Tag: heat

Posted in Science & Nature

Entropy

Posted on by Jinavie

The Second Law of Thermodynamics, one of the fundamental principles of physics, dictates that the entropy of an isolated system never decreases over time. If left alone, an isolated system will always progress towards thermodynamic equilibrium: a state of maximum entropy.

These are very long, technical words: what is entropy and why should you care?

Simply put, entropy can be thought of as a marker of how chaotic and disordered a system is. This is a misleading simplification, as entropy actually is more about energy moving from a concentrated state to a more dispersed state, but it is easier to understand this way.

An example would be a hot cup of coffee cooling down. The hot coffee is a concentrated locus of energy. But over time this energy gets dispersed throughout the coffee and into the surrounding (cooler) air and converts the water into steam. Energy slowly disperses out, until the coffee becomes room temperature.

This makes the Second Law of Thermodynamics more relatable. When have you ever seen a cold cup of coffee heat up by itself without any heat source? For that matter, a spilt glass of milk never reassembles itself. Balls sporadically arranged on a pool table will never form an orderly triangle by themselves. A dead person cannot miraculously come back to life. Without external influence, you cannot reverse the entropy of a system.

In a way, you could define life itself as a battle against entropy.

The cells in our body are continuously fighting to preserve order and energy in our body, such as actively pumping salts in and out to maintain concentration gradients, rigorously preserving our body temperature to ensure that enzymes can function optimally and breaking down food to fuel all the processes keeping us alive. If we are left truly isolated (no heat, no food, no oxygen), then entropy will build in our body until we die.

The concept of entropy can be particularly motivating when we consider that entropy doesn’t just apply to physical energy. Our brains are also subject to entropy where, if left alone, it will default to the lowest energy state.

This means that if we don’t pay attention, we will quickly find ourselves mindlessly consuming content, scrolling social media, binging television and procrastinating. It is so easy to waste away the potential energy in our brain if we let entropy have its way.

The best way to counter this is by focussing on a key part of the Second Law of Thermodynamics. It says that entropy never decreases in an “isolated” system. Some things are irreversible, like the inevitable heat death of the universe or our own mortality, but we can enact some change to restore some order to some systems. A cold cup of coffee can be reheated in a microwave. A leaking tire can be patched up and inflated. A spilt glass of milk can be turned back upright and refilled with more milk.

Ergo, we must prevent ourselves from being isolated systems. There are three main ways we can do this.

The first is to stimulate ourselves from external sources, reheating our metaphorical cup of coffee. This includes hobbies and interests, learning new things and expanding your horizons. Our brains are naturally fuelled by curiosity, passion and experiences.

The second is to connect with other people. Healthy social interactions keep us grounded to reality and inspire us to be better versions of ourselves. People can provide us with new knowledge, insights, wisdoms and love.

The last and most important is channelling our own willpower. We must fight against our natural instinct to be lazy by pushing ourselves to get off the couch, to exercise, to work, to create, to produce, to live. This is also the hardest because if it was easy for us to “Just Do It”, we wouldn’t even be discussing how to beat entropy. Therefore, we need to create systems, habits and routines to trick our brain into working and being productive. In no time, you will find yourself auto-adjusting your life to prevent entropic laziness from taking over your life, like homeostasis.

Isaac Asimov’s short story The Last Question tells the story of how even the most powerful supercomputer in the cosmos cannot answer the question of how we can meaningfully reverse entropy in the universe. But turns out we can reverse the entropy of our brain and it is damn well worth the effort.

Posted in Science & Nature

Shooting Star

Posted on by Jinavie

When an object from outer space enters the Earth’s atmosphere, it starts to burn up and creates a brilliant streak in the sky, which we call a meteor or shooting star. Contrary to popular belief, this is not due to friction with the air in the atmosphere.

An object entering the atmosphere is typically travelling at extraordinary speeds. Most meteors are travelling around 20km/s (or 72000km/h) when they hit the atmosphere. At these speeds, air molecules do not have a chance to move out of the way. The meteor will instead collide into the air molecules, pushing them closer and closer to each other, compressing the air in front of it.

As we know from physics class, compression increases temperature in gases as per the ideal gas law (PV=nRT). The impressive entry speed of these meteors result in so much air compression that their surface can heat up to 1650 degrees Celsius.

The heat boils and breaks apart the contents of the meteor, turning it into superheated plasma that gives off a glow. This is the streak of light that we see in the night sky when we wish upon a shooting star.

Posted in Psychology & Medicine

The Importance Of Television

Posted on by Jinavie

Fire is considered one of the most important discoveries in the history of our species. Since the dawn of time, it has provided us with warmth, light, cooked food and the power to invent even more things.

We can see how important fire was to our ancestors from how integral it was within a house.
In prehistoric times, there would always be a fire at the centre of a cave or hut, where the family could gather around for warmth and light. Here, they would warm themselves on a cold winter’s day and cook meat that they hunted during the day to tenderise it.

Unlike the old days, we no longer have open fires in the house. Instead, fire has been split into three different forms.

  • Instead of huddling around an open fire for warmth, we have boilers and hot water cylinders to warm our houses.
  • Instead of cooking our food over a campfire, we have gas or electric stoves and ovens.
  • Instead of the flickering flames providing us with light and distraction, we have television and computers.

Of course, we still have fireplaces, barbeques and candles, but the modern person tends to rely more on modernised versions of fire.

An interesting takeaway from this theory is how television is the modern form of the psychological comfort that fire provided us. In prehistoric times, people would struggle to stay alive, running from predators and hunting to feed the family. Looking at the fire mindlessly at the end of a hard day’s work would have been a way to destress and unwind.

Nowadays, most of us are lucky enough to not have to fear death on a day-to-day basis, but we still suffer constant stress from the busy modern life. Perhaps sitting in front of a television or computer to procrastinate for half an hour is not the worst thing in the world.

That said, everything should be done in moderation. It is good to relax for a set amount of time, but if you spent every evening after work staring at a screen without an original thought, your mind will dull and atrophy.

So, it is good to balance out the mindless entertainment such as comedy or reality shows with films that provoke thoughts and emotions, documentaries that provide you with knowledge, and shows that stimulate your creativity.

Most importantly, what you think and feel and learn after watching these should act as fodder for conversations that help deepen your connection with other people.

Posted in Science & Nature

Discomfort Index

Posted on by Jinavie

Hot and humid weather is quite possibly the worst weather, as most people will feel sticky and uncomfortable, to the point that it will affect their mood and ability to think. This combination is so terrible that weather forecasts often mention a discomfort index (or temperature-humidity index) to highlight how hot and humid the day will be. Discomfort index is calculated as:

DI = 40.6 + 0.72 (dry-bulb temperature + wet-bulb temperature ).

Here, dry bulb temperature is the “ambient temperature” (not considering humidity), while wet bulb temperature accounts for humidity by looking at how low the temperature can get by evaporating water.

Evaporation absorbs heat but can only happen if the air is not saturated with humidity. Therefore, the more humid it is, the more “discomfort” we feel as we cannot sweat off the heat building up inside our bodies.

When the DI is at 70, about 10% of people experience discomfort. At 75, 50% feel discomfort and at 80, most people will feel extremely uncomfortable. A DI of above 85 is virtually intolerable and anything above this, serious conditions such as heat exhaustion and heat stroke can occur.

As our core body temperature rises and we cannot cool down by sweating, we experience thermal stress. Under thermal stress, our concentration and task performance begins to suffer – a phenomenon people will describe as their brain feeling as if it is melting. This is a well-established phenomenon that has significantly affected how architects design offices and homes to improve air flow and temperature control to create an environment with the least thermal stress possible – for both efficiency and comfort.

Posted in Science & Nature

Shared Bodily Warmth

Posted on by Jinavie

Body heat is a vital condition that animals need to survive. It is so vital that when you are hypothermic, your body will override almost everything else to conserve heat as much as possible. Without enough heat, the chemical reactions that fuel your cells will grind to a halt and you will die. To solve the issue of getting heat, nature came up with two answers: endotherms and ectotherms.
Endotherms are organisms that produce their own heat (e.g. mammals) by trapping the heat produced by metabolism and through extra mechanisms such as shivering. Ectotherms rely on absorbing environmental heat (e.g. reptiles), usually through the sun. Because of this, ectotherms suffer a much greater range in body temperature. This means that animals such as lizards will be slower and more sluggish when it is cold.

Being in a cold environment quickens the process of heat loss, robbing you of the precious heat you generate. A solution to this is shared bodily warmth. Also known as kleptothermy, this is a common thermoregulation strategy where a group of animals huddle together to share the heat generated by each other. This increases the efficiency of heat generation (thermogenesis) and the group as a whole can stay warmer for longer. This behaviour is commonly seen in communal animals such as mice, who huddle together even when they are newborns (newborns lose heat much quicker than adults due to the difference in weight to surface area ratio). Some ectotherms such as snakes and lizards also engage in kleptothermy, where by huddling together they increase their effective mass and reduce heat loss.

An interesting case of kleptothermy is seen in Canadian red-sided garter snakes, where the heat is not shared, but stolen. A male snake will sometimes emerge from hibernation and begin to produce fake pheromones to attract other males as if it were a female. Other males are fooled into thinking that the snake is female and approach it to mate. Through this strange process, the snake is able to steal the heat from its rival males and use the extra energy to mate with an actual female (or lose it to an even more cunning male snake).

Posted in Science & Nature

Brazil Nut Effect

Posted on by Jinavie

Have you ever bought a bag of mixed nuts and noticed that Brazil nuts tend to be on the top of the pile? If you put nuts of various sizes in a bag and shake it, you will see that the larger nuts (such as Brazil nuts) will rise to the top slowly. This is strange as common sense dictates that heavier objects sink to the bottom. The strangest thing? No one knows exactly why this happens.

However, there are some persuasive theories. It has been suggested that the so-called Brazil nut effect is due to a phenomenon called granular convection. Convection is usually used to describe the movement of gases and liquids, where heated particles are more active and lighter, thus rising to the top. As the particles rise, they cool down and fall back to the bottom, creating a current. It seems to be that the same can be applied to solid particles, such as nuts. When the jar or bag of nuts is shaken, a vibrational force is applied. Nuts in the middle are pushed upwards by the vibration, with smaller particles filling the gap below. Once the nuts reach the top surface, the vibration pushes the nuts towards the side, where they are then pushed back to the bottom. However, larger nuts like Brazil nuts are too big to fit in this downward current so they stay on the top. 

The Brazil nut effect is not exclusive to Brazil nuts. A similar phenomenon can be seen with any large particles surrounded by smaller particles, like pebbles in sand or coffee beans in ground coffee. The theory of granular convection has still not been fully understood, with various factors such as nut density and air pressure seeming to play a role.

Posted in Science & Nature

Fighting Fire With Fire

Posted on by Jinavie

On a hot summer’s day, one tends to drink cold drinks and eat cold foods to try cool their body down. But an old Korean proverb states that one should control fire with fire (yiyul-chiyul, 이열치열, 以熱治熱). In other words, instead of drinking cold drinks, it is better for your health if you eat hot soup to combat the heat. When the temperature becomes hot, the body redirects blood flow to the skin to cool itself, meaning there is less blood flow to the organs and causing the internal temperature to drop. Although cooling yourself is good, having a cold drink rapidly on a hot day can suddenly cause a large temperature difference between the surface and the organs, leading to digestive problems. In severe cases, it can cause abdominal pain and diarrhoea, with a vicious cycle where the heat is trapped on the surface and you feel even hotter. Ergo, having a hot food like samgyetang (a Korean chicken soup with many nutritious foods to revitalise your health in the summer) warms the organs and allows for better communication between the organs and the skin to effectively overcome the heat.

The philosophy of yiyul-chiyul can be extended beyond the scopes of medicine. Just as the proverb defeat savages with savages (yiyi-jeyi, 이이제이, 以夷制夷) says, one can control a certain force by using the same force on it. A great example is backfires. A forest fire tends to be too large in area to be extinguished with water. But if you deliberately start a fire just beyond its trajectory, it will burn everything as it moves towards the forest fire. Eventually the two fires will meet and without any fuel to consume, both will be extinguished.

Posted in Psychology & Medicine

Hypothermia

Posted on by Jinavie

A person’s body temperature is always maintained between 36.5~37.5°C. This is because enzymes, which are crucial in all physiological reactions in the body, work most efficiently at this temperature. As physiology is essentially a series of chemical reactions, it is heavily dependent on temperature. If the temperature falls, chemical reactions occur slower and vice versa. When body temperature falls below 35°C, metabolism becomes too slow and it poses a risk to the person’s health. This is known as hypothermia.

How does hypothermia affect the body? Hypothermia is categorised into three classes depending on the severity.

  • Mild hypothermia (32~35°C) leads to the slowing of bodily functions, tremors and difficulty in walking. The patient’s speech is impeded and other neurological symptoms such as decreased judgement skills and confusion start to appear. Also, blood pressure, pulse and breathing rate rise.
  • Moderate hypothermia (28~32°C) causes paralysis of muscles and extreme fatigue (they may complain of being sleepy). As blood (carrying heat) is rerouted to major organs, the skin (especially lips and extremities) become white or purple and very cold. Neurological symptoms worsen with amnesia, memory loss, severe confusion and delusion beginning to show. As sustained hypothermia leads to the tremors stopping, one should not take the lack of tremors as a good sign. Heart rate becomes irregular and arrhythmia may occur.
  • Severe hypothermia (20~28°C) leads to chemical reactions becoming so slowed that physiological functions that support life decline dramatically. Heart rate, blood pressure and breathing all lower to dangerous levels and the heart and lungs may stop functioning. As the patient’s major organs begin to shut down, they enter a state of unconsciousness and eventually, clinical death.

As you can see, hypothermia is a highly dangerous situation that can kill. There are some other fascinating facts about hypothermia.

20~50% of hypothermia death cases are associated with paradoxical undressing. This is a strange phenomenon where the person begins to take off their clothes due to confusion and a lack of judgement from the hypothermia. One theory suggests it is related to the cold damaging the hypothalamus (which controls body temperature), causing the brain to think that the body temperature is rising. Whatever the reason, it is extremely dangerous as it worsens the hypothermia.

As explained above, severe hypothermia leads to death. But interestingly, hypothermia also protects organs. This is why organs for transplanting are transported in ice. Similarly, there are examples of people who “died” from hypothermia recovering with no brain damage. Because of this, medical professionals traditionally say: “they’re not dead until they’re warm and dead”. In fact, if there is something wrong with the patient’s circulation and there is risk of damage to their organs (such as in surgery), sometimes the patient’s body temperature is forced down with ice water injections and cooling blankets, known as protective hypothermia.

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Posted in Science & Nature

Nuclear Explosion

Posted on by Jinavie

Nuclear weapons are quite possibly the most dangerous weapons mankind has ever developed. Through the use of nuclear fission, atoms are split to release the massive amounts of energy contained within, causing a gargantuan explosion. When a typical nuclear bomb detonates, energy is released in various forms: blast energy (40~50%), heat (30~50%), radiation (5%) and fallout (5~10%). The distribution of the energy varies according to the type of bomb (e.g. neutron bombs produce significantly more radiation than heat and blast energy).

The initial damage that follows a nuclear explosion is from the blast energy, much like a conventional weapon. The sheer amount of kinetic energy creates a shockwave that pulverises everything in its path, travelling at speeds over 1000km/h. In addition, the heat from the explosion, over ten million degrees celsius at one point, causes vaporisation of all matter within a certain radius, causing a massive release of gases, fuelling the shockwave from the expansion. In the case of the bomb that destroyed Hiroshima, all structures within 1.6km were vaporised and those within a 3.2km radius suffered moderate to severe damage. A modern nuclear weapon is at least tens of times more destructive and will affect a significantly larger area.

At the same time, thermal radiation spreads out in all directions much like sunlight. Thermal radiation travels far further than shockwaves and can cause severe burns and eye injuries (flash blindness) to people in the vicinity (if they are close enough, they will spontaneously combust or melt). Near ground zero (point of explosion), a firestorm may erupt from the sheer amount of heat energy, as observed as a fireball. 

Next comes the indirect effects.
Ionising radiation is produced when atoms are split and these have detrimental effects on living organisms. Not only are they responsible for mutations in the genome, leading to deformed offspring, sterility and cancer, but if there is sufficient radiation, a person will immediately die from acute radiation poisoning.
The same radiation, especially gamma rays, creates what is called an electromagnetic pulse (EMP). EMP is caught by metal objects and induces a high voltage surge, destroying unshielded electronic devices. Sometimes, nuclear bombs are detonated at very high altitudes so that only the EMP affects the ground, damaging enemy communications and destroying entire power grids.
Lastly, radioactive material rains from the sky for long periods of time, also known as fallout. Fallout causes continuous radiation damage in affected areas.

A nuclear bomb is truly a weapon of mass destruction as it utilises various forms of destruction to devastate all life forms within an area spanning several kilometres, even killing over the course of time in the form of radiation.

Posted in Science & Nature

Fire

Posted on by Jinavie

Every creature on earth knows the fearful power of fire. Learning how to utilise it is possibly one of man’s greatest achievements, as it allowed science and technology to kickstart in every way. However, we still lose control over it sometimes and suffer the consequences. Fire can develop from a tiny ember to a full-blown firestorm that incinerates everything in its path. The following are the four stages of fire development:

  • Stage 1 – Incipient stage: No visible smoke and very little heat. Small fire.
  • Stage 2 – Build-up stage: More heat causes pyrolysis (decomposition of material due to heat), releasing combustible gases. May cause a flashover (every combustible surface in the room ignites all at once).
  • Stage 3 – Fully-developed stage: Visible flame, massive amounts of heat, smoke and toxic gases. Everything is burning.
  • Stage 4 – Decay stage: Fire is either contained or extinguished. If not, may spread to other areas (e.g. the next room).

After sufficient heat has built up, fire spreads almost explosively (sometimes literally) causing extensive damage. Thus, the most important part is preventing the fire in the first place or extinguishing a small fire still at the incipient stage. As powerful a tool it may be, it can also destroy everything you hold precious within a matter of hours.

An interesting phenomenon related to fire is backdrafts. This is similar to flashovers (described above) except it is triggered by oxygen rather than a build-up of heat. Both cause a sudden transition from a small fire to a full-scale inferno.
A backdraft occurs when a burning room is filled with pyrolysed, combustible gases but lack the oxygen needed to continue burning as it was used up while the fire was building up. When a firefighter or a broken window causes air to rush into the room, the pressure in the room spikes and every combustible material suddenly bursts into flames, exploding out in a ball of fire. Backdrafts are one of the most dangerous fire phenomena that claim the lives of countless firefighters.