Does reality exist when no one is watching it? Like the age-old puzzle of whether a tree falling in a forest where no one can hear makes a sound, this question is one of the most interesting in quantum mechanics.

In a new study published in the journal Communications Physics, Brazilian scientists suggest that reality exists “in the eye of the beholder.” They tried to test the principle of complementarity, proposed by the Danish physicist Niels Bohr in 1928. The principle claims that objects have pairs of complementary properties that cannot be observed or measured simultaneously.

A new study conducted in April 2022 allowed scientists to conclude that physical reality in the quantum world consists of mutually contradictory entities that, after all, do not contradict, but complement each other. According to scientists, this is an exceptional result.

“The Brazilian researchers have devised a mathematical framework and corresponding experimental configuration that allows the testing of quantum theory, particularly understanding the nature of complementarity by studying the physical realism of the system,” comments the associate professor of physics at Fordham University.

“The fact that a material particle may behave like a wave and light like a particle, depending on the context, is still one of the most intriguing and beautiful mysteries of quantum physics,” says one of the authors of the study.

Efforts to better understand quantum mechanics could potentially help create quantum technologies that far outpace current ones. The fact that reality can exist in the eye of the beholder is a very peculiar aspect of physical reality. There is still a lot of work to be done before solving this mystery.