Prime Eval, Part 10 – Space

Rambling time.
I still see comments from people on the net that claim that no matter what anyone else says, Pluto is a planet. To them, anyway. Generally, these people aren’t scientists, and their opinions don’t really affect anything else. But, those opinions remain unshaken, in any event.

This brings me back to language coloring perception. We hear the word “planet” and that brings certain images to mind, such as photos of Earth, Mars or Mercury. But, the classification “planet” was originally kind of a dumping ground for any celestial phenomena that wasn’t initially recognized as being something else. That is, “planet” as a definition for a specific kind of thing hasn’t ever really been all that clear.

In science, you want to know what makes two things similar, and what differentiates them from each other. If I give you two perch, you may look at them and say, “they’re the same kind of fish, they’re both perch”. Looking closer, you may notice that one is male and the other is female. Or, if I give you one perch and one trout, you’ll still say they’re both fish, but they’re not the same kind of fish. Why is it important that they aren’t the same kind? Or rather, why is it important that they should be the same kind? Because having two fish that are capable of breeding with each other gives you more fish. Why is it important that we know that there is a similarity? Because if they’re fish, and you’re holding them in your hands, regardless of whether they’re perch or trout, they’re both either dying as we speak, or already dead. Classifying the two things under the same heading (“fish”) and then further classifying them under separate headings (“perch” and “trout”, “male” and “female”) is relevant to our understanding of them.

Look at the night sky. We have small, dirty snow balls, small iron pellets or rocks, larger rocks with iron or nickel cores, big rocks made up of various materials, gas balls, liquid balls, balls of incandescent plasma, balls of compressed matter, dust, radiation, and photons and other subatomic particles. Some of these things are easier to differentiate than others. Big balls of incandescent plasma are not like small dirty snowballs. So, it makes sense to create a classification “star” for plasmatic kinds of critters. And, within this group you have properties that include age, ingredients, mass and best use by date. So, knowing how young, hot, massive or complex the star is can help you figure out other things like how far away it is, what direction it’s traveling, how long it’s been traveling, and what kind of things are surrounding it.

So, let’s jump to the next point. Stars can have accretion disks, that is, dust and gas that surrounds the star. Over time, the dust in the disk is going to clump and form rocks, or ice and dirt balls. What are the differentiators here? Comets have eccentric orbits, they’re not very dense, and they can have tails formed when the ice or dust melts or is blown off by the force of the stellar wind of that star. Asteroids are large solid rocks or metallic clumps. They can be very small, or up to several miles across. So, yes, comets aren’t asteroids and there’s a reason for identifying them as such.

If the clumping gets serious enough, the object can develop sufficient mass to have its own gravity. As the pull of the object’s gravity increases, it attracts other neighboring clumps that smash into it. So, at some point an asteroid can become a planet. And this is where the current classification “planet” breaks down. Mercury is only slighter larger than the Moon, while Neptune is a gas giant 17 times more massive than Earth. Neither Mercury nor the Moon have atmospheres, while Neptune and the Earth do. Earth can support life, as may Saturn’s moon, Enceladus. While the Earth, Mercury and Neptune orbit around the Sun, the Moon orbits around Earth, and Enceladus orbits around Saturn.

Which of these differences are significant enough to justify separate classifications? Obviously, a rock that orbits around another rock can affect the tides between the combined pair, and the smaller rock, if it orbits fast enough, can act like a broom to sweep out all the other rocks to protect its bigger sibling. So in this sense, the classification “moon” is justifiable. But still, “planet”? Just exactly WHAT is so important about a planet that we don’t just call it a “class XX asteroid”?

Atmosphere isn’t important because not all planets have one. Water isn’t important for the same reason. Mass? Mercury, Pluto, Ceres and the Moon are almost indistinguishable on that count. The potential for harboring life? That just gives us Earth, and possibly Mars or Enceladus (two planets and a moon).

What exactly do we want out of our planets that makes them not moons, not asteroids, and not comets? The International Astronomical Union came up with the following definition:

A planet:
1) is in orbit around the [its] Sun,
2) has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3) has “cleared the neighborhood” around its orbit.

So, what’s somehow important here is that the planet has to be mostly round, has to orbit its star, and can’t be a part of a “belt”. Which means, you can have things that are round and don’t orbit the sun (moons, rogue planets); that orbit the sun and aren’t round (comets, asteroids); or, that orbit the sun, are round, but are part of a belt (dwarf planets).

Is this classification system justified? Do “planets” do something special that we really care about? Or, is there something that we really do care about that is getting ignored in emotional baggage? Giant planets are good for determining if distant stars have planets, based on gravitational pulls or light dimming (as the planet crosses in front of the star). And yes, we can assume that “goldilocks planets” (which are going to be smaller than giants and less likely to be detectable from a distance) support alien life. But, things like Mercury, Pluto or Ceres don’t provide these kinds of benefits, just because they’re round and orbit a plasma ball. Personally, I don’t see the classifications “planet” and “dwarf planet” performing significant functions as-is. It might be better if we stepped back and tried looking again to see if we have a trout and a perch, or just a trout and one really ugly trout.


Soccer Ball 3D Puzzle

When I was in Thailand recently, I found a table in the Night Bazaar in Chiang Mai that carried a large number of 3D wood puzzles and brain teasers. The prices were all ridiculously low ($1.50-$4 USD range), and I had a lot of trouble deciding which ones to get. I should have gone with the 4-puzzle box set, but I preferred the design and quality of Soccer Ball and Dinosaur Egg (I didn’t keep the packaging or assembly instructions because they were just cheap xerox copies and I didn’t need them, so I don’t have the contact information or Thai names for these puzzles. I’m using the names I got from a yahoo image search.) I love 3D wood puzzles, so I’m going to talk about them in this blog.

First, Soccer Ball. This puzzle is very similar to a cube puzzle I used to have, which was one reason for getting it. It’s incredibly simple to take apart and reassemble if you do enough 3D puzzles. The first step is to locate the locking piece and push or pull it out. The puzzle pretty much falls apart by itself.

Sort the pieces by type. This will give you the one locking piece, 3 wedges with two notches, and 2 wedges with three notches.

Take the three two-notch pieces and fit them as shown in the photos.

Take one of the three-notch pieces and lead with the inner edge to fit it on one side of the assembly, with the middle notch pointing up.

(Three-notch piece, with the third notch facing up and the “M” edge facing to the right. You want to insert this piece into one of the notches of the puzzle assembly so that you’re leading with the “v” at the bottom of the “M”. This just makes putting the piece into place easier.)

(This is what the assembly will look like when the three-notch piece is put in place.)

Do the same thing with the second three-notch piece, leading with the inner edge on the other side of the assembly. This should give you 80% of the ball shape and you should be able to see the square hole the locking piece fits into.

The last step is to put the locking piece back. The only trick here may be in getting the other pieces settled into place so that the square hole is large enough for the locking piece to slide into easily. If you have to force the locking piece, then try disassembling the puzzle and rearrange the 3 two-notch pieces to get a larger square hole at the end. If I’m not trying to break speed records, I can still take this one apart and put it back together again within a minute if the locking piece jams. Reassembly time is usually about 30 seconds. I bought it in Thailand for about $1.50 USD.

Sakura Papercraft

A few weeks ago, I wrote about going to a Home and Energy Saving fair, where an architect had laser-cut sheets of wood for putting together a pencil holder in the shape of a house. He also gave me sheets of papercrafts for the local Kagoshima mascots, Guree-bu and Sakura. Sakura is pre-cut, Guree-bu isn’t. So, when I finally had a few free hours with nothing scheduled, I sat down to make Sakura. The sheet is printed on A4 paper. The paper between the cuts was just thick enough that I decided to take the pieces out by using a cutter knife rather than just punching them free. So that took about an hour total. Plus I was using envelope glue, instead of white wood glue, so the glue was taking longer than normal to bond the pieces of paper together. I think the gluing part took 2.5-3 hours. It wasn’t a particularly difficult project, just a bit fiddly.

The finished piece is about 5 inches tall, and 4 inches wide, including the flower whiskers.

I may tackle Guree-bu in the next few weeks, but I have to cut all the pieces out with a scissors or cutter knife, and that’s going to take a lot longer…

Prime Eval, Part 9 – Artificial Gravity

I was reading a manga adaptation of J.P. Hogan’s Inherit the Stars, and the above image got me to thinking. In the story, humans are just taking their first steps towards interplanetary travel, and their ships use rotating compartments for centrifugal force to simulate gravity. The Giants that they encounter have fully working artificial gravity systems. And that’s what I was thinking about. Gravity is the result of mass. It’s not a field (like a magnetic or electric field), so you really can’t have “gravity field generators” (unless I’m wrong).

How would an artificial gravity generator work? Effectively, if you want 1 Earth g in your ship, you need to have the equivalent mass beneath your feet. You can get that mass by compressing matter, as with micro black holes. They will be really hard to move, and you’re going to be expending all your fuel to push the compressed mass through space, but they will work. You won’t be able to turn them on and off as you can in cartoons – once you have the equivalent mass, you’re not going to want to let it uncompress unless you aren’t interested in keeping your ship any more. And you’re not going to be able to quickly change the pull of gravity to reorient it so up is down, etc. Not unless you can move the compressed mass freely around the ship, which may do some interesting things to space-time if you try to warp it too much…

Again, because gravity is not a field, it’s not going to stop at the edge of your ship, and this is where things get fun. You’re going to be pushing a space-time warper through space wherever you go. Which means that you’re going to be attracting matter that gets within your gravity well. Just think what happens when you go through an asteroid belt, and your ship has the equivalent of 1 Earth g extending out past the ship’s hull for 1-2 miles. The above craters in the ship? Yeah, self-inflicted. But, I’d expect that the material from the disintegrated asteroids would stay within the gravity well around the ship and start caking up. Of course, you can claim to have a force field or electromagnetic barrier around the ship to protect against physical collisions, but unless the barrier completely destroys matter, your barrier field is going to cake up instead.

In short, true artificial gravity in space ships may be unattainable, and certainly will require heavier plating to protect the ship from incoming rocks. At least, until we figure out how to make those “force fields”…


Tornado Humidifier Kit review

(All rights belong to their owners. Images used here for review purposes only.)

Well, the Gakken editors have admitted that they took too long to come out with this issue. They didn’t specifically say what the delay was, but they kind of implied that there was a quality issue with the kit. It probably also allowed them to put in more time on the magazine, too, because it looks really good. Anyway, the magazine starts out with “Uzu” (spirals), a photo essay of spiraling air flow patterns, some of which are very complex and fractal-looking. This includes spirals in clouds, on the face of Jupiter, and from distant stars. There’s an 8-page explanation of how tornadoes are formed, with examples from the Gakken kit, and the indoor tornado generator at the Mercedes-Benz museum in Stuttgart, Germany.

There’s an explanation for how the kit works, plus the suggested mods – adding a little spinner to spin within the tornado; creating an Arduino bluetooth interface to a PC to control the mist and push it through a tube as a “beauty aid”; putting it on a penguin robot base to have a walking humidifier monster; and adding a photocell and Arduino control to have the LED light show activate when the room goes dark. There’s an interview with one woman on a project to translate 11 of the Gakken kits to Chinese; an article on the U.S.-Taiwan Formosat-3 meteorological satellite constellation; an explanation for how auroras happen; and a 6-page piece on Canadian tornado hunter, Greg Johnson. There’s 5 pages on the dangers of dry air (dried skin, build-up of viruses that cause the flu) and promotion of the use of room humidifiers (but which ignores the build-up of mold due to excessive humidity…); the instructions for building the kit; and the 16-page manga from Yoshitoo Asari on what 3-D printers are and how they work. The magazine ends with an ad for the Knitting Loom kit, and promise of the next Adult Science kit some time in 2016 – the Kaedadrone. Everything is in Japanese, as per SOP.

Just as an aside, the bits on health and beauty play into Gakken’s recent foray into skin care magazines and creams for aging women.

(The full set of pieces.)

Ok, for the kit itself. There are 31 pieces, plus another 19 screws, and a total 60 minute suggested assembly time. I took a little under 2 hours because I was also editing videos, helping with a computer manual translation, and doing the dishes during all this. Assembly is pretty straight-forward, and there’s really only one or two tricky points that may get you if you can’t read Japanese.

(The pieces for making the mesh cone.)

This is the first tricky point. You need to make the cone mesh. Take the mesh material, the cone and the locking collar. Put the mesh over the collar and press the collar into place inside the cone. Make sure the mesh is smooth, and not floppy in the middle.

(The finished cone. The pieces just press-fit together.)

Like this. It’s not that hard to do, but it may be a bit difficult to figure out just by looking at the figures in the magazine.

(The cone, the mist generator, the LED cover and the main base.)

The next step is to put together the major assemblies. In effect, you’re going to have the top and bottom sections of the cylinder, which are separated by a single sheet of rolled plastic. The base is where the secrets lie. The piece in the lower right corner of the above photo is the water tray. It’s also the holder for the main circuit board (which goes underneath). The piece at the top right contains a transducer (shown below), which pushes a felt cylinder (shown above) that is sitting in the water tray. The transducer vibrates at ultrasonic frequencies to produce the mist. The mist gets diffused by the mesh cone, and then rises into the bottom of the main cylinder.

(And the reverse sides.)

The base (left, in the below photo) has both the power switch and a volume control. The volume control changes the speed of a very small fan for less or more airflow up to the top of the cylinder, and the strength of the transducer for producing less or more mist. The top piece contains the fan blade assembly and an exit path for the mist to leave the cylinder and fill up your room. It also has the tri-color LED for illuminating the tornado from above.

(The partially-assembled base and top cover. Notice the power switch and volume control at the bottom side of the base unit to the left. These have to be inserted before putting the other pieces into place.)

I’m not really clear what the purpose is of the two pieces of cardboard coming from the transducer head (in the upper photo, bottom left assembly), other than to act as shim in holding the transducer while minimizing vibrations in the kit as a whole. Personally, I think the pieces should be shortened to maybe a third the length.

(The base, with the mister mesh cone in place, and the fully assembled top unit.)

(The fully assembled kit. The second “tricky” point is that you need to put the plastic cylinder in place so that the slots in the cylinder are down next to the two white paddles in the base unit. If you want to further hide the wires, you can cut a strip of paper out of the magazine (bottom of page 61) and slide it into the support spine.)

The wires run from the base to the top within the support spine at the left side of the cylinder. And, the cylinder rotates to reveal the water reservoir. You need to keep the reservoir mostly full, which is maybe an 1/8th of a cup of water. There’s a little plastic “L” flange inside that marks how much water you need in the reservoir (not too little or too much). The reservoir will probably go empty after about 15 minutes. The unit runs on USB power from any PC or laptop, and a 1 meter cable is supplied with the kit. Rotate the cylinder back into place before turning the kit on. All the USB cable does is to provide unit power – there’s no other USB communications between the PC and the kit, and the kit doesn’t come with a battery holder.

There’s a little lever in the base that lets you rotate the cylinder so that the slots at the bottom of the plastic are at one side of the little white paddles, or the other. You want to position the slots so they’re just partially blocked by the paddles in order to generate spin in the airflow into the cylinder (you can rotate the lever to make the tornado spin clockwise or counterclockwise). So far, the “tornado” isn’t that visible in my kit, even with “volume” turned all the way up, and the slots partly not blocked by the paddles. Either put a black background behind the kit, or turn the lights off. If you push the power button once, you get a single color from the LED. If you push a second time, you get color cycling, as with the origami lamp and aurora kits. Purple seems to be the color that makes the tornado stand out the best. Red is the worst.

Overall, this is a nice nightlight, but you’re going to want to put a timer on the power cable to automatically turn it off before the reservoir goes dry, or you may damage the felt piece attached to the transducer. It’s a big kit, at about 24 cm tall, and 9 cm in diameter at the base. Most of the pieces are very sturdy, not including the thin plastic sheet. There were no missing pieces, and the only “leftovers” consisted of the cardboard sheet used for shim for the transducer, and that could be purposed as a spinner inside the tornado chamber. I’m going to keep messing with it to see if I can make the airflow stronger to make a more visible tornado. Then again, my apartment is normally at 60-70% humidity, and in the winter we have heavy condensation all around the windows and frames that we have to remove with towels. The last thing I need here is something that intentionally INCREASES the room humidity…

Next up: The Kaededrone
No details given.
Scheduled for some time in 2016.
This is a small, lightweight 2-bladed remote controlled drone based on an insect wing for the main body shape. I can’t tell what the size will be from the photo.

Prime Eval, Part 8

When I took physics classes back in university in the early 80’s, my professors taught that photons were waves that act like particles, and electrons are particles that act like waves. The examples included scattering, interference patterns, etc. However, in QED, Richard Feynman came straight out and stated that photons are particles. Which is interesting to me, because QED hit print in ’85, and was based on stuff he’d been lecturing on for years. Presumably, my teachers should have had access to the same information Feynman had, and I would have been happier if they’d taught what he taught. Anyway, Feynman photons are particles, not waves.

The book QED presents a very simplified representation of the Feynman diagram.

Basically, an electron travels and at some point emits a photon which is then absorbed by another electron, or breaks down into a quark-antiquark pair. The Feynman diagram isn’t predictive – it doesn’t try to explain why electrons and photons behave in this way – it just uses probabilities integrated over a surface or volume to develop the math for what we observe matter doing in space-time. Then there’s the little problem of two neighboring electrons, where one absorbs the photon before the other one emits it…

To me, it’s almost like electrons and subatomic particles are bouncing around the boundaries of 4-D space, and occasionally making one right-angle turn too many before coming back to our 3-D reference frame. Maybe we could say that this behavior is what you get when you’re really close to the origin of the x-y-z axis and you keep dividing by 0 somewhere. This is all pointless speculation, but it could hint at the shape of 4-D space if we could build up enough cross-sections of the 3-D space around a specific particle.

One other interesting thing about the book QED is that it puts a different light on the Schrodinger’s Cat experiment. The Feynman Diagram represents a probability of an event. Different particles have different probabilities, and all possibilities can and will happen. But, some of them cancel each other out and what you have left is a group of particles doing something together on a macro scale, or one particle apparently doing two things at the same time when you try to measure it. I’ve always thought that the “probability” part came from not being able to predict the future, as when you roll a ball on a roulette wheel. There’s a probability that the ball will land on any given number, but the actual number can’t be known until the ball stops rolling. But, in Feynman’s view, each particle has an event probability that is based on time and/or distance traveled from a point source. We can’t know what the particle will do at any given moment until it actually does it. Bottom line is, what most people think they understand about Schrodinger’s Cat is wrong.

Funny enough, the inaugural volume of Motohiro’s manga Q.E.D. iff (2015) does get into something of a discussion of these exact same concepts, and goes into a short explanation of negative probabilities. Although the manga is still only in Japanese, I do recommend both the Feynman QED book and Q.E.D. iff for anyone that wants to learn more.

House and Energy Fair Papercrafts

(Gundam, to the right.)

There was a Home and Energy Saving fest on Oct. 25th, at the Volunteer Center.

One booth was part of the display by a local Kagoshima architect, and consisted of a number of really good papercrafts. The designs all came from the Yamaha site, the architect just printed them out and built them. Having made the Himeji Castle papercraft myself, I think I have a good idea of just how much work went into all of these projects here…

(The One Piece ships, plus Space Battleship Yamato.)

(Goku, Frozen, Pokemon, Miku Hatsune, and random animals.)

(Tigger and a really nice blaster.)

These building card cutouts were probably based on the architect’s own designs. He uses something similar for his business cards.

Gundam, from the back.

Next door, the same guy had a workspace for people that wanted to make things themselves. I asked if he’d let me make something, and his assistant pulled out two sheets of laser-cut wood, asking if I wanted the piggy bank house or the pencil holder house. I chose the pencil holder because I don’t have anything to put into a piggy bank. I was told that I had 30 minutes, which I thought meant that they’d be closing up at 3:30 or 4 PM. So, I sat down and started punching pieces out of the wood. Initially they said that I wouldn’t need glue to hold the pieces together (which was true for the walls and roof) but I did have to glue on the window and door frames. The edges where the laser burned the wood were very ashy, and that covered my hands and stained one side of the wooden pieces. I ended up flipping the pieces to be “wrong-side out” because that side wasn’t getting stained. Fortunately, they had lots of wet wipes, which I needed constantly. I think it actually took an hour to finish everything, and that was with the architect sanding down the locking pegs for me because he’d discovered that he’d designed the matching holes to be a little too small. The finished pencil holder is about 6″ cubed.

Very nice for something that was free.

He also let me have papercraft sheets for the local advertising mascots, Gree-bu and Sakura. Sakura is pre-cut, Gree-bu isn’t.

(Greebu papercraft sheet)

(Sakura papercraft sheet)


Otona no Kagaku newsletter #164

Finally received the latest newsletter in email. The editors start out by stating that it has been a long time since the last kit came out, and that they’d gotten a LOT of inquiries from fans asking what’s going on. They add that they’re pretty confident that this kit is going to hold up under the scrutiny after such an extended wait. It’s going to be the “Tornado kit”, also known as the “Tatsumaki Hassei Souchi” = Hurricane Springing Forth Device”, with a release date of Nov. 12. The editors would be very happy if you put in a pre-order.

1) Tornado Kit Out After 1 Year Wait
There’s a fairly extensive description of both the kit and the magazine. On the kit side, it’s basically a mister-style room humidifier. Blowers at the bottom of the main chamber push in a fine mist and create a visible vortex within the chamber. A tri-color LED provides a changing light show, and the unit has an USB jack for power if you want to plug it into a PC for table-top operations. It also has an auto-off timer if you want to use that. The magazine is A4-sized, 84 pages, and has photos of various air flow patterns, the science of hurricanes, pictures of auroras, and an article on tornado hunters. The online instructions show 40+ parts (including screws and springs) and a suggested 60 minute assembly time. 3,500 yen, not including tax. Hitting stores Nov. 12 (it will get to where I am in Kyushu 3 days later.

2) Knitting is Popular in America
The editors talk about how knitting is popular world-wide, and then segue into the release of a new book – “Knitting Loom”, with the “Knitting Loom Starter Kit”. 2,100 yen. Nov. 17th release date. No photos or on-line pre-ordering links.

3) Rainbow Loom Starter DVD Book
Gakken has decided to release a DVD and book combo for showing beginners how to make various items with the Rainbow Loom. B5-sized book, 84 pages, plus the DVD. 1,300 yen not including tax. Released on Oct. 13.

Prime Eval, Part 7

There was an illustrated book that I encountered in a bookstore in Saint Anthony Main in Minnesota in the mid-1980’s that told the story of a two-dimensional character that lived in, and explored a “flatland”. I can’t remember the title, and I’m having trouble tracking it down. It’s not Edwin Abbott’s Flatland (1880), but was probably inspired by it. The book I’m remembering had stick figures, while Abbott used multi-sided polygons, and there was some discussion of how the internal organs of the characters were designed with interlocking valves that would keep people from splitting into pieces while still allowing them to eat and digest food. Occasionally, there’d be rain storms, which would drown anyone silly enough to live underground, because water had no place to go except sideways or down; and when two people encountered each other when traveling opposite directions, one of them would have to climb over the other in order for them to get past each other.

I haven’t read Abbott’s Flatland, but according to the wiki, the first half discusses the mechanics of the 2D world, while the second half is a parody of Victorian society. However, looking at the website for the CG animated movie based on the book, it does raise some interesting questions. First and foremost would be, “do you need gravity?” In the movie, the characters move around like blood cells on a slide under a microscope. There’s no blatantly obvious form of locomotion. Instead, everyone just spins, or advances in a kind of ineffectual-looking rocking motion. We see the polygons face-on, and there is no real “up” or “down”. In the book I’d read, (I’ll call it “Stickland” for now) all the characters are stick figures, and there is a definite “up” and “down”, with “gravity” holding everyone to the ground line.

Both approaches exhibit a bias inherent to 3D creatures. With Stickland, we have gravity without a system representing mass, while in Flatland we have movement without friction (that is, the characters aren’t pushing off against a surface in order to propel themselves forward). In effect, the Flatland characters should be stuck in place, spinning helplessly in circles like an astronaut without a jetpack. Granted, both works are fiction and not intended to be questioned too closely. But still, the questions are there.

“Do you need gravity?” How would you move around in a 2D space? Stick figures on a cross sectional landscape have the obvious advantage of being able to move by pushing their feet against the ground line, assuming that their legs don’t cross. But this means that being bipedal is an evolutionary dead end. It’d be better if they were more amoeba-like, or had more of a rolling motion. On the other hand, being polygonal lets you move left-right and back-forth, giving you the ability to sidestep obstacles. If only there were something to push off of for propulsion (i.e. – the “ground” “under” you), or if there was some way to differentiate between movable and non-movable objects. Again, a more amoeba-like shape gives rise to something like a squid or octopus, which could move using a kind of air-jet.

All of this speculation is silly, because there’s no option for food, or other energy intake, and being 2-dimensional none of the creatures would be able to “see” (sense) each other, since they’d just appear as infinitely thin line segments edge-on. But there is one other aspect that is related to the previous post regarding cross sections, and that is, with an upright, stick figure-style world, the landscape could be in the shape of a big circle and the inhabitants would never be able to tell. If there’s a “sun” in the middle of the circle, the light would obscure the opposite side if you looked “forward and up”. Otherwise, the “ground” would be between you and the sun and the universe would appear black. If the “ground” is mostly flat with some hills and valleys, this would raise a different philosophical question. Which is, How could you tell if the world is a long, fluctuating line, and not a 3D plane that slides sideways as you “pretend” to walk forward and backward? That is, is movement illusionary and you’re actually traversing a 3D map whose cross section (the value of y) changes as x changes? The answer is, you wouldn’t be able to tell.

So, how would that translate for a 3-dimensional character within a 4D space?