The Quick Questions About World Building Thread

Goats can eat stuff that sheep can't, mainly - they're also a bit less susceptible to parasites like intestinal worms.

Would a texas-sized asteroid impact on earth cause an Earth-Shattering Kaboom? Or at least destabilize the planet enough that tidal forces from the moon would finish the job? if such an event did occur, would the moon's gravity keep the Asteroid Thicket reasonably contained? (rocks close enough for a few days travel time with 20 Minutes into the Future rockets?)

This is for a rather soft After the End story were humanity has expanded into near-earth-obit space in the 2040's. Near-Earth Object mining is a massive industry, with rival corporations trying to find and exploit rocks. But, when a truly enormous rock came hurtling for earth, no one was able to stop it.

The story revolves around what astronauts, miners, bandits etc who survived. Think But What About the Astronauts? with a dash of Armageddon meets Firefly

edited 14th Aug '12 12:37:40 PM by Borkless

Borderline "no". Theia or whatever it is called was bigger than that.

Hmm... it at least close-ish?

This story is set in a verse with roughly the scientific accuracy of Armageddon (which is to say, juuuust enough for Rule of Cool to take over)

edited 14th Aug '12 1:10:05 PM by Borkless

http://qntm.org/destroy #9 covers this possibility.

thanks for the link!

Eeexcellent site!

I have a world with multiple large continents, each with a distinct cultural theme and climate. These continents are all separated by great geographic distances, but are nonetheless connected by "wormholes" in the spacetime continuum which function as portals; merchants and adventurers use these wormholes to travel between continents. Would wormholes as imagined by physicists allow that kind of travel on one planet, or do I have to resort to magic?

Magic, surely. As far as I'm aware, there is no flavour of scientifically-sound wormhole which could in any useful way be tied to the rotating surface of an orbiting planet. There are other problems, but that one is the most clear-cut.

So, what would happen if someone with the power to control gravity turned it off around a single person?

I'm guessing they'd go flying off into the air and burst into flames from the friction of going gods only knows how fast up into the sky.

The centripetal acceleration due to the rotation of the planet is given by

a_cp|rot = v^2 / r ~ ((2 pi R)/(1 day))^2 / R = 4 pi^2 R / (1 day)^2 ~ 0.03 m/s^2 ~ 0.3% g

The centripetal acceleration due to the orbit of the planet, similarly, is given by

a_cp|orbit ~ 4 pi^2 (1 AU) / (1 year)^2 ~ 0.007 m/s^2 ~ 0.07% g

So, I'd say the victim would be suddenly weightless and veeery slowly begin to drift upwards. If the intention is to cause harm, I'd definitely recommend increasing gravity to crush the victim under their own weight instead, if that's an option.

Isn't the solar system, galaxy, etc moving also?

I had a physical science class where we discussed how quickly the earth/solar system/etc were moving. Made me a bit curious.

They are, and one could do the same calculation for the sun about the galactic centre, since that's a circular orbit. Off the top of my head, the numbers are on the order of 10^5 light-years and 10^8 years, which would yield 10^-10 m/s^2 or thereabouts. After that, it gets trickier, because the orbits aren't necessarily virialized (meaning they haven't had time to reach the same sort of equilibrium that describes the previous ones) and the expansion of space itself has to be taken into account when describing relative motion.

I don't think any of this is really necessary, though. We're talking about how the victim would move relative to Earth, in the absence of gravity. We know that the dominant sources of gravity are Earth, for the victim, and the Sun, for Earth. That's why we describe their location and motion in those terms, rather than in others. Anything else can be treated as a correction, and so need not be considered as long as we're only estimating and not actually modelling.

And if we did want to start applying higher-order corrections, I'm pretty sure the next biggest contribution comes from a rather more local source than the rest of the galaxy/cluster/supercluster/universe - there's the Moon, and we know that that one does have measurable effects here, namely tidal ones, while none of the others do.

The equator rotates at 1670 km/h. So if he is standing at the equator he would move in straight line at 1670km/h instead of rotating around earth at 1670 km/h(relative to earth).

So at first it would look like hes floating upwards really slowly.

edited 8th Oct '12 12:19:21 PM by m8e

So you DO start to move up when there's no gravity. Who would have thought hollywood was right on that one?

Yeah, sort of, but it'd be very slow-going (and thus not very cinematically impressive) at first. In practice, it would also be completely overshadowed by aerostatic and aerodynamic effects, I suspect - if one were weightless and the air around one were not, one would start to float upward for the same reason that helium balloons do, of course. And acceleration due to wind drag is bound to be orders of magnitude bigger than what I derived above.

If people from our world met with European Fantasyish type cultures fairly often and stayed from dome time several centuries ago, how long would it take for our world's influences to only be party noticable? If that makes sense.

It only makes halfway sense to me, to be honest, but couldn't you look at the impact contact with Europeans had on native cultures in other parts of the world during the Age of Exploration, to gain a sense of (time)scale here?

Above: Duh, forgot 'bout them, good idea, thanks.

What is a "natural choice" for a western-derived civilization in my world to count as year 0 according to their calendar? I've been considering making it the year the Valentian Empire, an Empire whose influence on the history of my world is similar of that to the Roman Empire, fell, but I'm not sure whether that would be a natural choice for my world's people. Does anyone have any ideas?

Any "After the Fall" kind of epoch gives the whole thing a dystopian flair, IMO. If that's what you want, your idea should work very well. If not, I'd go for something more upbeat. Hard to make specific suggestions without you giving us an outline of the backstory of the setting, but perhaps something like "After the Founding" of The City or The Realm (as used by the Romans), or "After the Crowning" of a Charlemagne-type unifying figure, or of course after a date of utmost religious significance, if they are afflicted with religion - but that's so obvious that there's probably a reason you're not using it, I'm thinking.

How long does it take for multiple major lacerations to heal to the point that moderate strain will no longer be likely to re-open the wounds? I mean lacerations affecting skin and muscle tissue, for the most part, no complicating factors like damage to essential ligaments or bone or internal organs.

For example, if someone got attacked with a machete, and suffered serious wounds to arms and legs but was lucky enough not to bleed to death, for whatever reason, how much bed-rest does the victim need before things like walking and lifting no longer interfere with further healing?

I'm thinking more than a week but less than a month, based on what I can remember of my own experiences with minor lacerations and a broken arm, but those memories are a bit hazy by now, and I'm not altogether sure that the multiplicity of the wounds in this scenario might not call for a longer recuperation time.

Thanks a lot, you're right, after the fall seems to indicate a much more dystopian world than what I had in mind. Also, you pretty much read my mind on the religion thing, I thought using it would just be uncreative of me. And thanks for your advice on using the date of the ascension of a Charlemagne-type figure, I have a character just like that forming in the back of my mind somewhere.

What sort of effect does an electromagnetic wave (thats the kind of weapon that turns off power and such for years, right? Did Not Do The Research) ten years later?

I do believe the weapon is called an electromagnetic pulse, or EMP for short. If that's wrong, then Hollywood has been lying to me for a long time now.

As far as I know, the pulse itself has no permanent effects worth mentioning. I mean, there may well be subtle changes in materials with the right kind of electromagnetic properties, but those be of the sort constituting a measurable signature of the pulse, if one has the right gear, not of the sort constituting any kind of problem for anyone or anything.

What the pulse does is permanently fry unshielded electronic within a certain radius (and electrical ones, within a much smaller radius) by overloading them. The long-term effect simply consists in that those components no longer work, and won't work again until they are replaced. Does that make sense?