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82 Cards in this Set

  • Front
  • Back
how far is a lightyear?
6 trillion miles (6 & 12 0's)
size and shape of milky way galaxy?
barred spiral galaxy
disk (height, basically) is 2,000 Ly
200,000Ly diameter (100,000Ly radius)
how many stars in milky way?
400 billion (4 & 9 0's)
how many galaxies in universe?
"many" - 100s of millions
distance from the milky way to the nearest galaxy? name of that galaxy?
2million Ly
andromeda
most distant galaxies observed are how far away?
13billion Ly
what keeps clusters of galaxies together?
mass/dark mass at the center creates a gravitational pull (visible matter alone is not enough to create this pull, so scientists believe there must be more we cannot see - dark matter)
dark matter
- two components
- how do we know?
dark mass: exerts a gravitational pull
dark energy: exerts a repulsive force that causes expansion of universe

summing the known matter of the universe does not come to the mass of the entire universe. also, galaxies stick together because of dark matter
the observable universe
- limits
- why?
13.7billion Ly
13.7billion years ago, the big bang occurred. this is the beginning of the universe. immediately after the big bang, the universe was so densely packed that it created a veil of material that obscures our view of the big bang itself.
the age of the universe
14billion Ly (13.7billion, to be precise)
origin of the universe
big bang
evidence for the big bang (3)
1. expansion of universe
2. primordial fireball/primordial nucleosynthesis
3. cosmic background radiation
doppler shift of light
- general
- as big bang evidence
- distant galaxies
if galaxy is moving towards you --> wavelength of light is lower --> appears as blue light

if galaxy is moving away from you --> light waves are stretched, longer --> appear as red light

---
sleifer: almost all visible galaxies show red shifts ---> evidence of expanding universe

---
the more distant the galaxy, the faster it moves (the larger its red shift) [observation by hubble]
how are distances to galaxies measured?
measure the absolute brightness of stars in that galaxy
standard candle technique: compare brightness to other stars/galaxies whose distance is known. brighter: closer; dimmer: farther out.
hubble's law
- describe
- graph
there is a linear relationship between a galaxy's distance and that galaxy's velocity
- i.e., the more distant a galaxy, the faster it is moving away from us

---
x-axis: distance (Ly)
y-axis: velocity (km/sec)
straight line
cosmic background radiation
the universe's continuing expansion results in cooling temperatures, radiation cools down (from visible light to microwaves) to temperature of 2.7 (or 3) degrees K
primordial fireball
universe "born" at temperature about 10billion degrees --> protons and neutrons form to create hydrogen nuclei --> as it cools, hydrogen nuclei fuse to form helium nuclei (formation of helium nuclei = primordial nucleosynthesis)
penzias and wilson
their microwave telescopes picked up a constant radiation at 3 degrees K, proving cosmic background radiation
is earth at the center of the expanding universe?
no, there is no center
think of the raisin bread analogy
dark energy and the expanding universe
dark energy exerts a repulsive force that causes the universe to accelerate and expand
creation of primordial hydrogen and helium
1. protons, neutrons, electrons fuse together in primordial fireball to create hydrogen
2. as cooling occurs, hydrogen atoms fuse together to form helium atoms (6% of atoms He, 94% remain H)
3. but the universe cooled enough, expanded enough after that short period of time (8.5minutes) so that no other fusion could occur (too cool, atoms too far apart to collide). all other naturally occurring elements formed during supernovas
define: galaxy
clusters of billions of stars
define: star
body of hot gasses (H, He), that form a cloud of atoms with gravitational pull

as atoms within collide, heat rises, energy emitted as light energy --> stars shine
define: solar system
a sun (star) with celestial bodies (of gas, rock, and water) that orbit around it, drawn in by its gravitational pull
define: planet
a celestial body in orbit around the sun
how many elements are there in the universe?
92 naturally occurring
118 total
formation of stars: gravitational contraction of gas clouds
1. denser regions of universe draw matter inward by force of gravity, forming nebulae (clouds of H, He)
2. atoms in nebulae accelerate inward under the force of gravity, collide rapidly emitting extreme heat
3. collisions cause fusion, collapsing portion of nebula becomes a star
stellar birthplaces
orion nebula within orion's belt
pillar structures near orion's belt caused by star explosion --> increased pressure and density --> particles pulled together towards common centers (pillars caused by varying densities of the matter)
nine planets & distances from sun
mercury: .39AU
venus: .72AU
earth: 1AU
mars: 1.52AU
jupiter: 5.2AU
saturn: 9.54AU
uranus: 19.18AU
neptune: 30.06AU
pluto: 39.53AU
how old is the solar system?
4.65billion years old
origin of solar system from disk
- evidence given by planets' properties
higher temperature gases move faster than lower temp gases.

because mercury was closer to sun (than say, jupiter), its gases moved faster, more likely to fly off from the accretion disk around sun into space. as gases escape, planet loses mass; as planet loses mass, gases escape more easily. almost all gas escapes, leave behind spheres of metal and rocks. also, solar winds blow a lot of the gases off (terrestrial planets)

planets farther from sun initially cool enough to retain their gaseousness, and captured the gases that escaped from terrestrial planets. relatively small, rocky or metal cores; swirling liquid, gaseous atmospheres (jovian planets)
nuclear fusion in stars
if protons move fast enough to overcome the electromagnetic repulsion they have for one another, they are subject to nuclear force (which only works at very close distances) and fuse together to form He.
during this, a little bit of mass is converted to energy, in the form of light and heat --> STAR!
why are planets different sizes, different compositions?
distance from sun affects amount of gas lost, climate (exposure to solar radiation)
evidence from meteorites to the age and origin of planets
space debris crashing into planets --> craters
measure crater density to learn about a planet's history (weathering/erosion/lack thereof)
composition of moons of giant planets
many have earth-like atmospheres/compositions (jupiter's europa, saturn's titan)
meteorites
- composition
- age
most are "stony meteorites", 90% silicate rock, 10% iron/nickel
- similar to core:mantle ratio in earth --> meteorites as primordial composition of solar system,
mars: size
1. relative to earth
2. relative to moon

3. distance from sun
radius: =.053 radius of earth (about half the size of earth)
about twice the size of the moon

150km (1.52AU)
mars: evidence of volcanoes
calderas (central craters on volcanoes - volcanoes, which are enormous) on surface
lava flows cover the plains of mars
parallel cracks split martian crust, rising mantle plume stretches crust (blob tectonics vs plate tectonics like earth)
mars: when did vulcanism die out?
calderas shut down 500m - 1bill years ago , however some volcanoes have only a few meteorite craters (suggesting that recent lava flows - a few million years ago - "cleaned" everything)
mars: why did vulcanism die out?
outgassing eventually ended (outgassing on earth too, but earth is bigger so it can go on for longer)
as outgassing slows/stops, pressure drops
mars: atmosphere
surface conditions
thin co2 atmosphere (low atmospheric pressure), frigid, dry; water ice in caps, soil

--
rocky, evidence of water, craters, volcanoes
evidence for past liquid water on mars (9)
canyons, erosion, extinct stream/lakebeds, alluvial fans, precipitated salts, polar icecaps, frozen soil

winding valleys
branching channels
composition of martian ice caps
part h2o ice
part co2 ice
prospects for life on mars (currently, historically)
- why would the discovery of life on mars be important?
potentially a "golden age" for mars, when climate was temperate enough for life to evolve

at the present moment, it is too cold and too dry for life on mars

emergence of living organisms in our solar system would suggest that life is relatively common (other solar systems/galaxies could have life/intelligent life)
venus
size relative to earth

distance from sun
.95 radius of earth
closely resembles earth in size, density, and distance from sun

108 km (0.73AU)
venus: surface conditions
- temperature
- pressure
- atmospheric composition
because of greenhouse effect, hotter than surface of mercury (hot enough to destroy complex organic molecules necessary for life)

atmospheric pressure: 90x denser than earth (= to pressure at 1000m beneath the sea)

composition: 97% co2, small amounts of other gases; sulfuric acid cloud layer obscures surface from our view
venus: geologic activity
lots of volcanic activity --> few meteorite craters on surface

catastrophic series of eruptions 300-500m years ago --> volcanic mountains, covering surface with basalt flows
little activity after that. interior has cooled?

volcanic activity caused by blob tectonics: rising and sinking of mantle and crust causes eruptions (rather than at plate boundaries) - surface temperatures high --> surface rocks more plastic than earth
venus: greenhouse effect
higher surface temperatures of venus (proximity to sun) --> water never condensed + no oceans for co2 to dissolve into = lots of h2o and co2 in atmosphere. both of these emit radiation (absorbed infrared from sun) and heat up surface.
venus: carbon cycle
volcanic eruptions emit co2
nothing to absorb co2 (like plants on earth do) so it stays in the atmosphere
causes greenhouse gas effect, rock weathering
venus: rock weathering
rocks on surface react with co2, h2o, (both come out of volcanoes) carbonic acid --> weathering of rocks

h2o runs along rocks, to ocean: calcium carbonate > sediment > limestone
habitable zone around the sun
- what controls the boundaries?
- what planets are in the habitable zone?
1. planets distance from sun, planets size

2. mars and earth are both in the habitable zone (.95AU - 1.50AU)
main source of energy for sun?
hydrogen burning/fusing
red giant stars
at He builds up in star, it's like having ash in your fireplace. nuclear fusion slows down, star begins to collapse, atoms inside collide and cause release of energy as heat

to 100m degrees celsius, at which point carbon fusion occurs and the star becomes a red giant
accretion disks and the formation of stars
rotation of stars/matter in a cloud increases as cloud gets smaller (like an ice skater) the centrifugal force pushes the cloud outward into a pizza shape - accretion disk of gas and dust circle around stars
origin of the earth - accretion
centrifugal force around clouds causes gas and clouds in accretion discs to combine --> planetesimals
planetesimals combine with one another --> planets
8 most abundant elements on earth
- how much of earths' crust do these 8 make up?
1. hydrogen
2. silicon
3. aluminum
4. iron
5. calcium
6. sodium
7. potassium
8. magnesium

98.5% of total mass of earth's crust
how old is the earth?
4.6 billion years old
rock cycle
1. sedimentary, igneous rock subject to heat and pressure melt to form magma (or, magma comes up from earth's mantle)
2. magma cools --> igneous rock
3. rock is weathered --> sediment
4. sediment accumulates --> sedimentary rock
5. sedimentary rock is subject to heat and pressure --> metamorphic rock --> magma
6. metamorphic rock then either melts (heat & pressure) or is eroded --> sediment --> sedimentary rock
how is the earth heated?
1. bombardment heat (from bombardment of meteorites)/accretion (as meteorites hit the earth)
2. radioactive decay
when did the moon die?
3.8 billion years ago, bombardment ended and the moon was no longer volcanic
why is the study of the moon's geology so important?
because the earth is still geologically active, we cannot study its distant past (everything has been changed since). however, because the moon is smaller, geologic activity ended 3.8billion years ago, so we have a older "snapshot" of planetary growth
how was the moon formed?
- evidence?
- when?
collision between proto-earth and a mars-sized body; material flew off, accreted, and became the moon.

evidence: mostly iron, as contained in earth's core - the lighter elements vaporized/flew off in the collision

this happened 4.6bil years ago
formation of core, mantle and crust
completed by 4.0bil years ago

because the core contains the densest elements (iron, nickel, silicon), and the crust contains the least dense elements (rock - SiO2 (sulfite), MG, Al, Ca)
basalt v. granite: where?
basalt is in the oceanic crust, is darker and denser

granite is in continental crust, is lighter and less dense
how old are the oldest rocks on earth?
4.28billion years old
why are ancient rocks so rare on the earth?
because the earth is still geologically active, rocks are subject to the rock cycle and so they erode or melt
seismic waves
body waves: p and s waves
p: compressional (waves move parallel to wave direction); faster than s waves; through air, liquid, and solids
s: shear waves (waves move perpendicular to wave direction); moves slower than p wave; moves only through solids (atoms in a gas/liquid not densely packed enough to shear against one another)

surface waves:travel from epicenter (point directly above focus - origin of earthquake) across earth's surface in up-and-down or rolling motion; slower than body waves
reasons for initial rejection of continental drift?
alfred wegener had no hypothesis for the mechanisms of c.d., he only had observations that supported that it had happened
alfred wegener and continental drift theory (his three observations of evidence)
he pursued the observation that continents fit together (not the first to observe this), also found other evidence: fossil distribution (plants and animals), rock distributions
in general, what makes a planet habitable? (this is the same question as, what determines the boundaries of the habitable zone)
planet's size, and distance from the sun
evidence for plate tectonics/continental drift (9, including wegener's 3)
- fit of continents
- distribution of rocks
- distribution of plant/animal fossils
- distributions of earthquakes
- distribution of volcanoes
- mid-oceanic ridge; central rift on ocean floor
- age of ocean-bottom rocks (younger closer to ridge)
- magnetic stripes on ocean floor (magnetism direction/intensity reflects that of the earth at the time of rock formation
lunar maria
- what kind of rock?
- age?
maria means sea, but these are actually lava flows from the interior of moon (prior to its geological death)

mainly basalt flows

3.8 to 3.0 billion years old (until moon became geologically inactive)
lunar highlands
- features?
- age?
original crust of moon
heavily cratered
igneous rocks (about 4.4bil years old)
craters on the moon
caused by meteorite impacts

rock of maria and highlands welded together by lava --> proof that moon used to be liquid
causes of the melting of the moon? (2)
gravitational coalescence (accretion caused melting to a few hundred km)
meteorite bombardment

not radioactive decay, because igneous rocks formed before radioactive decay could have caused enough melting
how does a planet heat up?
heat of formation buried inside planets during birth process

additional heat by radioactive decay (of unstable elements)
size of moon relative to earth
surface area of moon = surface area of africa

1/4 the diameter of earth
radiometric dating
- parent/daughter isotopes
- k-ar dating
technique used to date materials based on comparison between observed abundance of a radioactive isotope and its decay products

as radioactive isotopes (parent) decay into daughter isotopes, amount of daughter isotope increases while amount of parent isotope decreases. relative proportions are used to derive the age of the sample.

k-ar is one radiometric dating technique, which measures the decay of potassium parent isotopes into argon daughter isotopes. because potassium has an extremely long half-life, this method is used for dating the oldest rocks
galilean moons of jupiter
in order of closeness to jupiter:
io: volcanically active, smooth surface (because of constant lava flows)
europa: rocky interior; surface covered in vast ice crust (liquid water beneath?)
ganymede: convecting metallic core; water/ice crust; plate tectonic activity
callisto: heavily cratered, possible subterranean ocean
other moons of giant planets
titan (saturn): atmosphere (nitrogen, methane); earth like landscape; methane exists in liquid/gas/solid form; reacts with other materials to form organic molecules

moons of uranus and neptune may be collision debris
asteroids
may change orbits frequently and erratically

composition can be solid rock, or compressed mass of rock/rubble
comets
originate in outer reaches of solar system

composed mostly of water-ice mixed with frozen crystals of methane, ammonia, carbon dioxide. concentrations of silicate rock and metal particles mixed with lighter ices