From: "Vladimir Galogaza" 
To: "ATM shore" 
Reply-To: "Vladimir Galogaza" 


Some old facts related to recent postings:

>If light is invisible then how can we see it.

Light is per definitionem that part of electromagnetic spectrum which humans CAN SEE.
Our seeing capability is wonderful because it provides us not only with
detection but with imaging as well. Not all  living species are that lucky.
Some other portions of electromagnetic spectrum humans can feel, like heat,
but without imaging option.
We have no "built in" detectors for radio frequencies or gamma
rays which are also electromagnetic waves.

>Light doesn't interact with itself, so the intersecting beams don't
bother each other

It does. This is called interference. And intersecting beams bother each
other very much. In order to observe this though some very special
conditions must be met. If those conditions (temporal and spatial
coherence) are not met, interference effects are changing so fast that we
can not see instantaneous values of intensity and long term average value
is practically zero
as our "detectors" are concerned.

>Why don't photons bounce off each other

Indeed, they do.
But with low probability and therefore requiring high photon density. This
is called photon-photon scattering and yes this is "question science
is still studying".

>light actually does no move along it's path?  It's in waves,, just as a
wave in a pond travel.

Waves in the pond and light waves are different thing. In the pond we have
particles interconnected with some springy forces. We have oscillation of
atoms or molecules in matter. Light does not need matter to propagate.
 ( I think, but who knows with so much invisible and dark matter around).
At first  hypothetical "ether" was introduced  for substance
required for propagation
 of light but electromagnetic theory does not need it any more.
 Light is and propagates via oscillating electromagnetic fields. Changing
electric field
creates magnetic field by induction and changing magnetic field recreates electric
 field and so on.
And this interplay of fields is spreading itself in space so light moves indeed.
In some cases this movement can be described as movement of particles,
photons. But it is not that light is sometimes photons sometimes waves . It
is  description of it that has this dualistic character.

This is how things used to be long while ago. If in the meantime something
new happened I would appreciate to hear about it.
Vladimir.

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