Due to the expansion of the universe, sometime around 2 trillion years from now, it won’t be possible to see anything outside our Local Supercluster.
There are all sorts of thoughts bouncing around my poor old noggin at the moment, accompanied by the lyrics to the classic R.E.M. song, “It’s the end of the world as we know it (and I feel fine),” except that — in this case — I actually feel sad (said Max, sadly).
Did you ever read the 1941 science fiction novelette Nightfallby Isaac Asimov? This tale was sparked by a quotation from Ralph Waldo Emerson:
If the stars should appear one night in a thousand years, how would men believe and adore, and preserve for many generations the remembrance of the city of God!
Asimov was discussing this quotation with John W. Campbell, who was the editor of Astounding Science Fiction magazine at the time. Campbell disagreed with Emerson, saying “I think men would go mad.” The result was Nightfall, which is set on a planet that is constantly illuminated by at least one of the six suns in its multiple star system. As a result, the “people” on the planet have never seen the night sky.
The narrative revolves around a group of scientists who have discovered a series of past civilizations, all destroyed by fire, with each collapse occurring about 2,000 years apart. It turns out that, once every 2,000 years, an unknown moon causes an eclipse of one of the suns when that sun is the only one in the sky. Even worse, the planet is located at the center of a supercluster. When the eclipse occurs and everyone sees 30,000 stars blazing for the first time, they panic and set fire to anything that will burn in order to keep the night away.
Another story that is relevant to this column is A Fire Upon the Deep by Vernor Vinge. This commences with an expedition launched by a young human civilization located close to the edge of the Milky Way. They are investigating a five-billion-year old data archive on a desolate planet at the very edge of the galaxy when they inadvertently awaken a malevolent superintelligence buried deep within the archive. All of this happens in the 7-page prologue, after which things start to get exciting.
When Einstein published his general theory of relativity in 1915, it was thought that the universe consisted only of our own Milky Way galaxy. It wasn’t until 1924 that American astronomer Edwin Powell Hubble proved earlier conjectures that the Milky Way is just one of many galaxies in the universe.
It was also discovered that the galaxies are moving away from each other due to the expansion of the universe caused by the Big Bang, which occurred around 13.8 billion years ago this coming Wednesday.
Initially, it was assumed that gravitational attraction would gradually slow, and eventually reverse, the expansion, eventually cumulating with the end of the universe in the form of the Big Crunch. However, in 1998, it was discovered that the expansion of the universe is accelerating (don’t get me started talking about “dark energy” and “dark matter”).
So, what does the future hold? Well, in their 1999 book The Five Ages of the Universe, the astrophysicists Fred Adams and Gregory Laughlin divided the past and future history of the universe into five eras. We are currently in the second, the Stelliferous Era, which will continue for close to 100 trillion years.
It’s important to note that, when we say that galaxies are moving away from each other, this doesn’t apply to galaxies in (relatively) close proximity because these are gravitationally bound to each other; that is, their gravitation attraction overcomes the effects of universal expansion.
For example, the closest galaxy to the Milky Way is the Andromeda Galaxy, which was about 2.5 million light years away from us when I broke my fast this morning. The Milky Way and the Andromeda Galaxy are moving towards each other at around 110 kilometres per second (68 mi/s), and will merge to form the Milkomeda galaxy (also known as the Milkdromeda galaxy) in around six billion years (give or take a billion years or two).
Similarly, the approximately 60 galaxies in our Local Group, which includes the Milky Way and the Andromeda Galaxy, are gravitationally bound and will merge into one large galaxy sometime between 100 billion and 1 trillion years from now.
Just to increase the fun and frivolity, we have the Local Supercluster, which contains at least 100 galaxy groups and clusters, including the Local Cluster.
The focus of my current cogitations and melancholy musings is that, due to the accelerating expansion of the universe, sometime around 150 billion years from now, all of the galaxies outside our Local Supercluster will pass beyond the cosmological horizon, at which point intergalactic transportation and communication beyond the Local Supercluster will become causally impossible.
Even worse, sometime around 2 trillion years from now, all galaxies outside the Local Supercluster will be red-shifted to such an extent that — as far as we’re concerned — even the gamma rays they emit will have wavelengths longer than the size of the observable universe of the time. Therefore, these galaxies will no longer be detectable in any way.
So, if any intelligent civilizations arise in our Local Supercluster more than 2 trillion years from now, they will assume that the Local Supercluster is the entire universe. Furthermore, on the outside chance they think to look for it, there would be no indication as to the origins of the universe. According to Space.com website, Evidence of Big Bang May Disappear in 1 Trillion Years.
Even if these hypothetical civilizations found some mention in an ancient data archive on an abandoned planet that detailed our understanding of the universe, they would probably shrug their equivalent of shoulders and say, “Nah — it’s not likely — they were probably confused and mistaken — how could ancient aliens know more about the universe than we do — and who was this ‘Max the Magnificent’ character whose writings flood the archive anyway?”
I know 2 trillion years is a long way away and — unless I get my time machine working again — the chances are I won’t be around to see what happens, but I still feel bad about those poor creatures never having a fighting chance to understand the origins of the universe. What say you? What are your thoughts on all of this?