The video below shows a wood stove fan. These fans function with no outside input of electricity. They use the heat gradient between the bottom of the fan in contact with the stove and the top of the fan, which is designed to radiate heat. The bottom to top flow of heat goes through an array of semiconductors. Semiconductors are used in most electronic devices today ranging from smartphones to computers. Semiconductors contain elements such as germanium or compounds such as cadmium selenide combined with specific impurities that alter their physical properties.
In the case of the fan, the elements of the semiconductor sandwiched between the hot and cooler areas of the gradient produce an electric current (Seebeck Effect) that is used to drive a small motor which rotates the blades of the fan. The rotating of the blades propels heat from the stove into the room and helps further cool the top of the fan enhancing the bottom to top heat gradient.
On a recent trip to the University of Tennessee (UT) we learned that robots were delivering food on campus, so we placed an order for Chinese food from the restaurant Panda Express. The robot arrived with our food about 25 minutes after we ordered. When we opened the lid of the robot, it played the song I had chosen (Here Comes the Sun by The Beatles). After retrieving the food and closing the lid, the robot said, “Thank you, go Vols” (the UT team is the “Volunteers”) and drove away.
These self-driving food delivery robots are the creation of the company Starship Technologies. The robots use a combination of machine learning, artificial intelligence, and sensors to cross streets and avoid pedestrians and other obstacles. They can deliver the food during rain, snow, or heat. The company has placed its robots in several university campuses in the U.S. and throughout the world.
Is this the future of food delivery? And what is next? Mail, packages, drones? The future is creeping closer and closer to the present!
Have you ever wondered why cat’s eyes are the way they are? In bright light the pupils of cats look like slits whereas in dim light their pupils look circular. I have documented this phenomenon in the pictures of Science Cat below.
Cats are predators that are biologically designed to hunt at night. The shape of cat’s pupils is an adaptation that reduces the amount of glare during the day and increases the amount of light that enters the eyes during the night. Whereas circular pupils such as those of humans can expand their area 15-fold in going from a fully constricted to a fully dilated shape, those of cats undergo a 135-fold change during this transition. But what allows cats to see better at night is that the density of a type of light receptor in their eyes called “rods” is 6 to 8 times higher than that of a human. Rods permit the detection of very faint light signals. Additionally, cats have a layer of tissue in the back of their retinas called the tapetum lucidum which reflects light back into the light receptors of the eye increasing the amount of light that they can detect. This is why if you use flash photography at night on a cat, like I did with Science Cat below, they look like little demons!
The photographs of Science Cat are property of the author and can only be used with permission.
The art of making music by running a bow against a saw arose in several countries around the world when steel saws became widely available some 300 years ago. In the United States it originated in the Appalachian Mountains and reached a peak in popularity in the vaudeville acts of the 1920s and 1930s but faded towards the second world war. However, the art still endures on today maintained alive by many performers.
The sound produced by a musical saw occurs as a result of the friction exerted by the bow upon the saw which causes the steel surface to vibrate, much in the same way as the string of a guitar vibrates when plucked. These vibrations produce compression waves in the surrounding air which are transmitted to our ears and are perceived as sound.
In a guitar, the pitch of the vibrating string can be adjusted by reducing its effective length, which guitarists do by pressing their fingers to the string. In the musical saw, something similar happens when the performer bends and twists the surface of the saw. This creates bounds that restrict the vibrations and changes their pitch in relation to where the bow is applied. The mathematics of the sounds produced by musical saws is quite complex.
In the video below, former university professor turned street performer, Robert (The Saw Man) Maddox, plays Somewhere My Love (Lara’s theme from the movie Dr. Zhivago) in downtown Knoxville, Tennessee.
In our cultural ethos, rattlesnakes are inextricably linked with the wild west of tumbleweeds, cowboys, horses, sheriffs, and outlaws. These reptiles are indigenous to the Americas and have several notable features. The most distinctive is the rattle at the tip of their tails which they can move 60 or more times per second producing a sound which serves as a warning of their proximity. Rattlesnakes are deaf, but they compensate for this by having a highly developed sense of smell. In fact, the reason why rattlesnakes (and other snakes) constantly stick their tongues in and out of their mouths is to bring scent particles in contact with their smell organs which lie in the roof of the mouth.
Rattlesnakes do not hear sound, rather they have an inner ear that is very sensitive to vibrations in the ground which are transmitted to it by the snake’s muscles and jaw bones. Besides also having very good vision, rattlesnakes have the ability to sense heat thanks to organs located behind each nostril which gives the snakes the ability of heat vision allowing them to hunt in the dark. Rattlesnakes have a venom which they inject through their fangs when they bite much in the same way that a hypodermic needle works. The venom consists of proteins that break down cells and tissues, as well as anticoagulants and neurotoxins that cause circulatory arrest and respiratory paralysis.
The Timber Rattlesnake (Crotalus horridus) featured in the video below was filmed at the Zoo Knoxville in Knoxville, Tennessee.
On a trip to Knoxville, Tennessee, I was informed that a specimen of Titan Arum, the world’s tallest flower, was about to bloom at the Hesler Biology Building of the University of Tennessee (UT), and that this event was open to the public. This was an amazing opportunity to see this tropical plant which exists mostly in a vegetative state for up to 8 years and then blooms only for about 24 to 36 hours!
Titan Arum is the name coined by the English naturalist Sir David Attenborough to be used instead of the actual scientific name of the plant, Amorphophallus titanium, which can be a little rude to use during blooming events that attract crowds including families with children. Titan Arum was discovered in the jungles of Sumatra by the Florentine naturalist Odoardo Beccari in 1878. The central column of the flower called the Spadix, which can reach heights of 12 feet, is what is responsible for the name of the genus of the plant. The spadix is surrounded by the spathe, which is the blood-red colored petal-like structure that opens during a bloom.
The plant I saw was a specimen sporting a spadix of modest size (3.7 feet) and is called “Rotty Top” partly after the song “Rocky Top”, which is one of the official state songs of Tennessee and the unofficial fighting song of UT sport teams, and partly because of the scent the plant emanates when blooming. Titan Arum is also called the "Corpse Flower" because it emits a smell similar to that of decomposing flesh to attract its chief pollinators, carrion beetles, and flesh flies. The chemicals mostly responsible for the rotting flesh smell are dimethyl di- and trisulphides but also include isovaleric acid (sweaty feet), trimethylamine (rotting fish), and methyl thioacetate (garlic & cheese). At the same time that the plant emits it foul odor, it also heats up to 80-90 °F to help volatilize the chemicals and spread the smell. Titan Arum belongs to a small group of plants that can generate heat such as Skunk Cabbage to which it is distantly related. Even though the plant was in a glass enclosure with a door, all those in attendance could smell the scent of the flower which would filter out through the borders of the door, and a few people found it strongly nauseating.
Although most people consider the flower of the Titan Arum to be made up of the spadix and the spathe, this is really just an inflorescence (a stalk with many flowers). The real flowers of the Titan Arum are tiny and are located at the base of the spadix. After Rotty Top reached full bloom, the staff cut a rectangular window at the base exposing the flowers. The female flowers are at the very bottom, while the male flowers are further up. I learned that the female flowers mature first and are receptive to pollen, but by the time the male flowers mature, the female flowers are not receptive anymore. This ensures that a given Titan Arum does not pollinate itself and promotes genetic diversity among the plants which rely on their pollinators spreading the pollen from one flower to another.
After blooming, the spadix and spathe degenerate and fall, and the structure that gave rise to them below the ground, called the “corm”, enters a vegetative cycle. The corm is a swollen stem which in the largest Titan Arum plants can weigh up to 200 pounds. When not flowering, the Titan Arum corm emits a single leaf which opens into a tall treelike structure with many branches. This leaf is the plant’s sole photosynthetic organ which produces the energy that is stored in the corm. The leaf dies every year and is replaced by a new one while the plant gathers energy for another blooming. This is a process that can last several years. In the biology building of UT there is a greenhouse where they keep other specimens of Titan Arum in their vegetative cycles.
OK, so now I can cross out “Titan Arum Bloom” from my bucket list!
The photographs belong to the author and can only be used with permission.
Cats are uniquely adapted for jumping and running. Unlike the spinal columns of humans which possess vertebrae that are held together by ligaments, the vertebrae of the spinal columns of cats are held together by muscles. This allows cats to bend their spinal columns into a perfect U shape. Cats can flex and extend their spines in a manner that allows their bodies to act like a spring when running or jumping. Their powerful hindleg muscles also allow them to generate large forces, and the length of their hind limbs relative to their lean body mass maximizes their takeoff velocity when jumping.
In the video below, Science Cat performs a cat jump.
Adam Savage and Jamie Hyneman from Mythbusters wanted to see if an inflatable ball could help their favorite crash test dummy, Buster, survive a fall. First, they attached to Buster a few shock indicator pads (Shockwatches), and then they threw him out of a helicopter hovering at 1,000 feet. They then repeated the process with Buster inside the inflatable ball. You can see the results in the video below posted by the folks of the YouTube channel Discovery.
The shock indicators they used are clever contraptions that contain solutions of different viscosity of red ink and water. When the shock (measured in G forces with “G” being acceleration) is large enough, the red ink solution comes in contact with a white porous material into which it flows making it turn red. The viscosity of the solutions are calibrated to indicate different G forces. These shock indicators can be placed in things that are transported to make sure that they have been handled properly.
The original Mythbusters series ended in 2016, and Savage and Hyneman decided to end their relationship with Buster in true Mythbuster fashion. They welded him to a rocket sled in a flying superman pose and flew him at 780 miles per hour into a wall as shown in the video below.
All of us have seen fire burning. Fire emits light of its own, and the colors we associate with fire are colors such as red, yellow, orange, and blue. Additionally, when a regular light beam is directed at a regular fire, it will go right through it, so fire is not an entity that casts a shadow. In the video below, James Orgill from the YouTube Channel The Action Lab manipulates the lighting and the material burning in the fire to produce black fire, a fire that absorbs light and casts a shadow!
Decomposition is an important process in nature which returns nutrients to the environment, but it’s such a slow process that we can seldom appreciate its progression. In the videos that I’ve selected below, the folks of the YouTube channel TEMPONAUT armed themselves with patience and filmed the slow day by day decomposition of several fruits and vegetables.
The first video is that of a peach rotting. You can see how the mold (probably from the genus Penicillium) that appears is white at first and then turns green when producing spores. Another interesting feature seen in the video is the way the juices of the peach come out as droplets through the mold.
Apart from the obvious changes such as the growth of mold, decomposing fruits experience a large decrease in their mass due to loss of water. This can be easily visualized in the video below which features the decomposition of a honeydew melon fruit placed on a scale.
In the video below, which shows a rotting lemon, you can again see the appearance of a white mold that turns green and covers all the lemon. However, later on you see the appearance of more white mold growing over the green mold on top of the lemon, but this white mold turns a blue color. I don't know if this is a new type of mold that takes over the green one. Also, in the previous videos you probably noticed some tiny things moving all over the moldy surfaces of the rotting fruits and falling over the sides. These are mold mites. These insects feed on the mold. In the video below you can see the little critters laying the whole field of green mold to waste!
The video below shows a potato rotting, and there are closeups filmed in real-time that allow you to see the mold mites clearly.
If you have the curiosity (and the stomach), you can check the TEMPONAUT YouTube channel for time-lapse videos of many other things rotting away.