From: "Keith F. Lynch" <kfl at KeithLynch.net>
To: WSFA members <WSFAlist at KeithLynch.net>
Subject: [WSFA] Re: Conjunction
Date: Wed, 23 Dec 2020 19:52:30 -0500 (EST)

Tamar Lindsay <dicconf at dmarc-yahoo.com> wrote:
> Technically, the two planets are a bit closer than usual. They are
> both on the same side of the sun. When they are on opposite sides
> again, there will be significantly more distance between them.

They're on the same side of the sun, sure.  But they're closest to
each other, not when they're in conjunction as seen from Earth, but
when they're in conjunction as seen from the sun.  Or at least very
close to that time.  Their closest varies from 3.83 to 4.92 AU,
depending on where their respective perihelion's and aphelions line up.

For comparison, their most distant from each other -- as they will be
in about a decade -- varies from 14.23 to 15.33 AU.

3.83 differs from 15.33 by a lot less than a separation of 0.1 degrees
in Earth's sky differs from their average separation, 90 degrees.

> The deadly litter from various early satellites sent up around earth
> was sufficient to require careful plotting of flight paths for all
> subsequent launches.  I believe they have not yet all fallen down
> again.

Interplanetary travel in that novel is always done at greater than
solar system escape velocity, so litter won't be accumulating
anywhere.  It's not like low Earth orbit, which is not only an
enormously smaller volume, but which contains junk that's been
there for more than 62 years.