Hi Shahab,

"clock" stands just for time measuring devices. The only reason for using "atomic clocks" is their high accuracy. In a setup where the expected final difference between two clocks were, say, 20% of the runtime, we could use two hourglasses as well as any processes which take a known time (like cooking spaghetti: in one system the spaghetti are al dente, in the other system they are overcooked ;-) .

So, the gist of this part of the theory is not that a certain kind of clock is affected but that time itself passes differently.

good question

Dear Joerg Fricke thanks a lot for your very valuable discussion :)

i can understand, velocity and gravity can influence the physical properties such as boiling point and boiling time.

but if you consider the physical properties of an element ( spaghetti) is independent of velocity and gravity, we can tell that time is dynamic

The clocks themselves are not affected. To compare them, you have to do a geometric projection of the ticks of one clock onto the worldline of the other. The difference in rates comes from that geometric comparison.

Thanks George Dishman

Can i guess that Time Dilation is just a mathematical hypothesis?

Interesting question and discussion!

The question is great ! . You are perhaps referred to Sir Albert Einstein ' s special theory of relativity .Your question is a fallacy . Actually no time / speed is absolute . Everything is relative ie clock is moving with a fixed time w.r to the specific country or that zone , because in other zone of universe the same clock will show different time . So only absolute is the speed of the universe. But whether this speed is also w.r to the speed of light ??

.

Clock for time and time is relative. Most people told time by some reference to the position of the sun or moon.

An exciting question and a wonderful discussion.

Afraa Ibrahim Samir M. Ismail Mila Ilieva

Thanks all for giving your valuable inputs

Here I am trying to explain two simple illustrations of ‘Time Dilation’ in respect of ‘Velocity’ and ‘Gravity’

Illustration 1: Time-Velocity

I and my friend were going class from our dormitory. We had started at the same time (9:00 AM) from dormitory. However, I was going on foot and he was using his bike. He was going faster than me. When he reached faculty it was 9:05 and it was 9:15 for me. In this illustration I can say that my clock was moving faster than my friend.

Illustration 2: Time Gravity

I and my friend were going class from our dormitory. We had started at the same time (9:00 AM) from dormitory. There was a dry river on the way. He had crossed the river using bridge. However, I did it without the bridge as the river bed was dry. When we reached our class, it was 9:15 for my friend and 9:20 for me. If we consider the river depression was due to gravity, we can say my clock was moving faster.

waiting for your comments and suggestion on those illustrations ... hope we can learn together more effectively

Dear Shahab,

SU: Can i guess that Time Dilation is just a mathematical hypothesis?

Certainly not. It was first proven by Ives and Stilwell around 1938:

https://en.wikipedia.org/wiki/Ives%E2%80%93Stilwell_experiment

It has been confirmed in particle accelerators and the GPS system many times beyond all doubt. It follows from Lorentz Invariance which has been tested to an accuracy of one part in 1018:

https://phys.org/news/2015-09-precise-lorentz-symmetry-photon-constant.html

The trick to understand what this tells you about the relationship between space and time. The two have to be treated a a 4-dimensional whole within which we exist. If two people meet for coffee one day, then go their separate ways and then meet again the next day, watches on their wrists if accurate enough would register a slight difference in the duration between their meetings but that is no more surprising than there being a difference in the number of steps they took between the meetings. If one went jogging while the other watched TV, there would be a large difference in their step count and a small difference in the amount they aged for the same reason. Both time elapsed and distance travelled depend on the path taken between the meetings.

Dear George Dishman Very simple and clear examples ... thanks a lot :)

Dear George Dishman One more question

if i agree with your two examples... it means there are infinity time domains and space domains.... all the domains can be as small as an atom or less. is so, my different body parts aging at a different rate .. I am right ?

Dear Shahab,

It is better to think that there is one domain, often called a manifold for mathematical reasons, within which we all exist, but there are an infinite number of paths we can take within that manifold. In a field with two gates on opposite sides, there are an infinite number of paths from one gate to the other. Because of the geometry, if you enter at the south side and leave at the north side, you can only move in a direction the is between north west and north east, but there are still an infinite number of paths you can take. Along their chosen path, everyone ages at the same rate but because the paths have different lengths from one gate to the other, people who enter with the same age will leave with different ages.

You should think of the ticks of a clock in this analogy like the number of steps you take. Everyone's stride is the same length (a second is the same duration for everyone) but the number of steps from one gate to the other depends on the path.

It's worth thinking about the "Twins Paradox", many years ago I wrote a very simple interactive web page just as an example when I was trying out HTML5:

http://www.georgedishman.f2s.com/html5/twins.html

Changing the slider alters the motion of an independent observer who monitors the history of the twins.

Dear George Dishman many many thanks ... i think i have learned something...

I am still not clear how we define time to explain Time Dilation... time here same as solar year or lunar month ?

Relative Relation Relationship

Dear Mohammed Jaafar Ali Alatabe thanks a lot for your very precised and valuable answer

Many many thanks Dear Nour Shakir

Time is for Clock or Clock is for Time?

Clock is for time (measurement tool for time), time is also relative and finding time is a precious resource which is getting less & less or running faster & faster in the more recent years of my life.

Interesting answers. Following

I believe clock is for time

Dear Shahab,

SU: I am still not clear how we define time to explain Time Dilation... time here same as solar year or lunar month ?

Have you played with my interactive page?

http://www.georgedishman.f2s.com/html5/twins.html

When you first open it, you'll see the picture on the left of the composite image attached. That is a representation of the story where one twin flies off to a nearby star (6 light years away at 0.6c) and then returns at the same speed. Each dot represents a birthday party so they are of course one Earth year apart. The whole is drawn with hindsight from a time some years after the travelling twin has returned home.

On the left is how the stay-at-home twin represents what happened. He celebrated each year, the grey grid shows time vertically with units of one year and distance horizontally with the units being light-years. You can see that his parties (the blue dots) are exactly on the lines. His more adventurous sister flew away and her dots seem to be farther apart, her existence has been "time dilated" so it appears to Bob that Alice's clocks are ticking slower and her ageing matches that.

The image on the right however is the same events plotted from Alice's point of view during her outward journey. You can see that now her parties fall on the grid and it is Bob's that are farther apart, as she measures them. Bob's time appears "dilated" relative to Alice.

To follow this, what you need to understand is that time is measured along the worldlines of the clocks. Alice determines the rate of Bob's clock by drawing horizontal lines from his parties onto her clock line because a horizontal joins that happen "at the same time". Remember time here is plotted on the vertical axis of the graph.

Physically, all the dots along any line are exactly the same spacing apart, one year when measured along the line. That tells you about the physical nature of time.

If you can grasp this picture in simple empty space, the same understanding will apply when you start to learn about gravity. What we call gravity is a curvature of the grid lines caused by the presence of energy (usually dominated by mass through E=mc2).

Do please try looking at the web page and moving the slider. All you are doing is rotating the graph of the events but it looks unusual because of the hyperbolic geometry of spacetime.

Thanks George Dishman :) :)

Dear George Dishman Thanks a lot for your kind supports and sorry for killing your time. I still have some issues and need your help

Twin paradox

I read and also tried to understand the figure you shared. As I can understand, Bob using one atomic clock in the ground and Alice was another at the spaceship. Bob and Alice were celebrating their birthday based on the clocks with them. However, they were not celebrating their 21st birthday on the same time.

Please let me know, if I am wrong.

Also please help me to understand following issues

Atomic Time:

The International System of Units (SI) defines one second as the time it takes a Cesium-133 atom at the ground state to oscillate exactly 9,192,631,770 times.

This measurement is at the ground state. Can extreme velocity and gravity change the rate of this oscillation?

The Muon Half Life:

The muon is unstable and decays into other particles. It has a half-life of about of 2.2 μs (microseconds) when measured at rest in the laboratory. Muons are created in the high atmosphere when cosmic rays strike the air. When created they have a speed of about 0.99C.

Half-life is the chemical property of unstable elements. Can extreme velocity (0.99C) change it?

Dear Shahab Uddin,

Particles have a clock driven by the Planck’s vacuum (Compton’s clock). When they are at rest (or viewed from its own reference frame), it consists of random circulations at the light speed (Schrödinger’s zitterbewegung), forming a spherical shell whose radius is the Compton’s one (the so-called vacuum induced fluctuations); all that in full agreement with SPIN-1/2. Inexorably, it means that such particles are massless elementary electrical charges entangled (or continually entangling) with zero-point radiation (second Planck’s radiation law). Such massless charged field (or Higgs field) evolves at the speed of the entangled zero-point radiation (light speed), regardless of the ordinary motion of bodies. Hence, if violations of the light speed are imminent (as expected from the inherent ordinary composition of velocities), then, inevitably, they are compensated by some emerging mechanism (de Broglie’s periodicity evidencing a phase velocity violating the light speed), given that violations of the light speed are not observed, despite gauge invariance of electrodynamical laws predicting a spontaneous breaking of symmetry, at this very stage of the theoretical calculations. This emerging mechanism — longitudinal contraction of the fluctuating spherical shell occurring in order to avoid violations of the speed of the entangled radiation — cause a retardation of the internal clock of particles. Therefore, particles in different reference frames with non-zero relative velocities, physically, must present different internal clocks (Hafele-Keanting experiment).

o

Thanks a lot Fernando Ogiba

"Time is for Clock or Clock is for Time?

What is time? Time is absolute or relative?What is time dilation? According to definition in ‘Encyclopedia Britannica’, “Time dilation ......."'

According to a standard definition in physics: "Time in physics is defined by its measurement. Time is what a clock reads. In classical, non-relativistic physics it is a scalar quantity and, like length, mass, and charge, is usually described as a fundamental quantity."

According to the theory that I ascribe to time is a measurement of change in matter. To measure it one must have a measuring device which we call a clock. Clocks can be imprecise, such as a sun dial, or very precise like an atomic clock of some kind.

The rate that time changes can vary according to the surroundings and relative motion of the matter being timed, therefore time is relative. This effect is time dilation via relative motion to the gravitational center of its surroundings.

Time-dilation is a description of a slowing rate of change in matter relative to a standard.

For instance, matter having a high velocity relative to the center of gravity which influences it, will slow down its internal changes, such as the rotation of the nuclei, orbital speeds of its electrons, etc. Time is the measured rate of change. Time also dilates according to its relative distance from the gravitational center of its surroundings. For instance, on the surface of the Earth time passes more slowly than when the matter is halfway between the Earth and the Moon.

These are the two well known ways that time dilates, by high velocities, and by gravitational influences. A third type of time dilation is observed by the radiation of type 1a supernova. Through study we have realized that these type of supernova events all have a similar light curve whereby the length of time they are observable within two standard deviations of their peak luminosity, is almost constant. This being known they have found there is a precise correlation between this time and the distance of the supernova. For instance when the supernova has a redshift of 2, its light curve lasts almost exactly twice as long.

This third type of time dilation has been called time dilation via distance.

The standard explanation of this is that space has expanded, therefore the light waves were stretched to twice there normal length, so the supernova event will last twice as long. I, on the other hand, ascribe to a different hypothesis, that time actually ran more slowly in the past therefore we observe the real-time of the event, but relative to our time frame, the time would be dilated. From this perspective space and the universe would not be expanding, and time dilation in the past would be real.

Quantum mechanics proposes that time can go backwards. This IMO is one of the many ways in which its logic, or lack thereof, has been dominated by its mathematics.

Although the explanation above is long, the corresponding definition of time to the explanation would be very simple. Time would accordingly be "a measurement of change relative to a standard," no more than this. The instrumentation of these measurements would be called a clock. Time accordingly would be a human dimensional concept, a forth dimension, to practically and mathematically organize reality like the other three Cartesian dimensions.

Dear Shahab,

SU: The Muon Half Life: The muon is unstable and decays into other particles. It has a half-life of about of 2.2 μs (microseconds) when measured at rest in the laboratory. Muons are created in the high atmosphere when cosmic rays strike the air. When created they have a speed of about 0.99C. Half-life is the chemical property of unstable elements. Can extreme velocity (0.99C) change it?

From the point of view of the muon, it is created then just hangs around while the planet is rushing towards it at close to the speed of light. As measured by an observer who moving alongside it, the muon is at rest and its half-life is the normal value so nothing happens to the muon. for someone on the ground, it appears to be extended due to time dilation, this is what I explained before, it is a geometric projection of the normal lifetime of the muon onto the ground observer's worldline.

SU: Twin paradox. I read and also tried to understand the figure you shared. As I can understand, Bob using one atomic clock in the ground and Alice was another at the spaceship. Bob and Alice were celebrating their birthday based on the clocks with them. However, they were not celebrating their 21st birthday on the same time.

The important point here is what you mean by "at the same time". What we understand from relativity is that there is no absolute meaning for that phrase. If you use my interactive page and adjust the slider so that a worldline is vertical, then "at the same time" means events lying on a horizontal line on the chart. If you have Bob's line vertical, then read across from his 30th birthday (10 dots up from when Alice departs), you'll see it is "at the same time" as Alice's 28th birthday when she turns round to return, the time dilation factor is 0.8. Now move the slider or type 0.6 in the box. Alice's outbound worldline is vertical and if you draw a horizontal line from her 28th birthday it crosses Bob's worldline 6.4 years after she left Earth (her 8 years times the dilation of 0.8). Those are "at the same time" as far as Alice is concerned.

SU: Atomic Time: The International System of Units (SI) defines one second as the time it takes a Cesium-133 atom at the ground state to oscillate exactly 9,192,631,770 times. This measurement is at the ground state. Can extreme velocity and gravity change the rate of this oscillation?

Velocity has no effect, as for the muon. Gravity is more complex but the basic idea is the same, the geometry is complicated because it includes curvature so rather than thinking of straight lines on a flat sheet, you have to think of something equivalent to great circles drawn on a sphere, but in four dimensions instead of two. As measured locally, the clocks are not physically changed, but there is a difference in rate for a remote observer. In the GPS system for example the orbiting clocks are measured to run 45 microseconds per day faster due to gravity but 7 microseconds per day slower due to their speed. Within the satellites though, they are operating perfectly normally.

Shahab, this stuff is not too hard once you understand it but it does take a fairly major shift in the way you look at time and space to make sense of it..

Dear Forrest Noble Thanks a lot for your very simple and precise definition of time " Time would accordingly be "a measurement of change relative to a standard," no more than this. " Not only the definitions, I liked the whole writing very much. Thanks a lot Sir.

Dear George Dishman Thanks a lot for all of your efforts and time . I agree with your comment " a fairly major shift in the way you look at time and space to make sense of it ". Hope I can learn more clearly from all the writings from you you and Forrest Noble

My pleasure Shahab. Regrettably, what Forrest wrote is somewhat difficult to follow accurately though not wrong, you would do well to lay aside that post until you have understood the geometric cause of time dilation, then look back at his comments to see some applications of it. Similarly the post of Fernando describes a personal viewpoint, not compatible with current science.

Witout Time no Clock is required.

Time as an ordering relationship 'past-now-future' comes from the very problem statement: we are speaking of something that we still want to reach as being in the future and of past as of what cannot be changed. Quite another thing is the measure of time: seconds, years etc. Conventionally, time was measured (just like length) according to some standards. Zeno, Aristotle, Newton, Einstein and many others discussed the heavy problem of what is genuine time flowing by itself and independent of artificial clock reading. However in physics (not in life!), it is possible to completely dispense with time(clocks) and distance (rods) measuring. More details might be found in my book 'Irony of the Method'.

Dear Shahab Uddin

Time is a great conceptual invention of human being to measure change. It is like paper money, it measures the value of change, but it doesn't have any value of its own. A duration of time, which is defined a segment from the past to future, is impossible to exist at the same time. What exists is the ever changing present. Einstein define time as "by substituting 'the position of the small hand of my watch' for 'time.'" "http://hermes.ffn.ub.es/luisnavarro/nuevo_maletin/Einstein_1905_relativity.pdf