## Sunday, 8 April 2018

### A guide to the fourth dimension

The idea of this article is to imagine what it would be like to be in four dimensions. Of course, since we live in only three dimensions, it is impossible to visualize a four-dimensional space, but we can show how everything would work in the fourth dimension by using mathematics.

To start with, we need to know what a transition to a higher dimension is like. The start is zero dimensions. In a zero-dimensional world, it is impossible to move, and there would be no space around, and no amounts of anything. There can only be something, or nothing. The shape of a 0-dimensional world is a simple dot.

To go to the first dimension, imagine taking two zero-dimensional worlds(dots), and connecting them. This world is simply a line. In the first dimension, nothing can move past anything else, and any object is basically a line, with varying length. The ends of each line are zero-dimensional points.

To make a two-dimensional world, imagine taking two one-dimensional lines, and connecting them at every point. The result is a flat sheet. An infinite world of two dimensions is called a plane in mathematics. It would be the same as in three dimensions, except that one of the directions is missing, so it would be like moving pieces of paper around on a flat table.

Stepping up to three dimensions can be done by taking two parallel planes and connecting them at each point. This results in a three dimensional space. This is the dimension that we are the most familiar with. Many more things are possible in three dimensions than in two. The second dimension to us would be so thin that it could not influence the third dimension. There are still two-dimensional things in our world, though, like shadows, surfaces and images.

The best way to imagine the fourth dimension would be to recognize that the third dimension is to the fourth dimension as the second is to the third. A four dimensional space would be the space in between two volumes that are separated from each other in only the fourth dimension, which is at right angles to each of our three dimensions. Of course, we know of no evidence that a four dimensional world exists, but it is possible in mathematics.

The simplest way to imagine these transitions through the dimensions is to imagine a hypercube. A hypercube is an object in any dimension, where its lengths in each dimension are the same, and it takes up the maximum amount of space for a given side length. For example, a 1-dimensional hypercube is a line. Stepping up to two dimensions makes it into a square, and in the third dimension it becomes a cube. The 1-dimensional hypercube has two 0-dimensional endpoints. The 2-dimensional hypercube has four 1-dimensional sides and four 0-dimensional corners. The 3-dimensional hypercube is a bit more complicated, with six 2-dimensional faces, twelve 1-dimensional edges and eight 0-dimensional corners. As the hypercube goes up through each dimension, it gains a different property. The next step is where it starts to get weird.
 An animation of a hypercube

A 4-dimensional hypercube is called a tesseract or 8-cell. The tesseract is to the cube as the cube is to the square. Because a square has four sides and a cube has six, a tesseract has eight sides. These 'sides' are all three-dimensional cubes and are called cells. The two additional sides are extended in the fourth dimension as follows: if you go straight ahead all of the way around a cube or a square, you will go around three other sides before you get back to the starting side, and this is the same with a tesseract. Following the normal pattern of hypercubes, each cell of a tesseract has six square sides. Going through any one of those sides takes you onto another side. At each of the 32 edges, three cells meet, and four cells meet at each of the 16 corners. In normal three-dimensional space, four cubes can meet at an edge, and eight can meet at a corner, so at those areas the tesseract would be especially warped from three dimensions.
 The Dali cross

One way to make this all simpler is by unfolding the tesseract, just like how you can unfold a cube into two-dimensional space. In a cube, the resulting shape looks like a cross made of six square panels. In a tesseract, the shape would look like a four-sided cross made of eight cubes, four cubes tall with four additional cubes sticking out in all four directions. This is called a 'net' of a tesseract, which is known as the Dali cross.

The common way to display a tesseract(see below) is to have a cube with a smaller one inside it, linked to the bigger one by twelve walls, one for each edge of the inside cube. The inner cube is the cell that is facing away from us in the fourth dimension, and the space in between the inner and outer cubes is divided by the walls into six semi-trapezoidal shapes. These shapes are six of the other cells. The last one, which is facing toward us in the fourth dimension, is the bigger cube and has all of the other cells shown inside it.

This is the classical projection of a tesseract onto three dimensions. It is three-dimensional, but it has all of the same edges, corners and faces of the actual tesseract. The only thing that is changed is the shape. It is what the shadow of a tesseract would look like if it was rotated in the right way.

There are many other shapes in the fourth dimension besides a tesseract, which include 6 shapes that are closely related to the five three-dimensional platonic solids. There is also a shape related to the circle or sphere, which is called the 3-sphere or glome. It consists of all of the points at a certain distance x(in four dimensions) to a certain point. The cross-section of a 3-sphere is a sphere, just like how the cross-section of a tesseract can be a cube.
 The shadow of a rotating 8-cell

Visualizing the fourth dimension is impossible, because we live in only three dimensions, however, there are three different ways we can make a small understanding of the fourth dimension. The first is by using three dimensional graphs that capture some of the elements of the fourth dimension. These can be like shadows or cross-sections of four-dimensional objects. They give some of the information about these objects, but never all of it. The second is by keeping in mind that four dimensions is to three as three is to two, so we can imagine how three dimensional objects would relate to a two-dimensional world.

The third is by using our own fourth dimension: time. Even though we can influence the future and it is impossible to look into it, and we can only see three dimensions, time can still be compared to a fourth. We can represent a four dimensional object by using time as one of the axes. Maybe we do live a four dimensional world.

## Friday, 15 December 2017

### How will the universe end?

Right now, all mass as we know it is composed of energy, because it is contained in the bonds in between the particles in atoms. Energy is also stored in other forms, including heat, electricity, the gravitational field, motion and in many other places. So where is it all going? There are three main theories for the end of the universe.

The first theory I am going to write about is the big rip. This is the theory where mass spreads too far apart, because of its momentum from the big bang, and all of the universe slowly rips apart.

Scientists have discovered that most of the galaxies around us are moving away from ours in all directions. What is more, they seem to be spreading apart faster than they are supposed to, considering the gravitational force in between them. It is very mysterious where the extra energy for this comes from, so it is called 'dark energy'. The mysteriousness from this makes us unsure of what will happen to the universe in the future, so we do not know if this theory is correct, However, the next one appears to be the most likely.

The second theory is the case where we consider a certain type of energy carrier: entropy. Entropy is a measurement of what we normally consider as heat. According to the second law of thermodynamics, entropy can be created, but not destroyed. Whenever we heat something up, we are adding to the ever-increasing amount of entropy in the universe, even when the light from the sun is absorbed by the ground, making entropy, or when we make entropy with our bodies. Energy is always carried away by the entropy whenever it is created, and that is where all of the energy from the earth goes; radiating into space being carried by entropy.

A theory for the end of the universe is that all mass will dissolve into energy carried by entropy, and the only thing left will be radiation. This theory is called heat death. The opposite of heat death is if the entropy spreads out too fast because of the expansion of the universe, and stars slowly die out as a result. This is the prevailing theory, and it is called the 'big freeze'. Despite the fact that entropy is always increasing and cannot be stopped, life and stars can only exist by using balances of entropy.

Fortunately, the next is more optimistic than these two, and it is still likely.

The last theory is that, since matter is spread out in the universe, it might fall under the gravitational attraction in between stars and galaxies after gravity overcomes the outward momentum given to the universe by the big bang. This could result in all of the the universe condensing to a single point, which could spark another big bang. This theory is called the 'big crunch', and it states that this might have happened to the universe several, if not infinite, times before.

## Sunday, 13 August 2017

### Struggle to the peak of Mount Barney

Mount Barney is one of the biggest mountains in South East Queensland. It has an interesting history of formation and discovery. It is very popular to climb and it is visible over a very wide range. I have seen it very often when climbing mountains and ridges at the remains of the tweed volcano, a place that is geologically linked to Mount Barney.

Mount Barney was formed when magma from a local geological hotspot intruded into the sandstone above. This hotspot also created the Tweed Volcano, a huge shield volcano that erupted millions of years ago, flooding the surrounding landscape with slowly cooling lava, building up the sides of the volcano with igneous rock. The eroded remnants of the Tweed Volcano are now a circular ring of mountains called the Scenic Rim. There are many national parks in this area, due to its diverse wildlife, stunning gorges and amazing views, all related to the igneous rock and long-ago volcanic eruptions. The Scenic Rim is nearly on the border of Queensland and New South Wales, although it is mostly in the latter. Me and my family have hiked in many national parks in this area, and at the many good viewpoints, one can get an idea of the vast scale of the ancient volcano. Related to the Tweed Volcano are the many igneous intrusions through the overlying sandstone that created mountains in this region.

After the magma intrusions cooled into hard rock, the soft sandstone around the intrusions weathered away. This weathering exposed the jagged peaks of mountains, which weathered little. This lead to strange mountainsides and sheer cliffs in many areas, including the area of Mount Barney. The odd rock formations and steep slopes make it a good challenge for backpackers, and it is a challenge that me and some of my family attempted on a weekend backpacking trip.

Mount Barney has an important role in many Australian aboriginal myths and stories, and climbing the mountain is forbidden in their culture. The first European who discovered it named it Mount Lindesay, but the second changed the name and named it after an engineer, giving the name of Mount Lindesay to a nearby mountain which is easily visible from Mount Barney.

There are two main peaks on Mount Barney, the East peak and the West peak. We did not attempt to climb the West peak, because it is far more difficult and only slightly taller than the East peak. To climb the East peak, we took a route up the Southeast ridge, also called Logan's ridge, and went down on the West slope of the peak, down a trail to the saddle in between the two major peaks, then down the South ridge. There are numerous smaller peaks as well, but we did not climb any of them. One thing to look for from near the base of the mountain is the amazing East cliff, a wide vertical free fall that goes down 300 meters from the top of the East peak.

None of the trails on Mount Barney are easy, and they all require a lot of hiking experience. The way we climbed up was along the Southeast ridge, which has good views but is very steep, especially at the top. There seemed to be no end to the sheer, smooth cliffs, the jagged knife-edges of rock, and the small hills, all of which the trail followed, keeping to the side of an arm of rock sometimes, going along the top of a small ridge with cliffs on both sides at other times. The trail was not clearly marked, and we lost it and came back to it about three or four times. The last section of the Southeast ridge, which reached from about 300 meters below the peak up to the top, was extremely steep, nearly a cliff, and we had to use rope at one place at the beginning of that section, and nearly had to use it on several other sections on the way up. Unfortunately, a thick mist was around the top, from a place 400m below the summit, and we did not get a view there, although the views on the way up were amazing. The mist made the climb very cold and wet. By the time we got to the top, we had climbed up an entire kilometer vertically.

After leaving the top, we took a while scrambling down long, flat rocks on the slope down to the saddle. The trail there was not very clear, and we had to rely on pink ribbons tied to bushes to find our way. There were spectacular views from the saddle. There we found the old site of a hut, and the place looked worn down and overgrown. I was disappointed at not being able to see the views at the top, but the view from other places, including the saddle, made the hike worth it. We crossed a small creek and went on a short trail to Rum Jungle.

There are many stages of vegetation on the slopes of the mountain. At the foot it is an ordinary, open eucalyptus forest. Higher up it turns into a shrubby area where there are only lichens, bushes, and a few stunted trees, including the grass tree. On the west-facing slope that we climbed down, there was also sparse vegetation, but of a different type, with less trees and more grass. On the saddle and for a while down the South ridge, the small bushes, tall grass and shrubs give way to dense subtropical rainforest, with a very sudden transition after crossing the small creek that runs along the saddle.

There is one trail on Mount Barney which is good for less experienced hikers. That trail is the South ridge trail, fittingly called the Peasant's trail. It leads from the foot of the mountain up to Rum Jungle, a campsite on the saddle that is in the dense rainforest. The Peasant's trail is what we took on the way down from the saddle. Compared to Logan's ridge, I found it easy and leisurely, but it has its own difficulties.

Mount Barney is surrounded by the boundaries of a national park. In this national park there are many rare species of plants and animals that do not live in many other places, as well as a huge diversity of plant and animals, including many wallabies that we saw near the trail head on the way back from the mountain. Another species that we saw was the red triangle slug, a type of slug that lives along the east coast of New South Wales and Queensland, including the Scenic Rim. The individual that we saw was dark red with a darker red triangle on its back. The nature on and around the mountain makes it a spectacular place, as well as a good hiking challenge. Our visit was enjoyable, peaceful and most of all challenging. If you are experienced at bushwalking and you live in South East Queensland or near the Scenic Rim, I suggest that you give Mount Barney a try.

## Saturday, 5 August 2017

### Top 10 birds you should see in Australia(Part 2)

This is the second part of "Top 10 birds you should see in Australia". If you have not read part 1, I suggest that you read it first, if you have time. However, it is not necessary.

These are my personal top 5 birds that I have seen on road trips through Australia, and around my home. I will include some information about personal experiences I have had around these birds, and also information about identification and birdwatching for those who are interested, as in the previous list.

Note on conversions: Since I have lived outside of the United States for so long, all of the distances and weights in this article are given in the metric system. If you live in the US, you can use this conversion to get an idea of these quantities:
1 centimeter(cm) ~ 0.4 inches(1in = 2.54cm)
1 meter(m) ~ 3.3 feet
1 kilometer(km) ~ 0.62 miles(1mi ~ 1.6km)
1 gram(g) ~ 0.035 ounces(1oz ~ 28g)
1 kilogram(kg) ~ 2.2 pounds

Hopefully I have explained this list briefly enough. It is now time to start.

#### 5: Pied Cormorant

Phalacrocorax varius
 A pied cormorant swimming in the Brisbane river

Pied cormorants are only one of the many common cormorant species in Australia, but they are the most commonly seen ones on the east coast. They are seen swimming in rivers, lakes, or estuaries, and they dive underwater to catch fish. They mostly live close to the coast, and not inland.

When I lived in the Central Coast, close to Sydney, I saw this bird, or possibly some other type of cormorant, on the rocks near the beach almost every time I went there. After it went swimming somewhere else to catch food, it always rested on the same rock to dry off its wings. I have also seen them in Brisbane, swimming in the ocean, reservoirs or the Brisbane river. It is very interesting to watch them feed, as they swim on the surface of the water for a while, then, when they see food underwater, they quickly and gracefully dive down to catch it. Cormorants spend about 20 seconds underwater, on average, before they resurface, and with clear water and direct sunlight, you might be able to track them as they swim.

Description: The pied cormorant is black and white("Pied" means black and white, and this leads to many bird names, such as pied butcherbird, pied currawong, magpie, etc), with black wings, black back, a white neck and white on most of the underside. It can be identified by an orange-yellow patch right in front of the eye. It has a blue-green eye ring.

How to find: Their feathers are not completely waterproof, so pied cormorants are usually seen drying out their wings in the sun, standing on top of rocks. They can also be seen swimming in the water looking for food.  The best place to see cormorants is around bodies of water. They are always close to land, because they only fish in shallow water.

Diet: Pied cormorants mainly eat fish. When they dive, they swim with their webbed feet and steer using their wings, which gives them speed and agility underwater.

#### 4: Black Swan

Cygnus atratus

The black swan is mostly known for its cultural importance, and it is seen as an icon of Australia because of the way they oppose to European swans, being black instead of white and living in the opposite hemisphere. Being part of Australian culture, they can be seen on the flag of Western Australia(Down and right) and the coat of arms(See previous article, "Emu", it is on the bottom middle of the shield).

Black swans live in the south of Australia, and I have seen many of them in Canberra and on the island of Tasmania. They swim in the water most of the time, and I have not seen one walking on land very often. They are not afraid to nest, and even live, near humans, and they are not very shy.
 Western Australian flag

I have seen black swans often on the open waters of Tasmania. When it is not mating season, they move around from place to place, flying frequently and stopping at water to feed. They partner for life, raising one brood per season. Their young are called cygnets.

Description: The black swan, hence its name, is mostly black, but it has white wing-tips that are visible in flight. Its bill is dark red, but also has a white tip.

How to find: Black swans are commonly seen in open, clean, still bodies of water. In southern places, such as Tasmania, they are a more common sight and many of them live in southern cities such as Canberra, Melbourne, Adelaide and Hobart. When you are lucky you might see them as a family.

Diet: Black swans feed by stretching down with their long necks and eating algae and other aquatic plants from the bottom. They do this in water about 1m deep.

#### 3: Wedge-tailed Eagle

Aquila audax
 Perching

The Wedge-tailed eagle is the largest bird of prey in Australia, with a wingspan of up to 2.84 meters and a length of up to 1.06 meters. They are accustomed to deserts and mainly live in desert environments, such as the outback, but not in the harshest deserts, and mostly near the edge of the outback. They can, however, occasionally be seen nearer to the coast.

You would be lucky to see one of these birds in the wild. They often circle very high up for hours on end, at about 1,800 meters up, and sometimes much higher. They do this by gliding on thermal air currents, during the hottest part of the day when there can be scorching heat. It can be very hard to see them during these times(Imagine trying to see a 1cm wide object 20m away. It is just about as hard), but most of the times that I saw one in the wild, it was circling straight overhead. Fortunately, they are very distinguishable when flying, even by the silhouette, because of their unique wedge-shaped tail.
 In flight

Wedge-tailed eagles are very territorial birds, and they have a record of attacking other birds, including other wedge-tails, and on occasion attacking and damaging model airplanes, hang gliders, paragliders, survey drones, normal airplanes and helicopters. For food they hunt anything that is convenient, being very adaptive, and they sometimes eat roadkill or other carrion. Once I have seen a wedge-tailed eagle, or a similar species, fly after a dingo that was dragging a dead wallaby across the road. Besides dingoes they compete with other scavengers such as Australian ravens and black kites. When not looking for food or flying, these eagles perch on a rock high up where they can get a good view of their territory.

Description: Wedge-tailed eagles are brown, and the colour of the feathers is a marker for age, since they get darker as they get older. To identify them from other birds, look for the wedge-shaped tail. They are very large birds, 96cm in length on average, which is about as tall as a 3 year old child.

How to find: They can be seen circling in slow loops high in the air in the middle of the day, around noon. Because they use thermals to stay up, they hardly ever have to flap their wings during this kind of flight.

Diet: Basically, being apex predators, wedge-tailed eagles can hunt almost anything. In many places, they eat mainly rabbits, ever since European settlers arrived. They also eat small mammals such as wallabies and possums, and many types of smaller birds including cockatoos, and also reptiles. I have seen them go after carrion such as roadkill, and they scavenge from other predators as well. In groups, they may even hunt large prey like sheep and red kangaroos.

#### 2: Superb Lyrebird

The superb lyrebird is well known as a songbird, and it is named after the male's tail feathers, two of which form the shape of a lyre. It has strong legs and large feet for clawing in the dirt to find food, like the bush turkey, but the superb lyrebird also has other uses for its feet. These lyrebirds are endemic to Australia, and they live on the east coast from Tasmania all of the way up to South East Queensland. A lyrebird appears on the Australian ten-cent coin.

The thing that lyrebirds are most known for is their courtship ritual. During mating season, the male lyrebird prepares for courtship by finding an area under some tall bushes that is safe from predators, but still easily visible from a distance. The male then uses his feet to rake all of the sticks and overlaying leaf litter from a small patch of ground, about 2m wide. As a "courtship dance", the lyrebird arches its long tail feathers over its head, covering it in a light silver canopy, and stands in the middle of the area it raked out, singing its song loudly enough that it can be heard from far away.
 Australian ten-cent coin

The song of a male lyrebird is composed of mimicry of many other sounds, both natural and artificial. It can mimic the sound of up to 20 other birds that live in the same area, and also the sound of a chainsaw, a car alarm, and many others. I have heard more lyrebirds than I have seen, and and first I have mistaken them for other birds, because of their excellent mimicry. I have heard one make the chainsaw sound, the voice of a bell bird, part of the song of a whip bird and an attempt of the call of a kookaburra, all in about 5 minutes, and most of them were imitated almost perfectly. I have also watched one perform its mating dance, and it tended its ground area well, pausing its song to get some dirt or branches out of the way every two minutes or so.

Description: The superb lyrebird is a large brown bird. It is similar in form to the bush turkey, and looks like a large pheasant. The males have a long tail, which consists of a few silvery-white feathers that the bird fans out during display, and two special curving feathers that look like the sides of a lyre. Juveniles and females also have a long tail, but lack the special feathers, and the tail is not as long or ornate.

How to find: It is easiest to find lyrebirds while on bushwalks in dry eucalypt forests about 100km north of Sydney, where they are common. It is easier to hear them than to see them, so listen carefully to find them.

Diet: Same as the Australian brushturkey.

#### 1: Southern Cassowary

Casuarius casuarius
 Wild cassowary at Mission Beach

The southern cassowary is a large, flightless bird, similar to the emu, except that its feathers are black and it has a large crest on the top its head. Its head and neck are distinctly coloured, and it has wattles on its neck. The Southern cassowary lives in southern New Guinea, and some very few places along the northeastern coast of Queensland, in the dense tropical rain forest.

While on a vacation in the tropical north of Queensland, we went to Mission Beach, a small town surrounded by green rainforest-covered hills. While we were there, we went to a building where we met a photographer who took pictures of cassowaries, and he told us about a good place to see them. We went there in the early morning with binoculars, and we were lucky enough to see a cassowary walking about 150 meters away through the early morning mist.
 This is the symbol for the Cassowary Coast shire region. It represents two things at once.

Cassowaries can be extremely dangerous birds. Being related to emus and ostriches, they can run far faster than a human, and if they feel threatened, they can deliver a kick fatal to humans. If you come close to a cassowary, you should not approach it or run away. The best thing to do is to slowly back away and keep an eye on it until it walks away.

Many cassowaries get killed off by human activity. Its greatest dangers are deforestation, hunting, roadkill and other animals eating their eggs. As of 2002, there was a declining population of an estimated 10,000-20,000 birds in the world, with approximately 1,500-2,500 birds in Australia. This puts it on the Threatened list with a conservation status of Vulnerable. The Australian population has a status of Endangered. If it goes extinct, it will be very bad for the rainforest, because the southern cassowary can eat fruits of plants that are poisonous to other animals, and the bird is important for distributing the seeds of these plants.

Conservation status: Vulnerable(Endangered in Australia). This is Least Concern for all other birds on this list, but you will still be able to find it if you look in the right places.

Description: The southern cassowary looks like an emu in body shape and size, but the feathers on its back are black instead of brown, as well as some other differences around the head and neck. These differences include that its neck and head are a sharp blue colour, paler at the head, and it has two wattles, which are red by contrast. The back of the neck is also red. It has a huge crest on top of its head. In my experience, it looks a bit like a very large turkey.

How to find: In Australia, you can find them by taking a trip through the rainforest in the north, along the coast(watch out for the crocodiles). To find places where they live, you can look up information or ask people. Cassowaries are active mostly in the early morning. Slow down on the road in areas where cassowaries have been seen to avoid hitting them.

Diet: Fruit, fungi and some insects.

Thank you for reading this list! Unfortunately, I might be busy for the next few weeks, and I might not be able to write very much. If you have any questions/comments, please post them below(Thanks!).

Image sources: Wikimedia commons(except for the first one, which I took myself).

## Monday, 10 July 2017

### Top 10 birds you should see in Australia(Part 1)

We have lived in Australia for almost five years. Over the various road trips I have been on, I have enjoyed seeing a lot of native Australian birds. Below is my personal top ten list of native birds I have seen on these road trips and around my home. If you consider travelling in Australia, be sure to look out for these birds!

Note on conversions: Since I have lived outside of the United States for so long, all of the distances and weights in this article are given in the metric system. If you live in the US, you can use this conversion to get an idea of these quantities:
1 centimeter(cm) ~ 0.4 inches(1in = 2.54cm)
1 meter(m) ~ 3.3 feet
1 kilometer(km) ~ 0.62 miles(1mi ~ 1.6km)
1 gram(g) ~ 0.035 ounces(1oz ~ 28g)
1 kilogram(kg) ~ 2.2 pounds

### 10: Australian Brushturkey

Alectura lathami
 Female Australian brushturkey

The Australian brushturkey, frequently called the bush turkey or scrub turkey, is very common across the entire east coast, from Melbourne to Carins. They are commonly seen in backyards in this region and can become a pest in some areas, since they steal food(usually fruit) often.

Like the Mallee fowl and other Megapodes, male brush turkeys make nests composed of leaf litter, which they rake up using their feet from a large patch of ground. These nests are built under tree shelter and can be a mound up to 1m high and 4m wide. I have seen the building of these nests disturb human habitation when the nest was built in a backyard, the turkeys rake trails of leaf litter across a road or public pathway, or they rake away all of the mulch in a garden. Each male brush-turkey typically has several mates, which lay eggs in its mound. The turkeys check the temperatures using their beaks and rake layers on or off whether the nest is too hot or too cold. A brush-turkey nest can have up to 50 eggs in it. After the chicks hatch, they receive no further parental care.
 Male brushturkey

Description: Australian brushturkeys are not easily confused with any other Australian bird. They are about the size of their relatives, peafowl and junglefowl, and they have a laterally flattened tail. They are mostly black, but they have a red coloured head with no feathers, while females usually have a yellow band around their neck and males have a yellow wattle.

How to find: If you stay in the area for a few days, you would be lucky not to see one! Most of them live close to human habitation and they are common in backyards and on rooftops, but mostly in parks.

Diet: Brush-turkeys dig in the ground for insects, seeds and fruits. To get to insects they break open rotting logs with their feet.

### 9: Australian Pelican

Pelecanus conspicillatus
 Australian pelican swimming

Australian pelicans are a common sight on lakes and rivers where there is not too much human disturbance. They are pretty large birds(medium-sized for pelicans) and have a wingspan of about 2.5m. They usually weigh 4.5-7.5 kilograms. Despite their size, pelicans can fly pretty well(Although they do look kind of awkward when they fly). They can be seen anywhere along the coast.

Lake Eyre is a large salt flat in South Australia which has a watershed spanning a large part of the outback. Once every few years, lake Eyre fills with water. During this time, many species of birds, including pelicans, fly there from all around Australia to gather at the edge and breed. During one of these periods, from 1989-1990, there was an estimated number of 200,000 pelicans, or 80% of Australia's total population. The fact that they can sense the filling of lake Eyre from the coast, in some places thousands of kilometers away, is still a mystery.

Description: Pelicans are mostly white, although the wings are mostly black. Males are larger than females. The Australian pelican holds a world record with the largest bill of any bird, which can be 40-50cm long, longer in males than in females. The pelicans also have a yellow rim around the eyes, making the eyes appear bigger.

How to find: Most pelicans eat fish from the sea or brackish water, so you are likely to see them around docks, harbours or jetties. They scavenge food from humans sometimes, so they often roost near human activity, usually in high places like on lamps and tall poles. They can also be seen flying overhead.

Diet: Pelicans mainly eat fish, which they catch while swimming with their long bills.

### 8: Laughing Kookaburra

Dacelo novaeguineae
 Laughing kookaburra

The Laughing Kookaburra is closely related to the Blue-winged kookaburra, which lives in northern Australia and New Guinea. Laughing kookaburras are known by the popular song, although many people might not know what they are. Kookaburras are in fact a member of the Kingfisher family, and they have heads and beaks suitable for catching fish and other small prey. Most of them, however, do not live near lakes or rivers. They are mostly found around Sydney, but some live in other parts of the East coast.

The most distinctive thing about laughing kookaburras is their call. They use it to warn other kookaburras of danger or as a territorial call to stop other families of kookaburras or other birds from intruding on that family's territory. It starts with one kookaburra, which initialises the call, then continues when others join in as a group. It sounds like laughing or chuckling.

Description: Laughing kookaburras are mostly white, with dark brown on the wings, and the tail is barred with black. They have a brown horizontal eye-stripe, and the upper beak is blue, while the lower part of the beak is white. They also have bright blue spots on their wings.

How to find: Kookaburras are almost always found in trees, on branches that are straight and horizontal, preferring eucalyptus trees. They can be seen in public parks around picnic benches, because they occasionally steal food from humans, but not very often. They can be very brave sometimes and come up to people to beg for food.

Diet: Insects, small lizards and snakes, also fish when present. When they are hunting, they sit very still on a branch, and when they see movement on the ground, they dive down and make their catch, which is interesting to observe.

### 7: Tawny Frogmouth

Podargus strigoides
 Frogmouth perching on a balcony in Sydney

Because of their nocturnal habits, low call, silent flight, diet, and similar colouring, tawny frogmouths are very easily mistaken for owls, although they are more closely related to nightjars than to owls. Tawny frogmouths can be seen anywhere in Australia, even in Tasmania, except for dense rainforests and the outback, and they are very common along the East coast, around Sydney and Brisbane.

Tawny frogmouths sleep during the day, and they need to be safe from predators during this time, so their colours make them able to camouflage. They sleep on tree branches, and their feathers make them able to blend into their surroundings so well, that they are even hard to see in broad daylight. When they are sleeping, tawny frogmouths tilt their head upwards to help this disguise. Even while awake, they hardly move at all, so they might appear to be fake. They sometimes sleep in pairs.

Description: Tawny frogmouths have a mottled pattern that allows them to camouflage, with black, light brown, darker brown, and silver-grey. They have a very big head and a wide beak. During the night, they make a deep, continuous 'ooo-ooo' sound.

How to find: Sometimes, tawny frogmouths can be seen sleeping on a railing during the day. When they do this, you can come close up to them, but it is best to be very quiet, to avoid waking them up. Their call can be heard during the night.

Diet: Tawny frogmouths are carnivores, and they eat mainly worms and insects. They are considered one of the best Australian pest control birds, as they hunt a large variety of the animals usually classified as household pests. Unlike owls, they catch their prey with their beaks instead of their feet.

### 6: Emu

Dromaius novaehollandiae
 An emu in a zoo near Melbourne

The emu is a very large, flightless bird. It is the largest living bird by height apart from its relative, the ostrich, and they have a height that can reach up to 1.9 meters. I have seen emus run very fast, and they can run up to 50 kph(30mph). Emus live almost everywhere in the Australian outback, and also in a few other places, like the Flinders ranges, where they are very common.

The Emu is a major icon of Australia, appearing on the coat of arms and playing a large role in aboriginal mythology. Many aboriginal groups have a 'constellation' in the shape of an emu, made from the dark parts in the Milky Way. This 'constellation' stretches across the Southern Cross and Scorpius, and is only visible in a clear night sky.
 Australian coat of arms, with the emu on the right

Like the brushturkey(above), the male emu does all of the work in caring for the eggs. The male also cares for the chicks. In the Flinders Ranges, I have seen a male emu with eleven chicks, which it was very protective of, rearing up towards the car while the chicks were crossing the road. The only work the female does is laying the eggs.

Description: Emus are very tall, in many cases taller than a person. They are covered with thin, shaggy brown feathers, except for the feet, head and neck. The head and neck have a pattern of black and bright blue and a thin layer of feathers. Emu chicks are brown with white stripes.

How to find: Emus can be seen anywhere in the outback, and sometimes groups walk straight through small towns. They are very easy to find on a drive through the Flinders Ranges or anywhere in the outback.

Diet: Emus are herbivores, and they eat from a large variety of plants, eating fruits, seeds, and small insects, and they swallow small stones to help them digest their food. Living in the outback, they can go several days without water if necessary.

This is the end of part 1. I will post part 2 sometime in the next three weeks, but not sooner than two, because I will be taking a trip to the Netherlands. In the meanwhile, I would like some suggestions of some birds that I can add to my list for part 2, especially birds common in Western Australia, where I have not travelled.

## Friday, 31 March 2017

### Superfluids

Quantum mechanics is very strange and hard to understand. Even today, most of it is merely theoretical, and it behaves much differently than the visible world.

Take quarks, for example. One of the smallest subunits of the things you can see around you are atoms. All atoms have a nucleus, which is composed of protons and neutrons. Protons and neutrons are made of quarks. There are six different types of quarks. They include Up and Down quarks, which protons and neutrons are made of, and also the Strange, Charm, Bottom and Top quarks. The largest type of quarks, Up and Down quarks, are about 10,000 times larger than the smallest type, the Top quark(This can be shown in the zoomable comparison here). The strange thing about this is, that the Top quark is almost 100,000 times as massive! This is an example of a phenomenon of quantum physics that shows that things at that scale greatly differ in behaviour from objects that we can sense. Another phenomenon is that neutrinos coming from the sun change into other types of neutrinos before reaching earth. Most of these phenomena are only theoretical, and cannot be seen or visibly detected, but some of them can.

One of the most remarkable of these phenomena are superfluids. When liquid helium gets lowered to a temperature below -271 degrees Celsius(2.177 degrees above absolute zero), it shows some very strange properties.

Superfluid helium has very little viscosity, so it has little friction with its surroundings. If you stir it, it can keep swirling for days. It is possible to detect its viscosity, but when a superfliud flows through very small holes or channels that normal liquid helium cannot go through, it has no measurable viscosity. This leads to the theory that superfluids are actually a mix of pure superfluid and normal liquid.
 Demonstration of the fountain effect.

The theory that superfluids are all partly normal liquid can be tested by the fountain effect. In the fountain effect, a hole filled with a very fine powder is placed in superfliud helium. The superfliud part goes through the hole and into a bulb, but the liquid helium part cannot go through. If the bulb containing 'pure' superfluid is heated, it turns into an ordinary liquid. More superfluid flows into the bulb, in order to keep the balance of the fluids, which increases the pressure. If the bulb has an outlet at the top, the liquid would 'fountain' out, as shown in this video.

Another strange thing about superfliuds is that they have no thermal resistance. If superfluid helium gets heated slightly in one place, the heat would not spread out slowly, but it would travel outward in waves so fast that the heat is instantly distributed. These waves are known as 'second sound'. This also means that when superfliud helium boils, it does not bubble, but evaporates directly from the surface.
 Superfluid helium escapes containers.

If the bottom of a thin tube is placed in water, the water will flow, seemingly against gravity, up the tube via capillary action. This is how plants get water from the roots to the leaves. All liquids do this, but this is limited by their viscosity. Since superfluids have no viscosity, they can creep through small tubes, and even over the walls of containers, and never stop until they become heated and evaporate. This makes superfluids very difficult to contain. If a container of superfluid helium is held above ground, It will seem that the fluid leaks through the bottom of the container, but interestingly, it actually travels up and over the side of the container and drips off at the bottom. It travels over the container as a film of fluid, only 30 nanometers thick, and at a speed of 20 centimeters per second, known as Rollin film. Waves are observed in Rollin film, and they move across these films. These waves are known as 'third sound'.

Some people argue that superfluids are a state of matter, like solids and liquids. It behaves like a liquid in some ways, but like a gas in other ways.

You can watch this video which demonstrates some of the properties of superfluids.

Resources:

Wikipedia

## Sunday, 19 February 2017

### Anne Frank's diary

Anne Frank was a young Jewish girl whose family went into hiding during the second world war. She was one of the most famous victims of the holocaust because of the fact that she kept a diary during her time in hiding and documented every detail of their time there.

Anne was born in June 1929. She lived in Germany until 1934, when Hitler took control of Germany and the Frank family was forced to flee to the Netherlands. They took residence in Amsterdam.

After the Netherlands surrendered to Germany in 1940, the Franks, being Jewish, started being restricted by many rules and regulations that the Germans had made. Among these were, that Jewish people could not use public transport, Jewish people had to wear a star of David, Jewish people had to go to certain stores and had to send their children to Jewish schools, and many, many more. These rules had started accumulating in Germany over a long period since years before the war, but as they kept getting added, the Jews got more and more restricted. Soon they weren't allowed to have bikes, and they had to walk everywhere.

In June 1942, Anne got a notebook for her thirteenth birthday. She decided to use it as a diary, and started writing in it. On the fifth of July, her family received a call-up from the Nazis and had to move their plan to go into hiding ten days forward. They took their possessions and moved to a section in the back of the factory where Anne's father had worked. They started staying there with another Jewish family.

Anne was the youngest of the people in hiding. She was with her mother and father, Edith and Otto Frank, and her older sister Margot. They were hiding with the Van Pels family, who Anne called the Van Daan family in her diary. The Van Pels family included Auguste and Hermann Van Pels, and their 16-year-old son Peter. In November, since both families had agreed that their hiding place could fit another resident, they were joined by Fritz Pfeffer, a German dentist who wanted to hide from the Nazis but unlike the Franks, who had become fluent at Dutch, Pfeffer spoke a mix of Dutch and German. He was referred to as Albert Dussel in Anne's diary.

In her diary, Anne called their place of hiding the "Achterhuis", translated into English as "secret annex". It was a three-storey area at the back of the factory. The people who worked there brought them food and told them what was happening in the outside world. They also designed and built a bookshelf to conceal the door to the Achterhuis. The bookshelf was on hinges, so that the helpers could easily get in and out.

The residents had to be extremely quiet during the day, to avoid being heard by the people in neighboring buildings. They had to tiptoe around the house, and whisper to each other. Being seen on the street was too risky, and they had to stay in the building for all of the two years they lived there. Everyone there knew, that at any minute they could get arrested by the Germans, and this caused a lot of stress and tension among them. Despite all this, Anne kept a lot of hope and optimism.

During March 1944, Anne Frank heard on the radio that manuscripts such as diaries written during the war would have a chance of being published after the war. Anne, with a view of becoming the author of a published novel, started writing a second edition of her diary, excluding some parts, rewriting others, adding new text, and giving all of the helpers and all of the residents of the Achterhuis pseudonyms.

In the October of 1944, Anne Frank and the other Jews in hiding were found and arrested by German troops. Anne and her sister Margot were taken to the Bergen-Belsen concentration camp, where they died of typhus in February 1945, only two months before the camp was liberated by English soldiers.

Right after the families' arrest, one of the helpers, Miep Gies, found the diary that Anne Frank had left behind. She hoped to return it to Anne after the war. She did not want to read it, because she knew that if she did, she would want to burn it, due to the fact that it contained the names of all of the people who were helping the Franks.

After the war, Anne's father Otto Frank, who, out of the eight Jews that had lived behind the factory, was the only one that survived the war, came back to the place where they had lived for two years. Once Anne's death was announced, Miep gave him the diary, along with the other notebooks and papers that the second edition was written on. Otto used both the original manuscript and the extra notes to construct a version of Anne's diary that got published in Dutch in 1947. The diary was titled "Het Achterhuis" and had five printings by 1950. Otto also assisted in rescuing the building from demolition and turning it into a museum. The museum is known as the "Anne Frankhuis" in the Netherlands and is still accessible today.

Today, Anne Frank's diary is well known and has been translated into 67 languages with over 30 million copies sold. Anne is seen as a symbol of the persecution of Jews during the second world war.