This post consists basically of spoilers, so you should stop reading now if you don't want to be spoiled :)

In most Known Space stories we are told that you can't use hyperdrive inside gravity wells. Ships that do so just disappear never to be seen again.

In Ringworld's Children, Tunesmith broke this "law". He dropped into hyperspace inside the Ringworld's sun well and survived. He explains to Louis that there's a whole ecology that grew within dark matter, and ships are eaten by predators from this ecology.

In The Borderland of Sol Bey does some wild speculations about the possibility of "hyperspace monsters" eating ships. Like me, Carlos Wu doesn't like this explanation.

Later when the protagonists went near a large mass on the borderland of Sol, their hyperdrive actually disappeared (without any exit hole or anything) and so they simply dropped out of hyperspace.

Carlos explains that using what he claims to be a well-established model of what happens when ships hit such a singularity. According to that model, a low gravity gradient (which is supposedly something you find on things like stars and planets) would disperse the ship's atoms across its path; but an extremely high gravity gradient (like that from the black hole used by Julian Forward) could just snatch the hyperdrive out of the ship like that.

However, this flies in direct contradiction of the "hyperspace monsters" theory. On top of that, hyperwave communication is known to not work within gravitational singularities. This doesn't fit with the "hyperspace monsters", unless they are also "eating" the waves near the source.

So, are there "hyperspace monsters" or not? Was Tunesmith lying?

  • 7
    Congrats on getting us to 1500 questions! This is the 1500th. Commented Nov 8, 2011 at 14:16
  • There is a webpage discussing fictional hyperspace-theriories. Take a look at this and see if you get any nearer: Hyperspace Theory & Practice freewebs.com/knownspace/articles.htm
    – WizardOz
    Commented Nov 9, 2011 at 19:15
  • 1
    As you say, the two stories are in direct conflict on this. There isn't a consistent explanation, your question has no answer. Commented Dec 24, 2011 at 0:37
  • While it doesn't quite answer the question, Sam Hughes's story qntm.org/frontier and qntm.org/kinetic gives a possible explanation for why you can't hyperjump from a gravity well: the hyperjump destination must be a place with the exact same gravitational potential, and if you jump in a direction that doesn't intersect such a position, nobody knows what would happen. Asimov's robot stories have a different explanation: I believe they say the gravitational effects make it almost impossible to navigate a hyperjump precisely if you're near a star.
    – b_jonas
    Commented Dec 23, 2012 at 10:48

5 Answers 5


Having re-read the Borderland of Sol recently, I didn't get the impression that the 'hyperspace monsters' was meant to be an explanation of the generally observed effect of ships disappearing in gravity wells. It was just one possible explanation of the current disappearances which results from the brainstorming between Wu, Shaeffer and Austfaller. As the story pans out, it was an incorrect theory.

As you point out the story goes on to detail that an extreme gravitational gradient will cause effects such as the hyperdrive alone being 'removed' from the ship, precipitating the ship to return to normal space.

Of course this whole issue of hyperdrive and hyperwave not working in a gravity well is a deliberate construction of Niven to hobble the technologies so they couldn't be used as a way of solving all problems - ruining his plots and known space in general. He needed a conveniently fast way of travelling and communicating between systems, but didn't want practically instantaneous travel around a planet or system. He cleverly makes hyperdrive not too fast, except when he needed to break that and used the 'generation-2' hyperdrive - which he hobbled by making it unfeasibly large and expensive to use routinely.

Myself, I like to consider Niven's later work non-canonical as there are several points where he breaks the previously fantastic internal consistency of Known Space. This is of course a personal choice.


My money is on this question being answered in the final Fleet of Worlds novel, Fate of Worlds.

As others have noted, the current Known Space books are contradictory on this; and it may be that Niven originally came up with the explanations simply as a means of limiting the FTL technology. Given these points, the best we can currently say is that there is no canonical explanation.

But of course Known Space is still under development. In particular, Fate of Worlds is a sequel to Ringworld's Children. Given that both Children and the other Fleet of Worlds novels deal with the hyperdrive question, it's not unreasonable to speculate that the question might be addressed in Fate. Ed Lerner noted on his blog that hyperdrive technology is important to the plot:

The Long Shot terrifies Puppeteers. Its Type II hyperdrive is one of a kind, and so considered less trustworthy (read: scarier) than normal hyperdrive. As it happens, you'll learn much more about Long Shot in the upcoming Fate of Worlds.

Is this definitive? Of course not; I am speculating, and when Fate comes out we'll know for sure. But the Long Shot item is surely interesting.

  • 1
    Fate of Worlds was pretty good, but I did not quite see an answer to this question in it. I need to re-read Ringworlds Children to see what Tunesmith did again now.
    – geoffc
    Commented Sep 19, 2012 at 1:36
  • 1
    Now that it's been six years and the whole series is over, do we have an answer like you speculated? Commented Nov 30, 2018 at 14:24

I could be wrong with this but this is my interpretation: I dont think the pak where lying about "monsters" maybe there is something that lives and eats stuff in gravity wells why not? maybe gravity wells act like ocean tides on a planet to help with life?

Anyways with that the inconsistency where tunesmith takes the ring into hyperspace it makes it seem like theyre lying, but if you remember properly
tunesmith took apart a hysperspace mk II drive that does way faster speeds. So maybe when you use regular hyperspace in a gravity well its like trying to outswim a shark with flippers or a row boat, then using the upgrade its like getting into a cigar boat!


According to Ringworld's Children, it really is hyperspace monsters.


There are indications that wavicles CAN actually travel faster than the theoretical speedlimit of light (the scientific observational basis for this - ironically - being when wavicles fall into a gravity well).

However, this is lightyears (pardon my french) away from turning this into the intergalactic equivalent of a V12. If the human race were ever to develop drives that even just approximate SOL, shifting into first gear would:

A) have the ship's crew experience what it feels like for a bug to hit the windshield of an F16 - albeit against the rear of the ship (unless Scotty adds a reverse, in which case of course everyone would be a pancake the size of an AU on the viewscreen).

B) cause a sudden weight gain that no amount of Jane Fonda workout videos is gonna solve (did someone say pigs in space?)

C) James T's "second star to the left and straight on 'till morning"...well, even if dawn was only an hour away on the ship's clock, a gazillion years would have passed outside, so by the time you get to your destination system, its sun would very likely have gone nova and even Reg Barclay would have given up on finding new and improved ways of trying to stutter long-distance with you.

But seriously, bottom line: you would have to invent a math that can do negative square roots before you can theorize on this. The reason being one of Einstein's relativity laws on mass (m) increase related to velocity (v) relative to SOL (c):

m' = m / sqrt( 1 - (v2/c2))

where you run into problems once your velocity becomes greater than SOL.

All you can say with absolute scientific certainty is that it wouldn't be a pretty sight. Well actually, it wouldn't be a sight at all, because once wavicles go faster than SOL you can't see them anymore, and...I'll just stop ranting now.

  • 2
    How do these out-of-universe (i.e. real world) conclusions about FTL travel relate to in-universe (i.e. fictional world) things like hyperspace monsters? FTL travel already works in Known Space without any of the issues you described. (And btw, we already have math that can do negative square roots.) Commented Dec 23, 2011 at 7:47
  • 1
    Hmm..my mistake, I thought this was the science FICTION exchange. Commented Dec 23, 2011 at 9:03
  • 2
    It is. I'm just trying to understand how your answer relates to my question. Maybe there's something I'm missing. Commented Dec 23, 2011 at 9:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.