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We
should remember Einstein’s general relativity theory and
the field concept to understand more about the nature of
the black wholes. Because, the universal
attraction force isn’t a value depending on the force
and the distance between two masses like Newton has stated.
It is the curved
space formed by the
celestial body which is the source of
this force. In other words, the attraction field around
the body appears by the curving of the
space and time structure.
We
can visualise this in our mind in the following
way : Let
us think that the space is a two dimensional surface having
a width and a length like a bed sheet and with a friend
let us hold it very
tight and straight from the two ends.
Now, when an apple is put on that tight surface, it causes the
sheet to loose its straightness and the apple will collapse into
a third dimension around itself.
The sheet will collapse more and the tightness
in our hands will increase when we place a watermelon
instead of the apple.because of its weight weight.
When we replace the watermelon with a shot,
the surface of the sheet will collapse so much
that it will be difficult to hold it anymore,
because the bodies curve
and bend the surface in proportion to their masses. The
sheet will be torn apart if the shot ‘s weight is more than
the limit of the sheet’s resistance.
When
we think of these
examples in terms of space
time; as soon as a part is torn apart,
it will join
another region of the universe (the sheet)
or will establish a contact with the structures (the
other sheets) which are described as separate universes in the
shape of a funnel.
However, when we
throw a small marble onto that sheet, it
will move ahead in the two dimensional surface,
but it will be hard to make a circular motion around the
tiny pit it has formed and the sloping surface it has created in
the third dimension.
Now, if we think of
the Sun as the watermelon which is put onto the sheet and
the World as the marble, we
can see that our planet earth has a direct motion in the three
dimensional space. However,
due to the curvedness
towards the fourth dimension, it moves in a circular
motion and this causes us to perceive as if there is a force of
attraction between them.
In other words, the
attraction appears in the form of a curve.
Therefore, matter
determines how space-time will bend, and
the space-time
net determines how matter will behave.
Besides,
the light rays that go through the curved space-time diverge
from their way and they become twisted. This is the
reason why during the eclipse of the Sun the stars that we can
see near the sun are perceived as if they have deviated from
their real places.
However,
another characteristic of the space-time curve is that (like in
the theory of relativity),
the alterations of physical concepts depending on the
speed also occur under an
attraction force equal to that speed.
This is similar to the measurement
results that we have regarding the mass of matter.
When the matter is close to the speed of light , it has a
certain mass. This
is equal to the mass when the matter is being exposed to an
equivalent force of attraction (without
speeding up the mass)…
Therefore,
we can say that according to the eye of the observer, the time
slows down where the curving
of the space-time is high.
In other words, deep in the space clocks far away
from all the attraction sources go with a normal speed,
but when they get closer to where the attraction is
dense, the clocks
go slower than normal because
of the attraction
caused by the curving. It is proved experimentally that the
clocks placed at the lowest
floor of a
building go slower than the ones placed at the higher
floors like the
clocks getting
further away from
the earth.
In
the light of all the above, if we return back to the black
holes, the collapsing accelerates
the attraction force between the particles which make up
a star. It
becomes more stronger.
Within seconds,
the volume of the star becomes unusually smaller
by the joining of electrons, protons and neutrons with
each other. The space-time
curve around the
star increases more as the attraction force makes the volume of
the star smaller. As a result of this, the rays that depart from
the surface of the star start to curve more. At the end
of this twisting stage there comes a very critical stage
where all of the rays return back to the surface of the star
again. As
these rays, no matter from which direction they come, cannot be turned back by the curved space-time,
the star suddenly becomes jet black. So, nothing can
escape from the star to the external universe anymore,
as nothing can move faster than light ( but , this is
true for the universe that we perceive). In the end, the
attraction becomes so powerful that the star disappears from the
universe entirely.
The
critical radius where the light can’t escape is called the
event horizon, and the largeness where the star will collapse
and become a black hole is called the ‘’schwartzchild
radius’’.
However, there is
no way to understand what is really happening behind the event
horizon. You can’t communicate with anybody behind it. (A
message goes but never comes back.) Because that place is
abstracted from our space-time, it isn’t a part of our
universe from now on and the star continues to collapse under
the event horizon aimed at gathering all of its mass to a zero
volume in the centre and to a point of IMAGINARY ONENESS with an
eternal density.
The
density of a black hole depends on its mass.
If the Sun could become a black hole, its schwartzchild
radius would be 3 km, for the Milky Way Galaxy
which has mass 150 billions times more than the Sun, it
would be 450 billions km and if enough material could be
found to make the whole universe
a closed one, its radius would be 300 billions of
light-years.
Besides, in order to
form an artificial black hole, it would be necessary
to compress 1600 tons of iron into a space which is 100
millionth of a cm.
If it could be possible to compress the whole mass of the World
into a marble with a radius of 1 cm, we would have increased the
density of the world that is 5 gr per cubic centimeter (where
the density of water
is 1 gr per cubic centimeter)
trilliar times more. The interesting point about this is
that the Moon can still continue to turn around the World even
under these conditions. A person on the Moon would never see the
marble, but he would be able to feel the attraction. In the same
way, when the Sun
will become a white dwarf and
swallow the planets
close to it, the
outer planets will carry on moving in their orbits.
Because,
the important thing in the universe is the mass not the volume.
That is to say, no matter how big the volume
is, if the density of an object is
low, then it would be
carried away by the attraction of
a smaller mass which has a higher density.
However, for
a star that is three times bigger than the Sun,
the process of collapsing takes
67 millionth of a second, for a star
ten times bigger it takes
4 millionth of a second and for a star which
is a million times bigger it
takes one fourth of a second . This
is a quite long period.
To
perceive more deeply about the nature of black holes, let us
imagine that there is a stationary spaceship and a separate one
which is sent to the black hole. Let us also imagine that there
is a person in the space ship travelling towards the black hole
and another one who watches from the outside and find out
how they would perceive
each other and their surroundings.
Also let our observers, both
the stable one and the travelling one send to each other
a blue signal in every second. At first, the outer observer
doesn’t recognize anything
and he continues getting
signals in response to his signals in every second.
(Because changes will occur when the ship is
closer to
the speed of light .) However,
as the moving one comes closer
to the black hole, the intervals between
the signals coming to the outer observer start to
increase slowly and the wave length of
the blue coloured light slides towards to red and it is
seen as red. This
is the effect of the
force of attraction on the photons. Thus it decreases their
energy. This
is similar to what is stated
in the law called the Doppler
effect; where
the rays sent by
objects going away from us in the expanding universe become red
because of the speed.
In other words, as
the space ship comes
closer to the event horizon,
the outer observer obtains the signals corresponding to every
second at increasing time intervals.
When the ship comes to the border
of the
event horizon, the expansion in
time extends to an eternal period of time in response to
one second (whereas time has stopped from now on), and the
observer perceives
the frozen image of the ship in this space-time net. (*)
Now,
let us see how the observer in the ship perceives the
outside. First, he
travels without any
abnormal event. However, as
the attraction force
increases (the wavelength of the coming signals shorten and slip
to the colour profiles above the blue) he starts to see edges of
the objects which he had already left behind
in front of him…..
To
be continued……..
Istanbul-
November
02th 2000
http://afyuksel.com
(*)
In these kind of expositions to understand the subject more
sufficiently generally one or two parameters are taken into
consideration, the rest can be undervalued.
Time is an
example for this. However,
in order to realize the occurrence exactly, all parameters should be kept in mind. (see Sufism&The
Human; Physics section/the nature of the time)
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