Example Of A Crazy Model: The Path Integral.

I recently discussed how it may be that mathematical models that describe our universe may or may not be what is actually going on but: it's okay since these models have predictive power.

For example, take the famous path integral.

Remember the double slit experiment shown in the picture below.  If you ask: what is the probability that an elementary particle released at point s, it ends up at point o?  It turns out, being non-technical here, to get the right answer you have to assume the particle to go through both holes together.

Now, run the same experiment where now you have two screens with multiple slits.( See picture below)  Again, to get the right answer, you need to assume the particle, in some sense, travels from s to o in every path possible.

No, add in infinite number of screens and drill into them an infinite number of holes.  What do you get?  Free space!  Yet surprisingly, you get the right quantum physics if you assume the particle still has to travel through all the infinite holes of the infinite screens: Ie, you assume the particle moves from point s to o taking every path possible in free space.

Now, though I didn't state all the details 100% technically correct, the basic intuitive idea of what is going on is still correct.  The math we use is suggests the particles take, in some sense, every possible path.

Now, is this really what is going on, or is this just a model?  I'm guessing it is just a model.  However, it's okay since it has significant predictive power.

Nevertheless, the question is always going to pester me: why do such bizarre models give such amazing answers?!?!  Nature is very interesting indeed.

(These images were taken from Quantum Field Theory In A Nutshell By A. Zee. This book has an amazing section on path integrals.)