Nature of Time Dilation and Length Contraction

Tom2,

I have nothing against the concept of relativity. I can understand how physical equations can exist where the absolute properties in them can either negate each other, or can otherwise be superfluous in the equations. For example, gravitational acceleration on the surface of the Earth is equal to around 10 m/s^2 regardless of the mass of the object that is accelerating. In this case, the mass of the accelerating object is superfluous, but that doesn't mean that the object does not have mass. The same thing applies to relativity, just because a property is superfluous in an equation doesn't mean that property doesn't exist.

I would expect to live in a universe in which absolute properties in some physical equations are superfluous, while in others they are absolutely necessary. For example, in an inertial frame of reference, I will admit that the absolute values in most of the physical equations dealing with the interactions in that frame may be superfluous, but that doesn't mean that they all have to be. What I don't understand is the extreme desire of Einstein, and relativists, to make everything in an inertial frame of reference relative. Their desire is so strong, they would even attempt to change the physical properties of space to fit their concept, and to even introduce a new physical property into physics (time).

I must admit, if everything in an inertial frame of reference was relative that would be cool. But some people need to be reminded that science is not the pursuit of "coolness". For example, why can't the speed of light be tied to an absolute property instead of a relative frame of reference? Maybe the speed of light is tied to gravitational fields, or a type of aether that dav57 is suggesting. Let's not forget that the omnidirectional speed of light has only been found to be invariant on the surface of the Earth. If the speed of light is tied to a field or medium that is geocentric, then to assume that the speed of light in all inertial frames of reference is invariable based on measurements done on the surface of the Earth is just plain stupid.

Finally, let me also say that many physical equations have been developed based on measurements that were done in stationairy positions on the surface of the Earth. If light, electric, or magnetic fields have ties to fields or mediums that are geocentric, then many of these equations are not universal, but are only a subset of a larger group of still unkown equations.

 

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Pete,

Then why do you have to change the values of length and time in your equations if only your point of view has changed?

 

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James,

You don't put the apparent height in your equations to figure out how the house interacts with other objects, do you? The difference between the perception of a physical property changing and the actual value of the physical property changing is that when the actual value changes you must put the new values into the equations.

One more thing, what is the proper value of space and time relative to spacetime itself? Does space and time have values that are independent of any observer or frame of reference? Or do they simply not exist until an observer is present?

 

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przyk,

The pressure is caused by force, which is energy. The energy is changing the physical properties of an object.

The relative velocity of an observer does not create enough energy to contract all of the space in the universe in the observer's frame of reference. Nor is there an interaction that can explain how an observer can compress spacetime at a distance (unless it's a new form of quantum entanglement

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Prosoothus, i heard your mother dilated time yester day..

 

Lensman,

First of all, welcome to sciforums. Now to get to some of your comments:

In the example you provided, there is a physical and a perceptual reason for the doppler shift. When a source is moving through a medium and generating a wave in that medium, the frequency of the wave is physically changed as a result of the motion of the source. When the target of the wave is moving through the wave's medium, the frequency of the wave only changes perceptually, and not physically for the target. In other words, the perceptual or physical change of the wave occurs locally at either the source or the target. So, the doppler shift is not a long distance interaction.

When an observer moves, relativists claim that the dilation of time and the contraction of length is physical, and not just perceptual. If it is physical, there is no way to explain how the observer can change, or even interact, with spacetime that is not local to the observer. Since length contraction and time dilation occur in the entire observer's frame of reference, it not only requires an enormous amount of energy, but a long distance interaction as well.

Did time dilate in those clocks, or did the reactions in those clocks slow down independently of time? Maybe the speed of reactions in any object that is moving through a gravitational field slow down, while time stays constant.

 

c7ityi_,

OK. :bugeye: Did your brain contract?

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Frequency contraction is mathematically identical to time dilation. Is a relative change the result of a time dilation or the result of frequency contraction in the clock? For the most part the question is moot, as the measuring of a change in time requires a clock. As Einstein wrote, "In order to measure time, we have to suppose a clock..." (The Meaning of Relativity, pg 27)

Now we could suppose a time which is independant of clocks. But, lacking something with which to measure this independant time, we are left with a concept that has no tangible definition. Without a tangible definition, we ought to exclude the concept from a discussion.

 

Consider it done!

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Is the emission of a photon at right angles to the direction of travel affected at relativistic velocities? Length contraction and momentum of the charged particle come to mind.

 

Hi Montec, welcome to SciForums.

Length contraction only happens in the parallel direction, but time dilation obviously happens in all directions. So a photon emitted perpendicular to the direction of travel of an object moving at relativistic velocity will be "redshifted" from it's proper frequency. This is known as the "transverse Doppler effect". Wikipedia has a nice transverse Doppler article, but it is down right now so I can't post the link.

-Dale

 

Because length and time are not absolute - they are relative components of spacetime, just like forward-backward and left-right in our intuitive model of space.

Here's an example of intuitive relativity:

If I tell you that you can find something by going three steps forward, two steps right, those directions are only useful if you know the right "point of view". In this case, it means knowing two things:
1) Where to start
2) What direction to face


In a similar same way, telling you that an event will happen "3 metres away in 10 seconds time" is only useful if you know the right "point of view", ie the right inertial reference frame.

 

This is one of the silly things that anti-relativityists like to say as though it is some point of great wisdom and insight.

Let's assume, for the purpose of illustrating absurdity, that it is not time, t, which slows down. Instead it is the "speed of reactions", s, that slows down. Now of course, all of our physics experiments are insensitive to the real underlying t that remains constant, but they are sensitive to the observable s that slows down. In fact, they are sensitive to s in exactly the same way as we used to mistakenly think of them being sensitive to t. So we carefully go through all of our physics equations and replace every t or d/dt with an s or d/ds. Voila! Now t doesn't dilate, just s. Wonderful. Of course, now time is a completely useless concept that can have no possible impact on anything, but at least the anti-relativityists are happy because it doesn't dilate.

There are some interesting things about s. Clocks measure it. Things change with respect to it. Etc. In short, it has all of the properties that one would expect of time. So, if we subscribe to the "if it quacks like a duck and waddles like a duck then it's probably a duck" approach, then we may as well call it "time" instead of "speed of reactions". Suddenly the concept of time is useful once again and it can effect things. And, of course, it dilates.

The point is, if you want to call something that doesn't dilate the "real" time then your "real" time has no impact on the real world and is therefore not terribly useful for anyone other than preachers and philosophers. I would much rather stick with my dilating time concept that describes the real world rather than your useless non-dilating time concept that describes nothing.

-Dale

 

DaleSpam,

I've got a wristwatch and it suddenly stops. Now I can assume that the battery died. Or maybe something blocked one of the gears. Or maybe one of a hundred different things went wrong with the mechanism of the watch. But why overcomplicate things? If it quacks like a duck, then it's a duck. It must be that time just stopped in my wristwatch. I call it the "frozen time" theory. My theory states that every couple of years, time stops in all wristwatches on Earth. You see, wristwatches actually use up time and after time is used up in the watch, they just stop ticking. Now, you can always restart the watch by recharging it with a new battery that has more "time" in it, but once that time is used up, you'll have to replace the battery again.

As for atomic clocks moving through gravitational fields, there is absolutely no possibility that any part of their complex mechanisms are actually effected by their motion through a gravitational field. That would be way too complicated. It's much easier to just assume that time is dilating and length is contracting in the clock's entire frame of reference. If it quacks like a duck, then it's probably a duck. Who needs Occam's razor anyway?

 

Dalespam,

The point here is that we’re trying to get to understand the reality of the universe and find out how things really work. If we just shrug our shoulders and accept notions of dilating time and apparent contracting lengths without exploring other possibilities then how can we possibly move forwards? We all know that science has hit a brick wall with regards to addressing a number of as yet unanswered questions.

What is wrong with discarding time as being a valid variable in our equations? Perhaps, more people should begin to think of clocks as being nothing more than a comparison of one set of arbitrarily chosen oscillations compared to another set. This way, it might prompt some of our best brains in science to make a link with gravity using this physical, aether-like substance. Physics Monkey is right. There is nothing wrong with replacing space-time with a similar dynamic aether substance which has all the properties of space-time. But there could be an intrinsic link with gravity too, and why can’t gravity be a result of the interactions between mass and the physical aether?

I can’t believe why science has shunned the aether models so easily just because of the MM experiment! DYNAMIC, REAL, PHYSICAL, COMPRESSIBLE aether is a very real possibility and this aether could easily affect the way clocks etc behave when moving through a gravitational field or positioned close to one.

Time, as I said, is nonexistent. Nobody can prove time to exists because the concept of time is nonsense, The universe does not require “time” to evolve. All that is needed is an unfolding of actions and reactions between physical entities, one after the other. Who needs time? Prove to me time exists. You can’t.

Why do relativists keep saying “ what’s the point in thinking of things in a different way?” Because we need to understand mass, gravity, inertia, make a link between QM and Relativity, find out why light is invariant, etc, that’s why!

 

Quick question, what absurbity did you intend to point out? Was it that time has no tangible definition if it is independant of a clock? Because when I look at your post prior to, "Suddenly the concept of time...", I see an argument against the use of the term time if one replaces "if it quacks like a duck and waddles like a duck then it's probably a duck" with Ockham's razor. But perhaps more to the point, when you consider the concept of time, do you think of a period of oscillations in a device, or do you think of that which the period measures?

 

I know this wasn't addressed to me, but, there is nothing wrong with discarding time as a valid variable. There is also no cause to do so, as t would need be replaced with some other variable which has the same use.

It would definately cut down on the fruitless debates if everyone was on the same page. Think of it this way, when a scientist measures time, he uses the second. If you look at the SI definition of the second, you will find, "The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom." Which is a set of "arbitrarily chosen oscillations". Now you are on the same page with scientists. Now all that is required is to train scientists to accept that you are on the same page as them looking at things from a different perspective.

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Not sure what you mean by this - I've never heard of energy "doing" anything. It's just a state function that has the useful property of being time invariant. This allows certain problems to be solved quickly (provided certain assumptions are made about the final state), without having to resort to complicated curvilinear integrals. Unless I'm missing something, energy is nothing more than a neat mathematical trick.

I wouldn't use the concept of force as an explanation for anything either. Unless you're told that a mass is set up in such a situation that the "force" acting on it is, say, 10N, you have to work out what the force will be, which usually depends on its location in relation to other objects. You equate m*a with a function of the object's position and effectively eliminate the force from the equation. What you end up with is a relation between an object's position and acceleration, for no apparent reason. Even if you bring in force carrying particles, you haven't expained why the particles affect each other at all, instead of simply flying past or through one another.

The point is that every theory or model can be traced back to its own set of fundamental, 'unexplained' postulates from which everything else can be derived. There's no way of avoiding this. You simply can't have a self-evident theory.

 

The article at Wikipedia discusses "time dilation" and its affect on EM waves. Good article. Thanks.
I'm still looking for info relating to "length dilation" and its affect on EM emissions. IE How does a dipole emitter react to length contraction?
My other question relates to momentum of a charged particle in an accelerated frame. IE Will a particle be predisposed to move at right angles to the direction of travel or not?

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When you expect inane comments from the anti-relativity crowd you are almost never disappointed. Clocks can break, ergo there is no time dilation. Nice non-sequitur there Prosoothus. Come to think of it, rulers can break too, so length contraction must be wrong too. Scales can break too, so ...

I always get a kick out of you guys who bring up Occam's razor. That is one of strongest arguments in favor of SR. SR has exactly 2 postulates. I suppose you have a theory that can make all of the correct predictions that SR makes, doesn't require time dilation, and only requires 1 postulate? If so I highly recommend you submit it to an academic journal, it will be a big hit!

-Dale