[Above left:] As soon as a detectors were turned on to observe the electron pass by, the path of the electrons striking the back wall were indicative of particles. Some would pass through the left window, then others through the right window. Over time, two distinct scatter patterns would result.

This pattern would happen even if one of the detectors was turned off. Since there are only two windows, it would still be easy to determine which window was used. So the information would still allow us to "know" the path of the electron hitting the target. Right?

But if you turn both detectors off, or don't even use them at all, the pattern on the target will revert to a wave pattern! Also, if you used the detectors but then didn't turn them on, or didn't look at the information coming from them (even if they are on) then the pattern will be that of a wave.

The point I am trying to make here is that just by our being aware of an electron, photon or any part of the electromagnetic spectrum, we change the state of that electron from a wave to a particle. Yes, you heard correctly. Our awareness, consciousness of the material world changes that world.

It gets even stranger!

When does the electron change from one form to the other? Does it happen when the particle is being detected? Could the mere act of detection be enough to collapse the wave and form a particle pattern?

To test his hypothesis a man named John A. Wheeler designed an ingenious way of altering the double slit experiment that would, he thought, prove that the process of detection was not responsible for the change from wave to particle patterns.

First, Wheeler had two powerful telescopes -- one focused on each slit. For this experiment Wheeler used light, photons. If a photon went through one or the other slit, the telescopes could see it. The telescopes were placed where the fuzzy rectangles would register a photon hit from a particle pattern. Since the light had to travel to the telescopes, they served as a detector.

Wheeler then devised a detection screen that could be very quickly placed in front of the telescopes, after the photons left their source, preventing them from reaching the detectors (telescopes) but recording where the photons landed on the screen. So what he was attempting to do was to record the photons paths before and after they were detected.

The mechanism [Below:] was constructed so that the distance between the wall with the slits was quite far from both the removable detection wall and the telescopes.

Because these distances and speed of light were known, it was possible to know when a photon had been released, passed through either or both of the slits and was somewhere between the slits and the telescopes. We call this time =x in the animation below. At this precise moment the detection screen could either be placed in front of the telescopes or removed.

[See animation below]

The idea was that the photon should have already decided if it was going to react like a particle or a wave after it had passed through the slits and "noticed" it was headed for the telescopes where it would be observed. And this decision by the photon should be irreversible. I mean, it's after passing through the slits so how can it change?

By putting up the screen after the photon passed the slits, but before the telescopes received the light, Wheeler expected the photon would act like a particle. He expected to see two fuzzy rectangles on the detection screen. (Is your head spinning yet?)

In the actual experiment, when the photons passed through the slits, if the detector wall was quickly put in place, they displayed the wave pattern on the wall. But, if after the photons passed through the slits, the detector wall was suddenly removed, the telescopes would capture the photons in the area where two fuzzy rectangles would be -- indicative of a particle.

The decision on which type of detection is used (screen or telescopes) was being made after the photons have passed through the slits -- presumably after they have already decided to be a wave or a particle. It is as if the photons realized they were being tricked, went back in time to before they passed through the slits and then changed their state accordingly.

Ordinarily we have "cause-effect" timelines in nature. But this experiment seems to show that the effect can change the cause. And even more significant is the fact that our own observation is the thing altering the cause.

In other experiments, the detectors were used to determine through which slit the photon passed but the electronics that reported or recorded the results were turned off. This is the so-called Earasure Paradox because, despite being detected, because no human was aware of this, the interference (wave) pattern resulted.

It seems that it is not the detection that matters but whether a human mind is aware of it or not!