ForeSight has rules for the altitude ceilings of aircraft. Those need modifying for air pressure and scale height.
The generation run that I used to produce the universe for Flat Black has a couple of worlds where the air threatens oxygen toxicity or nitrogen narcosis or both at sea level, and you need to go up for breathable air.
All the uses I have run across for scale height have involved the use of a calculator, and I don’t see any advantage of using 8.5 km instead of 1 km as the unit of altitude in such calculations.
I’ve dealt with the rocket equation in a system in which acceleration was in gee and speed in miles per second, implying ≈162 miles as the unit of distance, and about two minutes forty-two seconds as the unit of time. It was a pain. Fucking around with randomly-selected units is not clever. Jon Zeigler nearly drove me crazy fixing up tidal calculations in a system where the two units of mass were the solar mass and the Earth mass, and the three units of length were the diameter of Earth, the diameter of the nearest planet, and the range of the lunar component of Earth’s deep-water equilibrium tide. Use SI, dammit!
For figuring out what the experience of being on the planet is like, Earth-relative units are helpful; “1.25 G” is easier to interpret than “12.2 meters per second squared.” For doing astronomical, physical, or engineering calculations, actual physical units are superior (mksA for preference!). The uses are different, but both exist. But it seems to me that people who care only about experience will include many for whom the conversion will be a daunting task, especially if they have to do it repeatedly for different physical variables, whereas most of the people who want actual physical units will find it trivial to multiply an Earth-relative unit by a constant. And of course the sensible thing to do is convert everything at the start of the calculation.
If you have room to give both sets of numbers, fine; it does make things easier. But if you’re concerned about space on the page, I’d be more concerned about deterring the unmathematical.
Ease of use for players is paramount. If folks need a calculator and a reference table to compare a number to their practical experience it is very very likely they won’t bother or will get it wrong.
As for the Watsonian viewpoint, I would expect the Empire to use comparisons to pre-kablooie Earth as a yardstick instead of scientific units (not tourist friendly) or comparisons to any existing or former colony. It’s about as neutral as you can get in FB, everyone’s’ ancestors are from there, and it implies parental authority without explicitly stating it.
Toxic units suck. About half the possibilities are so transparently awful that Bill and Roger were startled when I pointed out that the consistency they mentioned implied day length not be in hours, ocean cover not be a percentage of world surface, and that population not be a number of people.
And no-one will ever use scale height for any purpose that doesn’t require a calculator.
Here’s a list of the quantitative data that I am presenting without any unit in which Earth’s values is 1 or 0. Pick your battles.
Day length in hours
Partial pressure of oxygen. (I give it in bar.)
Scale height of the atmosphere
Ocean cover
Tidal range
Average surface temperature
Escape speed
Altitude of low orbit
Period of low orbit
Population
Population density
Development level
Purchasing power of the local currency
Exchange value of the local currency
I really, really object to the suggestion of creating three new units of length and a new scale of temperature. I will revisit the issue of tidal forcing later, because tides vary so much from the global mean that that figure is not actually measured. But I will never list scale height in units of 8.5 kilometres, and certainly not in the same document as in which I list altitudes in units of 150 km and orbital periods in units of 89 minutes. I reject your implication that those units are familiar, and I also reject your argument that scale height might ever be of use to a person afraid of using a calculator.
Robert Heinlein once likened censorship to making grown men live on skim milk because the baby can’t chew steak. The point applies to dumbing down science fiction for people who haven’t been on speaking terms with science since the ninth grade. Let them eat Star Trek, or spit out the gristle. I won’t give up my steak when that’s not even necessary for them to have their pap.
That’s an interesting idea, but I’m not sure how useful it is to compare a global average to either the Indo-Gangetic Plain or the Darling Basin. I’m more inclined to exclude ice sheets and land with an average annual temperature over 30 °C from the land area when making the calculation.
The population density I care about as a GM is probably a range of densities people on this world actually live at. OK, for many places that’ll be the same (normal countryside)-(normal city), but if it isn’t that’s interesting.
° I don’t see any problem with giving day length in days, but I don’t object to hours; everyone knows that a day is 24 hours.
° For total pressure, my preference is either kPa (that’s what my physics and courses used) or atm (that’s what my chemistry courses used); I use bar so little that I had to look it up. But for partial pressure, while I could manage either whatever pressure unit you use, or a ratio to Earth’s partial pressure, I think what I would like best is a percentage of total pressure.
°If there is room, I might like to have v_esc given both in m/s and as a ratio to Earth’s v_esc. But that’s just because I haven’t memorized any figure except “seven miles a second” and I’m lazy and don’t want to look it up. I could live with just having the figure for Earth listed in the frontmatter.
I’ve conceded your point about scale height, and there’s nothing else that I would feel much need to see as a ratio to Earth.
For population density, I think I would actually like to see two figures: Percentage of planet’s land area that’s settled (as opposed to just being habitable) and density of the settled part. That would be more informative than having them combined, just as your treatment of atmosphere is more informative that just saying “thin” or “dense” or whatnot. Is this doable?