Hard Truth about stellar distances, for sci-fi RPG GMs

Hard Truth about stellar distances, for sci-fi RPG GMs

One of my pet peeves with sci-fi books, movies and particularly RPGs, is the treatment of stellar distances.  I respect a show or movie that treats it properly or at least show it a little respect.  It drives me crazy when a writer or director chooses to totally ignore them.  Case in point, Star Wars, especially the latest Star Wars movie.  JJ Abrams has a real problem with it because he did the same thing in his two Star Trek films.  It drove me up a wall.  Star Trek, up until that point, at least tried to recognize them in some fashion or another.  The whole pseudo-science behind warp was purely out of respect of the size and physics of space.  JJ ruined the Star Trek franchise, as far as I am concerned.

Just to give it perspective, I pulled this from the internet… The light from the sun takes about four hours to get to Pluto — and its pale reflected beams take about three hours and 52 minutes to bounce back to the earth. Pluto’s farthest distance from the sun is 4,567 million miles. From this point it takes a beam of light 16 minutes longer to travel from Pluto to earth.

4 Hours!!!  At the Speed of Light!  So even if we figured out how to travel AT the speed of light, which according to Einstein is near impossible, it would still take us 4 hours to get there.

Now distances between stars are another important point.   Again, the internet…. The nearest stars to Earth are in the Alpha Centauri triple-star system, about 4.37 light-years away. One of these stars, Proxima Centauri, is slightly closer, at 4.24 light-years. Of all the stars closer than 15 light-years, only two are spectral type G, similar to our sun: Alpha Centauri A and Tau Ceti.

We all should know what a light year is.  So it takes about 4 and a quarter years for light to travel from our system to Alpha Centauri. So when you look up in the sky and figure out which star is Alpha Centauri, that light that you see is 4+ years old!

Another case in point from the Force Awakens is when they fire the Starkiller for the first time.  I can only assume they are in a separate system from the one Han and Finn were on – Takodana – given the fact that the super weapons sucks all of the sun of a system.  Assuming that all these locations is on the Rim (as is the Resistance base), the target of the first Starkiller victim was the New Republic capital, which I can only assume is coreward.  Either way, let’s just assume they are all neighbors.  There still would be light years involved and the light from the Starkiller attack would not reach Takodana for years!  They would not observe the attack from a neighboring system WHILE it was happening!  And this assumes the weapon is firing at light speed, which with plasma of a star is a pretty good feat in and over itself.  Damn physics getting in the way of a good dramatic scene.

Interstellar Communication is another thing that drives me nuts.  Case in point, the scene in Star Trek Into Darkness where Kirk called up Scotty while in orbit around the Klingon homeworld.  Scotty, by the way, was on Earth! And they are making a call like it just down the street! Now according to Memory Alpha, the distance between Earth and Kronos is … About 112 light years, 4 days at warp 4.5.   Even if you were calling through Warp, it would takes days!  Just to clarify, assuming they are using standard radios… Radio waves travel very quickly through space. Radio waves are a kind of electromagnetic radiation, and thus they move at the speed of light. The speed of light is a little less than 300,000 km per second.

Again, pesky physics ruining a good plot moment.  JJ Physics strikes again.

Just to get off of JJ a little and move on to another Geek-God – Whedon.  I have a real issue with Firefly and it comes down to physics.  I am not asking for perfect physics but at least a believable understanding of it!  Many don’t realize that (according to the RPG) the universe that Firefly is set in is one system. Five or more stars with 40 or more planets, most of which were terraformed to Earthlike worlds.  This all done so they don’t have to have any kind of hyperspace or jump drive.  Again, stellar distances ignored. let alone gravity physics behind having this many stars in one system.  It just can not happen.  All because he was too lazy to come up with a simple jump drive system.  LAME!  No respect!


In truth, space is big and it can be used for dramatic adventures for an RPG and not in the boring way that games like Traveller use it. Stellar distances can be used by a GM to force the players in isolation.  If they know that their signals are going to take days or weeks to reach anyone that can help, they will be more willing to make decisions on their own and take the risks a GM loves them to take.  It gives the party a sense of self reliance and independence.

Depending on the setting, there may be conventions set up for travel and communication.  Keep those in mind for the various situations where stellar distances matter.  If they are realistic or at least show respect to physics and the size of space, they can be used well in a campaign.  One game setting I have been known to run (Fading Suns) uses instantaneous jump gates between systems, and a rather efficient drive system for in-system travel.  But it still took hours, days and sometimes weeks to travel between locations because of that in-system flight from the jump gate (on the outer rim of every system) and the destination.  You really had to localize the situation for the players.  Planets weren’t just quick stops.  In situations like this, the resources available to the players – allies, enemies, technology, etc – need to be localized and well understood by the players.

In worlds where “hyperspace’ is common, like Star Wars, it is a very fluid and wonky concept.  Even in Star Wars, the concept has been a little fluid.  Originally (based on the original trilogy), hyperspace navigation was dicey at best.  Now, as of Episode 7, Han has gotten good enough to drop out of it just above a planet surface.  So, conventions need to be set by the GM so that this magic box doesn’t get abused (like it was in Episode 7).

It is also important for the GM to mitigate the travel time between systems.  Sometimes you want to use it to expand on the story or do a side adventure.  For example, I tend to overuse the “You pick up a distress signal” trope.  Other times, you may want to skip over it and just use it to build skills, heal up and study spells (if applicable).  Be sure to express the players that time has passed.  If there is time sensitive plot waiting for them on the other end, be sure to keep that in mind.

Respecting stellar distances takes some work.  If you want the players to have a bail-out or cavalry option, they need to be close by and not in the next system.  A space station around a neighboring moon or gas giant, for example.  What I have found is that players take the easy way out far too often and far too early, so keeping that cavalry option as a last option somehow is usually best.  Where is the adventure in doing the minimum and letting someone else handle it?

However, never leave out the possibility of instantaneous travel between systems.  This can be the magic of ancient alien races or extra dimensional beings – the technology that no one in the player’s universe has but can attain after millions of years of evolution and knowledge.  Always remember Clarke’s three laws –

Clarke’s first law: When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.

Clarke’s second law: The only way of discovering the limits of the possible is to venture a little way past them into the impossible.

Clarke’s third law: Any sufficiently advanced technology is indistinguishable from magic.

The third one is key.

I highly recommend that people read the following book if you are going to right a sci-fi game or adventure

The Writer’s Guide to Creating a Science Fiction Universe 


It is very succinct and to the point.  An easy read that is smart and straight forward. Also read this …

Going Interstellar


These two books reformed my view of science fiction in general.

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