I recently saw a show on Animal Planet that showed animated, scientifically based, speculations as to the species that would would inhabit the Earth in 5 million years and beyond.
Man was not one of these species. If fact, the show stated that the Earth would be uninhabitable by humans inno more than 5 million years and, hopefully, we would have figured out a way to relocate to another planet before then.
How, and why, will the Earth become uninhabitable? What is the most likely timeline for this to occur?
It based on the assumption that few species survive for more than a few million years. This is especially true of mammals. Some species - e.g. horshoe crabs (Linulus), brachiopods - seem to have survived for over a hundred million years unchanged, bu as a rule the fossil record suggests very few species survive over ten million years.
By assuming that humans are typical and will be extinct in a few milion years, the program makers are free to make their wild guesses. And that’s all they are.
Why would humans become extinct? No idea. If we knew why we could do somehting about it. But there are lots of possibilities - asteroid impact, geological activity (such as the events that created the huge larva flows known as the Deccan Traps), whatever.
However, any such scenario has to assume humans don’t use their brains to work out a survival plan. We could lose five billion now and still survive as a species, just not in society as we know it.
The general idea is that the sun is progressively getting hotter (basically it begins to burn elements other that Hydrogen leading to high temps). The heating leads to additional water vapour in the atmosphere. Now water vapour is a “greenhouse” type gas which means that it will diminish the amount of heat radiated back into space at night. The combination leads to a “run away greenhouse effect” with temperature getting hotter and hotter. Eventually there’s enough water vapour in the atmosphere that significant amounts of hydrogen are lost (the H20 is split by UV). Now we have lots of oxygen which leads to more fires and basically it’s off to hell in a hand basket.
It’s a way off and if we can get off this rock we can work on mitigating this scenario.
I don’t know of a predictable reason*, except to add to the drama of a TV show that 5 million years from now the Human Race would not be able to live on earth. I would love to be corrected, but I would be surprised if there is one.
As far as a real “timer” running on the earth, the only thing I am aware of is the lifetime of the sun. Evolutionary models of stars, because the time line is on the order of billions of years, can make it pretty hard to answer re the OP. I mean, if it is off by 250-500 million years no biggee on a cosmic scale, but it makes it hard to say on June 5th 1.5 Billion CE earth will not be habitable. Having said that, at some point, probably w/i 750ml-1.5 billion years, the sun will use up its hydrogen and expand (tho it has always been expanding). Under different models Earth could be then engulfed by the Sun, or it might get pushed out into a larger orbit and freeze as the Sun expands. Before either happens earth will have been uninhabitable for millions of years.
*There are unpredictable elements too – an asteroid crash for instance. Possibly also a man-made disaster i.e. some kind of biologically engineered super-virus, a nanotechnology accident or some kind of all out Nuclear exchange (talking about tens of thousands of high yield nukes) though hopefully extremely unlikely, and completely unpredictable re the terms of the OP – could theoretically make the Earth uninhabitable in the coming decades or centuries.
Eventually this is true but you’re going to have to wait a lot longer than 5 million years to see this. Our sun is middle aged right now and has around 4-5 billion years left to go before fizzling out. I don’t know when it’ll start on the heavier elements but I am reasonably certain you won’t see it really get going for another 2-3 billion years.
Note that once the sun does start on the heavier elements the greenhouse effect will be the least of earth’s worries. The sun will expand in size such that the earth will actually inside the outer layer of the sun. The earth will be a cinder at that point and I’m reasonably certain all life on the planet will perish.
First of all that show wasy pure hype, I’d bet anything that the creatures portrayed in the show will never, ever exist. Secondly, in five million years if humanity survives you can bet we’ll be all over the place. Certainly by then we’ll have mastered the planet’s enviornment, colonized other worlds, and who knows what else. By then Star Trek technology will be laughable.
On a related subject (the cheezy “Future is Wild” show), does anyone know a website with maps of what the world will look like after a few more million years of continental drift?
You can see that the Earth hasn’t changed a whole heck of a lot in the last 14 Myr (million years). They also give maps looking ahead 50 Myr, 150 Myr, and 250 Myr. At some point between these last two, the Americas will smush back together with Eurafrasia, giving us a new supercontinent.
You musta missed the first minute of the show. The show posited that within 5 million years, humans will have colonized other planets, and will have left Earth as a wildlife refuge. Earth will eventually be unihabitable for humans, probably about the same time it becomes uninhabitable for all advanced life.
In fact, those robot scout satellites that framed the segments of the show were launched by humans from a new planet.
The only part of that show that was more scientific than ‘a bunch of scientists sitting around over beers trying to guess what might work evolutionarily’ was the movements of the tectonic plates, so they know pretty confidently France is moving toward the Arctic circle, and that when two continents meet (Africa and Asia? - can’t remember) it’s gonna make for some really tall mountains.
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