Re: Cat's eyes

[Mark Sylvester <msylvest@XNET.IT>]

Indeed, Scott's observation sounds interesting but is something different
from the shining cat's eyes. As John D point's out, it's a retroreflection.
My guess is, the cat sees your kitchen light reflected from, say, your
eyeball. The reflection probably looks pointlike to the cat. The cat's
optical system forms an image on the cat's retina, but at the same time
projects back the reflection of the image-forming rays in the direction
they came from, i.e. directly towards your eye. I believe it's the layer
behind the retina that does the reflecting. Playing with a flashlight -
shining it at the cat while holding closer to or further from your own eyes
should give some insight.

So when you stop the kitchen light from reaching your glistening eyeballs,
the cat sees no reflection, and neither do you.

You could try further confirming this by closing your eyes - you should see
nothing at all. <grin>

Mark


At 19:52 03/09/00 , Ludwik Kowalski wrote:
> I was not wearing glasses.
>
> Scott Goelzer wrote:
>
> > I get the same thing, but only from my new glasses which have an
> > anti-reflective coating. I when I hold the glasses at a certain angle
> > and view a flor. bulb the reflection is distinctly green. When washing
> > the glasses a water film turns the reflection purple. I assumed that
> > this was some sort of  thin film interference, but I would be curious
> > about the details.
> >
> > Scott
> >
> > PS Your cat may not appreciate the second experiment ;-)
> >
> > > Date:    Sat, 2 Sep 2000 23:29:38 -0400
> > > From:    Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>
> > > Subject: Cat's eyes
> > >
> > > A very strange observation (9/2/2000, 10 p.m.).
> > >
> > > The lights are off in our living room. But the door to
> > > the kitched is open and the light there is on. I am
> > > standing in the living room and the kitchen door
> > > is on my right side. I am looking at our cat who is also
> > > looking on me. His eyes are shining like two little light
> > > bulbs. A strange green fluorescent-like light. The cat
> > > is directly in front of me, about 15 feet away (in the
> > > semi-dark room).
> > >
> > > So far nothing strange, I have seen shining cat's eyes
> > > before. But this time I noticed something very strange
> > > and highly reproducible. The moment I place my hand
> > > between the kitchen light fixture and ny eyes the cat's
> > > eyes stop shining. I lower the hand and they shine again.
> > > The fixture, which is about ten feet on my right side,
> > > consists of five 60W light bulbs each surrounded by a
> > > common white scattering sphere. It is at ~90 degrees
> > > with respect to the direction of my looking.
> > >
> > > There is enough of scattered light in the living room
> > > (coming only from the kitchen) to see the body of the
> > > cat. But his eyes are shining only when there is nothing
> > > between my eyes and the kitchen light fixture. The
> > > impression is that light from the kitchen is somehow
> > > "reflected" from my eyes toward the cat and causes
> > > them to shine. Why do I see the shining cats eyes only
> > > when my eyes are sidewise illuminated by the kitchen
> > > light?
> > >
> > > By the way, my exact position, or exact orientation,
> > > do not seem to be critical; moving forward or
> > > backward (or left and right) by one foot did not make
> > > any difference. I asked my daughter, who is 22, and
> > > she confirmed the observation. Can somebody
> > > confirm it on another cat? Is there a well known
> > > simple explanation of what happens? I am puzzled.
> > > Ludwik Kowalski
> > >
> >
> > --
> > *****************************
> > Scott Goelzer
> > Physics Teacher
> > Coe-Brown Northwood Academy
> > Northwood NH 03261
> > sgoelzer@coebrownacademy.com
> > *****************************


Mark Sylvester
United World College of the Adriatic
Duino TS Italy
+39 040 3739 255