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Draw an iceberg and see how it would float in water

joshdata.me

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Re: Draw an iceberg and see how it would float in water

#101

Post by _tom_ »

JBiserkov wrote: post #14

Great page! Was this inspired by https://twitter.com/GlacialMeg/status/1362557149147058178 ? Try drawing the infinity symbol under water - mine jumped out of the water! It even jumped off screen, and ended up like an 8, half submerged, half above water. My other attempt hit the water/air boundary from below, and bounced back towards the bottom, off screen again, and reappeared in a bit.

There seems to be a bug with figures with boundaries that cross each other. Perhaps there is an issue with determining inside vs outside for the figure.

An infinity symbol drawn so the line crosses itself has issues. If you trace the outside of the symbol, without crossing, it works as expected.

Re: Draw an iceberg and see how it would float in water

#102

Post by 5600k »

arithma wrote: post #74
sgtnoodle wrote: post #67

Earlier quoted context omitted.

The code must somehow compute bouyancy in a way that reflects the object's arbitrarily complex shape. It's likely carving the object up into some number of smaller primitive objects whose equations for bouyancy are known. In order to make the whole object move as one rigid body, though, it's probably computing force vectors for each primitive, and then summing them together based on the overall object's center of mas…

I knew this was happening, but reading it, hey, maybe that's one way to get anti-gravity. Just loop the topology on itself. Obviously commenting in jest, but now I'm intrigued to see if someone has seriously considered this.

One of the theoretical reverse time travel machines I read about in the past involved stabilizing a wormhole first and then dragging it somewhere else, like to the future relative to current time by traveling near light speed with it, so you could get back to the earlier time.

Kip Thorne wrote of something that involved an extreme amount of mass in a spinning cylinder. That kind of mass was imagined to be at a huge scale like harnessing a number of stars and compressing them, iirc.

A device theorized or implemented by Salvatore Pais involves use of superconductors and microwaves to create an effective vacuum, like dragging part of spacetime. It could allow FTL relocation without actual speed. This could also create an area of effectively high masses that could allow time travel, even eventually reverse time travel, under theoretical conditions.

Re: Draw an iceberg and see how it would float in water

#103

Post by sgtnoodle »

chrisdalke wrote: post #65
praptak wrote: post #53

Earlier quoted context omitted.

When it comes to stability there is a crucial handicap between ships and icebergs. The former have non-uniform mass, so it is possible for a ship's center of mass to be below its center of buoyancy. That's why ships have ballast - it lowers the center of mass relative to the center of buoyancy. An iceberg is uniform, so its center of buoyancy is always below its center of mass. This makes its stability trickier, as i…

Good point -- The way I described it really applies to _any_ object floating in water. I don't have much experience with ship design, but on small boat design you can rely mostly on the geometry of the boat to produce a sufficient righting moment even with a very high center of mass. Some off-shore speedboats have really incredible self-righting because they've been designed to always have positive stability at all a…

It's possible to engineer a stable boat in this simulation based on that principle for stability.

https://ibb.co/T1KG5DM

The trick is to draw a low-mass object with high displacement, which happens to be possible because of the existence of, uh, anti-iceberg? that has negative mass.

Re: Draw an iceberg and see how it would float in water

#104

Post by praptak »

chrisdalke wrote: post #65
praptak wrote: post #53

Earlier quoted context omitted.

When it comes to stability there is a crucial handicap between ships and icebergs. The former have non-uniform mass, so it is possible for a ship's center of mass to be below its center of buoyancy. That's why ships have ballast - it lowers the center of mass relative to the center of buoyancy. An iceberg is uniform, so its center of buoyancy is always below its center of mass. This makes its stability trickier, as i…

Good point -- The way I described it really applies to _any_ object floating in water. I don't have much experience with ship design, but on small boat design you can rely mostly on the geometry of the boat to produce a sufficient righting moment even with a very high center of mass. Some off-shore speedboats have really incredible self-righting because they've been designed to always have positive stability at all a…

Yes, small boats are often constrained by shallow water, so they cannot have too much ballast not to mention things like bulb-keel. This means the hull needs to be sufficiently broad and flat.

Re: Draw an iceberg and see how it would float in water

#106

Post by madprops »

_kst_ wrote: post #9

I get interesting results if I draw a figure 8 (or a figure ∞). I wonder if it's treating one of the lobes as having negative density.

I tried with a timeglass-like shape. It flew around the map, going in and out of view and eventually setting on/in the water https://i.imgur.com/kcT9elV.jpg

Re: Draw an iceberg and see how it would float in water

#108

Post by sgtnoodle »

rampant_ai wrote: post #92
maxrmk wrote: post #71

Earlier quoted context omitted.

I spent... longer than I should have trying to take advantage of this bug to recreate a stable version of the stereotypical tall iceberg that the original tweet was complaining about. https://imgur.com/a/WG6D0RJ

I was able to make sailboats that float if I cross the line over itself so the sail is in "negative space", which keeps it upright. Kinda neat! https://i.imgur.com/2LZn50v.png

It's prettier than my boat. :-)

I believe it works because the sail consists of negative mass. The overall mass of the boat is therefore lower, but the part of the hull that's under water produces the same amount of bouyancy based on the area of displaced water. Because of the width of the hull, it's a stable equallibrium.

Interestingly, if the sail were to become submerged, it would create negative bouyancy and the boat would sink!

Re: Draw an iceberg and see how it would float in water

#109

Post by Sharlin »

croes wrote: post #77
_kst_ wrote: post #9

I get interesting results if I draw a figure 8 (or a figure ∞). I wonder if it's treating one of the lobes as having negative density.

Fo be fair, this shape is hardly possible for a real iceberg.

You mean there are no zero-volume nonorientable-manifold Klein bottle icebergs in real life? :(
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