A Sense of Perspective - Astronomically Speaking

Astronomical scales are something that is frankly beyond human comprehension.  Sure, we can calculate sizes and distances and map things against each other and we may feel that we have a metric of the scales involved - but this is simply academic/scientific knowledge - not internalized understanding.  Real comprehension in this case becomes almost transcendental.  This set of images, (source unfortunately unknown - I received them in an email...), which shows the relative scales of the familiar planets and a few familiar stars from our local neighborhood helps to make this point in a very graphic way:

First we have the terrestrial planets, of which Earth is the largest, and we also include Pluto as a representative member of the Kuiper Belt Objects.  There are many thousands (almost certainly more than 100,000) of these Pluto-type objects - some even larger than Pluto - in a broad torus that rings the Sun from the orbit of Neptune out to about 55 Astronomical Units (AU). (1AU is the average distance from the Sun to the Earth.)

Here we add the aptly named "Gas Giant" planets - Jupiter, Saturn, Uranus, and Neptune.

All of the planets are dwarfed by the Sun.

The Sun is a member of the main sequence "Dwarf" stars, and has a spectral classification of G2V.  This means that it is a yellow star, about 20% towards being an orange star, on the main sequence. Between 7-8% of all main sequence stars are G.  Sirius is the brightest star in the sky, as seen from Earth.  Pollux and Arcturus are familiar stars, easily visible from Earth.

But even these large stars are utterly dwarfed by "Red Giant" stars like Aldebaran, Betelgeuse and Antares.  As the Sun nears the end of its life, it will also grow into a red giant star like these.

So far we have just been talking about planets and stars.  Stars are only as "motes of dust" in the "dust storms" that are Galaxies!  (Only less so; the relative distances between grains of dust in a dust storm are orders of magnitude closer than the relative distances between stars in a galaxy.)

Credit: R. Williams (STScI), the Hubble Deep Field Team and NASA
Original image available here: http://hubblesite.org/newscenter/archive/1996/01/image/e
 

Here is where things get really "transcendental". In 1995 the Hubble Space Telescope was pointed at an "empty" region of the sky in the "Big Dipper", and captured this image.  If you imagine a pin held at arms length, the head of the pin would cover the area of the sky that is about the size of this image. Scientists have counted more than 3000 galaxies in this image.  (There are only a few foreground stars , which can be identified by their "spikes".)  It would take more than 500,000 images like this to cover the whole sky. If we did this, we might expect to see about 1,500,000,000 (one and one half billion) galaxies. The Milky Way is a fairly typical galaxy.  There are more than 100,000,000,000 (one hundred billion) stars in the Milky Way galaxy alone.

And now we have this new image, known as the Hubble Ultra Deep Field 2009 (HUDF09), which was taken by the Wide Field Camera 3 in August 2009. The faintest and reddest objects in the image are the oldest galaxies ever identified.  The photons that were captured from these ancient galaxies were emitted some 600 million to 900 million years after the Big Bang and have been traveling through space - at the speed of light - for about 13 billion years in order to reach us.

I think that it has to be very hard to maintain a conceit about mankind's central importance to the universe when faced with this kind of data.