Alternative facts are spreading like a virus across society. Now it seems they have even infected science—at least the quantum realm. This may seem counter intuitive. The scientific method is after all founded on the reliable notions of observation, measurement and repeatability. A fact, as established by a measurement, should be objective, such that all observers can agree with it.

But in a paper recently published in Science Advances, we show that in the micro-world of atoms and particles that is governed by the strange rules of quantum mechanics, two different observers are entitled to their own facts. In other words, according to our best theory of the building blocks of nature itself, facts can actually be subjective.

Observers are powerful players in the quantum world. According to the theory, particles can be in several places or states at once—this is called a superposition. But oddly, this is only the case when they aren’t observed. The second you observe a quantum system, it picks a specific location or state—breaking the superposition. The fact that nature behaves this way has been proven multiple times in the lab—for example, in the famous double slit experiment (see video).