Physics
Observer Effect
Quick fact
In quantum mechanics, the observer effect is not due to clumsy measurements but is an inherent property of nature: a particle exists in multiple states at once until measured, at which point it 'chooses' just one.
Why this is interesting
You've probably heard that looking at something changes it—but in the quantum world, this isn't just a saying; it's a fundamental law of nature. How can simply 'observing' an electron force it to behave differently?