The Deconstruction of Falling Stars

Originally published in the Informanté newspaper on Thursday, 17 December, 2015.

“Space, “ Douglas Adams said, “is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.” And it is. The diameter of the observable universe is estimated at 93 billion light-years, with a light-year being just under 10 trillion kilometres. This is so large (it has 26 zeroes at the end) that it is difficult to comprehend. 

Perhaps just as amazing, is the fact that of all the matter in this universe, 74% is hydrogen, the simplest element, and 24% Helium, the second least complex element. They occur in large molecular clouds across the universe, with these clouds able to stretch almost 100 light-years across and having a mass of up to 6 million times that of the sun. A mass that big has a large gravitational field, and so it is as well with these clouds. 

When these clouds collide, they start to form gravity hotspots, spot where the gravity is stronger than the surrounding area, and they begin to break up. Matter begins to collapse into these hotspots, strengthening them and increasing its gravitation pull. The density of matter at the center of these hotspots increase, and as a result, starts heating up. When there’s enough mass (about 8% the mass of the sun), the temperature can rise up to 10 million degrees Celsius, and at this temperature and in this incredibly dense cloud of matter, something new occurs. Nuclear fusion. 

Hydrogen atoms collide and ‘fuse’ together to form helium. This releases a momentous amount of energy, enough to offset the force of gravity and preventing the cloud from collapsing further inward. This energy release coincidentally also releases photons, or light particles. The cloud of gas lights up, and becomes a star.

But this process consumes the hydrogen, meaning that eventually, it will run out of fuel. Less massive clouds have less gravitational pressure, and fusion occurs more slowly, which means paradoxically that they’ll shine longer. Unfortunately, these red dwarf stars (with a mass of less half that of the sun) also don’t have the gravitational energy to continue fusion after their hydrogen runs out, and after six to twelve trillion years, they die to become white dwarfs – still quite hot, but no longer releasing massive amounts of energy. 

Stars with a mass more than half that of the sun to about ten times its mass burns through its hydrogen more quickly comparatively (from only half a million years for stars ten times as massive as the sun, to 100 million years for stars half as massive), but as more and more of the star turns into helium, the helium sinks to the core. With helium’s greater mass and density, the gravity becomes more intense, speeding up the hydrogen fusion process, and expanding it to a greater and greater area around the helium core. 

The outer layers of the star then expands as fusion moves closer to the surface, and the amount of light it emits increases massively as well, becoming a thousand to ten thousand times brighter. The star becomes a red giant. Eventually, the helium core becomes massive enough and hot enough that it reaches its next stage, helium fusion. At its core, the star fuses helium into carbon and oxygen, and this even greater energy release causes the core to expand, dissipating its outer hydrogen fusion layers, and reducing its energy output. Slowly the helium is used up in fusion, but even these stars are not large enough to induce the next stage of fusion, and they, too, die to become white dwarfs.

But when a star is more than 10 times as massive as the sun, it does not expand into a red giant, as the force of gravity continually causes nuclear fusion. Hydrogen to helium, helium to oxygen and carbon, then those into neon and sulphur – with fusion continually occurring, matter is continually used as fuel, and the star shines as a bright blue supergiant for only a hundred thousand years, until the core starts fusing into iron. This results in the gravitational force becoming so strong that the atoms can no longer stay separate, and the entire core fuses together. Lighter stars have the core fuse together into a neutron star – a single massive atom of billions and billions of neutrons. But in heavier stars the gravity overcomes even light, and the star collapses into a black hole, from which no light can escape. Either way, as a result of this gravitational collapse all fusion energy is released at once, exploding the outer layers of the star into space in what is known as a supernova. 

A supernova is so bright it is briefly brighter than an entire galaxy. The outer layers explode in a shockwave travelling at up to 10% of the speed of light. So much energy is released that nuclear fusion occurs in the shockwave – but unbounded by gravity, it happens more haphazardly that it does in the core, fusing in many different combinations. It is thus in these supernovae shockwaves that all the elements heavier than iron are formed. As they impact other hydrogen clouds, they trigger the formation of new stars – but these new stars now have heavier elements that don’t all collapse to the core, but rather orbit the core. We call them planets. And on some, these heavier elements start combining. Start self-replicating. Start the beginnings of life itself…

Carl Sagan famously said “We are all made of star stuff.” Every atom in your body, and the bodies of everyone around you, was once part of an exploding star, scattered across the cosmos. At this time of year, I cannot think of any other fact that can imprint such a profound connection between ourselves and the universe, and our loved ones, than this.

Tis the Season

Originally published in the Informanté newspaper on Wednesday, 9 December, 2015.

From the earliest times, mankind has looked to the stars for guidance. But not just any stars – our star, Sol, the sun. Barrelling around the supermassive black hole at the centre of the Milky way galaxy at 790 000 km/h, it has provided light and heat for the past 4.57 billion years. Earth formed from its periphery, accreting from its solar nebula, and blasts about its orbit at 107 000 km/h, once a year. And then 200 000 years ago, mankind first appears on Earth’s ovoid surface, spinning around it at 1674 km/h, and looked up.

Because even though most of this movement happened in nearly the same orbital plane to the ecliptic (the path of the sun in the celestial sphere), the earth happened to have a bit of an axial tilt. Specifically, an axial tilt of about 23.4 degrees – the cause of the seasons on earth. The axial tilt changes the intensity of sunlight that reaches us during the year, causing weather changes and making the sun appear higher or lower in the sky during certain times of year.

From its early years, humanity has been economically dependent on the seasons. Mating seasons of animals, planting seasons for crops, and more. But in the cold climates of the northern hemisphere, one season in particular spelled danger. The famine months, or winter, was particularly harsh. Starvation was common, but with our eyes on the skies, we could see the change in the position of the sun.

At the winter solstice, the sun reached its lowest point in the sky, and started to rise again. With most cattle slaughtered so they don’t have to be fed during the winter, and wine and beer made during the year finally fermented and ready for drinking, the sign that the sun was once again rising in the sky became a time for celebration. Ancient sites like Stonehenge, built around 3000 to 2000 BCE, show evidence of this. Stonehenge’s great trilithon was carefully aligned on a sight-line on the winter solstice sunset, indicating that the sun would rise again the next day, and a year was reborn. This has resulted in a great many feasts traditionally celebrated around the solstice.

Indeed, the midwinter feast has become a centrepiece for many a culture. The Roman Republic held its feast of Saturnalia from as early as 497 BCE. With a sacrifice at the Temple of Saturn, then followed by a public banquet, and private gift-giving, with continual partying and a carnival atmosphere, it is no wonder that the poets called it “the best of days.” Saturnalia lasted from 17 to 23 December, with the ceremony of renewal of light by Sol Invictus (Dies Natalis Solis Invicti), the Roman sun god, following on 25 December. 

In Sri Lanka, the Buddhists have been celebrating the solstice since 200 BCE. On the full moon in December, the Unduvapa Poya festival kicks off, commemorating Theri Sangamitta’s day of arrival from India to establish the Order of Nuns and marking her bringing a sapling of the sacred Bodhi-Tree from Bodh Gaya and planting it in Aunradhapura. On this day, Sanghamitta Day, ten ordained nuns initiate the festive celebrations every year. And even in China, they’ve been celebrating the solstice via the Dōngzhì Festival, celebrating the yin and yang philosophy of balance and harmony in the cosmos.

Of course, it was in 325 CE when the solstice festival was incorporated into a religious festival about a teenage pregnancy that was successfully delivered in a stable, due to the lack of any social care. This child would become an icon in this religion, and it is why this time is now known as Christmas. Christianity – perhaps you’ve heard of it? It’s apparently quite popular around these parts.

But Christianity was not immediately popular, and even up to the 14th century, the Germanic peoples of northern Europe continued their solstice festival traditions, called the yuletide, celebrated with feasts of meat and toasts. Toasts to Odin "for victory and power to the king", to the gods Njörðr and Freyr "for good harvests and for peace", and to the king was drunk. Toasts to departed family were also common. It is from the Yule that the Christmas traditions of a tree and a wreath come from.

Even in Muslim countries, the winter solstice is celebrated. In Iran, Shab-e Yaldā is celebrated on the "longest and darkest night of the year," and friends and family gather to eat, drink and read poetry. Red coloured fruit and nuts are eaten, symbolizing the red hues of dawn and the glow of life. 

The latest in the long line of solstice celebrations, of course, is Festivus. Originally a family tradition of the O’Keefe’s in the United States, it became a popular celebration after being televised in the sitcom Seinfeld. Described as "the perfect secular theme for an all-inclusive December gathering," it presents itself as an alternative for the commercialisation of Christmas. It’s “a Festivus for the rest of us.”

Here in Namibia, of course, we’ll be experiencing the summer solstice, but we’ll still be celebrating. After all, humanity has become one big family over the years, and now we all celebrate together. So on Tuesday, 22 December 2015, at 06h49, the sun will be directly above the tropic of Capricorn, the solstice will have occurred. Feast, and have a toast with the family you’ve still got, remembering those you’ve lost.

The Rising Tide

Originally published in the Informanté newspaper on Thursday, 3 December, 2015.

This week, the nations of the world descended upon Paris. But unlike a month ago, when France was in the spotlight due to terrorist attacks, this time it is a matter of grave importance to the entire world. This, of course, is the 2015 United Nations Climate Change Conference, running from 30 November to 11 December. The conference aims to achieve a legally binding and universal agreement on climate change from all the nations of the world.

Here in Namibia, of course, we have been feeling the effects of climate change quite a bit over the past few years. The increase in temperatures globally has led to increasing weather abnormalities. In particular, atmospheric circulation, which greatly determines precipitation, or rainfall. 

Specifically, atmospheric conditions are determined by three circular patterns of winds that determine cloud movements and rainfall. The first of these is called the Hadley cell, named after George Hadley, who explained the trade winds that blow towards the equator low in the atmosphere (where the rainclouds are), whereafter it heats up, and thus rises high up, cools down, and has high atmospheric winds blowing outwards from the equator. 

Similarly, the polar cells operate in the opposite direction. Hot air from the 60th latitude line rises, and is blown high in the atmosphere to the poles. There the air cools down, drops, and results in low atmospheric winds blowing out from the poles, with the attendant snow storms etc. that is common near the polar regions.

The third cell, named the Ferrel cell after William Ferrel, who theorized it in the 19th century, exists in between the polar and Hadley cell, in the sub-tropical semi-arid regions such as Namibia. This cell, however, is not a closed loop like the other cells, and depends on them. And unlike those cell that have north-south winds, the Ferrel cell is characterised by westerly winds. It is from these winds that break away from the Hadley cell, that we get our rainfall.

The increases in global temperature is causing the polar and Ferrel cells to weaken, and cause the Hadley cell to grow. In effect, this causes dry regions to become even drier, with wet regions becoming wetter, with more storms.

Unfortunately, the Climate Change Conference only has a stated aim of trying to limit global temperature increases to 2 °C. This in itself will still cause devastation, as that will still entail the global sea level rising between 3 and 6 meters. Even in Namibia, this will displace between 2 000 and 28 000 people along the coast. Without this agreement, temperatures could rise by 4 °C, raising sea levels by 7 to 10 meters. Along the coast, that will displace 48 000 to 56 000 Namibian citizens.
At the conference, President Geingob stated, "We must be decisive without further delay and adopt a legally binding agreement that will limit the average global temperature below two degrees Celsius. In the absence of the required political will and concrete actions, future generations will judge us harshly." I cannot agree more.