"[T]ime is not an illusion, but the flow of time is. So is change. In spacetime, the future exists and the past doesn't disappear. When we combine Einstein's classical spacetime with quantum mechanics, we get quantum parallel universes... This means there are many pasts and futures that are all real—but this in no way diminishes the unchanging mathematical nature of the full physical reality. ...[A]lthough this idea of an unchanging reality is venerable and dates back to Einstein, it remains controversial... with scientists I greatly respect expressing a spectrum of views. ...Julian Barbour argues in his book The End of Time not only that change is illusory, but that one can even describe physical reality without introducing the time concept at all."