According to a well-known theory in quantum physics, a particle’s behavior changes depending on whether there is an observer or not. It basically suggests that reality is a kind of illusion and exists only when we are looking at it. Numerous quantum experiments were conducted in the past and showed that this indeed might be the case.
Now, physicists at the Australian National University have found further evidence for the illusory nature of reality. They recreated the John Wheeler’s delayed-choice experiment and confirmed that reality doesn’t exist until it is measured, at least on the atomic scale.
Some particles, such as photons or electrons, can behave both as particles and as waves. Here comes a question of what exactly makes a photon or an electron act either as a particle or a wave. This is what Wheeler’s experiment asks: at what point does an object ‘decide’?
The results of the Australian scientists’ experiment, which were published in the journal Nature Physics, show that this choice is determined by the way the object is measured, which is in accordance with what quantum theory predicts.
“It proves that measurement is everything. At the quantum level, reality does not exist if you are not looking at it,” said lead researcher Dr. Andrew Truscott in a press release.
The original version of John Wheeler’s experiment proposed in 1978 involved light beams being bounced by mirrors. However, it was difficult to implement it and get any conclusive results due to the level of technological progress back then. Now, it became possible to successfully recreate the experiment by using helium atoms scattered by laser light.
Dr. Truscott’s team forced a hundred of helium atoms into a state of matter called Bose-Einstein condensate. After this, they ejected all the atoms until there was only one left.
Then, the researchers used a pair of laser beams to create a grating pattern, which would scatter an atom passing through it just like a solid grating scatters light. Thus, the atom would either act as a particle and pass through one arm or act as a wave and pass through both arms.
Thanks to a random number generator, a second grating was then randomly added in order to recombine the paths. This was done only after the atom had already passed the first grate.
As a result, the addition of the second grating caused interference in the measurement, showing that the atom had traveled both paths, thus behaving like a wave. At the same time, when the second grating was not added, there was no interference and the atom appeared to have traveled only one path.
The results and their interpretation
As the second grating was added only after the atom had passed through the first one, it would be reasonable to suggest that the atom hadn’t yet ‘decided’ whether it was a particle or a wave before the second measurement.
According to Dr. Truscott, there may be two possible interpretations of these results. Either the atom ‘decided’ how to behave based on the measurement or a future measurement affected the photon’s past.
“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 behavior was brought into existence,” he said.
Thus, this experiment adds to the validity of the quantum theory and provides new evidence to the idea that reality doesn’t exist without an observer. Perhaps further research in the field of quantum physics and more thought-provoking evidence like this will completely change our understanding of reality one day.
“If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet.” – Niels Bohr
Reference: The Mind Unleashed