But for the people walking, this looks like a model railroad setup.
Tilt-Shift Trains Switzerland
Category Archives: Cool stuff
No Grace Under Pressure
Atmospheric pressure is about 10 N/cm^2, but there are a whole lot of square centimeters on that tanker — the more familiar unit is N/m^2 (Pascals), where 1 atmosphere is 101325 Pa (or possibly even more familiar 14.7 psi).
Various sites showing this have claims about this happening after the tanker had been heated (from steam cleaning), and all the valves shut while it was still hot. One claims frozen (perhaps they mean liquid?) nitrogen being added. Plausible? Heating the tanker to 373K and then letting it cool to ambient should drop the pressure by 0.20 atmospheres. A tanker that’s 2 meters in radius and 10 m long has a surface area of 125.6 m^2, for a total force of 12.7 MegaNewtons. 20% of that is a lot. I don’t think the liquid nitrogen is strictly necessary, but would add to the effect.
The heat of vaporization of liquid nitrogen is 5.56 kJ/mol and its specific heat capacity of the gas is 29 J/mol-K. The volume of 125.6 m^3 means 5600 moles of an ideal gas, requiring 160 kJ/K to cool it down. Each liter of liquid nitrogen (29 moles) takes about 160 kJ to boil off, and then another .84 kJ per degree as the gas heats up from 77K. So ten liters of liquid nitrogen dumped into it will cool it about 20-25 degrees, depending on the starting point of the tanker. So that won’t hurt, but what’s probably more important is that the tanker was built to withstand some pressure difference and we see the catastrophic failure when its critical pressure difference is exceeded. Unlike the kind of test you can easily do with a can where you boil some water inside, seal it and watch it crumple as it cools, because it wasn’t designed to withstand and significant pressure difference.
Fractal, Inc
Oh. I mean fractal ink
A Polynesian Vacation
You're a Pillar
Typically seen in polar regions, the vertical columns of light have been appearing along with frigid temperatures at lower latitudes this winter.
Light pillars appear when artificial light or natural light bounces off the facets of flat ice crystals wafting relatively close to the ground.
Waterfalls
Top Ten Waterfalls in the U.S.
Of these, I’ve seen Multnomah Falls and Niagra Falls
Peek-a-Boo
Litracon is a combination of optical fibers and concrete. A wall made of Litracon has the strength of traditional concrete but thanks to an embedded array of optical glass fibers, which lets in the view of the outside world, such as the silhouette of trees, or passersby, that are displayed inside the building.
The glass fibers allow light to travel by points between the two sides of the blocks. Due to their parallel placement, the light-information on the brighter side of such a wall seems unchanged on the darker side. Also there is no change in the color of the light.
Peer Pressure
C’mon … we’ve all done it!
Just about anyone with access to liquid nitrogen has dunked things and smashed them.
The Photon Push-Me Pull-You Update
Back in June I wrote up a post an the Abraham-Minkowski controversy, which concerns the momentum of a photon when it’s in a medium.
Depending on the assumptions one makes, one can show that the momentum increases or decreases inside the medium, and obviously both solutions can’t be correct. But for a long time it was unclear which assumptions were faulty, because it was such a delicate experiment to do.
I just ran across a post at Everyday Scientist, and the paper (based on the ArXiv preprint I cite in the link) was published last month … and there’s a video.
The researchers performed a second experiment with a longer fiber and continuous–rather than pulsed–laser light and found similar results. The tip of the hanging fiber moved sideways like a pendulum by about 30 microns, which agreed with the tiny force (less than a billionth of a Newton) that they predicted. The team also verified that thermal effects, such as heat expansion, would be too small to influence the fiber’s movement.
Winter Wonderland
It’s very cold tonight, so we played with bubbles. If you blow them upwards enough they have time to freeze on the way down.
Damn. I wish I’d thought to do this when the temperature dropped to ~ 0ºF while I was home.