ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: Einstein and the Theory of Relativity | HD |

เลือกโหมดฝึก

แต่ละโหมดจะเปิดห้องฝึกแบบเต็มจอ

508 ประโยค

หากประโยคสั้นหรือยาวเกินไป กดที่ Edit เพื่อปรับแก้

Who would have believed that one day we'd be able to see this image?

A black hole in the universe, a strange star from which no light or person can escape.

This image was calculated using the equations of general relativity.

A scientific theory of space and time developed 100 years ago.

A theory that was in turn praised, rejected, forgotten, and then rediscovered.

A theory that this black hole nearly killed.

My theory.

The theory of relativity is infamous for its difficulty.

I want to show that there's nothing peculiarly difficult about it.

Let me illustrate this with an example here.

Let's imagine that this piece of jelly is the space.

Then the presence of matter is to distort the space.

Einstein's theory of relativity does lead us into a very strange and unfamiliar path.

Relativity is perfectly intelligible to anybody who is willing to think.

In the 20th century, I was known by the name of Albert Einstein, and for my equation, E equals mc squared.

I sought to understand nature through mathematics.

I had a new vision of the architecture of the universe, and I expressed it in a theory, general relativity.

General relativity is a theory about gravity, the mysterious force that attracts stars and planets to each other.

For 250 years before my theory, gravity was the realm of the great scientist Isaac Newton.

My theory revolutionized the worlds of physics and mathematics.

Newton's theory of gravity, revolutionary in its scope and concision, had held water since the end of the 17th century.

It is fascinating to think that, to explain just a few changes to this law, everything had to be turned on its head.

And that is exactly what Einstein did.

His theory of gravity involves several major modifications.

Space is no longer straight, but curved, depending on the matter inside.

giving a position at a given time no longer makes sense.

Positions and times are intertwined, and geometry now has to be seen in four dimensions.

And we can't count on this equation here anymore.

It needs to be replaced by one with a radically different form.

First of all, I discovered that space and time were actually connected, working as one.

And matter, such as stars and planets, bends and curves this space -time.

That curvature is the gravitational field, obliging the planets to rotate around the Sun.

Nothing, not even rays of light, can escape the curvature.

All these discoveries were based on a single observation, that of freefall, known since Galileo, and which can even be observed on the moon.

In my left hand I have a feather, in my right hand a hammer,

and I'll drop the two of them here and hopefully I'll hit the ground at the same time.

I'll find proof that Mr. Galileo is correct.

I saw and understood freefall differently from all other people.

It guided me towards the curvature of space -time.

All I had to do was observe closely.

Einstein himself tells us about the moment when he understood

that this was the tool that would allow him to form his theory.

In 1907, he wrote, I was sitting at my desk in the patent office in Bern

when suddenly I thought that if somebody was in free fall they wouldn't feel their own weight, and I was surprised.

He realized that gravity has the property, and is the only force with this property, of disappearing as a result of its own effect.

And that if we are in free fall, and so under the effect of gravity, we feel like there's no gravity.

In my day, I was only able to experiment this idea through thought.

But 100 years later, the physicists of the 21st century have new tools, such as this tower in Germany,

which can create a vacuum that eliminates air resistance.

By dropping objects in capsules into the tower, we can see how, in free fall, our weight disappears.

In this experiment, we put two objects on a scale in this capsule which will be dropped into freefall in the tower.

The needles on both scales will fall back to zero, showing, albeit not particularly precisely,

how this apple and this one kilo weight fall in exactly the same way in the gravitational field.

So it looks like mass doesn't exist anymore, which may seem absurd, because if we're able to eliminate gravity, then does gravity exist?

Once sealed, the capsule will be raised to a height of 110 meters for a five -second free -fall in the vacuum.

So we have perfect conditions for every experiment that is done in weightlessness.

So for example, if we have some experiments for space, we can test the payload or the equipment in our facility.

Thank you.

You're welcome.

Here we have a view of the inside of the drop tube.

Okay, so three...

Then after one second, it will go.

Three, two, one...

Wow.

Impressive. So now...

I'm a launcher.

So now we have to search for the right time in the video for the right...

For the five seconds.

The five seconds.

Okay.

So this is...

Something is happening.

Okay, so now here we are during the free fall.

It's almost zero on both sides.

Gravity has disappeared.

You twerked?

Yeah.

Until now, this principle, the cornerstone of my theory, has proved watertight.

Nobody has been able to prove it wrong.

A team of French researchers is preparing to test the principle in space.

Their satellite microscope, set for launch in 2016, will orbit 700 kilometers above the Earth and provide an unprecedented precision of measurement.

But let's wait and see.

In science, the experiment is our sole judge.

Back in 1907, this idea, today known as the principle of equivalence, led me like a lighthouse in the night to rethink gravity.

I returned to Switzerland in 1912 after five years of work.

I returned to the city of my student days.

The two years I spent in Zurich would be the most important of my life.

I I was offered a professorship in physics at the Zurich Polytechnicum School, now known as ETH Zurich.

So here's an ETH.

One of my old university friends, Marcel Grossman, had become a professor there.

He was far better than me in geometry.

His notebooks inspired me on numerous occasions.

Impressive, no?

Yes, it's very detailed.

The fundamental properties of elliptic functions.

He was preparing to work for Einstein, without knowing it, obviously.

But that's what was going on.

It's really surprising.

I didn't think it happened like that.

100

What I would have done without Grossman, I really cannot say, because the mathematical obstacles before me seemed insurmountable.

101

General relativity made me work like a monomaniac.

102

To see if I was on the right track, I used a flaw in Newton's theory.

103

Newton's gravitational equation couldn't predict the precise orbit of Mercury around the Sun.

104

Mercury's perihelion, its closest point of the Sun during the year, shifted much too fast.

105

This was a perplexing problem that physicists and astronomers just couldn't crack.

106

He arrived at the definitive theories in November 1915.

107

Definitive in particular because he determined

108

Mercury's perihelion with incredible precision.

109

After all these years, I still remember those evenings spent with Marcel Grossman in this café on the River Limat, putting the world into equation.

110

Our discussions concerned not only our studies, but ranged far beyond, over all the topics that could interest young people who kept their eyes wide open.

111

It was here that my theory took form.

112

The key to describing gravity is the geometry of space -time.

113

So, for the objects present in the universe, you have to determine the gravitational field they create, namely the geometry of space -time.

114

To do so hinged on solving an equation that took me eight years to create.

115

I wrote it as follows g mu nu is equal to 8 pi g over c4 times t mu nu.

116

A single equation and just a few mathematical symbols to describe our universe.

117

Based on a mathematical hypothesis, he opened up a new path, one that is still relevant today.

118

It's incredible.

119

You could have thought that it wasn't going to work. But it did work.

120

And it was here that the theory started to take on a life of its own, to unveil properties of nature that nobody had foreseen.

121

Curved geometry implied that time didn't pass in the same way in all parts of the universe.

122

Gravity influences time.

123

The stronger the gravity field, the more time slows down.

124

This threw everybody, myself included.

125

In my day, it was impossible to test this prediction through experiments gravity on Earth is too weak

126

and its effects on time are imperceptible.

127

But technology having evolved, in your day, this difference in time can be measured with amazing precision.

128

The new atomic clocks in the basement of the Observatoire de Paris are the most precise clocks in the world,

129

a billion times more precise than a quartz clock.

130

Even at this level of precision, my theory still works.

131

The effect is true everywhere.

132

The universe does not tick to a huge universal clock, as Newton thought.

133

Each region of the universe has its own time.

134

Each galaxy and each solar system exists in its own space -time.

135

Looking at the universe involves looking at other times.

136

In 1915, with World War raging, the publication of the theory of general relativity went unnoticed, gravity being elsewhere.

137

But I did receive a letter, from the German physicist Carl Schwarzschild.

138

With my equations, he had succeeded in calculating the distortion of space -time generated by a star.

139

This was a titanic achievement, given that my equation breaks down into ten others, and each one of them had to be solved.

140

But his work exposed a sort of minor flaw in the equations that nobody noticed.

141

This flaw would later be called the Schwarzschild singularity.

142

With his solution, Karl Schwarzschild cleared the way for the mathematical exploration of the theory.

143

Unfortunately, this was to be the only letter I received from him.

144

He died in the war in May 1916.

145

The seemingly never -ending war prevented the circulation of scientific publications.

146

But a ray of hope came to me from Great Britain, where I was nevertheless considered an enemy.

147

In Britain in 1915, there was a British astrophysicist called Eddington,

148

who was a pacifist, who was not at war.

149

In fact, was still at his post in Cambridge.

150

Now, it so happens

151

that Eddington was one of the few people in Britain who was capable of understanding what Einstein was writing.

152

And he immediately grasped the significance of this general relativistic theory.

153

The best physical test to confirm my theory was to measure

154

if the rays of light reaching us from far away actually followed the space -time curvature.

155

The sun is the only close and available mass that can curve space -time in a significant manner.

156

But if the sun is in the sky, it is daytime and the distant stars are invisible.

157

Our only chance would be to photograph the starry sky during an eclipse.

158

The war ended in 1918 and the following year he travelled, he led an expedition which went in two parts,

159

part to the island of Príncipe, off the coast of Africa and to Brazil.

160

Weather wasn't totally favourable, the observations weren't brilliant,

161

but they were sufficient to show that light was bent in exactly the way Einstein had proposed.

162

And when he came back, Eddington did a number of presentations and huge popular lectures about this work

163

and I think in the English -speaking world that launched Einstein.

164

Eddington presented his results to the Royal Astronomical Society, standing before a large portrait of Newton that had sat there undisturbed for over two centuries.

165

Reportedly, the whole atmosphere of tense interest was exactly that of a Greek drama.

166

Napoleon and other great men of his sight, they were makers of empire.

167

But there is an order of men who get beyond that.

168

They are not makers of empires, but they are makers of universes.

169

When they have made those universes, their hands are unstained by the blood of any human being on earth.

170

Solomon made a universe which lasted 1400 years.

171

Newton also made a universe which has lasted 300 years.

172

Einstein has made a universe, and I can't tell you how long that will last.

173

After my theory was confirmed, I received invitations from around the world.

174

During one of my trips in 1921, I found out that I had been honored with a Nobel Prize for Physics.

175

Strangely, I didn't receive the prize for general relativity, no doubt still too controversial, but for my previous work.

176

There was little talk of my theory of relativity.

177

As Charlie Chaplin once said to me, they're cheering us both, you because nobody understands you, and me because everybody understands me.

178

When I was in Paris in 1922, people wanted me to talk about time.

179

I recall people talking about it more in philosophical salons than in scientific conferences.

180

The fact is, nobody there understood the slightest thing about my theory.

181

But my most vivid memory is of a conference at the Collège de France.

182

A French mathematician, Jacques Ademar, stood up and pointed at me threateningly, pointing out a supposed flaw in my theory.

183

He brought up the very mathematical flaw that had escaped me in Schwarzschild's solution.

184

That's the Schwarzschild solution from 1916.

185

If I understand correctly, r is the radius relative to a central point, namely a star?

186

Yes, it's a star and its mass is m.

187

OK, but you can see straight away that there's a problem.

188

because if I see a radius equal to 2 gm divided by c squared,

189

the coefficient here becomes zero, which isn't right.

190

And here you get 1 divided by zero equals infinity, which is even worse.

191

Your solution falls flat on its face.

192

That's exactly what Jacques Hadamard said to Einstein in Paris.

193

It was terrible for Einstein because here, obviously, we're talking about maths.

194

But think about physics, which, for example, determines the geometry around our sun, the sun in the solar system.

195

Imagine we send a satellite towards the sun.

196

What happens when the satellite gets to this point?

197

Does it stop?

198

Does it explode?

199

Or does it disintegrate?

200

And that must have been seen as a fatal blow to Einstein's theory, right?

201

It did pose a major problem for Einstein because his theory was supposed to determine the structure of space space -time, and for a particular solution,

202

he saw that there were places where the idea of space and the idea of time no longer made sense.

203

The end of the world in equation form.

204

That's right, the edge of the world, what we call the Schwarzschild singularity.

205

No doubt this all looks abstract to you, a few symbols on a blackboard.

206

But for me, this singularity was a real monster.

207

It resembled a sphere, an impenetrable black bubble, a place in the universe where time seemed to stop and where space no longer existed.

208

The sphere appeared at the center of all celestial objects, like a star.

209

Fortunately, after a few calculations, we discovered that for our Sun, the size of the singularity was just three kilometers, hidden inside.

210

For it to become visible in our solar system,

211

we would need to be able to condense the entire mass of the Sun into a three -kilometer sphere.

212

For astrophysicists then, the singularity remained imaginary.

213

But mathematicians had a serious problem on their hands.

214

Would it prove fatal for my relativity?

215

Soon, the entire community was talking about the singularity.

216

And apart from a few firmly convinced cosmologists, pretty much everyone dropped my theory.

217

These were hard times for Einstein.

218

After his glory days, when relativity was in all the newspapers,

219

when he was the star of the Parisian Salons and spent the 1920s traveling around the world, he was the most heralded scientist of the day.

220

But interest in his theory shrank dramatically and life for people working on relativity became difficult.

221

With Elsa, I moved to Kaput, near Berlin.

222

I took up sailing as a hobby.

223

Until the day when events forced me to leave my homeland in 1933, forever.

224

Dr. Einstein, who gave the world its biggest headache, is back in California again with with his wife.

225

They've been found all night in San Pedro Harbor.

226

The professor had a theory as to how they could land, but before he and the captain could figure it out,

227

the fog had all gone away.

228

Now he's going to the Institute of Technology in Pasadena to work with other distinguished scientists.

229

There his theory will be thoroughly discussed and analyzed, and if it is what he says it is,

230

why then everything will be all right, won't it?

231

Physicists were extremely wary and not very interested.

232

There was a certain amount of aggression, from physicists in particular, except for the people who believed in it, who were few and far between.

233

And then there were those who simply didn't want to try and get their heads around it.

234

The problem of singularity grew as the years went by.

235

The impenetrable sphere, hidden in the heart of the stars, remained an obsession, impossible to understand, to imagine.

236

The edge of the world.

237

Relativistic scientists working on the gravity of stars such as our Sun found that according to my theory, stars could die.

238

That really was the limit.

239

Because the theory appeared to say that in dying, the star imploded and its size reduced to approach that of its singularity.

240

So stars are born and live and die.

241

The sun's future history is fairly simple, not good for us on Earth.

242

The sun will go through several phases, including swelling then it will ultimately shrink to one of these white dwarfs

243

and will steadily cool thereafter, just stop producing energy, stop its fusion reactions, but still quite hot and cooling.

244

For a star that's much bigger than the sun, basically what happens is the core of the star collapses to make a neutron star.

245

The rest of the material suddenly finds it standing on nothing goes rushing down to get a foothold,

246

meets this very, very solid neutron star and bounces out.

247

And 90 or 95 % of the material of the star goes out and the other little bit remains.

248

This extremely dense neutron star with a radius of barely 10

249

kilometres is coming dangerously close to the Schwarzschild singularity sphere hidden in its centre.

250

The risk I immediately saw was that it could be discovered in the theory that stars could condense even further,

251

and their singularity escape from within.

252

The question that immediately comes to mind is, do we know any stars? stars whose Schwarzschild surface, the edge of the theory,

253

is on the exterior of the celestial body?

254

You would have made an excellent physicist, or even astrophysicist.

255

Can we find any solutions in which we have the star or the celestial body, and here, the Schwarzschild singularity?

256

Those are probably created from really massive stars.

257

Once that big star begins to run out of nuclear fuel, gravity wins, so the star shrinks.

258

That puts up the gravity at the surface of the star,

259

so it shrinks, which puts up the gravity at the surface of the star, so it shrinks.

260

And it shrinks right down.

261

And even the atoms, you know, things like this table and chair I made of, the atoms collapse and the nuclei collapse.

262

And if you believe

263

If you believe the theory, it collapses down to a point, which is zero radius.

264

Some people don't like these kinds of points and zeros, so that's debated, but it goes down to very,

265

very, very small, having been one of the biggest stars in the universe before.

266

And it's a black hole.

267

All of a sudden, mathematicians and physicists were telling me, Einstein, that the Schwarzschild singularity, the flaw in my theory,

268

could in reality exist in the real universe, stepping out of the world of mathematics like a magical sphere.

269

And a completely black sphere, a place where space and time disappear.

270

I didn't want to believe it.

271

For me, the singularity had to remain a mathematical hypothesis.

272

A star can't just cave in like that.

273

Cave in, not stretch, but implode.

274

It's not possible.

275

There's something unbearable about that.

276

Other people, in particular Eddington, thought there must be something wrong.

277

He thought there must be something wrong in the calculation, but if not, there had to be something wrong in the physics.

278

So he thought, you know, nature shouldn't behave like this.

279

But then, it is a strange way for nature to behave, which is very different from the sorts of things that one is used to.

280

The most extraordinary thing in all this was Einstein himself.

281

He didn't want to believe that the Schwarzschild singularity could really be manifested, so he set out to prove it.

282

The worst paper he ever wrote.

283

He took the conclusion he wanted to reach as the basis for these calculations.

284

The main result of my research clearly concluded that Schwarzschild singularities didn't exist in physical reality.

285

It really was a poor paper by Einstein, one of the worst, but we can forgive him because he did write some excellent ones too.

286

It was all too much for me.

287

My own theory had completely escaped my grasp.

288

Since the mathematicians had invaded the theory of relativity, I did not understand it myself anymore.

289

In the USA in the 50s, I was seen as a sort of fossil, made deaf and blind by the years.

290

Ultimately, I didn't mind that role.

291

It suited my temperament.

292

Shrouded in this mystery, I left our planet.

293

And I can guarantee you that the most beautiful thing we can experience is the mysterious.

294

The doubt persisted after my death.

295

The black hole continued to disturb.

296

A number of competing theories showed that it can't even exist because logically speaking,

297

a star cannot simply collapse to zero but the life of relativity would be changed by the 1960s and the British

298

according to Einstein's theory the black hole that results from the collapse of a star several times the master

299

Sun would be an object several miles in diameter but

300

if you say imagine the earth compressed right down until it

301

became a black hole the dimension would be a bit less than an inch something like that

302

That's the Earth.

303

The Earth would have to be compressed into that size to be a black hole.

304

Roger Penrose had, like myself in my day, ideas that came to him entirely unannounced.

305

At the time I was getting very interested in this, which was 1964, perhaps a little earlier than that,

306

and there was a lot of interest in gravitational collapse at that time.

307

Well, I was pondering over these issues at one time.

308

I was at this time at Birkbeck College, where I was a lecturer, and a colleague of mine,

309

Ivor Robinson, who also had an important influence in many aspects of gender relativity, and he was talking to me very excitedly about certain things.

310

I forget what they were, I'm afraid.

311

But we came to a road, and when we crossed the road, the conversation stopped and when we get to the other side,

312

instead of walking into a wall...

313

Yeah.

314

We...

315

I forget what I had, the idea I had, which was crossing the street here, you see.

316

Mm -hm.

317

And then he goes off later.

318

Yes.

319

And then I try to remember...

320

Yeah.

321

...why I feel happy.

322

Why do I feel happy?

323

I have no idea.

324

So I think, am I breakfast?

325

No. ordinary breakfast, so on, you see, all through the day.

326

And then think, aha!

327

I had this idea about how you could characterize

328

a collapse of a star to a point where it is gone too far, point of no return.

329

And this was a surface which I call a trap surface.

330

And this surface can be irregular,

331

can be not symmetrical, but it has a very curious property that the light on both sides is focused inwards.

332

And I knew I could use this condition to try to prove a theorem.

333

Roger Penrose put into an equation the black hole that had thwarted so many physicists before him, myself included.

334

He proved definitively that when a star collapses, all its constituent matter condenses into a single central point, an infinite density of matter,

335

a point where time stops.

336

Roger Penrose worked with some important people, and most decisively with the young physicist Stephen Hawking.

337

The two earned a medal from the Royal Astronomical Society for their work on black holes.

338

Well, I haven't seen this before.

339

Yes, proposal for the Eddington Medal, that's what it was, yes.

340

I talked to Stephen at that time, and we had quite a long discussion on the details of this type of argument.

341

And this had a big effect on what he did later.

342

He generalised the argument to cosmological situations, and then further on we got together and had a general theorem

343

which seemed to encompass pretty well all the things that had occurred earlier.

344

I'd been dead for 10 years, I think, and this time I had to accept that my theory predicted the existence of black holes.

345

Despite everything, even if the work of Roger Penrose was convincing,

346

nothing proved that these singular celestial bodies arising from the death of stars actually existed.

347

It was all purely theoretical.

348

But new means of astronomical observation were developed in the 60s.

349

And a young British scientist was to change her vision of the universe forever.

350

Her name is Jocelyn Bell Burnell.

351

Radio astronomy revealed new kinds of objects, things that did not look particularly conspicuous or spectacular to the optical astronomer.

352

My first two years were spent working in the field constructing a radio telescope.

353

By the time at the end of my PhD I could swing a sledgehammer, which was not a skill I expected to acquire, but I did.

354

We started observations in the summer of 1967.

355

And after about a few weeks of observing,

356

there was the first indication of a curious signal.

357

So then I turned my attention to this thing, which meant going out to the observatory each day just before the telescope turned to it,

358

switching to a high -speed recording, and it turned out to be this string of pulses, about one and a third seconds apart,

359

which was not something I expected, I have to say.

360

We hadn't known about anything like that.

361

We hadn't imagined that anything like that could exist.

362

But the universe doesn't change in a day.

363

Jocelyn Bell Burnell came under heavy criticism until she detected, after months of inflagging work, a second similar source.

364

Ha!

365

What's that?

366

That looks a bit like the first signal that we've been chasing.

367

That bit of sky will be seen by the telescope at 2 o 'clock in the morning.

368

It was very cold and the equipment wasn't working properly in cold weather.

369

It was some problem with the receivers.

370

And of course when I got there it wasn't working properly.

371

But I got it to work properly for five minutes

372

and it was the right five minutes as the telescope was looking in

373

that direction and it was the right beam setting and in came pulse pulse pulse pulse

374

and that for me was actually the the eureka moment the sweet moment

375

because you know it's not the equipment with the fault you know it's not interference

376

it really does begin to look like a new class of object, still don't know what.

377

Well, these signals that we're picking up are entirely new.

378

Nothing like this has been seen in radio astronomy before.

379

Here is a discovery which illustrates the universe is far more complex than we at present believe.

380

It's not showing any sign of tiring, which means it's got lots of energy,

381

which means it's big, but because it's going fast, it's small.

382

So it's big and it's small.

383

That didn't make sense for a while, until we got our questions a little sharper.

384

It's small in the sense of how wide it is, but it's big in the sense that it's got a lot of mass.

385

Not that it's physically big, but it's got a lot of mass.

386

And we can see with hindsight that these very, very dense stars, which are small and massive, actually explained it.

387

Jocelyn Bell Burnell had discovered a pulsar.

388

And everything seemed to suggest that a pulsar was a neutron star.

389

The remnants of the death of an extremely dense star, neutron stars are the closest thing to a black hole.

390

So my theory was right, and in the end, I was wrong to doubt it.

391

Anyone who has never made a mistake has never tried anything new.

392

It became clear then that all the theoretical hypotheses posited earlier on what was possible on how stars evolved,

393

how they died and how they can collapse to become neutron stars were true and correspond to phenomena in the real universe.

394

Which also meant that the next step, i .e that

395

if you have a dead star but one that is too massive to be a neutron star, and so according to Einstein's theory,

396

has to be a black hole was that black holes exist too.

397

And after the discovery of pulsars, the conceptual landscape changed and everyone considered it clear that not only did neutron stars have to exist,

398

but that black holes had to exist too, and that we would find them one day.

399

The gravity on a pulsar is very, very strong.

400

You've got the mass of the sun, thousand, million, million, million, million tons, all in a ball 10 kilometers across.

401

And this produces some curious effects, curious to our minds.

402

They're explainable by general relativity.

403

One is that the gravity bends light rays.

404

So if I look that way on the surface of the pulsar, I actually see over the horizon.

405

I see over the horizon in every direction.

406

And it also affects clocks.

407

If I'm on a pulsar and you can see my watch,

408

you see the second hand is making one tick every two seconds because the gravity has slowed the clock so much.

409

I can use my watch, take my own pulse, and it's okay.

410

But that's because the gravity has slowed my heart the same way, and my metabolism.

411

And actually, I have problems getting onto the neutron star, the pulsar, because as I come down to land,

412

I am pulled down by this very strong gravity but there's a very strong gradient of gravity.

413

The force on my feet is much stronger than the force on my head.

414

Your body gets stretched.

415

There's a technical term for this.

416

It's called spaghettification after spaghetti.

417

But actually the difference in force.. between the bottom of your body

418

and the top of your body is so strong, it breaks.

419

Your body gets pulled apart.

420

Your feet get pulled off your legs, your legs get pulled off your body, your head separates from your body,

421

and the different bits of your body drop onto the neutron star, one after the other.

422

So don't go there.

423

Not a healthy space.

424

The universe is far stranger than I dare to imagine.

425

The famous Schwarzschild singularity, an impenetrable sphere, actually represented the edge of a black hole.

426

But what actually happens if we try to cross it?

427

This surface has an extraordinary property.

428

It isn't material, and yet it separates space -time into two zones, each with different properties.

429

You can cross it in one direction and send light from the exterior to the interior,

430

but you can't send light from the interior to the exterior.

431

It's a trap you never get out of.

432

A black hole is above all a solution to the theory of general relativity.

433

It is a mathematical solution, a space -time configuration, a universe.

434

And the question is finding out if this solution actually corresponds to something in the physical world.

435

We aren't sure that black holes exist in the real universe.

436

There are strong signs, though they remain indirect.

437

But the entire evolution of astrophysics in the 20th century, the fact that stars are born and die,

438

that very dense dead stars exist such as neutron stars, and that neutron stars have a maximum mass,

439

all this strongly indicates that black holes must exist in the real universe.

440

Maybe we will find absolute proof in a few years.

441

Finally, my theory of general relativity has found its field of application.

442

It describes the infinitely large.

443

Astronomers today are following in the footsteps of Roger Penrose,

444

Jocelyn Bell -Burnell, Thibaut Damour and many others as they search for the existence hidden in the immensity of our universe.

445

Without relativity, there would be no

446

Big Bang theory, no relativistic astrophysics, and not even a scientific cosmology with which to speculate on the origin of our universe and its future.

447

That said, as always in science, each new discovery brings with it new questions.

448

And the black hole concealed yet another surprise over its horizon.

449

So if you go inside a black hole, you should find a point at its center,

450

because if a star collapses in on itself, it crosses the horizon.

451

But what does it do after that?

452

It collapses.

453

And what happens?

454

General relativity says that the fabric of space -time tears, and that a true space -time singularity now exists at the center of the black hole.

455

In other words, space -time has ceased to exist.

456

It gets swallowed by the whole.

457

And then that information is lost to the universe.

458

Now you see, this is not something people like.

459

I can see there's some feeling of unhappiness from you on this position point.

460

You're not unique in this, I may say.

461

And it's probably the majority of you amongst physicists now that the information somehow has to get back again.

462

Maybe into another universe, maybe gets out through some curious effects of quantum mechanics one way or the other.

463

Personally, I think it has to be lost.

464

Today, I enjoy watching all these relativistic scientists from afar as they try to resolve new mysteries.

465

From string theory and loop theory to non -commutative geometry and twisters, a number of ideas have emerged to try and go beyond my theory.

466

One such speculative idea has been developed by Carlo Rovelli.

467

General relativity works very well, but it clearly tells us that it doesn't work in the center of the black hole, where singularity takes hold.

468

And this is where we need quantum mechanics, and for which we have a theory of quantum gravity that should tell us what is going on.

469

What that theory tells us or suggests is that afterwards, it bounces out and boom.

470

Hold on.

471

If you say that it bounces out, then you should be able to see loads of little explosions everywhere.

472

So why don't you?

473

Exactly.

474

That's the magic of the theory.

475

Because if you were on the star and strong enough to resist all that pressure, then that rebound would be practically immediate, a few milliseconds.

476

Except that in general relativity, time passes at different speeds in different places.

477

In a black hole, that effect becomes enormous, very, very strong.

478

According to our calculations, a millisecond inside a black hole corresponds to billions of years outside.

479

So if this image is correct, what is a black hole?

480

It's a star that becomes extremely small, a Planck star, and then bounces out and explodes.

481

But seen from the outside, the whole thing happens in slow motion, extreme slow motion, taking billions and billions of years.

482

I think that a mystery lies at the heart of physics, A mystery that has yet to be solved.

483

And that mystery is the nature of time.

484

What really is the passing of time?

485

We've discovered that time is not universal as understood by Newton.

486

We've discovered that each person has their own time.

487

We've discovered lots of things about time.

488

But what really is the passing of time?

489

We don't know.

490

The theory my colleagues and I are working on,

491

loop quantum gravity, has a set of equations limited to general relativity in one case and quantum mechanics in another.

492

These equations are special because they have no time parameter in them.

493

So time is not a fundamental ingredient of the universe.

494

Obviously, as with all theories on quantum gravity, we are not sure because we have not yet to establish measurements providing the theory.

495

But I think that on the whole,

496

everyone is convinced that putting general relativity and quantum mechanics together changes something fundamental in our understanding of space and time.

497

To tell you the truth, I would never have wagered that a hundred years later, my theory would still be around.

498

I thought by this stage you would have replaced it with a better one.

499

Now you have to unite quantum theory with my theory of general relativity.

500

I'm convinced that this will once again revolutionize our vision of space and time, as my theory revolutionized the vision of Newton.

501

Isaac Newton, with Einstein, was able more than anyone else to see further,

502

to see more things and discover more things in the world.

503

In a letter he wrote at the end of his life, there's a beautiful sentence in which he says

504

that he doesn't know exactly how others will see him or how they will remember him, but he sees himself as a child on a beach,

505

playing with pebbles, a child who is happy because he has found some particularly beautiful pebbles

506

while in front of him lies the immense ocean of all the things he has yet to understand.

507

And I'm sure that Einstein shared that same sense of the immensity of all we have yet to know.

508

Thank you.

ดาวน์โหลดแอป

ทุกอย่างที่ต้องใช้เพื่อพูดได้คล่อง

AI ให้คะแนนการออกเสียงให้คะแนนทุกประโยค

ฝึก IPAเชี่ยวชาญทุกเสียง

คำศัพท์สร้างคลังคำของคุณ

เกมคำศัพท์เล่นไปเรียนไป

สแกน QR

Download on theApp Store Get it onGoogle Play

FOR YOU

วิดีโอแนะนำ

41 ประโยค

Espacio y tiempo, una cuestión de lengua. Lera Boroditsky, psicóloga e investigadora

Daily ConversationUniversity Students

คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้

บทเรียนฝึกพูดนี้ใช้วิดีโอ “Einstein and the Theory of Relativity” เป็นสื่อ คำที่ถูกพูดซ้ำบ่อยที่สุด: theory, star, gravity, universe, hole วิดีโอนี้มี 344 ประโยค และ 6304 คำ สำหรับฝึกพูดตาม ช่วงที่มีเสียงพูดยาว 49:02 ผู้พูดพูดด้วยความเร็วสม่ำเสมอ ประมาณ 129 คำต่อนาที เหมาะกับการฝึกพูดตาม มีเพียง 80% ของคำที่อยู่ใน 3,000 คำที่ใช้บ่อยที่สุดในภาษาอังกฤษ คำศัพท์จึงค่อนข้างยาก

คำศัพท์สำคัญในวิดีโอนี้

คำที่ควรเรียนรู้ 15 คำจากวิดีโอ พร้อมคำอ่านและความหมาย:

คำศัพท์	คำอ่าน	ความหมาย
equation คำนาม	/ɪˈkweɪ.ʒən/	สมการ
collapse คำกริยา	/kəˈlæps/	พัง, ถล่ม
sphere คำนาม	/sfɪɚ/	ทรงกลม
quantum คำนาม	/ˈkwɑntəm/	จำนวน
geometry คำนาม	/d͡ʒiˈɑ.mə.tɹi/	เรขาคณิต
physics คำนาม	/ˈfɪz.ɪks/	ฟิสิกส์
experiment คำนาม	/ɪkˈspɛɹ.ə.mənt/	การทดลอง
pulse คำนาม	/pʌls/	ชีพจร
mystery คำนาม	/ˈmɪs.t(ə.)ɹi/	ความลี้ลับ, รหัสยภาวะ
observation คำนาม	/ˌɑbzɚˈveɪʃn̩/	การสังเกต
horizon คำนาม	/həˈɹaɪ.zən/	ขอบฟ้า
dense คำคุณศัพท์	/ˈdɛns/	แน่น, ทึบ
mechanic คำนาม	/mɪˈkænɪk/	ช่างเครื่อง
telescope คำนาม	/ˈtɛl.əˌskoʊp/	กล้องโทรทรรศน์, กล้องดูดาว
discovery คำนาม	/dɪˈskʌv.ɹi/	การค้นพบ

กริยาวลีที่คุณจะได้ยิน

คำศัพท์	ความหมาย
bring up คำกริยา	เลี้ยงดู, ฟูมฟัก
come back คำกริยา	กลับมา
go out คำกริยา	ออก, ออกไป
pick up คำกริยา	ยก, หยิบ

ประโยคที่ควรฝึกพูดซ้ำ

ประโยคสั้น ๆ ที่สมบูรณ์จากวิดีโอ ซึ่งนำไปใช้ในบทสนทนาประจำวันได้:

I didn't think it happened like that.
You could've thought that it wasn't going to work.
Would it prove fatal for my relativity?
I didn't want to believe it.
Why do I feel happy?

ไวยากรณ์ในวิดีโอนี้

โครงสร้างที่ผู้พูดใช้บ่อยที่สุด พร้อมคำพูดจริงจากวิดีโอ:

โครงสร้าง	ในวิดีโอ
Present perfect have/has + กริยาช่อง 3 — เหตุการณ์ในอดีตที่ยังเกี่ยวข้องกับปัจจุบัน	has disappeared · has proved · has been
Passive voice be + กริยาช่อง 3 — เน้นสิ่งที่เกิดขึ้น ไม่ใช่ผู้กระทำ	was calculated · was known · be turned
Relative clauses who / which + อนุประโยค — ข้อมูลเพิ่มเติมเกี่ยวกับคนหรือสิ่งของ	anybody who is · capsule which will · people who kept

การออกเสียงที่ควรระวัง

ผู้พูดใช้รูปย่อและรูปลดเสียง 67 ครั้ง เช่น didn't, can't, don't ให้พูดแบบสั้นตามที่ได้ยิน

เสียง “th”: mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, mathematics /mæθ(.ə)ˈmæt.ɪks/, theoretical /ˌθi.əˈɹɛt.ɪ.kəl/, hypothesis /haɪˈpɒθɪsɪs/, theorem /ˈθiərəm/
เสียง “sh” และ “zh”: equation /ɪˈkweɪ.ʒən/, observation /ˌɑbzɚˈveɪʃn̩/, precision /pɹɪˈsɪʒ.ən/, calculation /ˌkælkjuˈleɪʃn̩/, publication /ˌpʌblɪˈkeɪʃ(ə)n/
คำยาว — ลงเสียงหนักให้ถูกพยางค์: mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, geometry /d͡ʒiˈɑ.mə.tɹi/, experiment /ɪkˈspɛɹ.ə.mənt/, fundamental /ˌfʌn.dəˈmɛn.təl/, mathematics /mæθ(.ə)ˈmæt.ɪks/

เสียงที่คนไทยมักออกเสียงยาก:

เสียงท้ายคำ — ออกเสียงให้ครบ ไม่เปลี่ยนเป็นตัวสะกดแบบไทย: collapse /kəˈlæps/, mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, physics /ˈfɪz.ɪks/, curious /ˈkjʊɹ.i.əs/, pulse /pʌls/
/v/ — ไม่ใช่ /w/ ให้ฟันบนแตะริมฝีปากล่าง: gravity /ˈɡɹævɪti/, observation /ˌɑbzɚˈveɪʃn̩/, discovery /dɪˈskʌv.ɹi/, convince /kənˈvɪns/, universal /ˌjunəˈvɜɹs(ə)l/
/z/ — เสียงก้อง ไม่ใช่ /s/: physics /ˈfɪz.ɪks/, observation /ˌɑbzɚˈveɪʃn̩/, horizon /həˈɹaɪ.zən/, proposal /pɹəˈpoʊzəl/, afterwards /ˈæf.tɚ.wɚdz/

วิธีฝึกกับวิดีโอนี้

ฟังวิดีโอให้จบหนึ่งรอบโดยยังไม่ต้องพูด แล้วจดคำที่ยังไม่รู้จัก
พูดตามทีละประโยคด้วยความเร็วปกติ ทำซ้ำแต่ละประโยคจนจังหวะของคุณตรงกับผู้พูด
อัดเสียงตัวเองแล้วเทียบกับต้นฉบับ โดยสังเกตคำอย่าง equation, collapse, sphere เป็นพิเศษ

เทคนิค Shadowing คืออะไร?

Shadowing เป็นเทคนิคการเรียนรู้ภาษาที่ได้รับการรับรองทางวิทยาศาสตร์ พัฒนาขึ้นสำหรับการฝึกนักแปลมืออาชีพ วิธีการนี้เรียบง่ายแต่ทรงพลัง: คุณฟังเสียงภาษาอังกฤษจากเจ้าของภาษาและพูดตามทันที — เหมือนเงาที่ตามผู้พูดด้วยช่วงเวลาห่าง 1-2 วินาที การวิจัยแสดงว่าเทคนิคนี้ปรับปรุงความแม่นยำในการออกเสียง ทำนองเสียง จังหวะ การเชื่อมเสียง การฟังเข้าใจ และความคล่องแคล่วในการพูดได้อย่างมีนัยสำคัญ

เทคนิค shadowing: อ่านคู่มือฉบับเต็มทีละขั้นตอน →

ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: Einstein and the Theory of Relativity | HD |

เลือกโหมดฝึก

ดาวน์โหลดแอป

How Einstein changed time forever | Jim Al-Khalili for Big Think

White holes and wormholes are probably real. Here's why.

LET THERE BE... Voltage? | Maxwell's Equation #2 Explained for Beginners

John Berger / Ways of Seeing , Episode 1 (1972)

The Professor Who Taught People How To Think (1962)

This New Pyramid Theory Explains the Missing Evidence

The Philosophy of Rick Sanchez

We Found Galaxies Too Old for the Universe

Cosmic Insignificance Theory: A Simple Idea That Will Change Your Life Forever

Hellraiser, Bataille and Limit Experiences

The Beginning of Everything -- The Big Bang

Espacio y tiempo, una cuestión de lengua. Lera Boroditsky, psicóloga e investigadora

คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้

คำศัพท์สำคัญในวิดีโอนี้

กริยาวลีที่คุณจะได้ยิน

ประโยคที่ควรฝึกพูดซ้ำ

ไวยากรณ์ในวิดีโอนี้

การออกเสียงที่ควรระวัง

วิธีฝึกกับวิดีโอนี้

เทคนิค Shadowing คืออะไร?