How can reality exist

Reality: The bedrock of it all Can we explain reality purely in terms of matter and energy, asks Valerie Jamieson Read more. Reality: Is matter real? It is much harder to work out what it is Read more. Reality: Is everything made of numbers? Dig deep enough into the fabric of reality and you eventually hit a seam of pure mathematics, says Amanda Gefter Read more.

Reality: A universe of information What we call reality might actually be the output of a program running on a cosmos-sized quantum computer, says Michael Brooks Read more.

Reality: How does consciousness fit in? Is the universe really all inside your head, asks Michael Brooks Read more. But the birth of quantum physics in the early s made it clear that light is made of tiny, indivisible units, or quanta, of energy, which we call photons.

Some have even used it to argue that the quantum world is influenced by human consciousness, giving our minds an agency and a place in the ontology of the universe. But does the simple experiment really make such a case? On the other side of the barrier is a screen that records the arrival of the particles say, a photographic plate in the case of photons. Common sense leads us to expect that photons should go through one slit or the other and pile up behind each slit.

Rather, they go to certain parts of the screen and avoid others, creating alternating bands of light and dark. These so-called interference fringes, the kind you get when two sets of waves overlap. When the crests of one wave line up with the crests of another, you get constructive interference bright bands , and when the crests align with troughs you get destructive interference darkness.

The wave function behaves like a wave. It hits the two slits, and new waves emanate from each slit on the other side, spread and eventually interfere with each other. The combined wave function can be used to work out the probabilities of where one might find the photon. The photon has a high probability of being found where the two wave functions constructively interfere and is unlikely to be found in regions of destructive interference.

It goes from being spread out before measurement to peaking at one of those places where the photon materializes upon measurement. This apparent measurement-induced collapse of the wave function is the source of many conceptual difficulties in quantum mechanics.

The photon is not real in the sense that a plane flying from San Francisco to New York is real. In the double-slit experiment done with single photons, all one can do is verify the probabilistic predictions of the mathematics. So it is rather unsettling to discover this might all be a fabrication. Some researchers even contend that the live-stream movie in my head bears no resemblance whatsoever to reality.

On top of this, our brain presents us with only a snapshot. If our senses took in every detail, we would be overwhelmed. Did you notice the last time you blinked, or that fleshy protuberance called your nose that is always in your peripheral vision?