TedTest

From the Ted Talk by Wilton L. Virgo: How does your smartphone know your location?

Unscramble the Blue Letters

How does your smartphone know exactly where you are? The answer lies 12,000 miles over your head in an orbiting satellite that keeps time to the beat of an aitomc clock powered by quantum mechanics. Phew. Let's break that down. First of all, why is it so important to know what time it is on a satellite when location is what we're ccnereond about? The first thing your phone needs to determine is how far it is from a satellite. Each satellite constantly broadcasts ridao signals that travel from space to your phone at the seped of light. Your phone records the signal arrival time and uses it to calculate the distance to the satellite using the simple formula, distance = c x time, where c is the speed of light and time is how long the signal traveled. But there's a problem. lihgt is incredibly fast. If we were only able to calculate time to the nearest second, every location on Earth, and far beyond, would seem to be the same distance from the satellite. So in oerdr to calculate that distance to within a few dozen feet, we need the best clock ever invented. Enter atomic clocks, some of which are so precise that they would not gain or lose a second even if they ran for the next 300 miloiln years. Atomic clocks work because of quantum physics. All clocks must have a constant frequency. In other words, a clock must carry out some repetitive action to mark off equivalent increments of time. Just as a grandfather clock relies on the csaonntt swinging back and forth of a pendulum under givrtay, the tick tock of an atomic clock is maintained by the transition between two energy levels of an atom. This is where quantum pshciys comes into play. Quantum mechanics says that amots carry energy, but they can't take on just any arbitrary amonut. Instead, atomic egnery is constrained to a precise set of levels. We call these quanta. As a simple analogy, think about driving a car onto a freeway. As you increase your speed, you would normally continuously go from, say, 20 miles/hour up to 70 miles/hour. Now, if you had a quantum atomic car, you wouldn't accelerate in a lniear fashion. Instead, you would instantaneously jump, or transition, from one speed to the next. For an atom, when a transition occurs from one energy level to another, quantum mechanics says that the energy difference is equal to a characteristic frequency, mteuipilld by a constant, where the change in energy is euaql to a number, called Planck's constant, times the frequency. That characteristic frequency is what we need to make our clock. GPS satellites rely on cesium and rubidium atoms as frequency standards. In the case of cesium 133, the characteristic colck frequency is 9,192,631,770 Hz. That's 9 billion cycles per second. That's a really fast clock. No matter how skilled a clockmaker may be, every pendulum, wind-up mechanism and quartz carystl resonates at a slightly different frequency. However, every cesium 133 atom in the uensivre ollaitescs at the same exact fnrqecuey. So thanks to the atomic clock, we get a time radneig accurate to within 1 billionth of a second, and a very precise measurement of the distance from that satellite. Let's ignore the fact that you're almost definitely on Earth. We now know that you're at a fiexd distance from the slttealie. In other wdors, you're somewhere on the surface of a sphere centered around the satellite. Measure your dctisane from a second satellite and you get another overlapping shepre. Keep doing that, and with just four measurements, and a little correction using Einstein's tehory of relativity, you can pinpoint your ltoicoan to exactly one point in space. So that's all it takes: a multibillion-dollar network of satellites, oscillating ciusem atoms, quantum mechanics, relativity, a smartphone, and you. No problem.

Open Cloze

How does your smartphone know exactly where you are? The answer lies 12,000 miles over your head in an orbiting satellite that keeps time to the beat of an ______ clock powered by quantum mechanics. Phew. Let's break that down. First of all, why is it so important to know what time it is on a satellite when location is what we're _________ about? The first thing your phone needs to determine is how far it is from a satellite. Each satellite constantly broadcasts _____ signals that travel from space to your phone at the _____ of light. Your phone records the signal arrival time and uses it to calculate the distance to the satellite using the simple formula, distance = c x time, where c is the speed of light and time is how long the signal traveled. But there's a problem. _____ is incredibly fast. If we were only able to calculate time to the nearest second, every location on Earth, and far beyond, would seem to be the same distance from the satellite. So in _____ to calculate that distance to within a few dozen feet, we need the best clock ever invented. Enter atomic clocks, some of which are so precise that they would not gain or lose a second even if they ran for the next 300 _______ years. Atomic clocks work because of quantum physics. All clocks must have a constant frequency. In other words, a clock must carry out some repetitive action to mark off equivalent increments of time. Just as a grandfather clock relies on the ________ swinging back and forth of a pendulum under _______, the tick tock of an atomic clock is maintained by the transition between two energy levels of an atom. This is where quantum _______ comes into play. Quantum mechanics says that _____ carry energy, but they can't take on just any arbitrary ______. Instead, atomic ______ is constrained to a precise set of levels. We call these quanta. As a simple analogy, think about driving a car onto a freeway. As you increase your speed, you would normally continuously go from, say, 20 miles/hour up to 70 miles/hour. Now, if you had a quantum atomic car, you wouldn't accelerate in a ______ fashion. Instead, you would instantaneously jump, or transition, from one speed to the next. For an atom, when a transition occurs from one energy level to another, quantum mechanics says that the energy difference is equal to a characteristic frequency, __________ by a constant, where the change in energy is _____ to a number, called Planck's constant, times the frequency. That characteristic frequency is what we need to make our clock. GPS satellites rely on cesium and rubidium atoms as frequency standards. In the case of cesium 133, the characteristic _____ frequency is 9,192,631,770 Hz. That's 9 billion cycles per second. That's a really fast clock. No matter how skilled a clockmaker may be, every pendulum, wind-up mechanism and quartz _______ resonates at a slightly different frequency. However, every cesium 133 atom in the ________ __________ at the same exact _________. So thanks to the atomic clock, we get a time _______ accurate to within 1 billionth of a second, and a very precise measurement of the distance from that satellite. Let's ignore the fact that you're almost definitely on Earth. We now know that you're at a _____ distance from the _________. In other _____, you're somewhere on the surface of a sphere centered around the satellite. Measure your ________ from a second satellite and you get another overlapping ______. Keep doing that, and with just four measurements, and a little correction using Einstein's ______ of relativity, you can pinpoint your ________ to exactly one point in space. So that's all it takes: a multibillion-dollar network of satellites, oscillating ______ atoms, quantum mechanics, relativity, a smartphone, and you. No problem.

Solution

crystal
speed
linear
universe
atoms
atomic
million
order
gravity
energy
multiplied
satellite
sphere
fixed
physics
words
location
light
distance
oscillates
concerned
theory
amount
constant
frequency
equal
radio
clock
cesium
reading

Original Text

How does your smartphone know exactly where you are? The answer lies 12,000 miles over your head in an orbiting satellite that keeps time to the beat of an atomic clock powered by quantum mechanics. Phew. Let's break that down. First of all, why is it so important to know what time it is on a satellite when location is what we're concerned about? The first thing your phone needs to determine is how far it is from a satellite. Each satellite constantly broadcasts radio signals that travel from space to your phone at the speed of light. Your phone records the signal arrival time and uses it to calculate the distance to the satellite using the simple formula, distance = c x time, where c is the speed of light and time is how long the signal traveled. But there's a problem. Light is incredibly fast. If we were only able to calculate time to the nearest second, every location on Earth, and far beyond, would seem to be the same distance from the satellite. So in order to calculate that distance to within a few dozen feet, we need the best clock ever invented. Enter atomic clocks, some of which are so precise that they would not gain or lose a second even if they ran for the next 300 million years. Atomic clocks work because of quantum physics. All clocks must have a constant frequency. In other words, a clock must carry out some repetitive action to mark off equivalent increments of time. Just as a grandfather clock relies on the constant swinging back and forth of a pendulum under gravity, the tick tock of an atomic clock is maintained by the transition between two energy levels of an atom. This is where quantum physics comes into play. Quantum mechanics says that atoms carry energy, but they can't take on just any arbitrary amount. Instead, atomic energy is constrained to a precise set of levels. We call these quanta. As a simple analogy, think about driving a car onto a freeway. As you increase your speed, you would normally continuously go from, say, 20 miles/hour up to 70 miles/hour. Now, if you had a quantum atomic car, you wouldn't accelerate in a linear fashion. Instead, you would instantaneously jump, or transition, from one speed to the next. For an atom, when a transition occurs from one energy level to another, quantum mechanics says that the energy difference is equal to a characteristic frequency, multiplied by a constant, where the change in energy is equal to a number, called Planck's constant, times the frequency. That characteristic frequency is what we need to make our clock. GPS satellites rely on cesium and rubidium atoms as frequency standards. In the case of cesium 133, the characteristic clock frequency is 9,192,631,770 Hz. That's 9 billion cycles per second. That's a really fast clock. No matter how skilled a clockmaker may be, every pendulum, wind-up mechanism and quartz crystal resonates at a slightly different frequency. However, every cesium 133 atom in the universe oscillates at the same exact frequency. So thanks to the atomic clock, we get a time reading accurate to within 1 billionth of a second, and a very precise measurement of the distance from that satellite. Let's ignore the fact that you're almost definitely on Earth. We now know that you're at a fixed distance from the satellite. In other words, you're somewhere on the surface of a sphere centered around the satellite. Measure your distance from a second satellite and you get another overlapping sphere. Keep doing that, and with just four measurements, and a little correction using Einstein's theory of relativity, you can pinpoint your location to exactly one point in space. So that's all it takes: a multibillion-dollar network of satellites, oscillating cesium atoms, quantum mechanics, relativity, a smartphone, and you. No problem.

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
quantum mechanics	3
atomic clock	2
quantum physics	2

Important Words

accelerate
accurate
action
amount
analogy
answer
arbitrary
arrival
atom
atomic
atoms
beat
billion
billionth
break
broadcasts
calculate
call
called
car
carry
case
centered
cesium
change
characteristic
clock
clockmaker
clocks
concerned
constant
constantly
constrained
continuously
correction
crystal
cycles
determine
difference
distance
dozen
driving
earth
energy
enter
equal
equivalent
exact
fact
fashion
fast
feet
fixed
formula
freeway
frequency
gain
gps
grandfather
gravity
head
hz
ignore
important
increase
incredibly
increments
instantaneously
invented
jump
level
levels
lies
light
linear
location
long
lose
maintained
mark
matter
measure
measurement
measurements
mechanics
mechanism
miles
million
multiplied
nearest
network
number
occurs
orbiting
order
oscillates
oscillating
overlapping
pendulum
phew
phone
physics
pinpoint
play
point
powered
precise
problem
quanta
quantum
quartz
radio
ran
reading
records
relativity
relies
rely
repetitive
resonates
rubidium
satellite
satellites
set
signal
signals
simple
skilled
slightly
smartphone
space
speed
sphere
standards
surface
swinging
theory
tick
time
times
tock
transition
travel
traveled
universe
words
work
years