in speed or direction or both |
|
you don't feel any effect of moving when
|
YOUR VELOCITY IS CONSTANT
|
|
acceleration of gravity
(g) |
earth: increases by 10 m/s
|
|
momentum
|
(mass)(velocity)
|
|
how do u change an object's momentum?
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only by applying a FORCE
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freefall
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falling without any resistence
-whenever there's nothing to prevent you from falling -astronauts weightless when orbiting earth bc in constant state of free fall (there is gravity in space) |
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newton's third law
clarified |
for every force there's an equal and opposite force
-much greater acceleration for you than earth (bc you're so much smaller) |
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white light
v black light |
white :
all colors mixed in equal proportion black light absence of color |
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how light & matter interact
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1)EMMISION
-emits light (turn on bulb) 2)ABSORBTION -hand near a light -- hand absorbs light -- energy warms hand 3)TRANSMISSION -glass / air - allow light to pass thru 4)REFLECTION / SCATTERING -light bounces off matter -reflection = bouncing in same direction -scattering = random bouncing |
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wavelength
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distance from one peak to the next
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frequency
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number of peaks passing by a pt each second
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frequency can also be reffered as
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cycles per second
HERTZ (Hz) |
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speed of wave?
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(wavelength)(frequency) = speed
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"field"
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strength of force any particle would exerience @ a pt in space
-earth's gravitational field depends on earth's mass and the distance pt is from earth |
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light's "field"
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light waves are vibrate electric AND magnetic fields
-vibrations of electric field - electron goes up and down |
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wavelength & frequency related
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longer the wavelength
the lower the frequency |
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photons
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light's individual particles
-can be counted individually -each have a wavelength & frequency -shorter the wavelength, the higher the frequency == THE HIGHER THE ENERGY OF ITS PHOTONS |
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electromagnetic spectrum
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the complete spectrum of light
visible = 400-700nm -shortest gamma --- xrays --- UV --- visible --- IR --- (microwaves) --- radiowaves -longest(smallest amt of energy) |
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matter is composed of
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atoms
-different types = different elements |
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atomic #
v atomic mass |
atomic number = # of protons in nucleus
atomic mass = protons + neutrons (can vary -- isotopes) |
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molecules
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atoms combine to form molecules
(O2 molecule = two O atoms) -molecules w 2+ types of atoms = compounds (H2O) |
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phase changes occur..
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when one chemical bond is broken & replaced by another
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sublimation
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the process that molecules escape from a solid
(some gas always present with solid ice / liquid water) |
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evaporation
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process by which molecucles escape from a liquid
[high temps = higher sublimation & evaporation] |
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molecular dissociation
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at high enough temps collisions between molecules so violent they break chemical bonds holding individual h2o molecules together
molecules split into peices |
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ionization
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@ temps HIGHER than molecular dissociation
collisions break bonds holding electrons around nuclei of an atom allowing electron to go free -leaves remaining atom w + charge (the process of stripping electrons from atoms) |
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plasma
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hot gas in which atoms have been ionized
(can be reffered to as gas or plasma... ex. the SUN!) at temps HIGHER? than ionization whats left becomes a hot gas of freely moving electrons & + charged ions of H &O |
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pressure
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force / unit area
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pressure's effect on state changes
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higher pressure = needs higher temps to change state
(stay solid longer... & such |
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what particles can interact w light?
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ONLY CHARGED PARTICLES
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how can atoms contain energy?\
(3) |
1) bc of their mass they posses mass-energy (mc^2)
2)kinetic energy bc of their motion 3)electrical potential energy --MOST IMPORTANT -depends on the arrangement of electrons around nuclei |
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energy stored by electrons in atoms
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-electrons can have only particular amts of energy & not energy in between!!!
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"energy levels" of an atom
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the possible energies of electrons
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lowest possible energy level for electron?
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"GROUND STATE"
level 1 |
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"excited state"
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all possible energy levels other than ground state
(though they will quickly "calm" & return to ground state) |
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"energy level transitions"
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only occur when electron gains or loses specif amt of energy seperating 2 levels
(any other amt and nothing will happen) -the electron can gain enough energy to reach ionization level and will then escape the atom completely (ionizing the atom) *energy levels differ from element to element* |
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spectroscopy
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process of obtaining a spectrum and reading info
(look like rainbows) |
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"intensity" (light)
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the amount of radiation
-proportional to (number of photons @ that wavelength)x(energy of those photons) -lot of light = high intensity |
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"continuous spectrum"
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-common bulb
=spans a broad range of wavelengths w/o interruption |
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"emission line spectrum"
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low density cloud
-emits light only @ specific wavelengths -spectrum consists of bright emission lines against black background |
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"absorbtion line spectrum"
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cloud between us and bulb
-cloud absorbs specific wavelengths but we still see most of the continuous light of bulb --spectrum = dark absorption lines against background rainbow |
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when electrons go back to ground state...
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they emid a photon of light (when they release that energy)
-the photon released has the same energy the electron lost === specific Wavelength & frequency |
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"chemical fingerprints"
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hydrogen emits and absorbs light at specific WL's = can detect its presence in distant objects (only H produces a certain set of lines)
-molecules can vibrate and rotate and also produce spec. spectra (molecular bands) |
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thermal radiation
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the temperature dependence of light
-photon energies depend only on objects temp (not what obj made of) |
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hotter object emit photons....
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hotter = emits more light
hotter = emits photons w higher energy (shorter wavelengths) -first turning on light glows red ... hotter gets blue -cool star = red light -hotter stars = blueish |
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doppler effect
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moving toward you - higher pitch
-each pulse a lil closer -waves get bunched --gives them shorter WL --higher frequency moving away from you - lower pitch -each pulse from farther away -stretches out WLs ---giving them lower frequency |
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doppler effect applied to light
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-moving toward us
-light waves bunch -shorter WLs "BLUESHIFT" -moving away -longer WLs "REDSHIFT" |
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"rest wavelengths" applied to light
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the wavelengths of hydrogen lines in stationary clouds
-if lines appear longer = REDSHIFT -lines seem shorter = BLUESHIFT (can also tell if rotating) |
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how lens' work
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light hits lens
-slows down -causes light to bend (farther from center = bent more) -converge to pt - FOCUS -forms image of original obj -image appears on "focal plane" |
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CCDs
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"charge coupled devices"
-chip of silicon VERY sensitive to photons -divided into grid (pixels) -when photon strikes pixel == electric charge accumulates -more sensitive to light than normal film -accurately records 90% of photons that strike them -can records BOTH DIM & BRIGHT light @ same time |
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telescope's "light collecting area"
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how much total light telescope can collect at a time
-by diameter of lca |
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telescope's angular resolution
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smallest angle over which we can tell 2 dots are distinct
-depends on their actual seperation & their distance from us -larger = higher angular resolution -earth's atmosphere limits angular resolution |
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telescope's "diffraction limit"
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the angular resolution a telescope could acheive if it were limited only by light wave interference
-depends on diameter of telescops mirror & WL being observed -larger telescops = smaller diffraction limit |
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spectrographs
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use diffraction grating to seperate various colors of light into spectra -- then recorded w CCD
-can reveal chemical comp, temp, & rotation rate from spectrum BUT depends on SPECTRAL RESOLUTION (higher = more detail) --depends on how much spectrograph spreads out light...spreads out light too much = dim |
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"light curves"
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graphs that show how objects intensity varies w time
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arctic circle
v antarctic circle |
arctic = N
antarctic = S |
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difference between
"special" & general relativity |
special - shows that space and time are intertwined - IGNORES gravity
general - offers new view of gravity --explains expansion of universe & black holes -applies WITH OR WITHOUT gravity |
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theory of relativity leads to....
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-no info can travel faster than speed of light
-moving faster = time moves slower -moving faster = length is shorter -faster = mass is greater (E = mc^2) |
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2 absolutes of relativity
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-motion is relative NOT everything
1)laws of nature same for everyone 2)speed of light same for everyone |