Friday, November 02, 2012

Left Side of the Aisle #80 - Part 4

And Another Thing 2: Earth's magnetic field changing

One of the other things Curiosity has found is that water once flowed on Mars. There is just absolutely no question: Features on the surface of Mars exactly match features produced on rocks on sand by flowing water on Earth.

So looking at Mars today, knowing that Mars was more Earth-like in the past, looking at Mars today could give us some sense of what might be in our future.

Now, one of the things - it's not the only thing, but it's one of the big things - that protects, that allows for, life on Earth is that the planet is surrounded by a magnetic field. That field helps shield us from the solar wind and blocks some of the more intense cosmic radiation from deep space. It also helps existing life: For example, it helps birds migrate, with many species navigating along lines of magnetic force.

However, the magnetic field of the Earth is getting weaker: Its strength has declined by 10% over the past 150 years and scientists say that in as little as 500 years it could disappear entirely.

Now, that could be bad news, because the lack of a magnetic field on Mars is one of the reasons why there appears to be no life (or if there is, it is hidden). Losing the magnetic field, which happened on Mars billions of years ago, allows the solar wind - which is basically the flow of charged particles coming from the Sun - to blow away the atmosphere and what atmosphere is left is no protection against the cosmic rays so any life, if it did exist, would either have been wiped out or driven underground.

That's not likely to happen to Earth, because this business of the magnetic field weakening has happened before. What happens is that the field weakens, it almost disappears, and then it flips so that north and south reverse directions. It's happened several times in the Earth's history; in fact, it's happened about every 250,000 years according to the geological record - but which also means that, with the last event being some 800,000 years ago, we are really overdue for one of these flips.

The effects are hard to predict, but it's unlikely to cause any severe damage to life on Earth because the field will not completely disappear - but it could have a real impact on migrating birds, for example, which will have to learn other means of keeping track of their path, otherwise they might find it hard to do things like reproduce.

Something else that could occur is disruptions to electronic equipment and communications. Satellites could be disrupted (which means GPS gets disrupted), radio communications could be disrupted because a weaker magnetic field allows more of the solar wind and more cosmic radiation to penetrate. So while this might not affect our life, it might affect our technology.

The other thing is that when the poles flip, it's not just a matter of the south and north poles sort of rotating around the Earth until they have swapped positions. No, what happens is that as the field diminishes, you start getting all these little poles, north and south poles, popping up all over the planet. Which means a compass would be completely useless and any system or technology that relies on a compass would also be completely useless.

The European Space Agency is taking this seriously enough to be planning to launch three satellites next month to improve what is now our rather hazy understanding of what's called the magnetosphere, which is the name for that magnetic field that surrounds the Earth.


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