SPECIAL RELATIVITY KILLED BY A RIVET

[Pentcho Valev]

The bug-rivet paradox:

http://hyperphysics.phy-astr.gsu.edu/Hbase/Relativ/bugrivet.html
"In an attempt to squash a bug in a 1 cm deep hole, a rivet is used. But the rivet is only 0.8 cm long so it cannot reach the bug. The rivet is accelerated to 0.9c."

In the rivet's frame, "the end of the rivet hits the bottom of the hole before the head of the rivet hits the wall" - the bug is squashed. In the bug's frame, "the rivet head hits the wall when the rivet end is just 0.35 cm down in the hole" - the bug remains alive.

Needless to say, the bug being squashed in the rivet's frame and alive in the bug's frame is fatal for special relativity so Einsteinians resort to an idiotic ad hoc "requirement" - the rivet shank length miraculously increases beyond its at-rest length and poor bug gets squashed in both frames, Divine Einstein, yes we all believe in relativity, relativity, relativity:

http://math.ucr.edu/~jdp/Relativity/Bug_Rivet.html
John de Pillis Professor of Mathematics: "In fact, special relativity requires that after collision, the rivet shank length increases beyond its at-rest length d."

Yet even the idiotic length-elongation requirement does not save special relativity. As judged from the bug's frame, when the head of the rivet hits the wall, an enormous stretching force will separate head and shank, that is, the rivet will be broken. The bug will be squashed by a headless shank.

This "enormous stretching force" is absent as judged from the rivet's frame, and the bug is squashed by an undivided rivet.

The contradiction is even more clearly seen in the pole-barn scenario:

http://physics.bgsu.edu/~stoner/P202/relative1/sld015.htm

If the pole is replaced by a rivet whose head cannot pass through the door, then we have head-shank separation as judged from the barn's frame and no separation as judged from the rivet's (pole's) frame. Reductio ad absurdum par excellence. One of Einstein's 1905 two postulates is false.

Pentcho Valev

[Dirk Van de moortel]

Pentcho Valev <pva...@yahoo.com> wrote:
> The bug-rivet paradox:
>
> http://hyperphysics.phy-astr.gsu.edu/Hbase/Relativ/bugrivet.html

That is completely wrong.
On two occasions I mailed them to explain, and twice they ignored it.
Too bad. It serves as an excellent example for learning how not to
truzt teh Internetz to learn about the world. Suits you, Sir.

Dirk Vdm

[Y]

Dirk: Is it wrong because what is described is a material contraction, and SR predicts no such thing ?

-y

[Dirk Van de moortel]

(Sent October 2009 and June 2010)
==================================
Hi Rod,

I just noticed your little article
http://hyperphysics.phy-astr.gsu.edu/Hbase/Relativ/bugrivet.html
where you correctly calculate the times of impact for the rivet's
head resp. end on the wall resp. bug.
For both viewpoints you conclude with the phrase "The
paradox is not resolved".

On a few occasions this page has been brought up in Usenet
articles (e.g. sci.physics.relativity) and weblogs by people
proving that "there are indeed unsolved paradoxes in special
relativity", and that "therefore special relativity must be bogus".
Each time we must explain that the "internet is a bad place
to study a subject".
In this case that's a pity, since your hyperphysics site is
rather good.

So, wouldn't it be a good idea to show the real solution to the
paradox by explaining that the paradox is not to be solved by
considering the time order of spacelike separated events, but
rather by considering the propagation time of signals through
the rivet's material, and the fact that there is no such thing as
rigidity?

------

1) In the part "Transforming the times to the bug's frame of reference",
you write:
| "The bug disagrees with this analysis and finds the time for
| the rivet head to hit the wall is earlier than the time for the
| rivet end to reach the bottom of the hole. The paradox is not
| resolved."

I propose a reformulation to something like this:
| "The bug disagrees with this analysis and finds the time for
| the rivet head to hit the wall is earlier than the time for the
| rivet end to reach the bottom of the hole. However, when the
| head hits the wall, it takes some finite time for this disturbance
| to reach the end of the rivet, during which time the end keeps
| moving and is able to reach and squash the bug.
| The paradox is resolved.

------

2) Further you write:
| "All this is nonsense from the bug's point of view. The rivet

| head hits the wall when the rivet end is just 0.35 cm down

| in the hole! The rivet doesn't get close to the bug."

Again, the rivet *can* get close to the bug and squash it, provided
the signal of the head's collision with the wall has insufficient
time to reach the front of the rivet and stop it before it reaches
the bug. Such signals usually propagate through a material at
the speed of sound in that material, which is far below the 0.9c
of the setup.

------

3) In the part "Transforming the times measured in the bug's frame
of reference to the rivet frame", you write:
| "Transforming times from the bug frame to the rivet frame
| gives a time for the end to reach -0.35 cm before the rivet
| head hits, and even suggests that it reaches the bottom
| of the hole before the rivet head hits. The paradox is not
| resolved."

Again, there is nothing wrong here. In the rivet frame, the end
does indeed squash the bug before the head hits the wall.
When the bug is squashed, the head part of the rivet keeps
moving forward, as the signal from end to head needs a finite
time to reach the head.

------

In reality, there will be two signals in the rivet going in opposite
directions. Upon the bug-squash-event, one signal goes from
the rivet's end (bug) to the head, trying to tell it to stop.
Upon the wall-hit-event another signal goes from the rivet's
head to the end, trying to tell it to stop.
These signals will meet each other somewhere in the body
of the rivet.
The difference between the frames of reference lies merely
in which events happen first.
The bug gets squashed.
The paradox is solved.

I hope you will consider taking this into account in some
future new version of this page on your (otherwise excellent)
site.

Cheers and kind regards,
Dirk Vdm

[Pentcho Valev]

On Monday, July 1, 2013 6:51:37 PM UTC+2, Dirk Van de moortel wrote:
> Again, the rivet *can* get close to the bug and squash it, provided
> the signal of the head's collision with the wall has insufficient
> time to reach the front of the rivet and stop it before it reaches
> the bug. Such signals usually propagate through a material at
> the speed of sound in that material, which is far below the 0.9c
> of the setup.

Terrific! Since the speed of the signal is "far below the 0.9c of the setup", the front of the rivet can travel unrestrained through a very long distance, that is, if the hole is bottomless, the rivet will become... how long, Clever Moortel?

Pentcho Valev

[Odd Bodkin]

On 7/1/2013 12:28 PM, Pentcho Valev wrote:
> Terrific! Since the speed of the signal is "far below the 0.9c of the setup", the front of
> the rivet can travel unrestrained through a very long distance, that is, if the hole is
> bottomless, the rivet will become... how long, Clever Moortel?

I don't think a very long hole is case at hand. If the hole is
bottomless, then no amount of length contraction will make the end of
the rivet bottom out and the bug lives in all frames. There is still no
contradiction. If you're trying to make a contradiction, are you
supposing the hole is shallow in one frame and bottomless in another
frame? I'm not following what you're thinking.


--
- Odd Bodkin, maker of fine toys, tools, tables

[Pentcho Valev]

You are not but Clever Moortel is, and is very ashamed!

Pentcho Valev

[Dirk Van de moortel]

Nerer mind. Communicating with Valev is like pissing onto
a black hole.

Dirk Vdm

[Pentcho Valev]

On the contrary I was very communicative and asked you a simple question, Clever Moortel. The front of the rivet is travelling at 0.9c and the signal that is to tell the front to stop is chasing it, as you informed us, at the speed of sound. Now the question: When will the signal reach the front and how long will the rivet have become then?

Pentcho Valev

[Odd Bodkin]

On 7/1/2013 1:55 PM, Pentcho Valev wrote:
> On the contrary I was very communicative and asked you a simple question, Clever Moortel.
> The front of the rivet is travelling at 0.9c and the signal that is to tell the front to
> stop is chasing it, as you informed us, at the speed of sound. Now the question: When will
> the signal reach the front and how long will the rivet have become then?

Oh, I see what you're driving at. If the front of the rivet is traveling
faster than the speed of sound, then the signal traveling from the back
end of the rivet will never outrace the front of the rivet. Is that what
you're saying?

[Odd Bodkin]

I thought about this a bit, and the sound signal will always have to
travel faster than the end of the rivet.

In the frame of the wall, where the rivet is going at 0.9c, the speed of
the sound signal will be
vs' = (vs + 0.9c)/(1 + (0.9)vs/c)
right?
vs is the speed of sound when the rivet is at rest, about 6000 m/s. I
think we'll eventually want to write that as 0.00002c. Did I do that right?

So suppose the rivet expands from L to L' in the time it takes for this
signal to get to the other end. That time is
L'/vs'
right?

Now in that same time the front of the rivet is going 0.9c a distance of
L'-L. So that time is also
(L'-L)/(0.9c)
right?

So equate these two times, like so
(L'-L)/(0.9c) = L'/vs'
and we can surely find out L' if we know L and vs.
(vs')(L'-L) = (0.9c)(L')
or
(0.9c)/(vs') = (L'-L)/L' = 1 - L/L'
or
L/L' = 1 - (0.9c)/(vs') = 1 - (0.9c)(1+(0.9)vs/c)/(vs + 0.9c)
and now we can put in the value for vs
L/L' = 1 - (0.9)[1+(0.9)(0.00002)]/(0.00002 + 0.9)
and I think the rest is just putting numbers in the calculator
L/L' = 1 - (0.9)(1.000018)/(0.90002) = 0.00000422
which means L'/L = 236,847. That's pretty long alright.
I hope I did everything right.


If you put a number in for L, you can find L', and then you can also
find the time for the signal to travel.

[Odd Bodkin]

On 7/1/2013 5:57 PM, Odd Bodkin wrote:
> which means L'/L = 236,847. That's pretty long alright.

Thinking about this just a little more, I think this means that the end
of the rivet never really stops. Anything that would stretch a metal
236,000 times would end up just dissociating the metal from itself,
turning it into vapor, and then the speed of sound in steel doesn't
apply anymore anyway. It sounds like the rivet vaporizes and the bug
dies from being scorched.

[xxe...@comcast.net]

xxein: First of all, I can agree with you. But Einstein's postulates are a good measure. All he needed to do was add a third. To include that frame of reference depends on the aether he can't prove that exists but had to consider it and got lost within it. So he eventually he sort of discarded it. But it nagged him until he died.

[Tom Roberts]

On 7/1/13 7/1/13 10:28 AM, Pentcho Valev wrote:
> The bug-rivet paradox:

> [...]

This is among the worst teaching examples there are, because no matter what the
bug dies. Indeed, stopping the rivet releases more energy than an atomic bomb,
making survival of the bug a very silly question.


Tom Roberts

[Pentcho Valev]

Honest Roberts, your "atomic bomb" counterargument is just as relevant as a counterargument stating that, in Einstein's scenario where a clock moving at, say, 0.9c suddenly turns around and returns at 0.9c again, the turn-around acceleration destroys the clock making its running "a very silly question".

Pentcho Valev

[Y]

Valev: I agree. Resorting to physical or material conclusions, kind of defeats the 'geometry' of the conclusions. All conclusions should be restricted to geometric rigors, since the model is geometric.

Roberts: Don't you confuse nature and models when you leap from geometry to E released or absorbed ? At least, you leap models from an SR domain to a GR domain. Maybe this is ok ? Is it ok to do that? It would seem to me that when assessing the consistency of one model, use of other models should be precluded. Internal consistency here is what is being sought.

-y

[Tom Roberts]

On 7/2/13 7/2/13 2:59 AM, Y wrote:
> Valev: I agree. Resorting to physical or material conclusions, kind of
> defeats the 'geometry' of the conclusions. All conclusions should be
> restricted to geometric rigors, since the model is geometric.

But the ORIGINAL "bug-rivet paradox" involved the material properties of the
rivet in an essential way.

> Roberts: Don't you confuse nature and models when you leap from geometry to E
> released or absorbed ?

No. Energy is part of the model.


Tom Roberts