Birds and some other migrating animals seem to use angles to help them
PEOPLE CAN see the Earth's magnetic field, albeit unconsciously. The effect
is too small to be noticeable, but other animals may use their eyes in this way
to get their bearings, says a report in New Scientist.
The Earth's magnetic field lines vary depending where you
are. They always run south to north, but are horizontal only at the equator,
dipping in at a steeper angle the greater the latitude.
Birds and some other migrating animals seem to use these
angles to help them navigate, and one theory is that they do so using
German researchers investigated whether people's eyes are
sensitive to these field lines.
They measured the lowest level of light that people could
detect in a small spot straight ahead of them. They had people face south, west
and south south-west, and used a magnetic coil to create a horizontal
They then repeated the experiment with the Earth's natural
magnetic field, which in Germany is angled 70 degrees downwards towards the
When the field lines coincided with the direction of the
spot, which only occurred when people faced south in a horizontal field, the
threshold of brightness at which their eyes first detected a very dim light went
The effect was small but significant, say the researchers.
Although we are not conscious of it, the same probably happens when
photoreceptors in the eye are aligned with the Earth's magnetic field.
American researchers studying newts say the light compass in
them probably use specialized photoreceptors to detect the magnetic field lines.
Magnetic fields interact with spinning electrons, and could
theoretically influence photoreceptor chemicals at the quantum level, altering
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