Contraction Definition and 689 Threads

I have the following mapping (generalized geometric mean): y(i)=exp\left[{\sum_j p(j|i)\log x(j)}\right]\\ ,\ i,j=1..N where p(j|i) is a normalized conditional probability. my question is - is this a contraction mapping? in other words, does the following equation have a unique...

Hi all, apologies if this has been posted a million times before... I'm trying to explain the twin paradox without getting involved with length contraction. One way to think of it is Twin A remains at rest on Earth then twin B goes off at 4c/5 to Alpha centauri 4 light years away, then...

Homework Statement A meter stick at rest in S' is tilted at an angle of 30 degrees to the x'axis. If S' moves a speed beta = 0.8 with respect to S. a)How long is the the meter stick as measured in S ? b)What angle does it make with the x-axis? Homework Equations l=l naught/gamma The...

Inertia has Lorentz-Fitzgerald contraction. Is there a similar (parallel?) contraction equation for Gravitational forces?

I need help with length contraction. I need videos that explains or proves that length contraction is possible even if it is just the visual interpretation of an observer. pls help.

Interstellar travel is always a problem in science fiction: you can't have the hero hibernate for millions of years whenever he or she wants to travel to another star, but it's annoying when spaceships just magically move faster than light. However, wouldn't length contraction from special...

I have recently been reminded of a problem a friend posed to me many months ago in special relativity that I was never able to address: Suppose we have a person inside a moving spaceship of proper length L. According to an observer outside the ship, the person inside the ship is at rest...

Does Acceleration affect Lorentz contraction? Suppose their was a Circle spinning around its center then its outer edges would decrease in length. looking somewhat similar to a saw blade or something. This doesn't make sense though because then then object would change shape depending...

OK I've been reading up on Lorentz contractions in special relativity and i have been wondering about something for a while now. When a Lorentz contraction occurs what actually contracts? the space between the atoms? (because we are 99% space) the actual atoms themselves? or the distance between...

In this thread https://www.physicsforums.com/showthread.php?t=361915" I showed my viewpoint on a real length contraction https://www.physicsforums.com/showpost.php?p=2486767&postcount=21": and I've see no criticism on my view, neither acceptance nor denial, that a real length contraction must...

Suppose the earth, moon, and an extraterrestial observer(ET) are at the corner of an equilateral triangle. The Earth observer points a laser at the moon and emits a powerful laser pulse for exactly .01 seconds. The 1,860 mile long pulse travels to the moon in about 1.3 seconds. The ET knows that...

I don't understand why this happens. And it's not enough to tell me 'well it happens because Simultaneity is relative' or 'Because Time dilates between frames'. I can still say I don't understand why it happens because shouldn't 2 frames adjust their measurements so that they get the same...

The following is from Accelerating spaceships paradox and physical meaning of length contraction by Vesselin Petkov. Quite a well known paper I think. Speaking of Bell's Spaceship Paradox he says ----This paradox still appears to be regarded by some physicists as proof that (i) only...

I think I am correct in saying that Lorentz relativity and standard SR are experimentally indistinguishable. I think it is also the case that in the first, the space between objects does not contract while in the second evrything inclding space contracts pro rata. As a personal choice I prefer...

Consider two groups of 3 spaceships each. The groups are numbered 1 and 2. The ships in group 1 are numbered 1A, 1B and 1C. The ships in group 2 are numbered 2A, 2B and 2C. In each group, ship A leads, followed directly in line, at fixed and equal proper intervals (as measured in each line's...

Homework Statement A spaceship travels past a planet at a speed of 0.80 c as measured from the planets frame of reference. An observer on the planet measures the length of a moving spaceship to be 40m. a)How long is the spaceship, according to the astronaut? b) At what speed would the...

Hi Does anyone have any information or web links for layman followable explanations of how Lorentz contraction is connected with the accelerator bunching problem. I have found many references to the phenomena but no explication of the actual connection. A related question is: I have heard...

Homework Statement The radius of our galaxy is 3x10^20m (30000 lightyears). (part a): Can a person in principle travel from the center to the edge of the galaxy in a normal lifetime? Explain using Time-Dilation, then Length-Contraction. Homework Equations d\tau = dt \sqrt{1...

Ok, so imagine observer A is moving along with a measuring rod of length L that is being slid along the ground by a rod that holds it steady by pushing it against the ground as it slides (no tilting whatsoever, the base of the rod remains firm against the ground), at a velocity comparable to c...

Reading http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html#Length_Contraction I reminded something that always bothered me about this explanation: I would think that a current carrying wire would only appear electrically neutral when the observer is moving along the wire...

My understanding is that SR time dilation and Lorentz contraction are flip sides of the same coin. The two always occur together, never separately. That is implicit in spacetime diagrams. I think this duality requirement is necessary so that light always travels at the speed of c in every...

I'm doing some sort of notes on special relativity and i got this question, because proper time and time dilation have a relation. In fact we have that proper time is mathematically the arc length of a timelike curve. I will use geometrical units and the Minkowski Metric with the -+++ signature...

Hi, this isn't exactly homework, as I'm teaching myself, but I thought this forum would be more appropriate for it. Homework Statement (Page 36, Introduction to Special Relativity by Wolfgang Rindler) An 18-foot pole, while remaining parallel to the x-axis, moves with velocity (v,-w,0)...

This isn’t an example from a textbook, just something that occurred to me, so there may be any number of mistaken assumptions in it. I must have gone wrong somewhere, but I don't know where, and I'd appreciate any advice. Imagine one of those Swiss high speed trams that wreaked so much havoc...

Ok, I do understand what it is, that things get shorter the faster you go.. But I just want to know why they do?? If anyone could explain to me... Someone told me it was just an illusion because our eyes couldn't keep up but I think that person was wrong, so thank you to anyone that can help :)

Hello, according to my book of 'Geometric Algebra' the operation of Left-Contraction for Blades has a distributive property in respect to addition. However the authors do not prove it, nor they give the smallest hint on how to derive it. The property says that...

Homework Statement 1)An ex-student with a new spacecraft 'buzzes' the school oval on sports day at 1.5 * 10^8 m/s. How long does the 100m track appear to him. 2) The sports day began at 9am. The student buzzed the school at an average speed of 0.5c till the presentation ceremony at...

Homework Statement A woman is 2.0 m tall and has a mass of 60 kg. She moves past an observer with the direction of the motion parallel to her height. The observer measures her relativistic momentum to have a magnitude of 2.30x1010 kg·m/s. What does the observer measure for her height?Homework...

Homework Statement A ladder 4.92 m long leans against a wall inside a spaceship. From the point of view of a person on the ship, the base of the ladder is 3.13 m from the wall, and the top of the ladder is 4.00 m above the floor. The spaceship moves past the Earth with a speed of 0.919c in a...

Problem:"An interstellar cloud with a radius of 10parsecs and a mass of 10000 Msun is contracting. How long does this take? (The cloud itself has no pressure)

Homework Statement 2 bodies move towars each other M1 WITH Velocity V1 and M2 with velocity V2 ,on a frictionless surface with a spring between them(attached to M1),what will be the maximum contraction(I mean You know, shrink or W\E)? Homework Equations reduced mass...

Homework Statement Hello I actually just need help with an explanation rather than equations (I hope this is OK). In my essay I need to explain why the length contraction in Special Relativity is the inverse of the time dilation factor. My explanation is below, but I'm not convinced...

I ask this just to clarify something, because something I read threw me off earlier. An object travels near the speed of light, and you are stationary. You measure the object somehow, and find it's length from your reference frame. Would it's length be shorter or longer than the proper...

If I take F(x)=\sqrt{1+x^2}, then the derivative is always less than one so this is a contraction mapping from R to R, right? But there is no fixed point where F(x)=x, where the contraction mapping theorem says there should be. So where have I gone wrong? Cheers

I understand the explanation for time dilation involving the light clock on the spaceship, or a train. But what is used to explain length contraction. Is there another example that is used involving a light beam and a spaceship.

Hi, This isn't actually a coursework question but rather a part of my course which I'm struggling to get my head round. I can use formula to calculate the amount that an object contracts but I can't seem to get my head around why this happens. I've been trying to imagine a rod traveling past...

In SR is length contraction physically real, or is it just and illusion brought on by high speed motion.

There have been more than a few threads where there clearly is confusion about the use of time dilation and length contraction. People initially think that: 1. in an frame which is in motion relative to themselves, time dilates and lengths contract; and 2. velocities in a frame which is...

So does there exist any evidence to support the theory of length contraction? I am aware of the overwhelming evidence to support time and mass dilation, but none for length.

Hi everybody, I have a question concerning length contraction/time dilation. I read about how time dilation is calculated using transverse motion and how length contraction is calculated using longtitudinal motion in order to preserve lightspeed and it got me thinking: why not use length...

So I was reading up on the SR equations and the following thought experiment crossed my mind: Suppose you have someone in a starship traveling at high enough speed to make the Lorentz factor noticeable. Will that produce a blurring effect when the observer is looking out the front window? I...

I read a theory recently which, to my understanding predicted a contraction or expansion in an electric field (like the lorentz contraction) depending on the two charges involved. Has anything like this ever been expiriementally observed

Hi, I'm trying to understand Lorentzian relativity (Lorentz ether theory, whatever) which is empirically equivalent to the Einsteinian STR. I have, however, a problem in comprehending length contraction. In the Lorentz theory we have a preferred frame and length contraction is a real...

I apologize, I know this is not a QM question per se but I think I am more likely to find someone who could answer this here. I'd like to know (or rather, be reminded of) how to draw contraction symbols in LaTeX (or TeX). I mean the symbol we use to show how two fields are "paired up" when...

Homework Statement Show the derivation for legnth contraction, given that from the example given; The example shows a moving light clock - two walls which are moving in a direction at speed u and a beam of light from wall A to wall B then back to A and so forth. From Ao (starting...

Some days ago there was a discussion on pf whether eath’s magnetic field was rotating. That got me to think again about magnetism and relativity and I found this article: http://en.wikibooks.org/wiki/Special_Relativity/Simultaneity,_time_dilation_and_length_contraction Including this section...

It is known that with the formula that accounts for the time dilation effect in hand we can derive directly the formula that accounts for the length contraction effect: L0/Dt=L/(Dt)0 (1) where L0 and (Dt)0 are proper length and proper time intervals, L and Dt...

Homework Statement A meter stick is moving with 0.8C relative to frame S. What is the sticks length when measured by an observer in S if the stick is 60 degrees to v, as seen in the rest frame? Homework Equations Length contraction = proper length /lorentz factor The Attempt at a...

Question: What is the percent length contraction of an aircraft traveling at Mach 2? So, we know that Mach 2= 680.58 m/s and that L'=L\sqrt{1-(v/c)^2} If you divide over the L to get: L'/L=\sqrt{1-(v/c)^2}=% length contraction Plug-n-chug from here to get...

It's my understanding that gamma (the boost factor) for light is infinite which allows it to have energy (mc^2), however, this is the same factor for legnth contraction & time dilation, I'm not really concerned about time dilation as i thought photons don't experience time? However, there is...