Need a scientist?

[Rider of scaled wing]

If the zinc is the dominant impurity, yes. But the word "bronze" is very loose; the people who were making it would chuck in a bit of this, bit of that; as long as the basis was copper, it got classed as bronze. Then there are all the modern ones like phosphor bronze, magnesium bronze, which I don't think contain any tin at all.

But you'd want hardwood charcoal for the smelting, not the conifers that are most likely to grow in those conditions. Oh, there are deciduous trees that could survive, but they'd be replaced pretty slowly, probably leading to mobile charcoal burning camps in the summer, and mass transport of prepared charcoal on sledges come first snow. Or you could have them own a coal mine and produce coke as a reducing agent.

A wealth of knowledge in a neat post. This is going to help immensely.

The 'mobile charcoal burning camp' idea seems like it'd be very interesting as far as cultural background. Mined coal would probably be traded for at ports for the most part, and those who did in fact own local coal mines would probably be the more wealthy.

 

[Trammell]

Hi all - new to the boards, but I've got some expertise on green energy, particularly wind and biomass. I'm not a scientist or engineer, but am a minor partner in a greenfield wind development company and have learned a lot of interesting stuff along the way. I also know a number of the leading educators in the renewable field, so if you do need serious technical expertise, I might be able to hook you up.

Great idea for a thread btw.

 

[J Riff]

Yes. Well, here's my planet-sized problem.
A planet is discovered that is falling into its Sun. It has a few short years to go before it becomes too hot to save the lifeforms still living there.
Humans, who have arrived in a gigantic ship, must attempt to increase the velocity of the planet, or the size of its orbit. They have two massive spacecraft to do this with. The panet is perhaps2/3 the size of Earth, or smaller.
How would one latch on to a planet, or manage to drag it into a lager orbit? I had a vague idea about magnetic couplers and a nickle-iron core to the planet, but....

 

[J-WO]

I'm no scientist, but wouldn't the very action of the planet falling into the sun already be killing off the life there, or at least affecting the gravity, weather etc? As I say, I'm no expert, but...

 

[chrispenycate]

Sorry this has taken me so long; It's not the generating of the concepts, but the typing them out.


I assume that the orbit has become ever more elliptical, and the perigee is now close enough to the primary to be developing friction? A steady, slow spiral wouldn't give you a few years to solve the problem, but a few centuries. Much preferable. But now we get long, very cold winters, and short but drastically hot summers.

So, how do your ships' drives work, and how much damage am I allowed to do? Jogging a planet ,even the tiny bits to recircularise an orbit, is going to take immense quantities of energy; but, so does accelerating a couple of million tonnes up to near light speed. I was considering using the magnetic field generator used for compacting interstellar hydrogen for a bussard ram jet, and eddy currents in the planet's core, but even that, which can only hope to provide millimetres per second squared (and the ship will lose almost all of its momentum, and be useless for days). Even that will increase vulcanism and planet quakes; some of my other tricks (like colliding it with extremely accurately aimed comets, which would obviously vaporise in the atmosphere, but their momentum would be conserved. As would their cargo of volatiles; you can expect some serious sea level rise as it condenses out as rain.

If you had my gravitic drive, the mechanism is dead simple; but the difference in mass makes moving a planet with ships a bit equivalent to water skater beetles towing an ocean liner. There's nothing much stopping them, but the process is going to take a while. Probably more than the years before surface conditions become life supporting.

So, we set up manufacturing tens of thousands of huge robot ships. Each one swoops past the planet on a calculated trajectory, close enough for some spectacular tidal effects, and gravity to transfer a fair amount of momentum. Then it redirects itself back out to the gas giant, where orbital stations are preparing more fusion fuel and reaction mass, to accelerate up and swoop again. As far as possible everything automated, with humans trying to clean up the inevitable crises.

OK, one slightly better in effectiveness, if slow. We build a really big fusion jet – big as North America, at least, probably as big as Earth – and find a small gas giant, something like Neptune or Uranus (not a gas dwarf by any means; still many times the mass of our target planet) Now we plunge our motor into the gas planet and light it up, at a throughput of several hundred hydrogen bombs a minute (gotta be tough). The plume of vapour jetted into space shifts the planet's orbit into something more elliptical, until finally its perigee is within the orbit of the potentially habitable planet. Lots of careful manoeuvring (of a mass considerably greater than the universe was supposed to be until the eighteenth century) and it's in just the right place that its gravitational field pulls the planet in the direction you planned, and again as it rounds the sun, and goes skooting off into the cold and dark for fifty years or so, when it becomes available again for more Velicovsky cosmic billiards.

Oh, stupidly massive tides, earthquakes, hurricanes to dwarf anything ever seen in our atmosphere; I get to break things. But probably not the entire environment.

Trouble is, building that jet is going to take a century, (and joggling the big planet's orbit decades, at least). By the time we're ready to act, it's too late. So, how about this? We build the thing in orbit in the solar system, when the first probe sends back information about a potentially habitable planet, and put the fleet in orbit around it.(It'll mass as much as a fair-sized moon) Then we feed it comets, and it accelerates, towing the space stations and terraforming vessels that can remain fully fuelled the whole trip. They can even use solar cells to get energy from the yellow hot fusion engine, and greenhouses can grow food. The idea being, evidently, that they cut loose in the destination system; but when they are a decade or two out, they spot the orbital decay of their potential new home. For cosmic engineering you need large tools, so they allow their tug to be captured by a planet in the system, and start doing their sums…

 

[J Riff]

Ok, I'm going to have to read that a few times! What I forgot to mention, though it may not matter much, is that the planet is a dustball. Totally dry, sand and only sand, howling wind storms and a giant sand whirlpool/vortex dominating one side of the planet. So there is precious little damage that will matter much to the underground dwellers, who live inside solid rock.
The furthest point, the apogee? was where I figured power could be applied, or mass added to the planet, as the gravitational field would be at it's weakest there?
Also, I am going to set off one or two uniquely-designed gigantic bombs below the planet's surface, in order to try and collapse the huge whirlpools that have formed, in an attempt to quell the constant 200 mph winds. Thought maybe that could be timed to coincide with any other effort to shove the planet back away from the sun.
Once this is accomplished, terraforming can start. This is the 1st planet humans have discovered with life on it, so they are ready to pour everything they have into saving it. I have two gigantic ships, far too large to make planetfall, to work with, and they have all the tech there is. )

 

[chrispenycate]

If you're going to terraform it anyway, the "crashing comets" solution is probably best, although the chthonic residents might be a bit surprised when lowlands become seas, and atmospheric pressure triples.

For maximum effect you do your operations (in this case, ramming the planet with a cosmic snowball) as close to perigee as possible, just like slingshot acceleration; when the maximum of energy is kinetic, minimum potential, that's when small changes can cause big results.

If you've detected the problem before arrival (as I imagine you would be looking very carefully at your planned destination on the way in, with robot probes and the like) you could collect your comets as you go through the Oort cloud equivalent (yes, big butterfly net. I don't know if comets are tough enough to withstand my standard drive technique in these circumstances, which is to explode hydrogen bombs next to them until they are pushed into the required orbit. It might come down to building a very large ion drive for each one. Ygad, the calculations are hairy.

A lot of small (≥ hundreds of kilotonne) impacts are safer to use than fewer enormous ones.

I suspect you'll have to wait until the orbit is circularised before trying any atmospheric dynamic calculations; that much water, and generalised volatiles, being applied in one swell foop (actually, in several smaller foops, but over a short period of time) is going to massively modify the weather situation (it might quite easily be them that caused the stable storm in the first place).

So, the natives aren't even worried about the steadily destabilising orbit? Deep down like that, it'll be millennia before the thermal cycling starts to make any difference to them (and I ask how the probes detected life there in the first place. Relative concentrations of atmospheric gasses, like oxygen, that would need a continuous process to replenish?). The comfort factor is for the humans; it's only long-term that it's going to effect the planet's own ecology.

So, I can take a few decades with my solution; the impatient so and sos can live in their ships (or build orbital stations) until then, but no "preparatory" settlements on the planetary surface; impacts several times larger than "dinosaur killers" will cause considerable disruption.

 

[J Riff]

OK. I've decided to start the story with the big blast, six months after the planet is discovered. Time is short, and conditions impossible on the planet's surface, so they go for it, boom.
I started this as a screenplay and it might still work that way, but have to come up with a believable planet-shifting description first.
I had the idea of bringing gigantic icebergs from a nearby planet, so don't know how they could be used, other than to make a lake or two.
I'll post some of the beginning if I can ever get around to actually writing it, and see if it's believable enough to get by. Tx, Chris. )

 

[chrispenycate]

Don't get into lifting things out of a planetary gravity well; far too much energy requirement. Water ice is a common resource in our solar system; not only the comets, but the rings of Saturn, and the surface of several of Jupiter's moons; not over surprising, as hydrogen is the commonest element in the universe, and oxygen is a part of the main stellar fusion chain.

I will even guess that any system which does not have a lot of loose water ice kicking around will not be suitable for human colonisation; too different chemically.

And kinetic energy, properly applied (dropping heavy weights from orbit, for example) can be just as effective as explosions, and quite a bit cheaper…

 

[Hex]

I wonder if anyone could tell me if it would be possible to kill (or, annoy) an octopus (a hugely enlarged one, naturally, for dramatic effect) with a small book.

I know they have a water-out funnel thing which helps them move (I think), but do they have a handy orifice that my hero could stick a book into?

(and if anyone would like information on 20th C history, especially around WWII, and most especially in the USSR, then I'll... um... have a go (its been a while, but I used to know a lot). Also willing to hold forth on human-computer interaction and the various effects of ageing).

 

[Rider of scaled wing]

a world building question, particular to any biologists who have experiance.

Eyes.

Eyes that are built for seeing great distances, like an eagle, and eyes built for excellent night vision, like an owl.

Are the mechanisms that grant each of these kinds of eyes their special attributes mutually exclusive, or can there be a 'perfect eye' that has both great focus at distance, and great night vision?

 

[goldhawk]

...or can there be a 'perfect eye' that has both great focus at distance, and great night vision?

No. Although it may be physically possible, such a thing would not evolved.

Some hawks evolved long-distance vision because they fly high enough so their prey can't see them from the ground. Owls evolved night vision to see at night. What you want is a bird that flies high at night. Such a bird is not likely to evolve. If it was likely, there would be at least one breed of owl that does this.

Owls rely on their hearing more than their vision. And they fly relatively slow, especially when compared to a diving hawk. That's because even with their night vision, they can't see that well and don't want to run into things at high speeds.

So, unless you can come up with a niche where an animal can evolve long-distance, night vision, the answer is no.

 

[Boneman]

So, I've got an ancient city, probably 500,000 inhabitants, with a system of drains where the effluent is eventually used as compost. But there are pretty massive underground caverns. Is a build-up of methane and an ignition a feasible scenario? Essentially, I want it as an explanation for an explosion in a building, (like a backflash) but what sort of damage would it cause? Does it explode, or just burn? And what sort of spark is necessary, or can it happen spontaneously?

Sorry, that's a lot of questions... Be grateful for any help.

 

[goldhawk]

So, I've got an ancient city, probably 500,000 inhabitants, with a system of drains where the effluent is eventually used as compost. But there are pretty massive underground caverns. Is a build-up of methane and an ignition a feasible scenario? Essentially, I want it as an explanation for an explosion in a building, (like a backflash) but what sort of damage would it cause? Does it explode, or just burn? And what sort of spark is necessary, or can it happen spontaneously?

Sorry, that's a lot of questions... Be grateful for any help.

It would explode. Any source of heat would do it. Never heard of one spontaneously igniting. It would explode the building, sending chunks of it into nearby buildings and raining down on passersby. There would be nothing left of the building but its foundation and rubble.

Also, your city could be built on top of a natural gas fissure; cracks in the rock beneath it allow natural gas to seep up. Normally, the gas would disperse in the air but it could build up in a building to explosive levels.

 

[Boneman]

It would explode. Any source of heat would do it. Never heard of one spontaneously igniting. It would explode the building, sending chunks of it into nearby buildings and raining down on passersby. There would be nothing left of the building but its foundation and rubble.

Also, your city could be built on top of a natural gas fissure; cracks in the rock beneath it allow natural gas to seep up. Normally, the gas would disperse in the air but it could build up in a building to explosive levels.

Brilliant! Thanks so much, Goldhawk - it's exactly what I need. Naturally, the woman takes a candle to the sluicing room, electricity not been invented yet!

 

[Sapheron]

Damn you Boneman, stealing my plot! I have quite a similar set up going in one of my WIPs, though mine is natural gas rather than sewage.

 

[seaside]

I have two ocean related questions.

Assuming you're on a planet based on earth (same rotation, size, etc.) will you get waves on both sides of a channel? I have an area of my world with two parallel islands about a mile apart. There's a channel running north and south between them.

Also, can rip currents occur at on the northern and southern sides of an island?

 

[Abernovo]

Hi, seaside. Waves are formed and influenced by combinations of currents, weather systems and terrain, so you would get waves on either side of a sea channel between islands. I used to live on an island with a 2km (1.6 mile) separation from the next island over. There were big waves. The exact form of wave may vary depending on the islands' situation in relation to other land masses, the direction of the current and to their coastlines and surrounding seabed. As to rip tides, I'll have to look at one of my old oceanography tomes. It was one of those subjects I only touched on at university.

I qualified as an agricultural and environmental manager and have worked in wildlife and habitat protection. So, if I can help with environmental questions, I will.

 

[ktabic]

Also, can rip currents occur at on the northern and southern sides of an island?

Rip currents are (generally) caused by the interaction of the a receding current from a shore with physical features, such a a break in a sandbar. Since these can occur anywhere (sandbar and breaks in them) they can happen on either side of an island - they are normally in the opposite(ish) direction to the direction the waves are moving in. North or south doesn't come into it.

 

[goldhawk]

Assuming you're on a planet based on earth (same rotation, size, etc.) will you get waves on both sides of a channel? I have an area of my world with two parallel islands about a mile apart. There's a channel running north and south between them.

You won't get waves coming in on the shores inside the channel. If they are running north or south, you would get waves running up and down the channel but almost none if they are from the east or west. If they come in at an angle they might bounce repeated off the shores and zig-zag down the channel.