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Free Will 321

[Image of Newton's Rings interference pattern]

Newton's Rings

It turns out a single photon can interfere with itself! How can this be? It must somehow split up and consider both the available paths reflecting off the glass surfaces.

Now that we have these two concepts in our head, that a photon sometimes reflects and sometimes does not, and a single photon must consider both paths, we can ask: what tells the photon what to do?

There are only three possible answers: the light source that emitted the photon, the pane of glass that reflected the photon or the observer that saw the photon – me.

The first obvious place that might control the photon is the original source of the photon; the light bulb. The photon might leave the bulb already knowing what path to follow, whether it will be reflected and whether that reflection will be affected by the gap between the two surfaces in a positive or negative way. This is sometimes called a pilot wave theory. The problem with this theory is I could insert a piece of glass into the experiment after the photon has left the light source. This will affect the photon but the light source could not have known my intention in advance and told the photon what to do. Therefore, the path of the photon is not pre-programmed by the light source.

Now our photon has left the bulb and is traveling toward the glass. The glass has two surfaces. The photon reaches the first surface and has to decide if it will reflect. But there is a problem. The second surface

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