[Runequest] Fact check

Phil Hibbs snarks at gmail.com
Fri Apr 5 21:44:48 EST 2013


Asher:
>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.

You aren't accelerating... but the floor is accelerating towards you. You
continue on a straight line at a tangent to your former rotation, while the
floor below you follows a curved path, approximating an acceleration
towards you of 9.8m/s. So the floor squashes you flat by hitting you,
rather than you hitting it. Small technicality, and no consolation to your
relatives.

Phil.
-- 
Don't you just hate self-referential sigs?


On 26 March 2013 21:32, Asher Royce Yaffee <ashersensei at gmail.com> wrote:

> 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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