Question about “Real And Virtual Pendulums Swing As One In Mixed Reality State”

[lupus_in_fabula]

I have tried to find more information about this experiment because, as a layman, I can’t picture how the test setup looked like. Can anyone help me in giving a rudimentary step-by-step explanation about what they basically did? It sound very interesting, but I find it hard to create a clear picture in my head about what actually took place.

For instance they “[...] sent information about the virtual pendulum to a motor that influenced motion of the real pendulum.” What does that actually mean? Or the following: “When the lengths of the pendulums were similar, however, they 'suddenly noticed each other, synchronized their motions, and danced together indefinitely'.”

Here’s the link: http://www.sciencedaily.com/releases/2008/03/080310131511.htm

[lupus_in_fabula]

I see there are no takers :(

To clarify my question: when the 'information' from the virtual system is sent to the real pendulum, how can that not bee seen as a 'specific instruction' for the pendulum to swing in accordance to the virtual one? How can the real pendulum 'know' the momentum of the virtual pendulum if not by redefining 'knowledge' into 'direct instruction about how to swing'?

[bjornart]

It's a setup like this, only with one of the pendulums virtual, and with the ability to change the length of at least one.

The information transmitted in the real world is the energy in the not-perfectly-rigid stand. The virtual set-up simulates this.

It's not a "direct instruction about how to swing" because information is passed both ways, the system behaves like it would if there were two real pendulums.

The point of the exercise is as the article says.
"Computers are now fast enough that we can detect the position of the real pendulum, compute the dynamics of the virtual pendulum, and compute appropriate feedback to the real pendulum, all in real time," said Hubler

[bjornart]

In case that's unclear, here's a simpler setup that doesn't have the same complexity and virtuality.

Imagine the "virtual pendulum" is much more massive than the real one, the influence is now aproximately one way, and all you have to do is send occilating instructions to the motor. No registrating the movement of the real pendulum and no feedback and calculation of the movement of the virtual pendulum.
In this setup you can obviously say that all you are doing is instructing the real pendulum on how to swing.

[lupus_in_fabula]

Imagine the "virtual pendulum" is much more massive than the real one, the influence is now aproximately one way, and all you have to do is send occilating instructions to the motor. No registrating the movement of the real pendulum and no feedback and calculation of the movement of the virtual pendulum.
In this setup you can obviously say that all you are doing is instructing the real pendulum on how to swing.

Ok, thanks for the clarification. I think this is a case where actually watching the experiment take place would give a much, much, better picture about what’s actually going on than reading an overview about it. But I think I kind of understand the general message.

[69dodge]

To clarify my question: when the 'information' from the virtual system is sent to the real pendulum, how can that not bee seen as a 'specific instruction' for the pendulum to swing in accordance to the virtual one? How can the real pendulum 'know' the momentum of the virtual pendulum if not by redefining 'knowledge' into 'direct instruction about how to swing'?

I would assume that the 'instructions' take the form of forces. A force directly affects acceleration, and only indirectly affects velocity and position. That is, the 'instructions' to the pendulums don't look like, "be here now." They look like, "slow down a bit now" or "speed up a bit now." And then, the net result of all those changes in speed at appropriate times turns out to be that after a while the two pendulums end up swinging together.

[lupus_in_fabula]

I would assume that the 'instructions' take the form of forces. A force directly affects acceleration, and only indirectly affects velocity and position. That is, the 'instructions' to the pendulums don't look like, "be here now." They look like, "slow down a bit now" or "speed up a bit now." And then, the net result of all those changes in speed at appropriate times turns out to be that after a while the two pendulums end up swinging together.

Cool, that’s what I think I was looking for. Damn, I wish I was smarter, or at least had better visualization capabilities, but that makes an awful lot of sense to me.