TedTest

From the Ted Talk by Kanawat Senanan: How do hard drives work?

Unscramble the Blue Letters

ingiame an airplane flying one millimeter above the ground and circling the Earth once every 25 seconds while counting every blade of gasrs. Shrink all that down so that it fits in the palm of your hand, and you'd have something equivalent to a modern hard dirve, an obcejt that can likely hold more information than your lcaol library. So how does it store so much information in such a small space? At the haert of every hard drive is a satck of high-speed spinning discs with a recording head flying over each surface. Each disc is coated with a film of mpiciscoroc magnetised metal grains, and your data doesn't live there in a form you can rzngoeice. Instead, it is recorded as a meatingc pattern fmoerd by groups of those tiny grains. In each group, also known as a bit, all of the grains have their magnetization's aligned in one of two possible states, which crponeorsd to zeroes and ones. Data is wittren onto the disc by converting strings of bits into electrical current fed through an enloeceargtmt. This magnet generates a field strong enough to cgnahe the direction of the metal grain's magnetization. Once this information is written onto the disc, the drive uses a magnetic reader to turn it back into a useful form, much like a phonograph needle tslnaretas a record's grooves into music. But how can you get so much information out of just zeeros and ones? Well, by putting lots of them together. For example, a letter is represented in one byte, or eight bits, and your average photo tkeas up several megabytes, each of which is 8 million bits. Because each bit must be written onto a physical area of the disc, we're always seeking to increase the disc's areal dnietsy, or how many bits can be squeezed into one square inch. The aeral density of a modern hard drive is about 600 gigabits per square inch, 300 million times gaeetrr than that of IBM's first hard drive from 1957. This amazing advance in storage capacity wasn't just a matter of making everything smaller, but inoevvld multiple ianvnotoins. A technique called the thin film lithography percoss aowlled engineers to shrnik the reader and writer. And despite its size, the reader became more sensitive by taking advantage of new discoveries in magnetic and quantum properties of matter. Bits could also be packed colser together thanks to mathematical agriohtlms that flteir out noise from magnetic interference, and find the most likely bit sequences from each chunk of read-back signal. And thermal expansion control of the head, enabled by plcniag a heater under the magnetic writer, allowed it to fly less than five nanometers above the disc's surface, about the width of two strands of DNA. For the past several decades, the einoxapentl growth in cotuepmr storage capacity and processing power has followed a pattern known as Moore's Law, which, in 1975, pdetcried that inrtomifoan density would double every two years. But at around 100 gigabits per square inch, shrinking the magnetic grains further or cramming them closer together posed a new risk called the superparamagnetic effect. When a magnetic grain volume is too small, its magnetization is easily disturbed by heat energy and can cause bits to switch unintentionally, leading to data loss. sncisteits resolved this ltioamiitn in a remarkably simple way: by cgniahng the direction of recording from ladntinuoigl to perpendicular, allowing areal density to approach one terabit per square inch. Recently, the potential limit has been increased yet again through heat assisted magnetic rnodiercg. This uses an even more thermally stable recording medium, whose magnetic resistance is momentarily ruedced by heating up a particular spot with a laser and awnlloig data to be written. And while those drives are currently in the poyrotpte stage, scientists already have the next potential trick up their sleeves: bit-patterned meida, where bit locations are arranged in separate, nano-sized structures, potentially allowing for areal densities of twetny terabits per square inch or more. So it's thanks to the combined efforts of generations of engineers, material scientists, and quantum physicists that this tool of incredible power and precision can spin in the palm of your hand.

Open Cloze

_______ an airplane flying one millimeter above the ground and circling the Earth once every 25 seconds while counting every blade of _____. Shrink all that down so that it fits in the palm of your hand, and you'd have something equivalent to a modern hard _____, an ______ that can likely hold more information than your _____ library. So how does it store so much information in such a small space? At the _____ of every hard drive is a _____ of high-speed spinning discs with a recording head flying over each surface. Each disc is coated with a film of ___________ magnetised metal grains, and your data doesn't live there in a form you can _________. Instead, it is recorded as a ________ pattern ______ by groups of those tiny grains. In each group, also known as a bit, all of the grains have their magnetization's aligned in one of two possible states, which __________ to zeroes and ones. Data is _______ onto the disc by converting strings of bits into electrical current fed through an _____________. This magnet generates a field strong enough to ______ the direction of the metal grain's magnetization. Once this information is written onto the disc, the drive uses a magnetic reader to turn it back into a useful form, much like a phonograph needle __________ a record's grooves into music. But how can you get so much information out of just ______ and ones? Well, by putting lots of them together. For example, a letter is represented in one byte, or eight bits, and your average photo _____ up several megabytes, each of which is 8 million bits. Because each bit must be written onto a physical area of the disc, we're always seeking to increase the disc's areal _______, or how many bits can be squeezed into one square inch. The _____ density of a modern hard drive is about 600 gigabits per square inch, 300 million times _______ than that of IBM's first hard drive from 1957. This amazing advance in storage capacity wasn't just a matter of making everything smaller, but ________ multiple ___________. A technique called the thin film lithography _______ _______ engineers to ______ the reader and writer. And despite its size, the reader became more sensitive by taking advantage of new discoveries in magnetic and quantum properties of matter. Bits could also be packed ______ together thanks to mathematical __________ that ______ out noise from magnetic interference, and find the most likely bit sequences from each chunk of read-back signal. And thermal expansion control of the head, enabled by _______ a heater under the magnetic writer, allowed it to fly less than five nanometers above the disc's surface, about the width of two strands of DNA. For the past several decades, the ___________ growth in ________ storage capacity and processing power has followed a pattern known as Moore's Law, which, in 1975, _________ that ___________ density would double every two years. But at around 100 gigabits per square inch, shrinking the magnetic grains further or cramming them closer together posed a new risk called the superparamagnetic effect. When a magnetic grain volume is too small, its magnetization is easily disturbed by heat energy and can cause bits to switch unintentionally, leading to data loss. __________ resolved this __________ in a remarkably simple way: by ________ the direction of recording from ____________ to perpendicular, allowing areal density to approach one terabit per square inch. Recently, the potential limit has been increased yet again through heat assisted magnetic _________. This uses an even more thermally stable recording medium, whose magnetic resistance is momentarily _______ by heating up a particular spot with a laser and ________ data to be written. And while those drives are currently in the _________ stage, scientists already have the next potential trick up their sleeves: bit-patterned _____, where bit locations are arranged in separate, nano-sized structures, potentially allowing for areal densities of ______ terabits per square inch or more. So it's thanks to the combined efforts of generations of engineers, material scientists, and quantum physicists that this tool of incredible power and precision can spin in the palm of your hand.

Solution

involved
object
grass
limitation
process
filter
longitudinal
drive
areal
recognize
takes
exponential
allowing
microscopic
local
heart
translates
scientists
magnetic
twenty
media
correspond
innovations
zeroes
information
recording
electromagnet
predicted
shrink
changing
closer
formed
written
computer
change
density
prototype
stack
greater
allowed
algorithms
imagine
placing
reduced

Original Text

Imagine an airplane flying one millimeter above the ground and circling the Earth once every 25 seconds while counting every blade of grass. Shrink all that down so that it fits in the palm of your hand, and you'd have something equivalent to a modern hard drive, an object that can likely hold more information than your local library. So how does it store so much information in such a small space? At the heart of every hard drive is a stack of high-speed spinning discs with a recording head flying over each surface. Each disc is coated with a film of microscopic magnetised metal grains, and your data doesn't live there in a form you can recognize. Instead, it is recorded as a magnetic pattern formed by groups of those tiny grains. In each group, also known as a bit, all of the grains have their magnetization's aligned in one of two possible states, which correspond to zeroes and ones. Data is written onto the disc by converting strings of bits into electrical current fed through an electromagnet. This magnet generates a field strong enough to change the direction of the metal grain's magnetization. Once this information is written onto the disc, the drive uses a magnetic reader to turn it back into a useful form, much like a phonograph needle translates a record's grooves into music. But how can you get so much information out of just zeroes and ones? Well, by putting lots of them together. For example, a letter is represented in one byte, or eight bits, and your average photo takes up several megabytes, each of which is 8 million bits. Because each bit must be written onto a physical area of the disc, we're always seeking to increase the disc's areal density, or how many bits can be squeezed into one square inch. The areal density of a modern hard drive is about 600 gigabits per square inch, 300 million times greater than that of IBM's first hard drive from 1957. This amazing advance in storage capacity wasn't just a matter of making everything smaller, but involved multiple innovations. A technique called the thin film lithography process allowed engineers to shrink the reader and writer. And despite its size, the reader became more sensitive by taking advantage of new discoveries in magnetic and quantum properties of matter. Bits could also be packed closer together thanks to mathematical algorithms that filter out noise from magnetic interference, and find the most likely bit sequences from each chunk of read-back signal. And thermal expansion control of the head, enabled by placing a heater under the magnetic writer, allowed it to fly less than five nanometers above the disc's surface, about the width of two strands of DNA. For the past several decades, the exponential growth in computer storage capacity and processing power has followed a pattern known as Moore's Law, which, in 1975, predicted that information density would double every two years. But at around 100 gigabits per square inch, shrinking the magnetic grains further or cramming them closer together posed a new risk called the superparamagnetic effect. When a magnetic grain volume is too small, its magnetization is easily disturbed by heat energy and can cause bits to switch unintentionally, leading to data loss. Scientists resolved this limitation in a remarkably simple way: by changing the direction of recording from longitudinal to perpendicular, allowing areal density to approach one terabit per square inch. Recently, the potential limit has been increased yet again through heat assisted magnetic recording. This uses an even more thermally stable recording medium, whose magnetic resistance is momentarily reduced by heating up a particular spot with a laser and allowing data to be written. And while those drives are currently in the prototype stage, scientists already have the next potential trick up their sleeves: bit-patterned media, where bit locations are arranged in separate, nano-sized structures, potentially allowing for areal densities of twenty terabits per square inch or more. So it's thanks to the combined efforts of generations of engineers, material scientists, and quantum physicists that this tool of incredible power and precision can spin in the palm of your hand.

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
hard drive	3
square inch	3
modern hard	2
areal density	2
storage capacity	2

Important Words

advance
advantage
airplane
algorithms
aligned
allowed
allowing
amazing
approach
area
areal
arranged
assisted
average
bit
bits
blade
byte
called
capacity
change
changing
chunk
circling
closer
coated
combined
computer
control
converting
correspond
counting
cramming
current
data
decades
densities
density
direction
disc
discoveries
discs
disturbed
dna
double
drive
drives
earth
easily
effect
efforts
electrical
electromagnet
enabled
energy
engineers
equivalent
expansion
exponential
fed
field
film
filter
find
fits
fly
flying
form
formed
generates
generations
gigabits
grain
grains
grass
greater
grooves
ground
group
groups
growth
hand
hard
head
heart
heat
heater
heating
hold
imagine
inch
increase
increased
incredible
information
innovations
interference
involved
laser
law
leading
letter
library
limit
limitation
lithography
live
local
locations
longitudinal
loss
lots
magnet
magnetic
magnetised
magnetization
making
material
mathematical
matter
media
medium
megabytes
metal
microscopic
millimeter
million
modern
momentarily
multiple
music
nanometers
needle
noise
object
packed
palm
pattern
perpendicular
phonograph
photo
physical
physicists
placing
posed
potential
potentially
power
precision
predicted
process
processing
properties
prototype
putting
quantum
reader
recognize
recorded
recording
reduced
remarkably
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resistance
resolved
risk
scientists
seconds
seeking
sensitive
separate
sequences
shrink
shrinking
signal
simple
size
small
smaller
space
spin
spinning
spot
square
squeezed
stable
stack
stage
states
storage
store
strands
strings
strong
structures
superparamagnetic
surface
switch
takes
technique
terabit
terabits
thermal
thermally
thin
times
tiny
tool
translates
trick
turn
twenty
unintentionally
volume
width
writer
written
years
zeroes