Time and Space in Traveller -- Units

[BRover]

One of the inconsistencies I've noticed in Traveller is the units of the world. In game explanations, that is. Why, for example, should Jumps so neatly correspond to Earth-weeks and parsecs? Even one being exact would be a strange coincidence, but both?

My answer is that they aren't, not quite. That is, they are close enough for many purposes, but not totally. We get similar coincidences--the apparent diameters of the Moon and Sun as seen from Earth are within a few percent, and 2^10 is very close to 10^3, so log (2) = 0.30103 . . . (There are plenty of others, naturally.)

Similarly, is it likely that a Jump (J-1) takes on average exactly 7 days = 168 hours and covers a maximum of 1 parsec? It seems more likely that these were "close enough"--and led to a re-definition of the terms, so that now one week is the average length of time of a jump, and one parsec is the maximum length that can be covered in one jump-1. So, IMTU, I redefined these, and jump one is at most 3.15 light years, taking (on average) 166 hours. (This has the advantage of giving a few extra hours for that trip between the jump-spot and the spaceport.) It removes a bit of the difficulty in believing coincidences, and blurs a bit the Earth-centered cosmos.

 

[aramis]

There are other unit differences in Traveller (hidden in CT/MT formulae), as well...
C=300 000 000 m/s, not 299 792 458 m/s
G=10 m/s² not 9.80665 m/s² (explicitly given as 10 on page 54 of The Traveller Book)

These were game simplifications.. and different levels of precision loss...
G is off by 1.971621297792%...
C is off by 0.069228559445%
Imperial Year explicitly defined as 365 days, no leaps. Day explicitly 24 hours, and hours 60 minutes of 60 seconds each. 31,536,000 seconds, vs Earth's 31,557,600.

If we assume C is correct, our G would be 9.813439 or so. And the hex size for a parsec might be altered, too... and the year is defined as 365 days.

I've always assumed that the year is that of Sylea/Capitol, not of Earth. And, since I noted the discrepancy, G and C, as well, being in Sylean units, not Earth units.

 

[Spinward Scout]

I had heard that one week in Jump Space was an out-of-game throwback to Play-by-Mail gaming where people only replied (?) or heard from the GM once a week.

 

[Condottiere]

It's now part of the DNA of the game.

I had a go at creating a algorithm for jump time, experienced and universe, that doesn't necessarily default at exactly one hundred sixty eight hours, just about that period, combined with exit point, but since we don't have precise star charts in real life, sort of pointless.

You could rule that jump drives don't cycle at the same rate, so the time varies slightly for each starship jump.

 

[BRover]

There are other unit differences in Traveller (hidden in CT/MT formulae), as well...
C=300 000 000 m/s, not 299 792 458 m/s
G=10 m/s² not 9.80665 m/s² (explicitly given as 10 on page 54 of The Traveller Book)

. . .

I've always assumed that the year is that of Sylea/Capitol, not of Earth. And, since I noted the discrepancy, G and C, as well, being in Sylean units, not Earth units.

I'd noticed or learned of some of these, but they failed to come to mind when I posted.

Still, the Sylea/Capital explanation would be yet another coincidence. I'd still prefer close--like within 5%, or even 1%, but not necessarily exact--only close enough for uplifted game porpoises.

 

[Grav_Moped]

I had heard that one week in Jump Space was an out-of-game throwback to Play-by-Mail gaming where people only replied (?) or heard from the GM once a week.

Sounds plausible. And the picaresque SciFi it was based on favored "world of the week" campaigns, with (one hoped) weekly sessions.

 

[whartung]

Why, for example, should Jumps so neatly correspond to Earth-weeks and parsecs? Even one being exact would be a strange coincidence, but both?

Because it's a game of adventure and exploration, not quantum physics.

Get on the ship from T-Shirt world A, fly in a week, dodging pirates, to T-Shirt world B, explore the world, avoid being eaten by a grue, bargain a cargo manifest, steal a secret document, get drunk in a bar with your buddies, brawl with some locals, and skip out to the next star system minutes ahead of the local lawmen. Hooting and hollering the live long day.

 

[Proneutron]

Why, for example, should Jumps so neatly correspond to Earth-weeks and parsecs?

You should REALLY ask, "Why do Earth-weeks and parsecs so neatly correspond to Jump space physics?"

THAT really bothers me.

 

[Condottiere]

Calculating the value of a parsec
By the 2015 definition, 1 au of arc length subtends an angle of 1″ at the center of the circle of radius 1 pc. Converting from degree/minute/second units to radians,

{\displaystyle {\frac {1{\mbox{ pc}}}{1{\mbox{ au}}}}={\frac {180\times 60\times 60}{\pi }}}{\displaystyle {\frac {1{\mbox{ pc}}}{1{\mbox{ au}}}}={\frac {180\times 60\times 60}{\pi }}}, and
{\displaystyle 1{\mbox{ au}}=149\,597\,870\,700{\mbox{ m}}}{\displaystyle 1{\mbox{ au}}=149\,597\,870\,700{\mbox{ m}}} (exact by the 2012 definition of the au)
Therefore,

{\displaystyle \pi {\mbox{ pc}}=180\times 60\times 60{\mbox{ au}}=180\times 60\times 60\times 149\,597\,870\,700=96\,939\,420\,213\,600\,000{\mbox{ m}}}{\displaystyle \pi {\mbox{ pc}}=180\times 60\times 60{\mbox{ au}}=180\times 60\times 60\times 149\,597\,870\,700=96\,939\,420\,213\,600\,000{\mbox{ m}}} (exact by the 2015 definition)
Therefore,

{\displaystyle 1{\mbox{ pc}}={\frac {96\,939\,420\,213\,600\,000}{\pi }}=30\,856\,775\,814\,913\,673{\mbox{ m}}}{\displaystyle 1{\mbox{ pc}}={\frac {96\,939\,420\,213\,600\,000}{\pi }}=30\,856\,775\,814\,913\,673{\mbox{ m}}} (to the nearest metre)
Approximately,

In the diagram above (not to scale), S represents the Sun, and E the Earth at one point in its orbit. Thus the distance ES is one astronomical unit (au). The angle SDE is one arcsecond (
1
/
3600
of a degree) so by definition D is a point in space at a distance of one parsec from the Sun. Through trigonometry, the distance SD is calculated as follows:

{\displaystyle \mathrm {SD} ={\frac {\mathrm {ES} }{\tan 1''}}}{\displaystyle \mathrm {SD} ={\frac {\mathrm {ES} }{\tan 1''}}}
{\displaystyle \mathrm {SD} \approx {\frac {\mathrm {ES} }{1''}}={\frac {1\,{\mbox{au}}}{{\frac {1}{60\times 60}}\times {\frac {\pi }{180}}}}={\frac {648\,000}{\pi }}\,{\mbox{au}}\approx 206\,264.81{\mbox{ au}}.}{\displaystyle \mathrm {SD} \approx {\frac {\mathrm {ES} }{1''}}={\frac {1\,{\mbox{au}}}{{\frac {1}{60\times 60}}\times {\frac {\pi }{180}}}}={\frac {648\,000}{\pi }}\,{\mbox{au}}\approx 206\,264.81{\mbox{ au}}.}
Because the astronomical unit is defined to be 149597870700 m,[9] the following can be calculated:

Therefore, 1 parsec ≈ 206264.806247096 astronomical units
≈ 3.085677581×1016 metres
≈ 30.856775815 trillion kilometres
≈ 19.173511577 trillion miles
Therefore, if 1 ly ≈ 9.46×1015 m,

Then 1 pc ≈ 3.261563777 ly

https://en.wikipedia.org/wiki/Parsec


Rather dependent on what one supposes is the Third Rock from the Sun's unique orbit.

So the Universe really does revolve around the Earth.

 

[BRover]

Because it's a game of adventure and exploration, not quantum physics.

Get on the ship from T-Shirt world A, fly in a week, dodging pirates, to T-Shirt world B, explore the world, avoid being eaten by a grue, bargain a cargo manifest, steal a secret document, get drunk in a bar with your buddies, brawl with some locals, and skip out to the next star system minutes ahead of the local lawmen. Hooting and hollering the live long day.

That's the game explanation, but not the in-universe explanation. I can accept it, but the exact equivalence is harder to explain.

 

[BRover]

Calculating the value of a parsec
By the 2015 definition, 1 au of arc length subtends an angle of 1″ at the center of the circle of radius 1 pc. Converting from degree/minute/second units to radians
. . .

Rather dependent on what one supposes is the Third Rock from the Sun's unique orbit.

So the Universe really does revolve around the Earth.

Yes, I get that. Again, this is exactly why I prefer it not be an exact equivalence, but a close-enough approximation, that the "parsec" gets redefined as "the maximum distance of a Jump-one jump."

Just as a "league" has varied definitions--or a mile (nautical vs. statute, and other historical forms). They were "close enough" to get on with. And, let's face it, "parsec" is rather arbitrary in the game--just a measure on the grid, that may (or may not) correspond very closely to the actual universe we happen to live in--not even considering the two vs three-dimensional state of the jump-space.

 

[Proneutron]

That's the game explanation, but not the in-universe explanation. I can accept it, but the exact equivalence is harder to explain.

How hard is to to explain? Player A asks why the values are what they are and you say, "Quit meta-gaming". . Seriously it was BOUND to be a value that corresponded to SOME planet in the galaxy. It it aligned with the values for Efate would they be asking???

 

[Grav_Moped]

The in-universe explanation is "It's something that's driven generations of the greatest Jump Space physicists in the universe to explore vast new reaches of chronic alcoholism and/or religion."

If that's not sufficient, "A Wizard Did It." The wizard, of course, being a particular advanced mutant Chirper, some 300,000 years ago. They had a peculiar fascination with Earth for some reason, and this may have something to do with it.

 

[Timerover51]

An author is going to use terms for distance and time which his readers are familiar with or which can be easily explained. If he does not, he is going to have a hard time getting his audience to relate to the story.

In the early days of "Astounding" science fiction magazine, an author by the name of Sewell Peaslee Wright had a series of stories about the Special Patrol Service where he sometimes mentioned a different way of keeping time, based on the system of another planet. The difficulty was he had to continually relate the given different time measure to Earth time measurement in order to be understood by the readers (see included quote from the September 1930 issue, which can be found on Project Gutenberg). While the stories are pretty good, the continual problem of explaining the passage of time is something that I find annoying. In his later stories, he drops the use of the different time measurement.

"Correct," I smiled. The Universal method of reckoning time had never appealed to me. For those of my readers who may only be familiar with Earth time measurements, an enar is about eighteen Earth days, an enaren a little less than two Earth days, and an enaro nearly four and a half hours. The Universal system has the advantage, I admit, of a decimal division; but I have found it clumsy always. I may be stubborn and old-fashioned, but a clock face with only ten numerals and one hand still strikes me as being unbeautiful and inefficient.

I have no problem at all with the various range of measurements, as they are all understandable without extensive and repeated explanations.

 

[whartung]

That's the game explanation, but not the in-universe explanation. I can accept it, but the exact equivalence is harder to explain.

My favorite quote from "The Terminator":

Sarah Connor: [disbelieving] Are you saying it's from the future?
Kyle Reese: One possible future. From your point of view. I don't know tech stuff.

This one quote adroitly addressed and hand waved away the challenges of time travel in storytelling.

"How come Jumps are 1 week long?" "Heck, I don't know, I'm just the navigator -- I don't know tech stuff. They just are."

 

[BRover]

Whereas I can say, "Actually, it averages 163 hours. If you need more precision, 163.36 hours. And the Imperial parsec is 3.21 light years."

 

[BRover]

I think this xkcd helped inspire me . . .

https://xkcd.com/1047/

 

[Straybow]

One of the inconsistencies I've noticed in Traveller is the units of the world. In game explanations, that is. Why, for example, should Jumps so neatly correspond to Earth-weeks and parsecs? Even one being exact would be a strange coincidence, but both?

The map parsec doesn't correspond to the Earth-centric parsec at all. For example, it is 2 map parsecs from Sol to Alpha Centauri, but only 1.35 pc in real space. None of the distances and positions on the Traveller map correspond with real distances and positions.