It used to be thought that we were about halfway through our planet’s history, and that conditions would continue in the way they have in the last few hundred million years until the Sun becomes a red giant in something like five thousand million years’ time. Sadly, this is not now considered likely, but that’s not really because of us or any damage we might be doing to the planet’s long term prospects. It turns out that our Sun has something more hostile in store for us in less than an æon. And at this point I should probably explain my words.
Firstly, I still use the long scale with large numbers, so for me a billion is 1012 and so on – 1 followed by twelve 0’s. The short scale, where a billion is 109, 1 000 000 000, is American and when I say “American” I mean both continents. It’s fairly wasteful to use up the words for numbers on lower values, so I don’t do it. That said, ironically from an English-using perspective, the short scale does line up better with metric multiple prefixes such as giga- for “billion” and tera- for “trillion” and so on. There’s also already a perfectly good word, “millard”, referring to a hundred thousand anyway.
Secondly, the word æon, from the Greek word ‘αιων meaning “age” or “generation”, and sometimes translated in the Bible as “world” in a fairly pejorative way, is a unit of time lasting a thousand million, or millard, years. From the same root stems the word “eon”, which is a division of time above “era”, so I’ll talk about that too. Earth’s past history is divided on the longest temporal scale into eons, namely the Hadean, Archean, Proterozoic and Phanerozoic, this last being our current eon. From the Archean onwards, these are divided into eras (the well-known Palæozoic, Mesozoic and Cenozoic in the past 540 million years or so), periods (for example the Triassic, Jurassic and Cretaceous), epochs (in our case the Pleistocene, Holocene and probably the Anthropocene), ages, for example the Meghalayan which lasted from some time in the Bronze Age and might be considered to have finished in the 1950s, and finally chrons, which in the case of the current Sub-Atlantic started around the time Rome was starting to expand. It gets a bit confusing because of the archæological Three Age System of Stone, Bronze and Iron, and incidentally we are still in the Iron Age, which collides with the chrons.
With a couple of exceptions, Earth’s future is as yet unmapped as far as actual names for intervals of time are concerned, but it certainly isn’t unmapped according to scientific understanding, which of course could change easily. In fact it did just that in the past few years with the realisation that we haven’t got as long as we thought. I’ve already gone into a fictionalised history of the next two hundred million years which mainly amounts to Dougal Dixon’s work on ‘After Man’, ‘Man After Man’ and ‘The Future Is Wild’. This is somewhat feasible and somewhat based on science, though forty year old science, and has some degree of validity, but there is a firmer understanding of the probable near future, and also well beyond that until the Sun dies. Thus I’ll start with the next few million years.
It’s been proposed that we’re currently in the Anthropocene Epoch, but it isn’t clear when it started. The previous epoch, the Holocene, covered the time since the end of the last Ice Age, but in recent years it’s been reconsidered and now there’s a popular movement to divide the Holocene off from the past few years because of the major effect our own species is having on Gaia, hence Anthropocene – ‘ανθροπος + καινος = > human + freshness. All the epochs in the Cenozoic end in “-cene” because they’re relatively recent. The geological dating system uses “BP” to name particular fairly recent times, usually within the history of our genus Homo, which stands for “Before Present”, the “present” being defined as the year 1950. Consequently one suggestion is to date the Anthropocene from 1950. Another rather similar proposal is that it begin from the earliest nuclear weapons tests, since these have left a long-lasting change in the geological record by irradiating the world and changing its radionuclide signature. A third suggestion is that it begin with the Industrial Revolution, and finally Heather Davis has proposed that it start in 1492, since this is when Europeans began to conquer the rest of the world. Rupert Sheldrake, who articulated the Gaia Hypothesis, recently proposed that the Neocene will follow the Anthropocene in the near future, which basically coincides with the Singularity and marks the point where machines will sort the environmental problems we’ve created. This would make the Anthropocene ridiculously short, possibly less than a century, but Sheldrake embraces that, linking it to the acceleration of change, which may have started nearly an æon ago with the appearance of multicellular life. The future is of course unknown and our existence may have vast consequences of which we’re currently unaware and can’t anticipate, but there’s also what might be called the “geological future”, that is, the future as it will proceed assuming that human activity lacks major long-term consequences for the planet, which is probably less hubric and more Copernican, as it were.
Naming things doesn’t necessarily give you any control over them though.
The most obvious issue in the relatively near future is anthropogenic climate change. It isn’t clear whether what we do to the climate is far-reaching enough to end the recent spate of ice ages, of which there have been five from the Pleistocene onwards so far. It might even trigger one, because if Antarctic icebergs spread far enough they may reflect more heat into space and cool the planet. There are various ideas about the next ice age. The most popular seems to be that it will happen anyway, in about fifty millennia, which is when it’s “scheduled”. More recently this has been questioned, and some climatologists believe there will still be another ice age but that it will be in a hundred millennia, because by that point climate will have returned to the point where it would’ve been without our technology as it has recently been. Of course it may also be that we or our machine successors will just “re-wild” most or all of the planet and things will get back to “normal”. This degree of uncertainty regarding even the relatively near geological future might be seen as indicating that this is just idle speculation, but in fact it may not be because certain things are well-known and established scientific facts it seems unlikely we’ll be able to avoid, such as entropy, and those can be predicted fairly confidently.
A lot of this is covered in the popular video ‘Timelapse Of The Future’:
I’ve covered this before here, and there are similarities between this post and that one and its successor, but I hope I’m saying something fresh here too.
Fifty thousand years from now, the day will be one second longer. This is because the lunar tidal action on Earth gradually slows our rotation. I’ve previously been curious about how long it would take before the year has exactly three hundred and sixty-five days, and if this change is linear, leap years will become unnecessary by the time each day is fifty-nine seconds longer, almost three million years from now, and before that date they could be rarer, say every five years by six hundred millennia from today. To be honest, I find the idea that the Gregorian calendar would still be in use by then absurd, but there are similar assumptions made about the likes of long-term contracts and economic planning, so maybe it will, and Y2K is an example of a problem caused by assuming such things would not be in place for longer than a few years.
A quarter of a million years hence, Lō’ihi will break the surface of the Pacific Ocean, although it may of course be either deeper or shallower by then depending on which way sea levels go. This is the next Hawaiian island, to the southeast of Hawai’i itself. This will continue as the Pacific plate and the hotspot shift over many millions of years and the islands to the northwest erode away. By six hundred millennia from now, the chances are that an asteroid one kilometre in diameter will have hit us, although this could happen at any time. The energy released by this would be equivalent to around sixty times the detonation of every nuclear weapon in the world. There’s a modelling tool for asteroid impacts here.
Around a million and a quarter years from now, a red dwarf star called Gliese 710 will be very close to the Solar System, less than a quarter of a light year away. By two million years hence, judging by previous events when this has happened, the ocean will once again be alkaline enough for coral to recover. This acidification occurs because of the increase in atmospheric CO2. Ten million CE will be around the time the Afrikan Rift Valley will be flooded and the new continent, which Dougal Dixon named Lemuria, will start to move across the Indian Ocean. Also by this time, even without a mass extinction most species around today will have died out and, I hope, been replaced. Fifty million years from now the map of the world will look roughly like this:
(I actually think this is exaggerated in the sense that it assumes the rate of continental drift to be faster than it in fact is).
Around 200 million years from now, there will be a new supercontinent, whose exact shape is hard to predict because nobody knows much about which way Antarctica will move. This restores the planet to the situation as it was before the dinosaurs evolved, and makes for a large amount of desert with extreme temperatures near the centre of the continent, very hot during the day and very cold at night. It will also increase the amount of oxygen in the atmosphere, and means a single world ocean and a single landmass covering 29% of Earth’s surface. While this continent is in place, the Hadley cells either side of the Equator will move to 40° either side of it. This will increase the already high percentage of desert land by a further 25%. This supercontinent will have broken up by about 450 million years from now, leading to the kind of climate found here during the Age of Dinosaurs, and also at around this time the likelihood of a mass extinction from a gamma ray burst, which will cause it to rain concentrated nitric acid, means it’s likely to have happened by about this time.
There may just be time for another supercontinent to form about 600 million years from now, by which time there will be no more total solar eclipses because of our satellite’s widening orbit, but there will still be annular eclipses where some of the Sun’s surface remains visible.
Then, unfortunately, a major catastrophe will ensue. Up until this point, a process referred to as the carbonate-silicate cycle has kept considerable amounts of carbon dioxide in the atmosphere. Rain dissolves this gas and acidifies, landing on rocks and gradually dissolving them. Calcium and bicarbonate ions are washed into the ocean, where it’s incorporated into the hard parts of organisms such as plankton, molluscs and coral. This sinks to the ocean bed, where it’s buried and ends up in the magma under the crust. Volcanic eruptions then return this to the atmosphere as carbon dioxide. But the Sun is gradually getting brighter, and by this time the light will be strong enough to start weathering the rocks faster than their carbon can be released back into the air, and will also start to dry the land, reducing rainfall and therefore carbon reaching the sea. The rocks will also harden, slowing continental drift and since that’s responsible for throwing up new volcanoes along the edges of the plates, these will erupt less often. At a certain point, around 600 million years from now, one form of photosynthesis known as C3 will cease to operate due to insufficient carbon dioxide in the atmosphere. This will lead to a gradual decline and eventual extinction, first of green herbs such as annuals, then deciduous trees, then broad-leaved evergreens and finally conifers. I would expect that during this time, evolution would lead to other plants occupying their vacant niches. That said, there’s still C4 photosynthesis, which can function at a lower level of carbon dioxide, and there are many plants which use this type, particularly those in the spurge family, and they already look quite alien and futuristic:
Date
17 May 2006
Source
Own work
Author
Sphl
Water vapour is a much more powerful greenhouse gas than carbon dioxide and consequently this evaporation of water from the oceans and elsewhere will start to raise surface temperatures. Because of less photosynthesis, oxygen will also fall and therefore the ozone layer will break down and there will be more oxidation at the surface due to more ultraviolet light penetrating to ground level, removing even more oxygen from the atmosphere. By 850 million years or so in the future, C4 photosynthesis will become impossible and the cycle run by the sun through plants will cease to function. This means that only animals who don’t breathe oxygen or rely on plants for food, directly or indirectly, could survive. This would, for example, include worms living in geothermal vents at the bottom of the ocean who feed on bacteria. However, the ocean will also be disappearing and once the average surface temperature exceeds 47°C 1.1 æons from today, the amount of water vapour in the atmosphere will start to run a feedback loop through the greenhouse effect, causing runaway evaporation from the oceans and a slide into a situation where the only life which can survive will be in places like lakes and caves at the tops of mountains or near the poles, and finally not even that. 1.6 æons from now only bacterial and archeal life will remain, and 2.8 æons hence even the poles will be at 150°C.
I find this all rather claustrophobic and suffocating, which is a bit of a weird reaction. I look around at the trees in the park, the people, badgers and spiders in this household, note that I can breathe the air and that there is evidence of human activity all around in the form of houses, roads, vehicles, furniture, whatever, and it really saddens me that it will come to an end so soon, but I also find it weird because we’ve got 800 million years to go. However, they used to think that Earth would stay in about the same state for about as long as it had already existed, so theory has robbed us of three or four æons of life. There’s only enough time for another two supercontinents, by contrast with maybe ten which have happened before on this world. But the future is in fact unknown and may not be like the past, or continue trends which began then. We have intelligent tool-using life now, and those tools may find a way to lengthen our stay, or alternatively hasten our demise. Also, if some of us were to leave this planet permanently and entirely to settle elsewhere, that gives us more hope, if hope is the word. But a Doomsday Argument-like scenario makes that unlikely. Then again, maybe it isn’t up to us. Maybe another species of animal will start to invent more advanced tools and technology before the carbonate-silicate cycle breaks down. Maybe there will even be such beings around as it starts to happen. Who knows? The future is unknown.
A Box Of Chocolates 