There’s a good bit of entertainment in here whether you like amazing, beautiful, cute or funny stuff.
Ok, we need to talk about this. This is a spider setting up a cozy little home.
Essential steps and the abilities they require (require of Something, not necessarily of this exact spider)
- What made him do this, “I need a place to sleep.”? (Executive function: I better get this done)
- What makes him choose this one shell out of many? Did he check it out for size? (Critical thinking: This one will work better than those)
- Did he set up that block and tackle lifting system ahead of time? (Foresight: I’ll need this in a few minutes)
- How did he know “That’s about enough” after wrapping the shell for lifting? (Predicting outcomes: This is enough to haul it up without falling)
- Do spiders have imagination and logic? (Creative thinking: Hey…those things would make good houses!)
Most people would say “It’s instinct, it’s just instinctive behavior” putting the issue to rest. Here’s the definition of instinct “An innate typically fixed pattern of behavior in animals in response to certain stimuli”.
Instinct sounds meaningful but it isn’t. “Instinct” is a tautology, circling the question. Semantically it says “Yes, that behavior is a thing.” or “I don’t know why or how, but they all do that” or even “That’s what it is, but we don’t talk about that”. The word instinct is a placeholder description, not a real answer. Saying Instinct shuts off questioning without providing answers, it is an empty box labeled “behavioral presets”. The classic Darwinian answer to “But how, why?” would be “Spiders that behaved this way were better at surviving and reproducing. That is why the behavior was retained”. Continue reading
I could happily sit on the floor playing with magnets for a couple of hours. I have never outgrown the delight of feeling invisible forces at work, all the more because magnets almost seem to possess some agency and a playful nature. Like baby monkeys, they snatch things that get too close and the next minute freak out and run away. If you look back a couple of posts at the one called ‘magnets sorting themselves out’ they move like highly trained but bumbling soldiers racing to stand at attention, and in formation. They show what feels like certainty about their destination and they seem to clamber over each other to get there.
The thing about invisible forces is how difficult it is to properly imagine what is taking place. If we never saw air moving through smoke or mist, the wind would be a similar mystery to our imagination.
The only way to see the shape and force of a magnetic field is similar to seeing the wind act on smoke. We can’t see the force in a pure, abstract way… we need to see it acting upon something. We need a material the magnet will engage with, but not a large, lumpy object like another magnet. We need something like a cloud, made of tiny, reactive particles. To the right is a familiar image of light iron filings scattered like sand on paper lying atop a horseshoe magnet. A little gentle tapping on the paper and they line up cleanly along the magnetic field lines. If you want a better look, it’s linked to a full-size version.
This is a rather static vision of the effect though. Below is a slightly more dynamic way to see it. Rather than paper, it’s a clear acrylic box with a liquid suspension of iron filings.
It’s better, we can even get a little taste of the three dimensionalities of the effect. Remember though, we never see a magnetic field acting in a vacuum. Iron filings don’t show the truth of magnetic fields, they show that truth as applied to iron filings.
Ferrofluid shows that truth acting on a rather dense liquid. There’s an earlier post on the composition and history of Ferrofluid. Take a look if you need a touch more foundation. Basically, it’s a colloidal suspension of magnetic nanoparticles. Ferrofluid breaks the “fourth wall” of being demurely flat and passive. It’s often in a bowl or other container, open and available to us. The very different physics of a liquid and a powder are instantly apparent. Ferrofluid makes one think of an alien life form or some stylish evil entity. It undulates, it climbs up and down surfaces like sentient oil. It even leaps. It appears to have moods, and rather peculiar ones.
While this view of magnetic fields is not truer than the behavior of iron filings, it’s more dynamic and thrilling. It’s truer perhaps in that way. From the point of view of magnetic energy, peaks and valleys are energetically favorable. In the corrugated configuration, the magnetic field is concentrated in the peaks; since the fluid is more easily magnetized than the air, this lowers the magnetic energy. In consequence, the spikes of fluid ride the field lines out into space until there is a balance of the forces involved.
At the same time, the formation of peaks and valleys is resisted by gravity and surface tension. It requires energy both to move fluid out of the valleys and up into the spikes and to increase the surface area of the fluid. In summary, the formation of the corrugations increases the surface free energy and the gravitational energy of the liquid but reduces the magnetic energy.
Just for fun, ferrofluid mixed with glow-stick liquid:
And finally, with some awesome coloration in the mix.
I love this, especially the fact that time passing looks like an intense wind blowing around him.
Credit to David Espinosa
Ferrofluid is a liquid that becomes strongly magnetized in the presence of a magnetic field. A grinding process for ferrofluid was invented in 1963 by NASA’s Steve Papell as a liquid rocket fuel that could be drawn toward a pump inlet in a weightless environment by applying a magnetic field. Ferrofluids are colloidal liquids made of nanoscale ferromagnetic, or ferrimagnetic, particles suspended in a carrier fluid (usually an organic solvent or water). Each tiny particle is thoroughly coated with a surfactant to inhibit clumping.
When a paramagnetic fluid is subjected to a strong vertical magnetic field, the surface forms a regular pattern of peaks and valleys. This effect is known as the Rosensweig or normal-field instability. The instability is driven by the magnetic field; it can be explained by considering which shape of the fluid minimizes the total energy of the system.
From the point of view of magnetic energy, peaks and valleys are energetically favorable. In the corrugated configuration, the magnetic field is concentrated in the peaks; since the fluid is more easily magnetized than the air, this lowers the magnetic energy. In consequence, the spikes of fluid ride the field lines out into space until there is a balance of the forces involved.
At the same time, the formation of peaks and valleys is resisted by gravity and surface tension. It requires energy both to move fluid out of the valleys and up into the spikes and to increase the surface area of the fluid. In summary, the formation of the corrugations increases the surface free energy and the gravitational energy of the liquid but reduces the magnetic energy. The corrugations will only form above a critical magnetic field strength when the reduction in magnetic energy outweighs the increase in surface and gravitation energy terms.
Ferrofluids have an exceptionally high magnetic susceptibility and the critical magnetic field for the onset of the corrugations can be realized by a small bar magnet. – Wikipedia
A ‘star drop’ refers to the patterns created when a drop, ﬂattened by some force, is excited into shape mode oscillations
Abstract: “These patterns are perhaps best understood as the two-dimensional analogs to the more common three-dimensional shape mode oscillations. In this ﬂuid dynamics video, an ultrasonic standing wave was used to levitate a liquid drop. The drop was then ﬂattened into a disk by increasing the ﬁeld strength. This ﬂattened drop was then excited to create star drop patterns by exciting the drop at its resonance frequency. Diﬀerent oscillatory modes were induced by y varying the drop radius, ﬂuid properties, and frequency at which the ﬁeld strength was modulated.”
“Shape oscillation of a levitated drop in an acoustic ﬁeld,” by W. Ran & S. Fredericks (Clemson University, Department of Mechanical Engineering)
If the title is confusing, I apologize. Emergence is a huge focus of my writing and explained in depth elsewhere in the site. A short version is: Emergence is when a new and surprising result emerges from grouping enough of almost anything together. The effect doesn’t resemble the individuals it emerges from. The things being grouped in this video are individual Starlings, the grouping is their seasonal flocking behavior. The emergent effect is the murmuration, the huge, shapeshifting display of their collective flight. No bird is in charge, the effect is bottom up as the individual birds react to each other yet we see what feels very much like a huge excited individual playing in the sky.
A cuttlefish transmitting social information via pattern and color change. Apparently, this display means he’s really pissed off. Watch till the end and you’ll be in no doubt.
All cephalopods; cuttlefish, squid, and octopus use the same remarkable technique to communicate among their kind and camouflage themselves.
Close up of a squid’s color-changing cells called chromatophores. Amazingly these cells blend shades to create colors outside their individual range much as we can blend red, green and blue to create any color. Odder still, all cephalopods appear to be color blind.
Finally, here’s an octopus giving a practical demonstration of using chromatophores for camouflage.