(Of electromagnetic radiation) having a wavelength just greater than that of the red end of the visible light spectrum. Infrared radiation has a wavelength from about 800 nm to 1 mm, and is emitted particularly by heated objects.
PHOTO: Wolf in Infrared Light
by Wonder Science
Photo credit: USGS
March 12, 2019 by Wonder Science
Photo Credit: CSIRO
READ: Scallop Vision
by Wonder Science
Photo credit: Prof. Dan-E. Nilsson, Lund Vision Group, Dept. of Biology, University of Lund
In Sandro Botticelli’s iconic painting, “The Birth of Venus,” the goddess of beauty is depicted standing inside a giant scallop shell. In nature, inside its radiating ridged shell, the scallop resembles an undifferentiated round blob. But the beloved bivalve mollusk is not as simple as meets the eye. The scallop possesses an unusual form of biological optics. A single scallop can have up to 200 eyes!
A scallop’s eyes grow out of its fleshy mantle, in the undulant folds of its upper and lower shells. Each eye perches on top of a thin tentacle that can extend it forward and retract it back. The eyes often possess a brilliant blue hue, and they not only permit the mollusk to perceive light and motion, but to form actual images.
Scallop eyes use a concave mirror to focus light rather than a lens. The mirror is made from twenty to thirty layers of guanine crystals. Guanine happens to be one of the four* chemical building blocks of DNA and RNA — it is the “G” in G,C,A,T — guanine, cytosine, adenine and thymine. Crystals of guanine are rhombic, each having four sides of equal length like a semi-squashed square. The rhombic guanine crystals grow in thin transparent layers with a high index of refraction, allowing some light to pass through and reflect. In the scallop eye, the crystal layers are themselves arrayed in a square mosaic. The remarkable arrangement of the guanine crystals reduces optical aberrations. The scallop can even adjust the layered mirror structure to best reflect wavelengths of light.
The scallop’s visual system is even more complex because it has a double retina. One retina images what’s in front of the scallop, and the other retina images objects and motion in its peripheral field of view.
It has been noted that the concave focusing mirror in the scallop eye bears a striking resemblance to the segmented mirrors of reflecting telescopes. This similarity provides biomimetic inspiration for the further development of compact, wide-field imaging devices.
The Lepidoptera are beloved among insects. Most of us are familiar with their fluttering beauty, seasonal migrations, and amazing ability to transform from caterpillars. But here are some surprising facts about butterflies which you may not have heard:
1. Butterfly metamorphosis is grisly. To become a butterfly, a caterpillar first digests its own body inside its cocoon. It dissolves into unrecognizable goop that slowly reconstitutes into a butterfly with a wholly different body plan.
2. Butterflies taste with their feet. Sensors on the back of their legs determine the quality of sugar in a flower. Butterfly feet can also taste leaves. Before depositing eggs, a female butterfly knows whether a leaf will be edible to her offspring. Her sense of taste ensures a ready first meal when her eggs hatch into baby caterpillars.
3. Some species of butterfly possess a sense of hearing. The Zebra Longwing, for example, is equipped with microscopic hearing organs that can detect sound. Its two eardrums are located at the base of the underside of its wings.
4. The scales covering the wings of a butterfly are not only for display, aerodynamics, and protection from the elements. Butterfly wing scales also serve as defense. They detach easily from the wing to help the insect escape from tight spots, for instance from an attacker or a spider’s web. This is why it’s important not to touch a butterfly — if it loses scales it could get cold and die.
5. Butterflies have excellent posture. To regulate flight, the insects actually use their bodies as much as their wings. A butterfly controls its abdomen much like the rudder of a sailboat. And its wings are like sails. Filming butterfly flight in slow motion and with thermal imaging, researchers at the National Taiwan University have shown that butterfly body posture is integral to their flight.
READ: Cyanobacteria & Oxygen
by Wonder Science
Cyanobacteria originated pivotal evolutionary developments which transformed our planet. These microscopic bacteria live alone or in colonies, in any environment that has moisture. Over 2 billion years ago, cyanobacteria triggered the Great Oxygenation Event. Every breath we take, we owe to cyanobacteria. It is thanks to them that complex life forms evolved in the first place.
When the Great Oxygenation Event occurred 2.5 billion years ago, the Earth was half its current age, populated by various single-celled organisms subsisting in an atmosphere composed of carbon dioxide, water vapor, ammonia and methane.
Approximately 100 million years earlier, cyanobacteria had evolved the ability to make their own food using sunlight, carbon dioxide, and water — photosynthesis. They were the first organisms to photosynthesize.
Of course, oxygen gas is a waste product of photosynthesis. Over millions of years of cyanobacteria performing photosynthesis, small concentrations of oxygen accumulated in the environments where cyanobacteria lived.
Fast-forward 100 million years, and the Earth’s atmosphere was full of oxygen. Multiple theories attempt to explain the 100 million year lag between the time cyanobacteria became photosynthetic to when the Great Oxygenation Event occurred, 2.35 billion years ago. A favored theory posits that a mere 150 million years prior to Great Oxygenation Event, cyanobacteria changed in a way that suddenly made them more successful, enabling them to release enough oxygen to transform the atmosphere of the planet.
So what happened? Through taxonomic analysis, scientist B.E. Schirrmeister et al have shown that cyanobacteria evolved multicellularity 2.5 billion years ago. Therefore, cyanobacteria were not only the first life-forms to photosynthesize, they were also the first to achieve multicellularity. They formed chains of bacteria with one differentiated cell at the head. As primitive as it was, cyanobacteria’s multicellularity gave them profound new advantages over single-celled species.
Most cyanobacteria lived in layered microbial mats called stromatolites, rounded lumps found in tide pools and underwater, home to many species of microbe. Once cyanobacteria became multicellular, they could hold onto the stromatolites better, and not be swept off by waves and tides. They found ways to position themselves advantageously within the layers of a stromatolite, even orienting vertically to avoid the sun’s harmful ultraviolet rays.
Photo Source: The Wikimedia Foundation
Basically, multicellularity enabled cyanobacteria to outcompete single-cell organisms. The resulting growth of their populations increased the overall amount of oxygen released during photosynthesis. In a quick 150 million years, the planet’s atmosphere became oxygen-rich. Cyanobacteria were responsible for the most significant climate change in our planet’s history, creating the air we breathe and a protective shield from the Sun’s harmful rays.
Of course, the Great Oxygenation Event was also Earth’s first mass extinction. Most organisms alive at the time were anaerobic — intolerant of oxygen — and they all died off. The other side of the coin is that cyanobacteria caused nearly every other living thing to become extinct. Small quantities of anaerobic life exist today in oxygen-free environments, for example, microbes living around hydrothermal vents on the ocean floor, or safely ensconced inside another organism’s oxygen-free gut.
Yet ultimately, oxygen’s transformative effects were more creative than destructive. The new presence of oxygen affected chemical interactions between rocks, causing explosive growth in the diversity of Earth’s minerals. And, being a reactive gas, oxygen allowed for the emergence of larger, more complex life forms, like humans.
Cyanobacteria are also considered by many scientists to be the ancestors of all plants. The theory goes that, at some point, a single-celled organism ingested a cyanobacteria but did not digest it, and the cyanobacteria continued to photosynthesize inside its host — like chloroplasts do inside plants.
Today, cyanobacteria perform 90% of photosynthesis in the planet’s oceans. Cyanobacteria comprise the most significant and prolific phylum of bacteria, abundant in freshwater and marine environments, anywhere there’s moisture, even in Antarctica and the fur of sloths.
If you’ve ever caught a snowflake on your tongue, you’ve likely swallowed a bacterium called Pseudomonas syringae. Don’t worry, it’s harmless. The rod-shaped, Gram-negative bacteria can be found in the exact center of trillions of snowflakes. Its presence there is directly tied to the formation of the snowflakes themselves.
Snowflakes don’t just materialize out of thin air. Every unique snowflake initially forms around what scientists call an ice nucleator. An ice nucleator is small enough to stay aloft in a cloud. It’s also solid, a tiny solid speck of matter onto which water vapor in a cloud can collect and freeze.
In higher, colder clouds, most ice nucleators are inorganic particles of dust, soot or ash.
But in lower clouds, where the majority of classically intricate snowflakes form, almost all ice nucleators are organic. They can be a bit of pollen, a fungal spore, or a microorganism. Surprisingly, many of latter are alive before, during, and after a snowflake develops around them.
Over the past two decades, scientists have discovered that the skies overhead are not an empty void but actually are absolutely teeming with microbial life. Microbes get swept up off the ground by wind and evaporation and become the ultimate jet-setters — traveling long distances in floating ecosystems. Clouds and airstreams transport googles of single-cell life forms around the globe.
Pseudomonas syringae is the most prolific snowflake-starting bacteria.
Like all bacteria, Pseudomonas syringae is a single-cell organism. What makes it an especially adept ice nucleator is a special protein that coats the outside of its body. The structure of this protein is such that it forces water molecules that come into contact with it to arrange like they do when water is in ice form. It happens that water molecules already arranged like ice become ice quicker, freezing and thereby starting a snowflake at slightly warmer temperatures than are otherwise required to start snowflakes. That’s how Pseudomonas syringae are able to transform water vapor into ice at temperatures higher than cloud freezing. The protein enables them to make more snowflakes than other ice nucleators.
Pseudomonas syringae are so good at starting snowflakes in fact, that we add dead ones to artificial snow machines all the time to make artificial snow. If you’ve ever skied on a trail covered in artificial snow, you’ve zipped over many Pseudomonas syringae.
So what happens once a snowflake starts forming around a Pseudomonas syringae? As more and more water molecules attach and freeze onto the microbe, the organism becomes entirely encased in ice. Patterned crystals extend in all directions from the bacterium, fanning out into an exquisite frozen parachute ten thousand times its size. When the snowflake has grown so large that it becomes heavier than the surrounding air, it begins somersaulting downward, hurtling the frozen bacterium toward earth.
It’s reasonable to speculate, since such large populations of bacteria regularly undergo this frigid ritual, that being frozen alive is not deadly but even somehow beneficial to them. Assuming Pseudomonas syringae are not a bunch of kamakazes, what good is being frozen alive?
From the microbe’s perspective, starting a snowflake represents an important aspect of its grand plan for world domination — or at least for expanding its species’ reach into new territories. Pseudomonas syringae bacteria prefer to feed on certain agricultural plants. (Which makes it not a favorite with farmers and agricultural interests.) A bacterium can be lifted from plants in a crop field by wind or evaporation up into the air, where it may travel hundreds or thousands of miles in any prevailing direction. It withstands cold temperatures and can even absorb airborne nutrients and reproduce up in the clouds.
But ultimately, life is easier on land, and that’s where a snowflake comes in handy. With the snowflake’s growth initiated by the bacterium, more and more water vapor molecules glom on in a symmetrical formation.
Photo Credit: Prof. Kenneth Libbrecht, CalTech
Once the snowflake grows heavier than the surrounding air, it falls, carrying its founding partner back to the ground. When the snowflake melts, the bacterium defrosts. Then it is free to snack on new food sources, and reproduce to create new bacterial colonies that will spread its genes.
Bacterial ice nucleators including Pseudomonas syringae don’t know they’re being so clever of course. But they don’t need to know because, as one of the earliest life forms on the planet, bacteria have been shaped longer than any other species by the optimizing genius of Evolution.
–Drift off to visions of macro snowflakes here and here.
READ: Snowflake Self-Organization
by Wonder Science
A snowflake is made up of billions of water molecules, each one identical to every other. And yet somehow in a snowflake a single ingredient is able to form endlessly varying, intricate, and symmetrical designs. How do water molecules do it?
The surprising truth is that in order to freeze, water molecules assume a mineral formation. A basic hexagonal ring arrangement of six H2O molecules is repeated millions of times in every direction, creating a crystalline lattice. A snowflake has a crystal structure made of inorganic molecules (containing no carbon), and therefore technically qualifies as a mineral. A temporary status, granted, because once the snowflake melts into liquid or vapor, its constituent H2O molecules degenerate into less orderly configurations.
The hexagonal arrangement is apparent on both the smallest and largest levels of the ice crystal. The overall shape of a snowflake displays its utmost internal organization. But exactly how do H2O molecules transition from the chaotic dance of water vapor in a cloud to the orderly repetition in the crystalline lattice of a snowflake? It’s through one of Nature’s most powerful and prevalent forces — self-organization.
Self-organization is defined as a process through which some form of overall order arises from local interactions between the parts of an initially disordered system. Self-organization occurs across a wide array of disciplines, including physics, chemistry, biology, and, most recently, in human society and computer science. Some examples include flocking in birds, social behavior of certain insects, traffic patterns, pattern formation, swarm robots, optimization algorithms, and the growth of slime molds.
Self-organization is spontaneous and not controlled by any external agent.
Certainly the inside of a cloud is a disorganized system if ever there were one — with water vapor blowing this way and that in the shifting wind, and subject to constant fluctuations in temperature and air pressure. But from this initial chaos emerges a pristine symmetrical snowflake. This tiny miracle is actually due to four main factors: the polarity of H2O, the dynamic growth of the ice lattice, faceting, and branching.
A frozen water molecule contains three atoms of course: one oxygen atom attached to two Hydrogen atoms. The angle formed by the hydrogen bonds is always 104.5 degrees.
Consulting the Periodic Table, we can see that an oxygen atom has a larger mass than the hydrogen atom — oxygen is eight times as large. The hulking oxygen nucleus with 8 protons and 8 neutrons exerts a stronger gravitational pull on its 8 electrons, drawing them close. Importantly for snowflake formation, the oxygen nucleus even draws hydrogen’s electrons ever so slightly towards it as well. Not enough to pull the electrons out of orbit around the hydrogen nucleus. This it the polarity of H2O.
Electrons are negatively charged particles. The greater proximity of electrons to oxygen than to hydrogen confers an ever-so-slightly slightly negative charge to oxygen, and an ever-so-slightly positive charge to the hydrogen. This polarity determines everything about a snowflake’s shape.
If you’ve ever played with magnets, you know that like charges repel and opposite charges attract. So when multiple water molecules bond with each other, it’s always between the slightly-negative oxygen of one H2O and the slightly-positive hydrogen of the other H2O. Floating water molecules attach to the growing snowflake only oxygens to hydrogens.
Because of that 104.5 degree angle between the hydrogen atoms in each H2O molecule, new bonds between different water molecules happen to form rings of six H2O. The ring of six H2O is called the unit cell or the lattice, because it is the smallest unit of organization. As more and more rings of six H2O molecules self-assemble, the ice extends into a crystalline lattice, repeating the one basic molecular unit in all directions. The growth of a lattice is the reason ice is classified as a mineral.
That’s how the six-sided, hexagonal symmetry of the snowflake begins at the molecular level, 10 million times smaller than the final ice crystal.
But what keeps the snowflake from growing indefinitely as an undifferentiated lattice? How do the six branches form? It’s due to the hexagonal ring shape of its unit cell.
Snowflakes become six-sided as self-organization continues through a process called faceting. Water molecules diffusing through a cloud collide with a growing ice lattice on all sides. Some molecules bounce off. Others attach. Many evaporate. The edge of an ice lattice is a very dynamic region.
We recommend you watch the Wonder Science video, Self-Organizing Snowflake, to help visualize faceting. All you need to take away is this: once an initial few water molecules freeze together in ringed unit cells*, the rest of the incoming molecules attach in accordance with that specific pattern. The ice lattice grows into a six-sided prism shape because of the 6 molecule ring unit cell.
A water molecule hitting the lattice attaches when there are available atoms with which to bond. The edges of a growing lattice offer more points of attachment than the top and bottom, so the lattice grows into a flat disc. Furthermore, the lattice grows into a six-sided prism because of the six-ringed unit cell. Smooth edges of the lattice offer fewer points of attachment. The incomplete parts of the lattice grasp incoming water molecules strongly at multiple points of attachment. Hence the rough edges of the lattice grow faster. When the rough edges fill in and become smooth, fewer new water molecules attach, and the growth of that edge naturally slows.
The existence of a hexagonal prism triggers a new dynamic: branching. The six corners of the ice prism stick out into the air further than the sides of the prism, causing diffusing water molecules in the cloud to hit the corners sooner and more frequently.
At first the corners grow by just the tiniest bit. But with every molecule that preferentially bonds to the corners of the prism, the corners grow larger, causing even more diffusing water molecules to attach. This activity becomes a positive feedback loop. The corners grow larger and larger. All the while, the developing ice prism spins inside the cloud, exposing all sides more or less equally to the presence of water vapor. Soon, branching structures form outward from all six corners of the ice prism.
The snowflake is a delightful instance of order emerging out of the simple interactions between identical water molecules. No one is in charge of building a snowflake and yet they. Every six-sided starlet is a triumph of non-engineering.