Radioactive Decay

You may have heard the term “radioactive”. A lot of the time, it is associated with green goo, superpowers, and mutant creatures. Of course, those things don’t actually happen in real life. In real life, radioactive decay is a scientific process which I will explain.

Types of Radioactive Decay:

Radioactive decay is a process that occurs on the atomic scale. Unstable atoms have unbalanced electrical charges, meaning the subatomic particles that make up the atoms want to balance out the charge. To do this, subatomic particles are ejected from the atom, along with excess energy. Ejected particles and energy is collectively known as radiation. There are three types of radioactive decay: alpha decay, beta decay, and gamma decay. Alpha decay is when two protons and two neutrons are ejected from the atom. The combination of protons and neutrons emitted is identical to the nucleus of a helium atom. Beta decay is when beta particles, which are either electrons or positrons, are emitted. Finally, gamma decay is when a simple energy surge called a gamma ray is released. The time it takes for a particular element to decay is called a half-life.

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Products of Radioactive Decay:

Radioactive decay can result in the production of different isotopes or entirely different elements. Because of the protons and electrons (positrons in the case of antimatter) ejected, beta decay and alpha decay always result in the formation of different elements. Atoms that have yet to undergo radioactive decay are called parent atoms. Atoms that are the result of radioactive decay are called daughter atoms. In alpha decay, the emitted protons and neutrons are identical to the helium nucleus, and therefore equal helium. In addition, the remaining nucleus of the parent atom has been deprived of two protons, and therefore goes down two atomic numbers. For example, uranium is a completely unstable element with the atomic number 92. When it undergoes alpha decay, a helium nucleus is ejected and the remaining nucleus becomes thorium, which has the atomic number of 90. Beta decay also transmutes elements. For example, when a potassium atom ejects electrons, it will decay into either calcium or argon (scientists believe this is selected completely at random). Gamma decay does not transmute elements, because gamma radiation is pure energy.

Nuclear Fusion and Fission

People commonly associate the term “nuclear” with the term “boom”, due to the fact that these processes can indeed cause chaotic explosions. But what exactly happens to cause a nuclear explosion? While I will talk about the inner workings of atomic bombs when I get to the “Nuclear Weapons” post, here I will explain two important scientific processes.

First off, lets establish that “nuclear”does not actually mean “boom”. Nuclear actually refers to atomic nuclei, the cores of atoms. The processes of nuclear fusion and nuclear fission both involve these nuclei.

Nuclear Fusion:

Fusion in the Sun typically follows this chart. The other labeled particles are byproducts of the reaction.
Fusion in the Sun typically follows this chart. The other labeled particles are byproducts of the reaction.

Fusion is the name for two objects colliding, merging, or otherwise connecting. To understand nuclear fusion, you first have to understand particle movements. Atoms with a lot of energy like to use up that energy, like a toddler charged with sugar. For example, when you boil water, you are giving the water molecules heat energy, which makes them want to loosen up and move all over the place as steam. Because of how fast the water is now moving, the particles smash into each other and knock each other around. What happens when you add even more heat? With a lot (and I mean a lot) of heat, the steam will become ionized (see the “The Four States of Matter” post for more information), meaning the electrons that buzz around atomic nuclei will take off and roam independently. At this point, the water is the state of matter called plasma. Stars are very, very hot. This means they are made entirely of plasma. Not water plasma, though. Hydrogen and helium plasma. Because the hydrogen nuclei are so “excited”, they constantly ram into each other. This collision causes the nuclei to lose mass, which is expelled as photons, particles of light energy. Mass can also be expelled as heat. Due to the sheer amount of collision inside the star, it will begin to be very hot and very bright. But the process doesn’t end there. Even after the energy is released, hydrogen atoms “mingle” until they are clumped into groups of four. The results are called helium atoms, because the number of protons has gone from one to two. Hydrogen and helium aren’t the only elements that can fuse, but they are the most common. Heavier elements are much less likely (and much more difficult) to fuse together.


Heavier elements can also fuse together. This diagram shows typical fusion in heavier stars. Notice how elements like nitrogen and oxygen are present.
Heavier elements can also fuse together. This diagram shows typical fusion in heavier stars. Notice how elements like nitrogen and oxygen are present. Nuclear fusion is how many of the heavier elements in the universe were first formed.

Nuclear Fission:

Fission refers to the process of ripping something apart, in this case atomic nuclei. Unlike fusion, which tends to occur in lighter elements, fission tends to occur in heavier elements. In nuclear fission, atomic nuclei are torn apart, releasing tremendous amounts of stored energy, and creating two or more lighter atoms. This is why heavier elements are better fissioned than fused. For example, uranium can split into barium and krypton when it has enough energy. A lot of the energy is released during the reaction.

A diagram of the nuclear fission of uranium into barium and krypton.
A diagram of the nuclear fission of uranium into barium and krypton.

The video below is superb in explaining nuclear fusion and nuclear fission. And it even does so with the help of the evil computer from Valve’s Portal series!


Have you ever wondered why you look like your parents? Well, every person inherits chemical information from their parents. These chemicals instruct the cells in the body to produce certain proteins, which determine each person’s physiology. The branch of science that studies these chemicals is called genetics.


A color-coded strand of DNA.
A color-coded strand of DNA.


To understand genetics, you first have to understand DNA. DNA is short for deoxyribonucleic acid. DNA is a complex macromolecule composed of two main things: four different chemical “bases” called nucleotides, and a “backbone” of alternating sugar (in this case, deoxyribose) and phosphate. The nucleotides, also called nucleobases, are important chemicals. They are adenine, thymine, cytosine, and guanine (often abbreviated ATCG). The sequence of these nucleotides in a DNA molecule is what determines the proteins the molecule codes for. Like letters of the alphabet, there are numerous ways of rearranging the bases. DNA looks somewhat like a twisted ladder (in science, this shape is called a double helix). The sides of the ladder are made of sugar and phosphate, while the rungs are made of the four chemical bases. Each rung is made of two connected bases. Adenine always pairs with thymine, while cytosine always pairs with guanine. Thymine and cytosine are known as the pyrimidines, while adenine and guanine are known as the purines.


RNA is like DNA, but differs in multiple ways. RNA is short for ribonucleic acid. Unlike DNA, RNA has only one strand. Additionally, RNA uses the nucleobase called uracil instead of thymine. Finally, RNA contains the sugar ribose instead of deoxyribose. RNA serves to deliver direct instructions to organelles. Arguably the most important task is to instruct the ribosomes on protein synthesis.


In genetics, the term “gene” is only loosely defined. However, it is most commonly used to refer to any polymer (long, repeating strand) of DNA or RNA. Genes code for the production of different proteins. The different proteins are responsible for physiological differences between living beings. Any variation of a gene is called an allele. Each allele codes for a different trait. A person’s collection of physical traits is called their phenotype. A person’s collection of genetic traits is called their genotype. There are two types of traits: inherited traits, which are directly genetic in nature, and environmental traits, which are the result of external factors. Some traits can be influenced by both the environment and inheritance.


Genes are located on chromosomes, small cell structures that lie within the cell nucleus. While most chromosomes look like the letter ‘X’, circular ones are also known to exist. They are made of tightly coiled pieces of DNA, RNA, and proteins.

Below is a song about DNA (this is a parody of “Grenade” by Bruno Mars)


Muscular System

Muscles are what let you move from place to place. They are what let you stretch your arms. Even simple finger movement cannot be done without muscles. Collectively, the muscles in the body are referred to as the muscular system.

A simplified diagram of the anterior and posterior views of the muscular system.


Role of the Muscular System:

The muscular system allows movement of the body by applying force. There are numerous muscles in your body, so many it would be difficult to memorize them all. However, there are multiple notable muscles with notable functions.

Shoulder Muscles:

Shoulder muscles raise and lower the arms.


The triceps straighten the arms and keep them in place. They are located above (outside) the biceps.


Biceps are muscles that bend the arms. They are located beneath (inside) the triceps.

Neck Muscles:

Neck muscles allow the head to move in a wide variety of directions.

Abdominal Muscles:

Abdominal muscles move the torso.

Thigh Muscles:

Thigh muscles allow movement in the the legs.

Shin Muscles:

Shin muscles allow the feet to move around and side-to-side.

Calf Muscles:

Calf muscles control the heel and toes.

Nervous System

When I talk about the nervous system, I don’t mean there’s an organ system that exists to make you nervous (well technically it is responsible for nervousness, but that’s not the only function). The nervous system is like a computer network for your body. It sends signals all throughout the body to the other systems to control them. Sometimes you (as in your consciousness) can control some systems, sometimes they’re completely autonomous. Be warned, this post may blow your mind. Even though it’s about your mind.

File:TE-Nervous system diagram.svg
A labeled diagram of the nervous system. Note that the auditory, olfactory, visual and gustatory subsystems are not included.

Role of the Nervous System:

The nervous system is arguably the most important body system (perhaps not, as creatures who have been decapitated can survive for astounding periods of time afterwards as long as their other systems are intact, they simply won’t be conscious). The nervous system is responsible for every one of your senses, as well as regulating your bodily functions. You control your body through the nervous system.


Understanding neurons is key to understanding the nervous system. Neurons are highly specialized nerve cells identified by the presence of synapses that connect the membranes of neurons to other neurons. These synapses allow signal transmission between neurons, electrical or chemical. Most neurons also have projections called axons. These projections end in a branching synapses terminal that allows multiple neurons to be connected to a single neuron. Neurons are usually part of bundles called nerves. Nerves run through your body, and their presence allows you to “sense” things you touch. Nerves are also the “control conduits” that the nervous system uses to control your body.

File:Complete neuron cell diagram en.svg
A labeled diagram of a neuron. Many of the parts labeled are found in most other animal cells as well, and are explained in the “Parts of a Cell” post.

The Brain:

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The brain is a very complex organ. It serves numerous functions, including reception and interpretation of sensory signals, rapid calculation, movement, thought, memory, emotion, and more. The main feature of the human brain is the cerebrum or cerebral cortex. It covers the cerebellum and spinal cord. It is divided into four lobes: the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. The frontal lobe is responsible for reward, attention, short-term memory tasks, planning, and motivation in addition to voluntary motor control. The parietal lobe is associated with proprioception (explained later), and the interpretation of the sense of touch. It is also important in language interpretation. The occipital lobe is responsible for the processing of visual information. Finally, the temporal lobe is involved in memory, emotion, and understanding. The cerebellum (Latin for “little brain”), which hangs behind and below the cerebrum, is responsible for precision in motor function, but also plays a part in pain reception and pleasure. Damage to the cerebellum can result in loss of motor precision. Last but not least, the spinal cord is a long, thick bundle of nerves that runs from the brain into and through the thoracic region before splitting into numerous other nerves.


The nervous system also includes several sensory subsystems. Sight (vision), hearing (audition), taste (gustation), smell (olfaction), and touch (somatosensation) are all senses. Contrary to popular belief, these five senses aren’t the only ones. In fact, the human body possesses nine total senses. The remaining four are spatial awareness (proprioception), detection of temperature (thermoception), pain (noiception), and balance (equilibrioception).

Somatosensory System:

Despite including five of the nine human senses, the somatosensory system is relatively simple. It allows a person to feel pain, interpret temperature, maintain balance (the auditory system also plays a role here), and keep a relative sense of the position of other areas of the body (such as the limbs). These functions are achieved by the presence of neural receptors all over the skin.

Visual System:

A diagram of the visual system. The individual parts of the eyes are not labeled (save for the retina)
File:Schematic diagram of the human eye en.svg
A labeled diagram of the human eye.


The visual system is responsible for the sense of sight. It includes the eyes and their parts, along with the neural pathways that connect them to the brain. The eyes receive visual input from the light waves (will be explained in the “Light” post) that are reflected off of objects. While most mammals can only see into certain parts of the light spectrum, snakes can “see” heat via the infrared spectrum, while bees can see into the ultraviolet spectrum. Light first enters the eye through the cornea, which is a transparent covering eye, where it is refracted through the pupil. The pupil is surrounded and controlled by the iris, the colored part of the eye. The light is refracted once again by the pupil, and then passes into the retina, which conveys a recording of the light wave down a neural pathway into the brain. It is interesting to note that the image sent to the brain by the retina is originally upside-down. The occipital lobe corrects the image by flipping it over. The visual system works similarly to a camera, where a light waves are reflected and refracted before being turned into an image.

Auditory System:

File:Blausen 0328 EarAnatomy.png
A labeled diagram of the human ear.

The ears are the primary components of the auditory system. When a sound wave enters the ear, it “bounces” off the various folds of the ear into the tympanic membrane, more commonly known as the ear drum. The sound wave is then received by nerves and transmitted to the temporal lobe of the brain, where it is registered as sound. In addition to hearing, the ear helps perceive balance by the position of fluids inside the inner ear.

Gustatory System:

The gustatory system allows the brain to interpret taste. It consists of the tongue and taste buds. It is important in distinguishing between helpful and harmful food. Sour and bitter tastes usually indicate that a particular substance is harmful, while sweetness, saltiness, and unami (Japaneese for “savory”) are indicators of helpful foods, though overdoses of salt can be harmful. Taste is a form of chemoreception, which is where a sense utilizes the chemical compounds in a substance in order to determine the correct signal to send to the brain.

Olfactory System:

File:Olfactory system.svg
Numbered diagram of the olfactory system: 1: Olfactory Bulb 2: Mitral Cells 3: Bone 4: Nasal Epithelium 5: Glomerulus 6: Olfactory Receptor Cells.

The substances of gases that enter your nose are analyzed by your olfactory system. The analysis of a particular substance is sent to the nasal epithelium, where it is then transmitted from neuroreceptors to the brain and translated into smell.

Below is a parody of Jason Derulo’s “It Girl” about the nervous system.

Integumentary System

Most people think of organs as only referring to your innards. This is not true. Your skin is actually an organ, and its the largest one, too. The skin, along with the sweat glands and nails, make up the integumentary system.

A cross-section of human skin.

Role of the Integumentary System:

The integumentary system serves the role of protecting your body from external harm, dehydration, burns, and infection. It also allows waste to be excreted by perspiration. Finally, the skin acts as a receptor for the sensations of touch and pain. The skin has three primary layers: the epidermis, the dermis, and the hypodermis.


The epidermis is the top layer of the skin. It is keratinized (waterproof). Tiny openings called pores are found in the epidermis that allows perspiratory waste to be excreted. Fingernails are the result of the stiffening of the protein keratin in order to protect sensitive cells.


The dermis is the middle layer of the skin. This is where blood vessels typically end. Integumentary attachments like hair and feathers begin growing here. Additionally, sweat glands can be found here.


The hypodermis, also known as the subcutis, is the innermost and thickest layer of the skin. It specializes in storing fat.

Skeletal System

Have you ever broken a bone? If so, then you probably had to wear a cast or brace for a while afterwards. But why do we need those? Surely we can operate perfectly without a particular bone. However, that is not the case. Bones are necessary for proper movement and structuring the body. Contrary to popular belief, having no bones does not mean you turn into a puddle of goo, but the results would still be rather unpleasant.

A simplified diagram of the anterior view of the skeletal system.
A simplified diagram of the posterior view of the skeletal system.


Role of the Skeletal System:

The skeletal system is very important. It provides structure to the body. At birth, the skeletal system contains roughly 270 bones, but decreases to 206 as certain bones fuse together over time. Inside the bones, red blood cells are produced by the bone marrow and put to work. The skeletal system is divided into two main sections: the axial skeleton and the appendicular skeleton.

Axial Skeleton:

The axial skeleton is comprised of the vertebral column, the ribcage, the sternum and the skull. It protects vital organs like the heart, lungs, spinal cord, and brain. It allows humans to maintain an upright posture. A human can survive with just their axial skeleton, but they would be severely handicapped as a result.

Appendicular Skeleton:

The appendicular skeleton is comprised of the pelvis, the upper limbs and the lower limbs. The appendicular skeleton assists in mobility and the protection of digestive and reproductive organs.

Bone Marrow:

The bone marrow is a flexible tissue inside of long bones. Blood cells are produced in the bone marrow in a process called hematopoiesis. Blood cells come from a stem cell in the bone marrow, which then allows developing blood cells to specialize as a red blood cell (erythrocyte) or one of the many types of white blood cells.

File:Hematopoiesis simple.svg
A diagram showing the possible developments of a blood cell from a stem cell.


Ligaments are fibrous tissues that connect bones to each other. These are not to be confused with tendons.


Tendons are fibrous tissues that connect bones to muscles. They are not to be confused with ligaments.