If we take the earth and shrink it down
to the size of this bead, viola we have a
black hole .Black holes are the remains
of supermassive stars that warp
space-time so much that nothing can
escape it ,not even light .That's why
black holes are the only place in the
universe where we can see things behind
us but not in front. But what are black
holes really good for other than just
gobbling up matter ,well they are a whole
lot useful .Firstly, it is no coincidence
that almost every galaxy has a
supermassive black hole at its center,
the shape of the galaxy depends upon the
presence of the black hole, and the speed
of the rotation of the stars around the
galaxy depends upon the mass of the
black hole.All of this provides more
than enough proof that this some sort of
relationship between black holes and the
galaxies. To understand this better we
need to go back in time to the formation
of the first stars .These stars were
really massive as they were made of pure
hydrogen and helium ,so they died quickly
and left behind supermassive black holes.
These black holes had two phases of
their lives-
one the quasar phase in which they fed on
the small group of stars or incomplete
galaxies, and due to their enormous
gravity
brought together the stars forming the
first galaxies .Then they would enter
into the dormant phase giving time for
the galaxies to create many more new
stars. But can't the stars just come
together by themselves? Do they always
have to rely on a black hole?
to answer this question we need to
understand the two forces acting on
stars- one is their gravitational energy
which causes them to come closer and the
other is the expansion of space-time
between them which causes them to move
away from each other .Since the gravity
of the Stars alone is insufficient of
getting them close enough to form
galaxies, only black holes with their enormous
gravity can bring together all the stars
thus forming galaxies. Black holes not
only form galaxies but also establish
their stability. Take for example our own
milky way. It it has the black hole
Sagittarius A* at its center and all
the stars revolve around it.
If not for it, the stars would collide
with each other resulting in huge
turmoil .Black holes can even hold
galaxies together resulting in the
formation of clusters and superclusters
both which are very much essential for
creating a closed environment, else the
matter would escape into deep space
being completely useless for the
universe. It is astonishing how something
as small as singularity could affect the
universe in such a weird and mysterious
way, indeed even though they destroy, they
create, sustain and coordinate various
systems without whose presence the
universe would definitely be a different place. Thanks for watching.
