New Quantum Paradox Throws the Foundations of Observed Reality into Question
If a tree falls in a forest and no one is there to hear it, does it make a sound? Perhaps not, some say.
By Eric Cavalcanti | Associate Professor (ARC Future Fellow), Griffith University

September 04, 2020 | And if someone is there to hear it? If you think that means it obviously did make a sound, you might need to revise that opinion.

(Image: © Shutterstock)

We have found a new paradox in quantum mechanics — one of our two most fundamental scientific theories, together with Einstein’s theory of relativity — that throws doubt on some common-sense ideas about physical reality.

Quantum mechanics vs. common sense
Take a look at these three statements:

* When someone observes an event happening, it really happened.
* It is possible to make free choices, or at least, statistically random choices.
* A choice made in one place can’t instantly affect a distant event. (Physicists call this “locality”.)

These are all intuitive ideas, and widely believed even by physicists. But our research, published in Nature Physics, shows they cannot all be true — or quantum mechanics itself must break down at some level.

This is the strongest result yet in a long series of discoveries in quantum mechanics that have upended our ideas about reality. To understand why it’s so important, let’s look at this history.

More:
The battle for reality
The observer, observed
Our experiment
What does it all mean?