SCIENCE BEHIND WORMHOLES

Perhaps the most astounding aspect of our cosmos is its immensity.

What a vast universe we live in!

But this is also, arguably, the most frustrating feature.

Consider the fact that it would take centuries for us to arrive at another planet like Earth in a galaxy with the great telescopes we have at our disposal today.

In actuality, leaving this galaxy is not conceivable for any person.

The Earth's location inside the Milky Way Galaxy is now widely known.

Andromeda Galaxy is the Milky Way's nearest neighbor.

Distance from the Earth: 2.5 million light years.

So, if we want to travel there by spacecraft.

It will travel at its typical speed of 28 000 km/h.

it will take 94.5 Billion years to reach it.

Not only that, if we can somehow make the technology

travel at the speed of light,

it will still take 2.5 million years to reach there.

This is truly disappointing.

What is the point of finding all these planets

when we will never be able to travel there?

But if there were a shortcut

to travel outside the galaxy,

a shortcut through which

we can travel across million light-years

in a few months,

then these things become interesting.

These shortcuts, my friends, are

Wormholes.

The 2014 film, Interstellar,

my favourite space film,

I would like to mention it again.

In this film, it is shown that

when Cooper and his team leave Earth

in search of other habitable planets,

in search of other planets like Earth,

they travel to another galaxy.

From their galaxy to another galaxy,

they travel through a wormhole

in a matter of minutes.

This is the scene in the film when Cooper's team passes through the wormhole.

According to the film, this wormhole was discovered

near the orbit of Saturn by NASA.

It is mentioned in the film many times

because it plays an important role in the plot.

But the most interesting thing is that

this concept of wormholes is not science fiction.

In fact, it is based on real science.

What are wormholes exactly?

And how can we use them?

Before understanding all this,

we have to come back to Einstein's Theory of Relativity.

I talked about it in the video on Black Holes too

and explained the basic concept in that video.

Now let's go a little deeper into it.

When Albert Einstein wrote his Theory of Relativity,

he wrote it in a set of equations.

The set of equations

is called Einstein's Field Equations.

It was first revealed publicly on

25th November 1915,

when Einstein submitted his paper to

the Prussian Academy of Sciences in Berlin, Germany.

In total, these field equations are made up of 10 different equations.

10 non-linear partial differential equations.

But in short, they can be represented by only 1 equation.

And that equation looks something like this.

Don't worry, we won't go into the mathematical details in this video.

Because this one equation has a lot of complexity.

If you expand this one equation,

you can see these steps.

Even if you love maths,

you will get dizzy after seeing this.

Broadly speaking, these equations tell us

how matter and energy

influence the curvature of space-time.

Albert Einstein said that to visualize this,

we need to imagine a big mesh.

When you place objects on this mesh,

it bends down due to the weight.

The space-time mesh also bends in the same way,

it curves with the weight of big planets and stars.

The more the gravitational force of a planetary object,

the more the space-time mesh will curve around them.

Now the interesting thing is that Albert Einstein himself

was not able to solve his field equations completely.

He had just found an approximate solution to his equation

in a specific case.

The first person who solved these field equations

was Karl Schwarzschild in the year 1916.

He calculated exactly how much the curve of space-time

bends and to what degree

in case of a single ball of mass.

It was the solution by Karl Schwarzschild

which helped scientists understand the concept of Singularity.

What would happen if this mass

becomes infinitely dense?

The curvature of space-time would wrap around it so tightly

that this region would pinch off from the rest of the universe.

With this, the scientists

were able to theoretically prove the concept of Black Holes.

This was proven about 100 years ago.

Actually, decades later,

for the first time in 2019,

scientists were able to take a photo of a black hole.

So, basically, what I want to say is that

one of the solutions to these field equations was black holes.

Theoretically, we already knew about the existence of black holes

about 100 years before they were discovered.

And the thing is, friends,

that another solution to these field equations

is Wormholes.

You might be thinking how can we

solve one equation and get two solutions.

Well, you would remember studying quadratic equations in school.

This simple equation also has two solutions,

x=2 and x=3.

Both are correct.

So, if you see Einstein's field equations,

they are much more complicated.

Actually, there can be numerous solutions to these.

Wormhole is one suck solution

and its scientific name of the Wormhole solution is

the Einstein-Rosen Bridge.

This name is derived from Albert Einstein

and his assistant Nathan Rosen

who worked together and came up with this solution in 1935.

So it is very easy to understand wormholes.

It is basically a shortcut

which connects two points of space-time.

First, I will explain things in two dimensions

so that it is easy for you to understand.

Look at this paper.

There are two points, A and B, on this paper.

If you want to go from point A to point B

using the shortest route,

which route can it be?

The straight line that connects A and B.

There can be no shorter route in two dimensions

except the straight line connecting both points.

But if this two-dimensional mesh

is bent into three dimensions,

you will see new paths emerge.

I have bent A and B in such a way that

if you want to choose the shortest path to go from A to B,

then this distance of millimetres between A and B

can be used directly.

If I make a path here between these two,

literally, by inserting a pen,

then, literally, a shortcut has been found

to go from A to B,

which is much, much shorter,

as compared to this path.

Wormholes are also doing the same thing.

In our three-dimensional world, we think that

the shortest way to go from Milky Way Galaxy to Andromeda Galaxy

is 2.5 million light-years long.

But if our 3-dimensional space

is curved or bent into the 4th dimension,

then it's possible that we can find a shorter, better shortcut.

Now, it is very difficult for us to imagine the 4th dimension

because we all live in 3 dimensions.

But to some extent, you can understand it better

if you compare 2 dimensions and 3 dimensions.

I'll give you another example.

This is the world map.

If you want to go from Delhi to New York by flight,

what would be the shortest route of the flight?

You'd say, a straight line connecting Delhi to New York

with the flight flying over Africa.

But in reality, this would not be the shortest route.

Because you're thinking in two dimensions.

The shortest route would be

to travel over Finland, Sweden,

passing by Iceland and Greenland to reach New York.

Which on 2-dimensions looks like

a longer route unnecessarily flying to the North.

But if you look at it in 3D,

it looks obvious that

it is the shortest route.

In 1957, scientist John Wheeler published a paper

on Einstein's Rosen bridges.

He compared it with a similar analogy.

He gave an example of an apple

and an insect is eating that apple, a worm.

It reaches from one side of the apple to the other

while eating it or travelling through the middle.

Instead of travelling on the surface of the apple

like our aeroplanes travel

around the surface of the earth, Earth's circumference.

By doing this, the worm will travel a shorter distance.

In a way, it has taken a shortcut in space-time.

And this term was named by Wheeler as a Wormhole.

And this is where the word Wormhole originated.

When you search the word wormhole on the internet,

you get to see many such diagrams.

Basically, the same thing I did with the paper,

two points were connected through a hole.

Here, it is imagined that we have a space-time mesh,

on which there is an object with an extremely strong gravitational force.

So strong that the curvature of space-time has bent so much

that it has pierced through the other side.

The space-time mesh has folded on itself.

Just like I folded that paper.

And this wormhole has become a shortcut

to travel from one galaxy to another.

But in all these visualizations,

the problem is with the dimensions.

We try to represent a wormhole in two dimensions.

But as I said, wormhole works in 3D to 4D.

So in reality, if a wormhole exists,

it will look like a spherical ball.

There is a very interesting website where you can visualize

how wormholes will actually look like

if their existence is proved indeed.

A ball-like figure,

where, as you go inside,

everything that you see around you is curved.

And if you turn around and look,

the earth is moving away from you.

And everything will look in a circular shape.

That's why the wormhole shown in the Interstellar film

is depicted in a very realistic way.

Here, it is important to mention that

the concept of wormholes

for now, as of 2023,

is just a theoretical concept.

It has been theoretically derived as a solution to Einstein's field equations.

In movies, scientists have tried to visualize it.

Many theories have been formed about it,

but practically no one has seen a wormhole yet.

Scientists don't know whether wormholes really exist or not.

But if wormholes exist,

they will work as a time machine too.

Just imagine that you will be able to travel millions of light-years in a few minutes.

This means that you can reach there even before light.

If the light didn't reach there,

then basically you have jumped from one place in time to another.

Now it's a different thing that if wormholes do exist,

can humans even travel through them or not?

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Now, let's get back to the topic.

Many practical problems arise here

if wormholes are to be considered real.

The first question is how will the opening of the wormhole be formed?

We will need an extremely heavy gravitational force here.

Where can we find this gravitational force?

If you have seen my old space-related videos,

you can guess what the answer to this question is.

A black hole.

Einstein and his assistant Rosen theorized that

only black holes can have such a gravitational force

that they can open up these tunnels of wormholes.

Everything is attracted to black holes.

Everything will be attracted to it

and will flow through this wormhole

through this tunnel.

But the next question is

what will be on the other side of this tunnel?

If there is a black hole on the other side

then there will be no way to get out of this tunnel.

You will be trapped inside this tunnel.

Basically, in that case, this wormhole will not be a tunnel

to go from one place to another

but rather it will be a trap.

There should be something on the other side

which is the opposite of a black hole in every sense.

Something which is as powerful as black holes

but works in the exact opposite way.

Something that instead of attracting things towards itself,

sends things away from itself.

So that an exit point can be created.

And here, enters in our story, the white holes.

Once again, White Holes is a concept that

has been proved theoretically

by Einstein's Field Equations.

Apart from black holes and wormholes,

white holes are another solution to these field equations.

What are these white holes?

Like white is the opposite of black,

a white hole is the opposite of a black hole in every sense.

Like in a black hole, no light can escape

once it is trapped inside.

On the other hand, in a white hole, no light can enter.

It can only be emitted by it.

This means that the white hole will be extremely

bright and white in colour.

Russian theoretical physicist and cosmologist

Igor Novikov was the first person

to use the term White Hole in 1964.

According to scientists,

a white hole is basically a time reversal of a black hole.

Like the event horizon of a black hole

is a point of no return.

Once it is crossed, nothing can escape from it.

Similarly, the event horizon of a white hole

is a boundary of no admission.

Nothing can go beyond that point.

The objects inside the white hole

can go outside and interact with the outside world

but they cannot go back inside.

Even though this is a solution to Einstein's Relativity Theory,

no one actually knows how white holes will form in reality.

I explained the formation of black holes

in the video about black holes when

a star collapses on itself.

But what can be the opposite of this?

So, can a white hole exist or not?

This is the topic of discussion among scientists to date.

Some scientists believe that when Big Bang happened

and the universe was formed,

at that moment of creation,

everything must have emerged from a gigantic white hole.

Another theory is based on the idea by Stephen Hawking.

Stephen Hawking said that a black hole

will eventually evaporate when

radiation keeps leaking from it.

"Black holes are not eternal.

They evaporate away

at an increasing rate

until they vanish

in a gigantic explosion."

But when a black hole evaporates and dies,

what will happen to the information and matter inside it?

Quantum theory has a fundamental law

which states that no information can be lost.

It is called the No Hiding Theorem.

According to the No Hiding Theorem,

even if any information disappears from a system,

it would still be existing somewhere or the other in the universe.

Theoretically, if all this matter and information

is being sucked into a black hole,

it will be spitted out after the death of the black hole.

And this is likely happening through a white hole.

Based on this argument, many scientists say

that a white hole forms when a black hole dies.

But till now, we do not have any substantial information

about how a black hole dies.

On the other hand, some scientists argue that

it is theoretically impossible for a white hole to exist

because it violates the Second Law of Thermodynamics.

As you must have studied in school,

the second law of thermodynamics states that

the entropy in any system cannot be reduced.

Take this paper as an example.

If I tear this paper,

after the paper is torn,

the entropy is simply increasing.

Now, it is not possible to join it again in the same way.

The way a paper shredding machine

shreds the paper which increases the entropy

in the same way, black holes shred everything in the universe.

Black holes swallow the entire planets and stars

and only radiation is left behind.

This increases the entropy in the universe.

But if you try to imagine that

it is happening in reverse,

with the entropy decreasing,

this is not possible.

And if white holes do exist,

then essentially this is what they will aim to do.

So, as per this logic, perhaps they cannot exist.

But despite this, some scientists believe that

not only do white holes exist,

but that in 2006,

scientists saw a white hole.

On 14th June 2006,

a space satellite named Neil-Gehrels Swift Observatory

captured an astronomical event.

Scientists saw an explosion of a white light

which suddenly disappeared.

This event was named GRB 060614.

It was a gamma-ray burst.

Gamma-ray bursts are basically

are highly energetic explosions

observed in distant galaxies.

Usually, these events occur

when a black hole swallows a big star.

You can see very bright explosions of light.

But in this case, no evidence of a star was found.