Is there the possibility of absolute time

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    Absolute Time
  • #51


hartlw said:
Taking into account relativity, no matter how small the effect, how do you calculate the acceleration of a box sliding down a frictionless plane.
Easy, use Newton's 2nd law, f=dp/dt. You can use 3-vectors for the Newtonian version or 4-vectors if you want to be anal about it and include the SR corrections, but the law is the same in either case.

The point is that time is not absolute because you can analyze the box's motion in a coordinate system where it is released at t=0 or one where it is released at t=13.7 billion years. In either case you can use the same laws to calculate the same result.
 
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  • #52


hartlw said:
Create a frame in a vacuum with a fluorescent marker at an equal distance on each of the three axes. Let a flash of light occur at the origin. If the observer at the origin sees all the flashes return simultaneously, a repeatable time interval, clock, is established in this frame. Define this particular frame and the distance and time interval as absolute. Proceed from there.
This is absurd.

Create an identical frame moving inertially wrt the first. Perform the same procedure. Now you have two different sets of "absolute time" that disagree with each other.
 
  • #53


Refer the second to the first. Or make the second absolute. Then refer the first to the second.
 
  • #54


Perhaps an agreed definition of absolute time may be useful here.

Matheinste
 
  • #55


hartlw said:
Refer the second to the first. Or make the second absolute. Then refer the first to the second.
Do you not see the blatantly obvious problem here? As you noticed there is no physical basis on which to choose one over the other. Therefore neither can be absolute.
 
  • #56


matheinste said:
Perhaps an agreed definition of absolute time may be useful here.

Matheinste

Since such a definition cannot by dint of SR model reality it is superfluous, like I say and Dalespam^ is also saying the definition given is useless. In fact any Galilean time as it's sometimes called is not what we observe in the real world nor it seems ever could.

People need to understand what is meant by there are no discreet frames of reference.

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

Reference frames, coordinates and the Lorentz transformation

Relativity theory depends on "reference frames". A reference frame is an observational perspective in space at rest, or in uniform motion, from which a position can be measured along 3 spatial axes. In addition, a reference frame has the ability to determine measurements of the time of events using a 'clock' (any reference device with uniform periodicity).

An event is an occurrence that can be assigned a single unique time and location in space relative to a reference frame: it is a "point" in space-time. Since the speed of light is constant in relativity in each and every reference frame, pulses of light can be used to unambiguously measure distances and refer back the times that events occurred to the clock, even though light takes time to reach the clock after the event has transpired.

For example, the explosion of a firecracker may be considered to be an "event". We can completely specify an event by its four space-time coordinates: The time of occurrence and its 3-dimensional spatial location define a reference point. Let's call this reference frame S.

In relativity theory we often want to calculate the position of a point from a different reference point.

Suppose we have a second reference frame S', whose spatial axes and clock exactly coincide with that of S at time zero, but it is moving at a constant velocity v\, with respect to S along the x\,-axis.

Since there is no absolute reference frame in relativity theory, a concept of 'moving' doesn't strictly exist, as everything is always moving with respect to some other reference frame. Instead, any two frames that move at the same speed in the same direction are said to be comoving. Therefore S and S' are not comoving.
 
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  • #57


hartlw said:
Define this particular frame and the distance and time interval as absolute. Proceed from there.

You have to be practical. Like the std meter and the std mass.

Accelerate the std meter in Paris to .75c and then call it the standard (absolute) meter. The real problem is communicating (measuring) between frames. An absolute reference allows you to do this. Just define one as absolute.
 
  • #58


hartlw said:
You have to be practical. Like the std meter and the std mass.

Accelerate the std meter in Paris to .75c and then call it the standard (absolute) meter. The real problem is communicating (measuring) between frames. An absolute reference allows you to do this. Just define one as absolute.

You can't it's one of the fundamental laws of SR, that's the point. If you could then it would destroy SR, and Einstein's theory would be thrown in the trash.

The problem is that to understand why you need more than a cursory understanding of special relativity. But reading any link or book on it will establish why quite completely such a concept is fundamentally flawed, if you understand the maths it will be even more obvious. yes you could define an absolute, but it would be only practical in philosophy because space-time simply doesn't work that way and never has to all appreciable understanding. Thus even knowing when time began precisely, if you even could would be worthless, unless you are God and are not subject to the laws of nature but exist outside of them.

You have to be practical and that is it in a nutshell, to all practical intents such an arbitrary concern is worthless.
 
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  • #59


I agree with you The Dagda. Such a thing as absolute time does not exist in SR and so is undefinable in SR. However hartlw obviously has his own example of what he considers to be absolute time so it may be worth asking for his general definition rather than a specific example.

Matheinste.
 
  • #60


matheinste said:
I agree with you The Dagda. Such a thing as absolute time does not exist in SR and so is undefinable in SR. However hartlw obviously has his own example of what he considers to be absolute time so it may be worth asking for his general definition rather than a specific example.

Matheinste.

Sure I have no problem with that as long as we understand it is philosophy in its purest sense because it is pure abstraction and pure maths. :smile:
 
  • #61


The most general definition I can think of is absolute time is the distance of a spherical light wave from its center.
 
  • #62


If we want to totally abstract ourselves from reality then time, distance, and mass are symbols with certain mathematical properties.
 
  • #63


hartlw said:
If we want to totally abstract ourselves from reality then time, distance, and mass are symbols with certain mathematical properties.

Ah but then I feel a need for a thread move. If that is the case then are these values independent of conscious thought, or are they a consequence of it? If the former then there is an absolute time, if the latter then not. It would start to move towards an argument over whether maths has always existed or it is an extension of us. That question is messy, but most people believe that maths is conscious dependent, or put another way not created by a god, or the universe. What is is, it is fundamentally written into reality, and maths is just our flawed way of getting to grips with it.
 
  • #64


hartlw said:
The most general definition I can think of is absolute time is the distance of a spherical light wave from its center.
And which law of physics is different in such a reference frame?
 
  • #65


DaleSpam said:
And which law of physics is different in such a reference frame?

I assume you mean a reference frame at the center of a spherical wave. Assuming the spherical light wave is not influenced by gravity, my first thought was a frame at the light center should function as an ineertial reference frame, avoiding for now the problem that there is no such thing as an inertial reference frame in the sense that an object in the frame couldn't possibly move with constant velocity unless you assumed there was no gravity field. But there would be no way of knowing if the frame were spinning wrt to the spherical wave of light.

This got me thinking about the Earth spinning about its axis. How does the Earth know its spinning about its axis? Suddenly the explanation struck me:

THE ANGULAR MOMENTUM OF THE UNIVERSE IS CONSTANT. This implies the existence of absolute space and time, starting with an inertial frame fixed at the center of the "big bang," and the CONSTANT equal to zero.
 
  • #66


hartlw said:
I assume you mean a reference frame at the center of a spherical wave. Assuming the spherical light wave is not influenced by gravity, my first thought was a frame at the light center should function as an ineertial reference frame, avoiding for now the problem that there is no such thing as an inertial reference frame in the sense that an object in the frame couldn't possibly move with constant velocity unless you assumed there was no gravity field. But there would be no way of knowing if the frame were spinning wrt to the spherical wave of light.

Isn't one way of getting the metric of special relativity to consider a bunch of inertial frames with light spreading out from a point (eg. their coincident origins at t=0)?
 
  • #67


hartlw said:
I assume you mean a reference frame at the center of a spherical wave. Assuming the spherical light wave is not influenced by gravity, my first thought was a frame at the light center should function as an ineertial reference frame, avoiding for now the problem that there is no such thing as an inertial reference frame in the sense that an object in the frame couldn't possibly move with constant velocity unless you assumed there was no gravity field. But there would be no way of knowing if the frame were spinning wrt to the spherical wave of light.

This got me thinking about the Earth spinning about its axis. How does the Earth know its spinning about its axis? Suddenly the explanation struck me:

THE ANGULAR MOMENTUM OF THE UNIVERSE IS CONSTANT. This implies the existence of absolute space and time, starting with an inertial frame fixed at the center of the "big bang," and the CONSTANT equal to zero.
The angular momentum of the universe is constant in all inertial frames, so this does not imply absolute space or time.

You still have yet to identify any physical law (e.g. Maxwell's eqts.) which is different (i.e. different form or constants) in one inertial frame vs. another. Until you do so you do not have an absolute time or space.
 
  • #68


hartlw said:
THE ANGULAR MOMENTUM OF THE UNIVERSE IS CONSTANT.

And that explains, for me, the rotation of the Earth about its axis. It also implies there is the Newtonian Universe (Cosmos) of large objects and small speeds, and the universe of small objects and large speeds. Confusion seems to arise when we put reference frames in between.

I can't get beyond this question. If a light wave is instantaneously emitted from a particle, does it have the speed of the particle? If the aether is "nothing" then it doesn't make sense that it should somehow have the ability to limit the speed of a wave, like water or air does. It makes more sense that light (or EM radiation) would travel with a speed proportional to the energy of expulsion. But then different colors would arrive at different times and so to get them to arrive at the same time you keep the speed constant and put the energy into frequency (color).

Let's assume that a pulse of light is created when an electron jumps from one energy level to another, and it does so with spherical symmetry, and no longer influences the light wave once the process is complete. Then we could have a spherical light wave with an identifiable center.

Two identical particles moving wrt each other emit identical pulses of light at the instant they are at the origin of a coordinate system. What happens? Will the light reach a marker on an axis in the direction of velocity at the same tiime?

In an "aether," yes.

The leading edge of the light wave is created at the instant the electron starts its jump. So regardless of the relative speeds, at this instant the light waves should be identical. The trailing edge of the light wave is created at the instant the electron reches its new energy level. Since one particle has moved with respect to the other, the trailing edges will be spherical but offset. This has some interesting implictions.

But the fundamental question is whether both light waves hit a marker on the axis at the same time. If the leading edges of both light waves are created instantaneously, can the leading edges "know" about the speed of the particle? If not, the leading edges would arrive at the same time but the trailing edge wouldn't.
 
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  • #69


DaleSpam said:
The angular momentum of the universe is constant in all inertial frames, so this does not imply absolute space or time.

An inertial reference frame is one in which an object on which no forces act moves with constant velocity. Where is there a reference frame in which no forces act on an object? You can identify frames in which an object moves with constant velocity, but you can't satisfy the requirement that no forces act on the object, unless you dispense with gravity (the universe).
 
  • #70


Now you are just trying to weasel your way out of answering the question. An inertial reference frame can be defined even in the case where there are no inertial objects considered.

The point remains, as it has for the past 3 dozen posts or so, if you cannot identify a physical law that has a different form or different constants in an inertial reference frame then you have no physical basis for selecting one over another and calling one "absolute". I think it should be clear that there is no such law and you are just trolling.

Don't bother posting unless you can address the core issue.
 
  • #71


Where does mass appear in Maxwells equations?
 
  • #72


Hartlw:
Let's assume that a pulse of light is created when an electron jumps from one energy level to another, and it does so with spherical symmetry, and no longer influences the light wave once the process is complete. Then we could have a spherical light wave with an identifiable center.
I have to split hairs and point out this can't happen. When an electron emits a photon as a result of dropping to a lower energy level in an atom, it is emphatically not a spherical wave. Einstein describes it as a 'needle ray' in his (amazing) 1916 paper.
Momentum is exchanged between the emitted/absorbed quantum. This is the basis of laser cooling of atoms/ions.

I don't know if this affects the point you are trying to make about absolute time.

The idea of absolute time doesn't make a lot of sense when you consider that the only 'time' we know is what is measured on clocks. So there would have to an 'absolute clock' to measure 'absolute time'.
 
  • #73


I have a little problem with Mentz14 reply. If the photon is considered a single "particle", how can it be distributed around the source of light?. If it is a series of "particles" uniformly distributed around the source of light, what happens to the density of the photon around the circumfence of the "wave?". As the photons get further out does the distance between them decrease, or do they spread out so that the photon becomes wider and wider but the number remains the same? I would assume they would get wider, else the light "wave" might miss some objects altogether.
 
  • #74


How about, if light is concentrated in one direction you get a photon? So if you have a spherical wave of light, wrap it around to a single direction and you get a photon.

A spherical wave of light is a photon uniformly distributed spherically.
 
  • #75


Or maybe a single atom doesn't emit a spherical wave. That always bothered me, it would mean the "mass" of the electron is uniformly distributed around it's orbit and its only energy could come from "pulsating.". So it emits a photon in the direction determined by where it starts its jump. The light from a "particle," considered as a collection of atoms, would look like rays, as mentz14 reported about Einsteins article.

The only problem I have with this is the space between photons as distances get large. But the atoms in the particle continuosly and randomly emitting in different directions would address this. You wuld wind up with an average, continuos, weakening density of photons as the light expanded.
 
  • #76
  • #77


Newtonian mechanics identifies an approximate, absolute, inertial reference frame wrt distant stars. By extension, and for practical purposes, any frame moving at constant velocity with respect to this "absolute" inertial frame can be considerded an inertial reference frame.

I am off topic with photons, but I appreciate mentz114 bringing it up, since it has led to the resolution of the wave/particle duality paradox: there isn't any. I feel quite comfortable with them now, making any further discussion unnecessary. Thanks again mentz114, seriously. I appreciate expertise.
 
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  • #78


hartlw said:
Newtonian mechanics identifies an approximate, absolute, inertial reference frame wrt distant stars. By extension, and for practical purposes, any frame moving at constant velocity with respect to this "absolute" inertial frame can be considerded an inertial reference frame.
You sure seem to enjoy making the same mistake over, and over, and over, ...
 
  • #79


Dalespam,

Thanks for your opinion.
 
  • #80


hartlw said:
Newtonian mechanics identifies an approximate, absolute, inertial reference frame wrt distant stars.

Doesn't Newtonian mechanics identify an exact inertial frame as the centre of mass frame? Given the centre of mass frame we can identify an continuous infinity of other inertial frames. So the identification is exact within a mathematical framework that is experimentally known to be an approximate description of nature.
 
  • #81


atyy said:
Doesn't Newtonian mechanics identify an exact inertial frame as the centre of mass frame? Given the centre of mass frame we can identify an continuous infinity of other inertial frames. So the identification is exact within a mathematical framework that is experimentally known to be an approximate description of nature.

No, it is not experimentally known to be anything that's the point, Newton was wrong as was Galileo.
 
  • #82


The Dagda said:
No, it is not experimentally known to be anything that's the point, Newton was wrong as was Galileo.

Now that you've tossed out Newton and Galilea, what physical law explains (actually, describes) the rotation of the Earth about its axis? I take it you accept that as physical evidence?
 
  • #83


hartlw said:
Newtonian mechanics identifies an approximate, absolute, inertial reference frame wrt distant stars.

Taking into account the Hubble law (expansion of the universe) you can't do that: in different parts of the universe these frames are different and moving relatively to each other.
 
  • #84


atyy said:
Doesn't Newtonian mechanics identify an exact inertial frame as the centre of mass frame? Given the centre of mass frame we can identify an continuous infinity of other inertial frames. So the identification is exact within a mathematical framework that is experimentally known to be an approximate description of nature.
Yes, in Newtonian mechanics the center of mass frame of an isolated system is exactly inertial as is any frame moving with a uniform velocity wrt the center of mass frame.

The rather trivial objection that hartlw was raising is that there is no such thing as a truly isolated system. The objection is trivial because, given a non-isolated system of mass M with force F acting on it, then an inertial frame is simply one where the center of mass is accelerating at a=F/M.
 
  • #85


hartlw said:
Now that you've tossed out Newton and Galilea, what physical law explains (actually, describes) the rotation of the Earth about its axis? I take it you accept that as physical evidence?

Einstein's theory of general relativity? Why?
 
  • #86
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  • #87


Just notified of this in my email so I thought I'd comment.

Absolute time is ANY definition of time, ANYWHERE, and a method of synchronization.

The definition of time in Maxwell's equations and on Earth is as good as any. For a synchronization method see posts 34 & 35 in the thread

http://www.advancedphysics.org/forum/showthread.php?t=11435

where it is assumed that the speed of light in vacuum is constant wrt SOURCE.

Relativity, which is wrong, has nothing to do with it. See same thread.
 
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