life in the universe chapter 13
The New Horizons spacecraft will fly past Pluto in 2015. About how long will it take it to reach the distance of the nearest stars?
100,000 years
Suppose that a spaceship is launched in the year 2120 on a round-trip journey of 50 light-years, traveling at 99.99% of the speed of light. Approximately what year would it be on Earth when the ship returns to Earth?
2220
Suppose that a spaceship is launched in the year 2120 on a round-trip journey of 50 light-years, traveling at 99.99% of the speed of light. If one of the crew members is 30 years old when the trip begins, about how old would she be (biologically) when she returns?
31
If we assume that 100,000 civilizations have arisen in our galaxy at random times in the past 5 billion years, then the average time between civilizations is about ________.
50,000 years
What does the famous formula E = mc2 have to do with special relativity?
It is a direct consequence of the theory.
What is time dilation?
The slowing down of time for an object moving past you at a speed close to the speed of light
Which of the following is not relative in the special theory of relativity?
The speed of light
Why do science fiction shows such as Star Trek and Star Wars use ideas such as "warp drive" and travel through "hyperspace"?
These ideas do not violate known laws of physics, even though we do not yet know whether they are really possible.
Why were phonograph records placed on the sides of the two Voyager spacecraft launched in the 1970s?
To provide information about humanity to any alien species that might someday come across them in interstellar space
Which of the following best describes our current understanding of the possibility of fast interstellar travel through hyperspace?
We do not know enough to say whether such travel is possible.
Which of the following questions best represents what we call Fermi's paradox?
Why haven't we yet found evidence of alien civilizations?
Suppose that a civilization is never able to build spacecraft that can travel faster than a few percent of the speed of light. Could they still colonize the galaxy? Why or why not?
Yes, in principle, within as little as about ten million years.
The rocket engines of our current spacecraft are powered by ________.
chemical energy
The special theory of relativity ________.
has been very well tested and verified
In nuclear fusion of hydrogen into helium, about 0.7% of the starting mass is converted to energy. How much more efficient is matter-antimatter annihilation than fusion?
more than 100 times as efficient
The amount of energy that would be needed to accelerate a large spaceship to a speed close to the speed of light is ________.
more than the total amount of energy currently used by everyone on Earth in a year
According to current scientific understanding, the idea that the Milky Way might be home to a civilization millions of years more advanced than ours is ________.
one possible solution to Fermi's paradox
The first successful launch of a satellite into Earth orbit was accomplished by ________.
the Soviet Union in 1957
Suppose there were a way to accelerate a spacecraft with a constant acceleration of 1g. If you were a passenger on the spaceship, how far, in principle, could you go in 60 years (as measured by you)?
to the Andromeda galaxy and back
For a solar sail to be useful in accelerating a spacecraft, the sail would need to be ________.
very lightweight (low mass) and very large in area
