The Double Slit Experiment

Here in what Art Bell called "The Quickening", we constantly receive new and shocking quantum revelations of how the world we are living in is not the world we thought we were. But we actually got our biggest heads-up about the true nature of reality back in 1801, when Thomas Young performed the original "double slit experiment" to determine the properties of light.

Here's how it works:

A beam of subatomic particles is directed at a surface that will record the impact of said particles. A screen with two slit openings is placed in front of that surface, and these slits can be opened to allow the particles to pass through or closed to keep them out.

Now, common sense would tell you, like aiming a firehose at two openings in a wall, that if both slits are open, twice as many particles will pass through. But bafflingly, that is not the case. More particles get through if only one slit is opened.

You get an Moire-style interference pattern when you have two slits open, and stranger still, when you reduce the light source to only one photon at a time, it still makes the interference pattern, one dot at a time, if you repeat the experiment over and over. But if you close one of the slits, the pattern disappears. This shouldn't make any difference. And yet it does.

How does the particle know that one of the slits will be opened or not opened?

And that's not the crazy part. The crazy part is this: if you try to track the photon so you can witness which slit it actually chose to go through, the pattern disappears. Placing a detector even in just one of the slits will result in the disappearance of the interference pattern. Again, this shouldn't make any difference whatsoever to how the particle behaves. And yet it does.

The act of looking at something changes it.