Posted in Science & Nature

Periodical Cicada

In certain parts of eastern North America, it has been noted for centuries that some summers seem to bring a massive swarm of cicadas. Observant naturalists such as Pehr Kalm noted in the mid-1700’s that this mass emergence of adult cicadas happened every 17 years. Since then, a similar pattern has been observed with many different broods of cicadas, with precisely 17 or 13 years between emergences of mature cicadas.

What could possibly explain such a specific, long gap between these spikes?

This phenomenon has been well-researched and the species of cicadas (Magicicada) are known as periodical cicadas. They can be distinguished by their striking black bodies and red eyes. Like most cicadas, periodical cicadas start their lives as nymphs living underground, feeding on tree roots. They take 13 or 17 years (depending on the genus) until they emerge all at once in the summer as mature adults – far longer than the 1-9 years seen in other cicadas. After such a long period of growth, they emerge for a few glorious weeks in the sun to mate, before laying eggs and disappearing.

The astute reader would notice that both 13 and 17 are prime numbers (a number divisible only by itself or 1). Is this a sheer coincidence or a beautiful example of mathematics in nature?

This curious, specifically long period of maturation has been a great point of interest for scientists. The phenomenon of mass, synchronised maturation is a well-documented survival strategy known as predator satiation. Essentially, if the entire population emerges at the same time, predators feast on the large numbers, get full and stop hunting as much. The surviving proportion (still a great number), carry on to reproduce and the species survives.

One theory holds that the prime numbers are so that predators cannot synchronise their population booms with the cicadas. If the cicadas all emerged every 4 years, a predator who matures every 4 or 2 years could exploit this by having a reliable source of food in a cyclical pattern. 13 and 17 are large enough prime numbers that it would be very difficult for a predator to synchronise its maturation cycles with.

Another possible theory is that it is a remnant of a survival strategy from the Ice Age. Mathematical models have shown that staying as a nymph for a longer period increased the chances of adults emerging during a warm summer, rather than when it is too cold for reproduction. This resulted in broods of varying, lengthy cycles, but this created another problem: hybridisation. When broods of different cycle lengths intermingled, hybridisation could occur and disrupt the precise timing of maturation cycles, decreasing the brood’s survival rate. Prime number cycles such as 13 or 17 years have a much less chance of hybridisation, increasing the survival rate.

As Galileo Galilei said, mathematics is the language in which the universe is written. It is fascinating to see examples of how maths can influence natural phenomena, even the life cycles of insects.

Posted in Life & Happiness

Decade Review

A year is the amount of time the Earth takes to rotate around the Sun once. But strictly speaking, this does not have a large impact on our lives or our progress and growth as a person. The concept of a year is largely a construct of our minds to keep track of time; we could just as easily count time in 100-day increments or 3 years, given that most of our lives are not based on agriculture anymore. However, keeping track of time in years is useful because it gives us a reference frame, letting us compare our lives to a set point in the past, or to set goals for a set point in the future.

The practise of taking stock of the year that has been is great because we are naturally blind to change when it happens slowly. We are very bad at noticing gradual changes, so we will often be surprised that our hair looks longer or our body looks better than the past when we look at an old photo. Therefore, reviewing an entire year worth of moments and change will show you exactly how much we have experienced and grown. There will be many relationships and connections you’ve deepened, adventures you had forgotten about and much personal growth that seem so much healthier and more mature compared to your past self.

If that is the case for reviewing a year, then how about reviewing an entire decade? The close of a decade is a rare moment and ten years is a surprisingly long period of time when you really think about it. Some people reading this may be so young that they do not even know exactly what they were like or what happened ten years ago.

Look back on your past decade: how was it? Walk down memory lane in your head, through your journals and photo albums, reviewing and reflecting on how your life played out the past ten years.

  • What were some of the best and worst moments of each year?
  • What were the memorable moments and photos and stories?
  • What big events happened?
  • Where did you travel to?
  • What new skills or passions did you pick up on the way?
  • What new people came into your life and where are they now?
  • How have you grown in the past ten years?
  • What goals and dreams have you achieved in that time?
  • Most importantly: how happy are you now, and what things have contributed to your happiness/unhappiness?

You will be surprised to find the amount of content ten years can contain and how remarkable the amount of change is possible in ten years. It makes you wonder what the next decade has in store for you; what exciting journeys and meetings, what joys and sorrows, what growth and improvements await you?

Posted in Life & Happiness

Time Divided

Even though time is continuous, we like to think of think of time in segments.

The most basic unit is the year. Every time the Earth rotates once around the Sun, we take stock of the year gone by, while setting resolutions for the next year. Technically, whether it is 300 or 400 days, time has passed, yet we always mark changes by the number of years. For example, we use age as a marker of what stage of life we should be at (even if it is not a very accurate marker).

Another classic example is the four seasons. The making of accurate calendars and units of time was critical in the development of agriculture as it allowed us to plant many different crops with high efficiency and yield. In older times, people may have marked time by reminiscing what happened around the time of the last harvest while eating food made with ingredients harvested at that time.

Some segments are less regular, such as the last time you caught up with someone, or whenever you have a big life change such as moving cities. Some people may mark the chapters of life by the person they were dating at the time, or the stage of professional development, such as what year of university they were in.

Why do we obsessively divide time and remember our lives in artificial, bite-sized chunks? Our brains are very good at noticing patterns and change, but not so good when the changes are gradual and continuous (change blindness). Ergo, dividing up time into segments help us process the past.

It is hard to notice how much someone’s hair has grown if you see them every day. It is hard to notice how different you and your partner have become with time until a conflict arises. It is hard to notice how much we have grown and matured and changed without consciously reflecting from time to time.

Another interesting thing to consider is that what you use as a marker of time may suggest what you are prioritising. When you look back, what is the unit of time you use to divide your life? Is it the last time you moved cities? Your last boyfriend or girlfriend? Your last big trip? A moment where you came to an epiphany?

Whatever it is, it is a useful practice to periodically look back on all the segments that make up your life, such as by keeping a journal and reading it later. This will let you be more aware of how you are developing as a person and help you steer yourself in the general direction that you want your life to take you. At the very least, it is amusing to notice the subtle differences between the past and the present you.

Posted in Science & Nature

History Of The Earth

The Earth has been around for a good 4.6 billion years. Let us compress the long time from the Earth’s birth to today (2012) into one year to put everything in perspective.

The Earth’s history starts on January 1, 00:00:00. The Earth is a hard sphere, barren as any other planet. Incessant wind and rain erode away the barren mountains and tectonic forces create new ones. Nothing much happens for the next three months. Then, around the start of April, life begins in the form of bacteria. Over the course of the next few months, the bacteria divide and mutate, slowly forming new life forms that are multicellular. However, all life on Earth are still in the oceans.

Life on land only starts in the end of November, when plants begin to settle on land. Plants expertly take the abundant carbon dioxide in the atmosphere and convert it into oxygen. By early December, the oceans are teeming with fish, some of which adapt to living on land by developing lungs. These become the first amphibians. Insects also populate the land and become one of the most diverse types of life.

In December 12, reptiles evolve and the land is ruled by dinosaurs, but only for 9 days until they are wiped off the face of the Earth by a meteorite on December 20. Mammals quickly take the niche left by dinosaurs, populating the entire world. Even at this late time, there are no signs of humans.

December 31, humans have still not arrived on Earth. They only appear around 8pm, where the first hominids venture on to the plains of Africa. At 10pm, the Ice Age begins and the Earth is covered by a thick white sheet of ice. The ice comes and goes three more times. At 11:59pm, human civilisation begins as cities begin to rise. 22 seconds before the end of the year, the Egyptians build their pyramids. More monuments arise within seconds. At 11:59:47pm, Jesus teaches the people to love one another, until he is killed a millisecond later. In the last second of the year (about 150 years), humanity: has two major world wars, take to the skies, create the nuclear bomb that can wipe out all life on Earth and even step foot on the Moon.

We may like to think that we have made a significant impact in the history of the Earth, but we have only existed for an infinitesimally small fraction of the history. We are but a dot on the grand scheme of natural history.