If a tree falls in a forest and no one is there to hear it, does it make a sound? Perhaps not, some say.

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.

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:

  1. When someone observes an event happening, it really happened.

  2. It is possible to make free choices, or at least, statistically random choices.

  3. 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.

To read more, click here.