Title: Observing The Universe Really Does Change The Outcome, And This Experiment Shows How
Headings: Observing The Universe Really Does Change The Outcome, And This Experiment Shows How
Observing The Universe Really Does Change The Outcome, And This Experiment Shows How
Content: The most puzzling fact about quantum mechanics is that the answer you get depends on how you look at the individual quanta that are part of the experiment. If you make certain classes of measurements and observations, they behave like particles; if you make other choices, they behave like waves. Whether and how you observe your own experiment really does change the outcome, and the double-slit experiment is the perfect way to show how. This diagram, dating back to Thomas Young's work in the early 1800s, is one of the oldest pictures ... [+]
that demonstrate both constructive and destructive interference as arising from wave sources originating at two points: A and B. This is a physically identical setup to a double slit experiment, even though it applies just as well to water waves propagated through a tank. Wikimedia Commons user Sakurambo
More than 200 years ago, the first double-slit experiment was performed by Thomas Young, who was investigating whether light behaved as a wave or a particle. Newton had famously claimed that it must be a particle, or corpuscle, and was able to explain a number of phenomena with this idea. Reflection, transmission, refraction, and any ray-based optical phenomena were perfectly consistent with Newton's view of how light should behave. But other phenomena seemed to need waves to explain them: