Exam 1 Flashcards
The average distance between Earth and the Sun
Astronomical unit (AU)
The distance light travels in one Earth year
Light year (ly)
Light travels at an indefinite speed; and takes some time to reach our eyes.
False; true
The closest star to the sun
Alpha Centauri
The Galaxy is about ________ ly across.
100,000
How big is the Observable Universe?
28.6 billion ly
A way of expressing very large or small numbers in a compact form.
Scientific Notation
Singularity that gives birth to the universe
The Big Bang
The Universe expands faster than the speed of light
Inflation Period
How are stars formed?
Massive gas/plasma clouds are compressed until a single sphere is hot enough for nuclear fission.
Most massive star, creating the elements more massive than iron
Supernova
The solar system formed 4.5 billion years ago.
True
Earth’s orbit divided by Earth’s orbital period
Speed
How fast is Earth’s orbit?
107,000 mph
Brightest star in the sky
Sirius
How to describe the location of a star in the sky
Celestial sphere
Angle of 0o to 90o
Altitude
Measured from North (0 degrees) going clockwise around a complete circle (360 degrees)
Azimuth
The sun and the moon do not have the same angular size.
False
How do we measure angular distance?
1 degree is equal to 60 arcminutes.
1 arcminute is equal to 60 arcseconds.
Stars “rise and set” due to the spinning of the Earth.
True
A star whose daily circle causes it to be visible at all times
Circumpolar
Why are some stars circumpolar?
Their daily circle is entirely above the entire horizon.
Why should we be careful when using celestial coordinates?
The time of day, location, and day in the year will be different.
How are we tilted downward, toward the sun?
Hemisphere tilted down due to changing tilt.
March 21st
Equal day and night
All places on Earth
Spring Equinox
June 21st
Northern Hemisphere has longest period of light
Summer Solstice
September 22nd
Equal day and night
All places on Earth
Fall Equinox
December 21st
Southern Hemisphere has longest period of light
Winter Solstice
Earth is closer to the Sun during winter.
True
Why is the Arctic Circle called “the land of the midnight sun”?
The sun doesn’t fall below horizon for one week during the Summer Solstice.
Why are the seasonal changes more noticeable in the Northern Hemisphere?
Land mass
The gradual wobble of the Earth’s axis with the respect to the Sun. (It has a 26,000 year period.)
Precession
Lunar Phase: Moon not visible
New Moon
Lunar Phase: Right sliver of moon
New moon to Full moon
Waxing Cresent
Lunar Phase: RIGHT half of moon visible
First Quarter
Lunar Phase: Moon full other than sliver on left side
Waxing Gibbous
Lunar Phase: Whole moon visible
Full Moon
Lunar Phase: Almost all of moon visible except for sliver on right side
Waning Gibbous
Lunar Phase: LEFT half of moon visible
Third Quarter
Lunar Phase: Left sliver
Waning Cresent
“Exposing” phases of moon
Waxing
“Retreating” phases of moon
Waning
The moon does not create its own light. The moon reflects the sun’s light.
True
What does the “Moon’s Synchronous Rotation” mean?
The moon’s orbital period is the same as its rotational period.
Time required to complete one cycle
Period
The shadow the moon casts that reflects no sunlight
Umbra
The shadow the moon casts that reflects partial sunlight
Penumbra
Lunar Eclipse: moon passes through the umbra
Total Lunar Eclipse
Lunar Eclipse: moon partially on the umbra
Partial Lunar Eclipse
Lunar Eclipse: moon passes through penumbra
Penumbral Lunar Eclipse
A lunar eclipse can occur during any phase.
False. It can only occur during a full moon.
The eclipses’ 18 year 11.3 day cycle
Saros cycle
Solar Eclipse: the moon is in front of the Earth, completely blocking out the sun for a portion of the Earth
Total Solar Eclipse
Solar Eclipse: areas not experiencing total solar eclipse
Partial Solar Eclipse
Solar Eclipse: the moon’s umbral shadow does not reach Earth
Annular Solar Eclipse
Understood during eclipses, responsible for GPS
General relativity
What are the “wandering stars” in the sky and why are they called that?
They are planets. They are called that because they followed a different pattern than the rest of the stars.
Appearing to move backward as Earth catches up and passes during orbit of the sun
Retrograde Motion
Star appearing to change its position
Stellar Parallax
Originally used to tell time
Sun dial
Most widely used calendar
Gregorian Calendar
Occurs every four years except in years that end in 00 not divisible by 400
Leap year
Said that heavenly motion must be perfect circles
Plato
Argued for an Earth-centered universe (geocentric)
Aristotle
Introduced multiple circles to circles to explain retrograde motion
Apollonius
Finalized geocentric model
Ptolemy
Why is one model favored over another?
Which one sounds better seems to make more sense to people.
What evidence could sway a person to believe one model over another?
Disregarding science for a more favorable idea (popularity contest).
Revisited the heliocentric model and provided more detailed calculations with support of the church.
Nicholas Copernicus
Measured parallax for moon and comet and first supernova.
Tycho Brahe
Introduced the ellipse
Johannas Kepler
Kepler’s Second Law
As a planet moves around its orbit, it sweeps out equal area in equal time.
Kepler’s Third Law
More distant planets orbit the sun at a slower average speeds. Planets closer to the sun move at higher speeds.
First to use telescope for scientific data and challenged the ideas of the “old world.”
Galileo Galileo
What is evidence that the heavens are imperfect?
Comet and supernova
Brightness cannot be used to estimate distances.
True
A force needed to stop an object. Objects share the Earth’s motion through space.
Gravity
What did Galileo discover near Jupiter?
Four “stars” orbiting it; moons
How did Venus help prove the validity of the heliocentric model?
The observed phases of Venus are only possible with a heliocentric model. (Phases occur just like the Moon)
First observable direct evidence showing the rotation of Earth.
The Foucalt Pendulum
Distance traveled divided by the time elapsed
Speed
Change of position divided by time elapsed
Velocity
Change of velocity divided by time elapsed
Acceleration
How do we change an object’s acceleration?
Increase or decrease velocity, or change in direction while keeping constant speed (turning)
Any action that can cause a change in an object’s momentum
Force
The sum of all forces acting on an object
Net force
Momentum of a spinning/rotating product of its moment of inertia and angular velocity
Angular momentum
A measurement of an object’s resistance to rotating depends on mass and how the mass is distributed
Moment of intertia
An action that can cause a change in an object’s angular momentum
Torque
The measurement of an object’s resistance to movement
Mass
The force acting on an object depends on mass acceleration due to gravity, and forces acting on the object weight is equal to mass times gravity
Apparent weight
An apparent lack of an acceleration due to gravity in an environment
Weightlessness
In outer space, in presence of no objects with mass
True weightlessness
How do you “become heavier” in an elevator?
Elevator accelerating up
How do you “become lighter” in an elevator?
Elevator accelerating down
This person quantified the laws of nature, recognized gravity is universal, and invented the reflecting telescope and calculus.
Sir Isaac Newton
An object moves at a constant velocity unless a net force acts to change its speed or direction
Newton’s First Law of Motion
How to change the motion of an object. The force is equivalent to mass multiplied by acceleration. It requires a net force acting on the object.
Newton’s Second Law of Motion
For any force, there is always an equal and opposite reaction force
Newton’s Third Law
A force required for an object to follow a circular path
Centripetal force
Momentum is conversed unless acted upon by an external force
Linear momentum
- Why the Earth doesn’t need fuel to move around the sun
2. Why the Earth moves faster when it is closer to the sun
Angular momentum
Energy for any reaction or interaction is conserved. It can be transferred, but not created nor destroyed.
Conservation of Energy
Associated with a moving object, depends only on the motion of the object
Kinetic energy
The potential to do something; having stored energy
Potential energy
Collective kinetic energy of the random motion of particles
Thermal energy
Measurement of the average kinetic energy
Temperature
Energy that light can carry, a form of kinetic energy
Radiative energy
Does it physically make sense to have negative temperatures?
No; mass cannot be negative
Depends on the temperature of the object and the number of particles contained within the object
Thermal energy
Results from the relative positions of two or more objects, and is caused by the gravitational force
Gravitational Potential Energy
States that it is possible to convert mass into energy and vise versa.
Mass-Energy Relation
What are the most common places where Mass-Energy is seen?
Nuclear reactions
States every object with mass will attract all other objects with mass with a force that is proportional to the product of their masses and inversely proportional to the square of their separation distance
Newton’s Law of Universal Gravitation
Why are you not being pulled towards other students?
The force is minuscule. We are surrounded by objects and each pulls on us.
Ellipses are not the only possible orbit.
True
Allows the mass of an orbited object to be measured. This only works with a massive orbited object and a much smaller orbiting object.
Newton’s version of Kepler’s Third Law
Any object has a total energy which is the sun of its kinetic and potential energies
Orbital energy
Most objects in the solar system do not interact with each other. On occasion, two objects will pass each other so one or both will have their orbits changed.
Gravitational Encounters
Minimum velocity to leave an object, like Earth, and never return
Escape Velocity
Noticeable changes in the water levels of the oceans over the course of a day. Caused by a difference in the gravitational force on each side of Earth.
Tides
The ________ provides most of the tidal waves.
Moon
However, so does the sun
Large tides that occur at new or full moons
Spring tides
Smaller tides that occur at third and quarter moons
Neap tides
Causing Earth’s rotation to slow down and the moon to move further away from the Earth
Tidal Friction
An object experiencing the gravitational force near the surface of a large body. All objects have the same acceleration/rate.
Free Falling Object
The average distance between Earth and the Sun, which is about 150 million kilometers.
Astronomical unit
The distance that light travels in 1 year, which is about 9.46 trillion kilometers.
Light year
Which of the following correctly lists our “cosmic address” from small to large?
Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then
The planets are marble-sized or smaller and the nearest stars are thousands of miles away.
The total number of stars in the observable universe is roughly equivalent to:
The number of grains of sand on all the beaches on Earth
When we say the universe is expanding, we mean that
The average distance between galaxies is growing with time.
If stars existed but galaxies did not
We would not exist because we are made of material that required recycling in galaxies.
Could we see a galaxy that is 20 billion light-years away? Explain.
No, because it would be beyond the bounds of our observable universe.
The age of our solar system is about:
1/3 the age of the universe
The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that:
The universe is expanding.
Suppose we wanted to make a scale model of the Local Group of Galaxies, in which the Milky Way Galaxy was the size of a marble (about 1 cm in diameter). How far from the Milky Way Galaxy would the Andromeda Galaxy be on this scale?
25 cm
Suppose we wanted to make a scale model of the Local Group of Galaxies, in which the Milky Way Galaxy was the size of a marble (about 1 cm in diameter). How far would it be from the Milky Way Galaxy to the most distant galaxies in the observable universe on this scale?
1.4 km
Two stars that are in the same constellation
May actually be very far away from each other.
The North Celestial Pole is 35 ∘ above your northern horizon. This tells you that
You are at latitude 35o N
Beijing and Philadelphia have about the same latitude but very different longitudes. Therefore, tonight’s night sky in these two places:
Will look about the same.
In winter, Earth’s axis points toward the star Polaris. In spring:
the axis also points toward Polaris.
When it is summer in Australia, the season in the United States is
Winter
If the Sun rises precisely due east:
It must be the day of either the spring or fall equinox.
A week after full moon, the Moon’s phase is:
Third quarter
The fact that we always see the same face of the Moon tells us that:
The Moon’s rotation period is the same as its orbital period.
If there is going to be a total lunar eclipse tonight, then you know that:
The moon’s phase is full
How many arcminutes are in a full circle?
21,600 arcminutes
How many arcseconds are in a full circle?
1,296,000
When we see Saturn going through a period of apparent retrograde motion, it means:
Earth is passing Saturn in its orbit, with both planets on the same side of the Sun
In the Greek geocentric model, the retrograde motion of a planet occurs when
The planet actually goes backward in its orbit around Earth
Which of the following was not a major advantage of Copernicus’s Sun-centered model over the Ptolemaic model?
It made significantly better predictions of planetary positions in our sky.
When we say that a planet has a highly eccentric orbit, we mean that:
In some parts of its orbit it is much closer to the Sun than in other parts.
Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler’s second law:
Earth travels faster in its orbit around the Sun in January than in July.
According to Kepler’s third law:
Jupiter orbits the Sun at a faster speed than Saturn.
Tycho Brahe’s contribution to astronomy included
Collecting data that enabled Kepler to discover the laws of planetary motion
Galileo’s contribution to astronomy included:
Making observations and conducting experiments that dispelled scientific objections to the Sun-centered model.
Which of the following is not true about scientific progress?
Science advances only through the scientific method
A theory is essentially an educated guess.
False
When Einstein’s theory of gravity (general relativity) gained acceptance, it demonstrated that Newton’s theory had been:
Incomplete
Suppose you visit another planet. Your mass would be ________ as on Earth, but your weight would be ________.
The same; different
Which person is weightless?
a. A child in the air as she plays on a trampoline.
b. A scuba diver exploring a deep-sea wreck.
c. An astronaut on the Moon.
a. A child in the air as she plays on a trampoline.
Consider the statement “There’s no gravity in space.” This statement is
Completely false
If you want to make a rocket turn left, you need to fire an engine that shoots out gas ________.
To the right
Compared to its angular momentum when it is farthest from the Sun, Earth’s angular momentum when it is nearest to the Sun is
The same
As an interstellar gas cloud shrinks in size, its gravitational potential energy
Gradually transforms into other forms of energy
If Earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be
One-quarter as strong
According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?
Earth’s orbit would not change
If the Moon were closer to Earth, high tides would be ________ as they are now.
Higher
Which of the following represents a case in which you are not accelerating?
a. Going from 0 to 60 miles per hour in 10 seconds
b. Driving in a straight line at 60 miles per hour
c. Slamming on the brakes to come to a stop at a stop sign
d. Driving 60 miles per hour around a curve
b. Driving in a straight line at 60 miles per hour
