Mentos and cola in UltraSlo motion @7000FPS. Seven-frikkin’-thousand!
Category Archives: Physics
That Giant Sucking Sound
Is coming from sciencegeekgirl’s Hands on Science Sunday: Feeling pressured?
All you need is a big trash bag and an industrial strength vacuum cleaner, and a willing victim (er, “faithful subject of science.”) The victim (aka “subject) gets inside the bag, and once you suck all the air out of the bag with the vacuum cleaner, they’ll feel an intense pressure. SAFETY FIRST! Read this PDF writeup of the activity (from the Exploratorium’s Eric Muller) for all the ins-and-outs and safety factors in doing this with your kids. (Words to the wise — don’t put your head inside the bag!) It’s stunning — try it if you can.
Getting the Drop on … a Drop
Doing more of the standards. A drop of blue food coloring falling into a glass of water, at 1000 fps.
Going UP (Very Precisely)
Via gg I see that there is a new vertex on the bologohedron, The X-Change Files
The X-Change Files explores the intersections of science and entertainment, regularly taking a look at the ways in which science is portrayed in film and television. Given that science is often the basis for provocative and compelling storylines, we’ll also highlight the latest scientific discoveries. Perhaps most importantly, we’ll examine the ways in which public opinion is shaped and behavior is changed by what people see on their television sets and in the movie theaters.
And it comes with an impressive list of contributors.
So I will welcome them, followed by picking some nits in the analysis of Pixar’s new movie, UP which they point out in the post Going UP! . They link to a WIRED story about the movie, which estimates the weight of the house needing to be lifted by helium-filled balloons as being 100,000 lbs.
One more simple calculation — 100,000 pounds divided by 0.067 pounds per cubic foot — and you’ve got that it would take 1,492,537 cubic feet of helium to lift the house.
Ignoring that we’re working in English units, which scientists don’t really do very much, the big thing that pops out to the budding, fully-bloomed, or dying scientist is the misuse of significant digits. Do we really believe the estimate of the house’s weight is exact? No, it’s probably good to 2 digits, at best — the house could easily weigh several thousand pounds more or less than the estimated value. So the answer is that it takes 1,500,000 cubic feet of Helium to fill the balloons. You can’t specify it any better than that. The same mistake propagates through the calculation of the number of balloons.
Now, let’s assume you’ve got a bunch of spherical balloons three feet in diameter. They’ve got a volume in 14.1 cubic feet, so you’d need 105,854 of them filled with helium to lift the house.
Same deal. Not only is the volume not precise, but the balloon diameter is an estimate as well. There is no way to make an exact count to the last balloon you would need. So while Pixar got the science right in estimating the number of balloons needed, and it’s great to be enthusiastic about that, it’s also important not to drop the ball when discussing how well they did.
(The most consistently egregious abuse of significant digits in the media (though not necessarily entertainment media) is when there is a conversion from one unit system to another. An approximation of “30 meters high” is converted using 3.28 feet per meter, so that this rough estimation is then given as 98.4 feet high, instead of 100 feet high, as it should be given.)
And, getting on to some more physics, I see that zapperz has taken a pass at analyzing the physics in this movie as well. The Physics in Disney/Pixar’s “Up” takes another look at the buoyancy issue, and points to what might be a little problem among the rest of the decent physics treatment of the buoyancy. Rhett also looks at this issue, as well as some other analysis.
(Here Comes the Sun) (-1)
Why is the Earth moving away from the sun?
Short answer: tidal friction, the same reason the moon is receding from us.
But there’s a “what the?” in the story.
[T]he sun-Earth distance has been pegged with remarkable accuracy. The current value stands at 149,597,870.696 kilometres.
Having such a precise yardstick allowed Russian dynamicists Gregoriy A. Krasinsky and Victor A. Brumberg to calculate, in 2004, that the sun and Earth are gradually moving apart. It’s not much – just 15 cm per year – but since that’s 100 times greater than the measurement error, something must really be pushing Earth outward.
No error is reported, but presumably the error is in the last digit of the value, 0.001 km. One one-thousandth of a kilometer is a meter. 15 cm is smaller than that. If the error is as was reported, it should be a few millimeters. If that’s the error, why isn’t the distance known and reported to that level?
Smashing Pumpkins. Or Something.
It’s not the squirrel smasher, but it’s close. Abstruse Goose does the Toad Totaler
But … stationary target? It would be much more efficient to have the lab frame also be the center-of-mass frame (i.e. counter-propagating frogs)
Wheel … of … Falkirk!
These caissons always weigh the same whether or not they are carrying their combined capacity of 600 tonnes (590 LT; 660 ST) of floating canal barges as, according to Archimedes’ principle, floating objects displace their own weight in water, so when the boat enters, the amount of water leaving the caisson weighs exactly the same as the boat. This keeps the wheel balanced and so, despite its enormous mass, it rotates through 180° in five and a half minutes while using very little power.
Short time-lapse video of the wheel in action
Gelett Burgess's Stove
I never saw a purple cow;
I never hope to see one;
but I can tell you anyhow;
I’d rather see than be one!
I modified a webcam to allow IR photography, but didn’t think to take a picture like the one Matt has displayed, in which a stove’s heating element glows purple (when viewed with his camera), just as it starts becoming incandescent. I have a gas stove.
There are a Bazillion of Them
We think of fundamental particles as being very small, but “relic” neutrinos left over from the big bang could be big. Really big. According to the 22 May Physical Review Letters, the quantum wave describing one could be billions of light-years across, a good fraction of the observable universe. Such a large wave raises questions about how a quantum particle interacts with gravity at the scale of galaxies and galaxy clusters–questions that remain unresolved.
Someone Other Than Apple Launches an iPhone
The iPhone Rocket: The Story (and Data) Of How An iPhone Hit 1300ft
Powered by a Aerotech G80-13 engine, the rocket reached some 440m (1312 feet) in altitude (or 200m in relative altitude) before heading back to the ground. Michael developed an iPhone application that constantly polled the iPhone’s GPS and accelerometers, logging them to a file, as well as sending GPS data over the Web so that the unit could be easily located if it became lost.