The Great Beyond
In my opinion, the most amazing astronomical picture taken to date is now The Hubble Ultra Deep Field (HUDF). This is a sandwiched composite photograph assembled from 800 separate images taken with the Advanced Camera for Surveys' Wide Field Camera (ACS/WFC) of the Hubble Space Telescope and is equivalent to 11.3 days of exposure (images captured from September 24, 2003 to January 16, 2004). It represents a narrow "keyhole" view stretching to the visible horizon of the universe, and covers a speck of the sky only about the width of a standard US postage stamp located about 23 meters away. Though the field is a very small sample of the heavens, it is considered representative of the typical distribution of galaxies in space because the universe, statistically, looks largely the same in all directions. Gazing into this small field, Hubble uncovered a bewildering assortment of about 10,000 galaxies at various stages of evolution.
Now, let's do a little math. The area of a standard US postage stamp is about 4 cm2. The surface area of a sphere with radius 23 m is about 66 x 106 cm2. Dividing this by the area of the stamp and then multiplying by 10,000 leaves us with an estimate of the total number of observable galaxies in our Universe. This number is approximately 165 billion. Now, since we are looking far back in time for these distant galaxies in the HUDF picture, it is hard to say what the number present at one given time is. But if you think about this a bit, "one given time" is really a meaningless concept. Regardless, the number is HUGE. Don't forget that each galaxy is composed of billions of stars. If our galaxy (The Milky Way) is typical, then we can expect that the average number of stars per galaxy is about 200 billion. This translates to about 33 x 1021 stars in the Universe. The size of this immense number is hard to fathom. However, if a period on this page represents an average star, then all these stars packed together would fill a box measuring about 8 miles on each side! So, do you still think that we are the only intelligent creatures that exist, have ever existed, or will ever exist in this immense realm?*
*Please don't think that I am making an argument for the visitation of extraterrestrials to our planet. There is really no solid evidence for such. Yes, there are always the "Who built the pyramids?" types of questions. But I feel that those types of questions have more reasonable solutions than flying saucers hovering over us and buzzing our planet with tractor beams. You may now argue..."Given a virtual certainty that other intelligent life exists out there, why haven't we heard from them?". Well, there are many roadblocks to this occurrence. Distances in the universe are absolutely huge (I repeat....HUGE) and information can only travel as fast as the speed of light. We also have no real idea of what to "look" for in the way of a signal from beyond. SETI (search for extraterrestrial intelligence) looks for patterns in radio signals from outer space that are nonrandom. That is about as far as it goes. If you would like to know more about the current state of this goal, I suggest visiting Sky and Telescope and then doing a search for SETI in their search window. Believe it or not, you too can help in this search. It should also be noted that since we have only been broadcasting for about 60 or so years (and the first broadcasts were weak compared to those today), that would mean that anyone farther away than 60 light years and looking at us, would detect a blank signal (read: no intelligent life there....Hmmm, that may be true regardless!). To conclude, my feeling is that in the scope of the Universe as a whole, we are not alone. But, given the enormous size of our measurable space, we are, in effect, alone indeed. So, let's continue to look afar, but not forget our home and the care that it always needs. It won't be around forever, but this home as we know it will have a much shorter lifespan if we choose to disregard it.