I was recently watching a show where the characters talked about something having zero inertia. It was a brief line, but covered something pretty serious. Zero inertia, in a universe where virtually everything is in motion, is a big deal. Which brings us to the old RPG favorite – the immovable rod.
I don’t know why exactly there hasn’t been a published immovable rod for Starfinder, but I can guess. On a planet how an immovable rod functions is fairly simple so long as you make the ‘immovable’ part relative to how the PCs are experiencing gravity and place. Put a rod behind a door to keep it shut overnight and it will still be there in the morning.
Starfinder inherently brings in the issues of interstellar physics, bodies in motion, and inertia into the mix. If you are in a spaceship traveling even a short distance, and set an immovable rod somewhere to keep an object in place, does that rod remain immovable in relation to the ship? Or, does it rip through the hull as it’s fixed point in space immediately comes into conflict with the incredible speed the ship is moving, the solar system is moving, and even the galaxy is moving around it. A fixed point in space is a dangerous thing.
Now the PF1 immovable rod does a few things to lessen this. First, it’s not truly immovable, as a DC 30 Strength check can drag it around. Tough for a single creature to do, but in terms of gravity and astral bodies, that’s nothing (it’d be a great way to slow down a landing space ship though!) Second, it’s just a rod made out of metal, so in game terms it has a hardness of 10 and about 5 hit points, with a break DC of 24. It’s tough, but not so tough that it could withstand the kinds of forces working on it if it suddenly became a truly fixed point in space. Doing a direct conversion, the immovable rod either has to continue to be ‘immovable’ in a relative sense to it’s user’s perception, or it instantaneously explodes with incredible force as the speed of the universe around it brings the fixed point in space past it’s breaking point the very moment of it’s activation. You would be able to find where such rods had been activated by the blast craters they created.
Larger picture, if relative ‘immovable’ rods existed, they would quickly form the anchor points for stations, tethers for space elevators, and so on, becoming the linchpins in massive megastructures as even their relative inertia makes them invaluable to construction in a sci-fi setting. You could even conceivable catch stars or other interstellar bodies with a large enough net of such rods.
Now let’s say some culture gave birth to an inspired wizard that set out to make a fixed point in space. An indestructible, immovable object – the true immovable rod. This hypothetical wizard researches, consults genies and demons, summons materials from other plans, all to create a thing they can imagine but which flies in defiance to the natural laws by which their universe operates. Finally, on a dark and stormy night with lightning in the sky, they create their master work. A gleaming rod, indestructible and infused with powerful magic the likes of which have never been seen before. With a gesture and a word they active the rod. Before they can even comprehend what is happening the planet they are on impacts into the rod with incredible force, and because it is indestructible, the rod rips through the entire world, shattering it. This effect continues as the solar system, and even galaxy that contained the planet, run into the indestructible rod. Soon the rod has enough detritus around it that it begins to accrete its own mass, which continues to build at an exponential rate as more and more things run into it. Before long it is building enough mass to gain a gravitational field, with no end in sight. The true immovable rod is a cataclysm on a universal scale.
All of which is to say, be very careful about adding an immovable rod to your game.
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