Astronomy Test One

Front 1

Rules of thermal radiation

Back 1

1. Hotter objects emit more total radiation per unit surface area. funkyothingT^4=E
F.O.: constant
T: temp (K)
E: light energy emitted per unit area (brightness)
2. Hotter objects emit bluer photons (w/ higher average energy)
peak wavelength=2.9x10^6/T(K) nm

Front 2

Kirchhoff's Laws

Back 2

1. hot, dense glowing object (solid or gas) emits <u>continuous spectrum</u>.
2. Hot, low density gas emits light of only certain wavelength: emission line spectrum.
3. When light having continuous spectrum passes thru cool gas, absorption line spectrum.

Front 3

lunar eclipse

Back 3

Moon passes thru Earth's shadow, can only occur at full moon

Front 4

solar eclipse

Back 4

occurs when moon's shadow falls on Earth and therefore can only occur at new moon

Front 5

umbra

Back 5

central region of shadow where sunlight is completely blocked

Front 6

penumbra

Back 6

surrounding region of shadow where sunlight is only partially blocked

Front 7

eclipse can occur when:

Back 7

Nodes are nearly aligned with Sun and Earth
the phase of Moon is new or ful

Front 8

Precession is caused by

Back 8

gravitational tugs from sun and moon that try to straighten out its rotational axis

Front 9

total lunar eclipse

Back 9

moon passes entirely through umbra
sun, earth, and moon nearly perfectly aligned

Front 10

partial lunar eclipse

Back 10

part of the moon passes through umbra
alignment somewhat less perfect

Front 11

penumbral lunar eclipse

Back 11

moon passes through penumbra

Front 12

total solar eclipse

Back 12

Moon is relatively close to Earth in its orbit; umbra touches a small area of Earth's surface. anyone within this area will see a total solar eclipse.

Front 13

lunar eclipse

Back 13

Moon passes thru Earth's shadow, can only occur at full moon

Front 14

solar eclipse

Back 14

occurs when moon's shadow falls on Earth and therefore can only occur at new moon

Front 15

umbra

Back 15

central region of shadow where sunlight is completely blocked

Front 16

penumbra

Back 16

surrounding region of shadow where sunlight is only partially blocked

Front 17

eclipse can occur when:

Back 17

Nodes are nearly aligned with Sun and Earth
the phase of Moon is new or ful

Front 18

Precession is caused by

Back 18

gravitational tugs from sun and moon that try to straighten out its rotational axis

Front 19

total lunar eclipse

Back 19

moon passes entirely through umbra
sun, earth, and moon nearly perfectly aligned

Front 20

partial lunar eclipse

Back 20

part of the moon passes through umbra
alignment somewhat less perfect

Front 21

penumbral lunar eclipse

Back 21

moon passes through penumbra

Front 22

total solar eclipse

Back 22

Moon is relatively close to Earth in its orbit; umbra touches a small area of Earth's surface. anyone within this area will see a total solar eclipse.

Front 23

partial solar eclipse

Back 23

occurs in lighter area surrounding area of totality that falls within moon's penumbral shadow. only part of sun is blocked from view.

Front 24

annular eclipse

Back 24

Moon is relatively far from Earth, in region behind umbra you will see annular eclipse. sunlight surrounds disk of moon. (anyone in surrounding penumbral shadow will see partial solar eclipse).

Front 25

eclipse seasons

Back 25

two periods each year when nodes of Moon's orbit are nearly aligned with Sun

Front 26

saros cycle

Back 26

eclipses occur in roughly 18 year cycles

Front 27

how does night sky change throughout the year?

Back 27

the visible constellations at a particular time of night depend on where earth is located in its orbit around the sun

Front 28

why do we see phases of moon?

Back 28

at any time, half the moon is illuminated by the sun and half is in darkness. the face of the moon that we see is some combination of these two portions, determined by the relative locations of the sun, earth, and moon.

Front 29

what conditions are necessary for an eclipse?

Back 29

an eclipse can occur only when nodes of moon's orbit are nearly aligned with sun and earth. when this condition is met, we can get a solar eclipse at new moon and a lunar eclipse at full moon.

Front 30

retrograde motion?

Back 30

occurs over a few weeks to a few months as earth passes planet in its orbit. greeks rejected this explanation because they couldn't detect stellar parallax because they didn't believe stars were that far away.

Front 31

Ptolemy

Back 31

made a model of geometric universe with accurate predictions of planetary positions

Front 32

copernicus

Back 32

created sun-centered model of solar system designed to replace ptolemaic model, but it was no more accurate because he still used perfect circles.

Front 33

tycho

Back 33

provided observations used by kepler to refine the model by introducing elliptical orbit
saw supernova and comet--cosmos not perfect

Front 34

galileo

Back 34

experiments and telescopic observations (telescope saw stars were far away, observed moons orbiting jupiter, saw venus going through phases in a way that proved it must orbit sun and not earth, proved heavens were not perfect) overcame objections of earth orbiting sun.

Front 35

kepler's laws

Back 35

1. orbit of each planet is an ellipse with the sun at one focus 2. as a planet moves around its orbit, it sweeps out equl areas in equal times. 3. more distant planets orbit the sun at slower average speeds, following a precise mathematical relationship p^2=a^3. p is planet's orbital period in yrs and a is avg dist from sun in AU

Front 36

hallmarks of science

Back 36

1. seeks explanations for observed phenomena that rely solely on natural causes. 2. progresses thru creation and testing of models of nature that explain the observations as simply as possible. 3. scientific model must make testable predictions about natural phenomena that would force us to revise or abandon model if the predictions do not agree w/ observations.

Front 37

scientific method

Back 37

observations -> question -> hypothesis -> prediction -> test. if test supports hyp, made additional predictions and test, if it doesn't, revise or abandon hypothesis

Front 38

kinetic energy

Back 38

ke=1/2mv^2
energy of motion

Front 39

potential energy

Back 39

energy being stored for possible later conversion into kinetic energy. gasoline has chemical p.e. which a car engine converts to k.e. of moving car, etc.

Front 40

radiative energy

Back 40

energy carried by light

Front 41

temperature

Back 41

avg k.e. of particles. higher temp, particles are moving faster

Front 42

thermal energy

Back 42

energy contained within a substance as measured by its temperature. collective k.e. of the many individual particles moving within a substance. depends on both the temperature and the total number of particles. astronauts get cold in space despite high temp b/c of low density of space--few particles are available to transfer thermal energy to them.

Front 43

law of conservation of energy

Back 43

energy cannot be created or destroyed
all actions in universe involve exchanges of energy or conversion of energy from one form to another
1/2mv^2-GMm/r < 0
motion is bound (circle, ellipse) because if r got too large the constant would no longer be negative
> 0
motion unbound (escapes!) b/c r can go to infinity
= 0
escape velocity v^2=2GM/r (doesn't depend on m!)

Front 44

atomic number

Back 44

number of protons in nucleus

Front 45

atomic mass number

Back 45

combined number of protons and neutrons

Front 46

isotopes

Back 46

versions of an element with different numbers of neutrons

Front 47

phases of matter

Back 47

1. solid: below 0 C, K.E. is low and molecule is bound tightly to neighbor.
2. liquid: temp increases, rigid arrangement vibrates, molecules break bonds to make loose bond.
3. gas: water molecule breaks free of all bonds (molecular dissociation) and moves independently of other molecules
4. plasma: hot gas, atoms ionized (electrons stripped, escaped)

Front 48

ground state

Back 48

electron is smeared out to minimum extent that nature allows, atom contains smallest possible amount of electrical potential energy

Front 49

excited state

Back 49

electron gains energy, becomes smeared out over a greater volume. become ionized if it gains enough energy and escapes.

Front 50

how is temperature different from heat?

Back 50

temperature is a measure of the avg k.e. of the many individual atoms or molecules in a substance. heat depends on both temp and density: at a particular temp, a denser substance contains more thermal energy

Front 51

what is gravitational potential energy?

Back 51

energy that can be released by an object falling under the force of gravity. the amt of an object's g.p.e. depends on its mass, the strength of gravity, and how fair it could fall. -GMm/r

Front 52

what is the difference between speed, velocity, and acceleration?

Back 52

speed is the rate at which an object is moving. velocity is speed in a certain direction. acceleration is a change in velocity, meaning a change in either speed or direction.

Front 53

how can you tell when a net force is acting on an object?

Back 53

a net force must be acting whenever the object's momentum is changing. momentum = mass x velocity

Front 54

newton's three laws of motion

Back 54

1. in the absence of a net force acting upon it, an object moves with constant velocity. 2. F=ma. 3. for any force, there is always an equal and opposite reaction force. momentum =mxv

Front 55

universal law of gravitation

Back 55

force of gravity is directly proportional to product of the objects' masses and declines with the square of distance btwn two centers. F=Gm1m2/d^2
measure of force of gravity upon you
f=GM(earth)m(you)/r(earth)^2

Front 56

bound orbits/unbound orbits

Back 56

ellipses, circles/parabolas=, hyperbolas>
newton's update of kepler's first law

Front 57

mass
mass potential energy

Back 57

amount of matter in object
energy is stored in matter itself. mass-energy is what would be released if an amount of mass, m, were converted into energy. e=mc^2

Front 58

weight

Back 58

a measurement of the force which acts upon an object. when you freefall, you are weightless.

Front 59

force

Back 59

anything that can cause a change in an object's movement

Front 60

(conservation of) angular momentum
torque

Back 60

momentum involved in spinning mxvxr
velocity increases when radius decreases
a torque is anything that can cause a change in an objects angular momentum (twisting force). depends on where you apply force.
in absence of net torque, the total angular momentum of a system remains constant
m1v1 + m2v2 = constant conservation of momentum
causes moon to more farther away from Earth. Moon gains angular momentum because earth is being retarded--moon going away from us.

Front 61

why are there two high tides on earch each day?

Back 61

the moon's gravity stretches earth along the earth-moon lineso that it bulges both toward and away from the moon

Front 62

why are tides on earth caused primarily by the moon rather than by the sun?

Back 62

earth's gravitational attraction to the sun is stronger, but tides are caused by the difference btwn th strength of the gravitational attraction across earth's diameter. This difference is greater for the gravitational force due to the moon because the moon is so much closer than the sun.

Front 63

why is earth's rotation gradually slowing down?

Back 63

tidal friction, caused by the way the tidal bulges exert drag on Earth, causes a gradual slowing of Earth's rotation. A related consequence of tidal friction is the Moon's increasing distance from Earth.

Front 64

Why does the Moon always show the same face to Earth?

Back 64

the moon's synchronous rotation is a result of tidal forces. The moon may once have rotated much faster, but tidal friction slowed its rotation until it became synchronous with its orbit, at which point tidal friction could not slow the orbit any further.

Front 65

spring tide

Back 65

when sun and moon pull in same direction (new and full phases), high tide is higher than usual

Front 66

neap tide

Back 66

when sun and moon pull at right angles (first and last quarter phases) high tide is lower than usual