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Milkyway contains ___ stars

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1

Milkyway contains ___ stars

100 billion

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2

Local Group

about 40 galaxies in galaxy cluster

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Superclusters

clusters of galaxy clusters

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1 AU

earth's average distance from sun

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5

Light Year

distance light can travel in one year (9.46 tril km)

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Observable Universe

14 billion light years

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Big Bang

happened 14 bill years ago, avg. distance between galaxies increasing over time

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Star Birth

gravity compresses material in cloud, center becomes hot/dense, undergoes nuclear fusion

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Supernovae

massive stars dying in huge explosions

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10

Elements in earliest universe

Hydrogen and Helium

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11

Earth's Rotation

Rotates daily around axis, from west to east

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12

Sun and Stars rise in the ___ , set in the ___

east, west

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13

Ecliptic plane

flat plane defined by Earths orbit

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14

Created sun centered solar system idea

Copernicus

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15

Zodiac

constellations across ecliptic

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Precession

gradual wobble that alters orientation of Earth's axis in space (every 26,000 years)

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Zenith

point directly overhead

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18

Meridian

half circle from north to south through the zenith

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19

Angular size of moon

.5 degrees

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Synchronous rotation

moon rotates on its axis the same amount of time it takes for it to orbit earth

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New Moon

occurs when moon is between the sun and earth

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22

Lunar Eclipse

moon must be full; earth lies between sun and moon

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Solar Eclipse

moon must be new; moon lies between sun and earth

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24

The altitude of celestial pole in sky is equal to

your latitude

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25

Reason for seasons

tilt of Earth's axis causes sunlight to fall differently on Earth at different times of year

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Lundar Phase

29.5 days

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Apparent Retrograde Motion

apparent motion of a planet moving westward through the zodiac

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Stellar Parallax

apparent shift in position of a nearby star based on position of orbit (doesn't happen if object is far away)

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29

Reason for Greeks rejecting explanation for planetary motion

they couldn't detect parallax

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30

Solar Calendar

what we use, synchronous with seasons

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31

Geocentric model

Greek; placed Earth at center of universe

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32

Ptolemaic Model

each planed moved around Earth on a small circle that turned about a larger one

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Plato

heavenly motion must be in perfect circles

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Kepler

discovered planetary orbits are ellipses

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Keplers 1st Law of Planetary Motion

orbit of each planet around the sun is an ellipse with the sun at one focus (planets distance from sun varies during orbit)

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Keplers 2nd Law of Planetary Motion

As a planet moves around its orbit, it sweeps out equal areas in equal times (planet travels faster nearer to the sun, slower further from sun)

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Keplers 3rd Law of Planetary Motion

more distant planets orbit the sun at slower avg. speeds p^2=a^3

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Tycho

observed first nova, saw it was further than moon

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Objections to Copernicus' view of sun centered system

objects would fall away if Earth was moving, noncircular orbits meant heavens weren't perfect, no one could detect parallax

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Aristotle

argued Earth centered universe

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41

Speed

how far object will go in certain amt. of time

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Velocity

speed and direction

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Acceleration

change in velocity

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Acceleration of Gravity (g)

acceleration of falling object, 9.8 m/s^2

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Momentum

mass x velocity

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Mass

amount of matter

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Weight

mass x force; no gravity = no weight

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Newton's 1st Law of Motion

an object moves at constant velocity if there is no net force acting upon it

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Newton's 2nd Law of Motion

force = rate of change in momentum

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F = M x A

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Newton's 3rd Law of Motion

for any force there is always an equal an opposite reaction force

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Conservation of Momentum

if there are no external forces, the total momentum of 2 interacting objects cannot change

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Conservation of Angular Momentum

if there is no external torque, the total momentum of interacting objects cannot change

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Angular momentum

mass x velocity x radius

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Conservation of Energy

energy cannot appear/disappear out of nowhere, can only lose/gain energy by exchanging

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Kinetic Energy

energy of motion, 1/2mv^2

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Radiative Energy

energy carried by light

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Potential energy

stored energy, gpe=m x g x h

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Joule

standard unit of energy

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Mass-Energy

E=MC^2

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e = Amt of potential energy c = speed of light m = mass

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Thermal energy

measures total kinetic energy of particles

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Temperature

measures the average kinetic energy of particles in object

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Universal Law of Gravitation

a) every mass attracts other mass through force of gravity

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b) strength of gravitational force attracting any 2 objects is directly proportional to the product of their masses

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c) inverse square law- strength of gravity between 2 objects decreases with the square of the distance between their centers

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formula = F = G(m1m2/d^2)

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Escape Velocity

amount of velocity required to escape earth's orbit (40,000 km/hr)

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Moon's Tidal Force

difference in gravitational attraction from earth and moon on each side of the earth creates this

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Power

rate of energy flow (watts)

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Watt

1 joule/sec

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White

colors in spectrum are equally mixed

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Black

no light reflected

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Diffraction Grating

glass etched with many closely spaced lines, produce spectrum

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Speed (light)

wavelength x frequency

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Frequency

cycles per second (Hz)

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Light is an Electromagnetic wave

traveling vibrations of both electric and magnetic fields

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Photon

light behaves as a wave and particle

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Infrared

light with wavelengths longer than red light

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Radiowaves

longest wavelength

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Microwaves

light falling between infrared and radiowaves

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UV rays

light with wavelengths shorter than blue

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X Rays

shorter than UV rays

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Gamma rays

shortest rays

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Emission

light bulb emits visible light

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Absorption

when you place your hand near bulb, your hand absorbs some light, then warms hand

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Transmission

glass/air, forms of matter, can allow light to pass through

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Reflection/Scattering

light can bounce off matter, either all in same direction, or random

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Visible Light

what we can see, 400 nm to 700 nm

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90

Atomic Number

number of protons in nucleus

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Atomic Mass

combined number of protons and neutrons

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Sublimation

solid to gas

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Evaporation

liquid to gas

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Ionization

stripping electrons from atoms

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Pressure

force per unit area pushing on objects surface

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Intensity

amount of light at each wavelength

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Spectroscopy

process of obtaining a spectrum and reading the information it contains

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Continuous Spectrum

broad range of wavelengths without interruption (rainbow)

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Emission Line Spectrum

light is only emitted at specific wavelengths (bright lines against a black background)

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Absorption Line Spectrum

specific light wavelengths are absorbed (dark lines over rainbow background)

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