What is Length contraction: Definition and 475 Discussions

Length contraction is the phenomenon that a moving object's length is measured to be shorter than its proper length, which is the length as measured in the object's own rest frame. It is also known as Lorentz contraction or Lorentz–FitzGerald contraction (after Hendrik Lorentz and George Francis FitzGerald) and is usually only noticeable at a substantial fraction of the speed of light. Length contraction is only in the direction in which the body is travelling. For standard objects, this effect is negligible at everyday speeds, and can be ignored for all regular purposes, only becoming significant as the object approaches the speed of light relative to the observer.

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  1. Z

    Does Length Contraction Affect the Wavelength of Light from a Moving Source?

    Hey, sorry if this is a stupid question but I'm getting really confused... If I am standing on the Earth and watch a spaceship moving past at say 0.8*c from left to right, I will observe the spaceship to contract in its direction of motion. If a person on the spaceship shines a torch also from...
  2. Q

    Length Contraction & Molecular Structure Effects

    Hello, Just one quick question. What happens to the molecular structure of an object if it moves close to the speed of light? Does the high speed affect the atoms, protons, neutrons, electrons, molecular structures? Does the density/thickness of the object increase? Or do the protons and...
  3. W

    Wanting to make sure I understand length contraction and time dilation

    I made my own problem and tried to answer it to see if I understand relativity well. Can you please let me know if I got the answers right? A spaceship moving at .866c compared to a pair of stars. The stars are located at points A and B which appear to be 2 light seconds apart from an...
  4. A

    Length Contraction & Angled Motion

    if length contraction only applies in the direction of motion, then what happens if there is an angle to the direction of motion that's not perpendicular?
  5. L

    Special Relativity and length contraction

    A meter stick moves past you at great speed. Its motion relative to you is parallel to its long axis. If you measure the length of the moving meter stick to be 1.00 ft (1ft=.3048 m), for example by comparing it to a one-foot ruler that is at rest relative to you, at what speed is the meter...
  6. S

    Length contraction equation. what am i doing wrong?

    Length contraction equation determining v. what am i doing wrong? OK, L=L*(1-v2/c2)1/2 (to the power of 1/2) L=.75m L*=1.0m now i need to find v and for the life of me i always end up with a value greater then c which is obviously impossible. ill simplify to v=...
  7. S

    Err, did I do this length contraction problem right?

    it's a typical homework problem I suppose, a meter stick traveling at v=.8c at an angle of 60 degrees to v as seen in the stick's reference frame. I solved it out and got .6m, which is incidentaly the same answer I got for if it were traveling parallel to v. is that, you know, how that works?
  8. A

    Relativistic length contraction

    How do you find relativistic length contraction?
  9. D

    Misconceptions about length contraction

    Could someone please, briefy explain length contraction under general relativity?? Is it possibly for the universe to contract around a spaceship so that the distances between stars become only inches.. and thus it becomes possible to reach stars lightyears away in very little time? THe...
  10. ?

    Probably a very easy length contraction problem

    Hi all, Can someone tell me what to expect and how to calculate the length contraction when two bodies move towards each other, rather than away? The particular question I'm stuck on is this: A garage is 5m long, a car approaches it at 0.6c. What is the length of the garage according...
  11. bayan

    Length Contraction in Special Relativity

    In the SR section of my book there is a question like this. An astronout is traveling at .9C. The spacecraft has a proper legth of 100m. a)what is the length observed by observer? I get this as I divide 100 by gamma which is about 2.29 b)Astronouts view is also effected by the time it...
  12. E

    Length contraction and time dilation

    I'm having trouble understanding how length contracts while time dilates when the 2 equations in the lorentz transformation dealing with these are nearly identical (which makes me think that length and time should transform in the same way). Thanks in advance.
  13. G

    How Do Muons Travel from the Atmosphere to Earth Despite Their Short Lifespan?

    Muons have a "proper lifetime" = 2.2 micro seconds ("proper lifetime" = lifetime of a muon which is at rest). These Muons are created in the upper atmosphere at a height of 4700m above the Earth's surface. So, a muon traveling at a speed of 0.99c can travel only a distance of 653.4 m if you do...
  14. G

    Time Dilation and Length Contraction

    how can you explain that a rocket ship traveling at 99.999% of c will see a beam of light pass by it at c with respect to the space ship? what exactly is the definition of time dilation and length contraction and what formula's are used to explain the phenomenon(sp?) thanks :smile:
  15. C

    What is the Proper Length of a Ruler in Motion?

    Here's another one for ya'll. A spacecraft antenna is at an angle of 10 degrees relative to the axis of the spacecraft . If the spacecraft moves away from the Earth at a speed of .70c, what is the angle of the antenna as seen from earth?
  16. A

    Is length contraction relative or absolute?

    Is length contraction relative or absolute?? This is from the book "Speakable and unspeakable in quantum mechanics" by J.S. Bell. Three small spaceships, A, B, and , drift freely in a region of space remote from other matter, without rotation and without relative motion, with B and C...
  17. A

    Evidence of length contraction

    Hello all. I've recently had something of an epiphany regarding relativity. One of those moments when things become clear and it all makes sense. However, having not actually performed any of the experiments which may or may not support the whole thing, I have a question. Is there evidence...
  18. zoobyshoe

    Practical Use For Length Contraction?

    I'm looking through One Two Three...Infinity by George Gamow. After having explained length contraction with the example of two ships passing in space who each view the other as contracted he comments in a footnote: "Of course this is all a theoretical picture. Actually if two rocket ships...
  19. H

    Length Contraction and the Bomb Paradox

    Question "Length Contraction" Hello, I just finished reading special theory of relativity written by Albert Einstein himself. Even though I understand the book is only written to convey general idea it still left me with a lot of question. Einstein said that any event that occurs in one...
  20. B

    Speed of light and length contraction

    Hey, I am new to this site, I'm not entirely sure where i should post this question but can anyone here help? I need to know Einsteins assumption of the speed of light as a constant by referring to length contraction, mass and time dilation and how it affects people traveeling in space at high...
  21. K

    Correction to length contraction equation

    Suppose an electron has a small radius and we look at its radius and mass from the point of view of special relativity. Let's use the idea of (mass x length) = constant. No quantization. Is the contraction to zero radius at c a problem? If so then we can guess how to stop it. One way...
  22. K

    Length contraction and field theory

    If length contraction was quantized, then a particle of a given radius could have a constant radius for many observers moving at different speeds. Could such a particle be used to formulate a quantum field theory?
  23. R

    Would a Train Going at Near Light Speed Cause Length Contraction on a Planet?

    suppose you had a planet with a train going all the way around the circumference. The train is a complete loop so you just have an endless train. now speed the train up to near c. Because of length contration would the train begin to squeeze the planet?
  24. S

    4 length contraction questions.

    If I was traveling close to the speed of light and passed a hotdog outside, the hotdog would appear smaller to me compared to the hotdogs I remember eating on Earth correct? If I was traveling close to the speed of light with a hotdog in my hand and held it right in front of my pants, as I...
  25. R

    Evidence for length contraction

    would some be able to give me an example that shows some evidence of length contraction? i have looked at the muons example, but it seem to be dependent on the time dilation effect, rather than being evidence of length contraction. thanks for any help.:) much appreciated. btw, feel...
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