Earth will be habitable for only 1.75 BEEELLION more years

[klr]

http://www.theregister.co.uk/2013/09/20 ... andidates/

Unless we meddlesome humans – or our follow-on Earth inhabitants – muck up our planet with a nuclear holocaust, runaway greenhouse emissions, or some other ecological disaster, our 4.54-billion-year-old home should be habitable for at least the next 1.75 billion years.

Well, there's always the possibility of chance encounter with some wandering asteroid or a visit by hungry Kanamits bearing a copy of To Serve Man, but if habitability due to the sun's output and expansion are the only considerations, we've got plenty of time left on terra firma.

"The Earth seems to be habitable for perhaps 6.29 billion years (Gyr), but this is excluding the influence of humans and our pesky habit of pumping extra CO2 into the atmosphere," blogs Andrew Rushby of the University of East Anglia, lead author of a paper (PDF) published on Thursday in the journal Astrobiology entitled "Habitable Zone Lifetimes of Exoplanets around Main Sequence Stars".

Rushby takes pains in his blog post to explain that the true motivation and purpose of his paper was to explore methodologies for determining the habitability of exoplanets that share earthlike characteristics, and not to make "a definitive statement" about our check-out time from our comfortable digs on Hotel Earth.

"We are not" making such a statement, he writes. "Earth is [our] test, our standard, our control. In reality we only validated the model against other more complex models for the Earth, and came to similar conclusion."

The Reg gives a respectful nod to Rushby's intent – and to his observation that "the press machine is a rapid, yet inefficient beast" – but setting a terrestrial deadline is too attractive a headline to let pass unexploited. So sue us.

But to be fair, Rushby's paper is far richer than mere Earth lifecycle dating. In it, he takes into account a broad range of exoplanetary variables, and concludes that a number of candidates may have habitable lifetimes that far exceed that of Earth. For example, he notes that Gliese 581d "might be clement for 42 Gyr! A huge amount of time."

A planet with such a long habitable period would have plenty of time to evolve advanced life forms, Rushby reasons, "if we make the assumption that evolution by natural selection is a universal constant, operating in a similar way in potential exobiological systems as it does on Earth."

Rushby suggests that future exoplanetary investigations – "or SETI campaigns" – might do well to focus on such planets, since the evolution of intelligent life is likely not a simple, few-billion-year affair. In his paper, however, he rightly cautions that "This tendency to view evolution as a progression toward increasing biological complexity and intelligence likely stems from an anthropocentric bias."

That said, he also reasons that if we want to search for extraterrestrial intelligence, it would be wise to rigorously analyze planets that have been around for awhile for evidence of, for example, organisms that have altered their planet's biosignatures to such an extent that they could be detected across interstellar space, since those life forms would "undoubtedly require some level of complexity beyond that of simple replicating molecules."

So if we're going to study exoplanets in some detail, we could do worse than to use Rushby's habitable-zone lifetime filter. After all, we only have about 1.75 billion years left to finish the job. ®

[mistermack]

I'm surprised. Most people expect the Sun to last for another 5 billion years as a main sequence star, and then become a red giant. I can't see why the Earth can't remain habitable for at least that long, unless it's going to move away into a colder orbit. Even if it does do that, the technology will be there to warm the planet by then.

In any case, people will have the technology to live in space by then, so we won't be tied to planet Earth any more.

[That Alien Guy.]

Your planet has about 0.125 A-cycles left before your sun reaches optimum level for fuel harvesting. That's about 3200 of your years, roughly.

[mistermack]

Your planet has about 0.125 A-cycles left before your sun reaches optimum level for fuel harvesting. That's about 3200 of your years, roughly.

Surely it would be much easier to harvest the vast clouds of hydrogen gas that float around in space in a cold state BEFORE they come together as a star? Or just harvest comets, or planets that are mostly water.
You wouldn't have to risk the temperatures and gravity well of an immense star.
I mean, if I was looking for firewood, I wouldn't go looking for a fire, to pull burning sticks from.

Just trying to help.

[That Alien Guy.]

Your planet has about 0.125 A-cycles left before your sun reaches optimum level for fuel harvesting. That's about 3200 of your years, roughly.

Surely it would be much easier to harvest the vast clouds of hydrogen gas that float around in space in a cold state BEFORE they come together as a star? Or just harvest comets, or planets that are mostly water.
You wouldn't have to risk the temperatures and gravity well of an immense star.
I mean, if I was looking for firewood, I wouldn't go looking for a fire, to pull burning sticks from.

Just trying to help.

Would you take advice on how to extract oil from your ocean floors from a retarded squirrel? No me neither. Besides, Stars are not solely what you currently think they are. I'd explain but I'm no singularity engineer and I might get into trouble.

[mistermack]

Would you take advice on how to extract oil from your ocean floors from a retarded squirrel? No me neither. Besides, Stars are not solely what you currently think they are. I'd explain but I'm no singularity engineer and I might get into trouble.

What you fail to take into account is the fact that god won't let you take our sun.
You see, we are made in his image, which isn't green and weird looking but oddly European, with a beard. No offence intended.
So you were just created for our benefit, like women, so you might as well start helping now, and we might decide not to exterminate your kind, but to keep a few in zoos, and some as pets.