One of the strangest phenomena in quantum physics is the observer effect, which can be demonstrated using the double-slit experiment, the outcome of which is often described as mysterious, a term not often used in the scientific world.

The reason for this label is because the outcome of the experiment depends on whether we observe or measure the results.

The experiment involves shining a beam of light at a panel with two parallel slits in it. Some of this light passes through the slits, forming two paths. The emerging light from the slits acts like waves. They interfere with each other. The interference can be seen when the light hits a second panel as a series of alternating brighter and darker spots. The pattern appears brighter where the waves converge and reinforce each other.

This experiment shows us that photons, which are particles of light, can behave like waves as well as particles....