Thomas Young (1773-1829) was a British polymath who spoke thirteen languages fluently. A physician, physicist, and linguist he is also known for demonstrating the wave nature of light. In his time, light was thought to be a particle. He proved it is wave also. His methods came to be known as the Thomas Young Double Split experiment. While the experiment demonstrates wave/particle duality, modern interpretation also reveals the power of human intent. Young drew his conclusions using sunlight from a pin-hole in a window blind. Since then the experiment has been run with laser light, actual matter, and more recently, designer chemical compounds which are within an order of magnitude the size of a human virus.
The set up includes a source of light, a filter that has two side by side slits cut in it, and a receiving (recording) screen as shown below.
When one slit is open the photons (the units of light) advance to the receiving screen where they manifest as a particle, much like the photons from a flashlight illuminate a location specific spot where the flashlight is pointed. However, when both slits are open the photons manifest on the receiving screen in a spread-out pattern. They reach the screen in wave format. Note too, the pattern on the screen has blank spots in it. They are caused by destructive interference. Destructive interference occurs when the wave from one slit which is undulating upward meets a wave from the other slit which is undulating downward, whereupon a cancellation (destructive interference) occurs. This pattern is tell tale of wave behavior.
The equipment arrangement is representative of human intent. After all, the decision to have one or two slits open were human made. When only one slit is open the expressed intent is to locate the photons in space, i.e., there is only one route the photons can take to the receiving screen. Thus, they are observed and arrive as particle. With both slits open, the equipment set-up effectively communicates an indifference to the route taken, i.e., take the left slit or the right, who cares. This indifference is an intent to not-observe and the photons remain in wave format.
The Double Slit Experiment is where man gets the notion that matter is mind dependent. As Nobel laureate Max Planck (1858-1947), the reputed father of quantum theory says, “All matter is a derivative of consciousness.”