October
20, 2019
We live on planet Earth. It is the best planet in the Solar
system that can sustain life as it is in the goldilocks zone of the Solar
system. The Solar system is basically a gravitationally bound planetary system
of Sun. The Solar system exists in the Oort cloud which is approximately
somewhere between 2000 to 5000 au (1 au=Distance from Sun to Earth). Someday,
just get on a high place at night and look at the sky; all the stars you see
have their own planetary systems containing planets, dwarf planets, moons, etc.
There are billions of stars just in our Milky Way galaxy, which is 100,000
light-years across. It is home to billions of stars like the Sun. This is a
huge number and I get goosebumps when I think about the fact that each of
these stars has its own planetary system. Isn’t it astonishing? Though this is
nothing compared to the observable universe. So, the Milky Way exists in the
local group of galaxies, which is a group of 54 different galaxies.
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| Hubble deep field picture of some galaxies in the universe by NASA |
The local group is 10 million light-years across. In addition, it is a part of the Virgo supercluster, which consists of 100 more groups of galaxies just like our local
group. The size of this supercluster is an astonishing 110 million light-years. Furthermore, the Virgo supercluster is also a small part of the
Laniakea supercluster, which consists of 100,000 more galaxies just like our
Milky Way and is 520 million light-years across. Lastly, the Laniakea supercluster is itself a part of the observable universe, which is home to
billions of more superclusters. Though the observable universe is a huge
place, it is very small in comparison to the whole universe. It is so small in
comparison to the whole universe that, it’s the ratio of a tube light to the
dwarf planet Pluto! We still don’t know what is beyond that extent, as the
light from those distant places has not had enough time to reach us. This
explains the fact that there are some places which humanity will never see even
if it was to last forever. If this is not enough to scare you, then the fact that
the universe is expanding further will. The reason for the expansion of the universe
is mainly due to inertia because in the very early universe, probably before
humanity, the matter was flying apart from each other for an unknown reason and
this phenomenon is still taking place. Though some say it was due to cosmic
inflation. Some say that there is a force called dark matter that is causing
the universe to expand at an ever-increasing rate. So, have you ever thought about what will happen when the universe stops expanding? If this happened, it would
neither expand nor contract; but, would become static. Eventually, the stars
would burn up all the gas that is used to light them up. The rate of the birth
of stars would decrease and thus, the universe would start to grow darker
consisting of a lot of black holes. Hence, at a point, the temperature in the
universe would become absolute 0 (-273 degrees Celsius). At this temperature,
all life will diminish and even atoms would stop moving.
Even though it is nearly impossible for the universe to stop
expanding, the main thing I wanted to convey through this blog was to tell you
about how huge the universe is and what do we know about it.
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