Dark secrets of the Universe
It is very common and obvious that we get so much interested
in stuffs like the origin of universe and human evolution and always try to
think about different possibilities and causes, also our scientists indulge in
the same. But, yet, we know very little about how the Universe was created.
It’s perhaps likely that we don’t know much– after all, we were never there
ourselves,right?. But it’s surprising to realize that when it comes to the ‘Universe
at the present time’, we don’t seem to have a much better knowledge of what is
out there!! In fact, astronomers and physicists have found that all we see in
the Universe – planets, stars, galaxies – accounts for only a small 4% of it!
This means, it is not so much the visible things that define the Universe, but
rather the void around them.
Cosmological and astrophysical observations indicate that
most of the Universe is made up of invisible substances that do not emit electromagnetic
radiation – i.e., we cannot detect them directly through telescopes or other similar
instruments. We detect them only through their gravitational effects, which
makes them very difficult to trace and analyze. These mysterious substances are
known as ‘dark matter’ and ‘dark energy’. Their role in the
evolution of the Universe is mystery, but within this darkness lays intriguing
possibilities of till now undiscovered physics (beyond the established Standard
Model).
Dark matter
Dark matter makes up about 23% of the Universe. The first clue
of its existence came in 1933, when astronomical observations and calculations
of gravitational effects revealed that there must be more ‘stuff (???)' present
in the Universe than telescopes couldn’t see.
Researchers now believe that the gravitational effect of
dark matter makes galaxies spin faster than expected, and that its
gravitational field deviates the light of objects behind it. Measurements of
these effects show that dark matter exists, and they can be used to estimate
the density of dark matter even though we cannot directly observe it.
But what is dark
matter? One idea is that it could contain ‘supersymmetric particles’ i.e.
hypothesized particles that are the partners to those already established in
the Standard Model.
Dark energy makes
up approximately 73% of the Universe and appears to be associated with the
vacuum in space. It is homogenously distributed throughout the Universe, not
only in space but also in time (what does this mean???,think about it!!!).
Meaning -its effect is not weakened as the Universe expands.The even
distribution means that dark energy does not have any local gravitational
effects, but rather a global effect on the Universe as a whole. This leads to a
repulsive force, which tends to accelerate the expansion of the Universe. The
rate of expansion and its acceleration can be measured by observations based on
the Hubble law. These measurements, together with other scientific data, have
confirmed the existence of dark energy and provide an estimate of just how much
of this mysterious substance exists.
