Question in relativity

[discountbrains]

My question is simple: Consider a rod of length L moving straight from A to B at 0.99c. L is much shorter than distance from A to B. An observer sitting at right angle to the motion can measure what he thinks L is at this moment. The question is: Now, what does he measure for the distance from the leading end of the rod to B and trailing end to A? Should these measurements be the same as when the rod is at rest or should they be greater or what? I was directed to Wiki which showed several discussions on length contraction that made their authors famous, but nothing about my question. I now think I have stumbled on something profound here. I think I could put together  enough discussion to write a paper on this.

[Strange]

35 minutes ago, discountbrains said:

The question is: Now, what does he measure for the distance from the leading end of the rod to B and trailing end to A? Should these measurements be the same as when the rod is at rest or should they be greater or what?

One or both will obviously be greater. The length of the rod has decreased; the distance between A and B has not.

36 minutes ago, discountbrains said:

I now think I have stumbled on something profound here.

The depth of your ignorance, perhaps?

[Markus Hanke]

45 minutes ago, discountbrains said:

I now think I have stumbled on something profound here.

Yes, you have stumbled across your own ongoing inability to stop looking at time and space as being independent and absolute. This has been known to not be workable for well over a 100 years now - it’s time for you to catch up at last, don’t you think?

Based on the fact that you seem to have completely ignored everything that was already explained to you in the other threads you had opened on this topic, I see no reason to go through the actual calculation again. It would serve no purpose, since you’ll ultimately ignore it anyway. Also, had you actually read the Wiki article, you’d be able to do the numbers yourself - it’s just the usual length contraction formulas, plus a bit of trigonometry, since your observer sits off-side from the line of motion.

Instead of wasting our time here, let me ask you something in return - is there anything at all that we could say to you or show you, that could convince you of the validity of the theory of relativity? It seems obvious that giving actual answers to your questions isn’t enough. Please just be honest - if there isn’t anything we can say that would convince you, then that’s fine - at least we’ll all know where we stand.

45 minutes ago, discountbrains said:

I think I could put together  enough discussion to write a paper on this.

Well, why don’t you? No one is going to stop you from doing this. Perhaps it would be a very illuminating exercise for you.

Edited July 7, 2018 by Markus Hanke

[Janus]

If The distance between A and B is d, as measured by someone at rest with respect to these points, then the distance from A to B is D, then  D= ~1/7 d,  where d is the distance between A and B as measured by someone at rest with respect to A and B.

Thus the total difference between L and  D in the rod frame is  D-L or 1/7d-L

If length of the rod as measured from the rest frame of A and B is l, then l = ~1/7 L

and the difference between  l and d is  1/7 D-l

Plugging some numbers in, if L=10 light sec and  and d=100 light sec,

then D= 14.29 light sec and the difference between the length of the rod and the distance between A and B will be 4.29 light sec according to the rod.

And l = 1.429 light sec, and the difference between the length of the rod and the distance between A and B will be 98.57 light sec according to someone at rest with respect to A and B.

 

The problem is that you use the phrase "at this moment", when talking about comparing measurements made in two different frames.

And, as I have tried to point out to you before, you have to  take the Relativity of Simultaneity into account when making these type of jumps between frames.

So the question I'll put to you is:  Do you understand the concept of the Relativity of Simultaneity?   Until you do, resolution of this scenario will continue to puzzle you.

[mathematic]

In the reference frame of the moving rod, its length is unchanged.  In the reference frame of the observer it is much shorter.

[discountbrains]

ok, I got some concrete answers this time pointing out my error. I see on the Brehm diagram where 2 different times are on one axis (same frame) and separated on another. I believe I was trying to think of distances from the rod ends to A or B as independent of the relativistic effects on the rod. At high enough speeds the rod getting shorter would make these distances greater. Yet, what if 2 rockets are both traveling 0.9999c on the same path with one nearly landing on planet B and the other is just leaving planet A. A stationary observer would think the 2nd one would be almost running into the 1st and they would both be many, many miles from each planet. I guess that's all possible though. Why am I even saying this? Both would be so massive this not even possible.I'm really bored with this whole thing.  What about parallel currrents in two parallel wires?

[Strange]

5 hours ago, discountbrains said:

I'm really bored with this whole thing.

Bored by being proved wrong. Again.

[discountbrains]

I can't find where to delete my ending question about wires. It doesn't matter anyway..... Proven wrong?... You yourself answered my question. I could scroll up and get the quote. As I showed before the math doesn't really work out though for calculation of distance from A. This is all useless information anyway: the mass of the objects would be unrealistic. Relativity works well for some things and maybe not so well for others. Isn't there still a conflict with quantum mechanics?  

[Eise]

11 hours ago, discountbrains said:

Relativity works well for some things and maybe not so well for others. Isn't there still a conflict with quantum mechanics?

You do not seem to be prepared to learn. In another thread I reacted and told you that Dirac was able to predict the spin of the electron and anti-matter, by making quantum mechanics consistent with special relativity. No conflict here. Your examples are all related to special relativity.

The problem you seem to have heard of, is the combination of general relativity with QM. Normally there is no problem: in QM one can neglect gravity because it is much too weak; in cases where we need GR to explain phenomena (strong gravity or very precise measurements, for weak gravity Newton suffices), there are such huge concentrations of mass that we can neglect quantum effects. (We do not need QM to describe the movement of the moon.)

But there a 2 notorious exceptions: the singularity of black holes, and the very beginnings of the big bang. There the sizes involved are so small, that QM must be taken into account, and there the combination fails.

So we are very aware of the domains where we can apply QM and GR. In their respective domains there is no problem. SR and QM are proven to the bone: if you think you find an error, you can be sure you made an error in your thinking. GR is proven not so much, because the situations in which its results deviate from classical Newtonian gravity are not so abundant. But it passed all tests until now (gravitational redshift and time dilatation, gravitational waves, ...) so we are pretty sure GR is correct in its domain.

[swansont]

17 hours ago, discountbrains said:

This is all useless information anyway: the mass of the objects would be unrealistic.

Um, what? We accelerate objects to near light speed all the time. Their masses do not become unrealistic.

Quote

Relativity works well for some things and maybe not so well for others. Isn't there still a conflict with quantum mechanics?  

SR is incorporated into QM already. It's gravity at a scale where a quantum theory would be needed that is the problem. In the grand scheme of thing, this is at an extreme scale of size. i.e. for most situations, a quantum theory of gravity is not needed.

[Strange]

18 hours ago, discountbrains said:

As I showed before the math doesn't really work out though for calculation of distance from A.

You never “showed” anything; you just made claims based on ... well, nothing. 

[discountbrains]

I resolved my error myself. I was thinking of the distance from the leading end or leading object to it's destination 'B" to a statioonary observer as being a static measurement. I didn't consider that  the length L would be shrinking to him as the speed increased. Also Wiki gives 3 ways of calculating L. The (x₂-x₁)gamma I've seen before and used before. My text or other sources don't use this. It leads to errors.