Time

FISMA

Correct me if I am wrong, however in the never ending battle between the Quantum crowd and Einstein, Albert still occupies the intellectual high ground when it comes to time.

That is, time is still continuous.

I am just wondering whether you think time is continuous, quantized, or something else.

Please comment on any current research, what your instincts tell you, or what not.

Moving into meta-Physics...

... I have this gut feeling that says time is not continuous. But if so, what would that mean for a living being?

Anyone know much about the chronon? Are we knocking on its door or is it more proposition than experimentation?

Professor_Fink

It's already understood how to do relativistic quantum mechanics, and as in normal relativity time and space have the same status (modulo the metric). I think perhaps you misunderstand the status of space in quantum mechanics. It's what is called a continuous variable. So even though different spacial modes are orthogonal, space is still continuous. The same is true for time.

Morbert

As mentioned above, the problem is not time per se (the spacetime of special relativity is consistent with quantum mechanics, under quantum field theory). The problem is, in general relativity, spacetime is a dynamical field. Space and time are just facets of the gravitational field, which implies that the dynamics of this field, like others in quantum field theory, should be quantized. Normally fields are quantized with "creation/annihilation operators" but these operators imply a background spacetime, so they cannot immediately be used to quantize spacetime itself.

It also doesn't help that experiments cannot yet probe regimes where both theories are relevant, so we continue to have two theories which consistently pass experimental tests, but are incompatible on a fundamental level.

MonkeyDoo

My gut feeling would be that time is discrete rather than continious. My pseudo-reasoning if you could call it that....

In a blackhole nothing can move because gravity is so strong, As nothing can move time is also stopped.

Time can only be measured with reference to something changing position? If nothing moves time stays still?

I am assuming measuring tiny amounts of time would be dependent on measuring movements at a quantum level. There is no in between levels. So time measurement would be discrete rather than continious.

If everything stays in the same position,there is no time..If the smallest movements occupy specific quantum positions,then I would guess time would have some emergent quantum or discrete properties.

I would like to think there is some smallest unit of time...something in the universe had to move first, maybe that movement is the smallest unit of time...

himnextdoor

I think that time is 'caused' by the expansion of the universe.

Today the universe is bigger than it was yesterday and tomorrow it will be bigger than it is today.

On that basis, time-travel would have to involve shrinking or expanding the entire universe depending on whether you wish to travel backward or forward in time. The amount of energy required to achieve this suggests to me that time-travel is not possible.

Professor_Fink

himnextdoor wrote: »

I think that time is 'caused' by the expansion of the universe.

Today the universe is bigger than it was yesterday and tomorrow it will be bigger than it is today.

That's not quite how it works. There is no absolute time (it's basically the first thing we get from relativity), yet it is implicit in your picture. In reality, different observers experience differing degrees of time dilation, so it doesn't make sense to talk about the universe as a whole 'today'. Rather, you can only talk about how, for example, we observe the universe today (i.e. in our reference frame), and what we do see contains some very old parts as well as some very new parts. So, the continued expansion of the universe isn't what gives rise to time, and time could carry on even if the universe began to contract (from our perspective).

himnextdoor wrote: »

On that basis, time-travel would have to involve shrinking or expanding the entire universe depending on whether you wish to travel backward or forward in time. The amount of energy required to achieve this suggests to me that time-travel is not possible.

First off, I do not believe time travel is possible. However, you are wrong in your reasoning about how it could happen or why it is impossible. In general relativity there are structures which can allow for time travel (though I do not for a minute believe that our universe contains such structures). The most well known of these is an Einstein-Rosen bridge (wormhole).

If you think of spacetime as being the surface of a table cloth, such a structure is like what you get if you cut out two circles from the table cloth and then sew in a tube between them. How could this allow time travel? Well, massive particles (like you or I) are restricted to move along timelike path.

Imagine for some particular observer we identify one direction on the table cloth with time, and the other with space. The movement of any particle then must obey the following rule. When a particle is at point P, it can only subsequently be at a point Q if the angle from P to Q is between -45 and +45 degrees (with 0 being straight forward in time). This is called a timelike path.

For a normal table cloth, it should be clear that following this rule will mean that if Q lies behind P (i.e. back in time from P) then it cannot be reached from P along such a timelike path.

However, if you have this extra tube, as I described, with mouths at A and B, such that A is behind Q which is behind P which is behind B, then there does exist a closed path obeying the timelike rule I outlined above. This is simply P-B-following the curve of the surface into the wormhole-A-Q. Thus there is a timelike loop passing through all 4 points, allowing you to reach any point from any of the others (and hence allowing what might be called time travel). These are called closed timelike curves, and are not dependent on the larger structure of the universe (i.e. diameter of the visible universe etc.).

However, I would like to stress that while such objects are mathematically consistent with general relativity, there is no evidence that they actually exist naturally in our universe, and no plausible way of creating them.

himnextdoor

Professor_Fink wrote: »

There is no absolute time (it's basically the first thing we get from relativity), yet it is implicit in your picture.

I don't mean to be argumentative, (or maybe I do), but consider the case of two near earth objects, say a couple of small asteroids, one with a high velocity and one with a low velocity travelling along the same line through space. Obviously the slower of the two objects will be more influenced by earth's gravity than the faster one. Could we say then that earth's gravity is not absolute since it is 'percieved' differently by the two objects?

It may be that a clock on a jet flying at high speed registers longer seconds than a stationary clock on the ground but doesn't that say more about the nature of the components of the clocks than about time?

A pendulum driven clock that is accelerating along the axis of the pendulum's motion could register that no time has passed during the period of acceleration but a stopped clock is not the same as stopped time.

Professor_Fink

himnextdoor wrote: »

I don't mean to be argumentative, (or maybe I do), but consider the case of two near earth objects, say a couple of small asteroids, one with a high velocity and one with a low velocity travelling along the same line through space. Obviously the slower of the two objects will be more influenced by earth's gravity than the faster one. Could we say then that earth's gravity is not absolute since it is 'percieved' differently by the two objects?

No. Both objects experience exactly the same acceleration due to gravity, and so experience exactly the same gravitational field. Their different paths aren't because they 'percieve' gravity differently, but rather simply because faster moving object spends less time in the region where the gravitational field is strongest.

himnextdoor wrote: »

It may be that a clock on a jet flying at high speed registers longer seconds than a stationary clock on the ground but doesn't that say more about the nature of the components of the clocks than about time?

No. The speed of light as measured by both clocks is the same, so it is not the clocks that are at fault. This is absolutely fundamental to special relativity.

himnextdoor wrote: »

A pendulum driven clock that is accelerating along the axis of the pendulum's motion could register that no time has passed during the period of acceleration but a stopped clock is not the same as stopped time.

If all dynamics stop/slow, then it is the same as stopped/slowed time.

FISMA

If you have anyone that is interested in a quick and easy intro to relativity, have them give this link a look.

http://www.onestick.com/relativity/

himnextdoor

Professor_Fink wrote: »

No. Both objects experience exactly the same acceleration due to gravity, and so experience exactly the same gravitational field. Their different paths aren't because they 'percieve' gravity differently, but rather simply because faster moving object spends less time in the region where the gravitational field is strongest.
QUOTE]

No, they DO percieve gravity differently precisely because they spend a different amount of time in the field.

Professor_Fink wrote: »

No. The speed of light as measured by both clocks is the same, so it is not the clocks that are at fault. This is absolutely fundamental to special relativity.QUOTE]

No, under acceleration any physical system will 'feel' a force of compression which would alter its calibration.

If you had a one metre long rod with a transmitter generating a pulsing signal at one end and a reciever at the other end that counted the pulses, then accelerated that rod, the rod would get shorter and the reciever would measure time going by faster than when it was at rest. Or vice versa.

Just to clarify, we are treating gravity and acceleration as being equivalent?

himnextdoor

himnextdoor wrote: »

Professor_Fink wrote: »

No. Both objects experience exactly the same acceleration due to gravity, and so experience exactly the same gravitational field. Their different paths aren't because they 'percieve' gravity differently, but rather simply because faster moving object spends less time in the region where the gravitational field is strongest.

No, they DO percieve gravity differently precisely because they spend a different amount of time in the field.

Professor_Fink wrote: »

No. The speed of light as measured by both clocks is the same, so it is not the clocks that are at fault. This is absolutely fundamental to special relativity.

No, under acceleration any physical system will 'feel' a force of compression which would alter its calibration.

If you had a one metre long rod with a transmitter generating a pulsing signal at one end and a reciever at the other end that counted the pulses, then accelerated that rod, the rod would get shorter and the reciever would measure time going by faster than when it was at rest. Or vice versa.

Just to clarify, we are treating gravity and acceleration as being equivalent?

Professor_Fink

himnextdoor wrote: »

No, they DO percieve gravity differently precisely because they spend a different amount of time in the field.

There is no point in arguing over this. 'Percieve' doesn't make any sense in this context. They are subject to exactly the same force at any given point (assuming they are identical and differ only in velocity). The difference is that the path they take depends on initial velocity.

himnextdoor wrote: »

Professor_Fink wrote:

No. The speed of light as measured by both clocks is the same, so it is not the clocks that are at fault. This is absolutely fundamental to special relativity.

No, under acceleration any physical system will 'feel' a force of compression which would alter its calibration.

And this has nothing to do with time dilation. What I said before was correct. Time dilation is a real phenomenon, and has nothing to do with clocks not working correctly. There is no absolute time.

I know it's weird and counter-intuitive, but it is something we are very sure of. This isn't me expressing an opinion. This is a well established fact.

himnextdoor wrote: »

Just to clarify, we are treating gravity and acceleration as being equivalent?

They are equivalent. It's called the equivalence principle, and is absolutely fundamental to General Relativity.

himnextdoor

Professor_Fink wrote: »

And this has nothing to do with time dilation. What I said before was correct. Time dilation is a real phenomenon, and has nothing to do with clocks not working correctly. There is no absolute time.

Forgive me but isn't the twin paradox a mind experiment and doesn't it preclude us from detecting time-dilation anyway?

My understanding is that any experiments done with clocks at high altitude and speed support the notion of time-dilation but don't necessarily prove it. Can it totally be dicounted that fluctuations in the gravity field accounts for any measured effects?

Professor_Fink

himnextdoor wrote: »

Forgive me but isn't the twin paradox a mind experiment and doesn't it preclude us from detecting time-dilation anyway?

I don't understand what you mean. The twin that accelerates/decelerates is the younger one. I don't see how this could make you think it precludes us from detecting time dilation.

My understanding is that any experiments done with clocks at high altitude and speed support the notion of time-dilation but don't necessarily prove it. Can it totally be dicounted that fluctuations in the gravity field accounts for any measured effects?

No. There are numerous experiments showing this effect. Perhaps the most stiking examples are with decaying particles, where the lifetime of the particle changes according to velocity, exactly matching with time dilation. But yes, there have also been clock-in-plane type experiments which have given rise to non-neglidgable effects.

FISMA

Professor_Fink wrote: »

No. Both objects experience exactly the same acceleration due to gravity, and so experience exactly the same gravitational field.

himnextdoor wrote: »

No, they DO percieve gravity differently precisely because they spend a different amount of time in the field.

HimNextDoor,
The Professor is correct, however, I think I see where the confusion lies.

The Earth has mass. Mass has a property called inertia, we call this inertial mass. Mass also has a property called gravity, we call this gravitational mass. Are they the same? Who knows? To date, no difference has been measured and these measurements are some of the best ever made.

Why does mass have gravity? Who knows? "Why" is for the philosophers. That is does and that it may be studied and correlated - that's for the Physicists.

Anyhow...

Since two masses pull each other we create a theoretical field around the masses. The field is not some thing, it is immaterial. The field is a property of the mass.

Gravitation is a function that is point dependent: it only cares about where you are, not how you got there.

When both objects are located a distance x from the center of the planet, they are in the same gravitationl potential. That is, at a given height above the surface of a planet, both objects will potentially accelerate at the same rate, if allowed to free fall. The old balling ball vs feather experiment.

The more massive of the two will have more gravitational potential energy, however.

Thus, gravitational potential is more fundamental than gravitational potential energy because it is per unit mass.

Also, the gravitational potential does not care if there is a mass in the vicinity. The gravitational potential is always there and is continuous throughout spaceTime.

The gravitational potential due to the field does not care how massive you are or how fast you are going. All it wants to do is speed the body up by [say] 9.0m/s every second.

pvt6zh395dqbrj

Time is a quantised and it has the shape of a cube.

http://en.wikipedia.org/wiki/Time_Cube

MonkeyDoo

Terrell Attractive Bison wrote: »

Time is a quantised and it has the shape of a cube.

http://en.wikipedia.org/wiki/Time_Cube

The Time Pyramid is a probably a more credible project... ;-)

http://en.wikipedia.org/wiki/Time_pyramid

himnextdoor

Professor_Fink wrote: »

I don't understand what you mean. The twin that accelerates/decelerates is the younger one. I don't see how this could make you think it precludes us from detecting time dilation.

I meant that there is no real way to know if the twins actually age at different rates. I accept that clocks count time differently but what is actually being measured? All measurements must have a reference; calibrated to some sort of scale.

Take the experiment with identical clocks at the top and bottom of a water tower; the clock at the bottom ran slightly slower than the clock at the top and has been judged to indicate time-dilation. But does it?

If we replaced the clocks with water boilers then the same results would occur; the water at the bottom would boil more slowly than the water at the top. We can explain this with atmospheric pressure but time-dilation could be a conclusion drawn from such an experiment.

It seems reasonable to say that 'gravitational pressure' is affecting the way that energy is distributed and dissipated by the sub-atomic components of the clocks. And, indeed, in the cells of any travelling twins.

However, the tendency of the universe to expand is not affected by gravity. I would even go so far as to say that gravity is one of the effects of expansion and time is a function of the rate of expansion.

Now, since it is space that is expanding and supposing that energy/mass are manifestations of the stresses caused by the stretching of space it follows that time is independent of gravity. Universal expansion is responsible for all the events that take place within it and governs rates of change. There is nothing that can happen in the universe that can affect the rate of expansion.

Furthermore, there is nowhere in the universe today where it is yesterday.

What is time anyway? Isn't it simply an arbitrary reference to rate of change? An accelerating system still has mass/energy; it still posseses gravity and the space contained by the system will still have vacuum potential. Events such as the swing of a pendulum may take longer to complete under acceleration but there is always a process of change, continuous and ultimately arbitrated upon by the universe's rate of expansion. Absolute time; the only time that cannot be influenced by events in any physical system in the universe.

All I am saying is, why use time-dilation to explain a phenomenon when the principles of atmospheric pressure account equally well for the effect?

Morbert

himnextdoor wrote: »

I meant that there is no real way to know if the twins actually age at different rates. I accept that clocks count time differently but what is actually being measured? All measurements must have a reference; calibrated to some sort of scale.

Take the experiment with identical clocks at the top and bottom of a water tower; the clock at the bottom ran slightly slower than the clock at the top and has been judged to indicate time-dilation. But does it?

If we replaced the clocks with water boilers then the same results would occur; the water at the bottom would boil more slowly than the water at the top. We can explain this with atmospheric pressure but time-dilation could be a conclusion drawn from such an experiment.

It seems reasonable to say that 'gravitational pressure' is affecting the way that energy is distributed and dissipated by the sub-atomic components of the clocks. And, indeed, in the cells of any travelling twins.

However, the tendency of the universe to expand is not affected by gravity. I would even go so far as to say that gravity is one of the effects of expansion and time is a function of the rate of expansion.

Now, since it is space that is expanding and supposing that energy/mass are manifestations of the stresses caused by the stretching of space it follows that time is independent of gravity. Universal expansion is responsible for all the events that take place within it and governs rates of change. There is nothing that can happen in the universe that can affect the rate of expansion.

Furthermore, there is nowhere in the universe today where it is yesterday.

What is time anyway? Isn't it simply an arbitrary reference to rate of change? An accelerating system still has mass/energy; it still posseses gravity and the space contained by the system will still have vacuum potential. Events such as the swing of a pendulum may take longer to complete under acceleration but there is always a process of change, continuous and ultimately arbitrated upon by the universe's rate of expansion. Absolute time; the only time that cannot be influenced by events in any physical system in the universe.

All I am saying is, why use time-dilation to explain a phenomena when the principles of atmospheric pressure account equally well for the effect?

The phenomenon of time dilation is independent of whatever mechanism the clock uses. The result is the same whether your watch uses photons, or particle decay, or any accurate physical process.

Also, time dilation occurs by an amount predicted by relativity. If time dilation is not relativistic, but instead due to the choice of clock mechanism, you would have to explain why the clock simply happens to have slowed down by the amount predicted by relativity.

himnextdoor

Morbert wrote: »

The phenomenon of time dilation is independent of whatever mechanism the clock uses. The result is the same whether your watch uses photons, or particle decay, or any accurate physical process.

Also, time dilation occurs by an amount predicted by relativity. If time dilation is not relativistic, but instead due to the choice of clock mechanism, you would have to explain why the clock simply happens to have slowed down by the amount predicted by relativity.

As far as I know, any notable experiments investigating time-dilation were conducted with atomic clocks all of which rely on atomic processes to count time.

It seems likely that at high enough velocities space itself would offer resistance to matter; that the energy which comprises the moving matter is forced to interact with the vacuum energy and loses energy to it, energy that at rest would have contributed to sub-atomic processes. Those sub-atomic processes are retarded but the system's rate of change doesn't change, it just involves losing extra energy to the vacuum. It is as if it is being supercooled. Does relativity predict time-dilation in supercooled matter? Is supercooling equivalent to gravity/acceleration?

I say yes, in a way it is. If I put a joint of meat in the freezer I am not stopping time from the perspective of the meat, I am forcing it to change its relationship with energy. If uranium were cold enough it would extend its half-life; what's the difference between the uranium and the meat?

And when we heat something up are we accelerating time from the perspective of say, a boiled egg?

The half-life of the decay of muons has more to do with the conditions in which it exists than to do with the passage of time. And it is obviously something about the nature of space that impedes the ability of matter to express energy when it has a high velocity.

While we may use atomic processes in order to assess the passage of time, time is not reliant on these processes and these processes are not reliant on time.

Isn't it reasonable to think of the universe as a vast cavity-resonator whose resonant frequency is a function of its size? As the universe expands, its resonant frequency decreases. At the beginning of time the universe was much smaller and its resonant frequency was at a maximum
and it has been falling ever since. That rate of change, the rate at which the resonant frequency is falling, is the time-base of the whole of existence. If it could be said that the rate of expansion is absolute then wouldn't that allow absolute time?

I might put it this way, if the rate of expansion of the universe was slower than it is now then would the speed of light be affected?

Apparently there is a significant amount of energy in the physicist's equations that is missing from the observed universe and 'dark-matter' was conceived in order to account for it. But even dark matter doesn't balance the equations. Is it inconceivable that space itself is a manifestation of energy, like matter but completely diffuse? Couldn't it be space and its tendency to expand that provides the fuel that drives all the mechanisms of the universe?

I consider that the big bang started a clock that has been ticking at an ever decreasing rate ever since and it is this ticking, the pulse of the universe, that marks time. No amount of gravity or acceleration can influence that clock.

Acceleration and gravity may well affect the rate and method of energy exchange but they have no affect on real time.

Morbert

himnextdoor wrote: »

As far as I know, any notable experiments investigating time-dilation were conducted with atomic clocks all of which rely on atomic processes to count time.

It seems likely that at high enough velocities space itself would offer resistance to matter; that the energy which comprises the moving matter is forced to interact with the vacuum energy and loses energy to it, energy that at rest would have contributed to sub-atomic processes. Those sub-atomic processes are retarded but the system's rate of change doesn't change, it just involves losing extra energy to the vacuum. It is as if it is being supercooled. Does relativity predict time-dilation in supercooled matter? Is supercooling equivalent to gravity/acceleration?

I say yes, in a way it is. If I put a joint of meat in the freezer I am not stopping time from the perspective of the meat, I am forcing it to change its relationship with energy. If uranium were cold enough it would extend its half-life; what's the difference between the uranium and the meat?

And when we heat something up are we accelerating time from the perspective of say, a boiled egg?

The half-life of the decay of muons has more to do with the conditions in which it exists than to do with the passage of time. And it is obviously something about the nature of space that impedes the ability of matter to express energy when it has a high velocity.

While we may use atomic processes in order to assess the passage of time, time is not reliant on these processes and these processes are not reliant on time.

Isn't it reasonable to think of the universe as a vast cavity-resonator whose resonant frequency is a function of its size? As the universe expands, its resonant frequency decreases. At the beginning of time the universe was much smaller and its resonant frequency was at a maximum
and it has been falling ever since. That rate of change, the rate at which the resonant frequency is falling, is the time-base of the whole of existence. If it could be said that the rate of expansion is absolute then wouldn't that allow absolute time?

I might put it this way, if the rate of expansion of the universe was slower than it is now then would the speed of light be affected?

Apparently there is a significant amount of energy in the physicist's equations that is missing from the observed universe and 'dark-matter' was conceived in order to account for it. But even dark matter doesn't balance the equations. Is it inconceivable that space itself is a manifestation of energy, like matter but completely diffuse? Couldn't it be space and its tendency to expand that provides the fuel that drives all the mechanisms of the universe?

I consider that the big bang started a clock that has been ticking at an ever decreasing rate ever since and it is this ticking, the pulse of the universe, that marks time. No amount of gravity or acceleration can influence that clock.

Acceleration and gravity may well affect the rate and method of energy exchange but they have no affect on real time.

What is the proposes interaction between matter and the vacuum energy? What quantifiable predictions does it make? Why postulate it when phenomena like time dilation (whether it be observed in atomic processes, particle decay, light propagation etc.) and length contraction are explained and predicted by the geometry of spacetime?

Furthermore, how does the interaction fit into quantum field theory, which incorporates spacetime geometry to make predictions that have not failed any test so far.

Basically, saying "matter interacts with the vacuum energy" is as useful as saying "matter interacts with donkeys" unless you have a rigorous, predictive, scientific framework for phrasing the hypothesis, and evidence that the hypothesis is true.