4D machines

Ideas about how a world with more than three spatial dimensions would work - what laws of physics would be needed, how things would be built, how people would do things and so on.

4D machines

Postby PWrong » Mon May 31, 2004 9:51 am

What sorts of machines are possible in the fourth dimension? This might have been discussed before I joined, I can't remember if I read all the posts or not.

I think there must be hundreds of possibilities for 4D machines, with all the different wheels and cogs available (spherindrical, cubindrical, duocylindrical).

A first step might be to imagine an ordinary 3D machine stuck to a 3D wall. Then we can add little 4D components to accomplish things we couldn't ordinarily do.

Or, for a different approach... has anyone thought of 4D Lego? :lol:
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Postby Geosphere » Tue Jun 01, 2004 2:35 pm

Hmmm. 4D lego - blocks that could fit 'within' each other?
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Postby pat » Tue Jun 01, 2004 6:58 pm

Geosphere wrote:Hmmm. 4D lego - blocks that could fit 'within' each other?


Nope... they'd still be 'on top' for sufficiently broad definitions of 'on top'.
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Postby elpenmaster » Fri Jun 04, 2004 6:32 am

4d legos. . . .

sounds fascinating. is there any way that someone could create a computer program to mimic 4d legos? they could create things and then show the creation from different perspectives. . ..
:twisted: :?
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Postby Euclid » Sat Jun 05, 2004 1:00 am

elpenmaster wrote:4d legos. . . .

sounds fascinating. is there any way that someone could create a computer program to mimic 4d legos? they could create things and then show the creation from different perspectives. . ..
:twisted: :?


Take a 4-D object, like a Klein bottle, and use it as a construction primitive. Would be interesting to see what the projections look like.
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Postby PWrong » Sun Jun 06, 2004 6:32 am

The basic Lego brick is a 2*1*1 block. That's so they can fit together like bricks and make a tall, long but thin wall (not infinitely thin, just the width of a single block). A Lego wall in tetraspace would be tall, long, and wide, but "tarrow". So to find the basic TetraLego block, we need to find the most efficient 3D lego block to build a solid cube with, then "extrude" it into 4D. I think we're probably looking for either a 2*1*1*1 or 2*2*1*1 tetra-rectangular-prism. (for want of a better word)

Another important question is what shape to use to fit them together? Lego blocks have little cylinders on the top, and cylindrical holes underneath. Which of the three cylinder-like tetra-objects would be preferable for TetraLego?
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Postby Euclid » Wed Jun 09, 2004 4:03 pm

PWrong wrote:So to find the basic TetraLego block, we need to find the most efficient 3D lego block to build a solid cube with, then "extrude" it into 4D.


Can you elaborate on the above? It really makes no sense to me.

A cube (in three space) becomes a hypercube in four space. Are you trying to describe a hyperrectangle?
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Postby Keiji » Sat Jun 12, 2004 9:23 pm

is there any way that someone could create a computer program to mimic 4d legos? they could create things and then show the creation from different perspectives. . ..


I was thinking about that before in fact. Have internally a 4-dimension array of boolean values, each one having 0 = not occupied, 1 = occupied.
Let the program fill this array with values calculated from a net (this is a data type I "invented" after thinking hard about how to represent shapes higher than 2 dimensions).
Once the array is filled, pick 4 directions and an origin. (To draw 3D objects, you need 3 axes which are at 3 different angles. To draw 4D you therefore need 4 different angles.) The program will then fill any occupied item in the array, after calculating what space on the screen it uses, in black, leaving empty spaces as they were. That should give you a basic representation. To see it clearer, you could have the program draw in wireframes rather than block filling areas.

As for 4D lego, I would say that it would be rather similar to our existing ones, just extruded to 1 or 2 studs in tridth/trength (I usually use tridth). This is because the lego pieces could be rotated around so they wouldn't need any "abnormal" pieces. However, there is one thing that comes to mind in Technic - there would be many different types of Technic pieces due to the fact that there are 3 possible different orientations of axial pieces; cubindical, duocylindrical and spherindrical.

Also, in the 3rd dimension we have 3 main types of gear which are - under my names - parallel, angular and worm. Parallel is where the lines that go through the centres of the gears are parallel, used to convey rotational energy across a plane, or to change the speed and force of said energy. Angular gears are where the gears are not parallel but the gears' centre-lines lie on the same plane, used to change the direction of energy. Worm gears is where the lines are not parallel nor do they lie in the same plane. These have an interesting property which is that the force is magnified greatly - in my lego set by 24 - and speed is reduced by the same multiple.

In the 4th dimension things get complicated. With cubindrically and spherindrically orientated gears we will have 4 types of gear. We still have parallel, angular and worm, but we also have realmar. Parallel and angular remain the same, while the worm's definition changes to being not in the same realm as well as not in the same plane. The realmar gear is a gear where the lines from the centres of the gears are in the same realm but not the same plane. As yet I have no idea whether the realmar gear would behave like an angular or worm gear.

With duocyndrically orientated gears we only have one, like in the second dimension, because the shape of duocylinder leaves only 2 dimensions free. This also means that duocyndrically orientated gears would be large in terms of tetra-volume and would be more costly. The type of gear we have here is one we do not encounter in the 2nd or 3rd dimensions. I will call it a free gear, since like an angular gear it can not only go around the outside of another free gear and rotate around the plane perpendicular to any line constructed between the centres of the two gears, but it can also rotate around the other remaining plane over which rotation is possible. This means that you can use two free gears and two duocyndrically orientated rods to change to any angle possible in tetraspace, whereas in realmspace you may need to use either three angular gears or two worm gears to achieve said effect. The former uses up more space and the latter has a side-effect of dramatically losing speed and gaining force.

Phew, that was a long post. :o
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Postby PWrong » Fri Jun 25, 2004 4:08 am

Wow, complicated :o

I think a 2*2*1*1 shape would be the best choice for building a simple wall in tetraspace.

So how many studs would there be? The studs on 3D lego are cylindrical, so extruded they would be cubindrical. I'm not sure why, but a spherinder seems to be a better choice for fitting into a hole. The hole, of course would be the same shape as the stud. Is there any significant difference?

I don't have a Lego technic set myself, and I don't quite understand what a worm gear is. Could you explain it some other way?

By spherindrically orientated gears, do you mean the gear is a spherinder rather than a cylindrical gear in realmspace? A spherindrical gear would rotate around its single straight axis, but I can't work out how a cubinder would rotate, since it has two straight axis. I tend to think of a cubinder as a bit like a conveyer belt. Is this valid?
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Postby mightymrbob » Fri Jun 25, 2004 7:56 am

I'm not entirely sure, but I think a "worm gear" from a Lego perspective is one that kind of has two connectable "things" on each end that can move either way on the "thing" in the middle...


_____ _____
> \ / )
( O <
_____/ \_____


There's a small chance it may vaguely resemble the "diagram" above.

(The " )" represent the rotation). What I'm trying to explain may well not be a "worm gear", but it is a technic piece! :D [/i]
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Postby Keiji » Sat Jun 26, 2004 10:19 am

From Google Images:

http://www.hafhead.com/lego/mytrain/pdu ... step02.gif

The worm gear is the black thing in the middle.
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