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 measure its speed if we slow down the animation, we can analyze light's motion using a space-time diagram, which takes a fpoloibk of animation panels, and turns them on their side. In this lesson, we'll add the signle experimental fact that whenever anyone measures just how fast light moves, they get the same answer: 299,792,458 meters every second, which menas 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, chgnae 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 drgiaam. Yes, that means taking all of the different panels showing the different mtnmeos in time and stinakcg 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 adernw 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 sartt again. In the 1900s, a clever chap named Albert Einstein worked out how to see things properly, from Tom's ponit of view, while still getting the speed of light right. First, we need to glue together the separate panels into one silod bolck. This gives us our space-time, turning space and time into one stmooh, 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 vtraceil, so this does represent the wlord 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 corerct 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 lhgit works out to be that same fixed value that we know everyone measures. On the other hand, something srntgae has haepnped. The fence ptoss 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 leortnz 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 lekood 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 erydavey spedes, such as Tom's car reaches, actually all the effects are much, much smaller than we've illustrated them. Oh, yet, careful experiments, for isnactne wanctihg the boeivhar of tiny particles whizzing around the Large Hadron Collider cnmferiod that the effects are real. And now that space-time is an eltamlreinxepy confirmed part of rtealiy, 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.

Open Cloze

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 ________ of animation panels, and turns them on their side. In this lesson, we'll add the ______ experimental fact that whenever anyone measures just how fast light moves, they get the same answer: 299,792,458 meters every second, which _____ 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, ______ 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 _______. Yes, that means taking all of the different panels showing the different _______ in time and ________ 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 ______ 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 _____ again. In the 1900s, a clever chap named Albert Einstein worked out how to see things properly, from Tom's _____ of view, while still getting the speed of light right. First, we need to glue together the separate panels into one _____ _____. This gives us our space-time, turning space and time into one ______, 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 represent 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 _______ 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 _____ works out to be that same fixed value that we know everyone measures. On the other hand, something _______ has ________. The fence _____ 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 _______ 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 ______ 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 ________ ______, such as Tom's car reaches, actually all the effects are much, much smaller than we've illustrated them. Oh, yet, careful experiments, for ________ ________ the ________ of tiny particles whizzing around the Large Hadron Collider _________ that the effects are real. And now that space-time is an ______________ confirmed part of _______, 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.

Solution

behavior
smooth
stacking
block
watching
speeds
experimentally
andrew
correct
lorentz
happened
vertical
single
reality
solid
world
light
posts
start
change
instance
confirmed
strange
looked
point
diagram
means
flipbook
moments
everyday

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
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carefully
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changed
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einstein
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measure
measured
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meter
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moving
muddled
named
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part
particles
perspective
physically
physics
playing
point
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previously
properly
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real
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redraw
represent
represents
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separate
separately
shine
showed
showing
side
single
slice
slow
smaller
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solid
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speaking
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squashing
stacking
stand
start
stationary
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superb
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tiny
tom
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vertical
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watching
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works
world
worried
yeah