The Limits to Humanity

Much to the chagrin of my grandparents who largely raised me, my view of the universe was shaped by Carl Sagan and his various science lectures on television and books. Not that they opposed me watching his version of “Cosmos” on PBS back in the 1980's, in fact my grandfather was probably just as enthralled as me. But lets just say I came away with ideas that didn't fit well with their views. And to be truthful, some of Dr. Sagan's concepts didn't fit well with my understanding of the universe either.

At that time in my youth, I didn't understand the nature of the cosmic speed limit of light and frankly chaffed at the idea that there was no way around it. Having watched the Starship Enterprise and numerous other fictional vessels exceed lightspeed allowing them to have weekly adventures on all manner of alien worlds was something I desperately wanted to be possible. But Carl Sagan did offered up a semi-satisfying alternative in one episode of Cosmos.

Dr. Sagan said that it was theoretically possible for a sublight starship to circumnavigate the observable universe within the lifetime of a human being. Of course this hypothetical starship would have to squeeze extremely close to lightspeed in the order of something way more than 99.99999999 percent of light. Yes, an extremely difficult task given the energy requirements but as imaginary journeys of the mind go, not a show stopper we need to worry about right now.

What makes such an ultimate journey possible for these hypothetical humans would be time dilation, which would more of less stop time for those aboard the starship relative to the rest of the universe. The price these travelers had to pay though was that many billions of years would have passed upon their return home. While I never saw circumnavigating the observable universe as an attractive adventure just to return to a home that didn't exist anymore, it did imply there wasn't anyplace we couldn't reach for exploration and colonization in the future. The same goes for building fascinating stories here in the present.

One of my all-time favorite science fiction novels is entitled “The Genesis Quest” by the late Donald Moffitt. In that book an alien species in the Whirlpool Galaxy, twenty-three million lightyears away, intercept intergalactic radio messages sent by humans in the good-old Milky Way Galaxy. Included in these messages were genetic instructions on how to recreate living humans. A century or two later the resulting colony of Homo sapiens spends most of it time reviewing the information sent from the Milky Way, like the key to immortality, and growing restless.

As with humans, they get stupid and revolt against their good-hearted alien benefactors who promptly give them a massive sublight starship so a bunch of them can make the twenty-three million lightyear journey back home. Because the humans are now immortal, the five-hundred year voyage to the Milky Way is easy-peasy. The trouble arrives in the sequel, “Second Genesis” when they get back to the home galaxy and find out the neighborhood has gone downhill.

Even without warp drive or any other faster-than-light technology, science fiction suggested that humanity had a bright future filled with adventures zipping between galaxies. That was until Dark Energy went and screwed up the whole thing.

Since the early twentieth century we've understood that the universe was expanding. It all started at the Big Bang with space itself inflating outward pushing all matter farther apart. The general idea held by the cosmology boys and girls was that at some point gravity would slow the expansion and eventual pull everything back together into what they called the Big Crunch. Things got weirder as more accurate measurements of the universe showed that the expansion was actually accelerating.

Cosmologists, a bunch not prone to idle speculation, eventually came to the conclusion that there was a mysterious anti-gravity-like force that causes this increased rate of expansion. They call this anti-gravity force Dark Energy because they haven't a clue about how it works.

Where Dark Energy really throws a cosmic monkey wrench into intergalactic travel fantasies is that it is pushing everything outside the Local Group of galaxies, which includes the Milky Way, away from each other essentially faster than the speed of light. Yes, the damn cosmic speed limit is still in effect but that only prevents anything with mass going FTL. Space itself doesn't have any mass so Dark Energy can expand the universe as fast as it wants.

What this means is that when and if humanity ever begins building sublight starships that go as fast as I mentioned above such vessels would never reach the Whirlpool Galaxy. The same would go for the fictional humans of “The Genesis Quest” wanting to return home. With the expansion of space itself such travelers would spend eternity speeding through a dark, growing void.

Now all is not lost as far as intergalactic travel is concerned. The Local Group of galaxies we're inside consists of the Andromeda Galaxy and a whole bunch of dwarf galaxies all occupying an area around three megaparsecs, roughly 9.8 million lightyears. The Milky Way by itself contains between 100 to 400 billion stars with each star system hosting an assortment of planets. The Andromeda Galaxy is estimated to have at least 1 trillion stars with each of them orbited by its own worlds. That's an awful lot of potential real estate for any species capable of pulling their heads out of their asses and acting like they have some intelligence.

In fact since everyone in the Local Group is bound together by gravity, we'll all merge into one huge elliptical galaxy in several billion years. Sometime after that Dark Energy will push the rest of the universe so far away it will beyond our ability to detect given our current technology. Any existing intelligent species at that time will most likely believe the universe is static and unchanging. That is until all the available interstellar hydrogen is used up, stars begin to die, and the universe suffers what is called Heat Death.

Yes, that pesky Dark Energy means Dr. Sagan was wrong about a sublight starship being able to circumnavigate the observable universe. Dark Energy wasn't discovered until the 1990's, several years after his death so you'll have to cut the man considerable slack.

I've got to admit, I find the idea that the vast majority of the universe exists outside our ability to ever reach disturbing on a philosophical level. That the greater majority of it will eventually slip into the darkness never to be seen or considered again. Yeah, that will not happen for billions of years but I grew up influenced by Captains Kirk, Picard, Sisko, Janeway, and Archer to believe that at least the galaxy was our playground.

I like to fool myself sometimes to think I can set aside normal human assumptions about the nature of the universe. That assumption being that the cosmos exists to satisfy the needs and desires of our species. Speaking strictly about the universe, it doesn't give a damn about us hairless primates. It might be beneficial to the rest of humanity to realize that fact as well.