What is a tesseract?

It's also a rather forgettable book by Alex Garland.

Opps I made my e-mail addy into a link!

hypercube

Didn't Madeline L'Engle use them in her books somewhere as a metaphor for creation or something...?

It involves ants, and string.

I read a book called "A Wrinkle in Time" when I was a kid about 11 or 12 that had that word. I forget what it was all about.

That would be L'Engle. ;-) And yeah, it threw me when I first encountered it.

I also thought first of Wrinkle in Time. Wasn't the Tesseract some sort of creature?

the tesseract in Wrinkle in Time is how they teleport across the universe by bending space/time. But I'm wondering if it has some more scientific basis.I always thought the fourth dimension was time. I knwo the fifth dimension did "Up , UP and AWAY"

They also did "Stoned Soul Picnic". But Laura Nyro wrote it.

It's a fourth dimensional cube. I was going insane one morning, brushing my teeth trying to remember what the name of a fourth dimensional cube was, and I ran downstairs and asked everyone in the house, and they all laughed at me for this saying "Kate is the only person we know who would think about trans-dimensional geometry while brushing her teeth..." but none of THEM knew, the bastards. So I phoned my brother and he immediately knew. So there.

but a cube is 3 dimension al by definition. Isnt it? I dont understand the fourth dimension. Are math tricks involved?

Tesseract = fourth dimensional cube : cube = third dimensional square.

Geddit?

Well, if it was four dimensional it wouldn't be a cube, it would be a tesseract, I guess?

I remember it from A Wrinkle In Time but I always thought L'Engle made it up.

but I thought the fourth dimension was Time? WOuldnt a fourth dimesnional cube just be a cube that is there for a while?

Time is funny coz it is nonreversible in practice (due to entropy) & coz human perception an only see it for a moment. Watching an object pass through our 3-d plane on the 4d axis would make it appear as though the object were transforming over the course of time, "morphing" as it were. Imagine passing a sphere thru a 2d plane and how to a 2d person it would look like a circle getting bigger & bigger then smaller and smaller.

actually I have been thinking. Perhaps the reason we only see fragments of time , like frames in a movie film strip, is because we are constantly in motion in life due to Universe expansion, and perhaps if we coul din some way be totally still we would actually see all of time at once

shurely as our creator and omnipresent ruler you could do this dead easily.

i was thinking it was like a fjord, don't know why

http://adbusters.org/spoofads/fashion/nike/ad.jpg

Square = 2d version of shape with square face
Cube = 3d version of shape with square faces
Tesseract = 4d version of shape with square faces (perhaps cube faces would be more apt, but anyway, hypercube is to cube as cube is to square)

You can make a 2d "net" of a cube out of squares:

       _

   _ _|_|_ 

  |_|_|_|_|  <-- cut out, fold and stick together to form cube

      |_|            (imagine sides are square, obviously)

and in theory you can make a net for a tesseract out of cubes, though my head begins to hurt at this point, so I don't know what it looks like or how it fits together, and you can't actually fold it, you can just stare at it and ponder how it would have to fold.

Time is sometimes thought of as *a* fourth dimension. It's not the only possible interpretation of "fourth dimension". However, because our brains are better at coping with visualising things changing over time than they are at picturing other ways of thinking of extra dimensions, the easiest way to model 4D objects is to think of it as time and show 3D cross-sections changing over time, or rather due to primitive early-C21st rendering technology (no holo-vids yet! *sigh*) as 2D perspective representations of 3D cross-sections of a 4D object with changes over time representing movement along the fourth axis (k- blimey, etc).

Akshly I don't know what I'm talking about. At all. Sorry. I expect some of the maths degree posse will come and rip this to pieces soon. My maths tutor at uni had done loads of work on 27.4-dimensional manifolds or something, oo my head, and he tried to explain it to us in a first-year tutorial once, oooo our heads, just before first-year exams when we'd finished the actual syllabus, oooooo growing sense of panic at the thought that maybe we were meant to know this for exams vudge welcome, eek. But his webpage explaining this stuff in "layman's terms" (= still more complicated than my 60% of the easiest year of degree-level maths allows me to comprehend) does have the ace pun "Euclidean geometry went out with the arc", so I will forgive. Arf!

Best short trashy sci-fi story about tesseracts = Robert A Heinlein, "And He Built A Crooked House". I imagine you can guess the plot, really.

He builds a straight house but knocks it sideways well having sex with the red headed earthling and uses its crookedness to defended from the Mars humans who are annexing his corner of the moon of Jupiter?

I think of time as a fourth axis that all 3d objects stretch out on. I often try to imagine putting all the frames of a film strip together and shining a strong bulb thru it all so you could see all of a time at once

it's this thing

Arrgh I don't get it, Rebecca, will you come to the pub with me one day and explain it to me with beermats? That's how RickyT tort me about STACKS and I THINK I understand them although quite possibly I don't because MY BRANE HURTS. Is there an Uncle Albert book to explain this? Hmmm, trippetty trap off to Amazong I go!

Carl Sagan did the tesseract thing in Cosmos (and you know how I love Cosmos) - basically, you know how that drawing of two squares connected by diagonal lines represents a 3D cube in 2D, that in the 3rd D, all angles would be right angles. Well, he had this model of two cubes inside one another, connected by diagonal lines, which was a 3D shadow of a tesseract, and a tesseract would have all right angles again. Oooooohhhh... my dad used to tell me bedtime stories about this sort of stuff, Mr. Line and Mr. Point and Mr. Square all living on The Plane and how one day Mr. Cube came along and played magic tricks on them.

Robert A Heinlein = published by the NEW ENGLISH LIBRARY!!!! This is more than enough recommendation for me. Amazong is not haffing his books but I AM SO ordering one of the other ones heh heh heh.

Carl Sagan rules. Recently made a song about him.

Sarah, why is being published by NEL a particular reccomendation for you? 'Cos they also published the Richard Allen 'Skinhead' novs?

Going to pub = excellent idea, except I'm currently too poor to go anywhere with pubs not full of very scary people who'd like to kill me, hence another exciting Friday night spent at home staring at the computer. However, I don't think I could explain it with beermats. I'm not sure I could explain it at all in person. The internet makes trying to sound like you understand things you don't understand far easier, though I suppose alcohol might also help. And most of the London ILE people know far more about these bizarre mathsy physicsy concepts than I do anyway. Perhaps they will explain it with beermats.

Stories about lines and points and squares living on the plane and meeting Mr Cube or passing spheres through 2d planes are quite possibly taken from or based on Flatland: a Romance of Many Dimensions by Edwin Abbott, which you can read online now because it was written in 1884 and is now copyright-expired. You can also read Heinlein's And He Built A Crooked House online. Whee. Those should waste a few hours at work. And afterwards you will know as much about tesseracts as I know.

Blimey, I'd forgotten about the Uncle Albert books, I have one of those. What are stacks, are we talking about push-y pop-y computer data structure stacks? Can I be taught how to understand compiler design and distributed systems using beermats? Please?

Duh!! Ignore that above link. Instead, go here.

bluffin

RickyT says yes, those are the stacks. The fact that I was not quite sure indicates I haf a little way to go in my quest for KNOLEDGE. COme to the pub Rebecca!

Oh sorry, I didn't see that above. I used to have a friend who obsessed over New English Library tat and whilst living in Kingston found a charity shop with a HUGE NEL stock languishing on the bookshelves. They all tended to be hilarious slices of trash and only 10p each! I really should look up more about them but the fact remains if I see the NEL logo I know it should be... "interesting"...

"COme to the pub Rebecca!"

That sounds like an order to me. So, are you going to December Sussed and the hour or two beforehand? I might actually be there for once. Unless anyone else doesn't want me there, obviously.

I will probably not explain n-dimensional geometry with beermats, but I have found my NES and can bring it along for you and Alan to fight over, heh heh heh. Although I can't find the cable thing to connect it to the TV. I'm not sure if you need a special cable, either you do or I'm being really dense. Hrm. And there aren't any game cartridges, either - I have a vague memory that there's a built-in game which will run without one but I don't know since I don't have the cable.

What was the other console both of you wanted, was it a Megadrive? I'll have a look to see if I can find my Megadrive too so you can both take a console home; I don't like the idea of having to choose who gets the NES. But I've now found my big bag of retro console gubbins and it wasn't in there so I have absolutely no idea what I've done with it, so I might not find it.

Problem with December Sussed is that it clashes with the Strange Fruit with CHRYS LYNYRD, TP and those Camera Obscura chancers. Let's face it, I could give no shits at ALL re: Camera Obscura although this is probably a personal matter related to my bearing grudges about bands I've barely heard (they were shit at last SF though) but Mistopher Chris at least is U&K as he do not come to that London very often. TP I could catch another time I supose but hrmph stomp change the date of Sussed! It is the 5th, right?