14 KiB
[FF] [RST] Fling a Light 1.04 (Worm)
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Author: u/UltraRedSpectrum *
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Score: 12
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Created: 2016-03-13T03:10:04
Post:
Comments:
u/themousehunter [+5] Sunshine Regiment (an hour later)
I really enjoy your writing! Hope you keep up the pace with updates!
u/rationalidurr [+3] If fighting is sure to result in victory, then you must fight! (13 hours later)
OP, if you need good ideas on what to do with 2 portals, read some Saga of Soul. The author went into considerable detail with Earth's rotation and various matter acceleration. Also a good science girl story in general.
Write more please, economic uses of powers are very rare in ratfic.
Good emotional actions and good introspection. Also a good idea to just wait and get help form secret keeping authorities.
u/UltraRedSpectrum [+2] (16 hours later)
At present, I have enough ideas to fill the story entirely (though they aren't all mine). Also, I get the impression that I'll be getting more than enough from this subreddit. For example, I'd underestimated the wind speed generated by a portal to the upper atmosphere, which might be important later on.
I'm still not 100% sure about some of the plot details. There are things that need to happen, but how they happen is going to depend on other things. I've got a "bag of tricks" for Taylor, so to speak, and a list of things she's going to want to do, plus an ending, a bunch of antagonists, and a plot outline. I'm terrible at following my own plans, so even that much is probably going to mutate.
u/UltraRedSpectrum [+3] (2 minutes later)
In case anyone was wondering: http://what-if.xkcd.com/66/
u/ulyssessword [+4] (an hour later)
I really, really doubt if she could actually make 500 MPH winds using her method.
Sure, it would work if she sealed both ends of a frictionless tube, but there is huge (and exponentially scaling) resistance from both the walls and from the wind that misses and hits the floor beside the portal. I don't think she could even generate a strong breeze using that method.
u/UltraRedSpectrum [+2] (2 hours later)
I'm not about to give Taylor an understanding of higher-level math or physics (or economics, for that matter). Not accounting for wind resistance in a physics problem that involves accelerating the air itself is a completely reasonable mistake for a fifteen-year-old who is presently being duct-taped to a wall. I think a strong breeze is underselling it, though, seeing as she created (transferred?) almost a megajoule of energy, which is about as much as you'd get from a stick of dynamite.
The link is for her claim that 500 mph winds would rip pavement out of the ground and throw people around.
u/ulyssessword [+2] (2 hours later)
I'm not about to give Taylor an understanding of higher-level math or physics (or economics, for that matter). Not accounting for wind resistance in a physics problem that involves accelerating the air itself is a completely reasonable mistake for a fifteen-year-old.
Maybe I should've made a new top level comment instead of a reply. I don't think that her method could produce strong enough winds to threaten to drag desks around. Her ideas about what strong winds could do seem accurate.
On the other hand, I think opening a portal to the upper atmosphere would be very effective, producing winds of about mach one at the portal boundary.
u/JackStargazer [+3] Primordial Apologist (15 hours later)
On the other hand, I think opening a portal to the upper atmosphere would be very effective, producing winds of about mach one at the portal boundary.
This was what I was thinking she would do instead of the perpetual motion machine. That and opening a portal to the bottom of the Marianas Trench and firing super-pressurized water beams were the obvious combat uses of full-range portals to me.
u/UltraRedSpectrum [+2] (2 hours later)
Well, I'm not a physicist, so I don't really know. However, when I type "megajoule" into Google, I get this:
approximately the kinetic energy of a one megagram (tonne) vehicle moving at 160 km/h.
If we assume that, as you said, almost all of the energy is being lost to wind resistance, that means that we have as much energy as a car driving 8 km/hr through a classroom every second over the course of 20 seconds. Since a car can obviously move a desk, I declare this problem solved.
(That was a joke. I genuinely have no idea how to do this kind of physics.)
u/duffmancd [+6] (8 hours later)
So, I think we can all agree that if the air was in a frictionless tube bewteen the portals it would accellerate at g.
Next, we have two problems, friction with the surroundings and that the portal doesn't cover the whole floor. Given the fact that the portal is not a laval nozzle, the fastest the air can move through it is the speed of sound. So this gives the upper limit on the energy gained per second. This power is Area of the portal x Velocity (300m/s) x Density of Air (1kg/m^3) x height change. For a portal 1m in diameter, and a 2m high room this is: 471W
My desktop fan is 40W, so our 1m diameter portal with supersonic air flowing through it develops the same power as 12 of these. Needless to say the air would not be able to reach supersonic speeds, but ignoring that lets just assume we develop the full 500ish W. Taylor here would be able to cause quite a bit of a mess, a lot of noise and possibly scare the terrible trio but wouldn't hurt them with this trick.
How could she actually hurt them? Water is 1000 times as dense as air and has a speed of sound 4 times as fast. (Water jet cutting can cut through steel with an abrasive. People are squishier) A portal to the depths of the ocean would provide pressurised water, though you'd have to set it up ahead of time with Taylor's limitations (Maybe in a sealed strongbox, then you make a second portal from the box to enemy number 1). Moving the upper portal higher would also work (there was that height of room coefficient) though in a non-closed room you'd run out of air quickly. So actaully the best way might just be to open up a portal to the upper atmosphere behind your victim and let the explosive decompression deal with them. (Let alone actually just dropping them through a portal).
[Off topic] I just had the idea of using portals to below the ocean like those water jet-packs to make flying possible if a bit wet for those below.
u/duffmancd [+5] (8 hours later)
For the record vertical wind tunnels (for indoor skydiving) are about 0.6-1.4MW in power. This is electrical power so multiply by a prop efficiency of around 80% at design speeds to get aerodynamic power. So an exit portal a few thousand meters in the air would accellerate the air to approximately human terminal velocity in the area around the portal - unfortunately in the wrong direction to use as a blast.
u/chaosmosis [+1] and with strange aeons, even death may die (a day later)
[Off topic] I just had the idea of using portals to below the ocean like those water jet-packs to make flying possible if a bit wet for those below.
Can she fix portals relative to herself or her equipment rather than relative to the Earth's surface? I suppose if not she could make a succession of portals, but that would require a lot of micromanaging.
u/duffmancd [+2] (2 days later)
I got the idea somehow that the portals were stuck to the surface they were placed on, but now I remember that she's had portals in mid-air before so maybe not.
u/VanPeer [+1] The shard made me do it (3 days later)
I think we can all agree that if the air was in a frictionless tube bewteen the portals it would accellerate at g.
I'm not so sure about that. (This is only for a fun thought experiment, not for nitpicking the story). If the portals are in vacuum, I can see a small object falling endlessly (as long as the potential energy for sending the object back up to the higher portal is supplied from somewhere). But this is a volume of gas that spans both portals. The gas trying to fall through the lower portal will be sitting on the gas at the higher portal. So will the gas accelerate at all? I suspect not.
A portal to the depths of the ocean would provide pressurised water
Excellent idea ! Also a similar idea from Stargate SG1/Portal: Have a Tinker fabricate a stationary gigawatt laser and use the portals to wield them at will.
u/duffmancd [+1] (4 days later)
So two other ways of thinking about it, to hopefully convince you even air will accelerate at g in the frictionless case.
First think of fluid dynamics. At the very moment the portal is opened, the air at the bottom will be slightly higher pressure than the air at the top, so whe the portal opens it will be sucked through (and the air at the top pushed down equivalently) . Gravity will continue to supply ~2m of head between the portals and with no friction the only place for that energy to go is into speed.
The other way to think about it is imagine the gap between the portals is filled with a stack of boxes. Now you may think if they're packed tight they wouldn't fall. But consider what would happen if we removed, say the middle layer. Obviously, the one above, with nothing to support it would begin to fall, an all the other layers would fall with it. Negating air resistance, what would happen to the space - it would have to remain the same size as all the boxes are resting on each other. What if we instead removed the bottom layer? Again everything would fall, and the middle layer would fall exactly in line with where the gap was. So, imagine putting them together, nothing changes everything falls. Without something outside to rest on, there can be no upwards force to balance gravity and everything will fall at g.
Does that make sense?
u/Ilverin [+2] (13 hours later)
A portal to the upper atmosphere or space would have a massive sucking effect, the problem is this sucking effect would also affect Taylor.
u/Lugnut1206 [+3] (19 hours later)
taylor is presently stuck to the wall
perhaps a larger issue would be that the bullies would literally get sucked into space
u/elevul [+1] Cyoria Observer (a day later)
I don't see any issue with that.
u/Ilverin [+1] (13 hours later)
If there are portals such that a volume of air is enclosed (it's not clear from the text whether 'filling the room' entails sealing a volume of air) on all sides, all of the air would be accelerated, and missing one portal would mean entering another one. (I'm imagining a cube or triangular prism of portals).
u/ulyssessword [+1] (17 hours later)
We know that it's not a sealed prism of portals because the desks were moved by the wind.
Although a prism would be pretty cool, as it would allow unbounded acceleration (which would also tow the earth in its direction a negligible amount). It would take about 6 months to reach half the speed of light using this method.
u/Lugnut1206 [+1] (20 hours later)
what if she made a cube of portals? it'd be functionally frictionless, and if she can make the entire cube at the same exact moment, the air couldn't collide with slower air, because it'd all be moving at the same exact speed?
u/ulyssessword [+2] (20 hours later)
That would work, but it doesn't match what was described in the chapter.
u/Lugnut1206 [+1] (20 hours later)
yeah, true
u/duffmancd [+2] (8 hours later)
Yay, the world continues to be a complicated place. Poor Taylor. Next I would expect kidnappings as she basically explained to herself how she was going to take over the world with her power - everyone is going to want some of that if they think they can get at her. Interested to see where this goes.
u/VanPeer [+2] The shard made me do it (2 days later)
Interesting! However, as others have pointed out, opening a portal to the upper atmosphere will create high velocity winds much more readily; with velocities approaching Mach 1 (750 mph) before [choked flow] (http://web.mit.edu/16.unified/www/SPRING/fluids/Spring2008/LectureNotes/f20.pdf) conditions are reached.
Looking forward to the next installment. Also, you mention that her physics knowledge is that of a typical high schooler; but her knowledge of economics is impressive and way beyond a teenager. Is there a special reason for this? Or is that her hobby ?
u/UltraRedSpectrum [+2] (2 days later)
The more political your parents are, the more you pick up over the dinner table. Between a lecturer for a mother and a union spokesperson for a father, she got an extensive - if slightly biased - education in a wide variety of topics. From a Doylist standpoint, I've loosely pegged her knowledge to what I knew/believed when I was fifteen.
u/Gigapode [+1] (a day later)
I really liked this chapter, and what it implies about the next one. Thanks for bringing this story to my attention.