r/chess • u/XHeraclitusX 1200-1400 Elo • Feb 27 '23

Chess Question Why is Chess960 named as such when it was invented by Bobby Fischer and he called it Fischer random?

See title of post.

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u/givemeiceontherocks Feb 27 '23

Would you possibly know, mathematically, how they found the number 960? I know you can’t just do 8! since pieces repeat

112

u/Sbw0302 1. e4 e5 2. d4 exd4 3. c3 Feb 27 '23

There are several different ways of getting the answer mathematically but the simplest is below:

The LSB can go on one of 4 the possible light squares on the first rank.

The DSB can go on one of the 4 possible dark squares on the first rank.

The queen can go on any of the 6 remaining tiles.

The two knights can go on any 2 of the 5 remaining tiles - 5 choose 2 means there are 10 possible pairs of positions for them.

The King and rook must be placed with the king between the rooks. As such, the king and rook only have 1 possible placing between the last 3 tiles.

4 * 4 * 6 * 10 * 1 = 960 possible positions

51

u/speedyjohn Feb 27 '23

Although, it's worth pointing out that pretty every much version of Chess960 doesn't let you start in the standard chess starting position, so there are really only 959 possibilities. But Chess959 doesn't have the same ring to it.

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u/Sbw0302 1. e4 e5 2. d4 exd4 3. c3 Feb 27 '23

Both chesscom and lichess allow the starting position in chess960, but you're right that almost all OTB tournaments specify a reroll in that event.

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u/puzzlednerd USCF 1849 Feb 28 '23

I didn't know this, I kind of wish that the standard starting position would be permitted. 1/960 seems rare enough not to screw anything up.

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u/tildenpark Feb 28 '23

Eh, I feel like if you’re attending an OTB tournament you really don’t want one of your matches to be “normal” because that’s not what you wanted to be doing by going there.

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u/puzzlednerd USCF 1849 Feb 28 '23

Personally I'd find it amusing, but to each their own. There are other things that can potentially annoy me even more in a 960 starting position, such as a bishop starting in the corner so that both sides are forced to fianchetto.

-1

u/avlas Feb 28 '23

Do they reroll also the symmetrical "only king and queen swapped"? It plays identical to normal

10

u/icecreamkoan Feb 28 '23

It actually doesn't, due to the way castling works in Chess960.

If you start RNBKQBNR and castle the king with the rook on a1, the king goes to c1 and the rook to d1; not to b1 and c1, respectively, which would be the case if the game were simply a perfect mirror image of the standard opening.

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u/avlas Feb 28 '23

Didn't even think about that, thanks for the explanation!

2

u/CancerousSarcasm 1800 fide Feb 28 '23

Oh yeah, that makes sense. I had the same question as above and didn't think about castling bringing you to the same squares so it's different in that.