Prática de Shadowing: Can You Keep Zooming In Infinitely? - Aprenda a falar inglês com vídeo
Criando lição...
1
This is a tiny piece of metal just three millimeters across, and here's what happens if you just keep zooming in.
2
A thousand times...
3
A hundred thousand times...
4
50 million times.
5
Each of these blobs is an actual atom.
6
- I saw this the other day at the University of Sydney, and it kind of blew my mind, because up until just 30 years ago, directly seeing atoms like this was thought to be impossible.
7
The rooms that you're going to see here are perhaps the most shielded rooms on campus, or even in the whole of Sydney, I would say.
8
And perhaps also the most expensive.
9
That's wild.
10
So why is it so hard to see atoms?
11
Well, you can't actually see atoms with visible light.
12
That's because while light has wavelengths between 380 and 750 nanometers, an atom is still over 3 ,000 times smaller, just 0 .1 nanometers.
13
much bigger than the thing you're trying to see, the light will just diffract or bend around it, so you won't be able to see it.
14
So if you want to see atoms, you need something with a much, much smaller wavelength.
15
The best candidate isn't even light.
16
It's electrons.
17
In 1924, a French physicist named Louis de Broly worked out that everything was sort of wave -like.
18
Not just light, but matter too.
19
Atoms, molecules, even you yourself have a wavelength.
20
And the formula for this wavelength is Planck's constant divided by the object's momentum, that is, mass times velocity.
21
So here what you actually see, that's the column of the microscope where we accelerate the 300 kV electrons down.
22
300 kilovolts, these electrons.
23
Yes.
24
So they are relativistic particles.
25
How fast are they moving?
26
99 % the speed of light or...?
27
Well, around 80.
28
80 % the speed of light.
29
Yes.
30
So what would be their wavelength?
31
The wavelength is the Planck constant over the momentum, right?
32
So if we calculate that we come to around...
33
between 2 to 3 picometers.
34
Whoa.
35
That's over 100 ,000 times smaller than visible light, so theoretically, you get 100 ,000 times more resolution.
36
Shortly after de Broglie's discovery, a group of scientists in Germany started working on a microscope that would use these high -speed electrons.
37
The only problem is you can't bend electrons using glass lenses.
38
So how do you focus them?
39
Hans Busch, a German physicist, suggested that an electromagnetic lens might do the trick.
40
He published his results in 1926, but never actually built one.
41
Fortunately, a copy of his paper fell into the hands of an eager young PhD student, Ernst Ruska.
42
Ruska built his first prototype by coiling up some wire and surrounding it with iron, taking care to leave a gap in the middle.
43
Then when he passed a current through the coil, it induced a donut -shaped magnetic field through the metal and across this gap.
44
This was his lens.
45
To test it, Ruska first boiled electrons off a tungsten filament, the same kind of filament you'd find in an incandescent light bulb.
46
He accelerated these free electrons through a positively charged anode down to his electromagnetic lens.
47
As an electron approaches the lens, the magnetic field exerts a force on it.
48
So if an electron is traveling in the y direction, the magnetic fields are in the x direction, this force, called the Lorentz force,
49
pushes other magnetic field lines along the donut shape,
50
which constantly point its motion in a circle.
51
But then this circular motion means the Lorentz force starts pushing the electron inwards as well, spiraling it into the center of the lens.
52
Now if you trace the path of the whole beam of electrons, you'll see they all get steered into the center, focusing the beam.
53
By 1931, Ruska and his colleague Max Noll used this kind of design to build the first working electron microscope.
54
It was pretty basic, made of brass roughly bolted together.
55
But it worked.
56
The image itself was created once the focused electron beam hit a sample sitting at the focal point.
57
The sample needed to be incredibly thin, only around 100 nanometers thick.
58
More electrons would make it through the thinner parts of the sample than the thicker parts, creating an electron imprint of the sample.
59
Then, a second electromagnetic lens magnified this imprint down onto a fluorescent detector, producing the final image.
60
This was known as a transmission electron microscope, or TEM.
61
Now, early versions of the microscope barely magnified at all.
62
In fact, it wasn't even better than an optical microscope.
63
But Ruska was determined.
64
Over the next few years, he experimented with adding more lenses onto the microscope to create bigger and bigger images.
65
By the mid -1930s, Ruska had gotten the TEM way past 10 ,000 times magnification.
66
It could produce close -ups of insects, bacteria, and even viruses, at a level far surpassing the optical microscope.
67
But right as Reska's TEM was taking off, a German physicist named Otto Scherzer published a paper, claiming that the microscope was about to hit a brick wall.
68
"There was a flaw in the electromagnetic lens," he wrote,
69
"that was completely unavoidable." For an electron to make it to the focus of the lens, it needs to be deflected by a specific amount.
70
If you simplify its trajectory, you can define that ideal deflection with this angle theta.
71
This angle depends on the horizontal distance of the electron from the optical axis, and how far down the axis the focus is, also known as the focal length.
72
The shorter the focal length, the stronger the magnification.
73
If you graph this angle as a function of distance to the optical axis, you'll see that it can be approximated as linear.
74
The problem is that the magnetic field doesn't scale linearly.
75
It's much stronger near the edges of the magnet.
76
So if you plot the curve for the actual deflection of the electrons, you'll see that the magnetic field over deflects the electrons further out.
77
Their angles are bigger than they should be, so they end up focusing before the rays in the middle.
78
And as a result, the focus is spread across the optical axis instead of being contained in a single point.
79
The blur starts out around the edges of the image, but it gets worse the higher the magnification.
80
This is called spherical aberration and it distorts every radially symmetric magnetic lens.
81
In fact, it doesn't just affect magnetic lenses.
82
Every spherical lens from a camera to a telescope to a magnifying glass also suffers from it.
83
But there is a surprisingly simple way to minimize spherical aberration.
84
Just add a second lens, one that diverges light instead of converging it.
85
Now a diverging lens also suffers from spherical aberration, but if it has the same amount of aberration as your converging lens,
86
just in reverse, the two to essentially cancel out their effects, and that removes the aberrations almost entirely.
87
Almost all modern lens systems in cameras and microscopes use some sort of correcting divergent lens.
88
So you might imagine that the TEM simply needs its own version of a diverging spherical lens to magnify further,
89
but with magnets, this is physically impossible.
90
Every magnet has two poles, a north and a south.
91
It's impossible to just have one.
92
Even if you split a magnet down the middle, it creates two smaller magnets, both with a north and a south.
93
And all magnetic field lines have to start at one pole and end at the other, forming a closed loop.
94
is a direct result of the second Maxwell equation, because the field that you create has field lines that start and end at the same magnet.
95
So the electrons will always cross through.
96
Two lights.
97
The first time it passes through by the Lawrence Falls, it's brought into the spiraling motion and then the second time,
98
from that spiraling motion, which has then a slightly different direction, it's pushed towards the axis.
99
That's why all electromagnetic lenses.
100
By default, will converge the beam and never diverge it.
101
Even if you shot electrons in from the other side of the lens, they would still get focused.
102
This is what Otto Scherzer's paper proved in 1936,
103
stopping progress on the TEM: it is impossible to produce a radially symmetric magnetic lens that diverges.
104
And this was of course a big roadblock for the development of electron microscopy, because people saw: "Okay, we can accelerate electrons as much as we want.
105
The presence of the spherical aberration will always be in the way." Because of this roadblock, advancements in the microscope's resolution slowed significantly.
106
By 1955, another microscope beat the TEM to the punch, and took the first generally accepted image of atoms.
107
This was called the field ion microscope, and it worked by shooting helium or neon atoms at an atomically sharp needle tip.
108
The tip was positively charged, so when the gas atoms hit the needle, they got ionized and were ejected off perpendicular to the surface.
109
And that could form an impression of the atomic structure of the tip.
110
But this method was limited.
111
You could only get a sense of the atomic structure of the very tip of the needle, and the images weren't all that impressive.
112
Luckily, Ruska's electron microscope wouldn't stay stuck in the realm of insects and bacteria forever.
113
Now, you might not be an insect getting bombarded with relativistic electrons, but it can sometimes feel like it when you're getting bombarded with spam calls and targeted ads.
114
It's a real problem when we're researching for our videos.
115
I was reading up on lenses and optics, and a few days later I started getting targeted ads for glasses and eye surgery.
116
So, someone out there is probably selling my browsing data.
117
But this is where today's sponsor Incogni comes in.
118
on your behalf by finding out who has your data, which laws apply, and then they request with the appropriate legal language your information be deleted.
119
You just sign up and they'll give you a list of all the companies that have your information, how severe each claim is, and the status of all your requests.
120
Now I signed up last April and since then they've filed 317 requests for me, 281 of which have been completed, saving me over 210 hours of work.
121
And now I'm no longer getting ads for and fight against the data brokers, visit incogni .com /veritasium.
122
You can also click the link in the description or scan this QR code.
123
Make sure to use code VERITASIUM to get 60 % off your annual subscription to take control of your data today.
124
That's incogni .com /veritasium.
125
And now back to the electron microscope.
126
Despite Scherzer's aberration limit, work on the transmission electron microscope continued.
127
During the next four decades, people tried boosting the resolution with clever workarounds, and perhaps none more so than British American physicist Albert Crewe.
128
His idea was to replace the tungsten filament, which fired off electrons at random, with a more directed source.
129
So instead of boiling electrons off the surface, he tried pulling them off with a stronger electric field.
130
And by sharpening the tungsten into a fine tip, he was able to create a narrow beam which was over a thousand times brighter than before.
131
He paired his new narrow beam with an unlikely technology.
132
The cathode ray tube TV.
133
These TVs worked by scanning an electron beam across a screen.
134
The screen was coated in a phosphor that produced light when hit by electrons.
135
And by varying the intensity of the electron beam, you could vary the brightness of the screen, giving you a black and white image.
136
Crew was inspired to design a similar electron beam for the TEM that would scan across the nanoscopic sample.
137
So instead of creating an imprint of the whole sample at once, Crew's electron beam made smaller imprints, mapping the sample out bit by bit.
138
This wasn't the first time someone had tried to make a scanning version of the TEM.
139
German researcher Manfred von Arden built an early prototype in the 1930s.
140
But it was destroyed during World War II.
141
When Crewe revived Arden's design, he made several drastic improvements,
142
and by 1970, he had this: the first image of single atoms taken with the electron microscope.
143
Researchers quickly jumped to employ his tech, producing countless images of atoms.
144
After nearly a century of improvements from Ruska,
145
Crew, and many others, the magnification upgrades on the TEM had reached their peak. But Scherzer's problem persisted.
146
Spherical aberrations set a hard limit on how small you could see.
147
Even Crew himself gave up on trying to get around it after over ten years of work.
148
Unfortunately, we could never make it work.
149
After many heartbreaking attempts, we were forced to admit defeat.
150
Around this time, other microscopes emerged that could also image atoms.
151
These probe microscopes work by gliding an incredibly small stylus across the sample.
152
The stylus detects variations in quantum effects or nanoscale forces to then map the surface structure of the sample.
153
These were easier to build, and because they didn't use any lenses, they weren't limited by spherical aberration.
154
Their images were even 3D.
155
But the looming issue was that these probes weren't really seeing atoms.
156
It was more like feeling atoms.
157
Throughout the 80s and 90s, this was all we had.
158
But what if there was another way?
159
Schurzer's theorem proved that a diverging radially symmetric lens isn't possible.
160
But if you're willing to give up on that symmetry, the theorem no longer applies.
161
The problem is that radial symmetry is arguably the most important property of any lens, because if you break the symmetry, you also break the image.
162
But three maverick scientists thought there might be a way.
163
Newt Urban, Max Hader, and Harold Rose were known in the electron microscope community as troublemakers.
164
And for years, barely anyone had been interested in their research.
165
or more importantly, in funding it.
166
And for a good reason too.
167
Their idea was kind of crazy.
168
I mean, they purposefully wanted to break the image using a lens that wasn't symmetric.
169
Their hope was that there would be a small part of this distorted image that would be slightly diverging,
170
and maybe Just maybe this small part could correct the spherical aberration of the original lens.
171
So they got to work.
172
To distort the image, they used a massive nest of electromagnets with six, eight, or even ten separate coils and magnets with bumpy magnetic fields.
173
These were known as the hexapole, octapole, and decapole magnets.
174
So as the electron beam passed through a hexapole, it would twist and squeeze the flat 2D image into a triangular saddle.
175
and the circumference of the original beam would be pushed into the three corners, with the rest of the interior stretched out.
176
But now, the middle of the image would have a slight concave bow, giving the effect of a small divergence.
177
Then Rose, Hayter, and Urban forced the beam through a second hexapole, one that worked the opposite way, so it would unbend the distorted image back into a circular shape.
178
But now, they calculated, this new image might have the remnants of that tiny divergence still in its center, with spherical aberration pointing in the opposite way.
179
So if they got their maths and engineering exactly right, they could feed an image with spherical aberration through these two lenses to almost completely counteract the effect.
180
And I imagine a lot of people in the field thought it was a crazy idea when it was proposed, right?
181
Not only the concept, but that this is like technical feasible, I believe.
182
It was thought that this is not possible.
183
By May 1997, the group had just two months of development time left before their last sponsor withdrew their backing.
184
And to make matters worse, their latest lens iteration was still just on the drawing board.
185
But somehow by the 23rd of July, just a week before their funding ran out, the new lens was ready to test.
186
They gingerly placed it into the microscope, but like every time before it, the lens was unstable and failed.
187
So they decided to switch off the equipment for 24 hours the magnets to settle.
188
And then, at 2 AM on the 24th, They turned it on again.
189
And almost magically, the picture started to stabilize.
190
- I'm sorry.
191
Suddenly, there was no aberration.
192
only beautiful, clear images of atoms.
193
After more than 60 years of failed attempts, Urban, Rose, and Hayter pulled off the seemingly impossible.
194
With this method, they cut the resolution of the TEM down to only 0 .13 nanometers.
195
an average TEM image went from looking like this to this.
196
A few months after the group's breakthrough, Newt Urban attended a microscopy conference to share these results.
197
But because of the group's reputation, he was relegated to a small back room that barely anyone noticed.
198
- Thank you.
199
Soon, however, word spread that against all odds his pictures seemed real.
200
Then a crowd of hundreds formed.
201
People were lining up outside, hoping to get a glimpse of their stunningly sharp images.
202
So we're gonna get a sample holder.
203
Yes, now we get a sample holder out.
204
We put that under the optical microscope.
205
So the sample itself is a small lamella that you can't see without the optical microscope.
206
Here, have a look through that.
207
Beautiful.
208
On top of the B there's a prong.
209
Yeah.
210
And on the very top of that, on the left hand side, looks like a little bit of dust.
211
That's our actual sample.
212
Okay, now I simply go up with the magnification.
213
and I do a very few, like, more basic alignments.
214
In this electron microscope, because it's called transmission electron microscope, the electrons always transmit the sample.
215
Here we look through our entire sample at the same time.
216
And that's why it's so important that we align the sample.
217
If you imagine atoms in a high -symmetry direction are lined up like pearls on a string, when we look down it, well, we can see an image.
218
But if we are in some random direction, then everything would be just blurred.
219
So that's why we have to do some tilting in the end.
220
And this is where the actual sample starts, the strontium titanate.
221
And this is the thin region where we hope to get atomic resolution.
222
So this is 5 ,000 times?
223
Yes.
224
Wow and we see strontium, titanium, we see oxygen, We see carbon, that's contamination, so most likely what we're looking at here is carbon contamination.
225
When you do this focus, what are you really looking for?
226
I look for this edge to become sharp.
227
- Bye.
228
Seattle's what?
229
Just like that.
230
That's wild.
231
Shortly after the group successfully corrected the aberrations in the TEM,
232
Andrei Krivanek independently achieved the same for Crew's version of the microscope, the scanning TEM.
233
And in 2020, all four were awarded the prestigious Kavli Prize in nanoscience for accomplishing what so many others thought impossible.
234
Through their persistence and ingenuity, seeing atoms like this is...
235
Well, normal.
236
How big of a difference does aberration correction make?
237
If you want to see atoms, and if you want to, for example, measure interatomic distances, and if you want to learn what type of atoms you have.
238
you need aberration correction.
239
Any research that's materials science, materials engineering, chemical engineering, you will need to see what's happening at the atomic level
240
because you want to relate the properties to the structure.
241
If you can't see the structure at the atomic level, you only have half of the information.
242
So that was a game changer.
243
That's why nowadays every university in principle needs a microscope like that.
📺 Mesmo canal
C11
Something is jamming GPS over Europe. Here's what we found
IELTS PrepTOEFL PrepUniversity Students
C11
The Absurd Engineering Behind the Internet
IELTS PrepTOEFL PrepUniversity Students
C11
Why It Was Almost Impossible to Make the Blue LED
Business EnglishUniversity StudentsWorking Adults
C12
You've (Likely) Been Playing The Game Of Life Wrong
Business EnglishUniversity StudentsWorking Adults
B22
We're trying something new...
Business EnglishUniversity StudentsWorking Adults
C120
How does light 'know' the shortest path?
IELTS PrepTOEFL PrepUniversity Students
C12
The CIA's new tech doesn't make sense
IELTS PrepTOEFL PrepUniversity Students
C11
Why does every mammal get 1 billion heartbeats in their life?
IELTS PrepTOEFL PrepUniversity Students
C13
Why Cold Drinks Were Deadly Before 1914
Business EnglishUniversity StudentsWorking Adults
C14
Exposing The Flaw In Our Phone System
Business EnglishUniversity StudentsWorking Adults
C12
Our Greatest Delusion
IELTS PrepTOEFL PrepUniversity Students
C13
The Most Controversial Problem in Philosophy
IELTS PrepTOEFL PrepUniversity Students
B25
Why Boredom is Good For You
Daily ConversationUniversity StudentsWorking Adults
B24
Why Are 96,000,000 Black Balls on This Reservoir?
IELTS PrepTOEFL PrepUniversity Students
C13
We've Been Using The Wrong Science In Court For 50 years
IELTS PrepTOEFL PrepUniversity Students
B24
Explaining Pi With Pizza
University Students
B214
5 Fun Physics Phenomena
Daily ConversationUniversity Students
C11
The Most Misunderstood Concept in Physics
IELTS PrepTOEFL PrepUniversity Students
B11
Falling ladders - why does this happen?
IELTS PrepTOEFL PrepHigh School Students
C110
How a slinky falls in slow motion #shorts
University StudentsWorking Adults
✨ Vídeo recomendado
C13
80 frases
FINALLY: A Proof that Particles Take All Paths At Once?
IELTS PrepTOEFL PrepUniversity Students
C11
27 frases
ATOMS ENGLISH
IELTS PrepTOEFL PrepUniversity Students
C14
39 frases
Why Walls STOP Light Waves But Not Radio Waves?
IELTS PrepTOEFL PrepUniversity Students
C15
101 frases
The Most Extreme Explosion in the Universe
IELTS PrepTOEFL PrepUniversity Students
C115
43 frases
Candy Corn In Space
IELTS PrepTOEFL PrepUniversity Students
C167
66 frases
What science can’t answer, according to physicist Jim Al-Khalili | Big Think
IELTS PrepTOEFL PrepUniversity Students
C11
146 frases
The Most Complex Language in the World
IELTS PrepTOEFL PrepUniversity Students
C212
105 frases
2 The Principle of the Electron Microscope
IELTS PrepTOEFL PrepUniversity Students
C16
73 frases
Superfluid Dark Matter
IELTS PrepTOEFL PrepUniversity Students
C16
104 frases
How real are the real numbers, really?
IELTS PrepTOEFL PrepUniversity Students
C12
171 frases
The Most Important Picture in the History of Science
American AccentIELTS PrepTOEFL PrepUniversity Students
Contexto & Antecedentes
No vídeo "Can You Keep Zooming In Infinitely?", o apresentador explora a fascinante descoberta do mundo atômico e como a tecnologia nos permite ver átomos pela primeira vez. Ele relata sua experiência na Universidade de Sydney, onde observa uma demonstração incrível sobre a possibilidade de ampliar objetos infinitamente, revelando detalhes que antes eram inimagináveis. O vídeo não apenas destaca a ciência por trás da observação dos átomos, mas também a evolução dos instrumentos que tornaram isso possível, como o microscópio eletrônico. Para os alunos de inglês, essa é uma oportunidade de aprimorar a compreensão auditiva e expandir o vocabulário técnico enquanto descobrem conceitos científicos.
As 5 Principais Frases para Comunicação Diária
- This is a tiny piece of metal just three millimeters across. - Esta é uma pequena peça de metal que mede apenas três milímetros.
- Each of these blobs is an actual atom. - Cada uma dessas manchas é um átomo real.
- Why is it so hard to see atoms? - Por que é tão difícil ver átomos?
- You need something with a much, much smaller wavelength. - Você precisa de algo com um comprimento de onda muito, muito menor.
- This was his lens. - Esta foi a lente dele.
Guia Passo a Passo de Shadowing
A técnica de shadowing é extremamente útil para melhorar suas habilidades orais em inglês. Aqui está um guia passo a passo sobre como aplicar o shadowing em inglês com o vídeo:
- Escolha um trecho curto: Selecione uma seção do vídeo que você acha interessante e envolvente.
- Ouça atentamente: Escute a pronúncia, entonação e ritmo do apresentador. Anote qualquer palavra nova.
- Imite: Reproduza o que você ouviu, tentando igualar a pronúncia e a entonação. Use a técnica de shadowspeak para acompanhar o orador.
- Pratique repetidamente: Escute o trecho várias vezes, cada vez focando em aspectos diferentes, como a clareza da voz e a fluência.
- Grave-se: Use seu celular ou um gravador para registrar sua voz enquanto pratica. Comparar sua gravação com a original pode oferecer insights valiosos.
Utilizando essa estratégia no shadowing site, você não apenas melhorará sua pronúncia, mas também ganhará confiança ao se comunicar em inglês. Aproveite os recursos do YouTube para aprender inglês com youtube e transforme seu aprendizado em uma experiência enriquecedora.
Gramática neste vídeo
As estruturas que o falante mais usa, com as palavras exatas do vídeo:
| Estrutura | No vídeo |
|---|---|
| Voz passiva be + particípio passado — o foco está no que acontece, não em quem faz | was thought · was created · was known |
| Orações relativas who / which + oração — informação extra sobre uma pessoa ou coisa | motion, which has · beam which was |
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.