# How many mirrors on a discoball?

Asked by Cooldil17 (485) July 24th, 2009 from iPhone

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Depends…how big is said discoball?

All of them!

ShanEnri (4419)

my guess is… 6 times 10 to the 23rd (avogadro’s number)

Guessing…the same as the number of faces on a geodesic dome.

Jeruba (53074)

777

Zendo (1752)

666 ha

Tink (8673)

Zero. There are no mirrors, the reflections are all in your mind.

Sarcasm (16788)

If we estimate each mirror at 1 cm^2. Surface area of an sphere is 4pi*r^2 in cm^2 (assuming radius in cm). So let’s say we have a 2 foot diameter discoball, which is pretty big (I’m not sure they even come in that size). So radius is one foot, which is (12*2.5=) 30cm.

So there would be about 4*3.14*30*30= 11 304 tiny mirrors.

Now there are slight problems with using the formulas for a smooth surface, but we’re basically doing what video games do by estimating a sphere with polygons. We made one in college. It’s a pain in the butt.

@Tink1113 Great answer dude

Zendo (1752)

@Zendo Thanks :)

Tink (8673)

wow!! @swuesquire
fwiw not much! I was going to guess around 10,000

nebule (16452)

42

It appears that the little mirrors are square. That means that the surface cannot be entirely covered because there must be nonsquare spaces between them in order for squares to cover a rounded surface and form a sphere. If the size of the mirrored tiles is a constant, the number is going to depend entirely on the size of the ball, whether small enough to be a Christmas ornament or large enough to make a ballroom sparkle.

There is evidently a standard size for the mirrored tiles because this one advertises smaller tiles as a selling point.

I’ve made a rough visual count of the top half of one quadrant on the 8” ball at the second link above. The bottom half of the quardant is going to match the top half, and the whole ball woud be four times a single quadrant. There are roughly 100 tiles in that 1/8 area I counted. So that means there are approximately 800 tiles on this small disco ball. If this does indeed feature smaller-than-standard tiles, the number on a regular ball would be lower. I’d say pick an illustration and count.

Jeruba (53074)

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