‘When you have eliminated the impossible, whatever remains, however improbable, must be the truth.’ –Sherlock Holmes
The Heisenberg uncertainty principle is in part an embodiment of the idea that in the quantum world, the mere act of observing an event changes it.
But the idea had never been put to the test, and a team writing in Physical Review Letters says “weak measurements” prove the rule was never quite right. […]
Heisenberg’s uncertainty principle, as it came to be known later, started as an assertion that when trying to measure one aspect of a particle precisely, say its position, experimenters would necessarily “blur out” the precision in its speed. That raised the spectre of a physical world whose nature was, beyond some fundamental level, unknowable. […]
They aimed to use so-called weak measurements on pairs of photons. […] What the team found was that the act of measuring did not appreciably “blur out” what could be known about the pairs. It remains true that there is a fundamental limit of knowability, but it appears that, in this case, just trying to look at nature does not add to that unavoidably hidden world.