Pratica di Shadowing: The Biggest Misconception in Physics - Impara a parlare inglese con i video
Scegli una modalità di pratica
Ogni modalità apre una sala di pratica a schermo intero.
325 frasi
Se le frasi sono troppo corte o troppo lunghe, clicca su Edit per modificarle.
1
Imagine you're an astronaut out drifting in deep space.
2
When you throw a rock as hard as you can, what's gonna happen to that rock?
3
Well, you would think that it would continue with constant velocity in a straight line.
4
That's just Newton's first law.
5
But what actually happens is it eventually slows down and stops.
6
So why does this happen?
7
Where did all the rock's energy go?
8
At the turn of the 20th century, the problem of energy conservation baffled some of the greatest minds, including Albert Einstein.
9
Einstein came up with a possible solution.
10
But then a little -known unpaid mathematician named Emmy Noether proved he was wrong.
11
And in doing so, she created a whole new paradigm for physics, one that underlies all of particle physics and explains why anything is conserved.
12
It all started in 1915 at the University of Göttingen, where Einstein was giving six lectures on his new theory of gravity,
13
what would become the general theory of relativity.
14
The lectures were well received, but Einstein hadn't yet settled on the final form of the field equations.
15
One problem he was facing was how to show that total energy was conserved in his new theory.
16
This is the whole beginning of this story, right?
17
Classically, they thought they had this understanding of what the energy of a gravitational field was.
18
All of a sudden, with these new equations, they go, where is it?
19
You know, is it in the curvature?
20
You know, is it in the stress -energy tension?
21
Where's the term that we're looking for?
22
Einstein suggested that the principle of conservation of energy, long established as a bedrock of physics,
23
might hold the key to working out the correct field equations.
24
In the audience, legendary mathematician David Hilbert was intrigued.
25
So he started to look for the energy conservation equations in Einstein's new theory.
26
But the best he could find was a set of equations known as the Bianchi identities.
27
They showed that energy was conserved, but only in a completely empty universe.
28
So for one like ours, filled with stuff, they seemed useless.
29
Hilbert was stumped.
30
Fortunately, he knew just the person for the job
31
His new assistant, Emmy Nutter From an early age,
32
Nutter had dreamed of following the footsteps of her father A mathematics professor at the University of Erlingen
33
She got special permission to attend lectures at the university
34
But they refused to admit her as an official student
35
The Erlingen Academic Senate held that the admission of women would overthrow all academic order
36
So, in 1903, she spent a semester at Göttingen instead.
37
There, she learned about a new way to approach geometry.
38
Using symmetry.
39
Symmetry is one of those ideas that's easy to recognize, but harder to describe.
40
If I align a mirror on this triangle like so, then it looks the same as without the mirror.
41
And that's because this is an axis of symmetry.
42
Reflections about this axis leave the triangle unchanged.
43
And the same thing happens if I put the mirror like this or if I orient the mirror like this.
44
So this triangle has three axes of symmetry.
45
Now mathematicians generalize the idea of symmetry further to be any action you can take that leaves an object unchanged.
46
So something else I could do is I could rotate this triangle by 120 degrees
47
or by 240 degrees or by 360 degrees.
48
Together, these six actions capture all the symmetries of the equilateral triangle.
49
But you can also have more abstract symmetries, for example with a mathematical function.
50
If I shift this function up or down by some constant amount, call it a, then all of its y values will change.
51
But if I differentiate that function, I get the slope and that remains unchanged regardless of whatever constant is added.
52
So you can add any constant to this function and its derivative always stays the same.
53
So there's a kind of translation symmetry.
54
And unlike the symmetries of the triangle, this is a continuous symmetry, meaning you can shift it by any amount you like.
55
Over the next 12 years, Noether became a leading expert on symmetry.
56
She became only the second woman in Germany to earn a PhD in mathematics,
57
and she used this expertise to help Hilbert and Einstein with their problem of energy conservation.
58
The issue had bothered Einstein so much that he proposed a new conservation equation.
59
It said that if we add together the energy of matter and the energy of the gravitational field, then that total remains constant.
60
Its change over time and space is zero.
61
But when Noether saw this,
62
she was convinced Einstein had made a fundamental mistake because this equation disregards the foundational principle that general relativity is built on.
63
Ten years earlier, in 1905, Einstein had introduced his special theory of relativity,
64
and it was built on the idea that the laws of physics were independent of your frame of reference.
65
But so far, Einstein had only applied this principle to inertial frames of reference.
66
Those are frames that move at a constant speed.
67
He began wondering what would it take to generalize that, to consider more general states of motion.
68
After all, trains on the platform, he loved trains.
69
Trains would speed up or slow down.
70
People, you know, moving around the world don't only move at a single constant speed forever.
71
In 1907, he wrote, is it conceivable
72
that the principle of relativity also applies to systems that are accelerated relative to each other?
73
This made him wonder.
74
Perhaps his principle could also be applied to accelerating and rotating frames, frames that move in any way in general.
75
That's the general in general relativity.
76
So Einstein got to work on this largely intellectual pursuit.
77
But then, as he was daydreaming in the patent office, he had what he called the happiest thought of his life.
78
He imagined the window cleaner at the top of the opposite building falling off.
79
And Einstein realized that while the man was falling, he wouldn't feel his own weight.
80
He would be weightless, and anything he dropped on his way down would remain stationary relative to him.
81
It would be just as if he was floating in outer space.
82
It's ironic.
83
We would have sat down with being pulled down to the ground because the gravity of the earth is exerting a force.
84
But Einstein said while that person is in motion, what we call freefall motion, they'll actually feel no gravity at all.
85
There must be some equivalence between accelerated motion and the action of gravity.
86
So Einstein arrived at what he called the equivalence principle.
87
If you were stuck in a rocket in outer space accelerating at 9 .8 meters per second squared,
88
then it would be the exact same as if you were standing on the surface of Earth.
89
and this was huge because it meant that
90
if Einstein could figure out how to understand accelerating frames
91
then he didn't just get a more general theory he would also have a new theory of gravity
92
but to achieve this Einstein needed to make sure the laws
93
of gravity had the same form in every frame of reference this is the idea of general covariance
94
and it's one of the core tenets of general relativity to satisfy
95
it Einstein knew he had to use special mathematical objects called tensors.
96
A simple kind of tensor is a vector.
97
You can write a vector as a set of components multiplied by their basis vectors.
98
For example, this vector can be written as 3x hat plus 2y hat.
99
But I can also write this using a different coordinate system.
100
And with these new basis vectors, the original vector is now written as 2a plus 1b.
101
So the components, the numbers in this list changed, but the vector didn't.
102
It stayed the same.
103
And that's because when the basis vectors change, the components adjust in a complementary way to keep the vector the same.
104
The vector itself is independent of which coordinate system you use.
105
And the same is true for tensors.
106
Only now, instead of having just two components, a general tensor can have any number of them in the form of a matrix.
107
And just like with vectors, you can change a tensor from one coordinate system to another, and the tensor stays the same.
108
So that's why Einstein had to use them to build his new theory.
109
And that was exactly the problem that Knüter found, because when she looked at Einstein's proposed energy conservation equation, it contained a pseudotensor.
110
And as the name implies, that isn't quite a tensor.
111
When you try to transform it from one frame of reference to another, it doesn't remain the same quantity in different frames.
112
The gravitational energy you might observe in one frame completely disappears in another.
113
And Einstein, he had some strange thoughts about this.
114
I mean, people were trying to stamp conservation of energy into relativity by bending the rules of mathematics.
115
So, Nutter knew that Einstein's proposed solution couldn't be the answer.
116
And that made her think.
117
What if general covariance and energy conservation are simply incompatible?
118
And if that's the case, then why?
119
General covariance says that laws of physics must stay the same when you change reference frames.
120
So that is a kind of symmetry, exactly what Noether had spent her career studying.
121
So she started thinking about the symmetries of the universe, beginning with the simplest possible case, an empty static universe.
122
Imagine you're an astronaut in this universe.
123
Since it's empty, there is nothing special about any particular point.
124
I mean, it doesn't matter if you're over here or over there.
125
The universe is completely symmetric under translations in space.
126
So suppose you throw a ball.
127
Well, it'll travel at a given speed, and after a short amount of time, it will have traveled some distance.
128
But since the laws of physics are the same here as just before,
129
Or, we can shift the whole universe and we're back to the situation we started with.
130
And we can keep doing this over and over, and this shows us that the object will continue with that same speed indefinitely.
131
So what we've discovered is
132
that the principle of conservation of momentum is a direct result of the fact that there's a translation symmetry in the universe,
133
that an experiment done in one spot will give identical results to that same experiment done somewhere else.
134
You could move everything from one place to another, and the physics won't change.
135
Similarly, the laws of physics don't depend on whether you perform an experiment like this, or rotate everything by 90 degrees.
136
This universe is symmetric under rotations.
137
So imagine we take a metal rod and spin it.
138
If we let it rotate for a minute, then it will have moved through a small angle.
139
But we can rotate the whole universe back by that same angle, and now we're at the starting position again.
140
And we can keep doing this so that each instant looks exactly the same as the one before,
141
which means the object will keep rotating this way indefinitely.
142
So the law of conservation of angular momentum comes from the rotational symmetry of the universe.
143
Now, another important symmetry of this universe is time symmetry.
144
The laws of physics don't change over time.
145
If you do an experiment today or tomorrow, you will get the same result.
146
So what does this symmetry lead to?
147
Well, to understand this, we're gonna dig into some math
148
and a different way of doing mechanics using the principle of least action.
149
Previously on Veritasium, we learned that everything always follows the path that minimizes a quantity known as the action.
150
This is equivalent to the integral of the Lagrangian L over time.
151
In the simplest case, that's just the kinetic minus potential energy.
152
Euler and Lagrange found that the principle of least action is obeyed so long as this set of differential equations is satisfied.
153
So Noether used action to see how physics was affected by different symmetries.
154
So suppose we do an experiment where the result is the same now as some tiny time interval epsilon later.
155
Then how does this affect the action?
156
Well, the time is going to change from just t to t plus epsilon.
157
And as a result, the Lagrangian is also going to change.
158
So the new Lagrangian will be L prime, which is equal to the old Lagrangian, plus how much the Lagrangian changes over time,
159
that's just dl by dt, multiplied by how long that change lasts, so multiplied by epsilon.
160
But now also remember that the result is going to be the exact same now as a little while later,
161
which means that whatever this term is the dl over dt doesn't affect the equations of motion
162
and it's from this symmetry in the action
163
that we're going to be able to find the conserved quantity
164
so let's take dl dt and rewrite it using the chain rule
165
that gives us the partial derivative of L with respect to
166
X times dx over dt plus the partial derivative of L with respect to V times dv over dt
167
but we can sub in the partial derivative of L with respect to x with this term from the Euler -Lagrange equation.
168
And we can simplify this further by writing dx over dt as V and that gives us this expression.
169
And now notice what we've got right here.
170
We've got the time derivative of some function dL over dV times another function plus
171
that first function times the time derivative of the second function.
172
So we can use the reverse of the product rule to simplify
173
this to the time derivative of dl over the v times v
174
then as a final step we can bring dl over the t to the right
175
so what we found is that
176
if you take the time derivative of this quantity it's equal to zero
177
which means that whatever this is has to be a constant
178
so what is it well remember
179
that in the simplest case the lagrangian is just equal to the kinetic minus potential energy
180
which we can write as 1 half mv squared minus v. So
181
if we take the partial derivative of the Lagrangian with respect to v
182
we're just going to get d over dt m times v multiplied by v
183
so this is going to become mv squared
184
and then we can sub in the Lagrangian
185
so this becomes minus 1 half mv squared minus v
186
but also a minus here so this becomes plus v and all of that's equal to zero
187
which we can simplify to just one -half mv squared plus v is equal to zero.
188
But wait a second, because this is just the total energy.
189
So what we've discovered is that time translation symmetry is equivalent to saying that energy is conserved.
190
The principle of conservation of energy is a direct consequence of time translation symmetry.
191
In a theorem, Noether proved that all of these examples are no coincidence.
192
For centuries, people had no idea where conservation laws came from.
193
But now, Noether had discovered the origin of all of them.
194
She proved that any time you have a continuous symmetry, you get a corresponding conservation law.
195
Translational symmetry gives you conservation of momentum.
196
Rotational symmetry gives you conservation of angular momentum and time translation symmetry gives you conservation of energy.
197
But these are all symmetries of a static, empty universe.
198
The universe we live in is very different.
199
In the 1920s, astronomers measured the velocities of distant galaxies, and they realized all of them are moving away from us.
200
The farther away they are, the faster they're moving.
201
The implication was clear.
202
In the distant past, everything must have been much closer together.
203
In the 1990s, precise measurements of supernovae revealed that not only was the universe expanding, but that expansion was speeding up.
204
This means over large timescales, our universe is not symmetric in time.
205
It was very different 13 billion years ago, and it'll be different billions of years from now.
206
Since we don't have time symmetry, that also means energy as we usually think of it isn't conserved.
207
There's no reason for energy to be conserved anymore because you don't have that symmetry.
208
Think about a photon of visible light emitted 380 ,000 years after the Big Bang.
209
It travels through the universe unimpeded to arrive at our telescopes, not as visible light, but as a microwave.
210
It has lost 99 .9 % of its energy.
211
Where did the energy go?
212
It doesn't go anywhere.
213
Energy is not conserved.
214
And this is exactly what's happening to the rock as well.
215
It starts off with energy, but as it travels through the expanding universe, it slows down and stops.
216
The energy doesn't really go anywhere.
217
It just disappears years, it ends up coming to rest with regards to the other particles in the universe.
218
This doesn't violate any laws of physics because energy and momentum aren't conserved if there is no time or spatial symmetry.
219
So once you know that symmetries give you conservation laws, and so once those symmetries are gone,
220
you don't have to worry about those conservation laws anymore, then you can start drop in these concepts of trying to force something
221
that you want to say is fundamental into the theory and you just deal with what the theory gives you.
222
But if energy isn't conserved in our universe then why does it usually seem like it is?
223
That's because when you're looking at the short timescales that we're used to, time translation symmetry pretty much holds.
224
An experiment done today will give the same results as the same experiment done tomorrow.
225
So that That means, for all intents and purposes, energy is conserved.
226
But over large timescales, on the order of millions of years, well then, the expansion of the universe can't be neglected, and the symmetry is broken.
227
So only when you look at timescales that big do you notice that energy isn't conserved.
228
Noether's first theorem explains why a rock or a photon loses energy.
229
But it didn't fully solve the problem of energy conservation in general relativity.
230
See, so far, Nutter had only dealt with an empty universe,
231
where you could shift the whole universe and the laws of physics would stay the same.
232
But this doesn't work in general relativity, where the curvature can change from one point to another.
233
Now, if you shift the whole universe, rotate it, or let it evolve in time, things don't stay exactly the same,
234
so you no longer have these global symmetries.
235
But Nutter realized there are still other symmetries left.
236
See, no matter how you're moving, the laws of physics always look the same.
237
That's general covariance.
238
And it is a kind of symmetry that holds everywhere.
239
It means that in any small region, we can always change our frame of reference.
240
We can transform the points of space around as much as we like.
241
And since these transformations aren't global, but local, these are called local symmetries.
242
In a second theorem, Nutter proved that for these local symmetries, you no longer get proper conservation laws like we're used to in classical physics.
243
Instead, you get something that only works locally, a continuity equation.
244
One example of a continuity equation describes the flow of water through a pipe.
245
This first term tells you how the amount of water changes in a section of the pipe,
246
and the second tells you the difference between how much water is flowing out and how much is flowing in.
247
In this case, the first term is positive because the water level in this pipe section is increasing,
248
and the second term will be negative because less water is flowing out of the section than in.
249
Together, the two terms cancel to give zero, which guarantees that no water is created or destroyed.
250
If the total amount of water changes in a section, there must either be excess water flowing in or out.
251
In the case of general relativity, Noether found a similar continuity equation, but with an important difference.
252
Imagine that now our pipes are little patches of space -time, and the water is energy flowing from one patch to another.
253
In any individual section, the continuity equation looks exactly the same as before, so that in any small region spacetime, energy is conserved.
254
But when we link these sections together, we need to take into account the curvature of spacetime.
255
And this changes the equation.
256
Now it's as if there are little cracks appearing between different sections of pipe, between the local patches of spacetime.
257
And through those cracks, energy can leak out.
258
In special relativity, the pipe is imperturbable because the pipe is fixed and in general activity, you know, we have to account for the energy
259
that goes into other kinds of change over time and that gets correspondingly more tricky.
260
Now that we have this new equation, we can see how it works by expanding it as a sum of different terms.
261
This first term is analogous to the continuity equation from before, the one which conserves energy within a local patch of spacetime.
262
But now we have all these extra terms.
263
These describe the curvature of spacetime.
264
So as energy decreases in the first term, these curvature terms increase.
265
The energy that you lose from the system you're tracking, we now start attributing it to things like the gravitational field,
266
which has changed because the whole universe is stretched.
267
We should account for the energy that we attribute to the action of the gravitational field as well, because space and time themselves aren't sitting still.
268
And all of this can be described by the continuity equation Noether had found.
269
But when she looked at it, she realized something.
270
It was exactly equivalent to the Bianchi identities, the half solution Hilbert had found.
271
He had dismissed it because it only gave you proper energy conservation in an empty universe.
272
But now Noether proved that it was the best you could do in general relativity.
273
With one paper, she had uncovered the source of all conservation laws, and she had solved the problem in general relativity that eluded Hilbert and Einstein.
274
She was so amazing.
275
I mean, I would go out on a limb
276
and I would say these two theorems are probably the most important theorems for physics of the 20th century.
277
In the following years, the University of Göttingen took steps to make Noether's position more official, allowing her to do what she loved most, to teach.
278
They made her a professor and she even got a small salary starting in 1923.
279
But all of that changed on the 30th of January, 1933, when Hitler became chancellor of Germany.
280
The Nazis banned
281
Jewish people from working at universities.
282
And almost immediately, one of her former students told the authorities of her Jewish heritage, and she was suspended.
283
Despite this dismissal, she continued teaching in the kitchen of her home.
284
Then one day, one of her old students knocked on her door.
285
Clothed in the brown shirt of the Nazi stormtroopers, Noether let him in.
286
He had come to learn math and Noether was happy to teach him.
287
I love what this sort of shows about Noether.
288
You know, she truly deeply cared about math and she wouldn't discriminate whether someone was wearing a Nazi shirt or not.
289
She taught all.
290
But staying in Germany became untenable.
291
Fortunately, with the help of other academics, she managed to obtain a teaching position at Bryn Maw, a women's college in America,
292
where she would teach until her death.
293
In an obituary for the New York Times, Einstein wrote that
294
The reason that Noether's theorem is so important is that everybody just changed their state of mind.
295
All of a sudden, the physicists were thinking about physics in terms of these symmetries.
296
Physicists started applying these ideas to the quantum world too, realizing that charged particles like electrons also have symmetries.
297
Electrons have a phase, which you can think of as an arrow pointing in some direction.
298
But you can offset this phase by any arbitrary amount, so long as you do it simultaneously for all electrons.
299
And that doesn't change anything physically.
300
So there's another symmetry.
301
So what does this offset or gauge symmetry lead to?
302
Well, it leads to the conservation of electric charge.
303
In the 1960s and 70s, Noether's insights led directly to the discovery of new fundamental particles like quarks and the Higgs boson.
304
It taught us where the forces of nature come from, and it even helped to explain the origin of all mass in the universe.
305
Noether's two theorems, although little known, are what has gotten us the closest we've ever come to a theory of everything.
306
But all of this and much more will be covered in a second video,
307
so make sure you're subscribed to get notified when that video comes out.
308
When Emmy Noether set out to study mathematics, she was following in her father's footsteps.
309
But from there, she forged her own path, and before long she was coming up with a whole theory that reshaped our understanding of the universe.
310
That is the great thing about learning.
311
You start by following instructions, building on what others have done before you, but then at some point, you start asking your own questions.
312
You start experimenting and making discoveries.
313
I've loved watching my own kids start this journey, and my longtime sponsor, KiwiCo, has been a big part of it.
314
This month, they sent me their rapid -fire disk launcher crate, and at first, we followed the instructions carefully, putting it together step by step,
315
but as soon as it was built, my kids immediately started experimenting, testing different launch techniques to better hit the target,
316
changing the launch angles, and figuring out what would make the disks fly farther.
317
Without even realizing it, they were engaging with the same questioning mindset that drives real scientific discoveries.
318
So who knows, maybe a simple disk launcher will inspire a young scientist who
319
will go on to make the next great breakthrough in science or engineering.
320
KiwiCo makes this easy by delivering everything you need in a single box, and they have projects for all ages designed by experts
321
and tested by kids to make sure they're not only loads of fun
322
but they also inspire kids to ask questions and get creative with learning.
323
So if you want to try out KiwiCo click the link in the description or scan this QR code.
324
Use my code Veritasium to get 50 % off your first monthly crate.
325
So I want to thank KiwiCo for sponsoring this video and I want to thank you for watching.
Scarica l'app
Tutto ciò che serve per parlare fluentemente
Pronuncia con IAVoto per ogni frase
Pratica IPAPadroneggia ogni suono
VocabolarioCostruisci il tuo lessico
Gioco di vocabolarioImpara giocando
Stesso Canale
C11
White holes and wormholes are probably real. Here's why.
Daily ConversationUniversity Students
C11
Something is jamming GPS over Europe. Here's what we found
Daily ConversationUniversity StudentsWorking Adults
C11
Why is there antimatter?
Daily ConversationUniversity Students
C12
You've (Likely) Been Playing The Game Of Life Wrong
Daily ConversationUniversity StudentsWorking Adults
B22
We're trying something new...
Daily ConversationWorking Adults
C120
How does light 'know' the shortest path?
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
C13
No device could prove Einstein wrong... until now
Daily ConversationUniversity Students
C12
Our Greatest Delusion
IELTS PrepTOEFL PrepUniversity Students
C13
The Most Controversial Problem in Philosophy
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
C12
The Absurd Engineering Behind the Internet
Daily ConversationUniversity StudentsWorking Adults
B11
Falling ladders - why does this happen?
IELTS PrepTOEFL PrepHigh School Students
C110
How a slinky falls in slow motion #shorts
University StudentsWorking Adults
C13
We're 99.9% sure this pattern is true, but no one can prove it
IELTS PrepTOEFL PrepUniversity Students
B23
What is the secret of a good life? Lessons from the longest study on happiness
Business EnglishDaily ConversationUniversity Students
C18
How An Infinite Hotel Ran Out Of Room
University Students
FOR YOU
Video consigliato
C12
174 frasi
This 1 Book Has Produced More Geniuses Than Any University in History
Daily ConversationUniversity StudentsWorking Adults
C13
119 frasi
Mathematics and Physics | Lesson 2 | Understanding the Connection
Daily ConversationUniversity Students
C11
516 frasi
It’s Not As Simple As Putting Data Centers in Space
Daily ConversationUniversity Students
C11
215 frasi
This New Pyramid Theory Explains the Missing Evidence
Daily ConversationUniversity StudentsWorking Adults
C14
59 frasi
How Can You Change Somebody's Opinion?
Daily ConversationUniversity StudentsWorking Adults
C12
58 frasi
Where is the evidence for God? | Bishop Robert Barron
Daily ConversationUniversity StudentsWorking Adults
C187
66 frasi
What science can’t answer, according to physicist Jim Al-Khalili | Big Think
Daily ConversationUniversity StudentsWorking Adults
C1552 frasi
The Professor Who Taught People How To Think (1962)
Daily ConversationUniversity StudentsWorking Adults
C13
279 frasi
LET THERE BE... Voltage? | Maxwell's Equation #2 Explained for Beginners
Daily ConversationUniversity Students
C12
560 frasi
The Most Dangerous Woman in Science Says We Got the Dinosaur Extinction Totally Wrong
Daily ConversationUniversity StudentsWorking Adults
Vocabolario e note di pronuncia per questa lezione
Questa lezione di conversazione si basa sul video “The Biggest Misconception in Physics”. Le parole che ritornano più spesso: energy, symmetry, universe, conservation, Noether. Questo video contiene 255 frasi e 4496 parole da ripetere con lo shadowing. Il parlato dura 27:34. Chi parla ha un ritmo naturale di circa 163 parole al minuto, vicino a una conversazione quotidiana. Solo il 80% delle parole rientra nelle 3.000 più comuni dell’inglese, quindi il lessico è impegnativo.
Vocaboli chiave di questo video
15 parole del video che vale la pena imparare, con pronuncia e significato:
| Parola | Pronuncia | Significato |
|---|---|---|
| symmetry sostantivo | /ˈsɪm.ɪ.tɹaɪ/ | simmetria |
| equation sostantivo | /ɪˈkweɪ.ʒən/ | equazione |
| physics sostantivo | /ˈfɪz.ɪks/ | fisica |
| vector sostantivo | /ˈvɛktɚ/ | vettore |
| principle sostantivo | /ˈpɹɪn.sɪ.pəl/ | principio |
| experiment sostantivo | /ɪkˈspɛɹ.ə.mənt/ | esperimento |
| derivative sostantivo | /dɪˈɹɪvətɪv/ | derivato, derivata |
| pipe sostantivo | /ˈpaɪp/ | cornamusa |
| theorem sostantivo | /ˈθiərəm/ | teorema |
| rotate verbo | /ˈɹoʊ.teɪt/ | ruotare |
| translation sostantivo | /tɹænzˈleɪʃən/ | traduzione |
| gravity sostantivo | /ˈɡɹævɪti/ | gravità |
| minus | /ˈmaɪ.nəs/ | meno |
| triangle sostantivo | /ˈtɹaɪˌæŋɡəl/ | triangolo |
| continuity sostantivo | /ˌkɑn.tɪˈn(j)u.ə.ti/ | continuità |
I phrasal verb che sentirai
| Parola | Pronuncia | Significato |
|---|---|---|
| slow down verbo | rallentare, decelerare | |
| come up with verbo | ideare, escogitare | |
| figure out verbo | scoprire, rendersi conto | |
| speed up verbo | /spiːdˈʌp/ | stringere i tempi |
| end up verbo | andare a finire, finire | |
| get off verbo | scendere | |
| try out verbo | saggiare, collaudare |
Frasi da ripetere
Frasi brevi e complete del video che puoi riutilizzare nella conversazione di tutti i giorni:
- What's gonna happen to that rock?
- Where did all the rock's energy go?
- You know, is it in the curvature?
- You know, is it in the stress-energy tensor?
La grammatica di questo video
Le strutture che chi parla usa di più, con le parole esatte del video:
| Struttura | Nel video |
|---|---|
| Forma passiva be + participio passato — conta ciò che accade, non chi lo fa | is conserved · was conserved · was intrigued |
| Present perfect have/has + participio passato — un’azione passata che conta ancora adesso | we've discovered · has lost · has changed |
Pronuncia a cui fare attenzione
Chi parla usa 63 contrazioni e forme ridotte, come doesn't, we're, don't. Pronunciale nella forma breve, così come le senti.
- I suoni “th”: theorem /ˈθiərəm/, mathematics /mæθ(.ə)ˈmæt.ɪks/, math /mæθ/, mathematical /ˌmæθ(.ə)ˈmæt.ɪ.kəl/, bother /ˈbɑðɚ/
- I suoni “sh” e “zh”: conservation /ˌkɑnsə(ɹ)ˈveɪʃən/, equation /ɪˈkweɪ.ʒən/, translation /tɹænzˈleɪʃən/, partial /ˈpɑɹʃəl/, instruction /ɪnˈstɹʌkʃən/
- Parole lunghe — attenzione all’accento: conservation /ˌkɑnsə(ɹ)ˈveɪʃən/, experiment /ɪkˈspɛɹ.ə.mənt/, derivative /dɪˈɹɪvətɪv/, continuity /ˌkɑn.tɪˈn(j)u.ə.ti/, momentum /ˌmə(ʊ)ˈmɛntəm/
I suoni difficili per chi parla italiano:
- Consonante finale — senza aggiungere una vocale dopo: physics /ˈfɪz.ɪks/, experiment /ɪkˈspɛɹ.ə.mənt/, derivative /dɪˈɹɪvətɪv/, pipe /ˈpaɪp/, rotate /ˈɹoʊ.teɪt/
- /æ/ — più aperta della “e”: translation /tɹænzˈleɪʃən/, gravity /ˈɡɹævɪti/, triangle /ˈtɹaɪˌæŋɡəl/, patch /pæt͡ʃ/, mathematics /mæθ(.ə)ˈmæt.ɪks/
Come esercitarsi con questo video
- Ascolta tutto il video una volta senza parlare e annota le parole che non conosci.
- Inizia a velocità 0,75×, fai shadowing frase per frase e torna alla velocità normale quando diventa facile.
- Registrati e confronta con l’originale, facendo attenzione a parole come symmetry, equation, physics.
Cos'è la tecnica dello Shadowing?
Shadowing è una tecnica di apprendimento delle lingue supportata da studi scientifici, originariamente sviluppata per la formazione dei traduttori professionisti e resa popolare dal poliglotta Dr. Alexander Arguelles. Il metodo è semplice ma potente: ascolti un audio in inglese di madrelingua e lo ripeti immediatamente ad alta voce — come un'ombra che segue il parlante con un ritardo di solo 1–2 secondi. A differenza dell'ascolto passivo o degli esercizi di grammatica, lo shadowing costringe il tuo cervello e i muscoli della bocca a elaborare e riprodurre simultaneamente i modelli di discorso reale. La ricerca dimostra che migliora significativamente la precisione della pronuncia, l'intonazione, il ritmo, il discorso connesso, la comprensione dell'ascolto e la fluidità del parlato — rendendolo uno dei metodi più efficaci per la preparazione alla prova di speaking dell'IELTS e per la comunicazione reale in inglese.