• Member Since 28th Oct, 2012
  • offline last seen 1 hour ago

Pineta


Particle Physics and Pony Fiction Experimentalist

More Blog Posts367

Sep
6th
2019

Quicksand and the Physical Laws of a Novel Dimension · 9:46pm Sep 6th, 2019

To everyone interested in my project to commission some Particle Physics inspired stories, I am hoping to launch this soon, but it’s taking a bit of time to get everything ready. And I keep getting distracted by other things. More soon. Meanwhile…


Let’s revisit a scene in Spring Breakdown which is worthy of further study by those of you who love discussing how physical laws might be different in Equestria and calculating the density of air needed to support a flying pegasus and that sort of thing.

Rainbow “Danger” Dash is stuck in a pit of quicksand and needs to be rescued by her friends. Except it turns out it isn’t quicksand.

What is quicksand? It’s a popular trope in twentieth century adventure films, where, while trekking across a desert or through a tropical forest, the protagonist will fall into a sand-filled pool that threatens to suck her down to the depths of the Earth. And the harder she tries to pull herself out, the more it sucks her back. DUN-DUN-DUUUUN!!! Cue adventure film music.

Quicksand also features a lot in old children’s science encyclopaedias, usually with a simple explanation of how to escape from it, so a young reader will feel very clever knowing that if they ever fall into quicksand, they will know what to do because they know Science.

I have never encountered quicksand, but it is easy to find in the popular science blogosphere. The more convincing articles describe it as of a high density of sand grains mixed in water. It looks solid, until you step on it. Then you sink. If it’s thick enough then you may struggle to pull yourself out as when you pull your leg up, it creates a void in the mud which will suck you back. Some articles also explain that it can act as a non-Newtonian fluid, where, like tomato ketchup, the viscosity depends on the applied force, so if you hit it at speed while running, it is liquid and you sink. Then if you move slowly, it will feel solid and you get stuck. There is a fun demonstration of this by mixing cornstarch and water.

Fortunately as humans are less dense than wet sand, the weight of sand you displace will balance that of your body, and you will float. Nearly all articles assure the reader that you can only sink up to your waist in quicksand.


Now let us consider the balance of forces in Rainbow Dash’s trans-dimensional sticky situation. Sunset Shimmer shows the sand is just a thin layer on top of a portal to Equestria, and proves this by jumping through to emerge in a cave near Ponyville.


This would be a fantastic opportunity to study the physical laws of a novel dimension.

So when RD thought she was in quicksand, she was actually partway between worlds. In this case, what was holding her up at all? Why didn't she just fall into the cave? Going back to the much-debated topic of how pegasi fly, there have been ideas proposed that the Equestrian air is somehow denser. Presumably whatever magical pony buoyancy keeps winged ponies in flight was also supporting Rainbow's rear end in this scene. But then why was it so difficult for her to pull herself out?

This does also make you wonder whether at this time, she had a centaur anatomy, with her human head above the sand, and pony things dangling from the roof of a cave? She had a bit of trouble to get used to her flying skills once she realised she was a pony, but imagine how confusing it must be when your spinal cord crosses a portal and the brain has no knowledge of limbs it is controlling, but you are thrashing about wildly to try to keep your head above the surface.

Join our Patreon to remove these adverts!
Comments ( 10 )

One alternative is the Stargate approach, in which each end of the portal is attached to a "waiting room", which buffers the parts of your body that cross through until the whole thing can be sent.

The first Equestria Girls movie has an effect that implies this, as Twilight gets flushed through a Dr Who-like tunnel and transformed in the process.

PresentPerfect
Author Interviewer

Oh god, I don't want to think about half-formed equine anatomy while stuck in a portal. @_@

I much prefer the Stargate way, as 5117167 outlined. In which case, it’s entirely possible that a powerful magical entity actively resisting a portal’s magic significantly slows the process of going through it.

Quicksand can be extremely nasty stuff indeed, as you not only get superfluidisation due to the flow of pressurised water suspending the grains, but entrained air escaping can reduce the density even further, and even worse, if the fluid level, is level, it means that the jet(s) of water flowing Up, are also flowing Down. Or at least forming circulation flows.

Gee, Quicksand with Rips.

I think the local lost railway was lucky in that it was a fairly static layer of quicksand they dug into. In that they could build a stable raft over the layer instead of it being strong enough to flow damage even that structure. Always intresting to watch the council have to add another few inch of tarmac to the road alongside to raise it back up again every ten years or so. The wall along the road has a Very noticable dip, at least a couple foot down, for maybe a hundred foot.

I always thought the Stargate was a Quantum Wormhole. Less than one atomic bond long?

Are we sure about the orientation of the Everfree end of the portal? Depending on which way it's pointing, gravity could keep Dash in equilibrium until Sunset shoves her through.

5117167
On the other hand, the first movie also gave us this image:
derpicdn.net/img/view/2013/7/25/383508.jpg

Though that does raise the question of what the ponies waiting by the mirror saw...

5117167 5117215
The fact that it is called a mirror make me think of it as a 2d boundary between worlds. But other interpretations are just as valid.

5117173
Is it really as unthinkable as some of the scenes in some of the stories you have reviewed?

5117230
Superfluidity is a macroscopic quantum phenomena that happens to helium at very low temperatures. I don't think that applies to your average sand pit. But quicksand can indeed be nasty stuff.

5117356
I was at first thinking the portal was on the floor in Equestria, so with a 180 degree turn, Dash could be in equilibrium falling out of both worlds. But watching the clip again, it seems to be on the roof, but maybe at an angle. Another parameter to factor into any theory.

"calculating the density of air needed to support a flying pegasus " Is that aimed at me? :P Actually I saw elsewhere it wasn't. Since their non-sentient birds fly more or less normally, I proposed it was a magic field that interacts only with magic particles, permitting flight by Pegasi and Griffons, but leaving mundane lifeforms unaffected. It has the advantage of avoiding potential issues with air pressure and Earth-like critters.

I did love that bit about "studying the physical laws of a novel dimension" either way.

5117608
You're not the only one, but I think you went further and into more detail than the others.

5117650
Well for my part, I got the germ of the idea from Terry Pratchett's books.

I've not heard more than a mention of the basic idea, myself (and that was after I started working up a write-up). 'Course, I don't do deep dives into the community much.

Login or register to comment
Join our Patreon to remove these adverts!