BBC Knowledge Asia Edition - December 2014

What dangers will we face

if the magnetic field flips?

The magnetic field strength will drop to about

20 per cent of what it is now. This will increase

the radiation from space and increase cases

of skin cancer. However, we can act to protect

against that; it wouldn’t be a major killer. If

you look back at previous occasions when the

field has flipped, there is no evidence of that

coinciding with mass extinctions.

What about animals? Will it affect

their navigation?

There’s lots of evidence that animals use the

Earth’s magnetic field to find their way, but it

seems to be a secondary method. A flip would

produce a very different magnetic structure

• there would be no obvious north or south,
  for example. However, experiments that have

exposed animals to strong magnetic fields

show that they can adapt very quickly.

Would GPS be affected?

A weakened magnetic field means that we’d be

more susceptible to induced currents caused by

solar storms and we’d feel their effects more

acutely. Phenomena like those experienced

during the 1859 Carrington event [the biggest

solar storm on record] would become more

frequent. Telegraph operators at the time found

that communication worked better when the

system was turned off – the storm was

providing the current. The effect on satellites

can be seen in the South Atlantic Anomaly – the

weakest part of the Earth’s magnetic field.

Satellites flying over this region already go into

shutdown mode to prevent charged particles

from frying circuitry.

PROFESSOR

RICHARD HOLME
actually be a single north and south pole Researcher of Earth sciences at the University of Liverpool
at all. “The last time this happened was
around 780,000 years ago,” says David
Gubbins, Professor of Earth Sciences
at the University of Leeds. “Previous
flips have been preceded by a
dramatic drop in the strength of
the magnetic field. Perhaps it is
about to reverse again.”
To try to understand what’s
happening to our magnetic field,
geoscientists look to where it is
coming from: the Earth’s giant
iron core. Beginning about
2,900km (1,800 miles) below
the Earth’s crust, the core is
about half the size of the entire
planet. It is split into two parts:
the inner core and the outer
core. The inner core is
solid, but the outer core

What dangers will we f

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The magnetic field strength

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actually bbe ea asisngle north and souuthth ppole Researcher of E
at all. “The last time thihis hhappened was
around 7 80,0 00 years ago,” says David
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at the University of Leeds. “Previous
flips have been preceded by a

David Gubbins, Professor of Earth Sciences

at the University of Leeds

“Previous flips

have been

preceded by a

dramatic drop in

the strength of the

magnetic field”

Signs

of past

liquid water on

Mars were found

at Gale Crater by

the Curiosity

Rover

The

Earth’s solid

core acts as a

dynamo with the

liquid outer

core, causing a

magnetic

field