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For most people, clouds are these fluffy white things floating up in the air, which may give the impression that clouds are light, but nothing could be further from the truth. Clouds are created when water vapor condenses into minute water droplets due to changes in pressure and temperature, and water has weight. Those large cumulus clouds that you see up in the sky actually weigh hundreds of tons! The reason why clouds don’t fall is due to in part the same reason why ships built out of steel don’t sink. The density of the clouds is lower than the density of the underlying air. In other words, a given volume of air below the cloud is heavier than the same volume of air in the cloud, thus the cloud floats on this air. In cumulus clouds, this happens because as the warm air rises from the land it expands and becomes less dense. Additionally, the water droplets that make up most clouds are microscopic, and the effect of gravity on them is negligible and easily counteracted by the updraft currents within the clouds. 
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Kennett Square, Pennsylvania, is the site of Longwood Gardens, a world-class horticultural display garden with a wide variety of plants and trees of both beauty and interest. The garden is the brainchild of its founder, industrialist and financier Pierre DuPont, who began constructing it in 1906. Longwood Gardens features many native and exotic plants both abundant and endangered. But one of the greatest attractions of this site is its water, light, and music show in the Main Fountain Garden. This water display features more than 1,700 jets of water that are programed to move to music. Some of the jets can hurl water up to 175 feet up in the air. The average show, which lasts about 12 minutes, involves recirculating more than 10,000 gallons of water per minute. In the video below you can see a portion of one of the shows during the day. At night, the jets of water are illuminated by LED lights creating a stunning display of color. An additional feature of the show is the fire fountains. These are water fountains that have a fire burning at the top. This effect is achieved by injecting a stream of propane gas into the water jet and igniting it. In the video below you can see the fire fountains during part of one of the shows at night. Many plants have coevolved with other organisms (pollinators) to such an extent that the main or only means the plant has of transporting the male elements (pollen) to the female element (ovule) to assure reproduction is through the intersession of the pollinator. And the same time, many pollinators have become dependent on the nectar and pollen produced by plants for their nutrition. It has been calculated that without pollinators a third of flowering plants would produce no seed and half of all flowering plants would have their fertility reduced by 80%. Pollinators are estimated to contribute 24 billion dollars each year to the US economy by making possible the reproduction of plants of economic importance. The phenomenon of pollination is an active area of research in disciplines such as ecology and evolutionary biology. In the video bellow an Eastern Tiger Swallowtail butterfly (Papilio glaucus) feasts on the nectar of the flower of a thistle plant promoting its reproduction in the process. A wild plant took root in our garden. We decided to let it grow to see what it was. It turned out to be a Late-flowering Boneset Plant (Eupatorium serotinum), also known as Late-flowering Thoroughwort or just Late Boneset.  We immediately noticed that the plant was very fragrant and attracted quite a large number of pollinators. Below you can see a sampling of some of the pollinators that visited the plant. It seemed that all these pollinators were having a good time feasting on the nectar of our boneset plant and contributing to its reproduction. However, we then spotted a large bug feeding on a bee it had just caught. We were surprised at the structure with spokes in the back of the insect. What was this bug?  The bug turned out to a specimen of Arilus cristatus, the North American Wheel Bug. It is presumably called this because the spoke-laden structure in their backs reminds people of a wheel. The wheel bug is a type of the so-called assassin bugs which belong to the family Reduviidae. These bugs stab their prey with their very sharp proboscis and injects them with enzymes that dissolve the interior of their bodies, which they then proceed to drain.  But the wheel bug was not the only assassin lying in wait on our boneset plant. We also spotted a praying mantis lurking among the stems and leaves.  The mantis spotted a bee and moved with lightning speed upon the hapless insect, which became its meal.   So it seemed that our boneset plant could also be a death trap for some of our pollinators. The wheel bug and the mantis are both ambush predators. They frequent scented plants that attract their prey and lie in wait for the right time to attack. The drama of life and death in nature often unfolds right before our eyes, but we don’t notice it. And all it took was a fragrant plant in my garden to bring this reality to my attention. All photographs belong to the author and can only be used with permission. In the field of optics, a caustic is a set of rays of light that have been reflected or refracted by a curved surface and focused into another surface. The classic example of caustics or a network of caustics is the bands of light you get at the bottom of a pool when the light shines from above. The top of the waves crisscrossing the pool act like a convex lens concentrating light on a focal point. This is incidentally why they are called “caustics”, from the Greek “to burn”, as when sunlight is focused by a lens into a small area. If this focal point coincides with the bottom surface of the pool, the caustic band will be sharp, whereas if it doesn’t, the caustic band will be diffuse. On the other hand, the areas between the top of the waves have a concave shape and they act to disperse the light. This is why caustics are separated by areas that seem to be darker. In the video below, I have slowed down the network of caustics in a pool down to 240 frames per second. You can follow the caustic bands and see how they appear, disappear, merge, and separate continuously as a result of the pattern of waves on the surface of the water in the pool. I have previously posted about tensegrity structures. These are structures where the integrity of the whole is maintained by tension among its components. In the video below I show you how to build a simple but amazing tensegrity structure. The video includes an appearance by Science Cat! We tend to associate tail wagging with dogs. Almost everyone has seen happy dogs shaking their tails, and we have jokes and cartoons about it. We even have the phase “wag the dog” to describe when a small or less powerful entity takes control of a bigger or more powerful one. Apart from signaling that they are happy, dogs use their tails to communicate various messages about themselves, but, as it turns out, there are other species of animals besides dogs that use their tails to communicate things, and one of them is cats. Dogs evolved from wolves (Canis Lupus), which live in packs, so they tend to be social and expressive animals. However, domestic cats are evolved from the African Wildcat (Felix sylvestris lybica), which are solitary nocturnal animals, so the tail signals of cats are different from those of dogs. When cats curve and swish their whole tail from side to side it may indicate excitement or deep focus as when stalking a prey. This is a common predatory behavior especially if the ears are standing upright. However, a tail moving back and forth can also signal irritation or pain especially when associated with arched backs and lowered heads. When the cat only swishes the tip of its tail, it indicates that they are about to pounce or they are playing, but it can also signal that they are annoyed. If a cat wants to signal it is happy, it will stick its tail straight up, which in dogs is a sign of alertness, not happiness. In the video below Science Cat demonstrates how cats wag their tails. She is intensely looking at some birds in the bush outside while swishing her tail with her ears upright. One very common illusion employed in theaters, museums, shows and other venues is Pepper’s Ghost. The illusion is named after English scientist John H. Pepper who improved upon a previous ingenious but cumbersome illusion developed by inventor Henry Dircks in 1860. Pepper made the first demonstration of this illusion in 1862. The illusion relies on the fact that whereas light goes through most transparent glasses, a certain percentage of it is reflected by the surface of the glass. In the classical Peppers Ghost illusion, a glass is installed at an angle facing an audience. The audience can see with no problem the action taking place in the stage behind the glass. At some point an actor or an object is illuminated in a compartment that is located to the side of the glass in such a way that the light coming from the actor or object will bounce off the glass and appear to the audience to be coming from the stage as a ghostly apparition. In the photo below, I use a window to generate a version of the Pepper’s Ghost illusion, where I seem to be within the tree outside as a ghostly apparition.  In the video I used an exhibit at the 2019 Prague Quadrennial. I manipulated the see-through and reflection qualities of the glass window of the exhibit as well as the proximity of my phone to the glass, to create a Peper’s Ghost illusion. Note: the photo belongs to the author and can only be used with permission. I woke up one day to gnawing sounds in the attic right above my bed. For the next few days these sounds continued and became very bothersome making it difficult to sleep. Science Cat heard them too. She would stand on her hind legs with her front legs against the wall and look at the ceiling. I suspected we had a squirrel up there. Squirrels are mammals which belong to the order Rodentia. These also include rats, mice, chipmunks, beavers, and porcupines. One defining characteristic of rodents is that they have pairs of sharp incisor teeth in their upper and lower jaws which grow continuously throughout their lives. As a result of this, rodents need to gnaw very often, even if they are not eating, to wear down their teeth. If they don’t do this, their teeth can grow so large that it can kill them by making eating problematic and even piercing the palate of their jaws. Because of this I knew that, if left unchecked, the squirrel could inflict significant damage to our attic overtime. I borrowed a humane animal trap from my neighbor, and following his advice I baited it with a Reese's Peanut Butter Cup (apparently squirrels are suckers for Reese's Peanut Butter Cups). I left the trap overnight in our attic. The next morning Science Cat seemed to hear something. She would pace back and forth in the room with access to the attic. When I placed the ladder to access the attic, she darted up the ladder and stood at the top looking up, so I had to bring her back down.  I opened the trapdoor to the attic, inspected the trap, and found the varmint. It turned out to be a specimen of Sciurus carolinensis or the eastern grey squirrel. Science Cat took great interest in the squirrel.  My wife and I drove the critter to a nearby forested location and released it into the wild as shown in the video below. There have been no more noises coming from the attic, and I am able to sleep once again just fine. The photos are property of the author and can only be used with permission.  Forced perspective is a technique that exploits the relationship between distance and size to make large objects appear smaller or vice versa. This technique has been exploited in movies such as The Lord of The Rings franchise to make actors appear smaller (Hobbits) with relation to other actors. The technique is also used by professional photographers to create illusions and also by amateur photographers to create fun pictures. The classic use of the force perspective technique is when people get photographed holding up the leaning tower of Pisa in Italy. I made a forced perspective photograph of my own while visiting the Rumsey Monument in Shepherdstown, West Virginia. This is a monument to a local inventor, James Rumsey, who in 1787 became the first person in the United States to build and pilot a steamboat. The monument, which is located near the Potomac River where Rumsey made his trek, contains a 75-foot-tall granite column capped with a globe. The column sits atop a 40 square feet concrete base. In the photograph I use forced perspective to make it look like I am wearing the column of the monument on my head!  Leaning tower of Pisa image from flickr by Jeffrey is used here under an Attribution-NoDerivs 2.0 Generic (CC BY-ND 2.0) license. The photographs of the Rumsey monuments belong to the author and can only be used with permission. |
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