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 How small are we compared with what we know? A lonely planet? I am not a astronomy enthusiast but there are some things that... Lonely planet – a view of our known Universe

Solar System

 How small are we compared with what we know? A lonely planet?

I am not a astronomy enthusiast but there are some things that each one of us should know about our planet, our solar system, about the Universe we live in.

The creation of the Universe started with the Big Bang approximately 13.7 billion years ago, give or take 130 million years and it is still expanding as we speak.

Only 4% of the Universe is made up from things that we can comprehend. This 4 % stands for everything that we can see, planets, stars, galaxies. The other 96% is made up from substances that specialists cannot yet understand and call them dark energy and dark matter.

For the biggest part of our history we considered ourselves a lonely planet, but are we really lonely? With all the information that we have, can we still consider ourselves as the only ones? It is really possible to think that once you know the facts?

Milky Way

If I would be to give you my complete address I should say : my street, Toulouse, France, Europe, Earth, our Solar System, Orion Arm, the Milky Way, The Local Group, the Virgo Supercluster, the Universe.

  • Orion Arm – the area where our Solar System is located in the Milky Way Galaxy, 25.000-28.000 light years from the galactic center
  • Milky Way – our galaxy with a diameter of approximately 100.000 light years and containing about 200 billion stars
  • Local Group – is a small cluster of gravitationally bound galaxies that contains the Milky Way, the Andromeda Galaxy, the small Triangulum Galaxy and a bunch of dwarf galaxies like: the Large Magellanic Cloud, the Sagittarius Dwarf Galaxy and Canis Major Dwarf Galaxy.
  • The Virgo Supercluster – is a group of clusters that incorporates our Local Group of galaxies and 100 other similar clusters. It is supposed to be between 100 and 200 million light years in diameter.

The Universe as we know it contains over 10 billion trillion stars in about 100 billion galaxies and it is estimated to be 156 billion light years in diameter.

Below you will see a picture with known planets and stars and their sizes in order to make an idea of how small are we. (source Wikipedia)

Stars and Planets


The largest star known to mankind until now is VY Canis Majoris, and according to Dr. Roberta M. Humphreys study, it has a diameter of 2.800.000.000 km or between 1800 and 2100 solar radii. (Download Acrobat Reader from here). From this value a circumference of 8.796.459.430 km can be calculated.  In order for you to imagine the size of Canis Majoris think that an average airplane travels with an average speed of 900 km/h. It would take this airplane more than 1100 years of non stop flight to be able to circle the planet one time.

How fast does light travel?

Light travels with exact 299.792.458 m/s in vacuum. That means that the light travels with a little more than 1 billion km/h. Just so you can make an idea, the sound waves travels at 1235 km/h and the fastest known military aircraft travels at 3.500 km/h.

So a light signal would travel the length of Earth’s equator in  like 134 ms, 1.3 seconds to reach the Moon, 8.32 min to reach the Sun, 4.37 years to reach Alpha Centauri, the nearest star system, 26.000 years to reach the centre of the Milky Way galaxy, 2.500.000 years to reach Andromeda Galaxy.

So after viewing all this data is impossible to say that we are a lonely planet, that we are the only ones in the Universe. We only need the necessary technology to be able to travel this distances. More advance and intelligent life forms must exist on thousands of planets out there, they just did not contacted us yet. Or did they…

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