Researchers at the Center for Astrophysics and Space Sciences at the University of California, San Diego have estimated that the awe-inspiring, spiral-shaped Milky Way Galaxy, in which our own earth resides, contains more than 400 billion stars. Other estimates place the number around 300 billion, but either way we are talking about an incredibly large number.
Furthermore, the Milky Way Galaxy contains nearly the same number of planets, scientists say, with microlensing observations suggesting that those in the habitable zone may number as high as 10 billion. The galaxy is composed of a galactic center; a rotating, flattened disk area containing a very large number of stars (along with large amounts of galactic dust and various molecular and atomic gases); and a spherical halo of presumably dark matter, whose presence is inferred by its gravitational effects on the visible portions of the galaxy. (a)
"The halo consists of the oldest stars known, including about 146 globular clusters, believed to have been formed during the early formation of the galaxy with ages of 10-15 billion years from their H-R Diagrams," states one online tutorial written by Professor H.E. "Gene" Smith. (b)
While an enormous amount of dark matter is theorized as being integral to the milky way's existence—and indeed the composition of the entire universe, alternative theories do exist. Astronomers at the University of Bonn, whose findings were published by the Royal Astronomical Society, are among those who have called the existence of dark matter into question.
"In their effort to understand exactly what surrounds our Galaxy, the scientists used a range of sources from twentieth century photographic plates to images from the robotic telescope of the Sloan Deep Sky Survey.
Using all these data they assembled a picture that includes bright ‘classical’ satellite galaxies, more recently detected fainter satellites and the younger globular clusters," the RAS states in a May 2012 update. "The astronomers found that all the different objects are distributed in a plane at right angles to the galactic disk. The newly-discovered structure is huge, extending from as close as 33,000 light years to as far away as one million light years from the centre of the Galaxy." (c)
Lead author Marcel Pawlowski and team member Pavel Kroupa have suggested that what we are really seeing is the remnants of a collision between two galaxies billions of years ago.
Evidence calling into question the existence of dark matter also was presented on June 18 from data collected in an unusual underground experiment at Italy's Gran Sasso National Laboratory, designed to detect the "weakly interacting massive particles” (WIMPs), which many scientists suspect dark matter to be composed of. Yet after 225 days of data collection, using an instrument far more sensitive than had ever been used before, the elusive dark matter particles remained as elusive as ever. (d.)
To the contrary, this past month astronomers at the University of Michigan claimed to have observed what they call a filament of dark matter between two relatively adjacent galaxy clusters.
As stated by Zeeya Merali in the July 4, 2012 online issue of Nature: "The presence of dark matter is usually inferred by the way its strong gravity bends light traveling from distant galaxies that lie behind it — distorting their apparent shapes as seen by telescopes on earth. But it is difficult to observe this 'gravitational lensing' by dark matter in filaments because they contain relatively little mass. (Jörg) Dietrich and his colleagues got around this problem by studying a particularly massive filament, 18 megaparsecs long, that bridges the galaxy clusters Abell 222 and Abell 223." (e)
The exact nature and possible existence of dark matter, as with dark energy, is very intriguing and likely to be debated for some time. But let me turn the corner and draw your attention to something which I believe is far more fundamental.
What needs to be debated and vigorously challenged is the human propensity to resign itself to a philosophically constricted and scripted view of the human experience; that says everything—everything—must have absolute meaning in order to have value; and which reasons that death is inevitable and merely transitory.
How can humanity transcend the physical limitations of its existence in a real and practical sense—as opposed to the fantasy worlds built by superstition and spiritualism?
This is the question we should be asking.
Will we ever reach the stars?
Not if we fail to think outside the framework of tradition.
Not if we don’t stop ourselves from dying in the process.
The three-star Alpha Centauri system, the closest stars to our own, lies an estimated 4.37 light years away. The red dwarf known as Barnard's Star lies 5.96 light years away; Wolf 359 lies about 7.78 light years away; Lalande 21185, also a red dwarf, lies about 8.29 light years away; Sirius lies about 8.58 light years away; Luyten 726-B about 8.73 light years; Ross 248 (HH Andromedae) about 10.32 light years; and Epsilon Eridani about 10.52 light years.
Astronomers with the European Southern Observatory (ESO) published research this past year which said that there could be as many as 100 planets within 30 light years of earth. Billions more are presumed to exist throughout the broader Milky Way Galaxy. (f)
But herein lies the problem.
As defined, a light year is the distance that light in a vacuum travels in one year. That distance is calculated to be a little under 10 trillion kilometers—6 trillion miles in other words. This calculates to an incredible 186,282,297 miles per second. If we wanted to reach even the closest star system beyond our own, the Alpha Centauri system, and managed to reach speeds approaching 150,000 miles per hour, it would this infinitely flight-worthy ship roughly 18,000 years to arrive at its destination. Think about that for a minute.
We could surely send ourselves on a one-way voyage to some new world millions of light years away, counting on the cycle of reproduction to ensure the continuation of the species, as in Paul W.S. Anderson's 2009 Sci-Fi thriller Pandora, but what would be the point when the people who arrive will be 180 generations removed from those who first began the journey? The odds of maintaining some semblance of sociological, psychological and physical continuity would seem to be slim if not impossible.
I would not go so far as to say that such a quest would be irrelevant, but I will say this: The need to overcome disease and death, to overcome the genetic and physical imperfections of the human organism in the hear and now, in my opinion dwarfs any perceived need for space travel. When we finally get to the point where serious life extension beyond the pathetically-short 100 years or so we can hope for now becomes a reality, when the people who set off on the journey into space are the same people who will land on that new world in some distant part of the galaxy, then we'll have reason to celebrate.
References
(a) Nature, Vol. 481, pg 167-169.
(b) Astronomical Tutorial
(c) Do the Milky Way’s Companions Spell Trouble for Dark Matter?
(d) New Cern Tests Attack the Existence of Dark Matter
(e) Dark Matter’s Tendrils Revealed
(f) Astronomers Find First Habitable Earth-Like Planet