Living in a bubble on Great Barrier Island How things have changed since my last post! No doubt you too are wondering what this mega-upheaval is all about and where it’s going. I’d just relished a second heavenly herbal weekend with Mary Allan, featuring her herbal medicine-making workshop ... … where we made all of these – thyme- and garlic-infused honey, kawa kawa- and comfrey-infused oil, fire cider and lip balm, plus a tincture ... ... and had lots of fun as we chopped, chatted and learned how to build our natural immunity with herbs.... ... The next day Ro and I celebrated five years on the island (photo from our early days here) … when all of a sudden life changed all over the planet. With literally nothing happening here to write about, it’s a perfect time to send along some of the science-y bits I wrote over the years that never fit when lots was happening! So let’s learn about about stars, trees and time. Private lives of the stars, continued Further illumination of stellar mysteries from the talk two years back by New Zealand astronomer John Hearnshaw. This episode delves into the speed and mass of stars. How fast are the stars moving? The Doppler effect, first identified in 1842, comes in handy to answer this question. You’ve probably heard of it: a change in the frequency of sound waves or light waves as the source and observer move towards or away from each other. The example we were given in high school was the change in the pitch of a train whistle as the train approaches and then carries on down the track. Similarly, light waves from the stars change frequency – observed as colour – as the star moves relative to us. There’s a shift towards the blue end of the spectrum as a star moves towards us, and a red shift as it moves away. Using these shifts, clever astronomers of the late 1800s developed stellar spectroscopy to deduce the velocity of stars. If you want to take a crack at guessing the average speed of stars in kilometres per hour or second, now’s the time to pause and consider, before you begin to read the next paragraph! Hint: If you were a (person-sized) star, you could travel 25 km in a little less than a second. The answer is…. Most stars move at about 100,000 kilometres per hour (kph) relative to the sun, or 30 kilometres per second (kps). A few zip along at more than 360,000 kph (100 kps). Not one star ever observed in the Milky Way has revved up to “hypervelocity” – 1,000,000 kph, or about 300 kps, which is fast enough to escape the gravity of the galaxy, though every now and then a hypervelocity star enters and exits. Nowadays astronomers use the red and blue shifts to calculate a star’s speed to a precision of 3 meters per second! The Milky Way from two perspectives How massive are the stars? First of all, what is mass? It’s a measure of gravitational attraction. Physicists can determine the mass of a star by studying its orbit, but they need some clues indicating what forces are affecting the orbit. Did you know that most stars are part of a binary pair, or even a triplet or higher multiple? From this distance, many pairs seem to merge into one. Alpha Centauri, our nearest star, is a binary pair we can easily see. Alpha Centauri A and Alpha Centauri B are in an 80-year elliptical orbit around each other, sharing a centre of mass. “Simply” measure the effects of the two stars on their orbits and you can work out their mass. Alpha Centauri A & B (lower left) are the pointer stars to the Southern Cross (centre). Alpha Centauri A & B through the Hubble telescope. Or maybe they’re headlamps on a rainy night The sun is one of perhaps 15 percent of stars that are solitary. Luckily there’s another way to determine the mass of dwarf and mid-size stars: their mass correlates with their temperature, which is correlated with their colour. The sun’s mass is so colossal it’s difficult to comprehend. It’s 2 x 1030 kilograms, or 2,000,000,000,000,000,000,000,000,000,000 kg, which 3,000,000 times greater than the mass of the Earth. “Hot dwarves” are even more massive, and stars with the least mass are 100 times less massive than the sun. Why are trees tree-shaped? And why do some, like pohutukawa, have large side branches and others, like pines, have small side branches? We take for granted that trees are fundamentally similar, with wide trunks splitting into smaller branches. There’s a reason for this nearly universal size relationship – the need for trees to support themselves and their branches, possibly for centuries. Trees have developed some neat tricks to keep their trunks upright and their branches aloft! For some, including pohutukawa, oak and sycamore, the wood in each branch’s lower half is slightly compressed while the top half is stretched, which takes the weight off the branch. This layer, called reaction wood, is reinforcement for the increasing weight of the growing branch. Pohutukawa at Medlands For other trees, the reaction wood is on the underside of the branches, so the branches are pushed up, not pulled from above. This adaptation isn’t as effective, so these trees can’t support large side branches. Instead they have a thick vertical trunk with much smaller side branches, and they grow to be conical: pines, spruce and firs. Kahikatea, the New Zealand white pine Trees deal with a lot of wind. Their branches sway nicely in the breeze, but if branches bend too far they’ll snap. Yet a thick branch that doesn’t bend easily is also heavy, so it adds stress where it forks off from the rest of the tree. That’s why where a tree forks, the diameters of the two forking branches together equal the diameter of the sturdier main branch. All trees follow this pattern to minimise bending and snapping in the wind. Flexing branches also make trees more robust. Each branch sways at its own rate, pushing and pulling on the trunk at different times, all out of sync. Sharing the energy puts less stress on the roots, so the tree is more likely to weather a storm. These structural ingenuities are what makes a tree look like a tree. Nature is not only abundant, it’s also brilliant! What makes time special? That’s the topic of this final instalment from “The Nature of Time”, the fourth annual “No Barriers – Small Island Big Ideas” festival of the brain in October 2018. Though the four experts could only conclude is that time is “a big ball of wibbly wobbly, timey wimey … stuff” or even worse, “a big invisible thing that will kill you”, each took a crack at elucidating a tantalising but elusive concept that’s evaded scientists and philosophers since not long after the dawn of time. The last speaker was Craig Callendar, who flew all the way from California for a time-lagged couple of days. (Are at-will flights a thing of the past?) He’s a philosopher of science at the Institute of Practical Ethics – “Science for the Common Good” in San Diego. His 2017 book “What Makes Time Special?”, and his talk on the Barrier, tackled the conflict between our intuitive model of time as flowing and the “static” or “block” time of fundamental physics. Craig barely made it through the panel discussion with his eyes open, but he got himself together to talk about some very heavy duty stuff, though to him it’s child’s play by now. We think that time flows, he pointed out, like a spotlight moving up a map of our life. Our lives are a story with memories and other ingredients of a self that maintains an identity through time despite superficial changes. But physics tells us there is no time, only space-time. In the static view, our lives are a streak on the world line, forever there on the timeless “block” of all events, and so perhaps we are eternal. You and I experience time as an ever-changing structure. Starting in childhood, we instinctively model time as having a flowing present that divides a fixed past from open future. This model is deeply saturated within our language, thought and behaviour, but physicists say that it’s rubbish! As Einstein put it: For most of us, said Craig, time is general concept with many components that are central to our whole idea of it – the flow of time, its direction, sequence and duration, simultaneity, a “special” present that’s shared everywhere, time dragging or speeding up, and time as the fourth dimension. However, over time physicists have been gradually tearing apart these notions, using logic to detach our intuitively derived properties one by one. In fact, as science progressed, time has been shedding so many properties it has all but evaporated! There’s so little left, we can hardly call it time anymore. Craig explained the origin of our flowing-present model of time as a natural reaction to the perceptual and evolutionary challenges thrown at us. We’re constantly bombarded with information coming in through different senses from different directions at different speeds. It’s a chaotic mess that we do our best to make sense of in order to live. Sometimes that means integrating our perceptions and experiences into an intuitive but useful order and projecting it onto the world, even though our conclusions are at odds with the conclusions of science. Our view of time makes the world easier to describe but in fact has no independent existence. Once we become aware of the scientific picture of time, reconciling it with our inner picture is a fundamental dilemma. Modelling time as flowing makes sense even if it misrepresents it. Craig concluded with the lovely conciliatory idea that physics doesn’t explain the full richness of human experience. So what is time? Philosophers, physicists and everyday thinkers have long pondered the question, but to everyone but geologists it seems to lead only through labyrinths to find only paradoxes. Saint Augustine of fourth century Algeria wrote: “When you do not ask me what time is, I know, but once you ask me I do not know…. How can the past and future be, when the past no longer is, and the future is not yet? As for the present, if it were always present and never moved on to become the past, it would not be time, but eternity.” ⏱ ⏱ ⏱ ⏱ ⏱ ⏱ ⏱ ⏱ Water The Barrier's longest drought in living memory began in the spring of 2018. With one exception we’ve had only meagre falls all this time, and less than 1/3 of normal rainfall last year. As the rainless months dragged on, the local board set up a water source behind the council building. Carrying water home in containers only goes so far, and the only water deliveries on the island are of unpotable water from a stream. Since our early days here we’ve been urging the board to get community bores drilled south, central and north, with a clean tanker to deliver potable water to people’s water tanks. They agreed to the need, but no action yet. Denya We haven’t seen our dear friend Denya in 40 years. We first met her at a Doug Kirshaw concert in downstate New York in the early 1970s, where she had a wee stall selling her bead and shell jewellery. Now, as the pandemic’s tentacles had stretched all the way to Cape Cod, Massachusetts, all of a sudden emails weren’t enough and we had a rash of phone calls for the first time ever! Denya’s a professional musician, delighting audiences for decades with her fiddle playing and vocals, solo and with different groups at different times and places, at least until her life as she knew it was put on hold. Garden After months of stress from wind and drought and looking worse than pathetic, and then, following what seemed hardly any rain at all, our garden responded gratefully to even 10 mm from the sky. It breathed a sigh of relief and started to grow almost uncannily lushly. Kale, New Zealand spinach and mizuna grew bigger than ever. Kaitoke Beach from Palmers Beach. The arrow more or less marks the path through the dunes to Oceanview Road. South end of Blind Bay on the west (Hauraki Gulf) side of the island Wetlands (not my photo) Coast of Rakitu Island Gerald often boats out there, 2.5 km from Okiwi Passion, for fishing, or did for years before boating and fishing became taboo for a month (and we all hope no longer than that). Interior of central GBI from the Medlands overlook From our deck Here’s a wee pandemic-themed acrostic puzzle Ro and I made up! After you guess the answers to the clues, the first letters of the answers will form a two-word phrase reading from top to bottom.
_ _ _ _ - _ _ _ _ _ _ _ Enjoy quiet days and evenings at home _ _ _ _ _ _ Out of the question these days _ _ _ A invisible medium for disaster _ _ _ ! What everyone will say in celebration when this is all over _ _ _ _ _ _ _ _ _ _ _ _ _ Do this often as you sing Happy Birthday twice _ _ _ _ _ _ _ _ _ _ Small, round, blue prevention that grows in bunches on trees _ _ _ _ _ _ _ _ Happy release that’s wonderful for stress reduction _ _ _ _ What the world needs now more than ever Answer next time!
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