On 22 Oct 2015 at 12:18, Jerry Barrington wrote:

> Just to argue your basic premise, assuming you are walking about
> electromagnetic or sound emissions, the sum of emissions from 2 fixed
> & equal sources is *not* elliptical.  You are talking A+B, but the
> sum of emissions would be 1/A^2 + 1/B^2.

(Shhh! *They* don't know that)

More seriously, it's mostly a handwave anyway, and involves "magic"

Also, if I recall correctly, "waves" emitted from focus A will
converge to focus B and vice-versa.

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com