How HUGE Is the Universe? The Answer Is Impossible to Believe（原声文稿）

Look up at the starry sky above on a dark, clear night.

Thousands of twinkling dots seem so close as if you could reach out and touch them.

But behind this deceptive image lies an abyss so vast that the human mind simply cannot truly comprehend it. Just how big is the universe, really?

The answer to this seemingly simple question is so staggering that it's hard to believe.

Today we'll embark on an amazing journey up the ladder of cosmic scale.

We'll start with our own Earth, which seems enormous to us, and step by step we'll move further and further away until it becomes an invisible speck of dust.

We'll fly past monstrous stars that make our sun look like a tiny grain of sand.

We'll zip through entire galaxies, and we'll reach the most grandiose structures known to modern science. So get ready.

What you're about to learn will almost certainly change your understanding of your place in this vast world.

And by the end of this story, you may never be able to look at the night sky the same way again. Let's start with a familiar starting point. Our home planet.

The Earth's diameter is about 13,000 kilometers.

For us, this is an unimaginably large space.

Suffice it to say that even a fast passenger jet would need almost two days of non-stop flight to circle the globe at the equator.

The Earth seems like a vast world to us.

And indeed it is if we compare it only to ourselves.

But step outside our home, and everything changes dramatically.

Take, for example, Jupiter, the largest planet in the solar system.

This gas giant is approximately 11 times larger in diameter than Earth.

More than 1,000 planets the size of our own could easily fit inside it.

And yet, even mighty Jupiter is a mere dwarf compared to the true ruler of our system.

Around it, planets line up in a whole retinue of varying sizes。 from tiny mercury to ringed Saturn.

But all of them, taken together, are a mere trifle compared to the giant they obediently orbit. And that giant is our Sun.

The Sun is so enormous that its true size is almost impossible to comprehend.

Its diameter is approximately 1,400,000 kilometers.

In other words, it is approximately 110 times wider than the Earth.

More than a million planets similar to our own could fit inside the Sun.

It accounts for almost the entire mass of the solar system。 leaving only a tiny fraction of a percent for all the planets。 satellites, and asteroids combined.

And yet our Sun is a completely ordinary, unremarkable star。 among countless others in the universe.

But the true scale begins to strike when we consider the distances.

The Earth and the Sun are separated by approximately 150 million kilometers.

To get a sense of this distance, imagine driving toward the Sun in a car。 speeding non-stop at 100 kilometers per hour.

Such a journey would take you more than a century and a half.

This distance is so important to astronomers that they developed a special unit of measurement for it。 called an astronomical unit.

Anything further out in space is much more conveniently measured in such enormous steps.

Incidentally, even light, the fastest thing in the universe。 takes about eight minutes to travel from the Sun to Earth.

This means we always see our Sun a little bit in the past。 as it was eight minutes ago.

And, looking ahead a bit, I'll say that we'll soon need many, many more such steps. Now let's move even further.

Neptune, the farthest of the major planets。 is approximately 30 astronomical units from the Sun。 30 times farther than Earth. But it's not even the edge of our solar system.

Beyond its orbit lies a cold, twilight belt of icy debris。 and even farther away circle the even more distant dwarf planets。 one of which takes many hundreds of years to complete just one orbit around the Sun. But that's not all.

The true boundary of the solar system is considered to be the Oort cloud。 a gigantic spherical shell of billions of icy bodies enveloping our system from all sides.

Its outer edge, according to scientists。 is approximately 100,000 astronomical units from the Sun.

It is from this distant cloud that long period comets are believed to arrive。 taking thousands, even millions of years to reach the Sun.

This distance is so great that it is difficult to measure even in familiar units.

And here comes into play a new。 even more grandiose measure of length called the light year.

And once we begin to think in light years。 our journey will truly transcend everything familiar and understandable. What is a light year?

It's the distance a beam of light travels in one Earth year。 and light, as we know。 is the fastest thing in the entire universe.

It travels at almost 300,000 kilometers per second.

In a single second。 a beam of light would circle the Earth more than seven times.

And so, moving at this incredible speed for an entire year without stopping。 light travels about nine and a half trillion kilometers.

That's exactly how long one light year is. Now think about it.

The outer edge of the Oort cloud is almost a full light year away from us.

That means light even crosses the boundaries of our own solar system in about a year. But what lies beyond that boundary?

The closest star to us, not counting the sun。 is called Proxima Centauri。 and it's about four light years away.

This means that its light。 traveling toward us at that monstrous speed。 takes a full four years to reach Earth. And this is only our closest stellar neighbor.

To give you a true sense of the distance。 I'll give you one example.

The fastest spacecraft ever built would need tens of thousands of years to reach this closest star.

The space between the stars turned out to be truly desolate and utterly unimaginable in its size.

Our sun seems simply enormous to us。 but there are stars in the universe next to which it appears like a tiny spark.

Take Sirius, the brightest star in our night sky.

It is noticeably larger and heavier than the sun。 and shines many times brighter.

But even it is still quite modest by stellar standards.

There are super-giant stars living out the final stages of their lives which have swollen to truly monstrous sizes.

One of the most famous is Betelgeuse。 a red super-giant with a diameter hundreds of times larger than the sun.

If we placed it in the place of our sun。 it would engulf the orbits of several planets. But that's not the limit.

In our galaxy, there is a giant star in the constellation Scutum。 which is approximately 1,700 times larger in diameter than the sun. Billions of suns could fit inside it.

If such a star were placed in the place of our sun。 its hot surface would extend far beyond the orbit of Jupiter。 engulfing the inner planets, including Earth.

And there's an even more monstrous contender for the title of Largest Star, known as Stevenson.

It's estimated to be more than 2,000 times larger than our sun.

It would take several hours for a beam of light to orbit such a star。 whereas it would circle the sun in a matter of seconds.

Such are the giants against which our small, humble luminary exists.

And crucially, all these super-giants are extremely short-lived by cosmic standards.

Burning through their fuel at a monstrous rate。 they are doomed to end their lives in a spectacular supernova explosion in just a few million years。 briefly blazing brighter than an entire galaxy.

Our quiet sun, however, will continue to shine quietly for billions of years to come.

All these luminaries, our sun and distant giant stars。 are gathered together in a single colossal stellar system we call the Milky Way Galaxy.

And here, the scale takes another dizzying leap.

Our galaxy is about 100,000 light-years wide. Just imagine that.

Even light, the fastest thing in the universe。 would take 100,000 years just to cross it from one end to the other.

And yet, we just discovered that it takes light only four years to reach the nearest star.

This gigantic stellar disk, slowly rotating in the void。 contains several hundred billion stars。 and many of them have their own planets.

Incidentally, our sun, along with all of us。 completes a full orbit around the center of the galaxy in about 200 million years.

Since the time when dinosaurs roamed the Earth。 we haven't even completed one such cosmic circle.

Our sun, along with the entire solar system。 is lost somewhere on the distant outskirts in one of the galaxy's spiral arms。 far from its bright and dense center.

If you tried to find our planet in a photograph of the entire Milky Way。 you would be completely unsuccessful.

Earth would appear to be much smaller than a single dot。 smaller than the tiniest grain of light in this grandiose picture.

To get a feel for these numbers。 let's use a simple mental model.

Imagine taking our entire solar system。 from the sun to the orbit of distant Neptune。 and shrinking it down to the size of a coin in the palm of your hand.

At that scale, our entire vast Milky Way would be the width of an entire continent.

Just imagine, the entire solar system。 with its planets, comets, and Oort cloud。 compressed to a tiny circle in the palm of your hand。 while the galaxy itself stretched for thousands of kilometers.

And that's just our own galaxy。 just one of countless others.

And beyond that, structures await us that will make even the Milky Way itself seem like that insignificant coin. It would seem impossible to imagine more.

But the Milky Way is only one of countless galaxies.

Our nearest large neighbor is called the Andromeda Galaxy.

It is roughly twice the size of the Milky Way and contains about a trillion stars.

Its distance is about 2.5 million light-years.

This number is so vast that it almost loses all meaning to us.

And yet, on a clear, moonless night。 Andromeda can be seen even with the naked eye as a tiny, hazy speck. But here's what's truly astonishing.

The light that now reaches our eyes from it began its journey two and a half million years ago before modern humans even walked Earth.

In other words, we see Andromeda not as it is today。 but as it was in ancient times.

Moreover, this galaxy is slowly but surely approaching us。 and in a few billion years。 our two-star systems will merge into one.

Along with several dozen smaller galaxies。 the Milky Way and Andromeda form the so-called Local Group。 our closest galactic neighborhood.

Interestingly, Andromeda is actually noticeably larger than the full moon in our sky.

We simply don't see it in its entirety because it's too dim for the human eye.

If it were even slightly brighter。 a huge, glowing spiral cloud would grace the night sky.

But the Local Group is only a small part of a far more grandiose formation.

Thousands of galaxies, including our own。 combine into colossal clusters。 which in turn gather into enormous superclusters.

Our Local Group is part of the Virgo Supercluster。 whose diameter is already approximately 110 million light-years.

And among this multitude of galaxies。 there are true monsters.

Our Milky Way, for all its magnitude。 looks quite modest in comparison.

There are giant galaxies that contain hundreds of times more stars than our own.

The diameter of the largest of them。 according to various estimates。 can reach almost a million light-years.

That is, several times larger than that of the Milky Way.

The stars in such ancient galaxies are much older than our sun。 and at their very heart, as a rule。 lurks something monstrous and invisible。 an object worth discussing separately.

To give you an idea of the scale of such clusters。 the largest of them can contain thousands of galaxies。 each containing hundreds of billions of stars.

And this entire gigantic family is held together by a common force of gravity. We're talking about black holes.

A black hole is a region of space where matter is so tightly compressed that even light cannot escape.

Ordinary black holes are born at the very end of the lives of massive stars。 but in the centers of large galaxies lurk true giants。 so-called supermassive black holes。 whose mass can be millions。 even billions of times greater than that of our sun.

And among them, there are absolute record breakers.

One of the most massive known black holes is named Thon。 and is located many billions of light years away.

Scientists estimate its mass to be tens of billions of times the mass of our sun. Just think about that.

A single black hole can weigh more than all the stars in our Milky Way combined.

Hot disks of matter orbit these objects。 and their monstrous gravity warps space and time itself.

They are among the most formidable and mysterious inhabitants of the entire universe.

Moreover, a black hole like Thon is so enormous that its own dimensions are several times larger than our entire solar system。 up to the orbit of Neptune.

And yet, even these are mere dots compared to the colossal structures we are moving toward.

Incidentally, the closest black hole to us is only a couple thousand light years away。 and poses no threat to Earth.

To seriously disturb our system。 it would have to come thousands of times closer。 and the boundary beyond which even light disappears is called the event horizon.

Anything that crosses this invisible line vanishes forever. We're climbing another rung of the cosmic ladder.

It turns out that the Virgo supercluster。 where we live。 is itself just the outskirts of an even more colossal formation.

It's called Laniakea。 and it's essentially our supercluster of superclusters.

It contains about 100,000 galaxies。 and its diameter reaches approximately 520 million light years.

All these countless galaxies, including our own。 are slowly converging on the common gravitational center of this colossal formation。 a mysterious region that scientists have dubbed the Great Attractor.

The most intriguing thing is that we still don't really know what exactly lurks on the other side.

This region is partially obscured from us by the dense disc of our own galaxy。 making it extremely difficult to directly see.

We only sense its colossal pull。 and that's what's truly astonishing.

Right now, at this very second。 our Milky Way, along with the entire solar system。 and you。 is hurtling through space toward this center at a speed of about 600 kilometers per second.

We simply don't feel this rapid motion because it is completely smooth and constant。 and there are no fixed landmarks around us by which to observe it.

Scientists were able to determine this by studying the faint relic radiation left over from the very first moments of the universe.

So, as you listen to these words。 you are actually taking a dizzying flight through space. However, there is an interesting twist.

Due to the mysterious dark energy pushing the universe apart。 our supercluster will likely never have time to come together.

The space between galaxies is stretching faster than gravity can pull them together.

But even Laniakea。 for all its unimaginable size。 is far from the limit.

If you look at the universe on the largest scale。 it suddenly ceases to be uniform.

Galaxies and their clusters are not scattered haphazardly。 but rather gather into gigantic threads and walls with colossal voids gaping between them.

This entire colossal web is held together largely by invisible dark matter.

Our distant ancestors could not have imagined that such a grandiose architecture lay hidden behind the familiar constellations.

Our Laniakea is just a part of one such thread。 which likely stretches for more than a billion light years.

Astronomers have given this colossal formation a resonant name。 calling it the Pisces Cetus supercluster complex.

Our own Virgo supercluster occupies only a small fraction of it。 but even that pales in comparison to the largest known structure in the entire universe.

We're talking about the Great Wall of Hercules and Corona Borealis.

This unimaginable cluster of galaxies stretches for approximately 10 billion light years.

It's practically impossible for the human mind to comprehend such a thing. It's simply mind-boggling.

Light traveling from one end of this wall to the other would take longer than the existence of our Earth and the Sun combined.

This single structure occupies a significant fraction of the entire visible universe.

Moreover, the very existence of such a huge structure is so astonishing that it forces scientists to question and re-examine some of their ideas about the structure and evolution of the universe.

It is believed that in the billions of years since the birth of the cosmos。 gravity simply wouldn't have had time to assemble such a colossal formation。 and the fact that it exists remains one of the true mysteries of modern astronomy.

Before reaching the very edge。 it's worth realizing one astonishing thing.

When we peer into the depths of space。 we are simultaneously peering into the past.

After all, light from distant objects takes millions and billions of years to reach us。 meaning we see them not as they are now。 but as they were long ago.

In essence, any powerful telescope is also a veritable time machine。 and the further we peer, the more ancient the picture we see.

The most distant galaxies known to us are so incredibly distant that their light has been traveling toward us for almost as long as the universe itself.

We see them as they were just a few hundred million years after the birth of the cosmos.

It's entirely possible that some of the very first stars ever to flare up in the universe burn within them.

By gazing at these dim, distant spots。 we are essentially looking back to the youth of the universe。 to a time when neither our sun nor earth existed.

And so finally we reach the very edge。 the boundary of everything we can possibly see.

This boundary is called the observable universe.

Current estimates place its diameter at approximately 93 billion light-years.

Within this unimaginable sphere。 according to various estimates。 lie anywhere from several hundred billion to approximately 2 trillion individual galaxies。 containing far more stars than the grains of sand on all the beaches and deserts on earth combined.

Each of these galaxies is, in turn。 an entire island of hundreds of billions of stars。 and countless of them likely have their own planets. But this raises a logical question.

The age of the universe is estimated to be approximately 13.8 billion years.

How then do we see objects whose light has traveled much longer to reach us?

The answer is that space itself is constantly expanding。 stretching in all directions at once.

While the light from distant galaxies has been traveling toward us for many billions of years。 the galaxies themselves have traveled even further away from us.

This is why the observable universe turns out to be much larger than one might think。 based only on its age.

We see not where galaxies are now。 but only the light they emitted in the distant past.

There is another reason we cannot see beyond this limit.

Light from more distant objects simply hasn't had time to reach us during the entire existence of the universe.

Over time, as the cosmos ages。 light from increasingly distant galaxies will reach us。 but light from many others will never reach us due to expansion.

But even the observable universe is far from the entire universe.

It is only the fragment from which light has managed to reach us.

Beyond this boundary, space almost certainly continues。 and we simply don't know how far.

By the most conservative estimates。 the entire universe is at least hundreds of times larger than its visible part。 and it is quite possible that it is completely infinite. We don't even know its exact shape.

It could be flat and infinite。 or it could close in on itself。 like the surface of a huge sphere.

We will never see those distant edges。 because their light is physically unable to reach us.

It is entirely possible that somewhere out there。 beyond the visible。 there exist countless other galaxies。 stars, and worlds that we will never know about.

This thought is both fascinating and slightly alarming.

And now, having come this long way。 let's remember where we began。 with our seemingly enormous Earth.

But it's just a speck of dust next to an ordinary star lost in one of the arms of one of hundreds of billions of galaxies。 gathered into the threads and walls of the vast cosmic web.

How unimaginably dizzyingly small we are against all this.

And yet there's something truly astonishing about it.

After all, we, tiny inhabitants of an insignificant speck of dust。 have proven capable of grasping this entire abyss with our minds。 measuring it, and at least partially understanding it.

Perhaps this is precisely where our true, incomparable greatness lies.

After all, to contain this entire abyss in thought。 you don't need to be greater than it.

It's enough to be able to ask questions and seek answers.

And so, the next time you raise your eyes to the night sky。 you will no longer be able to look at the stars in the same way.

Behind each of these tiny dots lies a whole universe of distances。 and we ourselves, despite our smallness, remain, perhaps。 the only ones in all this immensity who are capable of admiring it all.