Re: Insanely Silly Rationalization Time!

"Andrew Plotkin" <erkyrath@xxxxxxxxxx> wrote in message
news:e72pri$4j5$1@xxxxxxxxxxxxxxxxxxxx
Here, Logan Kearsley <chrono.surfer@xxxxxxxxxxx> wrote:
Alrighty, I'm trying to work out some basic laws of physics for a
sort-of-fantasy / sort-of-science-fiction universe I just came up with.
Among several strange and interesting differences from our universe,
this
one features flat planets with an edge that can be walked off of. I was
figuring on making this work by instituting a preferred direction for
gravity, with the force exerted between two particles being dependent on
the
angle between the line between the particles and the universal vertical,
so
if you're directly above or below something, gravity works you get a
strong
attraction, but if you're directly off to one side, there's no
attraction.

That ought to work out great for giving me large, slowly rotating flat
planets, but for two problems: first, could they hold an atmosphere, or
would there always be too much leakage around the edges?

I think it wouldn't be leakage; it would be a hurricane. You've got
air at (one hopes) 1 atmosphere, but nothing is holding that pressure
in around the edges. It would go whoosh and be gone.

Well, that would definitely be too much leakage.

If you play with the force equations some, you might get a result
where the leaked air is still bound to the overall plate-planet. My
first thought was that this would lead to horizontal double-tornadoes
around the plate's perimeter... but no, that's a perpetual motion
motion. (I *hope* you keep your silly-gravity force conservative!)

I think it's still conservative. I'll have to play with it a bit to make
absolutely sure. If it's not, oh well, I don't mind infinite sources of
energy since they might help out with the lightsource problem and they could
be reverse to make infinite sinks of energy too, so everything balances out.
I'm now imagining giant 'gravity mills' set up on the edges of worlds to
provide limitless power (one side is pulled down by gravity, then the bottom
swings out over the edge and is lifted back up under nearly zero gravity,
then it gets pulled down again...).
The laws of thermodynamics are certainly not inviolate as I work out this
universe, though. I've been contemplating some sort of negative energy
production process as a solution to the lightsource problem, for example.

Try adding a trace of Newtonian gravity to your linear-gravity. That
should produce a plate-planet inside a very oblate spheroid of
atmosphere. Hm. Oblate? Now I'm not sure.

Well, the plate-planet's won't be completely two-dimensional- they have to
have some thickness, so when you go off the edge, there will be lots of
stuff that's not on a perfect horizontal with you and so will provide some
force. I'm just not sure if that can be made large enough to hold an
atmosphere, since the contribution of bits of the planet further in from the
edge, and the force on air particles farther out from the edge, diminishes
rapidly with decreasing angular size.

This would be a great adventure setting, in fact. The atmosphere
pancake would extend for thousands of miles, and would be nearly
zero-G -- you'd only need a trace of thrust (or lift-gas) to keep from
drifting in towards the planet. Sky-pirates ahoy! Of course, if you
cut in past the rim of the plate, you're suddenly plummeting...

Yup, that is the idea. If I were to go for the idea of filling the whole
universe with a sheet of gas that the plate-planets float in, Sky-pirates
could even sail between worlds just on unpressurized wooden ships. But I
really have very little idea of how such a sheet of gas would behave, and it
would mean everyone would have to breathe hydrogen (but I don't really need
to tell readers that, so it's be OK). Even if space is still a vacuum,
though, it makes interplanetary travel relatively easy to do with
not-very-high tech.

**entering a different topic, though it relates back to the atmosphere
eventually**

There will be hazards to being a Sky-pirate, though, besides her Majesty's
Royal Navy. The next strange and interesting difference from our universe is
that matter produces time in a bubble around it, but there's also some sort
of cosmological constant that sucks time away. The qualitative effect I'm
going for is that if you go too far from a large planet, your time will slow
down until you reach a new equilibrium between the time-production of the
mass you brought with you and time-loss to the universe, and below some
critical density you'll rapidly lose almost all of your time and become
essentially frozen. Frozen objects can be unfrozen just by moving so that
they come inside your time-field, but that uses up some of your time, which
you have to wait to build up again; so, you have to be careful about
encountering too many frozen objects at once, lest they steal all of your
time and you become frozen. And be careful about sailing too near things
that look like cannonballs or bullets, lest they suddenly unfreeze traveling
in your direction. Also, I'm thinking that anything that's producing energy
would increase time-production, so bringing a furnace along on your
Sky-pirate ship would help keep you from being frozen in time.
I haven't got even the basics of the math for how all that works figured
out, but more important to me at the moment is how to handle light and
relative velocities in that sort of space.
For example, when an object 'runs out of time', it has to stop moving from
the point of view of an outside observer- sure, it might still have some
velocity of x meters per second, but it doesn't have any seconds to move
per, so it just sits there. But you, observing it, still having time, could
move towards or away from it, so what is it sitting still relative to?
I've got two ideas at the moment. The first is that there is some universal
'rest frame of timeless space'. If that were the case, anything stuck
without time would appear at rest wrt everything else stuck without time. It
could make navigation pretty easy, since you could sail out somewhere into
timeless space, drop off some small reflective beacon that will run out of
time very quickly, and expect it to stay there forever, until something else
with time runs into it. Worlds moving against the background of timeless
space could be constantly picking up bits of interplanetary debris, and
leaving behind a trail of their own.
The second is that things come to rest wrt to some time-field defined by the
other masses around it, like a gravity well. That way, for example, if a
ship is traveling between worlds, and explodes, all of the little bits
quickly run out of time and freeze relative to the each other, but the whole
explosion-in-progress continued moving. That would require figuring out all
of the details of how time-fields merge, and how to define a frame for them
and stuff. Much more complicated.
So what does this all mean for light? Well let's say a lightbeam, traveling
at c, suddenly runs into timeless space. It's moving at 3E8 m/s, but it no
longer has any seconds to move per, so it all bunches up on the edge of
whatever time-field it originated in. That's bad if there's large separation
between this universe's planets and lightsources. One way to solve this
might be to say that light has infinite speed, or that it has some finite
speed in timeless space as seen by a time-full observer, but has infinite
speed when not in timeless space. I'm sure that would have some interesting
consequences. Another possibility I thought of is that light carries a bit
of time with it. That goes along with my idea that things that produce
energy produce more time, and it would mean that nothing that is illuminated
could be truly completely frozen, they could just get really close so as to
make no practical difference.

Alright, I said all that would relate back to the atmosphere, and it does. I
was thinking, perhaps atmosphere could be held against a planet because if a
particle of air gets too far away, it freezes in time, and eventually you'd
get a relatively dense shell of time-frozen air surrounding the world and
holding the rest in. That only works if there's a way to get air onto the
planet in the first place, but we can chalk that up to volcanic outgassing
or something. But that also only works if the time-frozen air moves through
timeless space along with the rest of the planet- otherwise, the back end of
the shell will be left behind, and the front end continually unfrozen by the
advancing edge of the planet, so the planet quickly loses atmosphere unless
there's enough just sitting around waiting to get swept up in timeless space
to replace it. Which pretty much amounts to the 'flood the whole universe
with a sheet of air' solution.

-l.
------------------------------------
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