In article <fvam2q$h71$1@[EMAIL PROTECTED]
>, Remus Shepherd
<remus@[EMAIL PROTECTED]
> wrote:
> So birds see magnetic north. Possibly only at dusk, when the
cryptochromes
> in their eyes are activated by the deep blue of the sky.
>
> I'm trying to imagine a sentient species with such an ability, and
what
> they might do with it. I'd expect them to ascribe religious qualities
to
> north and south, at least until their scientists figured out what the
colored
> lights in their vision mean.
Humans can see polarization in light.
http://en.wikipedia.org/wiki/Haidinger's_brush
Thus, if you can see blue sky, you can tell the direction to the Sun,
even if it is hidden behind clouds. This would be useful in polar
regions, where the Sun is always near the horizon, often hidden by
haze, but you can see sufficiently-clear sky straight up. This gives
you a sky compass without need of a Sunstone.
http://www.polarization.com/viking/viking.html
--
David M. Palmer dmpalmer@[EMAIL PROTECTED]
(formerly @[EMAIL PROTECTED]
@[EMAIL PROTECTED]
)
|
