Parsecs in Star Trek - are they what we think?

[Mytran]

Parsecs have been touched on only briefly in other threads - even this one veered off into a discussion on Terra-centric weights & measures. What I'd like to try here is something different, to better tie together Warp Speeds in the different incarnations of Trek.

As you probably know, Parsec is an abbreviation for parallax of one arcsecond and is a technique invented in 1913 which allows astronomers to measure the distance of various objects in the night sky, from planets in our own solar system to far off stars. It utilises the basic rules of trigonometry combined with the orbit of the Earth from our Sun and is explained far better on this Wikipedia page than I ever could, although pictures always help:

​

The practical upshot of this is that 1 Parsec = 3.2615638 light years. The term often got bandied around in science fiction, probably to avoid the characters saying "light years" all the time (and the associated misinterpretation that the latter were a measurement of time, not distance). In Star Trek "light year" (LY) was by far the more common term but it is interesting to see that in virtually all of Parsec's significant appearances it was used to express unusually massive units of distance; enough to skew the Warp Speed charts and make TOS (as it occurred there most often) appear as a continuity orphan in terms of speed and distance that its ships travelled. Speaking of speed and distance, here are the two Warp speed charts I will be consulting during this exercise, the standard TNG chart and the TOS Warp-Factor-to-the-power-of-five chart (it goes without saying that the TOS WF-cubed system is too slow for anyone's purposes and bears no resemblence to Warp speeds on any of the series):

NOTE: I mentioned the "significant" uses of parsec above as there many more uses where the term is just mentioned in passing, or in ways where specific times or distances were not a major problem. I'll deal with those another time, so here are the significant uses and their problems:


ARENA

• First captain's log is SD-3045.6, on the planet.
• The Enterprise then pursues the Gorn ship for a while at Warp 5
• Increase speed to Warp 6 some time before SD-3046.2
• This means that 0.6 SD units (maybe half a day) has passed since the first log entry
• Mr DePaul then reports that they have travelled "22.3 parsecs beyond the latest chart limit".

22.3 Parsecs is 72.732 LYs. Even if Cestus III was right on the edge of their charts and they were travelling Warp 6 most of the way, this would place Warp 6 at 44,276(c) - this meshes well with the WF^5 system but very badly with everything else!

At the end of the episode the Enterprise is flung 500 parsecs (1,631 LYs) away from the Metron system. Even at WF7 using the WF^5 system, this distance would take 35 days to cover. Either they got flung WAY past the Cestus III system (I sure hope they left plenty of supplies for the medical staff there) or the Enterprise covered a hell of a lot more ground than we thought in pursuit of the Gorn ship!

Incidentally, this is also the same episode where, having been stopped at the edge of the Metron solar system, Spock declares that Kirk could be out there anywhere "within a thousand cubic parsecs of space". I suppose Spock could just be using flowery language, but that seems very large for a solar system!

CONCLUSION: I don't thing a Starfleet "parsec" is the same as ours.


BREAD AND CIRCUSES

• Tracking the wreckage of the SS Beagle, Chekov informs Kirk that the planet is "only 1/16 of a parsec away" and that they should be there in "seconds". Sure enough, after only 30 seconds of continuous dialogue later they are in orbit!

1/16 parsec = 1,928,548,500,000 kilometres, which the wreckage drifted in only 6 years! By contrast, the Voyager 1 probe has only gone 18,514,066,000 in 37 years. The Beagle's wreckage must have had a hell of a boost at the start, it "drifted" 642 times faster!
Anyway, how fast does the Enterprise need to be to correspond to the episode:

• 1/16 parsec in 30 seconds is 214,329(c) or Warp 11.6 on the TOS-WF^5 scale
• TNG's Warp 9 would take 4243 seconds (71 minutes) to cover 1/16 parsec, hardly the "seconds" that Chekov promised.

CONCLUSION: I don't thing a Starfleet "parsec" is the same as ours.


WHERE SILENCE HAS LEASE

• Trying to leave the void, Picard leaves under Impulse power
• One flyby and 25 seconds later, Wesley and Data confirm that they should have travelled 1.4 Parsecs (4.566 LYs)

If we are generous and say that we skipped ahead an hour during that flyby, then the Enterprise-D at Warp 2 is travelling 40,027(c)!!!

By contrast, Warp 2 on the TNG scale would take 167 days to travel the same distance - I really don't think Picard waited 5½ months before checking on their progress!

CONCLUSION: I don't thing a Starfleet "parsec" is the same as ours.


CLUES

• After passing through the wormhole, Riker reports that they have moved 0.54 Parsecs (1.761 LYs) which is almost a day's travel.

If we round it up to a full day, that's 643(c) or just under Warp 7 under the TNG scale (full Warp 7 would be 0.55 Parsecs a day).
So, is Warp 7 their standard crusing speed then? Maybe, but Riker doesn't specify was speed a typical "day's travel" would use. He could be using a lower "standard ship" sort of formula that we're not aware of.

CONCLUSION: A Starfleet Parsec may or may not be the same as ours, insufficient information.


CONCERNING FLIGHT

• Janeway is in the marketplace, searching for her stolen computer core: "I have a client who runs a colony about twenty parsecs from here. His computer is outmoded so I'm looking for a replacement."

20 Parsecs is 65.2 LYs. At Warp 6 (TNG scale) this would take her 58 days each way. Seems a little distant...

CONCLUSION: I don't thing a Starfleet "parsec" is the same as ours.


SO, HOW BIG IS A STARFLEET PARSEC?

Since this is entirely speculative, it can be anything we like! With the advent of starships and FTL sensors we can suppose that the term "Parsec" fell into disuse some time prior to the 23rd Century, only to be revived later as meaning something completely different. Light Years on the other hand seem to be fairly ubiquitous and standard throughout the galaxy (understandable, since most naturally occuring Class-M planets would need to be a simliar size and distance from their sun).

So, let's try 1 Parsec = 1% of a Light Year:

ARENA: Enterprise covers 0.73 LYs before Kirk increases speed to Warp 7 and then a sustained Warp 8. It would mean the entire chase lasts a day or two in order to realistically cover the distance to the Metron system (unless it was very close to Cestus) but that's OK.
The distance Enterprise is flung at the end would reduce to a more manageable 442.76 LYs. Unfortunately that is still several months journey at Warp 8. Maybe Sulu knows of a Subspace Highway they can utilise?

BREAD & CIRCUSES: The wreckage of the Beagle is now a mere 5,912,929,701 kilometres from the Roman Planet - still twice as fast as the Voyager probe, but much less ludricously speedy!

WHERE SILENCE HAS LEASE: The Enterprise need travel no more than 0.04566 LY before Picard's enquiry. If he waits an hour, that is 400(c) or approximately Warp 6 (TNG scale). Picard could well have increased speed during the flyby and we only saw the latest of several update reports.

CLUES: If nearly a day's travel is 0.54 Parsecs, that would be 1.97(c). That's a very slow speed for Riker to use for his comparison, but not impossible - the spell of unconsciousness may have made his brain too foggy for more complex maths.


CONCERNING FLIGHT: Janeway's fictitous colony is now 0.652 LY away which places it outside the solar system but not far enough out to be in a neighbouring system. However, the colony could arguably be a mobile one (like the Varro generational ship), would would further their need for a decent computer core.


In all in all, I think a lot of scale problems are solved if the term "parsec" gets a makeover.

Thoughts, anyone?

 

[The Wormhole]

At least Star Trek remembers parsec is supposed to be a measurement of distance, unlike a certain other well-known sci-fi franchise...

 

[F. King Daniel]

I think Trek's speed/time/distance calculations are irreparably screwed. Why should viewers care more than the writers do?

 

[C.E. Evans]

I think a lot of measurements in Trek is based on plot, so a parsec (or even a light-year) is as big or as small as a story requires it to be, IMO. I doubt that many Trek writers use a calculator when working on the episode scripts.

 

[Autistoid]

I think Trek's speed/time/distance calculations are irreparably screwed. Why should viewers care more than the writers do?

Because it's called good writing.

Could you imagine how quickly someone would throw out a novel, if for dinner a parisian walked to tokyo and and than spent six years driving to spain?

This kind of stuff happened all the time and was part of the reason the franchise fell apart. The brand value and the cohernence of their world building is very important.

We all seen what happened to star wars when casual disregard for world building influenced production.

 

[T'Girl]

The current statute mile is different (longer) than the old Roman mile, similarly the parsec we currently use might be to be the "old parsec" by the 23rd century.

 

[Mytran]

Exactly my thoughts, T'Girl, thanks for phrasing it so well.

I think Trek's speed/time/distance calculations are irreparably screwed. Why should viewers care more than the writers do?

Because it's called good writing.

Could you imagine how quickly someone would throw out a novel, if for dinner a parisian walked to tokyo and and than spent six years driving to spain?

Good example Autisoid! And KingDaniel, you may call me hopelessly optimistic, but I believe the speed/distance thing in Trek is not as screwed up as you fear

The redefinition of "parsec" was an easy fix to bring the more outlandish distances in Trek into line with the rest, which I'll be looking at more closely in the near future.

I think a lot of measurements in Trek is based on plot, so a parsec (or even a light-year) is as big or as small as a story requires it to be, IMO. I doubt that many Trek writers use a calculator when working on the episode scripts.

I can't deny that Warp 4 one week may not be same as Warp 4 the next. However, I'm going to borrow from other thinkers here and utilise naturally occurring "subspace corridors" to explain those differences: These are regions of space which are either much more or much less susceptible to interference from Warp Engines. The practical upshot is that by picking the right areas of space to warp through you can achieve much greater velocities with far less energy than you would otherwise require (the reverse can also be true). I was reminded of this (fanon) phenomenon recently when revisiting the excellent Waxing Moon website - they also posit just such a corridor between Earth and the Klingon homeworld, explaining the oddly fast travel time both in Broken Bow and ST:ID!

These "subspace corridors" also mean that Starship navigators have to really work to make best use of local conditions - far more than just point-and-click

 

[martok2112]

At least Star Trek remembers parsec is supposed to be a measurement of distance, unlike a certain other well-known sci-fi franchise...

If you look at that scene closely, you'll realize that Han was just trying to see if he could get one over on whom he thought was a feeble minded old man, and a "wet behind the ears farmboy" who didn't know a parsec from bantha puduu. Look at the look on Kenobi's face, and you'll see the expression: "Really, Captain Solo? I was born during the day, but I wasn't born yesterday?"

 

[Timo]

Are there units that have changed definition by an order of magnitude or more? (There's "mil", which may be a thousandth of an inch or then ten kilometers, but that's not a case of the name acquiring a new meaning, just a case of two different teams picking competing definitions.)

I think Trek's speed/time/distance calculations are irreparably screwed. Why should viewers care more than the writers do?

I'm curious - where does that "24 hours from Earth to Qo'noS and back" thing come from?

The dialogue gives few hints of passage of time - Kirk launches to his mission ten hours after Pike's death, then estimates that the extraction of Harrison will take two hours (it probably takes longer, what with the complications), then chats with Khan, opens a torpedo, and then Admiral Marcus arrives. And Kirk doesn't yet conclude that Marcus has a superfast ship, but he does at least pretend that Marcus is responding to the warp core trouble, hence enough time has elapsed for a regular ship to fly from Earth to within half an hour of Qo'noS twice (first Kirk, then Marcus). So we get a lower limit, but nothing in the way of an upper limit. Might be 12 hours, might be 12 days.

Then there's the trip back, where we can insert only minutes after the "At least we're moving again" bit, and it's an odd thing to state if hours have already passed since departure. But that's only to be expected: if one is in moderate hurry from A to B, and great hurry from B to A, the rules of warp make the latter trip ten, hundred or a thousand times shorter in duration, depending on how many warp factors the skipper dares ratchet up the drive. So far, no other skipper has been in a hurry to get from the Klingon capital to the Human one before, so we have little idea of how long it ought to take for a ship with no known value for top speed.

Timo Saloniemi

 

[F. King Daniel]

"One day I've been off this ship, one bloody day!" - which gives us the time from Scotty's resignation until the Enterprise is falling to Earth.

 

[Timo]

Ah, gotcha. Thanks!

Timo Saloniemi

 

[C.E. Evans]

I think a lot of measurements in Trek is based on plot, so a parsec (or even a light-year) is as big or as small as a story requires it to be, IMO. I doubt that many Trek writers use a calculator when working on the episode scripts.

I can't deny that Warp 4 one week may not be same as Warp 4 the next. However, I'm going to borrow from other thinkers here and utilise naturally occurring "subspace corridors" to explain those differences: These are regions of space which are either much more or much less susceptible to interference from Warp Engines. The practical upshot is that by picking the right areas of space to warp through you can achieve much greater velocities with far less energy than you would otherwise require (the reverse can also be true). I was reminded of this (fanon) phenomenon recently when revisiting the excellent Waxing Moon website - they also posit just such a corridor between Earth and the Klingon homeworld, explaining the oddly fast travel time both in Broken Bow and ST:ID!

These "subspace corridors" also mean that Starship navigators have to really work to make best use of local conditions - far more than just point-and-click

Preaching to the choir. I've being using that idea to wave away any inconsistences for over a decade now (first heard about it in an old issue of Starlog back in the '80s)...

 

[Mytran]

That's fascinating, I did wonder where that idea originated from. I'd heard that it featured on one of the published maps, but it's nice to be able to trace it back further.

 

[The Wormhole]

This kind of stuff happened all the time and was part of the reason the franchise fell apart. The brand value and the cohernence of their world building is very important.

No. Whatever else led to the downfall of the Trek franchise, it most certainly wasn't misusing science terms. In fact, the overwhelmingly popular Trek XI is a movie in which the director blatantly ignored science and threw out an earlier draft which allegedly included proper science. How can the franchise have been saved by the very same thing you claim caused it to fall apart?

At least Star Trek remembers parsec is supposed to be a measurement of distance, unlike a certain other well-known sci-fi franchise...

If you look at that scene closely, you'll realize that Han was just trying to see if he could get one over on whom he thought was a feeble minded old man, and a "wet behind the ears farmboy" who didn't know a parsec from bantha puduu. Look at the look on Kenobi's face, and you'll see the expression: "Really, Captain Solo? I was born during the day, but I wasn't born yesterday?"

Hmm, interesting interpretation. In fact, after reviewing Wookiepedia, it seems George Lucas claims something similar was his intent, that Han didn't know what he was talking about and said parsec, not knowing what it meant.

Although, the EU of old did actually try to explain how it is possible to do the Kessel Run in only twelve parsecs, though that is of course no longer canon.

 

[Albertese]

...

Although, the EU of old did actually try to explain how it is possible to do the Kessel Run in only twelve parsecs, though that is of course no longer canon.

And I thought it was a clever explanation. For those of you who don't know it, the idea is that the Kessel Run is a shortcut through an area of space riddled with black holes. All ships in hyperspace move at about the same ludicrous speed*, but the trick is to plot the shortest course. So the Falcon is the best in that is has a super good navi-computer that can plot "safe" courses closer to black holes than most other ships and therefore can make it though the Kessel Run on a path as short as twelve parsecs.

Meanwhile... back to Star Trek...

--Alex


*All ships in hyperspace going the same speed is one of the ways George Lucas explained it once. But that doesn't seem to jive with "she can make point five past light speed" which is explained as multiplier effect in the WEG Star Wars Role Playing Game and has been accepted by many since.

 

[Starborn Dragon]

Actually, I for one did not know that about the parsecs. Thanks for the info.

However, keep in mind, parsec are completely and possibly even irrevocably irrelevant to the speed of plot.

 

[Mytran]

Not so much irrelevant to the speed of plot, but most of the time just a unit of measurement that sounded sufficiently "spacey" and really doesn't have to be 3.26 light years at all. Here is a list of the less significant parsec references I mentioned earlier:

ALTERNATIVE FACTOR: The Admiral evacuates all Starfleet units and personnel within a hundred parsecs of the Enterprise, as a safety precaution. 326 LYs would take nearly a year at TNG's Warp 6 or 15 days on the WF^5 scale. Small parsecs would work much better here.
(actually, I should have included this episode on the first list, I think!)

TROUBLE WITH TRIBBLES: Space station K-7 is within a parsec of the nearest Klingon outpost, "close enough to smell them". Since they already established K-7 to be near the border though, the actual distance in KM is not important, just that there is some distance.

ENTERPRISE INCIDENT: Spock scans first ½ parsec then 1 parsec, looking for any pursing Romulans. Again, the actual distance is not important, just that he is scanning and needs a suitable piece of dialogue.

THOLIAN WEB: Enterprise is flung 2.72 parsec away from the Tholians. Again, the precise distance is not necessary, just that they are out of harm's way.

UNNATURAL SELECTION: There are no vessels of any kind within 2 parsecs of the infected USS Lantree - again, precise distance is irrelevant to the plot.

TIN MAN: They are following the path of the Vega Nine probe to the Beta Stromgren system, 23 parsecs beyond the furthest manned explorations. Since we don't know how long the probe took to traverse the distance (or when), the exact distance is again irrelevant.

TRANSFIGURATIONS: John Doe is revealed to have come from a solar system 2.3 parsecs away (7.5 LYs) which is on the Enterprise's flight path. However, no journey times are mentioned.

JETREL: Neelix says of Jetrel "I don't want that man within ten parsecs of me!" but that's just a more "science fictiony" version of something we would say today. Irrelevant.

THRESHOLD: After Tom's shuttle vanishes, Harry Kim does 3 full sensor sweeps and finds nothing within 5 parsecs.

THE SWARM: After being rescued, Chardis says that he comes from a yellow dwarf system, 5 parsecs away. This does work better with larger parsecs, since the "swarm" is so virulent. However, Chardis is on death's door and suffering cranial trauma, so how would he know his exact position in space?

YEAR OF HELL: At one stage Annorax almost fully restores the Krenim Imperium, which spans 5,000 parsecs. At 3.26 LY/pa, this is double the size of the Federation (ST:FC) and would rival Borg space! Maybe smaller parsecs would be better?

WAKING MOMENTS: One of the dream aliens tells Chakotay that there is a 6 planet system less than a parsec away, which Voyager can be past in one day. At TNG Warp 8, this is true. However, this entire scene is all one of Chakotay's dreams, hence inconclusive.

TIMELESS: The ship crashes within "a few" parsecs of the Alpha quadrant. Since travel time is not mentioned (and they're using an experimental super-fast drive system anyway), this notation is irrelevant.

THE DISEASE: Tal wants to explore the Natori system - three months ago they passed within a parsec of it, now she wants a closer look. Again, this is one of those situations where "parsec" is used as a spacey-sounding term without relevance.

FURY: The Doctor mentions that Voyager is the only Vidiian "organ bank within half a parsec". 1.6 LYs is nothing in interstellar terms, are the Vidiians really going to restrict their search patterns to such local distances? As such, this reference can worth with either short or long parsecs.

DRIVE: Irina comes from a small trinary system about half a parsec away. As with FURY, this is a really short interstellar distance and well within range of Voyager's sensors anyway.

FLESH AND BLOOD: The rebel hologram Iden says he came from a Hirogen outpost about 15 parsecs away. However, we have no idea where in the galaxy the holograms' ship is supposed to be right now, so distances are irrelevant.

RENAISSANCE MAN: Fake-Janeway tells Chakotay about a fictitious race who's territory extends "thousands of parsecs from here to the edge of the Beta Quadrant". Larger parsecs would work much better here, but since it is really The Doctor saying this (and he's making it up under pressure anyway), I'd be inclined to disregard the whole statement.

DOCTOR'S ORDERS: Doctor Phlox is reading from the Warp Engine technical manual; "Output must be confined to within three hundred and three hundred twelve millicochranes to prevent fusion of the dilithium matrix, unless the spatial compression index is greater than five point six two percent, or the ship is within two parsecs of a class C gravimetric field distortion." Technobabble aside, there's no preference here for long or short parsecs, either will work.

 

[Timo]

The Admiral evacuates all Starfleet units and personnel within a hundred parsecs of the Enterprise, as a safety precaution.

Given how densely populated the Trek galaxy is, this would in many cases entail Starfleet personnel suddenly packing their gear and waving goodbye to a somewhat surprised and potentially quite doomed local population...!

Timo Saloniemi

 

[Mytran]

I just did the maths for that evacuation - a sphere of 100 parsecs radius around the Enterprise would yield a volume of 4,190,000 cubic parsecs!

Kinda puts Spock's "thousand cubic parsecs" in Arena to shame.

All those poor citizens that Starfleet abandoned...

 

[JirinPanthosa]

I think you're overthinking the Trek writers lack of inclination to reach for a calculator.