On Sat, May 26, 2018 at 08:48:06PM +0100, Timothy Collinson wrote:
> Is my calculation of a 40km horizon at height 200m on a size 5 world (let's
> say radius 2500 miles) about right? [1]

Yes, that looks fine for something like ocean or otherwise featureless
terrain.  If there are hills or mountains then they may block line of
sight to the theoretical horizon, or their upper parts may be visible
beyond it if the air is clear enough.

> I needed to name some TL4 explosives (on Pysadi, harvesting howood)
> and came up with quadroglycerine - it was supposed to be a sort of
> homage to triticale being turned into quadrotriticale for Star
> Trek's Trouble With Tribbles episode.  But is the nature of
> glycerine such that that's just completely ridiculous?

It does seem rather implausible taken literally, but it wouldn't have
to literally mean glycerol with four nitrations.  Probably the closest
compound analogous to that would be erythritol tetranitrate (ETN),
which is an occasionally used explosive.

Erythritol is the 4-carbon extension of glycerol's 3-carbon form, and
perhaps it might be naturally produced by the native biology in a
larger role than on Earth.  Erythritol is produced biologically on
Earth by some fungi, so it seems quite plausible to posit wider
availability for it in an alien biosphere.  That could make it a
natural choice for nitration to form an explosive on a TL4 world.

It's not out of the question for someone to use quadroglycerine as a
common name or a trade name for ETN by analogy with widely familiar
nitroglycerine which has much the same chemical form.

- Tim