both here & there at the same time
from: The Economist March 11 2017
Strange but true
Quantum mechanics -a theory of the behaviour at the atomic level put together in the early 20th century- has a well-earned reputation for weirdness. That is because the world as humanity sees it is not, in fact, how the world works.
Quantum mechanics replaced wholesale the centuries-old notion of a clockwork, deterministic universe with a reality than certainties -one where the very act of measurement affects what is measured.
Along with that upheaval came a few truly mind-bending implications, such as the fact that particles are fundamentally neither here nor there but, until pinned down, both here and there at the same time: they are in a "superposition" of here-there-ness.
The theory also suggested that particles can be spookily linked: do something to one and the change is felt instantaneously by the other, even across vast reaches of space. This "entanglement" confounded even the theory's originators.