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correct answers
What is our planet in the solar system
part of the solar system, in the milky way galaxy, in local group of galaxies, in local supercluster
how did we come to be
the Big Bang which produced hydrogen and helium
where did elements come from
the big bang produced H and He, which are the base of other elements constructed in stars
how old are we in comparison to the universe
human civilization is a second of a year, and our own life is a fraction of a second
how is earth moving
earth rotates on an axis once a day and orbits the Sun at 1 AU (150 million kilometers)
how can we specify the position of an object in the local sky
altitude above the horizon and direction along the horizon
why do stars rise and set
because of Earth's rotation
why do the constellations we see depend on latitude and time of year
your location determines which constellations are hidden by earth
the time of year determines the location of the Sun and the celestial sphere
what causes the seasons
the tilt of the Earth's axis
what are the summer and winter solstices
when the Northern hemisphere gets its most and least direction sunlight
what are the spring and fall equinoxes
when both hemispheres get direct and equal sunlight
how does the orientation of Earth's axis change with time
the tilt remains about 23.5 degrees (so the season pattern is not affected) but the the cycle slowly and subtly changes the orientation of earth's axis every 26,000 years
why do we see phases of the moon
half the Moon is lit by the Sun, half is in shadow, and its appearance to us is determined by the relative positions of the Sun, Moon, and Earth
each planet orbits the sun in a path called an ellipse with the sun at one focus
Kepler's Second Law of Planetary Motion
As a planet moves around its orbit it sweeps out equal areas in equal times.
a planet travels faster when it is nearer to the sun and slower when it is farther form the sun
Kepler's Third Law of Planetary Motion
The square of the orbital period of any satellite is proportional to the cube of its average distance from its central mass
More distant planets orbit the Sun at slower average speeds: p2 = a3 (p= orbital period in years and a= average distance from Sun in AU)
Galileo
his experiments and observations overcame the remaining objections to the Sun-centered solar system model
what is a scientific theory
A model that explains a wide variety of observations in terms of a few general principles and that has survived repeated and varied testing
how is astrology different from astronomy
- Astronomy is the scientific study of the universe
and the celestial objects within it
- Astrology assumes that the positions of celestial
objects influence human events
speed
distance/time
rate at which objects move
velocity
Speed in a given direction
Acceleration
rate of change of velocity
Momentum
mass x velocity
force
causes change in moment, produces acceleration
mass
the quantity of matter in an object
conservation of angular momentum
keeps a planet rotating and orbiting the Sun
conservation of energy
Energy cannot be created or destroyed, but it can be transformed from one form to another
types of energy
kinetic, potential, radiative
How do gravity and energy together allow us to understand orbits
Change in total energy is needed to change orbit
Add enough energy (escape velocity) and object leaves
How does gravity cause tides?
Moon's gravity pulls harder on near side of Earth than on far side
Difference in Moon's gravitational pull stretches Earth
the moon's gravity stretches earth and its oceans
Why do all objects fall at the same rate?
Mass of object in Newton's second law exactly cancels mass in law of gravitation
light is
a form of energy
light comes
in many colors than combine to form white light
how do light and matter interact
Matter can emit light, absorb light, transmit light, and reflect (or scatter) light.
Interactions between light and matter determine the appearance of everything we see
light emission
matter releases energy as light
light absorption
matter takes energy from light
light transmission
matter allows light to pass through it
light reflection (scatter)
matter repels light in another direction
what is light
As temperature rises, a substance transforms from a solid to a liquid to a gas, then the molecules can dissociate into atoms
Stripping of electrons from atoms (ionization) turns the substance into a plasma
how is energy stored in atoms
the energies of electrons in atoms correspond to particular energy levels
atoms gain and lose energy only in amounts corresponding to particular changes in energy levels
what are the three basic type of spectra
Continuous spectrum, emission line spectrum, absorption line spectrum
how does light tell us what things are made of
chemical fingerprints
-- each type of atom has a unique set of energy levels
-- each transition corresponds to a unique photon energy, frequency, and wavelength
-- downward transitions produce emission lines; upward transitions produce absorption lines
how does light tell us the temperature of planets and stars
Nearly all large or dense objects emit a continuous spectrum that depends on temperature
The spectrum of that thermal radiation tells us the object's temperature
blue light
hotter, closer
red light
cooler, further
light spectrum from shortest to longest wavelength
gamma rays, x-rays, ultraviolet, visible light, infrared, microwaves, radio waves
how does light tell us the speed of a distant object
the Doppler effect tells us how fast an object is moving toward or away from us
closer = higher pitch (blue light)
further = lower pitch (red light)
star
large, glowing ball of gas that generates heat and light through nuclear fusion
planet
a moderately large object that orbits a star, Ade spherical by gravity, (mostly) shines by reflected light
moon (or satellite)
light year
the distance light travels in one year, about 6 trillion miles (10 trillion km)
atoms
Building blocks of all chemical elements
where do we come form
we are "star stuff"
how we came to be
Big Bang, first stars, stellar death, 2nd gen stars
Big Bang
birth of universe, creation of H and He
first stars
fusion creates heavy elements
stellar death
seeds space with heavy elements
2nd gen stars
solar systems with planets
the earth rotates around its axis...
once every day (rotation)
Earth orbits around the sun
once every year (orbit)
How do galaxies move within the universe?
Galaxies are carried along with the expansion of the universe
Hubble discovered that
all galaxies outside our Local Group are moving away from us
the more distant the galaxy, the faster it is racing away
(we live in an expanding universe)
distant galaxies are
moving away from us
the further away galaxies are
the faster they are moving away from us
celestial equator
the extension of Earth's equator onto the celestial sphere
we measure the sky using
angles
An object's angular size appears ___ if it is farther away
smaller
altitude
(angle) above horizon
direction
along horizon
meridian
line passing through zenith and connecting N and S points on horizon
zenith
the point directly overhead
horizon
all points 90 degrees away from zenith
why do stars rise and set
Earth rotates west to east, so stars appear to circle from east to west
earth's daily motion
As the Earth rotates, the sky appears to rotate in the opposite direction around the celestial poles
If you are standing at the poles, nothing rises or sets
If you are standing at the equator, everything rises & sets 90 degrees to the horizon
We cannot see stars near the
south celestial pole
Stars near the north celestial pole are
circumpolar and never set
latitude
position north or south of equator
Longitude
the moon we see comes from
the moon's orbit (months)
Seasons are caused by
The tilt of the Earth's axis and how it affects the directness of sunlight
Summer Solstice
June (highest path)
winter solstice
december (lowest path)
spring equinox
march (precisely due)
fall equinox
September (precisely due)
eclipse
when either passes through the other's shadow
when the moon's orbit intersects the ecliptic (node)
new moon
solar eclipse
must be in the moon's shadow to see it
full moon
lunar eclipse
retrograde motion
The apparent motion of the planets when they appear to move backwards (westward) with respect to the stars from the direction that they move ordinarily
scientific thinking is based on
everyday ideas of observation and trial-and-error experiments
How did the Greeks explain planetary motion
earth at the center
objects move on perfect spheres or circles around earth
the Ptolemaic model
