Luyện nói tiếng Anh bằng Shadowing qua video: Can You Keep Zooming In Infinitely?

This is a tiny piece of metal just three millimeters across, and here's what happens if you just keep zooming in.

A thousand times...

A hundred thousand times...

50 million times.

Each of these blobs is an actual atom.

- 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.

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.

And perhaps also the most expensive.

That's wild.

So why is it so hard to see atoms?

Well, you can't actually see atoms with visible light.

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.

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.

So if you want to see atoms, you need something with a much, much smaller wavelength.

The best candidate isn't even light.

It's electrons.

In 1924, a French physicist named Louis de Broly worked out that everything was sort of wave -like.

Not just light, but matter too.

Atoms, molecules, even you yourself have a wavelength.

And the formula for this wavelength is Planck's constant divided by the object's momentum, that is, mass times velocity.

So here what you actually see, that's the column of the microscope where we accelerate the 300 kV electrons down.

300 kilovolts, these electrons.

Yes.

So they are relativistic particles.

How fast are they moving?

99 % the speed of light or...?

Well, around 80.

80 % the speed of light.

Yes.

So what would be their wavelength?

The wavelength is the Planck constant over the momentum, right?

So if we calculate that we come to around...

between 2 to 3 picometers.

Whoa.

That's over 100 ,000 times smaller than visible light, so theoretically, you get 100 ,000 times more resolution.

Shortly after de Broglie's discovery, a group of scientists in Germany started working on a microscope that would use these high -speed electrons.

The only problem is you can't bend electrons using glass lenses.

So how do you focus them?

Hans Busch, a German physicist, suggested that an electromagnetic lens might do the trick.

He published his results in 1926, but never actually built one.

Fortunately, a copy of his paper fell into the hands of an eager young PhD student, Ernst Ruska.

Ruska built his first prototype by coiling up some wire and surrounding it with iron, taking care to leave a gap in the middle.

Then when he passed a current through the coil, it induced a donut -shaped magnetic field through the metal and across this gap.

This was his lens.

To test it, Ruska first boiled electrons off a tungsten filament, the same kind of filament you'd find in an incandescent light bulb.

He accelerated these free electrons through a positively charged anode down to his electromagnetic lens.

As an electron approaches the lens, the magnetic field exerts a force on it.

So if an electron is traveling in the y direction, the magnetic fields are in the x direction, this force, called the Lorentz force,

pushes other magnetic field lines along the donut shape,

which constantly point its motion in a circle.

But then this circular motion means the Lorentz force starts pushing the electron inwards as well, spiraling it into the center of the lens.

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.

By 1931, Ruska and his colleague Max Noll used this kind of design to build the first working electron microscope.

It was pretty basic, made of brass roughly bolted together.

But it worked.

The image itself was created once the focused electron beam hit a sample sitting at the focal point.

The sample needed to be incredibly thin, only around 100 nanometers thick.

More electrons would make it through the thinner parts of the sample than the thicker parts, creating an electron imprint of the sample.

Then, a second electromagnetic lens magnified this imprint down onto a fluorescent detector, producing the final image.

This was known as a transmission electron microscope, or TEM.

Now, early versions of the microscope barely magnified at all.

In fact, it wasn't even better than an optical microscope.

But Ruska was determined.

Over the next few years, he experimented with adding more lenses onto the microscope to create bigger and bigger images.

By the mid -1930s, Ruska had gotten the TEM way past 10 ,000 times magnification.

It could produce close -ups of insects, bacteria, and even viruses, at a level far surpassing the optical microscope.

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.

"There was a flaw in the electromagnetic lens," he wrote,

"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.

If you simplify its trajectory, you can define that ideal deflection with this angle theta.

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.

The shorter the focal length, the stronger the magnification.

If you graph this angle as a function of distance to the optical axis, you'll see that it can be approximated as linear.

The problem is that the magnetic field doesn't scale linearly.

It's much stronger near the edges of the magnet.

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.

Their angles are bigger than they should be, so they end up focusing before the rays in the middle.

And as a result, the focus is spread across the optical axis instead of being contained in a single point.

The blur starts out around the edges of the image, but it gets worse the higher the magnification.

This is called spherical aberration and it distorts every radially symmetric magnetic lens.

In fact, it doesn't just affect magnetic lenses.

Every spherical lens from a camera to a telescope to a magnifying glass also suffers from it.

But there is a surprisingly simple way to minimize spherical aberration.

Just add a second lens, one that diverges light instead of converging it.

Now a diverging lens also suffers from spherical aberration, but if it has the same amount of aberration as your converging lens,

just in reverse, the two to essentially cancel out their effects, and that removes the aberrations almost entirely.

Almost all modern lens systems in cameras and microscopes use some sort of correcting divergent lens.

So you might imagine that the TEM simply needs its own version of a diverging spherical lens to magnify further,

but with magnets, this is physically impossible.

Every magnet has two poles, a north and a south.

It's impossible to just have one.

Even if you split a magnet down the middle, it creates two smaller magnets, both with a north and a south.

And all magnetic field lines have to start at one pole and end at the other, forming a closed loop.

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.

So the electrons will always cross through.

Two lights.

The first time it passes through by the Lawrence Falls, it's brought into the spiraling motion and then the second time,

from that spiraling motion, which has then a slightly different direction, it's pushed towards the axis.

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.

📺 Cùng kênh

✨ Video gợi ý

80 câu

FINALLY: A Proof that Particles Take All Paths At Once?

IELTS PrepTOEFL PrepUniversity Students

27 câu

ATOMS ENGLISH

IELTS PrepTOEFL PrepUniversity Students

39 câu

Why Walls STOP Light Waves But Not Radio Waves?

IELTS PrepTOEFL PrepUniversity Students

101 câu

The Most Extreme Explosion in the Universe

IELTS PrepTOEFL PrepUniversity Students

530 câu

Human Immortality 4K | Can Science Defeat Aging?

IELTS PrepTOEFL PrepUniversity Students

43 câu

Candy Corn In Space

IELTS PrepTOEFL PrepUniversity Students

105 câu

2 The Principle of the Electron Microscope

IELTS PrepTOEFL PrepUniversity Students

171 câu

The Most Important Picture in the History of Science

IELTS PrepTOEFL PrepUniversity Students

627 câu

Brian Cox - The Most Mysterious Facts About The Universe

IELTS PrepTOEFL PrepUniversity Students

89 câu

Fire in ZERO-G!!

IELTS PrepTOEFL PrepUniversity Students

249 câu

The Speed of Light Isn't a Limit. It's a Converter

IELTS PrepTOEFL PrepUniversity Students

172 câu

How Is a Memory Stored Inside Your Squishy Brain?

IELTS PrepTOEFL PrepUniversity Students

Về Bài Học Này

Bài học này sẽ giúp bạn phát triển khả năng luyện nói tiếng anh qua việc phân tích và thực hành những khái niệm khoa học liên quan đến nguyên tử. Bạn sẽ được tiếp xúc với những thuật ngữ và cách diễn đạt đặc trưng trong lĩnh vực vật lý, qua đó nâng cao khả năng luyện nghe nói qua video và cải thiện phát âm của mình.

Từ Vựng & Cụm Từ Chính

nguyên tử (atom)
tốc độ ánh sáng (speed of light)
kính hiển vi điện tử (electron microscope)
lực Lorentz (Lorentz force)
tần số sóng (wavelength)
khối lượng (mass)
điện tích dương (positively charged)
mẫu (sample)

Mẹo Thực Hành

Khi thực hiện shadowing tiếng anh với video này, bạn nên chú ý đến tốc độ nói của người dẫn. Hãy theo dõi và nhắc lại từng câu cùng với họ, bắt đầu từ những đoạn ngắn và dần dần tăng độ dài. Điều này sẽ giúp bạn cải thiện khả năng phát âm tiếng anh chuẩn và hiểu rõ hơn về ngữ điệu cũng như sự nhấn mạnh trong câu. Đặc biệt, hãy lưu ý cách người dẫn diễn đạt các thuật ngữ khoa học, đảm bảo rằng bạn không chỉ phát âm đúng mà còn hiểu cách sử dụng chúng trong ngữ cảnh.

Bạn cũng có thể thử nghe lại phần video với tốc độ chậm hơn để tập trung vào từng từ một. Sau khi thành thạo, hãy chuyển sang tốc độ bình thường để xem khả năng hiểu và phát âm của bạn đã cải thiện ra sao. Hãy kết hợp những kỹ thuật này với nhau để tối ưu hóa quá trình luyện nghe nói qua video và tận dụng tối đa bài học này.

Ngữ pháp trong video

Những cấu trúc người nói dùng nhiều nhất, kèm đúng cụm từ trong video:

Cấu trúc	Trong video
Câu bị động be + quá khứ phân từ — nhấn vào việc xảy ra, không phải người làm	was thought · was created · was known
Mệnh đề quan hệ who / which + mệnh đề — thêm thông tin về người hoặc vật	motion, which has · beam which was

Phương Pháp Shadowing Là Gì?

Shadowing là kỹ thuật học ngôn ngữ có cơ sở khoa học, ban đầu được phát triển cho chương trình đào tạo phiên dịch viên chuyên nghiệp và được phổ biến rộng rãi bởi nhà đa ngôn ngữ học Dr. Alexander Arguelles. Nguyên lý cốt lõi đơn giản nhưng cực kỳ hiệu quả: bạn nghe tiếng Anh của người bản xứ và lặp lại to ngay lập tức — như một "cái bóng" (shadow) đuổi theo người nói với độ trễ chỉ 1–2 giây. Khác với luyện ngữ pháp hay học từ vựng bị động, Shadowing buộc não bộ và cơ miệng phải đồng thời xử lý và tái tạo ngôn ngữ thực tế. Các nghiên cứu khoa học xác nhận phương pháp này cải thiện đáng kể phát âm, ngữ điệu, nhịp điệu, nối âm, kỹ năng nghe và độ lưu loát khi nói — đặc biệt hiệu quả cho người luyện IELTS Speaking và muốn giao tiếp tiếng Anh tự nhiên như người bản ngữ.

Phương pháp shadowing: đọc hướng dẫn từng bước đầy đủ →

Luyện nói tiếng Anh bằng Shadowing qua video: Can You Keep Zooming In Infinitely?

Something is jamming GPS over Europe. Here's what we found

The Absurd Engineering Behind the Internet

Why It Was Almost Impossible to Make the Blue LED

You've (Likely) Been Playing The Game Of Life Wrong

We're trying something new...

How does light 'know' the shortest path?

The CIA's new tech doesn't make sense

Why does every mammal get 1 billion heartbeats in their life?

Why Cold Drinks Were Deadly Before 1914

Exposing The Flaw In Our Phone System

Our Greatest Delusion

The Most Controversial Problem in Philosophy

Why Boredom is Good For You

Why Are 96,000,000 Black Balls on This Reservoir?

We've Been Using The Wrong Science In Court For 50 years

Explaining Pi With Pizza

5 Fun Physics Phenomena

The Most Misunderstood Concept in Physics

Falling ladders - why does this happen?

How a slinky falls in slow motion #shorts

FINALLY: A Proof that Particles Take All Paths At Once?

ATOMS ENGLISH

Why Walls STOP Light Waves But Not Radio Waves?

The Most Extreme Explosion in the Universe

Human Immortality 4K | Can Science Defeat Aging?

Candy Corn In Space

2 The Principle of the Electron Microscope

The Most Important Picture in the History of Science

Brian Cox - The Most Mysterious Facts About The Universe

Fire in ZERO-G!!

The Speed of Light Isn't a Limit. It's a Converter

How Is a Memory Stored Inside Your Squishy Brain?

Về Bài Học Này

Từ Vựng & Cụm Từ Chính

Mẹo Thực Hành

Ngữ pháp trong video

Phương Pháp Shadowing Là Gì?