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ลำดับตอนที่ #93 : Can we sense invisible magnetic fields?
In
2006, an Arizona body-hacker named Steve Haworth sliced open Quinn Norton's
ring finger, slipped a small rare-earth magnet into the incision, and then sewed her up.
"If
I pick up a cord or
I ran my hand over my laptop, certain parts of it would just make my finger tingle," she said in
an interview with
NPR's All Things Considered (she originally wrote about it for Wired.)
"I'd
reach over towards something and I'd have this very sudden tingling in my finger
from a live phone cord. Phone cords aren't particularly high voltage but they're also
not very shielded.
So I could really feel them," she said.
Norton's
purpose wasn't to invoke
some superheroic ability to move objects like Magneto from Marvel's X-Men
comics. The idea was that the implanted magnet might allow her to detect the presence of
magnetic fields.
Here's
how it works: our fingertips are packed to the brim with sensory receptors, the nerve endings
that inform your brain about whatever it is you're touching. When exposed to a magnetic
field, that implanted magnet might move or vibrate just enough to activate
those nerve endings.
We're
all of course continuously bathed in a swirling soup of magnetic fields: from the Earth,
the Sun, our refrigerators, light bulbs, smartphones and television remotes.
Because electricity and magnetism are inextricably linked, anything that produces an
electrical current also creates a magnetic field, and vice versa.
The
sort of bodyhacking that Haworth and Norton involved themselves with a decade
ago was not meant to pick up on all those magnetic fields. As Norton explained
in the radio interview, she usually had to make physical contact with an object
to detect the magnetic fields radiating from it.
Animals
don't have to try so hard. Scientists have known since the late 1960s that some
birds navigate by taking advantage of the Earth's magnetic fields. For them,
it's thanks to biology and evolution, rather than minor surgery. Robins,
for example, have molecules in their eyes called cryptochrome which, when
stimulated by magnetic fields, can overlay magnetic information onto the birds' perception of the world by making some parts of
its visual field brighter and other parts darker.
They're
not the only ones. Pigeons have neurons that are sensitive to
magnetic fields, and loggerhead sea
turtles use
magnetic fields to migrate. Foxes seem able to rely on the small
magnetic fields that betray
the presence of hidden prey. Dogs apparently prefer to do their business with their bodies aligned on a north-south
axis, and zoologists can't quite agreeo
n whether or not herds
of cows and deer prefer to orient
themselves along the Earth's magnetic field lines.
Given
how broadly distributed magnetoreception (the ability to perceive magnetic
fields) is throughout the animal kingdom, it’s reasonable to ask whether humans
possess any such
skills. Surely we'd know if refrigerator magnets stuck to our skin, but it's at
least possible that magnetic fields influence us in subtler ways, perhaps even outside of our
conscious awareness.
In
1980, a British zoologist named Robin Baker published what would come to be
known as the Manchester
Experiments. "A wide range of animals are able to orient
toward home when subjected to displacement-release experiments," he wrote in the journal
Science. "When comparable experiments are performed on blindfolded humans, a
similar ability emerges." He was confident that this ability could not
have been due to the creation of a mental map or anything else. Homo sapiens,
he thought, had the ability to perceive Earth's magnetic fields.
He
loaded up minivans with groups of between five and 11 students from Manchester
University. Once in the van, all were blindfolded and driven along a "tortuous route"
to a release point somewhere between six and 52 kilometres away. Each student
was led out of the van and before they were allowed to remove their blindfolds,
they had to indicate the direction of the campus from their current location by
saying something like "north" or "southeast." Baker
repeated this 10 times with 10 different groups of students, and on average
they were indeed more likely to accurately point towards their starting point,
or close enough at least, than in the opposite direction.
Then,
apparently for the benefit of a TV film crew, he repeated the experiment. Only
this time, half of the participants had a magnet strapped to the backs of their heads. The other
half was instead given a piece of non-magnetic brass, though everyone was told
they were being given magnets in an effort to avoid biasing the results. Those
wearing the brass
bars tended to accurately indicate the direction home, replicating the first
experiment, while those wearing magnets did not, suggesting that the ability
could be easily disrupted.
While
the Manchester Experiments didn't conclusively prove that humans could sense
magnetic fields, they were certainly provocative, and they set off dozens of replication attempts
around the globe. But the initial findings may have been too good to be true.
Biologists
James L Gould and Kenneth P Able, for example, found that they were unable, in
eight different attempts, to replicate the effect. "We believe that our
consistent failures indicate that the phenomenon is neither as simple nor as robust as we had been inclined to hope,"
they wrote in Science. That's even
after they invited Baker to New Jersey to assist in the administration of the
experiments. But in a 1987 metanalysis,
Baker claimed that when all the replication attempts conducted in the UK, USA,
and Australia were combined into a larger dataset, his original findings indeed
held up.
Even
now, the Manchester Experiments remain controversial, but discoveries of a mineral called
magnetite in our brains andbones and of cryptochrome in our eyes have continued to push
researchers to search for evidence that we're able, somehow, to sense magnetic
fields. It's safe to say at least that if we do have that ability, however
slight, it's not been easy to prove. For now, the best way to demonstrate the
ability might just be to surgically implant magnets into your fingertips...
which is probably best avoided.
Incision (n.)
an opening that is made in something with a sharptool,
especially in someone's body during
an operation:
a wound or
scar made
by a surgicalcut
cord (n.)
(a length of)
rope or
string made of twisted threads:
a piece of
wire covered in
plastic, used to connect electrical equipment to a power supply:
a long structure in the body similar to a rope:
tingle (v)
to have a feeling as if a lot of sharp points are
being put quickly and lightly into your body
When you tingle with an emotion, such as excitement or fear,
you feel it very strongly:
shield (n.)
something or someone used as protection or providingprotection:
invoke (v.)
to use a law in
order to achieve something, or to mentionsomething in order to
explain something or to support youropinion or action:
especially a god,
when you want to improve a situation:
to make someone have a particular feeling or remembersomething
brim (n.)
the bottom part of
a hat that
sticks out all around the head
the very top edge of
a container:
(v.)
to become full of something, especially a liquid:
exposed (adj.)
having no protection from bad weather:
swirl (v.)
to (cause to) move quickly with a twisting, circularmovement:
inextricably
(Adj.)
unable to be separated, released, or escaped from:
vice versa
(adv.)
used to say that what you have just said is also true in the opposite order:
overlay (v.)
to cover something
with a layer of something:The tiny carvings were overlaid with silver.
Something that
is overlaid with something has a particularquality added to
it that influences its character
betray (v.)
to show feelings, thoughts, or a particular characteristicwithout intending to:
to not be loyal to your country or a person, often by doing something harmful such as helping their enemies:
aligned (v.)
to put two or more
things into a straight line:
herds (n.)
a large group of
animals of the same type that
live and
feedtogether:
a large group of
people that is consideredtogether as a group and
not separately:
orient (v.)
to discover the position of yourself in relation to yoursurroundings
to make someone familiar with a new place:
possess (v.)
to have or own something, or to have a particular quality:
(of a wish or an idea) to take control over a person's mind, making that person behave in a very strange way:
subtler (Adj.)
not loud,
bright, noticeable, or obvious in any way:.
achieved in a quiet way
that does not attract attention to itself and is therefore good or clever:
Displacement(n.)
the situation in which people are
forced to leave the
placewhere they normally live:
the weight of
liquid that is forced out
of position by an object that
is floating on or in it
tortuous (adj.)
with many turns and changes of direction; not direct or simple
route(n.)
a particular way or direction between places:
a method of
achieving something:
(v.)
to send something somewhere using a particular way or direction:
strapped (adj.)
not having enough money:
brass (n.)
a bright yellow metal made from copper and
zinc:
disrupted (v.)
to prevent something, especially a system, process, or event, from continuing as usual or as expected:
provocative(adj.)
causing thought about interesting subjects:
inclined (adj.)
likely or
wanting to do something:
having natural artistic, technical, etc. ability:
to have
an opinion about something, but not a strongopinion:
controversial
(adj.)
causing disagreement or discussion:
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