Steuard Jensen

@steuard.bsky.social

613 Followers 125 Following

Physics professor, Tolkien scholar, JoCoNaut, and all-around science nerd. he/him

One search result turns up for "sustainable truffula tree farming".
An intersection at night, with a handful of streetlights and house lights and headlights creating a diffuse glow through a substantial fog of firework smoke.
Part of the Chicago skyline in early evening with lights in scattered windows and dark silhouettes of trees against the sky, with the crescent moon and Venus adjacent above and rainbow Pride colors decorating some of the skyscrapers.
A female duck huddles protectively over her six ducklings next to the wall of the fully enclosed courtyard inside our science building. In the background you can see the door to the hallway, propped open with a brick.
Me, a smiling middle-aged white guy with glasses, wearing a renaissance fair outfit (white shirt laced up in front, under a maroon vest/jacket with blue accents, plus a "tam" hat) and carrying a bright blue plastic ukulele.
A drawing in dynamic style of a defiant five-year-old girl with dark bobbed hair (seen as if looking up from ground level) shouting to her foe, pointing a finger with one hand while the other clenches behind her in a fist. On her head is a borrowed paper crown labeled "KING"; on her flowing nightshirt is a smiling cartoon narwhal. Behind her on both sides are clustered heaps of scared but eager kids. The caption below the picture reads: "Make no more clouds. I have drawn the rainbow here." Part of a page from Bea Wolf, Zach Weinersmith's retelling of Beowulf (illustrated by Boulet) as a story of kids defending their treehouse from the threat of growing up.
An illustration from the manga "Nausicaä of the Valley of the Wind" by Hayao Miyazaki. The title character, seated in the foreground, is a young woman with light skin and red-brown hair wearing a blue tunic and matching boots and thick gloves. She is gazing at something to the viewer's left with a small, peaceful smile on her face, while a small fox-squirrel stands on her shoulder and stares in the same direction. She is sitting on a spike of the reddish-brown discarded shell of a giant insect (only a tiny portion of the head is in the picture's frame) directly in front of two light-blue transparent eyes (each of them as big as she is). Falling like snow all around her are the small, puffy spores of toxic forest vegetation.
A plate covered with Swedish Christmas Eve food: meatballs and potato sausage and potatoes (all covered in cream sauce) plus fresh green beans and slices of homemade limpa bread.
Stars in the clear night sky shining outside my back door above my neighbors' house, whose roof and chimney are dimly visible in the dark with the bare branches of a tree slightly illuminated behind them. The brightest point in the sky (and the one that first caught my attention tonight, as a twinkling star caught Sam's in Mordor) is Jupiter, centered vertically near the left. The constellation Orion is vivid on the right.
Screenshot of a New York Times headline and accompanying photo, reading: "Prince Andrew to Be Stripped of His Royal Title". (Andrew doesn't look too happy about this development.) [Subtitle: The extraordinary move caps his fall from grace over his ties to the convicted sexual predator Jeffrey Epstein.]
A mug full of freshly made hot chocolate sits on a green placemat on a wooden table. The mug is white ceramic, and the outside is covered with a Halloween scene with ghosts flying around haunted houses.
The cover of the book "Moonshot: The Flight of Apollo 11", by Brian Floca. The image on the cover is a drawn or painted illustration of a black night sky full of stars, with the moon centered near the top (a crescent of it illuminated, but the rest still dim but visible). Centered near the bottom of the cover is a detailed drawing of the joined spacecraft Columbia (a shiny silver metal cylinder covered with various hatches and attachments) and Eagle (a shiny golden boxy craft with four landing legs folded up along its corners). The cover includes medals/seals for a couple of children's book awards, but its biggest selling point is a quote from Michael Collins himself: "Reading Moonshot gave me the feeling I was back up in space."
Dirac notation for the action of the position operator x-hat acting on a state psi, and then written in the position basis. The first term is "x-bra acting on x-hat acting on psi-ket", which equals "x times the bracket of x-bra with psi-ket", which is by definition "x times the wavefunction psi(x)".
The same diagram from earlier of an astronaut and their green-haired twin staying home. This time, though, a series of solid and dashed reddish lines criss-cross the diagram at various angles, illustrating how the astronaut might label time coordinates in their accelerated reference frame. (For each of the three different accelerated motion segments of the motion—rightward away from home, leftward to reverse toward home, and rightward to slow down while returning home—the red lines all come together at a single point "behind" the curve of the acceleration.) Three triangular wedge-shaped regions in the graph (extending outward from those singular points toward the sides of the graph) are shaded grey because the coordinate lines are ambiguous and overlapping there.
A screenshot of the app's user interface, including parts of the diagrams at the top (showing the motion of a house, a charging rhino, and a few flashes of light as seen in two different reference frames, along with animated motion panels below each one). In each diagram, one of the rhino images is selected (highlighted inside a yellow circle). Underneath the diagrams are a set of controls: undo/redo, animation play/pause, reference frame velocity selection, a panel showing detailed information about the selected event on the rhino's trajectory, controls for adjusting the diagram coordinates, and controls to load an example scenario or copy a permanent link to the current diagram state. Finally, sections at the bottom provide details and controls for any standalone events or any trajectories shown.
A screenshot of my spacetime diagram web app, showing diagrams describing the same events and motion in two different inertial frames ("Home Frame" on the left and "Other Frame" on the right). Each diagram shows a "graph paper" grid with the vertical axis labeled "t" or "t prime" and the horizontal axis labeled "x" or "x prime". Faintly in the background of each is a tilted diamond-like grid showing the coordinate grid of the other frame. Each diagram shows three lines going up the page (toward higher t), but they go straight up in the Home Frame and up along parallel diagonal lines in the Other Frame. There are also 45° lines going upward from a shining event marked at the origin. A yellow horizontal line is drawn across each diagram at the same height somewhere in the middle. Below each diagram is a flat panel showing the locations of each object at the time corresponding to the height of the yellow line: two firecrackers, a person with green hair in the middle, and a couple of blue dots between them. In the scenario below the Other Frame diagram, the firecracker on the left has just exploded.
A simple spacetime diagram labeled "Home Frame", showing a graph paper grid with vertical axis labeled "t" and horizontal "x". A green line representing a person with green hair extends straight up the graph just left of the origin, while a blue line representing an astronaut follows a curving path. The astronaut's line goes straight up from the bottom of the graph to the origin (right next to the green line) and then bends to the right, curving smoothly to a maximum point (six lines up in time and four lines over in space) before curving back to its original x position and straightening back up (next to the green line) to the top of the graph. Red-ish dots representing years of travel are marked along each line, with the green line's dots spaced evenly at each gridline while the blue line's dots are spread wide apart in sections where the graph is tilted farthest from vertical. A yellow line extends horizontally across the diagram near the top. Below the diagram, a thin panel shows the location of each of the two people at the time represented by the yellow line, directly below the points where each of their lines intersects the yellow line. Under each picture is a number corresponding to the number of red dots since the origin at that time: seven for the green hair and five for the astronaut.
A simple spacetime diagram labeled "Home Frame", showing a graph paper grid with vertical axis labeled "t" and horizontal "x". An orange line representing a house extends straight up the graph through the origin, while a green line representing a runner tilts up and to the right, and a blue line representing an airplane tilts more steeply to the right. A yellow line extends horizontally across the diagram near the top. Below the diagram, a thin panel shows the location of each of the three objects at the time represented by the yellow line, directly below the points where each of their lines intersects the yellow line.
A screenshot of my spacetime diagram web app, showing diagrams describing the same events and motion in two different inertial frames ("Home Frame" on the left and "Other Frame" on the right). Each diagram shows a "graph paper" grid with the vertical axis labeled "t" or "t prime" and the horizontal axis labeled "x" or "x prime". Faintly in the background of each is a tilted diamond-like grid showing the coordinate grid of the other frame. Each diagram shows three lines going up the page (toward higher t), but they go straight up in the Home Frame and up along parallel diagonal lines in the Other Frame. There are also 45° lines going upward from a shining event marked at the origin. A yellow horizontal line is drawn across each diagram at the same height somewhere in the middle. Below each diagram is a flat panel showing the locations of each object at the time corresponding to the height of the yellow line: two firecrackers, a person with green hair in the middle, and a couple of blue dots between them. In the scenario below the Other Frame diagram, the firecracker on the left has just exploded.
The William Tell bedroom at the Madonna Inn. The exterior walls are built of huge rough stones and feature stained glass windows showing the famous "shoot an apple off your son's head" story. (The carpet is patterned red to match the apple, and the interior walls are bright red.)
A still shot from Terminator 2, showing the shape shifting T1000 robot in the form of John's foster mother. She is holding out one arm, which has taken the shape of a sharp metal blade (dripping with blood). The shape is oddly reminiscent of the recalled steamers' pointy ends in the quoted skeet.
A map of air quality from map.purpleair.com showing air quality levels as colored circles. Green markers for good air are shown through the Dakotas to the west and past Lakes Huron and Erie to the east-southeast, but red and purple bad air spreads southeast from a source in eastern Saskatchewan through Minnesota, Wisconsin, and Michigan.
A view up the hill through a garden to the carillon bell tower of the National Cathedral in Washington, DC.
Me in the foreground in a burgundy polo with Ms13 peeking out from behind with a grin. Behind us is the US Capitol building under a beautiful clear blue sky.
Part of a display of various rocks and dust brought back from the Moon at the Smithsonian Museum of Natural History.
A very blurry and somewhat distorted photo of the moon just a few minutes after totality was reached in a lunar eclipse. Despite the low photo quality, you can see that the ball of the moon is mostly rust-colored against the dark black of space, but the top edge still shows slightly brighter, whiter coloration because it's not very far from the edge of the Earth's umbral shadow.
A political ad for AfD in Germany, featuring a blonde man and woman making a roof shape over their kids by apparently heiling Hitler at each other.
Three trays of cookies sit on the kitchen counter: about two dozen light brown wreath shapes per tray. I am standing by the counter, gradually piping bright green frosting onto the bottom of each cookie to look like leaves spreading out to each side.
A nighttime view of a house decorated with white Christmas lights around the front porch and spiraling up the pillars. The yard is covered in a blanket of snow, and a row of luminarias lines the road. Nearly invisible in the darkness, a young teenager builds a tiny snowman beside the front walk.
A large oval loaf of bread is cooling on a wire rack. It is a fairly dark brown on its crust and lighter brown inside the five diagonal slashes across the top. A dusting of flour is still visible in a few places lower on the loaf.
A big plate of classic American Thanksgiving dinner, with turkey and mashed potatoes and stuffing all covered in homemade gravy and side portions of green beans, cranberry sauce, and a fresh baked roll.
Two pots on a stove. The one on the left contains a thick layer of medium brown liquid and a whisk: flour and butter cooked into a roux, now with added broth. The one on the right contains darker brown clear broth, waiting to be added. (Not shown: pan drippings that will thoroughly darken the gravy and add amazing flavor.)
The same metal loop carrying a counterclockwise electric current as shown earlier, but this time instead of arrows illustrating the magnetic field as a vector we have shown oriented tiles illustrating the magnetic field as a bivector. The tiles inside the loop are parallel to the plane of the loop and all show counterclockwise orientations (matching the direction of the loop current). Beyond the loop, the tiles tilt to the side and around until they are perfectly flat in the plane of the loop (but now "upside down" so the side on top shows a clockwise orientation), and then beneath the plane of the loop continue tilting back in until they come back to where they started.
This image repeats the earlier image of a merry-go-round and a ball swinging in circles on a string. But instead of using vectors to indicate angular velocity omega for each one, the angular velocity of each is shown as a flat tile whose attitude in space matches the angle of the original rotating system and which are labeled to indicate the direction of rotation in the corresponding plane: a counterclockwise arrow on top of the circular tile on the left and arrows along the edges of the rectangular tile on the right. Each tile is labeled as "omega-bivector", where the bivector nature is indicated by a double arrow decoration (pointing left and right) on top of the letter instead of a traditional vector sign. In fact, the (tilted) rectangular tile on the right for the swinging ball has been constructed from the tip-to-tail combination of the ball's position vector (from the center of the circle to the ball) followed by its momentum vector (mass times velocity in the ball's direction of motion). Technically, the result is the angular momentum bivector L rather than the angular velocity omega, but I didn't want to overcomplicate things. (This construction of a bivector parallelogram is called the wedge product of two vectors, and replaces the traditional cross product. The cross product result can be recovered by simply applying the right-hand rule to the bivector tile, with the new vector's length corresponding to the tile's area.)
On the left, vectors A and B are shown tip-to-tail (in that order) forming the first two sides of a parallelogram in the x-y plane. (The other two sides are just negative A and negative B, still all tip-to-tail.) As seen here from above and to the side, the vector arrows describe a counterclockwise cycle around the parallelogram's edges. Starting in the parallelogram's center, vector C points straight up in the z direction (perpendicular to the parallelogram): a right-hand rule illustration shows that the direction of this vector C is where your thumb points if you curl your fingers around the ordered edges of the parallelogram. (This is really illustrating vector C as the cross product of vector A times vector B.) On the right, we see the exact same parallelogram after being reflected along the x-axis (sending x to negative x, as if seen in a mirror parallel to the y-z-plane). Vectors A and B are now A-prime and B-prime with their x-components reversed, so the parallelogram edges now appear to circle clockwise as seen from above. Shown in dim grey is the reflection of vector C, still pointing up in the plus-z direction, but the illustration shows that right-hand rule applied to this reflected parallelogram now curls its fingers clockwise so the thumb points down in the minus-z direction instead. That means that the correct vector C-prime (drawn in black) points down: exactly opposite the dim grey reflection of C you might have expected. (Shown dimly next to that reflection is a reflection of the original right-hand rule, illustrating that after reflection it is now a left hand!) Looking ahead a little, each parallelogram can be interpreted as the bivector tile constructed as the "wedge product" of its two vectors A and B. This wedge product replaces the cross product, and its result behaves entirely normally under reflections as illustrated here, with no weird reversals like what we see for the right-hand rule and cross product.
A generated image of a mostly-horizontal metal loop (tilted slightly down toward the viewer) carrying electric current to the right on the near edge (so, counterclockwise as seen from above). The magnetic field nearby is illustrated as a collection of arrows pointing upward through the center of the loop and then arcing in ever wider circles around through the space outside to come back in from below again.
Two rotating systems: a merry-go-round on the left (rotating in a horizontal plane, counterclockwise as seen from above) and a ball swinging in circles at the end of a string on the right (with the circle in a plane close to vertical and edge-on to the viewer, but tilted a little bit to the right and a little bit toward the viewer so that the motion is visible). Shown below each one is an angular velocity vector omega whose direction is along the axis of rotation in a sense given by a right-hand rule. The right hands in question are illustrated next to each vector: for the merry-go-round, the fingers curl around with the rotating system so that the thumb points straight up from the ground (as does the vector omega). For the swinging ball, the hand is tilted at an angle so the fingers can follow the ball around its circle, and the thumb (and vector) point mostly left but also a bit up and a bit toward the viewer (perpendicular to the plane of rotation).
The bright yellow cover of the American Journal of Physics (Volume 92, No. 12) for December 2024. Featured in the center is a large computer-generated image showing two bar magnets pointing opposite directions with red tape marking their north poles. Magnetic field lines emerge from the poles and stretch between the magnets and into the surrounding space. But threading along the field lines like square beads are a series of tiles, each marked with a clockwise or counterclockwise arrow indicating its orientation. These tiles represent the bivector magnetic field at each location, with the area of the tile proportional to the strength of the field. It is evident that each tile is orthogonal to the field line at its location. The field orientation appears counterclockwise when looking in toward a north pole and clockwise when looking in toward a south pole.
An advertising image for the very old, very shortlived cartoon "Vytor: The Starfire Champion". Muscular dark-haired Vytor is in the center, wearing a frayed, primitive vest with a jagged golden ring attached to the front. At his side is Skyla, with big blue 80s hair and a futuristic bodysuit. A collection of animal-looking humanoids in the lower corner is probably showing their enemies. One of the top corners show a modern-looking cityscape built atop a cloud, and the other corner shows a small golden airplane flying over a deep canyon spanned by a primitive rope bridge.
Google Maps directions for a walking route from Jakarta to Tokyo. The route goes north through Thailand and Myanmar, then along the India/Nepal border, then up north through multiple "-stan" countries before heading east through Russia and crossing to Japan. It's not clear why this was considered better than just walking along the Chinese coast, but there is an icon warning that you might need to take some stairs in Islamabad. The estimated time is 165 days and 20 hours, and a distance of 18,300km.
Me, a 40-something white guy with glasses in a purple collared shirt, smiling proudly while wearing a sticker that proclaims "I VOTED" above a howling, muscular werewolf ripping off its shirt in front of an American flag (as drawn by a 12-year-old).
Me (middle-aged tall white guy with glasses and brown hair) pulling aside my green dress shirt to reveal a T-shirt underneath with the title "LET'S SAY YOU'VE GONE BACK IN TIME". Below that is a dense block of text and diagrams with headings like "HEALTH" and "CHEMISTRY", with instructions on how to rebuild each field from scratch.
A comet in the sky just above the treetops, with its tail stretching high into the sky.
Brilliant reds at the left and greens at the right as the aurora glows above the silhouettes of trees and houses.
A rainbow of aurora across the sky.
My results page, with a cute particle picture featured in the middle: "CONGRATULATIONS! According to your answers, the particle which fits your personality best is a Charm Quark." (Followed by some notes about the actual physics of the particle, which conclude with "likes to team up with strange quarks."
Our brick house in the background behind the evergreen bush at the corner of our yard. Now perched atop the bush is the top of a Harris-Walz campaign sign, tucked in among the branches. (It was originally found folded in half and crammed horizontally deep inside the branches, nearly impossible to see.)
The suspect is an adult Caucasian male, 5'10", with dark hair. He was apprehended wearing a shiny metallic uniform and carrying some sort of advanced laser rifle. [Image actually shows actor Mark Goddard in costume from the TV show "Lost in Space".]
A plastic sleeve encloses The Radium Star Map: "It Shines At Night", created by E.W. Sundell of Oak Park, Ill. It's an aging brown "book" with a standard call number written on the lower-left corner (QB65.Su72) and detailed printed directions for use. (To be clear, I provided the plastic sleeve, as a first step toward containing at least some of the potentially nasty dust. Before that it was just sitting on a normal oversize shelf for 70 years.)
A still from "The Goes Wrong Show", about an acting company that scrambles to stage and perform a new play every week and invariably fails in spectacular and funny ways. (This picture shows three characters in an old-fashioned garden party, with a large bearded man in a brown suit holding a fluffy white cat, a young lady in an overwhelmingly pink dress and a bonnet, and a young mustached man in a tan coat and hat.)
The heroes of the animated 80s cartoon "Spartikus and the Sun Beneath the Sea", striding boldly toward us while framed in front of the titular sun.
Me standing next to Kim on our wedding day, in front of trees and plants in a peaceful garden. I was a 23-year-old man with short brown hair wearing a tuxedo with a white tie; she was a 23-year-old woman with long brown hair wearing a white wedding dress and carrying a bouquet of light colored flowers.
Screencap of text from an NPR article, reading: The world population is predicted to peak at about 10.3 billion people in the 2080s, according to a report released Thursday by the United Nations. The agency's 2024 World Population Prospects study projects the population will begin to fall after that, to about 10.2 billion people by the century’s end. Though, immigration can help slow the decrease.
A light blue dinner plate featuring seared pork tenderloin medallions covered in fennel slivers and an orange-based glaze. Servings of egg noodles and green peas are on the side.
A giant 25-foot-tall(?) statue of a yellow Transformer robot (probably Bumblebee, but off-brand) suntans over an outdoor mall courtyard.
A giant glowing Chinese dragon, whose orange and red coils form a tunnel for visitors to enter through.
I'm visible from the chest down, lying on a blue couch wearing a blue t-shirt and grey shorts. Looking at the camera from between my bare feet and legs is Agatha, a white cat with grey and brown patches above her eyes. Snuggled on the other side of my right leg is Polly, a grey cat with brown and black highlights, curled into a ball fast asleep. Stretched out in the shadows sleeping cuddled between my waist and the back of the couch is her sister Callie, a grey and black cat with brown highlights.
Purple and green lights from the aurora streaked across the night sky, with a bright dot that I'm pretty sure is the International Space Station passing through.
A park outside of Findlay, Ohio with a clear blue sky above wide open grassy areas, various pine trees, and some flowering trees.
The waning half-full moon floats in a light blue morning sky, framed below by a pine tree on the left and bare branches on the right.