Synchronization

Anyone have the science behind this? Looks like it could be an awesome lesson!

Don't know what's going on there. Takes them a while to get to the correct speed or something. Anyway, it's cool after I had a couple nice after work drinks.

Sorry if this is a bit drawn-out, but here goes:

Each metronome produces a surge of energy as it's pendulum comes to a stop at each end of it's swing. This energy is transfered into the platform and travels through the platform and "couples" into each of the other metronomes.

Initially, these surges or pulses are out of synch and thus out of phase (the pulse is actually a wave with a positive and negative component). These waves interfere with each other, and at each metronome the result of the interference adds or subtracts energy from the metronome. This in turn changes the interference pattern, which in turn adds or subtracts a little more energy from each metronome. This continues until a balance of positive and negative forces is achieved, which just so happens to coincide with synchronous swinging of the metronomes.

Setting the rig on the table dampens the exchange of pulses and makes for little or no interference.

BTW, This phenomenon is seen in all sorts of oscillating systems- electronic and mechanical, and can be a big problem.

Correct me if I'm wrong but this is also a huge component of bridge building and figuring out how much they need to be able to withstand? If a whole bunch of people walk across the bridge at the same time and they happen to walk in sync (which is quite common for some reason) the stress put on the bridge can reach somewhat unimagineable proportions.

SoLo,

Thanks for the explanation! Very useful!

I hope I'm not the only person who's reminded by this of the minimalist music of people like Steve Reich. Anyway, I'm kind of tempted to try this myself, except I've only got one metronome.

Yes. Thank you Solo. (May the force be with you.)

That play button is poorly placed.

I had a sense of satisfaction when the metronomes started to syncronize. It was like a rush of fulfilment.. Does that mean I am OCD? oh dear.

My pleasure :) The bridge thing is related - the concern with bridges (at least theoretically) has to do with causing the bridge to resonate- that is, to vibrate at a frequency where all the parts of the bridge are moving together (like the metronomes). The people provide the energy (in the metronomes, springs are the source of energy). If enough energy is fed into the resonating bridge, the mechanical stresses could become destructive. In practice, the mass of the bridge dissipates the energy before it can become a problem.

As for duplicating this without metronomes- if you can locate two or more mechanical clocks (or watches), just set them close together on a thin sheet of wood or even heavy cardboard, held up by cans (like in the video). Before long, they will be ticking in unison.

Mr. Pumpernickel, you are thinking of the Millenium Bridge, which was explained in the Embarrassing Engineering article a couple of weeks back. http://www.mentalfloss.com/blogs/archives/14030 They called it "synchronozed footfall".

SoLo, thanks for that quick lesson!

Nope, not thinking of the Millenium Bridge, didn't even know that it was a victim under the same phenomenon. I heard it quite some time ago, can't quite remember from where.

Synchronization also works well with harmonics (whole-number multiples) of the fundamental, and is widely used in electronics to generate various frequencies from a master oscillator (before things went digital, anyway). I'd like to see the metronomes where one was set to half or double the frequency of the others.
In old TVs, synchronization was used to lock the vertical and horizontal hold to keep the picture from rolling or tearing. A local oscillator was adjusted until it locked onto the pulses at the end of each line.

Good explanation SoLo, glad you mentioned the clocks too as it was Huygens back in the 17th Century that first discovered this with pendulum clocks, he called it entrainment.

I'd like to add that this phenomena is seen in biological systems too.

Good to see my old uni up on youtube! entertaining people too!

SoLo, thell us more about the Millenium falcon bridge :D

I agree with the Steve Reich comment. Check this out: http://www.youtube.com/watch?v=WnM_o-oj5u0

For more on resonance and synchronization, read up on Nicola Tesla. He believed that all structures have a resonant frequency. According to Tesla, once a structure began to resonate at such a frequency the structure would multiply that resonance upon itself until it ultimately failed. In fact, he claimed to be able to level entire buildings with a simple device that he could "tune" to these frequencies, and he even claims to have put it into practice only to be forced to destroy one such device with a sledgehammer mid-experiment because the building he was in was in danger of collapse.

(I'm pulling this information from memory, so I may be off on some details. Anyone wish to elaborate?)

Jason E., that was the topic of a Mythbusters episode some time ago. It was busted, but they did get some interesting results from placing an oscillator on a bridge.

http://kwc.org/mythbusters/2006/08/episode_60_earthquake_machine.html

This is from the new DVD "Physics Students Gone Wild"

Additive resonance in complex structures is an interesting topic for sure... often the competing dynamics results in a mish-mash that isn't too much of a problem, but sometimes, things come together to wreak havoc- as in the Tacoma Narrows Bridge- now there was some serious harmonic action! As for the Falcon...

Chewy and my brother Napoleon and I worked over the bridge on the MF a while back. The jump-drive initiator finally went totally ka-put (no matter how hard it was hit, the darn thing still wouldn't pop over). I found lots of old biosnax under the boards too... (Chewy's, though he'll rip your head off before admitting it). Anyway, all the red lights are now blue, the green ones are magenta, and the tiny yellow ones are now black (and mounted to a black panel- Hotblack gave 'em to me out at the end of the universe). Thanks for asking! :)

kittymeow: you might be thinking of ligeti...

http://www.youtube.com/watch?v=X8v-uDhcDyg

I wasn't aware of that piece by Ligeti, actually. I wonder if he did another piece with 100 metronomes on a bridge.

j0s3ph said: "I’d like to add that this phenomena is seen in biological systems too."

Obviously breathing and heartbeats would be a start... then going deeper, there's that strange ooga booga biorhythm science out there..

I wonder if this kind of thing is present in airplane engines?

Thanks for the info, SoLo.

@j0s3ph: "I’d like to add that this phenomena is seen in biological systems too."

Check out "menstrual synchrony" or the McClintock Effect: The Straight Dope, Wikipedia

There are really interesting applications of vibrations that people rarely realize unless they are into science. A quick google search of flutter will show you videos of vibration in brings or air plane wings that is dependent on the wind speed. The cool bit is that the vibration is perpendicular to the wind. Really cool stuff.

Beat phenomena is also really cool. An examples would be to set up two pendulums with a spring connecting them at the base. If you start one pendulum swinging, the amplitude of oscillation will slowly decrease and the other pendulum will slowly start to oscillate. Eventually all of the energy will transfer to the opposite pendulum. They will exchange energy back and forth until all of the energy is dissipated by mechanical methods (friction, etc).

Woo. Thats pretty sweet.

That's awesome. I'm totally tempted to go out and buy five metronomes so I can do it at home. I'll have to put it on the list of things to do on a rainy Saturday after I win the lottery.

Now...what's it good for?