"Time" not a dimension.

[lilphil1989]

You can't, look at the twins paradox.

As far as the twin travelling at light is concerned time feels normal and any clock on the spacecraft will show the same. But as far as his brother is concerned he has slowed right down.

In the theory it is usually considered that time(as a seperate demension) has slowed down.

The twin paradox isn't a paradox. It arises from a naive formulation of the problem as symmetric between the the earth twin's frame and the travelling twin's frame. The problem is that in order to return to earth, the travelling twin has to make a lorentz boost to move to the frame in which he returns, so that there are 3, not 2 relevant frames in the problem, and you can't just claim that each sees the others time dilated by an equal amount.
What happens then is that the travelling twin "sees" the home twin age very quickly when he turns around, because his definition of simultaneity with the unmoving twin changes when he lorentz boosts to the return frame. The travelled twin will be younger than the twin that stayed on earth.
This is confirmed experimentally: New Scientist, Feb. 1972

But it could be equally said that the physical interactions have been stretched out(a bit like red shift)

So it only appears that time has slowed down.

I'm not quite sure what you mean by this.
What would be the difference between the two empirically?

[reverendjeremiah]

It sounds like a play on the particle/wave veiws of physics.

The physics I understand is electron based and admitedly focused and applied in the electrical trade.

I wish I could give a more indepth opinion on this subject. Time has been shown over and over again to fit well into its classification as a fourth dimension.

[Zenith]

This is an interesting article, new research suggests that measurements of time are not measurements of a dimension but of the numerical order of events in space:

"The concept of time as a way to measure the duration of events is not only deeply intuitive, it also plays an important role in our mathematical descriptions of physical systems. For instance, we define an object’s speed as its displacement per a given time. But some researchers theorize that this Newtonian idea of time as an absolute quantity that flows on its own, along with the idea that time is the fourth dimension of spacetime, are incorrect. They propose to replace these concepts of time with a view that corresponds more accurately to the physical world: time as a measure of the numerical order of change."

http://www.physorg.com/news/2011-04-scie...nsion.html

I also believe that time is the order of events, and that that's all. We did not create time, we invented it. There is no "beginning of time" and "end of time". Perhaps this idea with time being something as an object or another dimension draws from SF movies and imagination with time-traveling, portals in time, etc. which I believe are impossible (after all, we did not prove "time" to be an object or something).

Numerical order of things seems to be an artifact of the perception of time, and does not address at all the fundamental nature of time. Why for example do the numerical order not count backwards? What explains why appearently truly random events like radioactive decay is still perceived as an ordered series of events?

Why do the numerical order not count backwards? Well, I think it's like saying "why do we count 1, 2, 3, 4 and not -1, -2, -3, -4". It's we who invented the counting. If there is no "time" like an object, an entity or a dimension, then it's just events, one after another. As about the second question, I don't understand it too well, what it has to do with "time".

What happens then is that the travelling twin "sees" the home twin age very quickly when he turns around, because his definition of simultaneity with the unmoving twin changes when he lorentz boosts to the return frame. The travelled twin will be younger than the twin that stayed on earth.

From what I've read from there, it seems that atomic clocks were used. So the question is, what if something influences in some way the atomic clock? Isn't that easier to believe than to say that the time itself has been influenced?

P.S. I do not have advanced knowledge of physics, so if I did a big mistake or something, I expect you to understand.

[Zenith]

P.S. As about the idea that time is the 4th dimension, something is odd: all other three dimensions are measurable in meters (not seconds, grams, joules, etc.). You know, if you put a cube in a 3d world, with the margins parallel to the axis, you check its sizes this way: width, in meters, by checking the X axis; height, in meters, by checking the Y axis; and the depth (or how that's called), in meters, by checking the Z axis. They're all measurable in meters, so why should the 4th be measurable in seconds?? Also, what if there are only 3 dimensions? (if so, then perhaps we should not struggle to add a 4th non-meter-measurable dimension).

[Anymouse]

I would recommend the 1884 novella by English schoolmaster Edwin Abbot Abbot (yes he's double the Abbot of an abbot), Flatland: A Romance of Many Dimensions.

In his novella, he expounds on the idea of many physical dimensions with characters in a fictitious two-dimensional universe that are visited by a sphere.

James

[lilphil1989]

From what I've read from there, it seems that atomic clocks were used. So the question is, what if something influences in some way the atomic clock? Isn't that easier to believe than to say that the time itself has been influenced?

It's not that time has been influenced as such (indeed, relativity threw out the concept of "the" time), rather the defintion of simultaneity associated with the rest frame of the moving clock has changed. Remember, one of the important results of special relativity is that there is no such thing as absolute time, and if you and I see two events as simultaneous, then someone in motion relative to us will see one happen before the other.

P.S. As about the idea that time is the 4th dimension, something is odd: all other three dimensions are measurable in meters (not seconds, grams, joules, etc.). You know, if you put a cube in a 3d world, with the margins parallel to the axis, you check its sizes this way: width, in meters, by checking the X axis; height, in meters, by checking the Y axis; and the depth (or how that's called), in meters, by checking the Z axis. They're all measurable in meters, so why should the 4th be measurable in seconds?? Also, what if there are only 3 dimensions? (if so, then perhaps we should not struggle to add a 4th non-meter-measurable dimension).

This is a common misconception. I blame pop-sci authors and their often sloppy explanation of concepts in order to make them "accessible".

No-one is saying that space and time are "the same thing", indeed if that were the case we'd only need one of those words! But, since the Lorentz transforms (the basics objects of special relativity) mix space and time into one another, it is useful conceptually to think of space and time making a four dimensional vector space so that Lorentz transforms can be though of as rotations in this space.
And actually it's quite easy to measure a time interval in metres, just multiply up by the speed of light.

[Anymouse]

One might also note that in the experiment which "showed" frame-dragging, the observation was not of time itself, but on machines which measure it.

[lilphil1989]

One might also note that in the experiment which "showed" frame-dragging, the observation was not of time itself, but on machines which measure it.

GR made a prediction about what would be seen, which was confirmed.

Is such a concept as "observation of time itself" even meaningful?

[Anymouse]

It sounds like a play on the particle/wave veiws of physics.

The physics I understand is electron based and admitedly focused and applied in the electrical trade.

I wish I could give a more indepth opinion on this subject. Time has been shown over and over again to fit well into its classification as a fourth dimension.

I am an amateur radio operator and have been an aviation electronics technician in the US Navy in my checkered past, before editing Romance novels nowadays.

Even so, an electron-based view of electronics breaks down at the antenna or waveguide of a wireless set or radar: from there into space it is E and H waves, not electrons.

But since one cannot see electrons, or radio waves, (just their alleged effects on instruments), one might presuppose there is only circumstantial evidence for their existence.

'Lectronics is magick to most people: they pull out the knob of a telly, and poof! pictures and sound. They have absolutely no idea how it happens other than the correct ritual movements. (Pointing a magic "wand" [remote] and pushing a button, or getting up and pushing or pulling one.)

While I understand how a telly works, I doubt I could put it into language a non-technical person could fully understand; from his point of view I am just mumbling arcane and occult knowledge.

That and I have government permits that allow me to practice the rituals of ham radio and ship and aircraft radio and radar operation and repair, when I am not working on a new bodice-ripper.

James.

[orogenicman]

I'd like to add some thoughts here. The Gravity Probe B has confirmed Einstein's General relativity. Just thought I would point this out.

http://physics.aps.org/articles/v4/43

According to Einstein’s theory, space and time are not the immutable, rigid structures of Newton’s universe, but are united as spacetime, and together they are malleable, almost rubbery. A massive body warps spacetime, the way a bowling ball warps the surface of a trampoline. A rotating body drags spacetime a tiny bit around with it, the way a mixer blade drags a thick batter around.

The spinning Earth does both of these things and this is what the four gyroscopes aboard the earth-orbiting satellite Gravity Probe B measured. The satellite follows a polar orbit with an altitude of 640 kilometers above the earth’s surface (Fig. 1, top). The warping of spacetime exerts a torque on the gyroscope so that its axis slowly precesses—by about 6.6 arcseconds (or 1.8 thousandths of a degree) per year—in the plane of the satellite’s orbit. (To picture this precession, or “geodetic effect,” imagine a stick moving parallel to its length on a closed path along the curved surface of the Earth, returning to its origin pointing in a slightly different direction than when it started.) The rotation of the Earth also exerts a “frame-dragging” effect on the gyro. In this case, the precession is perpendicular to the orbital plane and advances by 40 milliarcseconds per year. Josef Lense and Hans Thirring first pointed out the existence of the frame-dragging phenomenon in 1918, but it was not until the 1960s that George Pugh in the Defense Department and Leonard Schiff at Stanford independently pursued the idea of measuring it with gyroscopes.

More at the link.