Is Length Contraction Real? The Genuine answer (Special Relativity)
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- Опубликовано: 12 июл 2024
- The phenomenon of special relativity called length contraction is probably the most tricky one in the whole theory. Can solid object shrink just because someone is moving relative to it? or is it just an illusion caused by the limited speed of light? what it really is? and what impact it has on the observer?
All the answers you can find in this video :)
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i really love your videos man.
You are trying to give us real science, not attempts to impress and get views and money.
Thanks, I really enjoyed this video ... 🥰
Have you ever read John Bell's paper on how to teach relativity? He has the exact opposite view from yours. He sees both length contraction and even time dilation as actual mechanistic effects, and *because* of this, do you measure the speed of light to be the same in all frames of reference
John Bell's paper is anti-relativistic nonsense. I started reading recently and had to stop to see if he been institutionalized and was writing out of an insane asylum. Anyway, we measure the gravitational field to be a metric field, that is, all measurements are consistent with Weak Equivalence, Local Lorentz Invariance, and Local Position Invariance.
awesome video. just one thing i dont understand: why would an observer always measure the front of the ship first and the rear later (from the perspective of an observer moving with the ship)? at 3:58
Because if you measure from the back then by the time you close the front door, the front of the ship will be sticking out of the back of the garage when the back door is closed.
But there is a bigger problem than that: if the ship is powered from the front as accelerates to light speed then 'length contraction' would mean that the back of the ship is accelerating at a faster rate than the front of the ship. Cool, huh?
Relativity of simultaneity. the observer at rest with the ship will see the external observer measure 1 end before the other.
the end he will see the external observer measure first is the end that he is moving towards closest first.
remember the measurements have to be taken at the same time. how do you know that is the case if you aren't at rest? you do calculations. but what happens if you do calculations to work out the times an event happened when travelling close to speed of light? you have to do equations to take into account how the relative speeds affect measurements of time and length. moving close to speed of light affects the results of measurements of time and length.
why? because we use light as the means of measurement of everything. light is the barometer, the universal reference frame.
time of events and everything even measurements of length is affected by how close to speed of light either rhe observer or object is moving.
since the speed of light is constant in all frames, the calculations we do to determine time and length, will throw different results for different observers.
the speed of light will determine if someone says events were measured at the same time or not and whether they are moving towards or away from that light will affect the results of their calculations.
at speeds of light we do not see, we measure and calculate. we do maths.
the observer at rest with the ship has to see the light bounce from the external observer and then come to meet him. so he will see him measure 1 end first and then the second end.
from his perspective the external observer will not have measured the ship ends simultaneously. he will have measured one end first and then the second.
this is because he is moving towards or away from the external observer. so when he does his calculations of when the external observer measured the two ends of the ship, he comes away with maths that says it didn't happen at the same time.
this is cause if there is a speed difference between the measured object and observer that is moving close to speed of light, their speed will affect how they measure light.
in your scenario case, this is the observer at rest with the ship measuring the external observer who is travelling at close to light speed.
It is the "relativity of simultaneity". Clocks in a moving reference frame are not synchronized as they would be in a stationary reference frame. That follows from the fact that all observers measure the relative speed of light as c no matter how fast they are moving. If one observer is moving relative to another and both measure a single light flash traveling to the front of a moving spaceship, how can a stationary observer measure the speed of the flash as c and also the spaceship measure it as c? The front of the ship is traveling away from the flash emission point, so the stationary observer sees that it should get to the front later. But the ship still measures it as reaching the front at a speed of c because the ship's clocks at the front are set delayed. When it is all figured out, measuring a length (where the front and rear positions must be measured at the same time) is distorted by the fact that front and rear clocks are synchronized differently in relatively moving inertial reference frames.
best video on this
Thank you! Would you say this means all of relativity can be derived from giving up absolute simultaneity? And that would mean you can understand all relativistic spacetime structure just from accepting time dilation.
This gives me the idea that time is very fundamental and maybe creates to space.
Well, all the phenomena of special relativity are consequences of the postulates namely the speed of light is independent of the relative motion of the source and you also need principle of relativity. In order to satisfy these two postulates you need to give up absolute simultaneity and absolute time and space.
To the contrary of your idea, special relativity teaches us that time is not much differentor fundamental than space
All of the relativistic effects are consequences of the metric field, i.e. the geometry of the gravitational field.
@@kylelochlann5053 "All of the relativistic effects are consequences of the metric field, i.e. the geometry of the gravitational field."
Yes, and for me, that raises a bit of a question with regard to making 'c' absolute. It seems to me that we have to do an awful lot of mathematical gymnastics in order to 'force' physical reality to comport with the reality predicted by equations that implicitly _assume_ that 'c' is absolute.
If _I_ had been the one to come up with the idea of setting 'c' to an absolute and then constructed the equations containing _all_ the right variables to describe _each_ possible influence that correctly accounts for absolutely _every possible_ observation that can be made, measured or otherwise experienced _anywhere_ or _anytime_ in _any_ physical reality that can possibly exist and _then,_ just for kicks, decided to use those very same equations to work out the answer to the question: if I drive my 5 m car into my 5 m garage at the speed of light, will it be possible to close both the front and back doors at the same time and found that '5 m' wasn't worth the paper it was written on, I would have thought,
"Hmm! I'm missing something," rather than insisting that 'c' is the actual 'cause' of the discrepancies that are thrown up by physical reality and therefore require me to invent the concepts of 'spacetime', 'Black Holes', 'Time Dilation'', 'Length Contraction', etc., to compensate for such effects.
At least, I think, that's _one_ way to look at it. But what I find quite fascinating is: basically, because of Einstein, 'c' is the _cause_ of _everything_ since the 'finely tuned' nature of reality is an emergent property of 'c', right? So, the existence of 'c' is what governs over how the universe _can_ evolve, right? And therefore, in effect _and_ in keeping with Scripture, Einstein has quantified 'God'. Right? Given the current state of the world, I find this quite astounding.
Unchanging and uncreated; independent of space and time; eternal and invisible force; creator of the universe - Who, or _what,_ am I describing here? By _that_ definition, 'God' is _precisely_ equal to 'c', isn't He? This is the best bit:
'E', (needed to build pyramids) is equal to 'm', (a number of people), multiplied by 'c^2, (the size of the 'box' required to contain/control 'm').
So I'm with you; there is an internal inconsistency that appears as the result of assuming 'c' to be absolute and which is demonstrated by the existence of 'rainbows'. Clearly, changes in the medium through which light travels affects photons of different wavelengths in slightly different ways. It is as if photons of different wavelengths 'experience' the 'inertia' presented to them by the medium through which they are traveling to different extents, doesn't it?
In other words: all photons are created equal but some are more equal than others, right? But that would mean that there are lots and lots of Gods, wouldn't it?
does the lorentz contraction apply to planck length? can observer see length smaller than planck length this way?
yes, if not that would break the first principle of relativity. However this is not an verified fact. If you find an experimental evidence of a certain length being conserved then the whole special relativity breaks apart.
Yes, length contraction applies at every length scale.
thanks!
What do you think about the submarine paradox ?
A submarine with the same density as water either sinks or rises diet to lengh contraction in different frames .
The solution is tgat it always sinks , and but the explanations are quite nin trivial mathematicaly .
Could you just take the earth to be infinately long compared to the sub and have uts density alsi increase in the frame of the sub therby compensating for the increase of water density
I haven't heard of such paradox yet so maybe I create a video about it down the road thanks for the tip :D But ultimately I think that all these paradoxes are just more complicated examples of the same paradox of the length contraction like barn-pole paradox. You can always create a more complicated scenario where the solution will be more complicated but ultimately all can be solved by properly understanding what length contraction actually mean.
I also think the front and back of the object are measured at different times , but where I disagree is that you think "it is" shorter , where as I think it "appears" shorter .
Question , an experiment can only give one result , if the car and garage paradox thought experiment was done as an actual experiment , do you think the garage doors would close or not ?
Hi, I have video about it where I explain what would happen if the garage doors would remain close and would not open again. I refer to that video at the end of this one.
@@lukasrafajpps But Einstein specifically said that the effects of SR were REAL, so objects really do shrink and Time dilates, if it was only a measurement error, then fix the measurement method to remove the error. And thus we find that Newton was correct all along. (And Mass increase is real, according to Particle Accelerator fans. )
@@lukasrafajpps The point is you get a different result depending on what reference frame you choose , the garage doors still close at different times, but you can only have one result. What result do you think will be measured , same time or not ?
@@m.c.4674 In both cases you would be able to close the doors I explain this at the end of the video about barn paradox.
You have to have only one result if you are measuring a meaningful quantity and simultaneity is no such thing. Paradox would only occur if we concluded that we can't park the car in the garage in one frame and not in the other but I argue that we would be able to do it in both.
@@everythingisalllies2141 They are real but not in a sence you think. It is not even a measurement error we don't need to fix anything. The coordinate length is the disntance between the two points in space measured simultaneously in that particular frame. Since the simultaneity is not absolute, this distance will change from observer to observer but it does not mean the solid object physically shrink
You do not require 2 simultaneous measurements to measure the length of a moving object. Simply obtain the time duration (in proper time) that a vehicle appears to pass through a single point via infrared sensor if you know the proper length relative to your rest frame S as well as the relative speed of the car as seen in S you can determine if in actuality some length contraction physically took place.
In this case you would measure of course contracted length because the observer moving with the object would measure the same relative speed of these two frames and therefore his measurement of length in this case is the same. He would measure the time interval the front of the object passed a certain point in the S frame and then back of the object and calculated the length. However he would conclude that in the S frame time is dilated and therefore in the S frame you had to measure lower length.
From the observer in S althought he would conclude that it is the moving clock that is dilated but the clock at the front and the back of the object are not in sync.
@@lukasrafajpps My apologies I misunderstood. your intent. Thank you for the explanation. I am guessing that the time variances front to back should be small since the whole car will ultimately be in the same frame of reference. For this reason shouldn't another method other than simultaneity be more appropriate? Thank you.
It seems to me that I understand the issue of Lorentz contraction and the lack of absolute simultaneity, and yet I still cannot understand that there is no contraction in reality (?), and at the same time it is not an illusion? 😅
If the object is moving it has the same influence on its suroundings as if it was really contracted because that is what we measure as length. So in this meaning its length is really contracted because we measure it to be lower. So in different words, if you see object moving then you have to work with its contracted length to make physical predictions. The fact that its rest length is unchanged is irelevant because that is the length you don't measure.
Relativity of simultaneity is not an optical effect. Therefore the length contraction is neither.
Did we know that length contraction is derived from c is universal constant in all inertial frame?
Did we know that c is universal constant based on absence of Aether?
Did we know that MMX fail to detect Aether?
Did we also know that just because MMX fail to detect Aether that doesn’t mean it doesn’t exist?
Did we know that Aether can be detected with simple experiment?
Now do one one erenfeuchts disk
Okay, we start with a 4D Space-Time environment. Two events can be located at the exact same place in the time dimension of Space-Time, but be apart from each other spatially. These two events will therefore truly be simultaneous events. However, different observers in different frames of reference, each will not see this as being simultaneous events. But the point is, unless one is a complete bonehead, one realizes that a set of events relative to Space-Time occurs, which is then being observed differently from the lessor mere 3D frames of reference. So in physics today, the absolute cause of the Special relativity phenomena, is basically never ever spoken of. Moving on. Okay, so you can have a ruler that is entirely in motion across the time dimension, and is at true rest spatially. Here your entire ruler extends across space. But if you change your rulers direction of travel within the 4D Space-Time environment, then rotation has obviously been required to do so, and thus in turn less of the ruler now extends across space, now that it partially extends across the time dimension. So there is no real length contraction taking place here, but simply less of the ruler now extends across space.
_"So there is no real length contraction taking place here, but simply less of the ruler now extends across space"_ - that is indeed one way to look at it. The rod appears to be rotated in spacetime.
The only misconception you have, is that there is no "true spacetime" in the sense that you assume. Each observer has their own idea of what spacetime is. Hence different observers can see different rotations.
@@renedekker9806 Well as I said, if you start out with the "Absolute" 4D Space-Time environment, and the ongoing "ABSOLUTE 'C' " motion that is taking place within it, you end up discovering the cause of the Special Relativity(SR) phenomena. It reveals how the independent frames of reference come into play. Also, if you then create a simple geometric representation of this ongoing absolute motion taking place within the absolute Space-Time environment, a geometry which is composed of motion vectors and length scalars combined, you can use it to derive the SR mathematical equations, and complete the task in a matter of minutes, and do so even if you know nothing about physics.
He is really good ! But length like time is not a thing that is, like momentum and energy.. it is a thing that is perceived.
Momentum and energy aren't real, they're constraints on the dynamics owed to symmetry conditions. Length is most certainly real.
Here's where a problem appears with SR. Suppose you have a square box moving at 0.866 c. The length would be contracted by 50%, making it a 1:2 rectangle box, and time would be dilated to half speed. If a laser was fired from the upper rear corner to the lower front corner, meaning diagonally, the beam would be directed at a 45 degree angle as seen from inside the box but at a 26.5650512 degree angle as seen by a stationary observer. Its length would change from 1.4142 times the height of the box to 1.118 times, a reduction of 20.943%. A vertical beam would be 100% of its normal stationary length, a horizontal beam would be 50% of its normal length but the diagonal beam would be 79.057%, which is not the average of 100% and 50%, which would be 75%.
Now Einstein has a serious conundrum, because how could he make all three beams work out correctly using the same time dilation and clock desynchronization factors? The desynchronization of the rear and front clocks can't work with both the horizontal and diagonal beams at the same time, you would require two different amounts of desynchronization. That's why you never see a thought experiment involving a diagonal beam.
_"at a 26.5650512 degree angle as seen by a stationary observer"_ - the angle with the vertical as seen by the stationary observer would be 77.33 degrees. You are forgetting that the box is moving.
_"Its length would change from 1.4142 times the height of the box to 1.118 times"_ - its length would be 4.56 times the height.
_"A vertical beam would be 100% of its normal stationary length"_ - a beam that is vertical wrt. the box would not be vertical according to the stationary observer. That is used in the normal light clock derivation of time dilation.
_"That's why you never see a thought experiment involving a diagonal beam"_ - there is no problem at all with diagonal beams.
If the light clock were moving past in front of an observer, the angle they would see the light take would change. The zig zag path would appear closer to vertical the farther away from the observer the light clock is and stretched out the longest when directly in front of the observer. The only way the perceived path would be a consistently angled zig zag would be if the light clock were circling the observer. Thus, Einstein's time dilation would only apply under those conditions, not a straight moving frame as I first described.@@renedekker9806
@@renedekker9806 "You are forgetting that the box is moving."
You still have a problem though because you are accelerating the box from its rear. If the box is powered from the front as it accelerates toward light speed then 'length contraction' would mean that the rear of the box is accelerating at a faster rate than the front of the box. Cool, huh? This implies that faster than light travel is possible since, when the front of the box is traveling a the speed of light, the rear of the box will be traveling slightly faster.
Right?
@@undercoveragent9889 _"You still have a problem though because you are accelerating the box from its rear"_ - the Lorentz transformation in SR assumes they are travelling with constant speed. If you count in acceleration, then you indeed get different results.
_"...would mean that the rear of the box is accelerating at a faster rate than the front of the box"_ - correct, and yes, I agree that is cool.
_"when the front of the box is traveling a the speed of light, the rear of the box will be traveling slightly faster"_ - the front cannot travel at the speed of light. And yes, during acceleration, with a rigid object, the back will accelerate faster than the front (from the perspective of a stationary observer). That simply means that the rear reaches a speed close to the speed of light earlier than the front reaches that same speed.
If the length contraction is not real, Michelson-Morley experiment would have given positive result, that is there will be some drift in the interference pattern. Length contraction in the direction of motion is real but not detectable by observer in the same frame because his measuring scale will shrink proportionately in the direction of motion. I have mathematical proof for it.
are you saying that there is one frame where the shrinking does not take place?
@@lukasrafajpps : No, It is impossible to imagine a rest frame in the universe. I proved the contrary. That is, a moving frame should undergo contraction in the direction of motion to give Null result in Michelson-Morley experiment. Otherwise there will be a path difference between parallel rays and perpendicular rays, this results in change of interference pattern when the apparatus is rotated.
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I still don't get why it isn't considered an illusion. proper length seems to be the only valid length. everything else is relative.
This is all born of scientists trying to CREATE an absolute velocity reference frame. But, each velocity is infinitely relative which says that there is NO definition for any velocity. The INSTANT that it changes, there is acceleration, and ALL OBSERVERS AGREE. Theory is simply focused on the wrong aspects of science -the vague useless relative aspects. Einstein was wrong in that you CAN differentiate between linear acceleration and gravity acceleration. The gravity frame will squeeze inward, but the linear acceleration frame will not. With absolutes, you don't need frames. Dimensions are not real and are created and manipulated by math (transforms), which also creates a lot of fools by trying to CREATE an absolute frame for v. Length contraction and time dilation probably cancel out, and the only real physics in modern science is the mass increase. Space certainly has an affect on inertia by gravity, photoelectric effect, clocks, and anything you consider to be a force. The Strong force was invented to maintain the established concept of electric charge, so if electric charge changes when positive particles are crammed into a nucleus, then the Strong force don't exist, and apparent mass changes are suddenly associated with the changing mechanism of electric charge (whatever that is). That Strong force bandage has hidden a lot of physics. That is its only job. It is funny that neutrons are invisible. They may be massive photons for all we know, but science has never gone there. Most spend their time trying to master this crap. Question it, it falls apart.
Mathematics in physics problem solving is just like problem solving with gymnastics in a gymnasium. Once we step out of the gymnasium we face the real world.
The problem is we can’t challenge our professor even if we are right to receive his appraisal towards our graduation.
What happens in mathematics doesn’t mean it always happens in this universe. That including selective dimensional variance caused by speed.
I don’t believe length contraction. It is an artifice based on light c is constant in all reference frame, as a consequence of a faulty MMX experiment to a false conclusion. Concluding that Aether isn’t a medium of light.
Are u German
Slavic but I don't know my exact roots :D
There is no real length contraction and there is no definition of time.
Einstein was a plagiarist.
''In 1875, four years before Albert Einstein was born, Samuel Tolver Preston published an amazing book entitled "Physics of the Ether". In it he set down the now famous formula E = mc2 and thoroughly explained its implications. Preston expressly stated that matter contains a store of energy which if fully utilized could create atomic bombs and atomic energy. He knew that atomic energy would someday replace coal. He also described superconductivity and asserted that gravity propagates at light speed. Long before Einstein, Preston completely relativized unipolar induction. His complete works are republished along with commentary and analysis by Christopher Jon Bjerknes who discovered the fact that Preston had anticipated Einstein by many decades and had a better understanding of E = mc2 than Einstein. Albert Einstein mistakenly believed that atomic bombs and atomic energy were impossible to produce.''
Simple to solve the paradox. "Relativity of Simultaneity" is WRONG. It is based on a failure to understand Physics.