A few days ago the Cassini space probe orbiting Saturn took an
astonishing photograph showing the Earth as a tiny blue dot
underneath the rings of Saturn. The photo is shown below.
Photo: NASA/JPL-Caltech/Space Science Institute
Some people have remarked that the image really helps us to keep our
little planet in perspective, as it shows Saturn as very large, and
our planet as very small. But to get a much better perspective, we
must travel much further out in space.
Let's imagine how it would look if you were on a spaceship traveling
far, far away from Earth. Let's imagine you are some type of immortal
being on a spaceship capable of traveling at 80% of the speed of light.
After twenty or thirty years of travel, you would look out the window
of your spacecraft and see something like the image below, assuming
you were not looking at the plane of our galaxy.
You would know that
one of those stars was Earth's sun, but you would not be able to
detect which star was our sun without checking a computer or an
astronomical reference. Our sun would look just like any star in the
sky.
The view out your window would look the same way for many hundreds of
years. But after thousands of years of travel away from the plane of the Milky
Way galaxy, you would eventually be able to see some of the outline of
one of the galactic arms of our galaxy.
Photo: NASA
After finally traveling for tens of thousands of years, you would be
able to see our spiral galaxy the Milky Way in all its glory. You
might for a moment think of trying to find our sun amidst all of the
stars in the Milky Way, but would quickly realize that there was no
chance of doing such a thing. Because the galaxy you would see would
consist of hundreds of billions of stars, the Sun would be far too
small to pick out, as hard as picking out a grain of sand from a
giant sand box.
Photo: NASA
As your lonely voyage reached a length of millions of years, you
would be able to see about 54 other galaxies, each a collection of
billions or hundreds of millions of stars. These would be the galaxies in the Local Group of
galaxies. As you looked out the window, you would see two other
spiral galaxies, in addition to the Milky Way: the Andromeda Galaxy
and the Triangulum Galaxy. The Andromeda Galaxy would look larger
than our Milky Way.
Photo: NASA
Eventually millions of years later the entire Local Group of 54
galaxies would take up only a small part of what you would see in
your window. You would also be able to see many other groups of
galaxies.
As your spaceship kept traveling for many millions of years, your
ship would pass through countless other clusters of galaxies. You
might try to keep track of where your home galaxy the Milky Way was
in the sky, but eventually it would become a speck too small to see.
As the length of time of your journey stretched on to hundreds of
millions of years, you would wonder: when will I stop seeing galaxy
after galaxy? You would remember your own galaxy as the first of
millions of galaxies you saw from your window.
Having taken this imaginary trip into space, you may have a clearer
idea of how small and microscopic our planet is in the grand cosmic
scheme. Our planet Earth is like a mere drop of water in a vast
ocean. You and I and the rest of the human race are like bacteria
swimming around in that drop of water.
Therefore in all of your thinking, be very, very humble.
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