What is Time?
Question: What is time?
Answer: Time is matter in motion.
Question: What is motion?
Answer: Motion is change, i.e. changes in position and velocity.
Question: What does it mean for “time to stop?”
Answer: Time stops when all motions stops, i.e. time stops when matter stops changing. Time stops when everything is at absolute zero Kelvin and there is zero energy in the universe.
Question: Is there a direction for time, like past, present, and future?
Answer: Direction refers to position and motion. Only matter has position and motion. Time has no motion and no direction. Time is what matter does. The qualities and attributes of time are strictly derived from attributes of “matter in motion”. The past are those motions which we have observed. The present consists of the motions we see now. The future is the motions that we will see.
Question: Is time travel possible?
Answer: Time is not a position or location. Time travel would presumably mean moving from one state of matter in motion to another state of matter in motion. This happens all the time everyday at every moment everywhere we look. Motion is moving. But we cannot interact with all matter in all states of motion. However we can interfere locally and can do work on isolated systems. Therefore we say “time travel is possible in isolated systems”. In isolated systems, we can bring in energy from the environment and do work on the system and thereby transform states. To travel in time means working on the system to change a present state into a past state. There is nothing mysterious here, we are simply saying that “winding the hands of a clock” is work which time travels the clock back to a previous state. But winding the clock does work only on the clock and not on the environment. In the isolated system consisting of only the clock, we have time travelled. But we have not done any work on the larger environment and therefore have not time travelled in any wider sense.
GPS
We have a question: “Do Lorentz transformations and Einstein’s special relativity actually enter into real world GPS calculations?” Or do we simply use classical Newtonian physics combined with expectation that \(c\) really is the speed of light propagation in vacuum? This is like classical Maxwellian theory. We don’t know. And we really wonder if these calculations are accurate or not. Nobody would really know. Is a detailed study of GPS necessary or profitable?
Reviewing the basic history of navigation, latitude and longitude, it’s interesting to first consider the latitude problem, which historically was much simpler to solve. Here the navigator takes advantage of the “fixed” northern star, and measuring the angle from the horizontal to the northern star we find a measure \(\theta\) of the latitude, i.e. our angular distance from the Earth’s equator. It’s interesting to see how errors \(\Delta \theta\) compound the distance errors. This uses the fundamental definitions of spherical distances, i.e. \(\Delta C = R_{\text{Earth}} \cdot \Delta theta\).
Note: this method allows us to construct the latitude coordinate. This is not quite a distance measurement. Given two points \(x,y\), we could measure the angles \(\theta_x\), \(\theta_y\) from the horizontal to the fixed north star. But the distance \(dist(x,y)\) is underdetermined without another measurement, and here enters the longitude problem. Longitude requires a \(\Delta t\) computation, i.e. relative time difference between sunsets at Greenwich and at sea. The history of the longitude problem is quite amazing…
What is a Clock?
*What is a clock?
According to David Wineland’s lecture a clock consists of a periodic event generator and a counter. This definition might appear circular unless one adopts Mach’s view that time is matter in motion. The periodic event generator, whatever it is, is precisely the motion which is defining the clock. Whether the motion is regular or irregular, whatever that means, doesn’t matter. Even a broken clock tells a time at all times. And it’s always right from it’s own perspective.
What are regular time intervals?
When the matter in motion is periodic, and also when the periods appear relatively identical and indistinguishable, then we consider the motion to be regular or uniform. For example in determining the longitude, it’s assumed that the sun rises and sets regularly along the Greenwich meridian line. This is not strictly the case, as known by the ancients by the precession of the equinox and the great year.
Are all periodic motions candidates for clocks?
Briefly, yes. The simplest periodic systems are the spring, and the simple pendulum. In measuring longitude, the problem is the interaction of these periodic motions with the environment. For example, the simple pendulum is affected by the motion of the ocean waves. The longitude problem required a stable accurate clock for sea vessels on long voyages in deep waters.
Moreover simple pendulums are affected by the gravitational potential, therefore the periodicity of the simple pendulum is affected during high altitude flights. Assis makes this point clearly in (Assis 1999) where the periodicity of the pendulum is well known to depend on the gravitational constant \(g\).
The problem of stable clocks unaffected by the motion and bulk interaction with the oceans is very interesting. We should assume that it’s a fundamental problem. We like to imagine the pendulum as an isolated system, but this idealization is disturbed by the reality of the pendulum’s interaction with the environment.
We think it’s important to study the basic examples of oscillatory motion, because if the Weber-Sansbury model is correct, then oscillatory atomic motions are modelled precisely on electrical planetary models. Furthermore Sansbury emphasizes Bohr’s idea that Planck’s spring oscillators can be seen as planetary orbits when seen “along an axis”. See (Sansbury, n.d.), (Sansbury 2012).
Simple Pendulum
Example. A small mass with inertial mass \(m_i\) and gravitational mass \(m_g\) attached to a string (not a spring). The period of the simple pendulum becomes \[T_{period}=2\pi \sqrt{\frac{m_i}{m_g} \frac{\ell}{g}}.\] So it becomes evident that the period depends on \(g\).
Question: For the instability of pendulums in boats, does the moving ocean cause variations in \(g\) or is there another effect? Likewise during high altitude flight navigation, with many electrodynamic interactions and huge differences in the gravitational potential. Of course Assis’ point is that time meanwhile is running the same in all cases. That is, pendulums and clocks don’t measure global time. But they define their own time.
Remark. Experiments indicate that the half-lives of accelerated unstable radioactive mesons is much greater than the half-lives of mesons at rest in the laboratory. But what does this really demonstrate? We agree with Assis, Phipps, etc, that the experiments rather indicate the half lives depends on their accelerations and large velocities relative the stars at infinity, and on the strong electromagnetic fields being used to accelerate the mesons.
Like the pendulum in the ocean, the problem is that everything interacts with everything all the time. There is no real shielding or isolated systems.