In article ,
craigm wrote:

Billy Burpelson wrote:

craigm wrote:
Billy Burpelson wrote:

Billy Burpelson wrote:


What I -did- speculate on is that a *portion* of the echo (the
echo's leading edge) will be QRM'd *right as it leaves the moon*
(the first 0.75 seconds of the echo) by the trailing edge of the
incident wave (its last 0.75 seconds). Therefore, either a
shortened echo (due to full cancellation of the 'overlap', which is
unlikely) or an echo with a distorted or weakened leading edge
(more likely) will ultimately reach the earth, depending on how
much out-of-phase cancellation at the moon end of the circuit
occured.
craigm wrote:

Your error is assuming that echo is modified by the incident wave. The
waves pass by each other without interacting.
You seem to be contradicting yourself here. Above, you say they will
"pass by each other without interacting". Below, you say "anywhere they
'overlap' you *will* see interference". [emphasis added].

When you try to observe the waves, using any method, you get the sum of
the two signals. So anywhere they 'overlap' you will see interference.
This is superposition.
I agree -- and if you read what I said above (or tried to say) was
addressing the overlap, which due to superposition, will either
constructively or destructively add; in either case, the 'overlap'
portion of the echo (leading edge) -will- be modified (or degraded or
interfered with, however you want to look at it) by the trailing edge of
the incident signal, and that portion of the echo, when received on
earth, will be perceived as such.

Aren't we really saying the same thing???


No it is not the same. The waves do not interact with each other. It is
the ability to observe them that is the problem. Where they overlap you
are
seeing the sum of two independent waves. When the wave moves beyond the
overlap, it has not been changed. Outside of the area of the overlap,
there is no evidence of the prior overlapping.

Sorry, I respectfully suggest you might be incorrect here. In your
second paragraph, you say "So anywhere they 'overlap' you will see
interference.This is superposition". I agree with that.

I think all of us agree that because of the timing of the signal, the
last part of the incident wave will 'overlap' the leading edge of the
echo, just starting to head back to earth. Per YOUR statement above,
they are overlapping and thus will 'interfere'. (and by 'interfere', I
mean your 'super positioning' will cause the leading edge of the echo to
be 'distorted', either because of constructive or destructive addition.

The overlap is -not- modifying either wave. It is the ability to observe
that leads to the perception of distortion. Perhaps some poor analogies
will help.

1) Two ships are traveling towards each other on the ocean. You see them as
silhouettes. As they pass each other, the silhouette you see is the
combination of the two. Your view is therefore distorted. Once they pass,
there is no overlap and each is unchanged.

2) Take two light beams, one red and another green. Cross them so they form
an "X" and in the distance they shine on a wall. The red beam will cause a
red spot to appear on the wall, the green beam will form a green spot on
the wall. If you hold a piece of paper in the beams where they cross you
will see a different color. This is because of the superposition of the two
beams. They pass through this overlapping region and are unchanged.

In both cases, you see something different at the overlap, but the original
items are unchanged when they leave the overlapping region.


This distorted front edge of the echo will continue on to earth along
with the un-molested last part of the echo. Once the overlap/super
positioning has created the distortion (or interference or whatever you
want to call it), it will stay there.

You have to understand the meaning of the words I used. Note I used the
phrase "try to observe the waves". The problem is that by trying to look at
what is going on at a specific location, you don't see the bigger picture.
Looking inside the overlap you appear to see a distorted wave when you are
actually looking at two independent waves that get added together by
whatever you are using to observe them. Once they get past each other they
are unchanged.

It is not that the waves are changed. The limitation is in your ability to
observe them.

How can you 'UN-ring' a bell that
has been rung?

That is a totally different thing. When you ring a bell you are applying a
force to the bell. You are interacting with the bell. Overlapping waves are
not interacting with each other.

What I find interesting here is how long your patience will last. I
doubt more examples will help. I'm done with Mr. Burp. Good luck.

--
Telamon
Ventura, California