Contraction Definition and 708 Threads

Homework Statement Show that the length contraction deforms a sphere in motion to an oblate rotational ellipsoid whose volume decreases by a factor of γ (gamma) Homework Equations x=x'/γ v=4∏r^3/3 (volume for sphere) v=4∏(a^2)b/3 (volume for prolate and oblate spheroid) The...

hi sorry about my english. i am from france. i have a few questions about the image i have found in my schoolbook that i attached to this post. there is a light signal moving up and down and each time it reaches the upper mirror this is somehow detected. there are also two observers: one...

Can one detect length contraction due to general relativity? I.e does length/width/height change with distance to a gravitational centre? If so does the object get longer or shorter? I know this is the case with increasing speed in special relativity, but what about GR... If i went into...

An observer on Earth sees a meteor approaching rapidly, heading directly for the Earth's surface. At a certain instant, the Earth observer sees the meteor at 650m altitude. If the meteor is traveling at 0.92c, as recorded by an Earth radar, what would be the altitude as measured by the alien...

I have been wondering why the universe should behave in such a way. There is no obvious reason why gravity or speed should change the rate you travel through time or the relative distances, 1 second should be 1 second and 1 metre 1 metre whatever the strength of gravity or speed. The only...

Consider two observers in relative motion.At x'=0, t'=0, x=0, t=0. There's a box at distance x metres in the unprimed frame. Since the primed frame moves with a relative velocity v, he observes the length x to be contracted by a factor gamma. Does this imply that when the obsever in the unprimed...

Lets say I have 2 charged spheres that are connected by a spring and they are a distance d apart. The spring is made of a material that will not allow the charge to evenly distribute. And each sphere has the same charge q on it. Now I move with respect to this object and I should see the spring...

A space traveler is very happy to discover that after a long period of 1 g acceleration the measured distance to his destination has contracted substantially. At some point he begins to plan for reversing thrust... It come to him that if he reduces the relative speed between his craft and...

Question on Lorentz contraction and size of "pancakes" I have read that nucleons (protons in particular) appear to look like flattened "pancakes" hitting each other due to the lorentz contraction when crashed together at high speeds. Do any of the colliders give a hint at the "size" of the...

Homework Statement Hello, I have a question about length contraction transformation. In my textbook it looks like this: x_1=γ(x_1'+ut'), x_2=γ(x_2'+ut') If the coordinates of the two events are (x_1,t_1), (x_2, t_2) , why is t used instead of t_1and t_2? The second problem I have is with...

I have read somewhere about the phenomenon called gravitational length contraction.Was gravitational length contraction predicted by general theory of relativity?

Homework Statement Λ particle has a proper life-time τ = 2×10−10 s. After being born in the cloud chamber (a device to track energetic particles) of physics laboratory it left there a a 300cm long trail. Find the speed of this particle in the laboratory frame. Homework Equations...

I am glad for a place like this where I can come to discuss what is on my mind with those interested. My delema is expanding my conceptual understanding of relativity and how it realates to space time and gravity. To begin I will go over how I have come to understand space time...

Prove that the function F(x) = 4x(1-x) maps [0,1] into itself and it not contraction to prove it is not contraction it is enough to prove that there exist a number in [0,1] such that the first derivative exceed 1 F'(x) = 4(1-x) - 4x = 4 - 8x 4-8x > 1 \Rightarrow \frac{3}{8} > x...

This link is confusing me. http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html In this link, with non-relativistic method, half life is calculated as 21.8. But with relativistic method half life is calculated as 4.36. We calculate half life considering time dilation for muon...

Assume a spherically symmetric transparent objects relative to the observer high-speed motion, what the observer will see? 1, a discus (one dimension of contraction) 2, a olive football (two- dimensional of contraction ) 3, a narrowing of the sphere (three-dimensional at the same time...

A google search revealed an often asked question (including a locked thread here) about two ships approaching with closing speed > c, say each going .75c. And there's always multiple answers from the experts about relative frames and Lorentz this and that and you have to use the special formula...

The title isn't quite clear, because the question was a little too long. Here it is in full: How to apply length contraction and time dilation to a moving observer to measure the speed of light of a light beam moving parallel to their reference frame. Imagery and familiarity are my...

Hello, Suppose, There is two points [t_{a1}, x_{a1}] and [t_{a2}, x_{a2}] stationary in my frame A. I say L_a=x_{a2}-x_{a1}. If I want to find x component of co-ordinates in other frame B which is moving relative to me with constant speed v. I have to use the equation 1...

Is there any potential energy associated with length contraction? If I start with a rod at rest, and accelerate it to a relavsitic kinetic energy, the rod also length contracts, at least as viewed from the ground frame watching the rod go by. When the rod decelerates and comes to rest, it will...

Suppose there exists an absolute frame. The observer is at rest. an object moves with velocity v. Suppose it contracts as expected. Does this imply automatically that time dilation occurred?

To understand length contraction better, would an precise instrument where width, height and length must be exact equal for working when standing still in frame A, still working in its rest frame B at a higher speed in frame A with length contraction ? With other words, is length contraction...

It is my understanding that an astronaut could get from Earth to the far edge of the Milky Way within the length of a human lifetime if she were traveling close enough to the speed of light. From earth’s perspective, time would pass very slowly for her as she moved across the galaxy. From the...

The question I have is to do with the Relativity of Simultaneity of the type described by Einsten; whereby two light emitters are placed pulsing once every millisecond on board a spaceship traveling at the speed of light. One of these lights faces forward and the other faces aft. If time dilates...

Homework Statement An electron travels in an accelerator tube at a speed of 0.997 c relative to the Earth. In the frame of the electron, the length of the tube is 1.20 m. A. What is the length of the tube relative to Earth? B. Relative to Earth, how long does it take for the electron to...

Hi, To simplify the explanation of my problem, imagine that I have in my hand a rectangular steel piece of 1.5mm thickness with a hole of 2mm diameter. In the other hand I have a small tubular steel piece 10mm length x 2mm diameter. I have to put this tubular piece into the rectangular...

For the explanation of the Lorentz derivation in Wiki with the known triangle, 2 rest frames are considered in 1 view, so that's not forbidden. So I do too. To explain time dilation is easier to understand if you see it by length contraction. That could be explained somehow in the future...

Hi, I'm trying to model a compensation device in a hydraulic system. Basically, I have a closed pipe that contains a body of liquid (water glycol) and as time elapses this fluid is subject to a cooling effect. This results in contraction and hence a pressure decrease which is subsequently...

I've been told several times that length contraction is not "real" in the sense of material or its space actually contracting. How does modern physics (by that I mean what is being taught currently) view Bell's spaceship paradox. Will the string break? Why, if length contraction is not real...

There is a train(think of having only two boggie for a claer visualization ) in which two rod which are attached to the front and rear end of the train(say, the length between these rod is the length of the train). These are lowered by a single lever to touch the ground. These rods are at...

Hi all, modern physics student here. If the Lorentz contraction occurs at relativistic speeds, how does it gain mass yet get shorter? The best I can think of is that it has to depend in which reference frame one is in at the time. Does anyone know any useful links where I can read about this?

Homework Statement A rod of length L_0 moves with a speed v along the horizontal direction. The rod makes an angle of θ_0 with respect to the x'-axis. a. Show that the length of the rod as measured by a stationary observer is given by L = L_o [1 - (v^2 / c^2) cos^2 (θ_o) ]^(.5)...

Homework Statement Two events are observed by inertial observer Stampy to occur a spatial distance of 15 c·s apart with the spatial coordinate of the second larger than the spatial coordinate of the first. Stampy also determines that the second event occurred 17 s after the first. According...

The way I've been reading it, elliptic geometries are due to a positive Gaussian curvature, while hyperbolic geometries are due to a negative Gaussian curvature. Do local saddle curvatures mean local time dilation and length contraction, or do they mean local time acceleration and length...

How can relativistic length contraction be measured at the quantum scale? Since a Planck length by definition cannot be divided, how can something that is 1 Planck length, traveling near the speed of light, contract with respect to an observer? In other words, how can an observer possibly...

Hi all, this is not a HW problem but one I made up myself, (so you won't find it in any txtbooks or solutions etc.). It also is much more advanced than for someone on the physics HW site, as I can see, so I thought it best to put here. I'm having trouble working out simultaneity and Lorentz...

Hey guys, one quick question about Wick contractions and derivatives: Suppose I want to write down all (non-vacuum) Wick contractions of two fields a, and one field A into a cubic QCD-like interaction term of the form \partial^\nu A^{\mu, a}(p_1) a_\mu^b(p_2) a_\nu^c(p_3) f^{abc} to...

Hi everyone, I have seen this reference http://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe and I have seen in this reference that the ultimate fate of the universe could be a big crunch which means that after the expansion of the universe comes to the limit of the expansion it...

In this video: Special Relativity: Length contraction in more detail http://www.youtube.com/watch?v=s3ZqBt8KWVQ&feature=mfu_in_order&list=UL for the derivation of Lorentz contraction equation at 2.48 the guy says, "I won't bore you with the details". I'd appreciate is someone would...

Are these really just two ways of explaining the same thing?

This question is in regard to special relativity. From my rudimentary understanding, concerning the twin paradox, if one twin leaves traveling near the speed of light and returns, he will find himself younger than his twin who stayed behind. Hence, the effect of time dilation is permanent...

Lorentzian contraction of a box increases the pressure inside? I have been doing some research on gravity, and I am having a very hard time with the following example I found in a book entitled Gravity From the Ground Up by Bernard Schutz. It sounds like a 3rd grader explaining...

I have seen PeterDonis state that predictions of GR are expressed as contracted tensors i.e. scalars. And they are coordinate independent. So I have a question what these scalars represent physically? Could it be that they represent measurements of physical quantities (with tensors dual...

1 does length contraction occur in gravitational fields 2 what is the equation of gravitational length contraction 3 what are the units of measuring mass not weight

We all know the definition of a rope between two identical accelerating spaceships and how that rope will break assuming they both accelerate with the identical same velocity (as defined from a observer on Earth for example). And it makes sense, thinking of stress. But how do I define a Lorentz...

Homework Statement The dimensions of your friend’s spaceship are 100 meters in length, with a cabin width of 20 meters (i.e., you could approximate the main body of the ship as a cylinder with length 100 meters and diameter 20 meters). However, since your friend’s spaceship is speeding past...

Homework Statement A rod of proper length L0 oriented parallel to the x-axis moves with speed u along the x-axis in S. What is the length measured by an observer in S'? Homework Equations Relativistic relative velocity: For an object moving with speed u in S, its speed u' in S' = (u - v)/(1...

A clock falling towards the event horizon of a black hole would appear slowed down to the point of being frozen in time (or almost). But I'd like to understand properly what happens to the length contraction experienced by an observer falling together with that clock. Would he experience...

Homework Statement As measured by an observer on earth, a spacecraft runway has a length of 3.6km. What is the length of the runway as measured by the pilot of a spacecraft flying directly over the runway at a speed 4.00 x10^7 m/s relative to the earth?Homework Equations L= Lnot/γThe...

I'll try to be as specific as possible with my question. From my reading of SR I understand that an object that is moving relative to me will be contracted in the direction of its motion. I have no issue with that and I accept it as a fact. Would I be right in thinking that there is also length...