Static electricity was mentioned:
As long as we made sure none of the objects we were experimenting with were magnetic or electrically charged (easily arranged, assuming they are conductive, simply by bringing them into contact so all excess charges equilibrate)
But you're right, I would consider it much more convincing if the experiment were set up so that everything was connected by conductors.
The other thing is that in the video, the bar is initially nearly perpendicular to the external masses. In this configuration, not only are the bar's masses far from the external masses, but the torques are almost balanced. I don't see any mention of this.
The video appears to indicate that it takes 3 minutes for the bar to rotate around and make contact with the external masses. I wrote a quick sketch of a program to figure out how long it should take, and I got over 3 hours. Specifically, I used the favorable assumptions that the foam bar is massless, that the setup is frictionless, and I calculated what would happen with one external mass of 740g and an initial separation of 17 cm, until the separation decreased to 2 cm. The initial separation isn't clearly stated anywhere - there is a vague mention of "at the 14 cm distance when the beam is at the midpoint between the masses". The bar diameter is clearly given as 30 cm, and I believe I'm getting the basic trig right when I calculate that an angle of 70 degrees would result in a 17 cm separation. Finally, I'm considering only one bar mass and one external mass (utterly neglecting the near-symmetrical torque is highly favorable, producing a time estimate that will be shorter than reality) and because I didn't want to write the trig, I'm working with linear movement in free space, instead of the actual rotation. (I used Boost.Units to ensure that I didn't screw up my math even further than these simplifications.)
I agree - something is extremely fishy here.
Showing my work:
C:\Temp>type meow.cpp
#include <iostream>
#include <ostream>
#include <boost/units/io.hpp>
#include <boost/units/pow.hpp>
#include <boost/units/quantity.hpp>
#include <boost/units/systems/si.hpp>
#include <boost/units/systems/si/prefixes.hpp>
#include <boost/units/systems/si/codata/universal_constants.hpp>
using namespace std;
using namespace boost::units;
using namespace boost::units::si;
using boost::units::si::constants::codata::G;
typedef quantity<boost::units::si::time> quantit
I have an 8-year-old sister who is very interested in science. The school she attends (in rural Indiana) takes the mantra of "teaching to the test" to a whole new level; my sister has already come home from school many days crying and stressed over fear that she won't pass her state's proficiency tests (which are 5+ months away). They are underfunded and the science curriculum is what most of the (overtly religious) teachers are undertrained in, and so science is essentially not addressed. My sister has about an order of magnitude more homework on cursive writing than on anything related to science.
I want to purchase a gift for her for the holidays this year (the occasion doesn't matter, but it's a time when I'll actually be home so I can give her the gift and play with her / explain how to use it / hopefully help her start thinking about some things). I'm willing to consider age-appropriate ideas across several price ranges, but I want to think of something that will deliver a lot of utility: i.e. it should be compelling enough that an 8-year-old will actually like using it and there should be at least some evidence that she will benefit from it.
I've considered things like the EDUbuntu computers that come with lots of educational software, but actually buying one seems to be not straightforward. Is the best thing to buy a cheap netbook at then install EDUbuntu myself? Is a netbook too much for an 8-year-old? I'm mostly focused on things that will help her be proficient with computers and potentially help her develop a more sophisticated interest in them as she grows up. The Lego Mindstorm robotics stuff also crossed my mind.
Does anyone have experience with this / know of resources for making a good investment? Or am I way over-thinking this and just some regular Legos or art supplies are going to do essentially just as much good?
Added 02/25/2012
Much of the advice was very helpful. I ultimately found out that my young sister was interested in "mixing chemicals together because it looked cool." An item that I found which looked like a good way to bridge the gap between her more girly interests and her interest in chemistry was Perfume Science from Thames and Kosmos. I also purchased a variety kit from Snap Circuits. She loved both items and we spent a good bit of time playing with them during my trip home to see my family. We made several different kinds of perfume and also did some activities that helped explain how different extracts have been acquired throughout human history for their smells. Ultimately, my sister made a science fair project (something which surprised my parents a lot) based around one of the activities in the perfume science booklet, and she won second place.
I was very happy with both my decision to ask this question on LessWrong (despite the title of the post, which seems to seethingly annoy many LWers) and my purchase decisions. I used the website Fat Brain Toys to purchase the items and everything arrived without a problem. That site seemed to also have a reasonably good selection for more educationally oriented toys across several ages, and with useful customer reviews.