Biggest Black hole
A very daring idea has emerged in recent years: we may
be living within a black hole! Some scientists have suggested that the
entire Universe is a huge black hole, of rather different kind. It is not
surrounded by an event horizon, but curves back on itself like the surface
of the balloon. The result is the same: you cannot escape. The Universe
has no central singularity. Instead, it had a singularity in the past,
the Big Bang in which the Universe began - and it may collapse back into
a singularity in the future, the Bog Crunch. The theory can actually create
a new universe.
In the Beginning
No one knows what caused the Big Bang: it may have been
a fluctuation out of the literally nothing. Fractions of a second afterwards,
the temperature and density in the cosmic fireball were almost infinite.
In the inferno, dozens of strange particles were created which, as the
Universe cooled and expanded, formed the neclei of the first atoms. Around
2 billion years later, these clumped together to make quasars - violent
young galaxies with black holes in their hearts. Meanwhile, the Universe
continued its expansion.
In the End
After perhaps a million million million years, gravity
will draw everything in again - the Big Crunch. About a year before, galaxies
will collide, and the temperature of space will rise to higher than the
surface of a star. An hour before, supermassive black holes in the centres
of galaxies will merge and the Universe will dramatically collapse into
a point of infinite density.
Born to a black hole
Far from being merely cosmic sinks, black holes may give
to other universes. "Baby" universe may "bud" off black holes to grow as
universes in completely different dimensions with totally different properties.
Depending on the amount of matter in each unverse, they will expand and
contract, and prodoce still more universes along the way.
Deliberately created
Black holes and Big Crunches can both provide "budding
sites" where new universes can start. From one universe, they can spawn
a network of independent universes. Although each baby universe is different,
it will inherit some of its parent's "genes". This may how our Universe
came to be. American cosmologist Ed Harrison even suggests that our Universe
is so ideally suited for the development of intelligent life that it may
have been created by an advanced civilization in another universe. Perhaps
the scientists in that universe reached the stage of making black holes
in the lab, and one budded off to become our Universe. We may be juct the
result of someone's experiment!
From Big Bang to Big Crunch
If our Universe is a black hole, then it has a finite,
and predictable, lifetime. At the Big Bang, the Universe starts expanding
- shown here (not to scale) as a series of inflating balloons. The galaxies
and other constituents of the Universe lie on the skin of the balloon,
which represents space and carries the galaxies apart as it swells. The
history of the Universe is shown on successive strips of the balloons.
The Universe expands until it reaches its maximum size; then gravity wins
over the momentum from the Big Bang. The Universe begins to contract. The
galaxies move closer together and collapse into another singularity - the
Big Crunch.
Dark Matter Applies the Gravitational Brakes
The fate of the Universe depends crucially on how much
matter it contains. Too little, and there will not be enough to exert the
gravitational pull needed to "brake" the growth of the Universe; it will
expand forever. With sufficient matter, it will recollapse. Adding up all
the visible matter in the Universe gives only 10 per cent of the mass needed
to apply the brakes. But astronomers have evidence that the Universe contains
huge quanties of "dark matter". Perhaps 90 per cent of it consists of this
invisible matter, which could comprise exotic subatomic particles or even
vast numbers of black holes.
|
The NGC 2300 cluster of galaxies is embedded
in a gas cloud (coloured magenta) weighing 500 billion Suns. The gravity
from a vast amount of dark matter must be holding the gas cloud together. |
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the Black Hole in Galaxy
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