Saturday, 17 March 2012

How to fend off a shark with a magnet

Through accident, experimentation and application, man have deterred pests and animals by various means. Pesticides and insect are a few from the vast arsenal of weapons. But what about when it comes to sharks?

Fending off sharks is no easy business, scientists have tried sprays, pulses of lights, visual tricks and even chemical sprays (how that works in water I've no idea).

But in 2005, scientists accidently discovered a way to send this massive predator away like people running from fire.

The discovery

yes that is a magnet, want to try?
In the Bahamas, researchers dropped a small magnet into a the water near a shark and noticed it darted away immediately.

They wanted to test this further.

They put the shark into a condition known as tonic immobility. A temporary paralysis that occurs when  fish lay in a certain position on their backs.

They dropped the magnet in and the shark recoiled away!

But why?

You should know that salt water is made of salt dissolved in water (duh). The Sodium ions in the water (from the salt) are positive and so when a magnet is near it a weak electric field is created.

Sharks have a special sixth sense called electroreception. This sense is used to detect prey and other fish.

The weak electric field disrupts their sixth sense and so they back off.

Why don't we just swim around with magnets in our pockets?

it's okay I've got my magnet!
Sharks are used to sensing the electrical activity in other fishes muscles, having a sensitivity of a billionth of a volt!

Now the electric field is a bit stronger than that, so shark's electroreception is overwhelmed sending them in the opposite direction.

However, the problem is how far they go!

Testing revealed that they only back off about a foot (0.3m) :(

Which means that in order to have a better effect, you'll need to carry bigger and stronger magnets placed all over your body, and there's no point swimming with an extra kilo or two in your pocket.

Furthermore sharks hunt in groups, which means that even though you scare one away, chances are there'll be another 5 after you!

Also if a shark is particularly hungry, I doubt he's going to be bothered by a little irritating magnet, he's more concerned about dinner!

So what now..

There are a few other repellents that can be used, some divers wear PODs or protective oceanic devices.

These create a similar field but works in a different way. However motion is known to affect it so it's not very effective.

A new idea came about when it was discovered that sharks stay away from rotting corpses of their own kind.

But I don't think you want strap decaying shark flesh to your ankles..

Instead, a chemical was extracted which can mimic the effect. However it's reserved for lifeguards only. So don't expect to be shark-proof any time soon!


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