• Welcome to the Speedsolving.com, home of the web's largest puzzle community!
    You are currently viewing our forum as a guest which gives you limited access to join discussions and access our other features.

    Registration is fast, simple and absolutely free so please, join our community of 40,000+ people from around the world today!

    If you are already a member, simply login to hide this message and begin participating in the community!

Trick: swapping 2 edges (only) on a 3x3

aronpm

Member
Joined
Sep 9, 2009
Messages
2,010
If you're asking how it works (that is my assumption because of the :confused: emoticon):

By removing the centre caps you've created a Void Cube, which has a parity case. It's caused by the centres not being in a solvable position.

Here's an example (keep your caps on):
M' (that's the "parity")
U M' U' M (solve DF)
U' M U2 M' (solve DB)
M' U M' U M' U2 M U M U M U2 (flip UF+UB)
U' (AUF)

If you ignore centres (which is the case if you have them removed), you have now swapped UB and UL.

Doing a single quarter slice turn has the following effect: 4-cycle of edges and 4-cycle of centres. Because centres are ignored, this leaves a 4-cycle of edges which is not solvable on a regular 3x3x3.
 

rubiksarlen

Member
Joined
Feb 3, 2011
Messages
563
Location
Malaysia
WCA
2011TANA02
YouTube
Visit Channel
nah i knew the trick already but yeah shouldn't have put that emoticon. but still nice explanation.

that's basically a void cube. Void cubes have a parity where two edges can be swapped and the "invisible" centers are swapped along one axis 90 degrees.

i don't have a void cube, so i thought this was pretty cool. but i'm sure quite some people who don't own a void cube already knows this.
 
Last edited by a moderator:

Stefan

Member
Joined
May 7, 2006
Messages
7,280
WCA
2003POCH01
YouTube
Visit Channel
I don't understand why people keep bringing up centers when talking about a void cube, a cube without centers. Parity is caused by a 4-cycle of edges, plain and simple. Absolutely no need to talk about centers that aren't even there.
 

aronpm

Member
Joined
Sep 9, 2009
Messages
2,010
I don't understand why people keep bringing up centers when talking about a void cube, a cube without centers. Parity is caused by a 4-cycle of edges, plain and simple. Absolutely no need to talk about centers that aren't even there.

Because they are removing and re-applying the centre caps from a 3x3, it's relevant information that "the centres are ignored" or "the centres aren't in a solvable position". When there is an edge parity on this 3x3, the "actual" centre colours are not in a position that is solvable without affecting edges, regardless of the superficial colour put on them by the centre caps.

Of course, if he asked about an actual Void Cube, which doesn't have centres, then mentioning the centres would be irrelevant.
 

Stefan

Member
Joined
May 7, 2006
Messages
7,280
WCA
2003POCH01
YouTube
Visit Channel
To clarify: I wasn't talking about the video (didn't watch it much) but about the posts saying "a Void Cube, which has a parity case. It's caused by the centres not being in a solvable position" and "Void cubes have a parity where two edges can be swapped and the "invisible" centers are swapped along one axis 90 degrees". The latter being *really* bad because even if you do imagine centers there, "swapped along one axis 90 degrees" is just one of several possibilities.
 

aronpm

Member
Joined
Sep 9, 2009
Messages
2,010
I do agree that I worded that poorly. I should have said something like "[..] a Void cube, which has a parity case. On a normal 3x3x3, it's caused by [...]".

It's nice to have people on the forum that correct semantic errors. Too many kids like correcting syntactic errors. (that isn't sarcasm)
 

samehsameh

Member
Joined
Apr 29, 2011
Messages
27
Location
England
youve solved the cross on an adjacent face to what it should be if the centers were in place so youve swapped every edge
 

IanTheCuber

Member
Joined
Oct 28, 2011
Messages
215
Location
In the clouds
WCA
2013SCAH01
YouTube
Visit Channel
We're all correct. Its because you solved the cross on an adjacant face, since it is impossible to cycle the centers in steps of 90 degrees. But you didn't know this, since you didn't know what colors the centers were, because its basically a void cube, with no centers.
 
Top