Abstract Time plays a fundamental role in our ability to make sense of the physical laws in the world around us. The nature of time has puzzled people — from the ancient Greeks to the present day — resulting in a long running debate between philosophers and physicists alike to whether time needs change to exist (the so-called relatival theory), or whether time flows regardless of change (the so-called substantival theory). One way to decide between the two is to attempt to measure the flow of time with a stationary clock, since if time were substantival, the flow of time would manifest itself in the experiment. Alas, conventional wisdom suggests that in order for a clock to function, it cannot be a static object, thus rendering this experiment seemingly impossible. Here we show, with the aid of counterfactual measurements, the surprising result that a quantum clock can measure the passage of time even while being switched off, thus lending constructive support for the substantival theory of time.
Abstract Time plays a fundamental role in our ability to make sense of the physical laws in the world around us. The nature of time has puzzled people — from the ancient Greeks to the present day — resulting in a long running debate between philosophers and physicists alike to whether time needs change to exist (the so-called relatival theory), or whether time flows regardless of change (the so-called substantival theory). One way to decide between the two is to attempt to measure the flow of time with a stationary clock, since if time were substantival, the flow of time would manifest itself in the experiment. Alas, conventional wisdom suggests that in order for a clock to function, it cannot be a static object, thus rendering this experiment seemingly impossible. Here we show, with the aid of counterfactual measurements, the surprising result that a quantum clock can measure the passage of time even while being switched off, thus lending constructive support for the substantival theory of time.
Time – what it is and its nature – has from the beginning held mysteries for layman, philosopher, and physicist alike. Periodic phenomena from motions of heavenly bodies and pendulums to quantal atomic clocks provide the means to measure time intervals, and Newton’s absolute time is a background flow against which classical and non-relativistic quantum physics is played out. While internally consistent, these two fields of physics are incompatible with the requirement of treating space and time on an equal footing. Quantum field theories provide the answer, as both treated as parameters, physics residing instead in the states and operators. But even in classical physics and quantum mechanics, time-independent descriptions provide an alternative to an explicitly time-dependent one. These, including a general method of approach called invariant imbedding, are discussed as alternative representations of an underlying reality that is the concern of physics.
The problem of time is a deep paradox in our physical description of the world. According to Aristotle's relational theory, time is a measure of change and does not exist on its own. In contrast, quantum mechanics, just like Newtonian mechanics, is equipped with a master clock that dictates the evolution of a system. This clock is infinitely precise and tacitly supplied free of charge from outside physics. Not only does this absolute time make it notoriously difficult to make a consistent theory of quantum gravity, it is also the underlying problem in establishing the second law. Indeed, contrary to our experience, the Wheeler-deWitt equation --a canonical quantization of general relativity-- predicts a static universe. Similarly, when simply concerned with the dynamics of a closed quantum system, there is no second law because the Von Neumann entropy is invariant under unitary transformations. Here we are mainly concerned with the latter problem and we show that it can be resolved by attributing a minimal amount of resources to the measurement of time. Although there is an absolute time in quantum mechanics, an observer can only establish a time by measuring a clock. For a local measurement, the minimal entropy production is equal to the number of ticks. This lower bound is attained by a black hole.
Clocks are systems for measuring frequency, velocity, duration and numerical order ntttt.......,, 210 of physical events. Time t obtained with clocks is not a forth dimension 4X of space, time t is only a component of tciX ∗∗=4. This view of clock/time as a measuring system sees physical phenomena running exclusively in space and not in time. This view is supported with several experiments which confirm that time t of physical event can be zero. Time is not part of space; time is run of clocks in space. Past, present and future exist as a psychological time in the mind only not in the universe. We experience motion i.e. change in the space through the frame of psychological time. We “project ” linear psychological time “past-present-future ” into the space, however it is not there. Observer who distinguishes between space-time, physical time and psychological time is aware that in quantum measurement he only measures physical events in space and not in time. Clock/time is merely a measuring device. With this understanding observer’s observation, measurement and experience of quantum phenomena are closer to their real nature. Stream of numerical order of quantum phenomena ntttt.......,, 210 runs in space only and not in time. Stream of quantum phenomena has no duration on its own. Duration is result of measurement.
In last years, we are witnessing a trend, of trying to describe the laws of nature using informational tools instead of by functional tools. This change towards more abstract description of the nature, is a natural development, as from the time of the Greeks, through the time of Newton, followed by Analytical Mechanics, all the way up to General Relativity and String Theory, there was always a preference to the more abstract and general description of nature. The reason we prefer the more general and abstract descriptions, is that they give us a more objective point of view at the laws of Nature, which allow us more effectively to separate between Phenomena that are the manifestation of the deep laws of Nature, and Phenomena that are just being resulted by our very specific point of view at the universe, and the specific description that we have decided to give it. The more abstract descriptions give us a better frame of reference in our attempted to understand the origins of the laws of Physics. Informational description of the Universe is suspected to be better than the Functional description, as it is a more abstract and general point of view of the Universe, and yet, there is no complete and simple way to translate every Physical Theory to informational language. In this article I have attempted to do just that, by taking two tied Philosophical arguments, and giving them a Formal and Mathematical meaning, by so upgrading them into Physical Principals. The first Principle is the idea that the only objective thing in Nature, that does not depend at the observer point of view, is the different options that realty can exist in. This set of options of reality is meaningless and lacks structure in any way besides their combined number (cardinality), and I name these options of reality “cosmoses”. The second Principle is that there are observers, that are bound to one option of reality, but unable to separate between their cosmos to other cosmoses. This inability to completely know in what cosmos they do exist, creates a local structure. This structure, and the way it changes over time is what creates the structure of the universe that the observers (including you dear reader) measure. By using this simple language, I was able to suggest some new tools and predictions.
A clock is a dynamical system which passes through a succession of states at constant time intervals. If coupled to another system, it can measure the duration of a physical process and even keep a permanent record of it, such as in a time-of-flight experiment or in observing the lifetime of an unstable atom. A clock can also be used to control the duration of a process, e.g., the precession of a spin in a magnetic field which is turned on and off at prescribed times. This article shows how to construct time-independent Hamiltonians describing these possible uses of a quantum clock. As expected, a good time resolution entails a large energy exchange between the clock and the other system, thereby modifying the evolution of the latter. This evolution may even be halted by using a clock which is too precise (this is the quantum analog of Zeno’s paradox).