It goes from one side of the pond to the other and I can’t id any current that’s moving it. I can’t catch them at it, but Ari is not afraid of it, and she could certainly nudge it over.
I think the fish are using the bubble as a taxi…
by CJ | Aug 30, 2015 | Journal | 33 comments
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Ummm, wait a minute! Come back here! Can’t let that one pass.
If a fish was up inside and swam in one direction, he’d go until he bumped his nose into the side, but then swim as he might, the dome is going nowhere, if I’m picturing this thing right.
maybe they’re bumping their noses into the side, and it moves slightly, so that they swim forward, and again bump their nose, and it moves slightly, etc., etc.?
Fill a delivery truck with parakeets. Lots of parakeets! Fat, heavy parakeets. You’re over the weight limit! There’s a weigh station ahead! You’ll never make it. Oh, go outside and bang on the side of the truck, scaring the parakeets off their perches so the parakeets all fly around. Now you’re OK to go through the weigh station, right?
Here’s an experiment: Build a solid 5-sided box (open top) with pontoons on the side so’s it floats real good. Take it to a lake. Fill it with water. Put a board across the center of the box. Mount an outboard motor to the board, i.e. the propeller is in the water inside the box. Start the “outboard” motor. How far is it going to get you? Better mount the motor on one of the sides so’s it can push on the lake’s water.
So, only if the fishies outside at the time. A force to move the dome must be exerted outside the dome, against something else.
But it’s a dome, not a sphere. Even if it’s a hemisphere, Ari, say, bumps her nose into the dome and moves it; Ari’s tail-wash hits the dome, is redirected downward, and jets the back of the dome up. If the dome is shallow, much less than a hemisphere, it might tilt enough that Ari’s tail-wash would clear the edge of the dome; in any case the tail wash would only be directed somewhat downward.
You’re right in principle–flying a drone or R/C helicopter on a scale is a great science demo–but I think you’ve over-applied a smidge.
They’ve named some features on Ceres. I especially liked Kirnis, Lithuanian spirit, guardian of cherry trees. For more explanations, look to the IAU database linked in the line, “The International Astronomical Union recently approved a batch of names for features on Ceres.” (Good source of character names?)
http://www.jpl.nasa.gov/news/news.php?feature=4669
1. It’s a hemisphere. 2. there’s a closed-cell styrofoam ring that creates the buoyancy (and it’s significantly buoyant – I know from experience, I tried to get the thing submerged for CJ and Jane). 3. I believe you’re overanalyzing the whole thing. What if Ari’s energy of impact is greater than the energy generated by her tail swish? What would the reaction be? There’s no saying that she continues to swish her tail even after she bumps the edge of the ring, at least not until she tries again.
Paul, ever see a large appliance box? A child can put one of those upside down over themselves and push it along the ground. They can even shove it in increments. The difference is the medium that they’re in as opposed to the fish. Even though Ari’s in water, there’s still some slight friction, and if she’s bumping the ring, she’s imparting energy to it, possibly sufficient energy to move the ring slightly. You may dismiss my argument as facetious, but I believe the principle is the same.
Let’s not forget that there is also a waterfall in the pond, and that the action of the water flowing after it leaves the waterfall might also have an effect….
But Joe, if the child has it “upside down” with his feet on the carpet, then he’s pushing against the floor, external to the box. If you were to leave the box with the top open, bottom closed, lift the child unto it, so (s)he’s standing on the bottom, (s)he’s going nowhere. All (s)he can do is try to tip it.
There were two possibilities, either you were being facetious, or just erroneous. I’m just talking basic Newtonian physics.
If we were talking about one of the inflated spheres we sometimes see at amusement parks, the person inside can rotate the sphere, which pushes against the ground, or sometimes the water. As you say, water isn’t entirely frictionless. Put such spheres on a frictionless surface and the person inside can run all (s)he wants, (s)he’s going nowhere.
Take a cruiseship. In every cabin put a fan, facing the rear of the ship. Turn all the fans on. Does the ship move? You’d have to take them up on deck!
Certainly water falling from a height gains momentum from the change in “potental energy” of the height, creating currents in the pool which move things about. As it sticks up, and is not anchored, wind can also push it about.
In all cases “every action is opposed by an equal and opposite reaction”, and it can’t be a reaction from within itself. It must be external. I’m certainly not denying that the dome will move, just what can and cannot make it move.
Take the case of the astronaut in space with a broken tether. Certainly by throwing something heavy, (s)he will move in reaction. But encased in a box, as the mass hits one side and the astronaut the other, they cancel out and the “system” goes nowhere. This is a close approximation of what I imagined was being proposed–the water up inside being pushed by Ari’s swimming hits the far side of the dome, cancelling out her momentum.
Now if she sank a bit, so her nose was against the dome, tail below the dome, pushing against the water in the pool, then she certainly can move it. Or we surround her with a tube that exits outside the dome, then Ari becomes the motor of a “jet boat”. There are ways we can contrive it, if we can arrange to get the force she generates outside her containing environment.
Paul, that’s right in theory, but just today I saw a real-life example where it worked in practise. A 8,5 month old baby in a camping cot (5-sided box, closed side down, on short legs) managed to walk the whole cot sideways by about 2 feet -60 cms. He did so by getting up on hands and knees and swinging backwards and forwards (he wants to crawl but hasn’t quite got the hang of moving his knee under his belly to do so yet). There must be variables in how or how fast he moves backwards compared to forwards, and maybe there’s a difference in the friction of the legs on the hard laminate floor; but then, Ari might introduce such unknown variables to the bubble floating in the water as well.
It seems to me real-life has a habit of not conforming perfectly to theory (mostly because we can’t know al the variables perfectly).
Oh no, not a bit of a problem with that! Certainly by shifting one’s weight around within a confined space, one might be able to get “purchase” of the confinement with it’s friction against the surface it’s on. That doesn’t work on a frictionless surface.
Researchers on Rapa Nui have walked moai down a road, standing up as legend has it, using friction.
What is happening here is what always happens when people claim to have invented a perpetual motion machine, equivalent to violating the Laws of Thermodynamics. They always violate the “containment of the system”.
Paul, having observed Ari in the pond, she often swims with her head close to the surface, and her tail deeper, so she does get a bit of the backwash thrust down under the ring…..just saying. I agree with your assessment of Newton’s Laws, and yes, you are correct, but even in water, there is still some friction with the medium, otherwise, fish wouldn’t be able to swim as the water would just slip around their fins……
I don’t believe I was being either facetious or erroneous, as even though the child has friction with the ground, so do Ari’s fins with the water, albeit to much less of a degree than the child’s soles. I did base my premise on observing the fish in CJ’s pond, not just Ari, but all of them, and they pretty much all seem to swim that way at times, especially if there’s something on the surface that interests them.
@Joe Certainly they do that when being fed, or sometimes they just seem to be gulping air. Oxygen starved environment?
It certainly appears, in the site CJ posted those are huge koi, relative to the size of the dome.
But when the Subject says “taxi” and doesn’t mention specific fish, I can be forgiven to have the image of a fish entirely within the dome, swimming in some direction, staying relatively in position within the dome and because of the fish’s action the dome moving directionally around the pool. That ain’t gonna happen! What you seem to be suggesting with Ari, conjures up more the image of Fred Flintstone’s car! 😉
@chondrite Go ahread and prep for Ignacio, I suppose, but right now he’s left pieces of himself trailing almost back to San Diego! But Jimena is twisted up real good, so it won’t have been wasted effort. That’s the one I’d be scared of.
Not too concerned about either of them right now. They are both on north-bearing tracks that will take them away from Hawaii; Jimena in particular is still about 500 miles out and is almost at the same latitude as the Big Island. I have never seen a hurricane track threatening Hawaii that doubles back and heads south once it starts going north, so I feel relatively safe right now.
Naw, I don’t like this suit, Sam. I’m gonna change my costume.
Even though that is a nice, smooth dome, it might be high enough for the wind to catch. Of course I’d like to believe in concerted fish conspiracy as an explanation. Some of those things are big enough to burn diesel as the saying goes.
Certainly! Let’s get one fishy “passenger” inside the dome, and the rest on one side out in the pool, noses to the ring, all swimming in one direction! 😉
I haven’t seen it, but understood that it floats because there’s a styrofoam ring around the bottom. So the fish could move it by butting at the styrofoam, when they’re swimming below or behind it. Like kicking a ball ahead of you while you walk, just playing with it. Of course, if another fish went into the dome during this, that one would get a taxi ride.
How does the floating around go with the anti-eagle netting? Is tge netting high enough for it to have room to move under it, or does it have to push the netting up wherever it goes? That would require quite a bit more strength.
I’ve wondered if the magnified fishes inside would work like eagle-bait; or if the hard dome would make a fishing dive more difficult, but if it’s under the netting it probably makes no difference.
you are correct, there is a styrofoam ring..it’s actually quite buoyant, as CJ, Jane, and I can attest.
YES! Somebody gets it! 🙂 🙂 🙂
Lol—I love your parakeets. But Ari is somewhat larger than a parakeet, and I think that salmon-sized tail might protrude beyond the styrofoam below, while her nose is pressed to the bubble. I have yet to SEE it moving, but wander it does.
The answer is, the driver is still busted!
Even if the tail didn’t protrude (which it seems quite likely to, considering the pictures CJ linked), the way she swirled the water with her momements might tend to push the water down and backwards, out of the bubble; that would suck in replacement water from along the front edge; both of those waterflows would pull and push the bubble forward. Considering the ways fish normally propel themselves through the water in 3 dimensions, this doesn’t seem an unlikely scenario.
Paul, I don’t know much about physics, but is seems to me you may have discounted the free flow of the water between the bubble and the pond in your theoretical solution.
Momements = movements. I dislike typing on my phone!
Next pond accessory: a tiny lighted taxi roof sign for the bubble!
or
Paging Aquaman… paging Aquaman…
or
*cue ‘Jaws’ theme* Hey, Ari is apparently big enough!
BTW, I haven’t been able to get a good image of the fish using it, but these people (probably have been baiting the dome) have…
http://gizmodo.com/a-floating-observation-dome-gives-fish-a-glimpse-of-the-1709547254
That video is sort of creepy in that i suspect the next thing will be a hamster-ball designed for fish to go running across the lawn…..
The heat generated by having more surface exposed to the light might also have something to do with the movement.
Errm, smileys seem to be gone, not rendered. (I didn’t much like that set anyhow.)
I thought I typed semicolon right parenthesis. Lemme try again. 😉
I agree: the new smilies aren’t so much: 😉 looks pouty and unhappy, even at high magnification. I can see the supposed smile and wink, but they look forced. At a more reasonable resolution, ick (not ich).
But, a fig for Newton! Einstein rules; Newton drools!
But then there’s Bohr. *Yawn*.
And I’m totally blasé about Pascal.
Been watching too much PBS Physics: Mystery Out of Matter,
http://video.pbs.org/video/2365543486/
If you’re stranded on the way to the moon, Newton will bring you home! 😉
Strange protruding objects in a pond, particularly if they have relatively no drag, will also get blown by wind…. Otherwise a chunk of driftwood placed at one end of the pond will stay there, but nooooooooo not so much.
I’m loving the dome taxi discussion.
How many clams do you tip a fish taxi driver?
If you get tired of Aquaman, try for the Man from Atlantis. IIRC, this was the title of that 70’s show with the gimmick of a man with gills as we’ll as lungs, and webbed hands and feet. The series was short-lived, and I was a kid, but I liked it.
Or try Flipper, Sandy, Bud, and Pelican Pete.
Or if you’re in the mood for island adventure, with a telepathic cat and a guy with a tuning fork for a sonic screwdriver, plus Ike Eisenmann, there’s always Fantastic Journey. Very short-lived, but I have fond kid memories of that show. Too bad it’s not on DVD or download.