My Science School

There are two kinds of nuclear reaction, both of which give off huge amounts of energy. Nuclear fusion happens when two nuclei collide and combine to form one larger nucleus. This gives off enormous power. Nuclear fission happens when neutrons bombard the nucleus of an atom, causing the nucleus to split apart.

In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle (such as a proton, neutron, or high energy electron) from outside the atom, collide to produce one or more nuclides that are different from the nuclide(s) that began the process (parent nuclei). Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle and they then separate without changing the nature of any nuclide, the process is simply referred to as a type of nuclear scattering, rather than a nuclear reaction.

In principle, a reaction can involve more than two particles colliding, but because the probability of three or more nuclei to meet at the same time at the same place is much less than for two nuclei, such an event is exceptionally rare for an example very close to a three-body nuclear reaction). The term "nuclear reaction" may refer either to a change in a nuclide induced by collision with another particle, or to a spontaneous change of a nuclide without collision.

Natural nuclear reactions occur in the interaction between cosmic rays and matter, and nuclear reactions can be employed artificially to obtain nuclear energy, at an adjustable rate, on demand. Perhaps the most notable nuclear reactions are the nuclear chain reactions in fissionable materials that produce induced nuclear fission, and the various nuclear fusion reactions of light elements that power the energy production of the Sun and stars.

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Most elements do not change unless a force is applied to them that causes them to join with another element. They are said to be stable. But some elements are not stable. Their nuclei are constantly breaking down, or decaying, as they shed particles in an attempt to become stable. This is radioactivity, and the particles that are given off are known as radiation. Three types of particles are known to be emitted: alpha, beta and gamma rays.

As its name implies, radioactivity is the act of emitting radiation spontaneously. This is done by an atomic nucleus that, for some reason, is unstable; it "wants" to give up some energy in order to shift to a more stable configuration. During the first half of the twentieth century, much of modern physics was devoted to exploring why this happens, with the result that nuclear decay was fairly well understood by 1960. Too many neutrons in a nucleus lead it to emit a negative beta particle, which changes one of the neutrons into a proton. Too many protons in a nucleus lead it to emit a positron (positively charged electron), changing a proton into a neutron. Too much energy leads a nucleus to emit a gamma ray, which discards great energy without changing any of the particles in the nucleus. Too much mass leads a nucleus to emit an alpha particle, discarding four heavy particles (two protons and two neutrons).

Radioactivity is a physical, not a biological, phenomenon. Simply stated, the radioactivity of a sample can be measured by counting how many atoms are spontaneously decaying each second. This can be done with instruments designed to detect the particular type of radiation emitted with each "decay" or disintegration. The actual number of disintegrations per second may be quite large. Scientists have agreed upon common units to use as a form of shorthand. Thus, a curie (abbreviated "Ci" and named after Pierre and Marie Curie, the discoverers of radium (87) is simply a shorthand way of writing "37,000,000,000 disintegrations per second," the rate of disintegration occurring in 1 gram of radium. The more modern International System of Measurements (SI) unit for the same type of measurement is the Becquerel (abbreviated "Bq" and named after Henri Becquerel, the discoverer of radioactivity), which is simply a shorthand for "1 disintegration per second."

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A mass spectrometer is a machine that can measure the mass of atoms and so identify them. Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio of ions. The results are typically presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.

A mass spectrum is a plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical identity or structure of molecules and other chemical compounds.

In a typical MS procedure, a sample, which may be solid, liquid, or gaseous, is ionized, for example by bombarding it with electrons. This may cause some of the sample's molecules to break into charged fragments or simply become charged without fragmenting. These ions are then separated according to their mass-to-charge ratio, for example by accelerating them and subjecting them to an electric or magnetic field: ions of the same mass-to-charge ratio will undergo the same amount of deflection. The ions are detected by a mechanism capable of detecting charged particles, such as an electron multiplier. Results are displayed as spectra of the signal intensity of detected ions as a function of the mass-to-charge ratio. The atoms or molecules in the sample can be identified by correlating known masses (e.g. an entire molecule) to the identified masses or through a characteristic fragmentation pattern.

The atomic number of an element is the number of protons it contains. For example, hydrogen has one proton, so its atomic number is one. Tin has an atomic number of 50 because it has 50 protons in its nucleus.

Atomic number of a chemical element in the periodic system, whereby the elements are arranged in order of increasing number of protons in the nucleus. Accordingly, the number of protons, which is always equal to the number of electrons in the neutral atom, is also the atomic number. An atom of iron has 26 protons in its nucleus; therefore the atomic number of iron is 26. In the symbol representing a particular nuclear or atomic species, the atomic number may be indicated as a left subscript. An atom or a nucleus of iron (chemical symbol Fe), for example, may be written 26Fe.

The atomic number of a chemical element is the number of protons in the nucleus of an atom of the element. It is the charge number of the nucleus since neutrons carry no net electrical charge. The atomic number determines the identity of an element and many of its chemical properties. The modern periodic table is ordered by increasing atomic number.

The atomic number of hydrogen is 1; the atomic number of carbon is 6, and the atomic number of silver is 47: any atom with 47 protons is an atom of silver. Varying the number of neutrons in an element changes its isotopes while changing the numbers of electrons makes it an ion.

The atomic number is also known as the proton number. It may be represented by the capital letter Z. The use of capital letter Z comes from the German word Atomzahl, which means "atomic number." Before the year 1915, the word Zahl (number) was used to describe an element's position on the periodic table.

The reason the atomic number determines the chemical property of an element is that the number of protons also determines the number of electrons in an electrically neutral atom. This, in turn, defines the electron configuration of the atom and the nature of its outermost or valence shell. The behavior of the valence shell determines how readily an atom will form chemical bonds and participate in chemical reactions.

At the time of this writing, elements with atomic numbers 1 through 118 have been identified. Scientists typically talk about discovering new elements with higher atomic numbers. Some researchers believe there may be an "island of stability," where the configuration of protons and neutrons of super heavy atoms will be less susceptible to the quick radioactive decay seen in known heavy elements.

An element is a substance that is made up of only one kind of atom. The periodic table below shows all the elements currently known. However, there are more than 109 different atoms because some elements have more than one isotope.

There are more than 109 different types of atom - one for each element. Differences between the atoms give the elements their different chemical properties. In 2001, there were 115 known elements. However, those above 109 are highly unstable and have been made in only tiny quantities. Scientists are able to make tiny amounts of these new elements in the laboratory. They exist for only a very short time so, whilst they are of scientific interest, they have little practical use in the wider world – at the moment!

Atoms, once thought to be the smallest building blocks of nature, are in fact made of smaller particles. Most often these particles are in balance, and as such the atom is stable and lasts nearly forever. Some atoms are out of balance. This can make them radioactive.

Description: Atoms are made of tiny particles called protons, neutrons and electrons. Protons and neutrons clump together to form a central nucleus. The electrons move in a cloud-like region around the nucleus.

Stable: Most atoms are stable. Their protons, neutrons and electrons balance. Barring outside forces, a stable atom will stay the same indefinitely.

Isotopes: Every atom is a chemical element, like hydrogen, iron or chlorine. Every element has cousins called isotopes. These have a different number of neutrons, but are otherwise the same. Having excess neutrons may make isotopes radioactive.

Radioactive: Some atoms have too many neutrons in the nucleus, which makes them unstable. They’re radioactive, giving off particles until they become stable.

Ions: Atoms with extra or missing electrons are called ions. They have a positive or negative electric charge and are responsible for many chemical reactions.

Antimatter: Every atomic particle has a twin anti-particle, with an opposite electric charge. Antimatter hydrogen atoms have been formed in the laboratory, containing an anti-proton and anti-electron. Antimatter is very rare and fragile.

Each atom has a nucleus containing protons, and all except the hydrogen nucleuses have neutrons as well. Neutrons have no electrical charge, but protons have a positive charge. Moving at high speed around the nucleus are little particles of energy called electrons, which have a negative charge. The number of protons and electrons in an atom is always the same. As opposite charges attract each other, the attraction between the protons and the electrons keeps the electrons around the nucleus, just as the force of gravity keeps the Moon circling around the Earth.

The tiny atomic nucleus is the centre of an atom constituting positively charged particles “protons” and uncharged particles “neutrons.” On the other hand, the extra nucleus part is a much larger region which is composed of a cloud of negatively charged particles called an electron. Electrons revolve around the orbit or centre of the nucleus. The attraction between the protons and electrons holds the structure of an atom together.

Generally, all atoms are composed of these three subatomic particles except hydrogen. Hydrogen is an exception to all atoms as it just contains one proton and one electron but lacks neutrons. The number of protons indicates what element an atom is whereas the number of electrons indicates the type of reactions will happen in an atom.

The atomic nucleus in the structure of the atom is composed of a fixed number of protons and the proton attracts the same number of electrons thereby making an atom electrically neutral. Ions are formed by addition or removal of electrons from an atom.

There is no net charge of an atom. Electrons are the negatively charged particle whereas protons are the positively charged particles. The equal positive charge of the proton and the negative charge of the electron cancel each other. Therefore, the atom has no net charge. In an atom that is neutral, the number of electrons revolving around the nucleus and the number of protons inside the nucleus are equal in number.

The word “atom” comes from an ancient Greek word for a tiny piece of matter too small to be split up. Today we know that even atoms are made up of smaller parts, called subatomic particles. Protons and neutrons are the particles that make up the nucleus of an atom, while electrons can be thought of as circling around the nucleus like orbiting planets. However, these are not the only subatomic particles. Scientists have found hundreds more and are still discovering others by using a machine called a particle accelerator. Quarks, for example, form part of neutrons and protons.

When physicists first collided electrons with protons, they observed that electrons bounced off three small hard cores inside the proton. The cores were then called quarks and it was found to be even smaller particles that make up the proton. Quarks are the smallest particles we have come across in our scientific endeavor. Discovery of quarks meant that protons and neutrons weren’t fundamental anymore.

For more thorough understanding let’s peel apart a piece of matter and discover its constituents by removing each layer one by one. From a bird’s-eye view, matter looks rigid and its properties easily measurable. But even a 6-year-old can deduce that the tenacious pillars of his carefully engineered sandcastle are the sum of billions of microscopic sand grains. What constitutes the sand grain?

Peel another layer and you’ll find a neatly organized structure of atoms. The concept of atoms was first proposed by the Greeks, who believed that objects could be indefinitely split into halves until you were left with a single, indivisible speck of matter. This unimaginably small unit could not be divided further and was, therefore, called an “atom”, derived from the Greek word A-tomos. A for “no” and tomos for “cuttable” or splittable.

 Surprisingly, the theory didn’t fare well. Most of the texts written about elementary constituents were lost and retrieved after multiple centuries. It took almost two millennia for the atom to be was recognized as a real fundamental physical object.

The speculation was finally confirmed in the 1800s when chemist John Dalton conducted a series of ingenious experiments on gases. The average diameter of an atom measured around 50 nano-centimeters – a millionth of a grain of sand. The atom was then the smallest thing known to man.

Matter is the stuff that the universe is made of. The planets, this page, your body and the air that you breathe are all made of matter. Matter itself is made of very small particles called atoms, much too small to be seen with the naked eye or even with many microscopes. The kinds of atom that matter contains and the way in which they are joined together are what determine the kind of matter it is. Matter is a substance that has inertia and occupies physical space. According to modern physics, matter consists of various types of particles, each with mass and size.

The most familiar examples of material particles are the electron, the proton and the neutron. Combinations of these particles form atoms. There are more than 100 different kinds of atoms, each kind constituting a unique chemical element. A combination of atoms forms a molecule. Atoms and/or molecules can join together to form a compound.

Matter can exist in several states, also called phases. The three most common states are known as solid, liquid and gas. A single element or compound of matter might exist in more than one of the three states, depending on the temperature and pressure. Less familiar states of matter include plasma, foam and Bose-Einstein condensate. These states occur under special conditions.

Different kinds of matter can combine to form substances that may not resemble any of the original ingredients. For example, hydrogen (a gaseous element) and oxygen (another gaseous element) combine to form water (a liquid compound at room temperature). The process of such combination is called a chemical reaction. A chemical reaction involves interactions between the electrons of the atoms, but does not affect the nuclei of the atoms.

In some situations, matter is converted into energy by atomic reactions, also known as nuclear reactions. This type of reaction is fundamentally different from the chemical reaction because it involves changes in the nuclei of atoms. The most common example of an atomic reaction is the hydrogen fusion that occurs inside the sun. The immense pressure inside the sun, and inside other stars, forces atoms of hydrogen together to form atoms of helium. In this process, some of the mass is converted to energy according to the formula=

E = mc 2

Where E is the energy in joules, m is the mass in kilograms, and c is the speed of light, which is approximately 2.99792 x 10 8 meters per second in a vacuum.

Some scientists do wear white coats and work with test tubes, but many do most of their work in the world outside. A geologist, gist, for example, may have to clamber a cliff face to obtain samples of rock. Not all scientists wear white coats and work in labs. There are a wide variety of jobs and careers that require knowledge and application of science, from research to business and from regulation to teaching.

The Business Scientist underpins excellent management and business skills with scientific knowledge, supporting evidence-led decision-making within companies and other enterprises. This type of scientist has the scientific and technical knowledge to be credible with colleagues and competitors, as well as confidence in a business environment. They are found in science and technology companies in a wide variety of roles, from R&D or marketing, and to the C-suite itself.

The Developer, or translational, Scientist uses the knowledge generated by others and transforms it into something that society can use. They might be developing products or services, ideas that change behaviour, improvements in health care and medicines, or the application of existing technology in new settings.

They are found in research environments and may be working with Entrepreneur and Business scientists to help bring their ideas to market.

The Entrepreneur Scientist makes innovation happen. Their scientific knowledge and connections are deep enough to be able to see opportunities for innovation – not just in business, but also in the public sector and other sectors of society.

They blend their science knowledge and credibility with people management skills, entrepreneurial flair and a strong understanding of business and finance, to start their own businesses or help grow existing companies.

The Explorer Scientist is someone who, like the crew of the Enterprise, is on a journey of discovery “to boldly go where no one has gone before”. They rarely focus on a specific outcome or impact; rather they want to know the next piece of the jigsaw of scientific understanding and knowledge. They are likely to be found in a university or research centre or in Research & Development (R&D) at an organisation, and are likely to be working alone.

The Regulator Scientist is there to reassure the public that systems and technology are reliable and safe, through monitoring and regulation. They will have a mix of skills and while they may not get involved in things like lab work, they will have a thorough understanding of the science and the processes involved in monitoring its use or application. They are found in regulatory bodies, such as the Food Standards Agency, and in a wide range of testing and measurement services.

The Technician Scientist provides operational scientific services in a wide range of ways. These are the scientists we have come to depend on within the health service, forensic science, food science, health and safety, materials analysis and testing, education and many other areas. Rarely visible, this type of scientist is found in laboratories and other support service environments across a wide variety of sectors.

The Investigator Scientist digs into the unknown observing, mapping, understanding and piecing together in-depth knowledge and data, setting out the landscape for others to translate and develop. They are likely to be found in a university or research centre or in Research & Development (R&D) at an organisation, working in a team and likely in a multi-disciplinary environment.

It is incredible to us now that five hundred years ago it was possible for a person to have a good understanding of every branch of science then known. Today there is so much information available that no one person can be informed about every area of science, and even specialists has difficulty in keeping up with new developments. There is a long established tradition that scientists who have made a new discovery publish a “paper” or article on the subject in scientific journals. People working in the same field can then read this to keep up to date with their subject. Some discoveries are so important or amazing that they reach the general public, through radio, television, books and newspapers.

Until the past decade, scientists, research institutions, and government agencies relied solely on a system of self-regulation based on shared ethical principles and generally accepted research practices to ensure integrity in the research process. Among the very basic principles that guide scientists, as well as many other scholars, are those expressed as respect for the integrity of knowledge, collegiality, honesty, objectivity, and openness. These principles are at work in the fundamental elements of the scientific method, such as formulating a hypothesis, designing an experiment to test the hypothesis, and collecting and interpreting data. In addition, more particular principles characteristic of specific scientific disciplines influence the methods of observation; the acquisition, storage, management, and sharing of data; the communication of scientific knowledge and information; and the training of younger scientists.1 How these principles are applied varies considerably among the several scientific disciplines, different research organizations, and individual investigators.

The basic and particular principles that guide scientific research practices exist primarily in an unwritten code of ethics. Although some have proposed that these principles should be written down and formalized, the principles and traditions of science are, for the most part, conveyed to successive generations of scientists through example, discussion, and informal education. As was pointed out in an early Academy report on responsible conduct of research in the health sciences, “a variety of informal and formal practices and procedures currently exist in the academic research environment to assure and maintain the high quality of research conduct”.

Physicist Richard Feynman invoked the informal approach to communicating the basic principles of science in his 1974 commencement address at the California Institute of Technology:

[There is an] idea that we all hope you have learned in studying science in school—we never explicitly say what this is, but just hope that you catch on by all the examples of scientific investigation. It's a kind of scientific integrity, a principle of scientific thought that corresponds to a kind of utter honesty—a kind of leaning over backwards. For example, if you're doing an experiment, you should report everything that you think might make it invalid—not only what you think is right about it; other causes that could possibly explain your results; and things you thought of that you've eliminated by some other experiment, and how they worked—to make sure the other fellow can tell they have been eliminated.

Details that could throw doubt on your interpretation must be given, if you know them. You must do the best you can—if you know anything at all wrong, or possibly wrong—to explain it. If you make a theory, for example, and advertise it, or put it out, then you must also put down all the facts that disagree with it, as well as those that agree with it. In summary, the idea is to try to give all the information to help others to judge the value of your contribution, not just the information that leads to judgment in one particular direction or another.

Anyone can make a guess, but scientists set about finding out if their ideas are true in an organized way. A hypothesis is a theory — an idea — about why something happens or what makes something work. A scientist will then try to think of a way of testing whether this idea is correct. Often this will mean designing a special experiment.

A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous observations that cannot satisfactorily be explained with the available scientific theories. Even though the words "hypothesis" and "theory" are often used synonymously, a scientific hypothesis is not the same as a scientific theory. A working hypothesis is a provisionally accepted hypothesis proposed for further research, in a process beginning with an educated guess or thought.

A different meaning of the term hypothesis is used in formal logic, to denote the antecedent of a proposition; thus in the proposition "If P, then Q", P denotes the hypothesis (or antecedent); Q can be called a consequent. P is the assumption in a (possibly counterfactual) What If question.

The adjective hypothetical, meaning "having the nature of a hypothesis", or "being assumed to exist as an immediate consequence of a hypothesis", can refer to any of these meanings of the term "hypothesis".

Scientific study relies on collecting and interpreting information (data). Sometimes thousands of different observations or measurements are made. Computers can help to collect and organize the data. For example, an astronomer might want to study the movement of a planet. A computer, attached to a radio telescope, can measure the position of the planet every five minutes for weeks — a task that would be very tedious for a scientist. Having collected the data, the computer can also process it and use it to predict future patterns of movement. Likewise, computers can perform very complex calculations at incredible speed, working out in less than a second something that a century ago might have taken a lifetime to calculate. Other computer programs can draw three-dimensional plans of objects as tiny as an atom or as large as a cathedral. These models can be turned on screen so that all sides can be viewed. Finally, scientists can search for information on the Internet, instead of visiting libraries that may be in other countries.

Science has changed the world. The modern world - full of cars, computers, washing machines, and lawnmowers -simply wouldn't exist without the scientific knowledge that we've gained over the last 200 years. Science has cured diseases, decreased poverty, and allowed us to communicate easily with hundreds of different cultures. The technology that we develop not only helps us in our everyday lives, it also helps scientists increase human knowledge even further.

Science is the pursuit of knowledge about the natural world through systematic observation and experiments. Science is really about the process, not the knowledge itself. It's a process that allows inconsistent humans to learn in consistent, objective ways. Technology is the application of scientifically gained knowledge for practical purpose, whether in our homes, businesses, or in industry. Today we're going to discuss how that technological know-how gained through science allows us to expand our scientific knowledge even further.

It's hard to imagine science without technology. Science is all about collecting data, or in other words, doing experiments. To do an experiment, you need equipment, and even the most basic equipment is technology. Everything from the wheel to a Bunsen burner to a mirror is technology. So all experiments use technology.

But, as technology advances, we are able to do experiments that would have been impossible in the past. We can use spectroscopes (for spectrometers) to shine light through material and see what elements it's made of. We can use gigantic telescopes to see into the far reaches of our universe. We can use MRI scanners to study the inside of the human body and even the brain itself.

We can use a microscope to see the very tiny. And, we can use electronic devices to take measurements that are far more precise than anything that came before us. Technology is at the heart of all modern science experiments.

In the world around us, nothing happens in isolation. One event affects another. The activity of one living thing changes the lives of other organisms. As the natural world is very complicated, it can be difficult to see clearly how and why things are happening. One of the most important factors in designing an experiment is to try to isolate the particular event or substance being studied, so that the results of the experiment are not influenced by other things. For example, to see if a plant needs sunlight to live, you can put it in the dark and watch what happens. But it is important to make sure that the plant still has the same soil, amount of water and temperature as before, so that you can be sure that any changes in the plant are a result of the lack of sunlight.

Many experiments use something called a control. For example, to test a new drug, a hundred people may be given it and their health monitored very carefully. A hundred similar people may be given no drug or a harmless substance and their health monitored just as accurately. They are the control. It is the difference in results between the two groups of people that is important. The control group is designed to show what would have happened to the first group if it had received no drugs. Only then can scientists tell if the drug has had an effect.

An experiment is a type of research method in which you manipulate one or more independent variables and measure their effect on one or more dependent variables. Experimental design means creating a set of procedures to test a hypothesis.

A good experimental design requires a strong understanding of the system you are studying. By first considering the variables and how they are related, you can make predictions that are specific and testable.

How widely and finely you vary your independent variable will determine the level of detail and the external validity of your results. Your decisions about randomization, experimental controls, and independent vs repeated-measures designs will determine the internal validity of your experiment.

Traditionally, science has been divided into natural science, which deals with living things, and physical science, which is concerned with the matter that makes up the universe and how it behaves. Of course, these two fields overlap a great deal. There are also more detailed labels for different areas of scientific study.

Science is a systematic study of the nature and manners of an object and the natural universe that is established around measurement, experiment, observation and formulation of laws. There are four major branches of science; each branch is categorized in different type of subjects that covers different areas of studies such us chemistry, physics, math, astronomy etc. The four major branches of science are, Mathematics and logic, biological science, physical science and social science.

The first branch is mathematics & logic. Mathematics and logic deals with abstract concepts. It goes hand in hand as both are needed in relation to finding out how social sciences and natural sciences work. They are also both needed in forming laws, theories and hypothesis. Even scientist needs this branch of science, as they would not come to a conclusion without any formulation.

Another branch of science is Biological science. This on the other hand deals with the study of living things. Biological science is divided into different sub topics. One of them is Zoology. It is a category under biology that focuses on the study of animal life. The study includes, and are not limited to, evolution, classification of both extinct and the living, structure and habits. Zoology also deals with embryology, which is the study of the animals' development of the embryo, from fertilization to fetus.

Another category is Botany. This category is the scientific study of plants and its life cycle. Including in this study are the plants diseases, reproduction, growth, chemical properties, structure and relationship. Ecology on the other hand deals with the study of the environment and its relationship to living organisms. The last category of biological science is Paleontology. This category of biology deals with the study of prehistoric era. Fossils are not just the main concern in paleontology, it can include any subject that is related with the past, and in other words it can be a study of the whole history of mankind and its life on earth.

Social science is one of the four major branches of science. This on the other hand is the study of the society and man's relationship to it. This study includes Anthropology, which is the study of human behavior and human development that considers cultural, social and physical aspects. Economics is another category under social science; this science studies goods and services, how they are being manufactured, distributed and consumed. Sociology meanwhile is the study of human society; it is more concerned in group activities and urban studies. This study is part of the social science branch, although synonymous when it comes to the name, sociology is more compound since it uses different methods of critical analysis and investigation to come up with a conclusion.

The study of earth's phenomena, its land and features is what Geology is all about. Another category of social science, it can be divided into two parts, which are the physical geography that deals with the land and human geography that deals with the land's inhabitants. Philosophy on the other hand is the pursuit of knowledge by means of moral, intellectual and self-discipline. Studying human behavior according to its principles is what psychology is all about.

Physical science, the last in four major branches of science, has geology, physics, chemistry and astronomy as its categories. Astronomy is the study of the heavenly bodies, like the stars, galaxies, comets and planets, while chemistry is the study of different substances, the changes they undergo and their compositions. It can be divided as well into two, which are the organic and inorganic chemistry. Physics is the study of matter and geology is the study of the physical property and composition of the earth.

Scientists study how and why things happen, or why they are as they are. They can use this knowledge in many different ways: to predict what will happen in certain circumstances, to understand why bodies and machines sometimes go wrong and to try to prevent this or put it right, and to develop inventions that will make a difference to the world. The first scientist was probably a very early human or even human ancestor, who noticed something about the world, began to think about why this might be so and tried to test these ideas.

Aristotle is considered by many to be the first scientist, although the term postdates him by more than two millennia. In Greece in the fourth century BC, he pioneered the techniques of logic, observation, inquiry and demonstration. These would shape Western philosophical and scientific culture through the Middle Ages and the early modern era, and would influence some aspects of the natural sciences even up to the eighteenth century.

Armand Marie Leroi's reappraisal of this colossus, The Lagoon, is one of the most inspired and inspiring I have read. It combines a serious, accessible overview of Aristotle's methods, ideas, mistakes and influence with a contextualizing travelogue that also found expression in Leroi's 2010 BBC television documentary Aristotle’s Lagoon. Leroi's ambitious aim is to return Aristotle to the pantheon of biology's greats, alongside Charles Darwin and Carl Linnaeus. He has achieved it.

Leroi, an evolutionary developmental biologist, visits the Greek island of Lesvos — where Aristotle made observations of natural phenomena and anatomical structures — and puts his own observations in dialogue with those of the philosopher. It was in the island's lagoon of Kolpos Kalloni that Aristotle was struck by the anatomy of fish and molluscs, and started trying to account for the function of their parts. Leroi's vivid descriptions of the elements that inspired Aristotle's biological doctrines — places, colours, smells, marine landscapes and animals, and local lore — enjoin the reader to grasp them viscerally as well as intellectually.

Aristotle's time on Lesvos was only a chapter in a life of discoveries, and Leroi covers those signal achievements with breadth and depth. He details the theoretical and methodological principles governing the functional anatomy of species from pigeons to tortoises, discussed by Aristotle in On the Parts of Animals, as well as the descriptive zoology expounded in his History of Animals. For instance, Leroi explores Aristotle's theory of causation, based on the distinction between material, efficient, formal and final causes. He looks at the philosopher's views on the directedness of natural phenomena and the role played by necessity and hazard. He sketches out the theory of four elements (fire, air, water and earth) as the prime constituents of natural bodies. And he looks at the theory of soul and its relationship to the body — through which Aristotle accounted for aspects of physiology and psychology, from nutrition to rational thinking.