When people say black holes we are reminded of this ferocious object which swallows and engulfs everything in its path but in reality if there was a sufficiently stable black hole in the near vicinity of the solar system you will hardly even its presence and it will barely change the night. It will be invisible although its effect would be felt you can’t see it with your eyes.
A simulated
Black Hole of ten solar masses as seen from a distance of 600km with the Milky
Way in the backgroundThe black hole was first predicted as early as the 18th century by the English
natural philosopher John Michell. He was the first one to propose that there
could be a star massive enough that even light couldn’t escape its
gravitational field. He called it ‘dark star' in a letter to Henry Cavendish in
November 1783. He thought that such ‘dark stars’ could be detected by the
effect of their gravity in the neighboring stellar masses but interest soon
faded after the wave nature of light was demonstrated by Thomas Young in 1800.
Although Michell may have been right in predicting the existence of black holes
far ahead of his time modern understanding frowns on his version of black holes
as supermassive stellar masses slowing down light particles until it starts to
freefall back to their surface. It was not until einstein’s time that the next
major advancement towards the idea of black holes was made. It was during the turn
of the time when Einstein published his theory of general relativity that the
first and the most important exact solution was found for a single spherical
non-rotating mass of no charge. It was derived by a German physicist Karl
Schwarzschild in 1916 while he was serving in world war 1 a little over a month
after Einstein published his theory of general relativity. He died later that
year and the solution was named after him called the ‘Schwarzschild solution'.
Although he died his legacy holds considerable weight considering he underlined
the peculiar behavior of the solution at a certain point now known as the Schwarzchild
radius. The most amazing thing about the Schwarzchild radius is that it says
that any mass can become a black hole if you compress it small enough and the
radius of the resulting black hole is given by the Schwarzchild radius. For
example, if the earth were to be compressed then all the mass of the earth
should be compressed to a few millimeters which is approximately the thickness
of a penny!
Black holes are very fascinating things in this universe. Black holes are formed when a massive star collapses in its gravity to the point where even light the fastest thing in this universe can’t escape. That’s where it gets its name from because it is basically black and invisible in plain sight.
This point of insane gravitational field is called a ‘singularity’. The singularity is a point where the known laws of physics breaks down and all our models aren’t any good here. What’s funny is singularity is not a physical thing but a mathematical concept to explain models that don’t converge and diverge uncontrollably. It is the mathematical way of saying we hardly know what we’re dealing with here.
.jpg)
The existence of singularity suggests that there are some significant
gaps in our understanding of this universe. Our present understanding of the
universe is by two broad theories based on completely different ideas ‘the
standard model’ and ‘the general theory of relativity’. The standard model is
based on the idea that any interaction between objects in this universe takes
place due to the exchange of particles between them. The standard model is an amazing
theory it describes everything in this universe that doesn’t involve gravity, from
‘why does your hair brown?’ to ‘how your brain works?’. It’s just wonderful to
a remarkable degree of accuracy. In contrast, the general theory of relativity
is described only for gravity, it is based on the fundamental idea that mass
curves space-time in its vicinity, and this curved space-time further
influences the motion of other masses. To simply put it in einstein’s words
‘mass tells space how to curve and space tells matter how to move’ it’s a
revolutionary idea.
The problem faced by many physicists for the past 100 years is the inability
to reconcile these two theories and formulate a unified theory that could essentially
explain everything in the universe also called ‘the theory of everything’. These
two theories are like viewing the earth with two plain maps where one map covers
one half of the earth whereas the other covers the other half and these two
maps although give a clear picture of its half but to get a complete picture of
the whole earth these maps can’t explain no matter how much you try to overlap
these two because earth is a sphere. We need an entirely new model called as
the globe to map the whole earth. The same way no matter how much ever you try
to reconcile these two theories there is no way to get the complete picture of
the universe without a completely new theory build on a completely new idea an
essentially new ‘theory of everything’. There have been some developments in
this direction such as the ‘string theory’.
The bottom line is black holes are still strange and our models could
barely scratch their surface. We are so far from completely understanding it
and I doubt it would be like that for a very long time.