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54 Cards in this Set
- Front
- Back
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Constellation |
apparent grouping of bright stars, 88 determined by the IAU |
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Asterism |
familiar grouping of stars |
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Celestial Sphere |
scientific model, takes the earths equator, poles and horizon and projects it onto the celestial sphere. We can see half of the celestial sphere at any given time. (Zenith-above, Nadir-below) |
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Circumpolar |
stars that never 'set' |
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Apparent Motion of the Stars |
Because the Earth is rotating there is an apparent motion of the celestial sphere |
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Sidereal Day |
apparent time it takes for stars to complete one rotation around earth four minutes shy of 24 hours |
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Solar Day |
time that earth rotates, relative to the sun |
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Summer Solstice |
June 21st (for N hemisphere) the Sun is at its highest point in the sky |
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Winter Solstice |
December 21 (For N Hem) the sun is at its lowest point in the sky |
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Wavelength |
The measurement of distance between successive peaks, measured in nanometers.
I Nm = 10^-9 meters |
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Visible Light |
Wavelength between 400 (violet) and 700 (red) nm |
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Relationship between Wavelength and Frequency |
Inverse relationship. Short wavelengths and high frequencies are dangerous |
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Electromagnetic Spectrum |
Short Wavelengths/ High Frequency (dangerous) Gamma Ray Xray UV Visible (400-700nm) Infrared Microwave Radio Long Wavelength Low Frequency |
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Synodic Moon phase |
relative to the Earth-Sun line (29.5 days) |
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Sidereal Moon Phase |
relative to the stars (27.3 days) |
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Umbra |
Total shadow |
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Penumbra |
partial shadow |
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Archaeostronomy |
Stone/bronze age: realized cyclical nature of sky motions, used myths to describe it
Stonehenge Monuments lined up with solstices because on the solstice the sun is either the highest or lowest point in the sky rather than an equinox when it is equal |
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Eratosthenes |
-Measured the size of the Earth by measuring a distance along the Nile, angle of sunlight, estimated the radius -did it on the summer solstice |
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Aristotle |
-Earth didn't move -Earth is imperfect, heavens are perfect |
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Ptolemaic Universe |
Epicycles: theory that helped to predict eclipses by making 89 circles with the earth at the center -introduced to explain the cause of retrograde motion |
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Copernicus |
-Heliocentric -observed the retrograde motion of a planet which occurs when earth is moving faster and passes the planet as they both orbit the sun -Inner planets to around faster, looks like mars is going backwards, but it is not |
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Tycho Brahe |
-used very good mechanical instruments to measure the stars and planets with the naked eye (geocentric) -Saw the Supernova of 1572- heavens were not perfect! |
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Kepler's Laws |
1. Planets move in elliptical orbits -Eccentricity : e=c. 2. Equal areas in equal times 3. Period^2 = distance^3 |
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Galileo |
-first to use a telescope -Four moons of Jupiter, sun spots, phases of venus -heavens are imperfect |
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Motions of the planets |
Outer planets appear to move east relative to the stars (only apparent, there is actually no retrograde) |
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Mass |
Matter that gravitates and is made of atoms |
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Energy |
work/ability to do work -Potential Energy: change -Kinetic Energy: energy at motion |
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Force |
An entity tending to move objects , causes or tends to cause action, not visible |
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Newtons Laws of Motion |
1. A body continues at rest or in uniform motion in a straight line unless acted upon by some net force 2. the acceleration of a body is inversely proportional to its mass, directly proportional to the net force and in the same direction as the net force 3. To every action, there is an equal and opposite reaction |
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The Universal Law of Gravity |
Any two bodies are attracting each other through gravitation, with a force proportional to the product of their masses and inversely proportional to the square of their distance. Moon and Earth exert the same amount of g force on each other |
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how would the gravitational force between the earth and the moon change if the moon was orbiting further away? |
reduces by a factor of four |
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Orbital Velocity |
In order to stay on a closed orbit, an object has to be within a certain range of velocities |
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Center of Mass |
one object does not orbit another, orbiting around the center common center of mass. |
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Why are there two tides a day? |
because of the difference of the moons gravitational attraction on the opposite sides of the earth. Higher gravity pulls water towards the moon on the near side and lower gravity attracts it less on the far side |
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Spring Tides |
near full moon and new moon |
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Neap Tides |
near first quarter and third quarter |
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Einsteins Theories of Relativity |
1. Theory of Special Relativity: treats uniform motion at speeds approaching c 2. Theory of General Relativity: explains the nature of gravity as geometrical 3. Space and gravity are the same thing |
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2 Postulates for the theory of special relativity |
Postulate 1: Relativity Principle: Observers can never detect their uniform motion, except relative to other objects. your pov is stationary - everything else is moving. Uniform motion is only relative. Postulate 2: the velocity of light, c, is constant and will be the same for all observers, independent of their motion relative to the light source |
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Effects of Special Relativity |
Time Dilation, Length contraction, E=mc2, energy of a body at rest is not 0, Light has energy (and travels at the universal speed limit of c), Mass has energy |
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Equivalence Principle |
Observers cannot distinguish locally between inertial forces due to acceleration and uniform gravitational forces due to the presence of massive bodies (bear in a box example) |
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Relativity Principle |
Observers can never detect their uniform motion, except relative to other objects |
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Light Bending |
-Gravity, inertia, and acceleration are related via space time -Gravity is a geometric property of space time, configured by local massive objects -gravtity curves spacetime -light bending - following the curvature of space from g bending from massive objects |
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Tests of Theory of General Relativity |
1. Precession of the orbit of Mercury 2. Sun light bent during eclipse (because of g bending spacetime) |
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Coulomb Force |
Electrons bound to the nucleus due to attraction to protons
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Excitation of Atoms |
- photon is absorbed (from the right energy), e transitions into a higher orbit -More energy is required to move an electron up one energy level the closer it is to the nucleus |
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Temperature |
measure avg kinetic energy of particlees |
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Thermal Energy |
total energy of al moving particles |
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Heat |
flow of thermal energy from hot to cold |
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Blackbody Spectrum |
the spectrum of a star's light, approximately thermal spectrum |
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Wiens Law |
the peak of a blackbody spectrum shifts towards shorter wavelengths as the temperature increases |
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Stellar Spectra |
The spectra of stars are more complicated than pure blackbody spectra, contain characteristic lines, called absorption lines, can identify the elements using these absorption lines |
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Kirchoffs Law of Radiation |
-a solid liquid or dense gas excited to emit light will radiate all wavelengths and thus produce a continuous blackbody spectrum -A low density gas excited to emit light will do so at specific wavelengths and produce emission spectrum -if continuous spectrum passes through low density gas, absorption spectrum |
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Doppler Effect |
Light from a source that is moving away/toward us is shifted to longer/shorter wavelengths Speed of light is constant |
