[Runequest] Fact check

Peter Maranci pmaranci at gmail.com
Wed Mar 27 08:53:40 EST 2013

I should also mention that he's from a low-tech culture and has absolutely
no experience with parachutes - nor does he know anyone who DOES know
parachutes. Somehow, I can't help but suspect that it's hard to "wing it"
with a parachute! :D

On Tue, Mar 26, 2013 at 5:50 PM, <strobus at sympatico.ca> wrote:

>  Interesting stuff.
> Question though - if the surface you jump from is moving at the same
> rotational speed as the ground, would your landing spot still slide out
> from under you, relatively speaking? The building you jump from would lend
> you some lateral momentum, no? But perhaps the top of the building, being
> closer to the axis, is moving slower than the bottom of the building. But
> then the air would also be moving, carrying it with you...
> This stuff makes my head spin :-)
> Makes me wonder how air currents and convection work in the ringworld,
> though.
> Cheers!
> Chris
> ------------------------------
> Date: Tue, 26 Mar 2013 14:32:08 -0700
> From: ashersensei at gmail.com
> To: runequest at rpgreview.net
> Subject: Re: [Runequest] Fact check
> Hi, All,
>    One thing to remember about a ringworld or spinning space station or
> other such structure that gets "gravity" by rotation.  When you drop an
> object inside the environment -- ring, station, what have you -- the object
> does not continuously accelerate.  Ringworld's "gravity" is just about the
> same as Earth's, in that we would be the same weight on Ringworld as we
> would be on Earth.  But that is where the similarity ends.
>    Let's say I paint a big X on the sidewalk, go up the elevator, and then
> jump off a tall building in order to land on the X.
>    On Earth, if I jump off a tall building, I would accelerate
> continuously until either hitting the ground or hitting terminal velocity
> (due to air resistance).  After one second, I would be falling at about 32
> feet/second, or 9.8 meters/second.  After 2 seconds, double my speed.
>  After 3 seconds, triple my speed.  Etc.  The sidewalk below me would
> approach faster and faster.  Barring strong wind, I can reasonably hope to
> land on or near the X I painted.
>    On the Ringworld, if I jump off a tall building, I fall at about 32
> feet/second or 9.8 meters/second -- and that's it.  There is no further
> acceleration due to gravity.  So I watch the sidewalk below approach at a
> more leisurely pace.
>    But there's more.  During my fall, I would observe the X slide out from
> under me.  It would slide to spinward.  Very much like the case of long
> ranged artillery, where the artillery crew have to compensate for the Earth
> rotating underneath an artillery shell in its flight.
>    For any normal jump -- out of trees onto foes, etc. -- on Ringworld,
> the drift would be too small to notice.  But from 500 miles or 800 km up,
> it would matter.  I would have to relearn how to do the math to figure out
> how much the rotational velocity difference would be between the Ringworld
> floor and the Ringworld rim to say how much it would matter.  Let's assume
> that the troll has a strong enough parachute.  On the way down, the troll
> would find that his landing zone is sliding away from him to spinward --
> maybe by 60 mph.  Makes hitting a tree a whole lot more painful, too.
>    Sincerely,
> Asher
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Peter Maranci - pmaranci at gmail.com
Pete's RuneQuest & Roleplaying! http://www.runequest.org/rq.htm
The Diary of A Simple Man: http://bobquasit.livejournal.com/
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