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Author Topic: Does Lorentz contraction affect a stationary object that you pass at high speed?  (Read 33317 times)

Offline lightarrow

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Some statements, you tell me if and where you disagree :)

The universe have general macroscopic properties as 'Time' and three 'spatial dimensions'. Inside them we find matter and vacuum and light. Matter and vacuum (space) are defined in/as density and distance. A perfect vacuum is defined as containing no matter nor mass nor density. Distance is defined as being a property relating to what frames of reference we use to compare and measure it with.

Light is measured as a invariant velocity in a vacuum over a certain distance in time. It is also thought to consist of 'light quanta' of a invariant energy amount. Light will always be 'time less' no matter how much it is 'slowed down' as seen from another frame of reference. It is also seen as a 'duality' in that we have experiments proving it to act as a particle as well as waves.
I essentially agree up to here.

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Photons in QED (Quantum Electro Dynamics) are seen as both 'real' photons existing in a continuum in measurable time (Sun Earth) and as 'virtual' photons 'surrounding' atoms and outside measurable time.
Many people says virtual particles are nothing more than a mathematical tool in quantum fields theory and so we shouldn't think of them as really existing.

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Those virtual photons is expected to be responsible for the forces of electricity and magnetism. and also (?) seem to be the carriers of all other 'communication' between particles? A perfect Vacuum, although empty of 'matter', have a hidden 'energy' as well as consisting of virtual particles. Those interact with our macroscopic spacetime although they themselves are of to short duration to become measurable according to HUP (Heisenberg's Uncertainty Principle) and Planck time.
The problem is not much of HUP but of the fact that virtual particles are "out of shell" that is don't obey E2 = (mc2)2 + (cp)2

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So what do we have?

Light/photons/waves acting in a twofold manner, as measurable light and as unmeasurable light, 'timeless' internally but obeying spacetimes geodesics and able to act 'in time' on our universe, existing as a needful property for both living as well as dead matter. A vacuum devoid of matter (if perfect) but not of energy and virtual particles, and also containing 'distances'. Matter which I 'split' in two parts, 'living' and 'dead'.

So what else have I forgotten here?
Billions of things that we'll discover in the (near or far) future...  :)
 

Offline Vern

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Quote from: lightarrow
Many people says virtual particles are nothing more than a mathematical tool in quantum fields theory and so we shouldn't think of them as really existing.
I think this is a very good observation and predict that it will eventually be the accepted hypothesis.
 

Offline yor_on

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Lightarrow, when I write "Those interact with our macroscopic spacetime although they themselves are of to short duration to become measurable according to HUP (Heisenberg's Uncertainty Principle) and Planck time." you say that it hasn't to do with HUP? They are as you say 'out of shell', if you by that mean 'virtual', not being 'consistent in time'? To me it is HUP that best describes it, that and them possibly being 'under' Planck's definitions.
 

Offline lightarrow

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Lightarrow, when I write "Those interact with our macroscopic spacetime although they themselves are of to short duration to become measurable according to HUP (Heisenberg's Uncertainty Principle) and Planck time." you say that it hasn't to do with HUP? They are as you say 'out of shell', if you by that mean 'virtual', not being 'consistent in time'? To me it is HUP that best describes it, that and them possibly being 'under' Planck's definitions.
Virtual particles are not such because they have a too short life, but because they don't obey the equation I wrote in my previous post. It's theyr existence which is allowed by HUP; the property of "being virtual" is "not-obeying that equation".
« Last Edit: 01/04/2009 20:41:45 by lightarrow »
 

Offline yor_on

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That one you will have to go into in more detail to make me see Lightarrow? I'm not saying that HUP is the reason for them existing btw, I'm just finding it a 'best explanation' for how they might exist, and exist they seem to do, even if we just have 'indirect evidence' for them:)
But then again, if they're outside observable time, how would we observe them?

Then again, I do have another view of how it might work, but that one is so outlandish that I'll wait with it :)
 

Offline lightarrow

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That one you will have to go into in more detail to make me see Lightarrow? I'm not saying that HUP is the reason for them existing btw, I'm just finding it a 'best explanation' for how they might exist, and exist they seem to do, even if we just have 'indirect evidence' for them:)
Yes, but that 'indirect evidence' comes from a *specific* way of computing things: perturbation theory, which is only a tool in making approximate computations in QFT, because we still don'y know how to make the complete non-approximate computations; it could come out that virtual particles are not needed at all if we were able to make the complete computation; infact QFT actually  treats quantized *fields*, not particles; it's that quantization what we usually call "particles".
 

Offline Vern

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I found this wiki article that expands on QFT and is in agreement with lightarrow's comments. The last sentence in the quote below gives the reason a virtual particle can never be detected.
Quote from: below
cannot be detected while carrying the force, because such detection will imply that the force is not being carried.

From Wiki

Quote from: the link
In quantum field theory (QFT) the forces between particles are mediated by other particles. For instance, the electromagnetic force between two electrons is caused by an exchange of photons. But quantum field theory applies to all fundamental forces. Intermediate vector bosons mediate the weak force, gluons mediate the strong force, and gravitons mediate the gravitational force. These force-carrying particles are virtual particles and, by definition, cannot be detected while carrying the force, because such detection will imply that the force is not being carried.
« Last Edit: 02/04/2009 13:14:03 by Vern »
 

Offline yor_on

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That one you will have to go into in more detail to make me see Lightarrow? I'm not saying that HUP is the reason for them existing btw, I'm just finding it a 'best explanation' for how they might exist, and exist they seem to do, even if we just have 'indirect evidence' for them:)
Yes, but that 'indirect evidence' comes from a *specific* way of computing things: perturbation theory, which is only a tool in making approximate computations in QFT, because we still don'y know how to make the complete non-approximate computations; it could come out that virtual particles are not needed at all if we were able to make the complete computation; infact QFT actually  treats quantized *fields*, not particles; it's that quantization what we usually call "particles".

What I'm having problems with is 'renormalization' :)
And that idea I've had problem since I first saw it Lightarrow:)
And now you say I will have problems with perturbation theory as well
And quantum field theory too??

Lightarrow, do you remember how dissatisfied I am with my understanding of distance:) If distance is something relating, and only relating, to 'frames' observing 'frames', what is uniform motion, speed, velocity, acceleration? And what the heck is a 'direction'?
And perhaps most importantly, what is time?

We seem to describe things from a format where we expect numbers to come up the same, but our universe seems more likely to conform to a 'sliding standard', where things don't come up the same. Like the way time seems to act in QM as compared to our macroscopic universe. When we 'renormalizes' something we expect it to behave in a accountable manner with a clear 'causality chain' showing from the least to the biggest. Now, isn't that a preconception?
 
 

Offline lightarrow

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That one you will have to go into in more detail to make me see Lightarrow? I'm not saying that HUP is the reason for them existing btw, I'm just finding it a 'best explanation' for how they might exist, and exist they seem to do, even if we just have 'indirect evidence' for them:)
Yes, but that 'indirect evidence' comes from a *specific* way of computing things: perturbation theory, which is only a tool in making approximate computations in QFT, because we still don'y know how to make the complete non-approximate computations; it could come out that virtual particles are not needed at all if we were able to make the complete computation; infact QFT actually  treats quantized *fields*, not particles; it's that quantization what we usually call "particles".

What I'm having problems with is 'renormalization' :)
And that idea I've had problem since I first saw it Lightarrow:)
And now you say I will have problems with perturbation theory as well
And quantum field theory too??

Lightarrow, do you remember how dissatisfied I am with my understanding of distance:) If distance is something relating, and only relating, to 'frames' observing 'frames', what is uniform motion, speed, velocity, acceleration? And what the heck is a 'direction'?
And perhaps most importantly, what is time?
Now you know a little more why the main breakthroughs in physics happens when we understand the basic concepts better :).

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We seem to describe things from a format where we expect numbers to come up the same, but our universe seems more likely to conform to a 'sliding standard', where things don't come up the same.
As to say that one thing is our theory about the world, and another is how the world actually is...

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Like the way time seems to act in QM as compared to our macroscopic universe. When we 'renormalizes' something we expect it to behave in a accountable manner with a clear 'causality chain' showing from the least to the biggest. Now, isn't that a preconception?
Everything, always, is a preconception; nothing more than our mind's creation.
Among these mental creations, the one we call "physics" is the one which works better, that's all.
 

Offline yor_on

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So what do you see as 'virtual particles' Lightarrow? That is what we expect to regulate interactions at a atomic level, isn't it? So is there another idea describing them?


 

Offline wmmarioblogs

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Thanks, Vern. I guessed it would look contracted but I wasn't sure.
 

Offline lightarrow

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So what do you see as 'virtual particles' Lightarrow? That is what we expect to regulate interactions at a atomic level, isn't it? So is there another idea describing them?
In quantum mechanics is difficult to 'see' anything; things become bizarre and far from ordinary experience, physics and mathematics are so linked together that you don't understand where one finish and the other begins...
What we know, or, better, the *description* we have in this moment about microscopic world is that we have fields and these fields have quantized energy. If elementary  particles really exist (and not only the virtual ones) or are merely a useful way to compute things, it's not clear at all, at least to me. Have you ever asked yourself what an electron is? How big it is, how it is done?
 

Offline yor_on

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Oh yes, lightarrow.
And if they really are 'there' too:)

If one see time as shape filling up all of 'spacetime' moving from a 'before' towards a 'future', and you then see what we measure as being motion as instead being 'static prickings' made in 'spacetime',  then we would have 'events' again :)

But the 'events' described here would not be represented of any 'sliced time slots' with 'frames' of no-time between them, instead they would consist of 'frozen static events' that 'times arrow' would create the 'motion' for, even though not really existing. And as time then would be a 'flow' we would have a 'arrow of time' constantly 'moving' creating what we call 'motion and distance'. And then those 'virtual particles' would just be a 'matter' of duration of 'pricking' and the real interest for me would be the transitions we see and try to describe, as f ex Planck length and HUP. Outlandish, isn't it :)
 
 

Offline yor_on

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Vern, quantum gravity theories (QGT) with gravitons? Shouldn't that be String theory, not QFT, in the manner that it is a theory relating to the standard model it is postulated as an idea I know, But it's still just a theory. The Standard Model doesn't, yet, include any quantum gravity, so it is not a replacement for general relativity.

As I understands it only "string theory includes a massless helicity-2 particle whose behaviour is governed by GR in the classical limit. In this sense string theory - whether or not it's correct - is our only known QGT."
 

Offline Vern

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Hi yor_on; I'm having a little trouble understanding your comment. Quantum Gravity Theory would be a quantum theory. There is a string theory of gravity but I think it is different. The article I referenced was about Quantum Field Theory. QFT uses the famous Feynman diagrams to explain the force exchanges between particles.

I looked back through my posts and didn't find where I might have mixed them up; but it is possible I might have :)
 

Offline yor_on

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If you go by the predictions/expectations made from Standard Model you are correct I think. But we haven't found any gravitons and the ..QFT.. works without that it seems. String theory on the other hand seems to build on the concept of gravitons as I understands it?

--
But then again:) I don't really understand string theory, it's a very esoteric subject to me.
Sorry, wrong syllables up there, QFT, not standard Model I meant.
(Time to go to sleep here I think, tomorrow I will give you a better answer Vern, hopefully so:)
Or? awh, been a very long day this one, sorry about that.
« Last Edit: 05/04/2009 23:02:34 by yor_on »
 

Offline Vern

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If by esoteric you mean:
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A type of hidden knowledge that is generally known only by a few individuals and not by the general public.
I think that would definitely fit string theory. I never liked string theory because I didn't see the need for it. :) I think Lorentz had nature pretty well nailed down back at the turn of the century. QFT, without virtual particles, would predict relativity phenomena, because without virtual particles, forces are restricted to mediation at the speed of light. This would force the Lorentz distortions we see.

 
« Last Edit: 05/04/2009 23:34:28 by Vern »
 

Offline yor_on

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Vern you wrote "QFT, without virtual particles, would predict relativity phenomena, because without virtual particles, forces are restricted to mediation at the speed of light. This would force the Lorentz distortions we see."

Could you give me some simple example of how you think here, like A and B moving and...?
Sounds intriguing to me :)
 

Offline Vern

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Okay; yor_on; here's the notion:

Set the scene to flat space-time and relativity phenomena in accord with Lorentz.

Lets imagine an atom composed of things moving in a jumble of patterns. If you like we can call these quarks and gluons and electrons. The patterns relate to each other by exchanging gluons which must move at the invariant speed of light. Now, when the atom moves, the gluons must travel a greater distance to mediate the forces. This greater amount of distance requires a greater time, and the pattern must squeeze itself together in the direction of motion, in order to remain intact.

I imagine the patterns to be in accord with my speculative Square-Of-The-Shells rule. But the nature of the patterns doesn't matter, they can just as easily be the QM quark-gluon construct.

QM theory avoids predicting relativity phenomena by allowing the concept of virtual particles; since they are not confined to the natural laws they can mediate forces instantly.
« Last Edit: 08/04/2009 22:30:41 by Vern »
 

Offline yor_on

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Ok Vern, I see your idea:)
Let's say that a Atom has a velocity (speed and direction) in spacetime.

If I imagine it like a 3D sphere traveling then it seems to me that the gluons movements should be equalised as they may have one 'length' moving with the 'velocity' and a equivalently shorter length if moving 'back' (depending on if it's in a uniform motion or accelerating, naturally)

So your idea can be seen as a 'deformation' of their lengths, am I right?
But how do you explain how stationary Atoms, relative Atoms traveling, also will become shorter in length, as observed from those Atoms traveling. They shouldn't be, should they? Or is it something I'm missing?

It's a interesting idea Vern.

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« Last Edit: 09/04/2009 01:33:52 by yor_on »
 

Offline Vern

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Quote from: yor_on
If I imagine it like a 3D sphere traveling then it seems to me that the gluons movements should be equalised as they may have one 'length' moving with the 'velocity' and a equivalently shorter length if moving 'back' (depending on if it's in a uniform motion or accelerating, naturally)
It is easier to visualize the effect if you imagine the patterns as circles flat-wise to the direction of motion. There you can easily see that the spiral is a greater distance when the pattern is moving. It is not as easy to see but you get the same effect when the circle is moving edge-wise and any angle in between.

Quote from: yor_on
So your idea can be seen as a 'deformation' of their lengths, am I right?
But how do you explain how stationary Atoms, relative Atoms traveling, also will become shorter in length, as observed from those Atoms traveling. They shouldn't be, should they? Or is it something I'm missing?
The atoms travelling will experience a slowing of time because a greater amount of time is required for their patterns to repeat. This will cause them to measure a lesser amount of time required to traverse a stationary object. So they would measure the stationary object as contracted in the direction of their motion.

We can't compare lengths of measuring sticks directly because we would need to bring them side by side. We can only bring them side by side when they are in the same frame of reference.
« Last Edit: 09/04/2009 13:20:00 by Vern »
 

Offline Mr. Scientist

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Lorentz contraction has been mentioned a few time in threads just lately. I understand that an oblect travelling at very high speed will contract along its length in the direction of travel.

Now, GR states that if 2 objects pass each other with nothing to reference against, it is impossible for a person on 1 of them to know whether it is the object he is on or the other 1 that is moving.

So, my question is, if I was in a spaceship travelling at relativistic speed and we passed a stationary object, would it appear to me as being contracted? Surely it must to fit in with GR. But if it is velocity that causes Lorentz contraction then it wouldn't affect a stationary ship, would it?

No, it doesn't, nice thought though. No, you see, everything is relative, meaning that the effects of the Lorentz Contraction is not noticed from an inertial frame-reference, but the stationary observer will only observe the contraction. The contracion itself should not effect the observing system in any way, unless we are talking about some extreme examples, such as a relativitic-speed electron passing by a stationary atom and exhanging a gravitional fluctuation we call the graviton. In this case, then the contraction of the moving body and acceleration taking into account has caused a ''curvature'' and emits gravitional effects on another rest atom very close by, millimeters apart, for instance. But i did say it was extreme.
 

Offline amrit

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Lorentz contraction has been mentioned a few time in threads just lately. I understand that an oblect travelling at very high speed will contract along its length in the direction of travel.

Now, GR states that if 2 objects pass each other with nothing to reference against, it is impossible for a person on 1 of them to know whether it is the object he is on or the other 1 that is moving.

So, my question is, if I was in a spaceship travelling at relativistic speed and we passed a stationary object, would it appear to me as being contracted? Surely it must to fit in with GR. But if it is velocity that causes Lorentz contraction then it wouldn't affect a stationary ship, would it?

LOrenz contraction was never observed, it is only a math idea
only time shrink, means clocks go slower in fast ship or stronger gravity
 

Offline lightarrow

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LOrenz contraction was never observed, it is only a math idea
No, it's not a math idea, it's a physics fact.
 

Offline yor_on

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LOrenz contraction was never observed, it is only a math idea
only time shrink, means clocks go slower in fast ship or stronger gravity

Muons then?
This one first.
http://en.wikibooks.org/wiki/This_quantum_world/Appendix/Relativity/Lorentz_contraction_time_dilation
And then take a look at 'Relativistic Length Contraction' here.
http://faraday.physics.utoronto.ca/PVB/Harrison/SpecRel/Flash/LengthContract.html
« Last Edit: 18/04/2009 00:10:18 by yor_on »
 

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