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What is wrong about making the Kessel Run in 12 parsecs?
He's clearly phrasing this to talk about a time, but "parsec" is a unit of distance.
Sizes in Space, units from smallest to largest?
Kilometer, AU, Lightyear
In the Hidden Figures launch scene, how should the rocket's velocity change over time as it burns fuel?
The rocket applies constant force on a decreasing mass, and that produces increasing acceleration upward.
How long would it take a typical Earth spaceship (speed of 30 kilometers/second) to get to the nearest star (Proxima Centauri, at 4.3 lightyears)?
43,000 years
How long is Mark Watney waiting for NASA to respond once he says something?
8-40 minutes
If Brie Larson's Infinity stone powers obeyed Newton's Laws, what should have happened when she blasted Jude Law backward into the rocks?
She should have flown backward away from him with the same momentum
Which photo pair shows Earth correctly scaled in comparison to the Sun?
The Sun's diameter is more than 100 times Earth's diameter.
What should happen if Arnold ends up on the surface of Mars?
Air suddenly will blow out of lungs due to vacuum
This painting represents the Sun and planets (and one of the largest dwarf planets) of our solar system. What is not to scale in this painting?
The distances between the planets are not shown to scale.
Which of the following has your "cosmic address" in the correct order?
You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
About where is our solar system located within the Milky Way Galaxy?
about halfway from the center of the galaxy to the edge of the galactic disk
1 astronomical unit (AU) is
about 150 million kilometers
Earth’s avg. distance from the sun
Jupiter lies about 5.2 of these from the sun
1 light-year
the star Sirius lies about 8 of these from the Sun
the distance light travels in 1 year
about 10 trillion kilometers
Mars is about ____ from the Sun.
1.5 AU
Jupiter is about ____ from the sun
5 AU
The star Sirius is about ____ from the Sun.
8 light-years
The diameter of the Milky Way Galaxy is
about 100,000 light-years
The distance from Earth to the Moon is ____
less than 0.01 AU
Rank the following items that describe distances from longest distance (left) to shortest distance (right)
Longest:
- the distance from the Milky Way Galaxy to the Andromeda Galaxy
- the distance from the sun to the center of the Milky Way Galaxy
-the distance from Earth to Alpha Centauri
-one light-year
-the distance across our solar system(distance)
-the avg. distance from Earth to the sun
-one astronomical unit (AU)
Shortest:
Light takes approximately one second to travel from Earth to the Moon. This means that the Moon is approximately
300,000 km from the Earth
Which of the following statements does not use the term light-year in an appropriate way?
It will take me light-years to complete this homework assignment. Light-years is a distance not a time.
In Season 1, Episode 14 of "Star Trek: Discovery", the USS Discovery has just come back from an alternate universe. Starfleet wants them to proceed to Starbase 1 (their headquarters), which they say is "100 AU from Earth and over a lightyear from the Discovery's current position".
Given that Starbase 1 is 100 AU (Astronomical Units) away from the Earth, how you would describe Starbase 1's location?
In orbit around the Sun, beyond the orbit of Pluto.
Given that the USS Discovery is currently over a light year away from Earth and Starbase 1, how would you describe the Discovery's location?
Outside the Solar System, a quarter of the way to the nearest star
Represent 1 light-second in kilometers.
1 light-second =3.00×105 km
Represent 1 light-second in miles.
1 light-second =1.86×105 mi
Represent 2 light-minutes in kilometers.
2 light-minutes = 3.60×107 km
Represent 1 light-hour in kilometers.
1 light-hour =1.08×109 km
Represent 2 light-days in kilometers.
2 light years=5.18×1010 km
One light-minute is the distance that light travels in one minute. How far is this, in kilometers
18 million km
Depending on orbital positions, what is the shortest possible time NASA Mark Watney would have to wait, after sending a message, before he might receive a response?
8 minutes
Depending on orbital positions, what is the longest possible time NASA Mark Watney would have to wait, after sending a message, before he might receive a response?
40 minutes
Sunlight takes about 8.4 minutes to travel from the Sun to Earth. When NASA's New Horizons Spacecraft passed Pluto in 2015, it was about 32 AU from Earth. About how long did it take for transmitted images of Pluto to travel from the spacecraft to Earth?
4 ½ hours
n the movie Apollo 13, Tom Hanks says the famous line "Houston, we have a problem." instantaneously after Houston asks him via radio transmission (a form of light) for the mission's status. At that point, the Apollo 13 capsule was about 3/4 of the way to the Moon, or about 300,000 kilometers away from the Earth.
How long of a delay should there have been between when Houston spoke to the astronauts, and when their response came back to Houston?
2 seconds, Radio waves are a form of light, and hence travel at the speed of light (300,000 kilometers/second). If they must travel 300,000 kilometers in each direction, then the transmission delay between message and response is 1 second in each direction, or 2 seconds total.
In the pilot episode of "Star Trek: Voyager", Ensign Kim exclaimed in dismay that they were "over 70,000 lightyears" from Federation territory. Later in the episode, they conclude that getting back would take a little over 70 years.
Obviously the Federation has a (fictional) way of going faster than the speed of light. Assuming it isn't a problem to break the laws of physics, how fast can the USS Voyager go?
1000 lightyears/year
The nearest star, Proxima Centauri, is about 4.3 lightyears away. That's about average for the distance between stars in our galaxy. Assuming the speed from Part A, how long does it take a typical Federation starship to get from one star to the next?
1.56 days
In the Star Trek universe, when ships are traveling faster than the speed of light (at warp speed), there are often at least some visibly moving stars that go from directly ahead to directly behind within a few seconds. How is this inconsistent with the answers to parts A and B?
Stars' apparent motion is far too quick compared to the implied speeds.
Suppose the humans in Avatar wanted to visit the Navi and to reach Alpha Centauri (4.4 ly from the Solar system) in 130 years. How fast would you have to go, in km/second?
v=1.0×104 km/s
How many times faster is the speed you found in part A than the speeds of our fastest current spacecraft (around 15 km/secondkm/second)?
v/vcurrent =680
Choose the correct definitions of speed, velocity, and acceleration.
Acceleration is the rate of change of velocity in time.
Velocity is used to describe how fast the object is moving and tells us in which direction it is going.
Speed is used to describe how fast the object is moving.
What are the units of acceleration?
m/s²
What is the acceleration of gravity?
The acceleration of an object in free-fall. It is 9.8 m/s² near the surface of the Earth and varies from place to place.
In many television shows and movies (such as Star Wars and Guardians of the Galaxy), spacecraft flying through the vacuum of space are shown banking and swooping like airplanes.
Why does this violate one or more of Newton's Laws?
An aircraft turns by diverting airflow over its wings, but space is effectively a vacuum, so there is nothing exerting a net force.
Which of the following is an example in which you are traveling at constant speed, but not at constant velocity?
driving around in a circle at exactly 100 km/hr
If you want to reverse direction in a moving spaceship that is currently moving directly ahead, and your ship has one rocket engine on it, what direction would you fire the rocket (i.e., point the rocket's exhaust) to do so?
Directly ahead
If you want to be moving directly to the left in a moving spaceship that is currently moving directly ahead, and your ship has one rocket engine on it that you can only point in one direction, what direction would you fire the rocket (i.e., point the rocket's exhaust) to do so?
Diagonally, forward and right
You start out with forward motion (that you must get rid of), and you want to acquire leftward motion. To achieve this all-in-one move, you would fire your engine ahead (to stop moving forward) and to the right (to start moving leftward) in a diagonal direction.
Which of the following statements is not one of Newton's Laws of Motion?
What goes up must come down.
Suppose an object is moving in a straight line at 50 miles/hr. According to Newton's first law of motion, the object will
continue to move in a straight line at 50 miles/hr until it is acted upon by a net force.
Consider Newton's second law states, often written as force = mass × acceleration. If a known force is applied to an object with a known mass, what does this law predict for the object's acceleration?
acceleration = force / mass
As we'll discuss more in Gravity week, if an object falls, the downward acceleration due to Earth's gravity is approximately 10 meters per second per second ( g=10 m/s2). If you drop a rock from a very tall building, how fast will it be going after 7 seconds?
vrock=70 m/s
As you sled down a steep, slick street, you accelerate at a rate of 5 meters per second squared. How fast will you be going after 4 seconds?
vsled=20 m/s
You are driving along the highway at a speed of 60 miles per hour when you slam on the brakes. If your acceleration is at an average rate of -25 miles per hour per second, how long will it take to come to a stop?
tstop=2.4s
Momentum is defined as
mass times velocity.
As long as an object is not gaining or losing mass, a net force on the object will cause a change in
velocity
Which law explains why a skater can spin faster by pulling his arms closer to his body, or spin slower by spreading his arms out?
the law of conservation of angular momentum
Suppose the Sun were to suddenly shrink in size but its mass remained the same. According to the law of conservation of angular momentum, what would happen?
The Sun rate of rotation would increase.
Examples of acceleration:
- a car is slowing down for a stop sign
-a ball is in freefall after being dropped from a high window
-a planet is orbiting the sun in an elliptical orbit
-a car is speeding up after being stopped
-a car is holding a steady speed around a curve
-a planet is orbiting the sun in an circular orbit
Examples of constant velocity:
-a spaceship is coasting without engine power in deep space
-an elevator is going upward at constant speed
-a car is driving 100 km/hr on a straight road
Examples of a change in momentum:
- a car is slowing down for a stop sign
-a ball is in freefall after being dropped from a high window
-a planet is orbiting the sun in an elliptical orbit
-a car is speeding up after being stopped
-a car is holding a steady speed around a curve
-a planet is orbiting the sun in an circular orbit
Examples of constant momentum:
-a spaceship is coasting without engine power in deep space
-an elevator is going upward at constant speed
-a car is driving 100 km/hr on a straight road
Examples of Net Force (force does not equal zero)
- a car is slowing down for a stop sign
-a ball is in freefall after being dropped from a high window
-a planet is orbiting the sun in an elliptical orbit
-a car is speeding up after being stopped
-a car is holding a steady speed around a curve
-a planet is orbiting the sun in an circular orbit
Examples of No net force
-a spaceship is coasting without engine power in deep space
-an elevator is going upward at constant speed
-a car is driving 100 km/hr on a straight road
Which of the following statements correctly state general principles of motion?
An object that is accelerating is also being acted upon by a (nonzero) net force.
Accelerated motion includes any motion involving a change in speed, change in direction, or both.
An object that is accelerating is also undergoing a change in momentum.
I say that two travelers, moving at difference speeds, both see the other one’s time going slower. This seems…weird. What happens if one of you turns around, and goes back to compare notes with the other? When you meet:
Whoever turns around and catches up, will find that they’re younger.
What feature of the Earth causes it to have seasons?
The Earth’s spin is tilted, so different hemispheres get more or less direct sunlight in summer vs winter.
Obi-Wan aside, what is "relative" about the special theory of relativity?
Motion only makes sense when we say what it's measured relative to.
If the superhero Johnny Storm (the Human Torch) races after a laser beam at 0.99c, what should he see?
The laser beam moves ahead of him at the full speed of light, easily reaching New York City first
Rank the events based on when they occurred, from longest ago to most recent.
Longest ago:
The Big Bang, the universe begins to expand
elements such as carbon and oxygen first exist
nuclear fusion begins in the sun
the earliest life on Earth
dinosaurs go extinct
earliest humans
Most Recent:
According to current scientific estimates, when did the Big Bang occur?
about 14 billion years ago
On the cosmic calendar, which compresses the history of the universe into a single year, about when did Earth form? *study cosmic calendar
in early September
On the cosmic calendar, which compresses the history of the universe into a single year, about when did life arise on Earth?
in September
On the cosmic calendar, which compresses the history of the universe into a single year, about when did early humans first walk on Earth?
just a few hours before midnight on December 31
In what sense are telescopes like time machines?
They allow us to see distant objects as they were long in the past.
The farther away we look in space, the further back we look in time. Therefore, when we look to very distant objects, we see them as they were long in the past, when the universe was much younger than it is today.
Because we live in an expanding universe, distant galaxies are farther away from us today than they were when the light we see from them started on its journey to us. So what do we mean when we say that a galaxy is 7 billion light-years away?
Its light has taken 7 billion years to reach us.
Suppose we observe a galaxy that is 13 billion light-years away. Which of the following can we conclude?
The galaxy formed before the universe was 1 billion years old.
The galaxy’s distance of 13 billion light-years means that its light traveled through space for 13 billion years to reach us. Therefore, the light left on its journey when the universe was only about 1 billion years old – which means the galaxy had already formed by that time.
How do scientists estimate the age of the universe?
They measure the speeds and distances of galaxies, and calculate the time it took for them to travel that distance (away from us).
Which of the following statements best describes what is "relative" in the theory of relativity?
The theory says that measurements of motion make sense only when we state what they are measured relative to.
In relativity, two people share the same reference frame only if they __________.
are not moving relative to one another
Note that they need not be located in the same place, or even anywhere near each other; the only requirement for being in the same reference frame is that they are not moving relative to one another.
You and Al are both floating freely in your spaceships. Suppose that Al is moving away from you at 85 km/hr. You throw a ball in his direction at a speed of 75 km/hr. According to Al, which of the following is going on?
He sees you moving away from him at 85 km/hr and the ball moving away from him at 10 km/hr.
Each of the following lists two statements. Which two are the basic premises for the special theory of relativity?
(1) The laws of nature are the same for everyone.
(2) The speed of light is the same for everyone.
Examine the first figure(Figure 1), in which you see Jackie's spaceship traveling at 1000 km/hr
as she throws the baseball at a speed of 100 km/hr
. How fast would you say the baseball is going?
1100 km/hr
Examine the second figure(Figure 2), in which you see Jackie's spaceship traveling at 1000 km/hr
, with the ship's headlight on. According to special relativity, Jackie would say that a beam of light from the headlight is traveling at __________, and you would say that the beam of light is traveling at __________.
Blank 1: the speed of light
Blank 2: the speed of light
Examine the third figure(Figure 3), in which you see Jackie's spaceship traveling at 0.99c
. This time, Jackie would say that a beam of light from the headlight is traveling at __________ and you would say that the beam of light is traveling at __________
Blank 1: the speed of light
Blank 2: the speed of light
Examine the fourth figure(Figure 4), which shows Jackie with her spaceship engines on, so that she accelerates continuously. As she accelerates, Jackie would say that __________ and you would say that __________.
Blank 1: the headlight beam is always racing away from her at c
Blank 2: her speed gets faster and faster but never quite as fast as the speed of the headlight beam
Based on these thought experiments, what can you conclude?
Jackie can never reach or exceed the speed of light.
In science, it is now well accepted that the speed of light is always the same and therefore nothing can travel faster than light. These ideas gained acceptance primarily because __________.
they have been verified through actual observations and experiments
Part complete
The measured value of the speed of light is about 300,000 km/s. Suppose a futuristic space train is traveling at 200,000 km/s with its headlights on. If you could measure the speed of the light from the headlights, you would find it to be _____.
300,000 km/s
You are racing away from Earth in a super space ship in which you can continually increase your speed by firing engines that never quit. Which of the following best explains how people on Earth will perceive your speed?
They will see your speed getting closer and closer to the speed of light but never reaching it.
Johnny Storm, AKA the Human Torch, has just seen an evil villain fire a laser beam at New York City, for some unknown-yet-evil reason! Johnny thinks he can outrun anything, so he races after it so he can get ahead of it and block it. Let's say Johnny immediately chases after the laser.
The laser is fired, and at the same instant, Johnny Storm races after it at 99% of the speed of light (0.99c). According to the rest of the Fantastic Four who are watching him, what happens? (Assume they could somehow watch a slow-motion replay to see what occurred.)
The laser beam reaches New York City first, but barely; it is going 1% of the speed of light faster than Johnny.
According to Johnny, what happens?
The laser beam moves out ahead of him at the full speed of light, easily reaching New York City first.
What do we mean by time dilation in relativity?
It is the idea that time really runs slower in reference frames moving relative to you.
What do we mean by length contraction in relativity?
It is the idea that if you measure the size of an object moving relative to you, you will find that in the direction of motion it is shorter than it would be at rest, while its size in other directions is unchanged.
Each item below shows three spaceships that are all moving relative to one another; the speeds are shown as they appear in Jackie’s reference frame. Rank the items according to how much time you would say passes (on your own ship) while Bob’s clock ticks off one second, from the shortest to the longest amount of time. To rank items as equivalent, overlap them.
Look at Mastering Astronomy
The faster an object is moving relative to you, the slower its time will run relative to yours. Slower time means its clock takes longer to tick off each second, so the rankings go in order of increasing speed for Bob relative to you.
Each item below shows three spaceships that are all moving relative to one another; the speeds are shown as they appear in Jackie’s reference frame. Rank the items according to the length that you (in the spaceship labeled "YOU") would measure for Bob’s spaceship, from shortest to longest. To rank items as equivalent, overlap them.
Look at Mastering Astronomy
The faster an object is moving relative to you, the shorter (in its direction of motion) you will measure it to be, so the ranking goes in order of decreasing speed for Bob as measured by you. Two of the items show Bob with the same speed relative to you (although in opposite directions), which is why the lengths are equal in those two cases.
To summarize the reason for the answer to Part A, the rate at which time passes on any object moving relative to you depends __________.
only on the object's speed toward or away from you,
You will always observe time passing more slowly on an object moving relative to you, no matter what direction it travels
Are there any circumstances under which you would measure a moving object's length to be longer than its rest length?
No, you will always measure a moving object's length to be shorter than its rest length.
Motion is relative, so a moving object always has some component of its motion toward or away from you. This component of its motion determines both the amount by which its length will be shortened from its rest length, and how much more slowly time will pass on the object relative to your time.
Each figure below shows a spaceship moving past your spaceship ("YOU") at the indicated speed. Imagine that you watch the other spaceship as its clock ticks off one second. Rank the figures according to how much time you would say passes (on your own ship) while the other ship’s clock ticks off one second, from the shortest to the longest amount of time.
Shortest: 0.7c, 0.75c, 0.8c, 0.85c Longest:
The faster an object is moving relative to you, the slower its time will run relative to yours. Slower time means its clock takes longer to tick off each second, which is why the rankings go in order of increasing speed (relative to YOU).
The four figures below are the same as those in Part A. This time, imagine that the passengers on the other spaceship are watching your clock as its ticks off one second. Rank the figures according to how much time the passengers (on the other ship) would say passes (on their ship) while they watch your clock tick off one second, from the shortest to the longest amount of time.
Shortest time: 0.7c, 0.75c, 0.8c, 0.85c Longest
The passengers on the other ship must observe the same effects on you as you observe on them, because both of you are in free-float reference frames and there is no way to say who is "really" moving. In other words, just as you say time is running slow on their ship, they say time is running slow on your ship. That is why the answer here is the same as the answer in Part A.
Consider again the spaceships from Parts A and B. Suppose that, at rest, both you and a passenger on the other spaceship have the same heart rate of 60 beats per minute. How will you and the passenger on the other spaceship observe each other’s heart rates as you pass by in your spaceships?
You would observe that the passenger in the other spaceship has a slower heart rate than you do, and she would observe that you have a slower heart rate than hers.
Each figure below shows a spaceship moving past your spaceship ("YOU") at the indicated speed. Assume that all the spaceships have equal length when at rest and that you watch the other spaceship as its clock ticks off one second. Rank the figures based on the length that you would measure for the other spaceship (in its direction of motion), from shortest to longest.
Shortest length: 0.85c, 0.8c, 0.75c, 0.7c Longest
The faster an object is moving relative to you, the shorter (in its direction of motion) you will measure it to be.
The four figures below are the same as those in Part A. This time, rank the figures based on your length as measured by the passenger in the other spaceship, from shortest to longest.
Shortest Length: 0.85c, 0.8c, 0.75c, 0.7c Longest
The passenger on the other ship must observe the same effects on you as you observe on her, because both of you are in free-float reference frames and there is no way to say who is "really" moving. In other words, just as you say that her ship is contracted in length, she says that your ship is contracted in length. That is why the answer here is the same as the answer in Part A.
