TedTest

From the Ted Talk by Andrew Pontzen and Tom Whyntie: The fundamentals of space-time Part 2

Unscramble the Blue Letters

Light: it's the fastest thing in the universe, but we can still mrsueae its speed if we slow down the aiatnmoin, we can analyze light's moiotn using a space-time diagram, which takes a foolbipk of animation panels, and truns them on their side. In this lesosn, we'll add the single experimental fact that whenever anyone measures just how fast light moves, they get the same answer: 299,792,458 meters every second, which means that when we draw light on our space-time dgaarim, it's world line always has to appear at the same angle. But we saw previously that speed, or equivalently world line algens, change when we look at things from other people's perspective. To explore this contradiction, let's see what happens if I start moving while I stand still and shine the laser at Tom. First, we'll need to construct the space-time diagram. Yes, that means taking all of the different panels showing the different moments in time and stacking them up. From the side, we see the world line of the laser light at its correct fixed angle, just as before. So far, so good. But that space-time diagram represents Andrew's perspective. What does it look like to me? In the last lesson, we showed how to get Tom's peectvrspie moving all the panels along a bit until his world line is completely vertical. But look carefully at the light world line. The rneameernargt of the panels means it's now tlited over too far. I'd measure light traveling faster than Andrew would. But every experiment we've ever done, and we've tried very hard, says that everyone measures light to have a fixed speed. So let's start again. In the 1900s, a clever chap named Albert Einstein wekrod out how to see things properly, from Tom's point of view, while still getting the speed of light right. First, we need to glue together the separate panels into one solid block. This gives us our space-time, tiunnrg space and time into one smooth, continuous material. And now, here is the trick. What you do is stretch your block of space-time along the light world line, then squash it by the same amount, but at right angles to the light world line, and abracadabra! Tom's world line has gone veicatrl, so this does rpresenet the wrlod from his point of view, but most importantly, the light world line has never changed its angle, and so light will be measured by Tom going at the correct speed. This superb trick is known as a lenrtoz transformation. Yeah, more than a trick. Slice up the space-time into new panels and you have the philyaslcy cocerrt animation. I'm stationary in the car, everything else is coming past me and the speed of light works out to be that same fixed value that we know everyone mreeusas. On the other hand, something strange has hnpeepad. The fence posts aren't spaced a meter apart anymore, and my mom will be werorid that I look a bit thin. But that's not fair. Why don't I get to look thin? I thought physics was supposed to be the same for everyone. Yes, no, it is, and you do. All that srhtcntieg and squashing of space-time has just muddled together what we used to think of separately as space and time. This particular squashing effect is known as Lorentz contraction. Okay, but I still don't look thin. No, yes, you do. Now that we know better about space-time, we should redraw what the scnee looked like to me. To you, I appear Lorentz contracted. Oh but to you, I appear Lorentz cratcneotd. Yes. Uh, well, at least it's fair. And speaking of fairness, just as space gets muddled with time, time also gets mludded with scpae, in an effect known as time dilation. No, at everyday speeds, such as Tom's car reaches, actually all the ecftefs are much, much smaller than we've illustrated them. Oh, yet, careful expemtenris, for instance watching the behavior of tiny particles whzniizg around the Large hraodn Collider confirmed that the effects are real. And now that space-time is an experimentally cfromiend part of railety, we can get a bit more amiuboits. What if we were to start playing with the material of space-time itself? We'll find out all about that in the next animation.

Open Cloze

Light: it's the fastest thing in the universe, but we can still _______ its speed if we slow down the _________, we can analyze light's ______ using a space-time diagram, which takes a ________ of animation panels, and _____ them on their side. In this ______, we'll add the single experimental fact that whenever anyone measures just how fast light moves, they get the same answer: 299,792,458 meters every second, which means that when we draw light on our space-time _______, it's world line always has to appear at the same angle. But we saw previously that speed, or equivalently world line ______, change when we look at things from other people's perspective. To explore this contradiction, let's see what happens if I start moving while I stand still and shine the laser at Tom. First, we'll need to construct the space-time diagram. Yes, that means taking all of the different panels showing the different moments in time and stacking them up. From the side, we see the world line of the laser light at its correct fixed angle, just as before. So far, so good. But that space-time diagram represents Andrew's perspective. What does it look like to me? In the last lesson, we showed how to get Tom's ___________ moving all the panels along a bit until his world line is completely vertical. But look carefully at the light world line. The _____________ of the panels means it's now ______ over too far. I'd measure light traveling faster than Andrew would. But every experiment we've ever done, and we've tried very hard, says that everyone measures light to have a fixed speed. So let's start again. In the 1900s, a clever chap named Albert Einstein ______ out how to see things properly, from Tom's point of view, while still getting the speed of light right. First, we need to glue together the separate panels into one solid block. This gives us our space-time, _______ space and time into one smooth, continuous material. And now, here is the trick. What you do is stretch your block of space-time along the light world line, then squash it by the same amount, but at right angles to the light world line, and abracadabra! Tom's world line has gone ________, so this does _________ the _____ from his point of view, but most importantly, the light world line has never changed its angle, and so light will be measured by Tom going at the correct speed. This superb trick is known as a _______ transformation. Yeah, more than a trick. Slice up the space-time into new panels and you have the __________ _______ animation. I'm stationary in the car, everything else is coming past me and the speed of light works out to be that same fixed value that we know everyone ________. On the other hand, something strange has ________. The fence posts aren't spaced a meter apart anymore, and my mom will be _______ that I look a bit thin. But that's not fair. Why don't I get to look thin? I thought physics was supposed to be the same for everyone. Yes, no, it is, and you do. All that __________ and squashing of space-time has just muddled together what we used to think of separately as space and time. This particular squashing effect is known as Lorentz contraction. Okay, but I still don't look thin. No, yes, you do. Now that we know better about space-time, we should redraw what the _____ looked like to me. To you, I appear Lorentz contracted. Oh but to you, I appear Lorentz __________. Yes. Uh, well, at least it's fair. And speaking of fairness, just as space gets muddled with time, time also gets _______ with _____, in an effect known as time dilation. No, at everyday speeds, such as Tom's car reaches, actually all the _______ are much, much smaller than we've illustrated them. Oh, yet, careful ___________, for instance watching the behavior of tiny particles ________ around the Large ______ Collider confirmed that the effects are real. And now that space-time is an experimentally _________ part of _______, we can get a bit more _________. What if we were to start playing with the material of space-time itself? We'll find out all about that in the next animation.

Solution

whizzing
worried
happened
turns
flipbook
lorentz
measure
motion
rearrangement
angles
physically
tilted
confirmed
ambitious
scene
space
correct
worked
perspective
lesson
muddled
vertical
world
stretching
turning
animation
experiments
measures
reality
hadron
contracted
diagram
effects
represent

Original Text

Light: it's the fastest thing in the universe, but we can still measure its speed if we slow down the animation, we can analyze light's motion using a space-time diagram, which takes a flipbook of animation panels, and turns them on their side. In this lesson, we'll add the single experimental fact that whenever anyone measures just how fast light moves, they get the same answer: 299,792,458 meters every second, which means that when we draw light on our space-time diagram, it's world line always has to appear at the same angle. But we saw previously that speed, or equivalently world line angles, change when we look at things from other people's perspective. To explore this contradiction, let's see what happens if I start moving while I stand still and shine the laser at Tom. First, we'll need to construct the space-time diagram. Yes, that means taking all of the different panels showing the different moments in time and stacking them up. From the side, we see the world line of the laser light at its correct fixed angle, just as before. So far, so good. But that space-time diagram represents Andrew's perspective. What does it look like to me? In the last lesson, we showed how to get Tom's perspective moving all the panels along a bit until his world line is completely vertical. But look carefully at the light world line. The rearrangement of the panels means it's now tilted over too far. I'd measure light traveling faster than Andrew would. But every experiment we've ever done, and we've tried very hard, says that everyone measures light to have a fixed speed. So let's start again. In the 1900s, a clever chap named Albert Einstein worked out how to see things properly, from Tom's point of view, while still getting the speed of light right. First, we need to glue together the separate panels into one solid block. This gives us our space-time, turning space and time into one smooth, continuous material. And now, here is the trick. What you do is stretch your block of space-time along the light world line, then squash it by the same amount, but at right angles to the light world line, and abracadabra! Tom's world line has gone vertical, so this does represent the world from his point of view, but most importantly, the light world line has never changed its angle, and so light will be measured by Tom going at the correct speed. This superb trick is known as a Lorentz transformation. Yeah, more than a trick. Slice up the space-time into new panels and you have the physically correct animation. I'm stationary in the car, everything else is coming past me and the speed of light works out to be that same fixed value that we know everyone measures. On the other hand, something strange has happened. The fence posts aren't spaced a meter apart anymore, and my mom will be worried that I look a bit thin. But that's not fair. Why don't I get to look thin? I thought physics was supposed to be the same for everyone. Yes, no, it is, and you do. All that stretching and squashing of space-time has just muddled together what we used to think of separately as space and time. This particular squashing effect is known as Lorentz contraction. Okay, but I still don't look thin. No, yes, you do. Now that we know better about space-time, we should redraw what the scene looked like to me. To you, I appear Lorentz contracted. Oh but to you, I appear Lorentz contracted. Yes. Uh, well, at least it's fair. And speaking of fairness, just as space gets muddled with time, time also gets muddled with space, in an effect known as time dilation. No, at everyday speeds, such as Tom's car reaches, actually all the effects are much, much smaller than we've illustrated them. Oh, yet, careful experiments, for instance watching the behavior of tiny particles whizzing around the Large Hadron Collider confirmed that the effects are real. And now that space-time is an experimentally confirmed part of reality, we can get a bit more ambitious. What if we were to start playing with the material of space-time itself? We'll find out all about that in the next animation.

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
world line	7
light world	4
lorentz contracted	2

ngrams of length 3

collocation	frequency
light world line	2

Important Words

add
albert
ambitious
amount
analyze
andrew
angle
angles
animation
anymore
behavior
bit
block
car
careful
carefully
change
changed
chap
clever
collider
coming
completely
confirmed
construct
continuous
contracted
contraction
contradiction
correct
diagram
dilation
draw
effect
effects
einstein
equivalently
everyday
experiment
experimental
experimentally
experiments
explore
fact
fair
fairness
fast
faster
fastest
fence
find
fixed
flipbook
glue
good
hadron
hand
happened
hard
illustrated
importantly
instance
large
laser
lesson
light
line
looked
lorentz
material
means
measure
measured
measures
meter
meters
mom
moments
motion
moves
moving
muddled
named
panels
part
particles
perspective
physically
physics
playing
point
posts
previously
properly
reaches
real
reality
rearrangement
redraw
represent
represents
scene
separate
separately
shine
showed
showing
side
single
slice
slow
smaller
smooth
solid
space
spaced
speaking
speed
speeds
squash
squashing
stacking
stand
start
stationary
strange
stretch
stretching
superb
supposed
takes
thin
thought
tilted
time
tiny
tom
transformation
traveling
trick
turning
turns
uh
universe
vertical
view
watching
whizzing
worked
works
world
worried
yeah