What would diffraction of a macroscopic object look like? I read an interesting question here in the forum (Will a football (soccer) diffract?) and came up with the following doubt: even though its diffraction angle is too small to be detected, if we had the possibility to detect it, what would the diffraction of a soccer ball through a pair of posts look like? I mean, in the case of electrons, there is a screen in which the diffraction pattern can be appreciated. But what about this case? Would we see lots of soccer balls in different places or what?
 A: Each soccer ball would end up at one place, and the probability of landing in a particular place will be a function of position. Only if you kick many soccer balls would the diffraction pattern emerge. In that sense, it is no different than photon or electron diffraction: the actual pattern on the screen is actually made up of many millions of individual "hits". In fact, people have gone to great lengths to lower the flux of photons / electrons in such experiments to prove that a single photon "interferes with itself".
I wrote an earlier answer that goes into a little more detail. You can consider each dot in that answer "one place where the soccer ball hits", but recognize that, given the mass of the ball, the "fringe spacing" would be minuscule and you would not be able to discern fringes in any real world experiment like this.
But you asked for the "in principle" answer...
A: During the total solar eclipse of 10 May 1994, in Michigan, when you looked at the ground under a nice bushy maple tree you could  see a crescent shaped image of nearly eclipsed sun on the ground -- lots of them, corresponding to where the rays of light passed through the holes in the leaves.  It had become dark enough to provide the required contrast. So this is the case of many holes.
This is an example of multiple pin-hole cameras, and can be explained with ray optics.  I include it here because it illustrates one method of generating multiple images.
For football to diffract from the goalposts, the size must match that of the de Broglie wavelength of the football; they've done this with molecules, including buckyballs.  However, unlike the scenario above, there is only one football, and your detector will only click at one spot for each kick. Many repetitions are required before the diffraction pattern would appear.  
But you only get to detect each football in one place.
