The Chaos Machine (Double Pendulum)
Intro: The Chaos Machine (Double Pendulum)
Every physics department needs a double pendulum, so here's how I built ours. The big improvement is that the bottom pendulum can be locked in place. This turns the chaotic double pendulum into a non-chaotic physical pendulum.
I'm going to be lazy and skip writing a big long introduction or explanation for this. The Wikipedia article on chaos thoery is pretty good and explains how chaotic systems are sensitive to initial conditions. The mathematics are too complex to accurately reproduce here, but the links below can show them correctly:
http://en.wikipedia.org/wiki/Double_pendulum
http://en.wikipedia.org/wiki/Pendulum_%28mathematics%29
http://hyperphysics.phy-astr.gsu.edu/hbase/pendp.html
http://www.myphysicslab.com/dbl_pendulum.html (simulation)
http://www.chaoticpendulums.com/chaos-theory-a9.html (simple explanation of chaos theory)
Here's a neat version made from two square plates:
http://www.physics.usyd.edu.au/~wheat/sdpend/
You can buy a double pendulum from chaoticpendulums.com, but it's more fun to build your own. Look at the pictures, look at the CAD files, watch the video, and then go make one.
Support Amazon.com for sponsoring this science fair contest, buy ball bearings online.
Safety
Standard shop and power tool warnings apply, but I have to provide a warning specific to the double pendulum. The bottom pendulum can get moving very fast and because it's chaotic, it's unpredictable. If your hand or face is in the wrong place and the wrong time, you can get seriously hurt. The best thing to do is to set it in motion and then stay out of the plane of rotation.
I fixed the video! Sorry about that. It's viewable in step 10.
I'm going to be lazy and skip writing a big long introduction or explanation for this. The Wikipedia article on chaos thoery is pretty good and explains how chaotic systems are sensitive to initial conditions. The mathematics are too complex to accurately reproduce here, but the links below can show them correctly:
http://en.wikipedia.org/wiki/Double_pendulum
http://en.wikipedia.org/wiki/Pendulum_%28mathematics%29
http://hyperphysics.phy-astr.gsu.edu/hbase/pendp.html
http://www.myphysicslab.com/dbl_pendulum.html (simulation)
http://www.chaoticpendulums.com/chaos-theory-a9.html (simple explanation of chaos theory)
Here's a neat version made from two square plates:
http://www.physics.usyd.edu.au/~wheat/sdpend/
You can buy a double pendulum from chaoticpendulums.com, but it's more fun to build your own. Look at the pictures, look at the CAD files, watch the video, and then go make one.
Support Amazon.com for sponsoring this science fair contest, buy ball bearings online.
Safety
Standard shop and power tool warnings apply, but I have to provide a warning specific to the double pendulum. The bottom pendulum can get moving very fast and because it's chaotic, it's unpredictable. If your hand or face is in the wrong place and the wrong time, you can get seriously hurt. The best thing to do is to set it in motion and then stay out of the plane of rotation.
I fixed the video! Sorry about that. It's viewable in step 10.
STEP 1: Top Pendulum - Front
This aluminum bar is half of the top pendulum. Another similar bar forms the second half. The ball bearings are 3/8" ID x 7/8" OD x 7/32" wide (McMaster-Carr P/N 60355K14) and are held in place by a #8-32 set screw. There are four bottom tapped #8-32 holes for the screws that hold the top pendulum together. There's one more #8-32 through hole for the bottom pendulum pivot. Finally, there's a 0.311" hole for the socket head shoulder bolt.
STEP 2: Top Pendulum - Back
STEP 3: Spacing Block
STEP 4: Top Pendulum Assembly
STEP 5: Bottom Pendulum
STEP 6: Bottom Pendulum Pivot
This is the pivot for the bottom pendulum. The length is the same as the width of the top pendulum spacing block.
STEP 7: Bottom Pendulum Assembly
STEP 8: Complete Double Pendulum Assembly
STEP 9: CAD Files
Download an AutoCAD .dwg and/or an Alibre Design Xpress assmebly.
135 Comments
mithunashok 15 years ago
Irritable_Badger 4 years ago
You can certainly increase the accuracy of predictions by decreasing the number of variables (as in my example above) but there is always a level of unpredictability present. Which is what it’s all about :)
surrealista1 9 years ago
as i know it probably can be described by a fractal
vmars316 6 years ago
Hello & Thanks,
I would like to make one of these but on a much smaller scale .
Where could i find miniture ball bearings?
Thanks
btw: 'chaoticpendulums.com' is a dangerous link.
Yikes those 'McMaster-Carr P/N 60355K14' are expensive.
ProphetMargin 9 years ago
I'm thinking you add an LED to the bottom hole and turn the lights out!
armagdn03 10 years ago
Sir__Walter 11 years ago
DieCastoms 15 years ago
sueman2 14 years ago
since it is moving so fast the small amount of mass doesn't matter. Like it would have to be 1000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000
0000000000000000000000000000000000
00000000000000000000000000000000000000000N
i do like your fact and will share it with my friends. I simply ask for your view. Do you happen to have a blog or video channel of some sort i can subscribe to, so to hear more of your views?
ubr.bzkr 13 years ago
Because of this, the small amount of mass would matter as the speed of light is 299,792,458 m / s. now using the formula:
ke (kinetic energy) = (1/2)M*v^2
where M = mass and V = velocity. A tiny particle such as an alpha particle which weighs about 6.64424 × 10^-27 kg (and is much larger than a photon) moving near the speed of light would have kinetic energy equal to only about
2.9858*10^-10 Joules. which is equivalent to around 3*10^-9 newton meters.
you cant even feel it.
mickgoth 13 years ago
betwys1 13 years ago
DieCastoms 13 years ago
In the case of E=MC^2, Energy = Mass times the Constant (speed of light) squared. This refers to the amount of energy that can be released by a given amount of mass if ALL energy could be released, 100% efficiently.
In your post you mention E=hf and you also mention e.m waves. Can you expand on those two, please?
I appreciate that you took the time to post this! Thank you.
Mike from DieCastoms.
itsthatsguy 14 years ago
BigCountry 14 years ago
Sometimes I think the weeds in mu garden grow faster than light...
itsthatsguy 14 years ago
Ben5504 15 years ago
You're absolutely right: for a long time, people had difficulty combining the "massless-ness" of light with the fact that light can be deflected by massive objects (which is a proven phenomenon). I'll see what I can do to explain.
Imagine a large, squishy mattress. When you place a large object on that mattress, like a bowling ball, it sinks into the mattress and creates a dip all around it. If you were then to place a marble somewhere nearby on the mattress, it would roll toward the bowling ball because of the dip.
This is a really good analogy for the way that space behaves in the presence of an object with mass. Around any large object, like the sun, space is distorted, and nearby objects, like the planets, feel the effect of that distortion (they tend to "roll toward" the sun). Unfortunately, it's much harder to visualize in three dimensions.
Okay, so let's look at how it affects light. Going back to the bowling ball on the mattress: what would happen if you tried to roll a marble past the bowling ball? It would hit the dip in the mattress and curve toward the bowling ball. If you rolled it fast enough, or if the dip wasn't very deep, it would curve a little bit but still be able to make it back out of the dip, but now traveling in a slightly different direction. This is what happens to light going around massive objects in space, like a galaxy. This phenomenon is called "gravitational lensing", because the galaxy redirects light, just like a lens can do.
With black holes, imagine the dip in the mattress is very, very deep, so deep that no matter how fast you roll the marble, in can't make it back up the other side, but instead spirals around the dip until it reaches the center. This is what happens with black holes because they are so massive compared to anything else.
So, long discussion, but in summary: yes, gravity does affect the trajectory of light, but not because light has mass. Rather, mass changes the shape of the space around it, and light follows that shape, and is deflected.
nightscape_98 14 years ago
pacifcace 14 years ago
itsthatsguy 14 years ago