If superpowers were real: Invisibility - Joy Lin

1,436,348 views ・ 2013-06-27

TED-Ed


Please double-click on the English subtitles below to play the video.

00:14
Wouldn't it be great if we could be
0
14517
2572
00:17
invisible?
1
17113
1157
00:18
Ha, right?
2
18294
755
00:19
I mean, we could spy on people without being noticed
3
19073
2477
00:21
and do whatever we want
4
21574
1311
00:22
without being held responsible.
5
22909
2596
00:25
Now, magicians have figured out
6
25529
1666
00:27
how to utilize full-sized mirrors to bend light
7
27219
2649
00:29
in order to create disappearing illusions.
8
29892
4642
00:34
Scientists have created metamaterials
9
34558
2356
00:36
to guide rays of light
10
36938
1019
00:37
around tiny, two-dimensional objects.
11
37981
2771
00:40
Cameras can also film what is behind you
12
40776
2229
00:43
and project the image
13
43029
728
00:43
so you appear invisible from the front.
14
43781
3427
00:47
However, none of these options
15
47232
2153
00:49
can make an object as large as a person
16
49409
2169
00:51
appear invisible for all angles and distances
17
51602
2819
00:54
while its moving.
18
54445
1196
00:55
But if you are truly invisible,
19
55665
2103
00:57
as in from within,
20
57792
1899
00:59
here are a few problems
21
59715
1098
01:00
you may not have thought about before.
22
60837
2825
01:03
To move around undetected by other people,
23
63686
2425
01:06
you would have to be totally naked.
24
66135
2899
01:09
Even if it's freezing outside!
25
69058
2637
01:13
You can't carry anything,
26
73034
1425
01:14
including your wallet and keys,
27
74483
1853
01:16
otherwise people would just see
28
76360
2009
01:18
your wallet and keys floating around.
29
78393
1762
01:20
Drivers and people on the street can't see you either,
30
80179
2572
01:22
therefore they can and will run into you at some point.
31
82775
4326
01:27
Oh, and you better not wear any perfume
32
87820
2829
01:30
or make any noise breathing,
33
90673
2172
01:32
otherwise they'll know you're there.
34
92869
3262
01:38
And, just because you start off invisible,
35
98130
2000
01:40
doesn't mean you'll stay that way.
36
100154
1871
01:42
What if someone accidentally spills
37
102049
1755
01:43
scolding hot coffee on you?
38
103828
1892
01:46
And what if it rains?
39
106966
1910
01:50
But if you think only liquid can make you visible,
40
110745
3382
01:54
you're wrong.
41
114151
1185
01:55
Dust consists of dead skin cells from humans,
42
115360
2782
01:58
soil particles,
43
118166
738
01:58
and fibers from clothes made from cotton
44
118928
2240
02:01
and other materials.
45
121192
1555
02:02
Dust sticks to the moisture on our skin when we sweat
46
122771
3197
02:05
and the tiny hairs on our skin when we are dry.
47
125992
2854
02:08
So, even if you are invisible,
48
128870
2268
02:11
dust would still land on every part of you.
49
131162
2439
02:13
We usually don't notice the dust on our skin
50
133625
1936
02:15
because we can't see a thin layer of dust
51
135585
2002
02:17
on top of our skin color.
52
137611
1325
02:18
But, if you're invisible,
53
138960
1313
02:20
people would see a human-shaped blob of dust
54
140297
2640
02:22
walking around with extremely dirty soles.
55
142961
3314
02:27
Gross!
56
147073
1150
02:28
What do you think the world looks like
57
148247
1162
02:29
if you are invisible?
58
149433
820
02:30
Well, the answer is nothing.
59
150277
2782
02:33
The reason you can't see in the dark
60
153083
1715
02:34
is because there is no light.
61
154822
1867
02:36
To see an apple,
62
156713
1153
02:37
light has to hit the apple
63
157890
1010
02:38
and return it to your eyes.
64
158924
1519
02:40
Then, the retinas in your eyes
65
160467
1464
02:41
catch the light reflection for your brain
66
161955
1953
02:43
to interpret into the image of an apple.
67
163932
2557
02:46
If you're invisible,
68
166513
1167
02:47
then, by definition, light would travel
69
167704
2076
02:49
through you or around you
70
169804
2068
02:51
instead of bouncing off you for people to see.
71
171896
2574
02:54
But that means that retinas in your eyes
72
174494
1970
02:56
are not catching the light, either.
73
176488
1808
02:58
Therefore, your brain has nothing
74
178320
1572
02:59
to interpret into an image.
75
179916
1551
03:01
Can you see your reflection
76
181491
1642
03:03
without a mirror to stop the light?
77
183157
1667
03:04
No.
78
184848
823
03:05
So, when you can't be seen by others,
79
185695
2234
03:07
you also cannot see.
80
187953
2729
03:10
Ouch!
81
190706
1308
03:12
Now, have you given any thought
82
192038
1477
03:13
as of whether the invisibility is permanent?
83
193539
2648
03:16
If it is, how can you receive medical treatment
84
196211
2311
03:18
from a doctor if you're injured?
85
198546
1834
03:20
The doctor wouldn't know
86
200404
1081
03:21
where to apply ointments or bandages
87
201509
1927
03:23
because they cannot access your injury.
88
203460
4463
03:27
For that matter, you can't see it either.
89
207947
1545
03:29
I mean, what if you have an illness or an infection?
90
209516
2808
03:32
How can the doctor diagnose you
91
212348
1477
03:33
without being able to see the color change or inflammation?
92
213849
2862
03:36
And what if everyone is permanently invisible?
93
216735
3142
03:39
Well, think about how boring the world would be
94
219901
2239
03:42
without seeing people on the streets,
95
222164
1762
03:43
on TV,
96
223950
351
03:44
or at home on your computer
97
224325
2755
03:47
like right now.
98
227104
1755
03:48
It's lonely being invisible.
99
228883
2407
03:54
Now, which superpower physics lesson
100
234520
2757
03:57
will you explore next?
101
237301
2414
03:59
Shifting body size and content,
102
239739
4068
04:03
super speed,
103
243831
1370
04:05
flight,
104
245225
1404
04:06
super strength,
105
246653
2846
04:09
immortality,
106
249523
2727
04:12
and
107
252274
1861
04:14
invisibility.
108
254159
2584
About this website

This site will introduce you to YouTube videos that are useful for learning English. You will see English lessons taught by top-notch teachers from around the world. Double-click on the English subtitles displayed on each video page to play the video from there. The subtitles scroll in sync with the video playback. If you have any comments or requests, please contact us using this contact form.

https://forms.gle/WvT1wiN1qDtmnspy7