Are there lower and upper bounds for the size of creatures able to construct spaceships? It’s hard for me to imagine creatures the size of ants being able to do so, but perhaps on a planet with lower gravity a smaller spaceship would suffice. How about a creature the size of a blue whale, would its mass and size make it prohibitively more difficult? Presumably, a lower gravity planet would allow more massive creatures and thus make it easier.
In my opinion the only size limits would come from your definitions of “creature” and “spaceship”. In nature we have tiny single-celled organisms that construct large colonies. I could imagine a bacterial colony or the like covering the surface of an entire satellite (and maybe boring out and occupying some of the interior too), which is then thrown out of orbit and sent off to collide with another planet. It is possible that the biosphere could alter the orbit of their domicile by shifting weight. Is that a spaceship? Was it constructed by creatures, and if so, by many small creatures, or one large one?
~Max
If you assume that the aliens in question have a somewhat similar biology to us, then the lower limit comes from the brain. Intelligence is basically limited by the number of neurons, and (again, assuming an Earth-like biology, which may or may not be a valid assumption) you can only make neurons so small.
Birds, needing to minimize weight in order to fly, have a much higher neuron density than humans. The obvious conclusion from this is that humans are nowhere near the lower size limit. But you are probably talking about something the size of a large bird for the lower limit.
For something the size of a blue whale, you’d definitely need a planet with a significantly lower gravity. The massive Saturn V rocket had a payload of 120 tons and that payload includes the entire habitable part of the spacecraft, including life support systems, food and water, power, computers, etc. The blue whale weighs about 200 tons which is almost double the payload capacity of the Saturn V and that’s before you’ve even started building a spaceship around Mr. Whale.
Great point. I was thinking about strength, dexterity, and such.
One important factor in the development of technology is fire. On Earth, you can’t really build a very tiny furnace on Earth for ants to be able to smelt and forge metals; fire just doesn’t get sustainably hot at that scale. Ant-like creatures could perhaps work around that in various ways - either somehow collaboratively managing to build and remote-operate furnaces that are big and hot enough, or by developing technology based on organic composites, or something, but humans are a better size, at least in the conditions here on Earth, to be able to just get on and perform basic metalwork with their hands.
That’ll be different on planets where the gravity, and the composition of the atmosphere is different (for example where the general role of oxygen on Earth is performed by chlorine or something.
Some ants can carry up 10–50 times their weight . If that doesn’t sound very impressive to you, consider that a 2-milligram ant carrying 10 times its own weight is about the equivalent of a 180-pound human carrying a full-grown cow.
Humans can build machines capable of enabling a single operator to transport about 30 cows at once.
Yep. And hey, cool new avatar.
But it’s a fair point. Certain things are easier at the small scale; other things are harder
If an advanced alien civilisation has sufficiently advanced technology, they would probably make their space travellers to order; this suggests they would tend to make the travellers as small as possible, so that they require less energy, fuel and propellant to accelerate to interstellar cruising speed. Once they arrive at a suitable destination, perhaps they could construct larger, stronger bodies if they require them.
Basically, the answer to ‘how big could a space traveller be’ is ‘as big as necessary’.
[quote=“eburacum45, post:10, topic:989542”]
Basically, the answer to ‘how big could a space traveller be’ is ‘as big as necessary’.
[/quote] Fair point, but could a species the size of ants create a spaceship?
I’m not suggesting that the ants would create the spaceship; in the spacecraft construction facilities there could be a wide range of workers, from the size of an ant to the size of a blue whale.
But mostly the travellers could be ants - or maybe slightly larger travellers, about as big as a crow (very clever and dextrous creatures, after all). The smaller the traveller, the less fuel and propellant required. Indeed I suspect that most travellers would be electronic in nature, and have no specific size at all.
Creatures the size of ants could network — think of them as the equivalent of neurons that collectively constitute a brain, although leave room for a wide variety of ways to accomplish “thought” (i.e., it would not have to exactly mimic how our brains function).
I suspect they’d function well enough in tool and resource utilization to be able to construct space-going vessels.
But if you miscalculate the scale, an entire battle fleet could be accidentally swallowed by a small dog.
As long as they have a poop-resistant hull they could re-emerge to do battle in just a couple of days.
Lovin’ this. It is such an elegant thought, and it leads to another question: why send travelers at all, and not just information. You know that old conundrum: if I put my consciousness into a computer, am I now the computer, or does the computer just think it’s me? Assuming a race that doesn’t see the big deal about that, an entire consciousness could be recorded and that data could be sent to wherever in a device the size and shape of a VW Westfalia. Once at the destination, a suitable body could be generated and the consciousness dumped into or linked to it for easier interaction with the locals (I guess like Avatar). And if you’re advanced enough to not need your own body to link to and lab to do it in, you could just transmit the consciousness directly to an individual organism. Sending a craft with a mass on an interstellar trip can be tricky. Potentially it would be less so if there was no mass to consider.
That is an entirely different question, and we have explored it on this board many times. Maybe we could make some super-ChatGPT-type entity that replicates human mentality so accurately that we don’t need to send people. Indeed, I’m fairly sure that if we ever meet intelligent aliens, they will be something of that type.
I’m not entirely sure that such an entity would be truly conscious in the same way that Humans are - could the entire universe be colonised by some kind of super-chatbot? What would that look like?
It also begs the question if your civilization can upload their consciousness into a computer, why “go” anywhere when you could just create whatever virtual universe you want to live in?
Unless you can create FTL travel like Star Trek or Star Wars where you can reach other stars within reasonable timeframes, the concept of an interstellar civilization seems highly impractical to me.
Absolutely. The creation of a virtual environment is appealing, and many or most advanced civilisations would probably go down that route. This may be the ultimate solution to the Fermi Paradox; all civilisations stay at home, and fail to travel to other systems.
They may also miniaturise their computing systems so much that we can’t see them at a distance, although I would expect at least a few such civilisations to expand their computing systems into very large processing substrates which would be visible (as Freeman Dyson suggested). When you are creating a virtual universe, the bigger the better.
However any stay-at-home civilisation, especially ones with large and valuable processing substrates, might be sitting ducks for the few expansive and aggressive civilisations which are willing to travel between the stars. If you are going to live a life of luxury in your home system you must be prepared to defend yourself.
And quite often the best form of defence is attack; after fighting off a few invaders, an ancient and advanced civilisation might decide that a proactive take-over of the galaxy is in their best interest after all.
A virtual civilization still needs (insofar as we know) a physical substrate to run on. And for an elaborate enough virtual universe inhabited by a large enough supply of virtual denizons, that facility will be large. Or at least will consume a lot of power and the power source will be large.
Unlike a physical world, probably the largest obstacle to an ever-increasing population in the virtual world is that power supply infrastructure.
Which suggests that if virtual civs exist, the way to find them is by finding power supplies.