Not sure this can be answered, but I recall and the synopsis in Wikipedia mentions the extreme fear of heights that creatures who live in 67 billion Gs have.

It is reasonable that such creatures would fear heights but on the other hand, they are both much smaller than humans and they also live on a "planet" which is almost smooth by our standards; they also are probably much more durable than humans, being made of extremely dense matter.

So is it reasonable to attribute a greater fear of heights to them than our own considerable fear? Would indeed, even taking account the above differences, the effect of gravity and specifically falling (or having things fall on them) be much different than our own gravity which certainly is a big concern whenever we ascend heights not much more than a couple meters, i.e., our own heights?

1 Answer 1


Yes, they fear heights. With good cause. At 67 billion g, even living at a million times human speed things drop very fast:

The first thing they did was to push the large, whole dragon crystal to the edge and let it fall off. The nearly unbreakable, super-hard crystal became invisible and reappeared at the bottom, splintered into a dozen sharp shards.

Things fall so fast that they are imperceptible; even a small fall would be fatal.

There are a couple of episodes of cheela being uncomfortable on a height, but this one is notable. Even one of the bravest, smartest and most adventurous cheela is unable to face a drop of a bit more than her own height:

She then turned the slab sideways and slowly let it come down, where the flat edges jammed against the the narrowing sides of the crack as the pull of Egg sat it firmly in place. Swift-Killer slowly relinquished her hold, and she watched in pleasure as the heavy chunk of crust stayed suspended between the walls of the crevasse, just over her normal eye height. She took another slab, a longer one this time, and soon it too was suspended against the pull of Egg at the same height but further out from the back of the notch. Swift-Killer looked her creation over with care and then flowed back out of the crevasse and shortly returned from the rubble pile with another thick slab of crust, longer than the others. With a great effort she lifted the slab and soon it was in place, resting on top of the other two. Swift-Killer hesitated, then slowly induced herself to glide under the improvised platform to the back of the crevasse. She again forced her body into the narrow crack, and stretching out a narrow pseudopod that snaked up to rest on top of the wedged slabs, she slowly pumped her juices up against the pull of the Egg so that they inflated that portion of her skin on the platform. She halted after she had several eyes transferred to the upper level, then formed some strong manipulators that grasped the top slab tightly. Then, firmly anchored, she finally pushed and pulled the rest of her body up onto the platform.

All during this long procedure, Swift-Killer had been careful to keep all of her dozen eyes carefully concerned with watching the wall, the manipulators, the slabs, anything but the outside environment. Only when she was safely on top of the slab, her manipulators keeping her from flowing off the front or the back, and the firm walls of the crevasse holding her in from the sides, did she finally allow herself to observe the predicament she had put herself into. She looked out of the crevasse at the horizon, then at the pile of rubble in the distance, then at the crust just at the entrance to the crevasse, then just inside the entrance, and then her eyes refused to look any further. Try as she might, she just couldn't seem to make them look down from the platform where she hunched, perched at a height above the crust that would have burst her skin like a ripe pod if she had fallen.

  • It sounds like the author argues that despite the creatures having evolved in such an environment, their fear of heights is another order of phobia than our own and since he was a physicist, i'll buy this. a related question to follow.
    – releseabe
    Sep 29, 2022 at 22:20
  • 2
    +1 We can appreciate this fear in our own real-world experience here on Earth: a bacterium dropped from 8' will float around for a long while; a mouse dropped from 8' will bounce and run away; a human dropped from 8' might walk right away unharmed, might break a limb; a horse dropped from 8' is almost certainly facing a life-threatening injury. The Cheela are dealing with this but with acceleration pushing rapidly into relativistic velocities.
    – Lexible
    Sep 29, 2022 at 22:20
  • @Lexible: I do not recall the book mentioning an advanced understanding of relativity but would that not naturally occur? Experiments that humans performed had to be extremely sensitive (like Michaelson-Morley) but would they not notice in their everyday lives relativistic effects? I am not sure about this, maybe I should ask this in Physics.
    – releseabe
    Sep 29, 2022 at 23:11
  • it would take a fall of 0,003 seconds to reach 0,75c, at a million times speed that would be equivalent to almost an hour of falling. Which is still ludicrously fast.
    – Borgh
    Sep 30, 2022 at 13:24

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