Therese- it's always a little hard to answer 'what if' questions,
because all the laws of physics tie together, or at least we think they
should some day. So if you change one thing, you'd need different laws
and lots of things would be different.
But anyway, working from your premise:
If you looked a particular direction, you'd see light from lots of
different sources, because it could bend around to come in from the
direction you're looking. Probably the colors would end to wash out,
since they'd be mixtures of different colors. They wouldn't have to all
become white, however, since there could still be uneven distributions
of different colored objects in different directions. It sure sounds
like it would be hard to see clearly, thjough. Think of how hard it is
for us to judge the direction of things purely by sound.
Mike W.
Actually, light does travel just like sound in many respects. Sound
travels as a compression wave in the medium (air or water), while light
travels as electromagnetic waves. Waves follow Huygens's principle, and
when a wave impinges on an object with holes in it or an object with a
corner, the waves spread out from those places where they are allowed
to pass. The general name for this is "diffraction" and you can find
some answers on our web site about light going around corners.
The effect is small for very short wavelengths and very large
corners, and becomes more noticeable for longer wavelengths of light.
Radio waves, which are really just light waves with very long
wavelengths, diffract around corners just like sound waves do. If we
could see radio waves, this would be your world. Of course our vision
wouldn't be very clear, because the waves would just "slosh" around
people and houses and not give a nice, sharp image which can be
focused.
How much light diffracts by depends on its wavelength, and so does
the observed color. The reds will diffract more than the blues. This is
why you see a rainbow of bright colors when looking at diffraction
gratings on those metallized balloons, holograms on credit cards, and
some butterfly wings and fish scales.
Light bending around corners like sound is an important limitation
for people who etch transistors on computer chips using
photolithography. A material called "photoresist" is deposited on a
silicon surface and illuminated with light projected in a pattern
shaped like the structures desired on the chip. This light changes the
chemical bonds of the photoresist material, allowing it to dissolve in
a chemical bath in those places where light hit it, and not dissolve
where light did not hit it. Then acid is applied, which etches the
exposed silicon (or metal layer that has been deposited on the silicon)
but not the unexposed silicon, still hiding under the photoresist.
Transistors are currently made on silicon chips now routinely with
feature sizes on the scale of a tenth of a micron. That's about one
thousandth of the thickness of a human hair. The wavelength of visible
light is a crucial limiting factor in how small an image can be focused
on a piece of photoresist and still be sharp. Chip manufacturers now
use ultraviolet light, which has a shorter wavelength than visible
light, to push the feature size ever smaller.
Bacteria are experiencing exactly the world you are talking about!
Of course they don't have eyes which can focus (some are
light-sensitive, though), and there are other issues related to being
small (like water seeming to be more viscous).
Diffraction is the big limitation for visible-light microscopes and also for telescopes.
Good luck with your book!
Tom
(published on 10/22/2007)
