Pavlov's Stepson
Kiss someone nice, or lick a rock, or both
Take a look at some gorgeous snowflakes, and find out the reason they’re six-sided
The beautiful hexagonal crystals that water forms when it freezes in the clouds have been much celebrated by those with electron microscope, and without a driveway that they need to shovel clear. Because within the giant globs of freezing water that the world playfully throws at us, there are intricate hexagonal patterns.
Most of the time we’re too big to see those patterns and too cold to care about them, but when we get inside, warm our feet, and maybe get our hand around a hot mug of something, we contemplate. There are billions of swirling molecules of water up there in the clouds. Why do they always form into hexagonal structures? And if there is some preference, on the atomic level, for hexagonal structures, why are each of those tiny structures so different from one another?
The answer to the hexagonal shape of the snowflake lies in the shape of the water molecule itself. A water molecule is two electron-deprived hydrogen atoms clinging to a central, also-electron-deprived oxygen atom. By pooling their outermost electrons they get a stable formation. That stable formation requires the hydrogen atoms to be pinned at specific points to the oxygen atom. They can’t simply hang out at either end of the oxygen atom, 180 degrees apart. They hug relatively close to each other, only 104.5 degrees apart, giving the overall molecule a V shape. The oxygen tugs the electrons close to itself, leaving the angle of the V with a slightly negative charge while the hydrogen atoms, with the protons in their nuclei exposed to god and everyone, are slightly positive. Positive charges are attracted to negative ones, so the hydrogen end of one V will be attracted to the oxygen apex of another. Even when it’s splashing around in a bowl, or whirling through a cloud, water is structured.
When it gets cold, some real organization happens. Water doesn’t just spontaneously freeze. It freezes via a process called nucleation. One water molecule shifts its structure slightly and freezes solid with another, and as that structure moves through a whirling cloud of water, more water molecules hop on board, until the whole structure gets too heavy to fly and drops down. This process is not a free-for-all. A frozen water molecule will still repel, and be repelled by, any other molecule that approaches it from the wrong angle. Get a group of bar magnets together and jumble them around, and they’ll ‘arrange’ themselves with north and south polls of different magnets linked. Water molecules do the same, just with a V shape. The patterns grow from that shape, and they arrange themselves into hexagons.
And yet, different snowflakes look radically different from each other. Nucleation doesn’t generally start on its own. The ‘seeds’ of nucleation are dust molecules whirling with the water through the atmosphere. They’re one of the reasons why we see differently-shaped snowflakes whenever we care to look. Different patterns appear depending on the size and density of dust. The snowflakes also depend on temperature, air pressure, wind speed, and a thousand other factors. Scientists are still studying the exact mechanism of the different shapes. There are so many variables involved. In the meantime, they’re still pretty.
Top Image: US Department of Agriculture.
A pinhole camera created from an egg. Pinhole cameras are often used in introductory physics courses to illustrate the principles of optics. The following was taken from a lab exercise at Rice Univerity:
A pinhole camera consists of a darkened box or room with a small hole at one end. Because light travels in straight lines, the hole permits rays from each point of an object to fall only within a small circle on the opposite wall, effectively forming an image. As the pinhole is made smaller the image will become more distinct until the hole is so small that diffraction becomes important.
Although pinhole cameras were probably known to the ancient Greeks, they are still used in preference to lens systems in some situations. Pinholes are obviously useful for imaging x- rays or particle streams, where no lens materials are available, but even for light they offer complete freedom from linear distortion, virtually infinite depth of focus and a very wide angular field. Modest resolution and a very dim image are the disadvantages. Overall, pinhole cameras are worth study because they are useful and also because they illustrate some interesting physics.
Sunday Sun
Copyright: Behyar Bakhshandeh
Beautiful Bacteria
The images above are some examples of rotex fractal growth found in colonies of Bacillus subtilis. The varying branching patterns are caused by changes in the environmental conditions of the bacteria as they grow.
Thor’s Helmet: Skywatcher Sees Glowing Gas Space Bubble
Astrophotographer Bill Snyder captured this spectacular view of massive cosmic cloud commonly known as Thor’s Helmet.
Snyder took the image in June 2011 from his home observatory in Connellsville, Penn., and recently provided. Multiple exposures are made to collect enough light for an image that would otherwise not be evident to the eye.
The emission nebula lies in Canis Major, about 15,000 light-years away from Earth. A light-year is the distance light travels in one year, or about 6 trillion miles (10 trillion kilometers).
Fierce stellar winds and intense radiation from a nearby star created the bubble-like shape of the nebula. This star, known as a Wolf-Rayet, is thought to be in a pre-supernova stage and likely has a mass 10 to 20 times that of the sun. The winds from this star create the shell of the glowing nebula. It has a blue-green hue due to the oxygen atoms in the gas.
Spherified balls of melon and ham
Photograph from: Cooking Science: Condensed Matter
Microchip delivers drug; can it replace shots?
Instead of constantly releasing small amounts of drug, the microchip releases medication on command all at once, much like an injection.
Its sad because it’s true.
A Tornado On The Sun
NASA’s Solar Dynamics Observatory captured this video of swirling plasma on the surface of the sun. It’s a tornado perhaps the size of the Earth itself, spinning at speeds a thousand times greater than Earth’s strongest storms.
(via NPR)
Animation of MarkIII(k), one of the molecular machines designed by K. Erik Drexler and Nanorex, Inc., categorized as “nanoscale planetary gear.”
Crab Nebula’s Pulsar May Be Fast Particle Accelerator
Image: Crab Nebula gets the “Blues” by Danny Lacrue via HubbleSite
The Crab Nebula (also designated M1 or NGC 1952) is visible through small telescopes, which has allowed astronomers to observe its growth and evolution since the supernovae that created it became visible in 1054 CE. A pulsar was found in the center of the Crab in 1968.
This rapidly rotating neutron star is the core of the star that went supernova to make the nebula. In the intervening decades, x-ray, gamma ray, and radio observations have mapped the region of the nebula closest to the pulsar. During that mapping, it became apparent that the Crab pulsar is one of the brightest sources of gamma rays observable from Earth.
Despite all of those observations, we still don’t fully understand the Crab’s precise gamma ray spectrum, particularly recently observed pulses of intense gamma radiation seen by the Fermi Gamma-ray Space Telescope. Existing models certainly do well at describing much of the complex interplay between the intense magnetic fields of the pulsar and the winds of charged particles flowing outward. But no single scheme seems sufficient to cover all the observed phenomena.
A potentially promising new model, proposed by F. A. Aharonian, S. V. Bogovalov, and D. Khangulyan, may fill in some of these blanks. It proposes that areas near the pulsar are acting as rapid particle accelerators, but don’t boost electrons and heavier particles to the same extent.
Pulsars are exceedingly small despite their high mass: According to typical neutron star models, the Crab pulsar is approximately 30 kilometers in diameter, but contains nearly double the mass of our Sun. The intense gravitational influence and rapid rotation of pulsars place them firmly in the realm of relativity, while intense magnetic fields carry the enormous amounts of energy we typically encounter in particle accelerators.
In the region immediately surrounding the Crab pulsar, there is enough energy to produce pairs of electrons and positrons, which flow outward into the surrounding gas. This total flow is the pulsar wind, a plasma (an electrically neutral substance consisting of separate positive and negative charges) that moves very close to the speed of light.
Sundew plants are carnivorous, consuming insects by capturing them with small adhesive balls on the ends of their tentacles. The sundew’s adhesive has remarkable elasticity, stretching to 1 million times its normal size (most rubber bands can only stretch to six times their original size). Such elasticity would make the adhesive dew secreted from the plant an effective choice for coating replacement body parts, regenerating dying tissues, healing wounds and improving synthetic adhesives. It is also economical—it’s so sticky and elastic that less than a microliter (smaller than the period at the end of a sentence) would cover 25 millimeters squared (or the size of George Washington’s face on a dollar bill).
Olmid Gozar’s portraits of insects remind me of yearbook photos. I can’t help assigning personalities to these creatures when they appear to be looking directly at me, and especially not when the guy on the top is giving me his “Blue Steel”.
