the ultimate abyss
It used to be thought that the world
was flat. That beyond the horizon lurked a bottomless void, measureless
to humans. As our ships got better and our navigators more confident,
vessels that disappeared over one horizon began returning triumphant
from the other. The Earth was curved, a sphere with no edges. We
didn't fall off because a mysterious force called gravity kept everyone
and everything stuck to the planet's surface.
Then Albert Einstein came along and told us that space itself was
curved. Now we realise that if we sail off into the sea of curved space
we call the Universe, there are indeed bottomless voids that the unwary
traveler can fall into - and they are measureless to humans. They lurk
on the other side of their own dark horizons, and we call them Black
Holes.
FATAL ATTRACTION
A black hole is an astronomical contradiction - a dark star, an
invisible nothing, a prison of light. Its boundary is marked by the
so-called Event Horizon, a sphere of darkness that shrouds the
inside and defines the point of no return. There is no solid surface
beyond, just a bottomless gravitational whirlpool so strong that it
sucks everything - even light - relentlessly inward. Oblivion waits at
the centre in the form of the Singularity, Gravity’s fatal attractor.
Hidden eternally from view, the Singularity marks the spot where an
immense gravitational force has been concentrated. All the mass, light
and energy that has ever fallen into the black hole is compressed by its
own overwhelming gravity into a point that is infinitely small and
infinitely dense. The more a black hole swallows, the heavier it gets,
yet the singularity never changes. Space has been squelched out of
existence and Time has been squeezed to a stop. Step over the event
horizon and for all intents and purposes you’ve fallen off the edge of
the universe.
A BRIEF HISTORY OF GRAVITY
The concept of Gravity, this unseen force that dominates our lives
and pulls us eternally towards the ground, has long challenged the
greatest human minds. Even in Galileo's day, the tower at Pisa had a
good lean to it - perfect for dropping things off. Galileo wondered why
no matter how heavy or light objects were, they all took the same
amount of time to fall to Earth. He puzzled too about why the planets
moved they way they did. His conviction that they orbited around the sun
led to house arrest for heresy. He was still trying to put the gravity
puzzle together when he died in Florence in 1642.
On Christmas Day that same year, the gravity baton was handed to
Isaac Newton, born weak and premature in a Lincolnshire farmhouse.
Twenty three years later, Newton returned to Woolsthorpe Manor to sit
out the plague sweeping southern England. With 18 months quiet thought
in the countryside he discovered calculus, unravelled the nature of
light, and began formulating laws for the motion of the planets:
discoveries that still underpin most of modern physics. One day when he
was having a short break with a cup of tea, a falling apple interrupted
his thoughts and led him to ponder gravity itself.
The reason the apple fell straight down was that it was trying to
fall to the centre of the earth where gravitational attraction was
focused. And the Earth wasn’t the only object that had gravity, so did
the moon, the sun and the planets. In fact, Newton reasoned, every
object in the universe - including ourselves - has gravity. The bigger
and heavier, the greater it’s gravitational force. We are glued to the
surface of the Earth - and not the other way round - only because it is
has so much more mass. The Earth orbits around the sun for the same
reason. Finally, Newton had found a reason for the heavens to move the
way they do.
DARK STARS
In 1784, John Michell, Rector of Thornhill Church in Yorkshire and
great forgotten 18th Century scientist, became intrigued with the idea
of escape velocity - the minimum speed with which you need to travel
upwards from a star or planet to escape its gravitational clutches. He
knew that gravity depended upon mass and he knew the speed of light was
fast but finite. How heavy, he wondered, would the sun have to become
before its gravity would become so great that even light (which travels
at 299,792 km/second) would be held back at its surface? The answer,
Michell reasoned, was that if the sun was the same size but weighed 500
times more, the light from the Sun would not escape the Suns own
gravity. The Sun would simply disappear from view. A few years later
the great French mathematician Laplace came to the same conclusion
independently. The concept of the Dark Star was born.
A UNIVERSE OF HOLES
Black holes remained an ignored theoretical curio until a young clerk
in a Swiss patent office published his General Theory of Relativity in
1915. Albert Einstein realised that the universe was a fundamentally
different place to the clockwork universe of Newton and commonsense.
The three dimensions of space could not be separated from the fourth
dimension of time. Together they form the ‘Spacetime’ continuum, a kind
of invisible scaffolding that defines existence. Spacetime, though, is
not an absolute, fixed thing. It can be warped, bent and curved.
Spacetime is ‘straight’ only when it doesn’t have anything in it.
Wherever there is mass, there is gravity. Wherever there is gravity,
space is curved. The curvature of space dictates how an object will move
through it. The object will dictate how space bends around it. Gravity,
according to Einstein, is the curvature of space.
Einstein’s thought experiment was to imagine space and time being
squashed flat like a 2D rubber sheet. Put a massive object like the sun
on the sheet and it will bend. The more dense an object is, the deeper
the depression it makes in Spacetime and the stronger the gravity.
Eventually a point is reached when the walls of the depression are
stretched so steeply that nothing can climb out of it. It is, quite
literally, a hole in the universe.
A STAR IS BORN
To understand the very large in the universe, you need to start with
the very small. With the unlocking of the secrets of nuclear energy,
scientists finally got a clue to how black holes might form in nature.
Stars are born when enormous clouds of cosmic dust and hydrogen begin to
clump and condense under their own gravitational weight. Gravity grows
stronger by the hour as the increasing density of the protostar curves
space more strongly. Faster and faster, the hydrogen gas falls in upon
itself in the condensing core. The more it collides the hotter it grows.
When the core reaches 10 million degrees, the hydrogen protons begin to
fuse into helium. Some of the mass disappears, having being turned into
energy and light. Like a giant cosmic light bulb, the star has switched
itself on.
Every star we see in the heavens has a giant nuclear reaction raging
at its core. It’s what makes a star like our sun shine so hot and
bright. Gravity is still trying to pull the star’s gas tighter and
tighter but is matched now by the energy pouring outwards from the
nuclear reaction in the core. The star settles into a precarious balance
that gravity will always win in the end.
THE BIG SQUEEZE
The ultimate fate of a star depends upon its mass. Our sun is
middle-aged. It switched on 5 billion years ago and has enough fuel to
burn for 5 billion more. But when, in that far distant future, the
spent heart of the sun sheds its outer layers and shuts down, gravity
will squeeze the core so tight it cannot be squeezed any more. It will
become a ‘white dwarf’, a feeble ember the size of the earth but a
hundred thousand times more dense.
The more massive the star is, the faster it burns its fuel and the
shorter its life expectancy. A star 10 times as massive as the sun may
survive only millions, not billions, of years. As it starts to collapse,
the crush of in-falling matter slamming into the iron core sends the
temperature rocketing to 50 billion degrees. The core has only seconds
to respond - and it does so Supernova-style.
A supernova is a massive explosion. Huge quantities of material are
blown into space, but only from the outer regions of the star. Most of
the star has actually imploded, with the core being given a gravity bear
hug so extreme that the protons and electrons have been squeezed into a
ball of superdense subatomic particles called neutrons. The resulting
‘neutron star’ would weigh about one and a half times as much as the sun
but would measure only about 20 kilometres across - about the size of
Brisbane.
Astronomers can prove that neutron stars exist, because they give off
a unique distress signal. Like a lighthouse warning of a dangerous
shore, a neutron star sweeps space with a blinding beam of radiation,
generated by a magnetic field more than a trillion times greater than
the Earth’s. Such a neutron star is called a pulsar. To astronomers,
the pulsing beam sweeping the darkness of space is an unmistakable
warning that extreme gravity lurks nearby.
GRAVITY'S FINAL TRIUMPH
A neutron star resist the ongoing crush of gravity, only with its
neutrons packed in like sardines in a tin. But if the remnants of the
star after supernova weigh more than three times the mass of the sun,
even neutrons cannot hold back the inexorable force of gravity. The
neutrons are squashed into oblivion. The star’s core becomes so dense
that gravity overwhelms space itself, distorting it so horribly that it,
and time with it, is wrenched off from the outside universe. A
darkness forms at the star’s heart and moves relentlessly outwards as
the stars brilliance is sucked inwards. This is the hungry, growing maw
of a black hole: gravity’s final triumph. There is no escape, no
turning back, until the entire mass of the star has been swallowed and
its brilliance completely extinguished.
A BLACKNESS BEYOND BLACK
Visible only by its invisibility, the margin of the black hole is
marked by the event horizon, so-called because all events beyond are
hidden from view. For a black hole like this the event horizon may be
only a few kilometres in diameter but the void beyond impossibly deep to
measure. The entire mass of the star has been reduced to a singularity
- a point of infinite smallness and infinite density at the very centre
of this black malevolence.
The singularity is where science ends and speculation begins. Space
and time have ceased to exist, replaced by a seething chaotic mass we
call quantum foam. This bizarre conjecture is where Einstein’s laws
fail. This is where the laws of quantum mechanics fail. This is the
realm of something called Quantum Gravity - one of the hottest areas of
advanced mathematical research.
It is from a singularity that the Universe is believed to have begun.
In many ways the collapse of a star to form a black hole singularity
is the reverse of the Big Bang. Is this the way the Universe is going
to end? Wilder speculation is that our entire universe might lurk
inside someone else’s singularity. or even that universes can bud off
from each other like this, like some sort of heavenly breeding organism.
It wasn’t until 1967 that John Archibald Wheeler slipped the term
"Black Hole" into his paper at a scientific conference, and into the
lexicon of the late 20th Century. They may have become a household name
- but are they real?
BLACK HOLE OR WHITE ELEPHANT
Einstein himself couldn’t believe that such an invisible
impossibility as a black hole could exist in the real universe beyond
his theories. Today, his successors have no such problems. Astronomers
not only think they have identified nearly 30 black hole candidates in
our own Milky Way galaxy, they are now getting the proof that the holes
behave in the relativistic way that Einstein’s theories predict.
A black hole is an elusive quarry with perfect camouflage: total
blackness in the blackness of space. Searching for a black hole no
bigger than Sydney’s CBD across hundreds or thousands of light years of
space demands a sneaky approach. First you have to find a visible star
that a black hole has trapped in orbit. Then you have to study how the
star wobbles. John Wheeler described it as like looking for a pair of
dancers on a dark dance floor. The heavy man dressed in black is
invisible, but the bright white dress of a light women is an easy target
as she is whirled around. Astronomers look for the bright stars that
‘orbit’ dark partners in the same way.
One of the best candidates is the star called V404 Cygni.
Calculations shows V404’s dark partner is twelve times more massive than
our Sun, yet totally invisible. But for every black hole orbiting
another star, there must be many more solitary ones yet unseen. One of
these could lurk quietly much closer to home.
THE COSMIC HOOVER
Although black holes have the power to hoover up anything and
everything that strays too close, they can’t hunt. Contrary to popular
belief, if you replaced our Sun with a black hole of the same mass the
Earth wouldn’t get sucked in, there just wouldn’t be any sunlight. You
could even orbit a black hole in a spacecraft just so long as you kept a
safe distance.
Get too close though and strange things start happening. Space gets
stretched longer and skinnier. You would find your feet being pulled
miles away in front of you while your body is squeezed sideways. You
will have become a piece of space spaghetti long before you reach the
event horizon. Then you’d be ruptured into your own fundamental
particles and disappear behind the veil of darkness.
It’d be a spectacular way to go but no-one would see it because time
is being stretched as well. The photons carrying the image would
struggle harder to leave your body the closer you fell. Even with a few
million years to spare, an outside observer will see you slow to a halt
above the event horizon, before slowly fading from view.
HEARTS OF DARKNESS
Most astronomers now concede that a black hole heavyweight lurks in
the centre of our own Milky Way galaxy. Latest estimates are that it
weighs in at a whopping 2 million times the mass of the sun - a dwarf in
comparison to some of the truly supermassive black holes that may lurk
in the cosmos.
By the 1950s, astronomers began turning optical telescopes towards
some of the strongest signals that the new radio telescopes were picking
up. Source number 3C 273 was found to be a bright star-like object with
a 'jet' of intense radiation sticking out of it. It was the first of a
number of similar objects given the name of ‘quasar’ or 'quasi-stellar
radio source', but their real identity remained hidden for decades.
Quasars have now been revealed to be the energetic hearts of very
active galaxies: brilliant discs of superheated gas and ruptured stars
swirling at nearly the speed of light. Great jets of charged particles
are blasted thousands of light years into space from above & below -
like an axle through a wheel. The central engine that is driving all
this activity, though, is hidden deep inside. It has to be small and
it must be extraordinarily dense. The mathematics demand that the only
beast that can drive such a display of raw power is a supermassive
black hole. The heavier the hole, the faster the gases whirl in orbit.
Astronomers have observed speeds which tally with black holes weighing
up to five thousand million suns.
The theory goes like this: a galaxy evolves from a vast rotating
cloud of gas that begins to clump and condense under its own weight into
billions of stars arranged like an enormous Catherine wheel, a Mexican
hat or a bee swarm. In the centre, where the gas is concentrated,
enough matter to make millions or even billions stars has undergone
titanic gravitational collapse to make a supermassive black hole.
While the hole is still actively feeding on the inner part of the new
galaxy it manifests itself as a quasar. Later, when all nearby food has
been consumed, the black hole becomes quiescent, leaving a relatively
quiet galactic core like the one in the Milky Way. If this theory is
correct, then supermassive black holes are present in all but the
smallest galaxies.
TOWARDS THE WITHIN
For all their ferocity, these supermassive black holes are
surprisingly gentle giants up close. You can fall into one without
turning to spaghetti.
Suppose you or I were an astronaut about to step into such an abyss
at the edge of the universe. As I approach the event horizon, blackness
spreads upwards around me. The Universe shrinks to a bright point
directly overhead. As I meet and cross the horizon the universe above
disappears in a blinding flash of photons trapped in orbit around the
hole.
I am now inside the black hole and falling towards the
Singularity. It’s not dark like I expected. I see a ring of dancing
light where the singularity should be. It must be spinning so fast that
the centrifugal force has balanced out gravity. Now it’s a naked glowing
hula-hoop of indeterminate size. Around it I see glimpses of heavens
unimaginable to humans, universes within universes, time within time...
But hey! No matter what I might see or experience inside the black
hole, I could never send a message out. The secrets I discover will die
with me as I achieve oneness with the Universe, at the central
Singularity.
"Quasars have now been
revealed to be the energetic hearts of very active galaxies: brilliant
discs of superheated gas and ruptured stars swirling at nearly the speed
of light."
later on i will continue with all those function why human could spin of time even the years is goes forward but the world event is could be repeated i use the functional , religion, and some sufi books to approve it . base by my religion i choose , islam it self .
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