"People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion." - Albert Einstein

"The only reason for time is so that everything doesn't happen at once." - Albert Einstein

Everything we call real is made of things that cannot be regarded as real. Niels Bohr

“[T]he atoms or elementary particles themselves are not real; they form a world of potentialities or possibilities rather than one of things or facts.”
― Werner Heisenberg

“Consciousness cannot be accounted for in physical terms. For consciousness is absolutely fundamental. It cannot be accounted for in terms of anything else.”
― Erwin Schrödinger

No phenomenon is a physical phenomenon until it is an observed phenomenon.
— John Wheeler

“At the heart of quantum mechanics is a rule that sometimes governs politicians or CEOs - as long as no one is watching, anything goes.”
― Lawrence M. Krauss
Note: recently revised to include times one being watched as well..