Designing a planet denser than earth

[mr friendly guy]

Just because they were designed for a high g world/one where significantly higher than normal human strength was deemed desirable doesn't mean they actually wound up there. While it's pretty cliche their colony ship having an accident/human error/malfunction etc. en route and having to crashland is pretty cliche it would go a ways to why the lost so much if not all of their tech base.
Plus there's always the Manpower slave transport riot approach-they were designed for heavy labour/pitfighting/whatever, managed to hijack the ship but crashed it due to having no real clue how it worked.

My current idea is that the indigenous species lived on one continent in this higher G world. Human settlers set up shop in another continent. But then eventually the planet becomes utilised as a prison planet by a third party who is fighting the humans in the war, who for the most part leave the indigenous species alone. The planet is chosen because its isolated from most the main theatre of war. So for the most part, the warring sides on this world are left to fight, with limited support from their homeworlds. This will eventually lead to lost of technology as they haven't had time to set up infrastructure to support the technology, while most of the colonists and prisoners weren't exactly cutting edge researchers, although they would be competent in maintaining said technology.

[madd0ct0r]

So for the most part, the warring sides on this world are left to fight, with limited support from their homeworlds. This will eventually lead to lost of technology as they haven't had time to set up infrastructure to support the technology, while most of the colonists and prisoners weren't exactly cutting edge researchers, although they would be competent in maintaining said technology.

Nothing like a nice war to drive technological innovation. Look at anything ranging from WWI, WWII, the Crimean ect ect ect.

[Dwelf]

So using displacement = initial velocity (zero as they just start falling) x time +(acceleration x time squared / 2).

If I say the character starts falling from a height of 3 metres, with acceleration of 0.9 metres / second squared, ie 1 G I worked out it takes around 2.58 seconds to hit the ground. At 1 metres / second squared roughly 1.1 Gs it takes around 2.45 seconds. At 1.2 Gs at 1.08 metres/ second squared it takes 2.35 seconds. That extra half a quarter of a second won't make much difference thematically. Have I done my maths right? Its been ages since I had to do such physics calculations.

You appear to have dropped an order of magnitude from your acceleration due to gravity. 1g is 9.81 m/s^2 so it should take around 0.78 seconds to fall 3 metres.

[Darth Wong]

Ok lets think about another aspect. I can come up with some other explanation to justify wire fu scenes even if I just go magic blah blah or psionics blah blah. I can even accept Earth equivalent gravity. In fact even with 1 G there is no one someone will glide that way as say a character virtually flying would do. So I most probably need another explanation anyway.

If you want people to glide and do wire-fu fighting without wires, then you want really low gravity, not high gravity. In very high gravity, everything falls faster, no matter how heavy it is or strong its legs are. Even a mighty and high leap would not result in a lot of "hang time". A video of jumping on a high-g world would look as if it were artificially sped up.

[mr friendly guy]

You appear to have dropped an order of magnitude from your acceleration due to gravity. 1g is 9.81 m/s^2 so it should take around 0.78 seconds to fall 3 metres.

Thanks. After I had gone offline I realised I made the mistake. Doh!

Nothing like a nice war to drive technological innovation. Look at anything ranging from WWI, WWII, the Crimean ect ect ect.

That in itself is a point of contention, and I think it highly depends on a lot of the circumstances. Needless to say in sci fi and fantasy both options of war leading to stagnation or innovation has been used, so I think I am on safe ground to use it either way.

Ok lets think about another aspect. I can come up with some other explanation to justify wire fu scenes even if I just go magic blah blah or psionics blah blah. I can even accept Earth equivalent gravity. In fact even with 1 G there is no one someone will glide that way as say a character virtually flying would do. So I most probably need another explanation anyway.

If you want people to glide and do wire-fu fighting without wires, then you want really low gravity, not high gravity. In very high gravity, everything falls faster, no matter how heavy it is or strong its legs are. Even a mighty and high leap would not result in a lot of "hang time". A video of jumping on a high-g world would look as if it were artificially sped up.

I am beginning to think I will have to settle for Earth like gravity world. The problem is I also envisage these characters doing quite strong feats like breaking rock. No reason I can't still have it, I will just have to use another explanation for why they are so strong rather than the being adapted to higher gravity.

It does occur to me though, the way to do "hang time" as you put it in a high gravity environment, is to allow the characters to move ridiculously fast. So that the "visuals" in the story have been slowed down for the benefit of the audience, the same way language is translated into English for the audience's benefit. So while the audience perceives a reasonably fast battle, "in universe" the battle is over within a much shorter span of time.

[Grandmaster Jogurt]

Why would you have needed the planet to be Earth-sized? If you want higher surface gravity, making an Earthlike planet, only bigger, gets you there just fine. You end up with more surface area to work with but is this really a problem?

[Darth Tedious]

It does occur to me though, the way to do "hang time" as you put it in a high gravity environment, is to allow the characters to move ridiculously fast. So that the "visuals" in the story have been slowed down for the benefit of the audience, the same way language is translated into English for the audience's benefit. So while the audience perceives a reasonably fast battle, "in universe" the battle is over within a much shorter span of time.

But the higher gravity (and consequently thicker atmosphere) will make it harder to move fast.
If you're going to slow down the visuals, you might as have dudes who can move really fast fighting in Earth gravity or less, where they'll get even longer hang time.

[mr friendly guy]

Why would you have needed the planet to be Earth-sized? If you want higher surface gravity, making an Earthlike planet, only bigger, gets you there just fine. You end up with more surface area to work with but is this really a problem?

I did consider this as well. The problem would be that for armies to move to attack others, it would run into logistical problems if the planet was larger. I could simply have the main nations be close by, and simply have "far away areas" as unexplored.

[Simon_Jester]

It does occur to me though, the way to do "hang time" as you put it in a high gravity environment, is to allow the characters to move ridiculously fast. So that the "visuals" in the story have been slowed down for the benefit of the audience, the same way language is translated into English for the audience's benefit. So while the audience perceives a reasonably fast battle, "in universe" the battle is over within a much shorter span of time.

The problem is that you could do this just as well if not better in normal gravity. And trajectories will still be much faster to hit the ground than they would at normal gravity; you can't change that- punch someone sideways with as much speed as if they'd been hit by a car on the freeway, and you still won't make them fly very far before they hit the ground.

I did consider this as well. The problem would be that for armies to move to attack others, it would run into logistical problems if the planet was larger. I could simply have the main nations be close by, and simply have "far away areas" as unexplored.

...?

This doesn't make a lot of sense. First of all, you don't have to make a planet all that much larger before gravity increases significantly- surface gravity scales proportionate to the radius of the planet, assuming constant density.

If this is a premodern society, the logistics limits on distances armies can travel are much, much shorter than the distance around even an Earth-sized planet; no pre-modern country ever sustained large armies on other continents without finding ways to provide the supplies those armies needed from the distant territory they were standing on. You'll have relatively small states fighting each other that are, at most, hundreds of kilometers across, and the size of the planet won't change anything about the way wars are fought.

If this is a modern society, then the problems of logistics become a lot more solvable. Fighting between states separated by a large fraction of the width of the enlarged planet is more likely... but also easier to do.

[mr friendly guy]

This doesn't make a lot of sense. First of all, you don't have to make a planet all that much larger before gravity increases significantly- surface gravity scales proportionate to the radius of the planet, assuming constant density.

If this is a premodern society, the logistics limits on distances armies can travel are much, much shorter than the distance around even an Earth-sized planet; no pre-modern country ever sustained large armies on other continents without finding ways to provide the supplies those armies needed from the distant territory they were standing on. You'll have relatively small states fighting each other that are, at most, hundreds of kilometers across, and the size of the planet won't change anything about the way wars are fought.

If this is a modern society, then the problems of logistics become a lot more solvable. Fighting between states separated by a large fraction of the width of the enlarged planet is more likely... but also easier to do.

I definitely don't want them to be a modern society. I plan to have their magic equivalent bit more advance than the age of sail. Basically most sides use wooden ships, but ironclads are starting to replace the wooden ships. Fuel is powered by a mystical rock sort of analogous to coal, but I haven't defined all the rules of it yet, so I have some leeway. Occasionally remnants of advanced technology and science turn up, but for the most part they don't know how to reproduce them, and maybe only work them crudely.

The reason distance might play a factor is that the more powerful human nations have colonised territories belonging to the indigenous species, the same way European powers expanded during the age of colonialism. For ease of keeping things simple, I have divided the continents literally as separate land masses not connected via any land bridges, or if there were, they would be beneath sea level.

Another reason for doing this, I have decided ship to ship combat will likely determine the fortunes for some of those countries rather than land combat since the non human foe is based a separate continent.

[Darth Wong]

If these guys are actually humans (say, from a distant period in the past when we were spacefarers, before they entered a Dark Age), then wouldn't that be even more reason to avoid writing your story in a high-g environment? Humans in a high-g environment would have all sorts of problems, from a greater tendency to form blood clots in the legs to more back problems, hip problems, etc.

[mr friendly guy]

If these guys are actually humans (say, from a distant period in the past when we were spacefarers, before they entered a Dark Age), then wouldn't that be even more reason to avoid writing your story in a high-g environment? Humans in a high-g environment would have all sorts of problems, from a greater tendency to form blood clots in the legs to more back problems, hip problems, etc.

You are most probably right. I was hung up on the Andromeda "genetic modification of heavy worlders" brainbug. This fact presumably justified some of Hercules like fight scenes with Sorbocles Dylan Hunt lifting a guy over his head smashing him on the ground then effortlessly lift him up again to do in on the other side in rapid succession.

Its back to the "its magic" explanation to justify my wire fu fight scenes.

[Darth Wong]

Yeah, you can run into problems when you start internalizing brainbugs from other sci-fi series. If one was going to "genetically modify" people for a higher-g environment, your primary concern would be addressing the physical health issues, not making them super-warriors.

Alternatively, if one was going to "genetically modify" people to be better melee fighters, you would just do it, and not use "high-g" as your justification. It would not be difficult: just increase the propensity toward fast-twitch muscle fibres and change the attachment points for the muscles. If you just make the bicep attach to the forearm a little bit farther up, you could increase your leverage by 50% or even 100%, thus making the person FAR stronger. The penalty would be reduced flexibility and increased energy consumption (the latter of which is not important in a modern environment of plentiful food supplies). I suppose increased muscle flexure for the same bulk movements would lead to increased waste buildup in the muscles would be an issue too, so there would be potential stamina issues, but maybe that could be addressed somehow.

[Simon_Jester]

I definitely don't want them to be a modern society. I plan to have their magic equivalent bit more advance than the age of sail. Basically most sides use wooden ships, but ironclads are starting to replace the wooden ships.

Incidentally, the bigger the planet, the slower steam propulsion will be to outcompete sail.

A wooden sailing ship can, potentially, travel thirty or forty thousand miles and return to port, making repairs out of resources available wherever they land. Magellan's expedition did exactly that, though they lost most of their ships and men to unknown and poorly understood circumstances along the way. Later sailors did a lot better on survival rates.

An iron ship cannot repair its hull on just any beach, though, and a coal-fired steamship cannot refuel in just any port. For intercontinental runs, it wasn't until the late 19th century that steam could seriously compete with sail, mostly because it took that long for the network of coaling ports around the world to develop. Sail-powered freighters remained in business until some time after World War One, believe it or not.

The reason distance might play a factor is that the more powerful human nations have colonised territories belonging to the indigenous species, the same way European powers expanded during the age of colonialism. For ease of keeping things simple, I have divided the continents literally as separate land masses not connected via any land bridges, or if there were, they would be beneath sea level.

You could always stick the inhabited continents closer together- or have the colonies work willy-nilly. It's not like the British weren't able to subdue India despite it being something like fifteen or twenty thousand miles' sailing to get there.

Another reason for doing this, I have decided ship to ship combat will likely determine the fortunes for some of those countries rather than land combat since the non human foe is based a separate continent.

Make sure you grasp the capabilities and limitations of the era, is all I have to say.

You are most probably right. I was hung up on the Andromeda "genetic modification of heavy worlders" brainbug. This fact presumably justified some of Hercules like fight scenes with Sorbocles Dylan Hunt lifting a guy over his head smashing him on the ground then effortlessly lift him up again to do in on the other side in rapid succession.

Its back to the "its magic" explanation to justify my wire fu fight scenes.

Actually, as Wong pointed out, this works better on a low gravity world (which also gives you cool effects like giant birds). As long as people keep more or less the kind of muscle tone they'd have on Earth, gravity less than Earth gives you men who can jump ten feet into the air, who can pick each other up bodily without too much trouble, and throw each other sideways at a few meters per second... watching them drift towards the ground because the acceleration due to gravity is half what it ought to be.

Heavy-worlders on a heavy world wouldn't have any of this.

Heavy-worlders on a normal world actually might, but that's completely irrelevant to your setting.

[Connor MacLeod]

This leads me to wonder what a.) we're defining as 'heavy gravity' I mean does only 5-10% from Earth standard quality, or what? Or are we talking something extreme like 4-5x?

For that matter what sorts of impact on the human body (short and long term) would we expect from a heavy gravity enviroment? Circulatory and respiratory problems seem to be one example, as well as greater stress on the body (greater weight on the skeleton, etc.) What else would there be? Would there be any actual advantages if you can address the problems?

[Batman]

Depends. People fully adapted to seriously higher gravity would likely be massively stronger than ordinary humans, not to mention considerably more resistant do physical damage-in a 1g environment. They'd also likely be clumsy as hell and have trouble breathing given they'd be used to an atmosphere far denser than ours (presupposing you actually could adapt human life to an environment as extreme as that). On the planet they were 100% adapted to, I don't see them performing any better than ordinary humans.

[Purple]

Speaking of heavy gravity vs light gravity. In the hypothetical situation of a heavy world army invading a normal gravity world, if the gravity difference is large enough (say their home was 3x or more times our gravity) won't they also suffer from effects similar to astronauts in zero G? I mean, sure it won't be as severe and it will take more time. But sticking here for months or years might make it a thing to consider. Sort of irrelevant for the current situation but just felt the need to ask about it.

[Simon_Jester]

It's hard to document, because while we have data on men living in microgravity (i.e. on space stations) for about a year at a time, we don't have data on life in low gravity. Low gravity is impossible to simulate for extended periods of time.

And of course we have less than no data on the biology of high-gravity-adapted humans or humanoids.

The answer might well be "maybe yes, maybe no, maybe severe and stopping them from going home, maybe something they can recover from with a modest regimen of exercise..."

[someone_else]

High gravity worlds also have an interesting side effect. Chemical rockets may not be enough to escape from them.

I mean, if you double the gravity (mass), the orbital velocity for LEO/GEO/Escape should double as well. So to get to orbit you would need what, a saturn V? No way to go to the moon then.

I was also thinking, wouldn't be a good "high gravity world adaptation" genetic engineering trick just making humans shorter instead of stronger?

I mean, the mass goes down mush faster than size, so if we have to adapt someone to say a 2 gee planet (twice Earth gravity) what about by dividing by 1.3 the size, the mass is divided by 2.2, so you get a lifeform that has to withstand the same mechanical/energetic stresses we have now with a lifeform just a 70-ish% of Earth ones.

You still have issues with falling, but there is little you can do about that anyway.

Or am I doing something wrong?

[Guardsman Bass]

Incidentally, the bigger the planet, the slower steam propulsion will be to outcompete sail.

A wooden sailing ship can, potentially, travel thirty or forty thousand miles and return to port, making repairs out of resources available wherever they land. Magellan's expedition did exactly that, though they lost most of their ships and men to unknown and poorly understood circumstances along the way. Later sailors did a lot better on survival rates.

An iron ship cannot repair its hull on just any beach, though, and a coal-fired steamship cannot refuel in just any port. For intercontinental runs, it wasn't until the late 19th century that steam could seriously compete with sail, mostly because it took that long for the network of coaling ports around the world to develop. Sail-powered freighters remained in business until some time after World War One, believe it or not.

He could still have hybrid steam-sail ships out-competing the pure sail ships, though. There were a fair number of those in the 19th century (one of the earliest was the SS Savannah, and many later Clipper Ships converted to "steam clipper" hybrids), and while they would be more expensive and complex than pure-sailing ships, they also offer some advantages. Being able to turn on the steam engine when you get stuck in an area of little to no wind might be very useful, particularly if you're on a planet larger than Earth, and in the middle of a large ocean.

In fact, I wonder if ocean-going, pure coal-powered steamships would ever become competitive in a world where the potential ocean-traveling distances might be much greater than on Earth. Islands that could potentially serve as coal re-fueling points might be too spread out, and so you'd end up with sailing and hybrid ships over long distances until somebody figures out how to use petroleum for fueling. And if the world in question doesn't have lots of accessible supplies of petroleum . . .

[Simon_Jester]

A fair point, Guardsman- it would depend on the environment.

Wood-fired steamboats replaced sail for river traffic almost immediately, because it's almost priceless to have a boat that can sail upstream against the current reliably, and even tow barges; on the Ohio and Mississippi rivers in the US, before steam power, the custom was to build the barges in Ohio, send them downriver to New Orleans to drop off the goods for export into the world ocean, and then just break up the damn barges and use them for timber, because there was no way to bring them back upstream. Consider the labor savings of not having to do that... it'll happen in any world, no matter what.

Wood and coal-fired steamships will still dominate over sailing for short distances, too. Ironclad coastal defense monitors will evolve on schedule. What you will see is, yes, steam clippers and screw liners will dominate on intercontinental routes for longer than historical.

[sirocco]

Just a little remark: in this setting, shouldn't the people remember that some time ago their ancestor had cars, railroads, planes, rockets, etc? Even though they no longer have the scientifical knowledge to build them, at least they know it is possible to do so. It's somewhat a luxury that we didn't have during the age of sails.

I expect to see each country/nation/region trying to come up with its own design, but just slightly similar to what we have here on Earth.

Finally, I think that railroads would be a good way to travel on land. At a start maybe not too fast depending on the materials available (higher gravity may not be kind on your rails)

[Johonebesus]

You might consider playing with the atmosphere's density, which depends more on the amount of gas present than the planet's mass. Venus is slightly smaller than Earth yet has a vastly denser atmosphere. If the air were a bit thicker than ours, wouldn't that add a bit more buoyancy, making flight easier? Too great a difference would create problems for human colonists, but a modest difference could allow for bigger flying animals and easier powered flight, and might affect how people move.

[Batman]

'A bit' in the case of Venus meaning not quite two orders of magnitude, with the vast majority of it being CO2. I suspect even leaving alone adapting human beings to that kind of atmosphere (assuming you can get a sufficiently oxygenated atmosphere at those kind of pressures, which I'm not qualified to comment upon) I very much suspect the massively increased air (for want of a better word) resistance would pretty much cancel out the increased buoyancy.

[mr friendly guy]

Just a little remark: in this setting, shouldn't the people remember that some time ago their ancestor had cars, railroads, planes, rockets, etc?

I had planned for them to shroud their history in myth and legend. So when their ancestors used high tech weapons, it was a war of the gods etc.