I tried doing a similar demo, but used a beaker and it’s a lot harder to place the objects in so that they will float. Which is why I don’t have a video like this.
Category Archives: Physics
You Get My Motor Running
Those Orphan Neutrinos
I’m Shocked! Shocked! to Find There Are Neutrinos Going On Here
[E]xperimental physics is (and has always been) very, very hard to do, involving an effort to push the limits of precision beyond any current standard. Because the effects sought are at the limits of our capacity to detect them (necessarily; if it were easy, we’d have seen whatever it was already) there is an enormous amount of subtle knowledge that goes into constructing the framework of each experiment. The machines don’t just have to work; you have to understand in detail how quantum mechanics and relativity and all the increasingly subtle applications of the broad ideas play out at the speeds and energies and distances involved. Understanding what’s actually happening at the subtle edges of experiments — even seemingly simply ones — turns out to be very difficult to do.
I Would Not Mark "D" as Wrong
The Fonzie Workout
They continued to study Cao for the next six weeks. If they applied cooling between sets, Cao’s performance held steady in set after set. Without cooling, it decayed. “It was as if he had no fatigue,” Heller recalls. “We saw incredible gains over the next six weeks. He tripled his capacity to 620 pull-ups.” Preventing muscle exhaustion allowed Cao to train harder, leading to rapid gains in muscle strength. Heller and Grahn theorize that more blood, and thus, oxygen, is available to the muscles when the body doesn’t have to route extra blood to the radiators for cooling.
Do or Diode
Diode lasers may vie with LEDs for lighting supremacy
It’s not just BMW with laser headlights. But the higher efficiency is tempting.
Little research had been done on diode lasers for lighting because of a widespread assumption that human eyes would find laser-based white light unpleasant. It would comprise four extremely narrow-band wavelengths—blue, red, green, and yellow—and would be very different from sunlight, for example, which blends a wide spectrum of wavelengths with no gaps in between. Diode laser light is also ten times narrower than that emitted by LEDs
Occupy the Universe
Quasicrystal Animation
Quasicrystals as sums of waves in the plane
This is so cool, and artsy as well; like a very complicated moving moiré pattern (which is basically what it is, as far as I can tell). You can see lines emerging, similar to the effect of driving past an orchard with evenly-spaced trees, and glimpsing the far side when you hit a particular “order” of the structure, but there’s so much additional structure in the animation.
I Really Don't Know Clouds At All
Amazing video of a bizarre, twisting, dancing cloud
The outer surface of ice crystals can hold a static electric charge, similar to what happens when you rub a glass rod with a cloth, or rub a balloon on your hair and stick it to the wall. When placed in an electric field, the charges feel a force on them, and align themselves along the field. So all the ice crystals above that cloud top are aligned one way in the field. Then the field snaps (maybe due to lightning releasing the energy) and then reforms. The ice crystals change their orientation suddenly when that happens.
Stay! Staaaay!
I’ve been growing salt crystals. Unlike a pet, salt crystals won’t tear up the furniture, do their business on the carpet or need to be walked in the rain. Really I was testing to see if I could do this as a time-lapse project and wanted to test how long it would take. And it has fulfilled Hofstadter’s law: it always takes longer than you expect, even when you take into account Hofstadter’s law.
I took the standard approach of heating some water and dissolving a bunch of (uniodized) salt in it, letting it cool and pouring it into a beaker. And I waited. And waited. Finally, after a few weeks:
One thing I should have anticipated is how long it takes. There was some salt left in the pot when I poured the solution into the beaker, so I thought the crystallizing would begin quickly, but it didn’t. Plus, the evaporation was slow. I knew that boiling point elevation and freezing point depression are colligative properties (they depend on the number of dissolved atoms) so I reasoned that evaporation rate should be as well. And it is — there is Raoult’s law
The vapour pressure of an ideal solution is dependent on the vapour pressure of each chemical component and the mole fraction of the component present in the solution.
The vapor pressure of salt is very low, so as its concentration rises the total vapor pressure of the solution drops, and so does the evaporation rate. Rather than evaporating fully, one would expect it to reach an equilibrium with the atmosphere which would depend on the humidity. In fact, if the salt concentration were high enough, one might expect it to dehumidify the air, which is precisely what some people do. Salt concentrations are used in dehumidifiers — you expose the solution to the air and let is “grab” some water, then heat it up (often solar, for a completely passive system) to let the excess water evaporate, and cool it again in a cycle. Or you can have a solution with some solute left in the container, and as you “grab” the water, you dissolve more of the salt, so it can continue doing its job as long as there is more salt that can dissolve.
Another unexpected event in all of this is that I was getting salt crystallizing on the surface of the water. A small “raft” would float there until it grew massive enough that it would sink (or someone poked it). I had thought the crystallization would just build on any crystal that started up, but there are lots of small cubes rather than just a few large ones. Still, the biggest cubes are perhaps 10-20x larger on a side than the original grains.