Re: A question about mirrors

[Jack Uretsky <jlu@HEP.ANL.GOV>]

See below:


On Fri, 4 Aug 2000, Michael Edmiston wrote:
______________________________________________snip_________________>
> Of course this all fails if we are communicating with an intelligent being
> who somehow lives in a very different physical universe than we live in...
> but that is not our assumption.
>
> I am not sure how astronomy is different from beta decay in terms
 of
> defining handedness?  In both cases we are agreeing on a
specific object,
> and a specific vantage point.

        OK.  How do you do this in astronomy?  You must first of all,
I think, communicate the idea "coordinate system" and then define
one.  This will already invoke the idea of "handedness", won't it?
        Next, let's recall that the notion connecting rotation
with a "pseudo-vector" is quite arbitrary - and probably unique
to us.

In the case of beta decay, the vantage point
> is defined by the asymmetry in the angular distribution of the beta
> emissions... then we can tie that orientation to the spin of the nucleus for
> the handedness discussion.  Likewise, spinning or revolving astronomical
> objects have specific angular momentums.  If that is true, then don't we
> just have to agree upon a common vantage point from which both observers
> view these?

        Sorry, I don't see how "specific angular momentums" helps.

> Also, since the "intelligent being" discussion is hypothetical,
 it's not
> clear to me how this discussion is taking place.  If we are having the
> discussion face to face, we can point to things.
        I am adopting Morrison's point of view that we are
communicating by radio with a distant intelligence.  The messages
are probably spaced a couple of hundred years apart (we should be
so lucky in our SETI search!).

 If we are not face to
> face, how far apart are we?  Are we communicating by E&M waves?  If so,
> doesn't our path of communication define a "line," and whether I am
> transmitting or he/she/it is transmitting define directions along that line?
> And can't we reference viewpoints to that line?  (Note: I put line in
> quotations to acknowledge some would not necessarily consider it to fall in
> the simple realm of a "straight line."  But I don't think that matters for
> the point I am trying to make.)

        The devil is in the details!


                                Regards,
                                        Jack