What If I Told You: Reality Simply Doesn't Exist Until We Measure It?

by Monica Joshi

Remember that infamous question: if a tree falls in a forest and no one is around to hear it, did it really fall? A lot of us have answered this metaphysical question quite easily over the years with an overwhelming 'yes'. Well, this goes way beyond that and into the quantum level of atomic reality. Australian scientists have recreated a famous experiment and confirmed quantum physics' bizarre predictions about the nature of reality, by proving that reality doesn't actually exist until we measure it... at least, not on a very very small scale.

This mind-boggling, bizarre ordeal is really answering a very simple question: if you have an object that can act like either a particle or a wave, at what point does it decide between the two? The new experiment, a recreation of John Wheeler's delayed choice thought experiment, has suggested that it is only when we measure the atoms that their observable properties come into reality.

The experiment, first proposed back in 1978, required using light beams bounced by mirrors. However, back then, the technology needed was pretty much impossible. Today, almost 40 years later, the team from Australian National University has finally managed to recreate the experiment using helium atoms scattered by laser light. While John Wheeler's experiment called for a photon, Dr. Andrew Truscott of the Australian National University used a helium atom, according to his published findings in Nature Physics.

In order to successfully recreate the experiment, the team trapped helium atoms in a suspended state known as Bose-Einstein condensate. They then ejected them all until there was a single atom leftover. The chosen atom was then dropped through a pair of laser beams. This created a grating pattern that acted as a crossroads that would scatter the path of the atom, much like a solid grating would scatter light.

Roman Khakimov, a PhD student who worked on the experiment, said that:

"Quantum physics predictions about interference seem odd enough when applied to light, which seems more like a wave, but to have done the experiment with atoms, which are complicated things that have mass and interact with electric fields and so on, adds to the weirdness."

To make the experiment even more interesting, they then added a second grating that recombined the paths. However, this was only after the atom had already passed the first grating. When this second grating was added, it led to constructive or destructive interference. This is an expected result only if the atom had actually travelled both paths just like a wave would. However, it is interesting that when the second grating was added, no interference was observed, as if the atom had chosen only one path.

This second grating was added only after the atom had passed through the first crossroads, suggesting that the atom hadn't yet determined its nature before being measured a second time. Truscott explained that a future measurement was quite clearly affecting the atom's path as the atom seemed to take a particular path or paths.

In other words, Truscott went on to explain that:

"[As] the atoms did not travel from A to B, it was only when they were measured at the end of the journey that their wave-like or particle-like behaviour was brought into existence."

For us, an object is either wave-like or particle-like by its very nature, so that waves are wave-like and solid objects are particle-like. However, quantum theory holds that for the very small, this distinction breaks down, i.e. light can behave as either a wave or a particle; the same holds true for objects with mass like electrons.

Is your mind blown yet? While this all sounds incredibly weird, it's actually confirmation of the quantum theory that already governs the world of the very small. This theory has already helped us develop things like LEDs, laser and computer chips and now it has been clearly and thoroughly confirmed via this particular experiment.