Shadowing Practice: We Traveled Back in Time. Now Physicists Are Angry. - Learn English Speaking with Video

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You're going forward through time, one second every second.

Congratulations, you're a time traveler.

A bit lame, but let's start here to get to the fun real -time travel to ride on dinosaurs and high -five Einstein.

Time isn't really a thing that passes, but a dimension, a direction you can move in.

We think our universe is four -dimensional, with three spatial and one time dimensions smooshed together into a fancy thing we call space -time.

What you experience as time passing and your life happening is actually you moving through the time dimension.

And this dimension is a bummer.

While you can go forward, backward, left and right, up and down in the space dimensions, in time you can only go forward.

You only get older, never younger.

You can't make detours.

But this is an illusion.

You have far more control over how you move through time.

To explain how this actually works, without making a maths video, we have to make a lot of physicists grumpy,

so please keep in mind that we're simplifying and lying a bit.

Okay, so there's a very strange rule.

Everything in our universe moves at the speed of light through four -dimensional space -time.

Your speed through space -time is the sum of your separate speeds through time and space.

It's impossible for you to stay still.

Even if you're not moving through space dimensions, you're moving through the time dimension, blasting face first into the future.

You can slow down in the time dimension by moving faster through the space dimensions,

but in total, you will always move at the speed of light through space -time.

If you could somehow truly stand still in space, you'd still move through time at the speed of light, and the other way around.

Photons, light particles, move at the speed of light through space.

They don't experience any time passing because their speed in that time dimension is zero.

In the time dimension, they're frozen in place.

If you see light on Earth, from the photon's perspective, it was just on the surface of the sun

and then suddenly crashed into your eye with nothing happening in between.

Remember, we're telling a science story here.

In real life, things are more complicated.

For one, it's impossible to truly stand still relative to space itself.

You can only be standing still relative to other things in space.

And you can't really define a reference frame for photons as we just did.

For details, check out our sources.

But now, back to our story.

Okay, so everything in the universe moves at the same breathtaking speed, but this speed is split between space and time.

Which leads to all sorts of wacky things and where we can see time travel happen.

Real and easy time travel.

When a bus drives past you, it's moving a little bit faster through space than you are.

So, it moves slower through time than you.

Or how it's usually worded, the bus is moving slower through time relative to you.

While this makes things feel like weird physics magic, it's very simple move faster through space,

go slower in time, move slower through space, go faster in time.

And if you had another person moving way faster or slower than you, both end up traveling different distances in the time dimension.

The story that's usually told to demonstrate this is to get twins, force one of them into a rocket against their will,

shoot them through space super fast while the other twin chills on Earth.

And because one twin moves very fast through space while the other moves slowly on Earth, They move at different speeds through time.

When the rocket finally gets home, they're no longer the same age,

and the younger space twin is ready to start years of therapy for being abducted by theoretical physicists.

This is the twin paradox, and it makes perfect sense within the rules of the universe.

If you want to learn more about the paradoxes of time, we made a video about it.

But in a nutshell, you're using time dilation, the fact that your position in time is subjective and only true for yourself.

With sufficiently fast rockets, you could get as far as you want into the future.

Technically, this way you can witness the end of the universe or look at the final thing that will ever happen.

We also made videos about that.

We should mention that there's another way to jump forward in time.

Massive objects bend space -time, causing time to go slower near them.

On Earth, the effect is tiny.

The gravity of our planet makes time pass 0 .00000007 % slower than in deep space,

far from any gravitational fields.

Hardly useful for time travel, but it's a start.

If you move into a really strong gravitational field, like around a black hole, the closer you get to the event horizon,

the slower time passes for you.

If we kidnap our twin again, they won't notice it at all.

Their watch ticks as fast as it always does.

But from the outside, they seem to almost stand still.

Only when the twin leaves the gravitational field and comes back to Earth do they realize they'd time -traveled.

Okay, so you can time travel to the future by going fast or near a black hole.

But this is pretty lame and has literally only downsides except for people who want to sort of teleport into the future.

And it makes building a gigantic human space empire super hard, because even if we develop the technology to go really super fast between stars,

going on a far away journey will always mean leaving your home as you knew it forever.

But now that we know all of this, there's actually a way we could use the rules of our universe to travel backwards through time.

The past is a far away land.

Let's go there.

So you always move through space -time at the speed of light.

If you go fast through the space dimension, you slow down in the time dimension.

And here we find an actual opening for backwards time travel.

The theory of relativity, which may be the most solid scientific theory we know, does not forbid faster -than -light motion through space.

If you move through the space dimension faster than the speed of light, superluminal, you need to move through the time dimension with negative speed.

That means you go backwards through time relative to the rest of the universe, into the past.

Actually, scientists have been looking for superluminal particles and given them a name, tachyons.

They could exist and would have wild properties, like getting faster when they lose energy, and, of course, traveling backwards in time.

Finally, real time travel.

Just like with photons, it isn't really possible to clearly define how time passes for tachyons themselves.

It depends on how you move through space -time relative to them.

But now, for the first time, some observers could actually see tachyons literally traveling backwards in time,

which means they could be used to directly interact with the past.

In theory, you could use them to send messages to your past self

and change all sorts of things that have already happened.

Maybe with some tachyon -powered sci -fi future tech, you could see a star die before it was born,

meet your great -grandparents, prevent your past self from making that one dumb mistake, win the lottery or get eaten by dinosaurs,

and create juicy time paradoxes that also kind of break the universe.

Oh, what's that?

Right.

Hmm.

It seems there are things in our universe that are impossible to mix.

Unfortunately, the theory of relativity specifically forbids anything

that starts out traveling slower than the speed of light to reach the speed of light.

Because moving faster through space requires energy, and the energy required to reach the speed of light is literally infinite.

Even if you could gather all the energy of the universe, you couldn't accelerate a grain of sand to the speed of light.

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You can get as close as you like, but you can never reach it.

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It is possible to move at the speed of light as photons do, but they always move at the speed of light.

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If you move superluminally, you will always move superluminally.

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And sadly, so far, we don't have the tiniest bit of evidence that tachyons exist.

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While they work on paper, most scientists think they're not real.

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So for now, it seems that time travel into the past is strictly impossible, no matter how hard we try.

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The past is a faraway land, and while we can look at it in pictures and movies and our memories, it's locked away.

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Forever outside of our reach.

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While this is sad, it leaves you with the most important time there is.

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Right now, the moment where you actually exist, and a future that's yours to forge.

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If you want, you could even time travel to it.

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Luckily, shaping the future is much easier than trying to change the past.

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With the right knowledge and problem -solving skills, you'll be ready for whatever obstacles or opportunities lie ahead,

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which is where our friends at Brilliant come in.

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Brilliant will make you a better thinker and problem solver, with thousands of interactive bite -sized lessons on just about anything you may be curious about,

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from physics and maths to technology, data analysis and beyond.

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You can build real knowledge in just minutes a day, a terrific use of your precious present moments. On Brilliant,

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you'll learn through discovery by trying things yourself their course on scientific thinking for example gets

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you hands on with fascinating questions like the ones in this video

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and since each course is like an immersive workshop you'll gain knowledge of key concepts

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while building your intuition helping

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you learn to think like a scientist kurzgesagt has also partnered

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with brilliant to create a series of lessons to take your

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scientific knowledge to the next level each one is like a one -on -one version of a Kurzgesagt video,

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letting you further explore the topics of popular videos like Rabies, Mammalian Metabolism, or Climate Science and Supernovae.

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And you can get started whenever, wherever, right from whatever device you'd like.

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To get hands -on with Kurzgesagt lessons and explore everything

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Brilliant has to offer, from AI and programming to math,

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science and beyond, start your free 30 -day trial by signing up at brilliant .org slash nutshell.

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There's even an extra perk for Kurzgesagt viewers.

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Anyone signing up through our link will get 20 % off an annual membership once their trial ends.

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We found a way to evade the laws of the universe and go on a truly breathtaking time travel adventure.

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Are you ready?

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Well, too bad.

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Here we go!

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Look, it's the human era.

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12 ,000 years of human innovation brought to life.

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Absolutely incredible how our ancestors laid the foundation for the life we lead today.

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Let's go back even further and take a look at the timeline of life.

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Wow, humans are only a tiny blip at this scale.

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Mammals haven't been around for long either.

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Here's the age of the dinosaurs.

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And going further back, we can see where it all began.

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You can now go on your very own time travel adventure with our Timeline of Human History

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and Timeline of Complex Life posters.

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They're expert approved and designed with great love and care.

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Get them both to get the full time travel effect and to support everything we do on this channel.

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Vocabulary and speaking notes for this lesson

This speaking lesson is built on the video “We Traveled Back in Time. Now Physicists Are Angry”. The speaker keeps coming back to these words: space, speed, dimension, travel, universe. This video has 38 sentences and 1958 words to shadow. The speech runs for 11:03. The speaker talks at a natural 177 words per minute, close to everyday conversation. 86% of the words are among the 3,000 most common in English; the rest is worth studying before you start.

Key vocabulary in this video

15 words from the video worth learning, with pronunciation and meaning:

Word	Pronunciation	Meaning
dimension noun	/daɪˈmɛn.ʃən/	A single aspect of a given thing.
twin noun	/twɪn/	Either of two people (or, less commonly, animals) who shared the same uterus at the same time; one who was born at the same birth as a sibling.
backward adjective	/ˈbækwɚd/	Situated toward or at the rear of something.
relative noun	/ˈɹɛl.ə.tɪv/	Someone connected by blood, marriage, or adoption; someone in the same family.
lesson noun	/ˈlɛs.ən/	A section of learning or teaching into which a wider learning content is divided.
rocket noun	/ˈɹɑk.ɪt/	A cylindrical projectile that can be fired to a great height through combustion, (specifically) a type of firework of this form, typically exploding with light…
scientist noun	/ˈsaɪəntəst/	One whose activities make use of the scientific method to answer questions regarding the measurable universe. A scientist may be involved in original research…
mathematics noun	/mæθ(.ə)ˈmæt.ɪks/	An abstract representational system studying numbers, shapes, structures, quantitative change and relationships between them.
timeline noun	/ˈtaɪmˌlaɪn/	A graphical representation of a chronological sequence of events (past or future).
dinosaur noun	/ˈdaɪnəsoɹ/	Those animals of the clade Dinosauria that existed during the Triassic, Jurassic and Cretaceous periods and are now extinct.
paradox noun	/ˈpæ.ɹəˌdɒks/	An apparently self-contradictory statement, which can only be true if it is false, and vice versa.
adventure noun	/ədˈvɛn.t͡ʃə/	A feeling of desire for new and exciting things.
physics noun	/ˈfɪz.ɪks/	The branch of science concerned with the study of the properties and interactions of space, time, matter and energy.
define verb	/dɪˈfaɪn/	To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly.
explore verb	/ɪkˈsploɹ/	To examine or investigate something systematically.

Phrasal verbs you will hear

Word	Meaning
check out verb	To record the departure or withdrawal of someone or something (such as guests, employees, books, etc.).
end up verb	To bring to a conclusion.
get off verb	To move from being on top of (something) to not being on top of it.
go back verb	To return to a place or state after having been there at a previous time.
going forward adverb	In the immediate future and beyond.
lie ahead verb	To be going to happen in the future; to be in store.
lock away verb	To lock up; to lock in a safe place, out of view.
sign up verb	To add a name to the list of people who are participating in something.

Sentences worth repeating

Short, complete lines from the video that you can reuse in everyday conversation:

You’re going forward through time one second every second.
Congratulations, you’re a time traveler!
It's impossible for you to stay still.

Grammar in this video

The structures the speaker uses most, with the exact words from the video:

Structure	In the video
Conditional sentences if + clause, will/would + verb — a condition and its result	If you move superluminally, you will always
Present perfect have/has + past participle — a past action that still matters now	have already happened · has also partnered · haven't been
Passive voice be + past participle — the focus is on what happens, not who does it	is split · being abducted · was born

Pronunciation to watch

The speaker uses 16 contractions and reduced forms, such as you'll, can't, don't. Say them the short way, as you hear them.

The “th” sounds: mathematics /mæθ(.ə)ˈmæt.ɪks/, breathtaking /ˈbɹɛθˌteɪ.kɪŋ/, gather /ˈɡæðɚ/, theoretical /ˌθi.əˈɹɛt.ɪ.kəl/, thinker /ˈθɪŋ.kɚ/
The “sh” and “zh” sounds: dimension /daɪˈmɛn.ʃən/, dimensional /daɪˈmɛn.ʃə.nəl/, innovation /ˌɪn.əˈveɪ.ʃən/, workshop /ˈwɝk.ʃɑp/, illusion /ɪˈl(j)uːʒ(ə)n/
Long words — get the stress right: mathematics /mæθ(.ə)ˈmæt.ɪks/, dimensional /daɪˈmɛn.ʃə.nəl/, complicated /ˈkɑm.plɪˌkeɪ.tɪd/, innovation /ˌɪn.əˈveɪ.ʃən/, interactive /ˌɪn.tɚˈæk.tɪv/

How to practise with this video

Listen to the whole video once without speaking and note the words you do not know.
Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
Record yourself and compare with the original, paying attention to words like dimension, twin, backward.

What is the Shadowing Technique?

Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.

Shadowing technique: read the full step-by-step guide →

Shadowing Practice: We Traveled Back in Time. Now Physicists Are Angry. - Learn English Speaking with Video

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Vocabulary and speaking notes for this lesson

Key vocabulary in this video

Phrasal verbs you will hear

Sentences worth repeating

Grammar in this video

Pronunciation to watch

How to practise with this video

What is the Shadowing Technique?