How to test length contraction by experiment?

Oh yeah another wiki article. If you haven't been keeping up, Bell's paradox was already mentioned and it doesn't apply here.

 

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If a simple Wiki article is too much for you, how are we supposed to help you with anything more complex?

It does apply. It's a slight tweak to the same configuration but it's the same principle.
There's plenty of reading to do on the circular scenario as well, but start with the simple one. If the simple one is too complex, then the circular one will be worse.

Anyway, your irritation is out of place. You're going on your gut and it's wrong. You're making an "argument by incredulity" - "I don't see how it works therefore it can't." Don't do that.

 

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No it involves acceleration. I'm not asking for anyone's help. I'm not engaged in an argument of incredulity. I'm not going by my gut at all. I have a ton of math supporting what I say and almost all of it was a complete surprise to my gut. I received some tweaks on the PSX and I like learning new things. This requires experts, not old tired wiki articles. My ultimate goal is to find someone who can tear me down or who I can convert. But I can tell right away if someone's got it or not and see no point of engaging people who don't. I have no problem helping those who ask for help which is why I joined in this discussion with my parallax explanation. Unfortunately no one understands it and I've run out of patience with the rest of this thread. So far Janus has impressed me. Are there others here. That's all I need to know.

 

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This reply is misleading. Most space ships have their thrust from the rear and are very much under compression as they accelerate, but then again, the front of a spaceship accelerates at lower G force than does the rear, even if the ship is being towed.

So if the ship is composed of a line of equal masses each with its own thrusters and each applying identical force at the same time (very much like our bumper car case), then yes, the ship is under tension. The ring of cars has no way of relieving this tension, so the welded ring must break somewhere.

Length contraction is a function of speed, pure and simple. At that speed, each 5 meter bumper car is contracted to 4 meters, forming a 1 meter gap between each. This is same gap as a line of objects accelerated to .6c in a line. A line of 5 ships would form a gap of 1 meter between each. If they were welded together (not in a ring), the 25m object would contract to 20 meters, and the front object would not accelerate at the same rate as the rear object. The individual gaps assumes identical acceleration for each object, which cannot be the case if they're welded together.

You don't recognize it when you see it, so you're actually waiting for somebody who agrees with your story. Try PengKuan. He seems to seek latch onto any story that bucks the standard view.

 

So you're telling me you can't read a Minkowski diagram. I'd just like to get a list of experts here. I'll also post an exchange I had with an expert on the PSX so maybe you can get a clue.



"Your word "illusionary" seems synonymous with any measurement of the rod's length not done in the rod's rest frame. The idea that the rest frame length of the rod is invariant under boosts is well known. You are correct, the invariant length of the rod (or invariant distance to the star) does not change just because we look at it from a boosted frame. In this sense, measurements of the rod's length in other reference frames is illusionary, and we must return to the rest frame of the rod to measure its "real" length. I am still thinking about your idea of Persistence. – Gary Godfrey 44 mins ago"

You can check out his credentials on the PSX

 

By all means show me your Minkowski diagram. I've just not seen one for motion in two dimensions.

Invariant distance to a star? Sorry, but for two reasonably comoving objects, the distance between them is very frame dependent. The proper distance is invariant, but he didn't say that. I think he meant that, since he's talking about returning to a rest frame to determine 'real' length, instead of using the term proper length. I'm not claiming that the proper length of a given bumper car changes when it's going around the ring.

Normally, a narrow ring (not a disk or wide band) will simply contract to a smaller radius when spinning. It only breaks in this scenario since we're forcing it to fit in a track that is a larger radius. A 5 km track will not hold a 4 km hoop without the hoop breaking. It's not a rubber band.

 

Here's another exchange with the most knowledgeable person I've met about the Loedel perpsective:

"
No, "proper time simultaneity" is an undefined term, and I would not recommend trying to propose a personal definition for the term. "Proper time" is an invariant that is defined only on a given worldline and "simultaneity" is frame-variant and is defined over all spacetime so "proper time simultaneity" is nearly as oxymoronic a name as could be conceived.

answered Jan 13 at 18:28

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Dale
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• 1
  I did not see this answer coming but it is a great answer. As you may know, many of my previous questions were about this and I think I finally have closure. – ralfcis Jan 13 at 21:51
• 
  If my other question about "proper age difference" gets opened up I can correct it based on the info here. I just need to replace everywhere I use the adjective "proper" with the term "half-speed perspective". I can also go back and correct any wrong terms in my other questions can't I? Is half-speed or middle or balanced perspective an acceptable term because I will use it quite often in future questions. – ralfcis Jan 14 at 0:58 Delete
• 
  I think it would be fine, early in the question, to say “I will use the term ‘half speed perspective’ to refer to the reference frame where Alice and Bob are traveling in opposite directions at the same speed”. – Dale Jan 14 at 1:14
• 1
  After digging for info to answer my previous question I've come up with the perfect term for everything previously labelled as "half-speed". This sentence on Loedel diagrams in wiki, "Suppose there are two collinear velocities v and w. How does one find the frame of reference in which the velocities become equal speeds in opposite directions?" So half-speed is the Loedel reference frame so I'll use Loedel perspective, Loedel simultaneity, and Loedel velocity in all my future posts and expect everyone will know what I'm talking about. Case closed.

 

Halc, really? Yeah go argue with him now. Anyway I've put the link to my Md in a previous retort. Let's just simplify everything to the basic discussion about whether length contraction is a real physical phenomenon or illusion. Still none of you will research this on the PSX. That just boggles my mind how much you collectively don't really want to understand this because you're so sure you already know it.

 

I have not understood your theory. I see that you are against Length contraction, you use parallax to measure the length between 2 points. But then? What else?

 

"you use parallax to measure the length between 2 points"

Hoo boy. Not usually. It was just an example to answer your original question. I guess you're not seeing the connection between the two. I can give you a summary of the main points but then I'd be obliged to post 50 pages of math that are posted on another forum. I'd rather scope out this place for experts first then work my way in slowly one topic at a time.

 

Ralfis;

Left:
With no lc of B-stick,
A measures B-stick length as d.
B measures A-stick as d/gg.
One order of g too short.
Right:
With lc of B-stick,
A measures B-stick length as d/g.
B measures A-stick as d/g.
Reciprocal lc.
If you see an error, point it out.
Axis of simultaneity requires lc to work!

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The error is why make up length contraction when you don't need to? I have no Bx axis. Bx would be my line of perspective simultaneity if I wanted to know earth time from Alice's perspective. I don't even care about that as I use Loedel simultaneity for everything. At and Bt share the same Ax axis in my method. You guys keep saying that's not right when you really mean that's not how relativity does it which is the only way it can be done as proven over a 100 yrs. You can't recognise the illogic of that statement because you don't want to even entertain the possibility that there is another way of thinking about it that gives the same results. The only question is it the best way? You'd need to fully understand both methods to determine that and so far I have no one interested.

I don't like your style of Md's. I like numbers. I like my simple .6c Minkowski diagram where Alice goes to a planet 3 ly away in 4 of her yrs. Does she care that relativity says she's only travelled 2.4 ly of her distance? No, all her star charts were made using techniques that measure proper distance like the parallax method or the supernova flare method. You think every ship is going to have an infinite number of star charts based on their relative velocities to everything else but a common earth frame? That 2.4 ly distance gives her no valuable information except that according to wiki relativity she hasn't exceeded c from all perspectives.

No, that planet is 3 ly away. It only looks closer because she is using her watch to measure the distance to it. She gets there in 4 yrs according to her watch. Her watch, her starchart and her planet all co-located. Why would she care what earth has to say about it? Her Yv = .75c while her v = .6c from earth's perspective which she can measure using the Doppler shift ratio. I don't even care about reciprocal time dilation because I don't need to view this problem considering the ship is stationary and the entire universe is moving by it. That may be theoretically true but it's physically false. The sun does not revolve around the earth and the earth does not revolve around a proton in the LHC so why even bother tying to look at things that way. The answers are the same but what do we care what a proton's or a muon's perspective is?

The Md is constructed by rotation of one coordinate system over another pivoting at the origin. But it doesn't need to be done the way Minkowski did it. There's Epstein's and Loedel's rotations as well. Minkowski's method is fudged to have all the c lines conveniently overlap. You can convince people Minkowski rotated his ct' and x' axes in opposite directions but that's also not necessarily true. I'm not going to waste my time explaining how that's possible to people who don't want to know. If I was going to set up shop here, I'd definitely put most here on my ignore list because, as I've learned with you, it's a fruitless endeavor to hope that one day they may have something interesting to say, change their views or honestly admit mistakes in the face of incontravertible mathematical proof . I learn way more trying to explain things to cranks because they know nothing and concepts must be presented much clearer.

PS. One way I'd be convinced that length contraction is real is if Brian Greene's depiction of a taxi going through a city and the distortions he says it would see could be actually seen. This goes back to the original question in this thread and I can think of no experiment in which that would be possible.

 

It is closer.
Why doesn't x' = vt'?
Yv = .75c, here you are just rearranging terms, for what purpose?
Are you going to spend another 10 yrs. with the 'twins', trying to convert someone?

 

At t' = 3 the ship has .75 ly left to travel but if you believe in length contraction the distance is seen to be only .6 ly. Sure that would explain to a relativist why your destination looks closer as .75 ly is greater than .6 ly. You're comparing apples to oranges, x to x'. That .6ly distance should be from the ship's perspective and the only way it can be seen is the planet appears closer than EARTH's watch is telling him it should. The ship's watch is saying the ship is only 1 yr away but the earth's watch is saying he's 1.25yrs away. So 1 yr sounds less than 1.25 yrs so objects in his front view look closer than they would be from earth's coordinates. This is again comparing apples to oranges, t to t'. Closer is a term of relative comparison but you're confused on what you're comparing it to. The magnitudes of the numbers look different but they're actually the same from the Loedel perspective. 1/2 = 4/8 even though 4/8 uses apparently bigger numbers.

So in t'=1 yr, the ship would cover that x'=.6 ly to get to his destination. v=x'/t' = .6c. From the earth's perspective t=1.25 yr and x=.75 ly so v=x/t =.6c also. So far no problem .But without length contraction from Alice's perspective of her watch and her star chart, Yv = x/t' = .75c. She may have further to go (.75ly), but she does it at a faster velocity (.75c) so she is still 1 yr away (her time) from her destination whether you believe in length contraction or not. The simple math of using her perspective velocity Yv gets rid of the need for the false concept of length contraction. A little bit of term rearrangement gets rid of an entire foundational concept of relativity. A concept Einstein needlessly adopted from Lorentz. Unfortunately your brain is screaming to you to ignore this trivial math trick and continue believing c can't remain constant for all perspectives without the concept of length contraction. I say you can lead a horse to water but you can't make him think. Here's the Md

https://photos.app.goo.gl/jv4i7F5wRz8Bb8cE8

As usual you just pick and choose maybe one sentence you recognize out of all that I've written and ignore the rest. That's why it's useless for me to discuss anything with you over all these years. Forget about 10 yrs, 100 yrs wouldn't be enough.

 

ralfcis,

Believe it or not, I think I understand what you believe regarding length contraction. For example, with the barn-pole paradox, you do not believe the two doors close simultaneity in the barn frame. Instead, you believe the first event "BACK door closes momentarily" happens while the other end of the non-length-contracted pole is still sticking out the front door, and you believe the second event "FRONT door closes momentarily" happens at a later time, when the other end of the non-length-contracted pole is sticking out the back door. What you are doing here, whether you realize it or not, is you are making the pole frame the preferred frame. That is the sequence of events in the pole frame, but you are thinking it also is what is really happening in the barn frame.

Consider another pole that is moving in the opposite direction as the first one, but at the same speed. Now you would have us believe that the first event "FRONT door closes momentarily" happens while the other end of the non-length-contracted pole is still sticking out the back door, and you would have us believe the second event "BACK door closes momentarily" happens at a later time, when the other end of the non-length-contracted pole is sticking out the front door.

But what what happens if you consider both poles moving through the barn frame at the same time? If you are correct in your ideas, then the doors would not be able to close, because regardless of the order, the doors will hit one or the other pole. That is where you depart from SR. SR says both doors can close simultaneously in the barn frame, because both poles are length contracted in the barn frame. Do you see now that relativity of simultaneity (ROS) is not sufficient to explain both pole's length contraction effects? Or do you still think that both doors cannot close on the two poles? That is the difference between length contraction being real, or not.

 

Neddy I'm going to put you on ignore. You're confusing the concepts of the doors close simultaneously for an instant from a perspective and the idea the pole has shrunk into the barn. As I said, go to the physics stack exchange or watch the Brian Greene video over and over. I'm not interested.

PS. That was rude. I will answer this one last question for you. Each pole direction is its own frame so the barn doors are now two swinging saloon style doors as opposed to a single door at each end.

 

ralfcis: If you want to confer with the experts, there are no better experts than those at physicsforums.com.
Post your questions there; you will definitely get the answers you're looking for.

 

If you want to ignore me, that is fine, but unwarranted. In my post, I use two poles to show that if the doors were not really closing at the same time, then we would know it because the doors would have to hit one or the other pole. If the doors do close without hitting either pole, then length contraction is real, and not just an artifact of the doors closing at different times. But this is obviously too much for you to take, even though you are the one who brought up that you don't think length contraction is real in the first place.

I've put you on iggy as well. Later.

 

No I won't Dave. They don't tolerate personal theories. I was permanently banned 4 yrs ago when I asked my first question without knowing the answer.

 

No. You got banned for challenging well-established theory and observation. Despite being given correct answers, you argued them.

They don't perma-ban members for asking one question that they don't know the answer to; they perma-ban members who insist their unsupported ideas overthrow not just well-established science - but also - not to put too fine a point on it - applied worldwide technology that can only work if that well-established science is correct.

So there's no contention here about how relativity works as per established theory and observation, you just personally don't agree with it.

OK, I don't really need to get involved in that.

Frankly - neither do you, in this thread. Unless you're directly supporting the OP's ideas, you really should start your own thread.