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The Scientific Method!

Introduction

The Scientific Method

The Scientific Method

Welcome to the wikibook about the scientific method. This book is a wiki, and may be freely edited by all users. This book is released under the terms of the GFDL.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License."

Who is this book for?

This book is for any person interested in learning about the scientific method. No background in science or math is required to read and understand this text. Some of the historical chapters will discuss some philosophical topics that might be confusing to people with no familiarity with philosophy, but an attempt will be made to make all sections accessible.

What will this book cover?

This book is going to cover the scientific method, it's history, and it's applications. This book will not attempt to cover all of science, nor will it provide technical instruction in any particular branch of science. This book is mostly historical and philosophical, not technical.

How is this book organized?

This book will be organized into three primary sections. The first section will discuss the history of the scientific method, and the philosophical and scientific advancements that let to it's modern form. The second section will talk about how to apply the method to your inquiries, including a discussion of some common terms and tools. The third and final section will take a look at some specific experiments in various fields of science, to demonstrate how the method has been used to make major breakthroughs.

What are the prerequisites?

There are no specific prerequisites to reading and understanding this book. However, because the subject matter will be focused on history (especially european history) and philosophy, readers may find some benefit to reading books on those subjects first. This is not strictly required, however.

Introduction to Science

The Scientific Method

Science

Modern science is broken into so many divergent branches that it's almost inconceivable to think that they are all related. However, despite the varied subject matter, all scientific disciplines are tied together through their use of a common method, the scientific method. The scientific method is mostly a philosophical exercise that is used to refine human knowledge.

Precepts of the Method

Different disciplines may employ the general scientific method in slightly different ways, but the major precepts are the same:

Verifiability

Any result should be provable. Any person (with the proper training and equipment) must be able to reproduce and verify any scientific result.

Predictability

Any scientific theory should enable us to make predictions of future events. The precision of these predictions is a measure of the strength of the theory.

Wikipedia has related information at Falsifiability

Falsifiability

Falsifiability is an important notion in science and the philosophy of science. For an assertion to be falsifiable it must be logically possible to make an observation or do a physical experiment that would show the assertion to be false. It is important to note that "falsifiable" does not mean false. Some philosophers and scientists, most notably Karl Popper, have asserted that no empirical hypothesis, proposition, or theory can be considered scientific if no observation could be made which might contradict it. Note that if an assertion is falsifiable its negation can be unfalsifiable, and vice-versa. For example, "God does exist" is unfalsifiable, while it's negation "God doesn't exist" is falsifiable. Any scientific theory must have criteria under which it is deemed invalid. Should predictions and verifications fail completely, the theory must be abandoned.

Fairness

Data needs to be analyzed as a whole or as a representative sample. We cannot pick and choose what data to keep and what to discard. Also, we cannot focus our attention on data that proves or disproves a particular hypothesis, we must account for all data even if it invalidates the hypothesis.

Stages of the Method

We will get into more detail in the following chapters, but the basic steps to the scientific method are as follows:

1. Observe a natural phenomena
2. Make a hypothesis about the phenomena
3. Test the hypothesis

Once the hypothesis has been tested, if it is true we can work to find more evidence, or we can find counter-evidence. If the hypothesis is false, we create a new hypothesis and try again.

The important thing to note here is that the scientific process is never-ending. No result is ever considered to be perfect, and at no point do we stop looking at evidence.

Example: Newton and Einstein

Isaac Newton, a brilliant physicist, developed a number of laws of motion and mechanics that we still use today. For many many years the laws of Newton were considered to be absolute fact. Many years later, a physicist known as Albert Einstein noticed that in certain situations Newton's laws were incorrect. Einstein helped to create a new theory, the theory of relativity, that corrected those errors. Even though Einstein was a brilliant scientist, modern physicists are developing new theories because there are some small errors in Einstein's theories. Each new generation of physicists helps to reduce the errors of the previous generations.

The Complete Method

The complete scientific method, as it is generally known is:

1. Define the question
2. Gather data and observations
3. Form hypothesis
4. Perform experiment and collect data
5. Interpret data and draw conclusions

Notice that the first step is to define the question. In other words, we can not look for an answer if we do not know what the question is first. Once we have the question, we need to observe the situation and gather appropriate data. We need to gather all data, not just selectively acquire data to support a particular hypothesis, or to make analysis more simple.

Once we have our data, we can analyze it to determine a hypothesis. In many cases a hypothesis is a mathematical relationship between the data points. However, it is not necessary to use mathematics at any point with the scientific method. Once we have our hypothesis, we need to test it. Testing is a complicated process, and will be the focus of the second section in this book. We collect data from our tests, and attempt to fit that data to our hypothesis. At this point, we need to ask, is the hypothesis right or wrong? Or, if it is not completely wrong nor completely right, we need to ask if this hypothesis is better then the previous hypothesis? If this hypothesis is not quite right, we can modify it and perform the tests again.

Once we have completed tests and verified our hypothesis, we need to draw conclusions from that. What does our hypothesis mean, in the bigger picture? What kinds of relationships between the data can we find? What further problems does this hypothesis cause? What would it take to prove this hypothesis wrong?

Components of the Method

The Scientific Method

Principles

The laws of nature as we understand them and the bases for all empirical sciences. They are the result of postulates (specific laws) that have passed experimental verification resulting in principles that are widely accepted and can be re-verified (using observation or experimentation).

World View (Axioms, Postulates)

The word "axiom" comes from the Greek word αξιωμα (axioma), which means that which is deemed worthy or fit or that which is considered self-evident.

To "postulate" is to assume a theory valid due to be based on an a given set of axioms, resulting on the creation of a new axiom, this is so due to be self evident, "axiom," "postulate," and "assumption" are used interchangeably.

Generally speaking, axioms are all the laws that are generally considered true but largely accepted on faith, they cannot be derived by principles of deduction nor demonstrable by formal proofs—simply because they are starting assumptions, other examples include personal beliefs, political views, and cultural values. An axiom is the basic precondition underlying a theory.

Another thing one should be aware is that some fields of science predate the scientific method, for instance alchemy is now part of chemistry and physics and math was created even before we had numbers, one should have particular attention that in some fields the definitions or nomenclature may be out dated or be so for historical reasons, due to their use since before the definition of scientific method, and that mathematics uses not only the scientific method but also logical deductions, that result in theorems.

Take for instance the use of the word "axiom" in mathematics, this particular field has gone by several changes, especially in the 19th century, but due to historic reasons an "axiom" in mathematics does have a particular meaning.

Euclid's geometry, is based on a system of axioms that look self-evident. So, in physics, Euclid's geometry was used as natural (and the only) choice, the complete theory could be drawn from the axioms, resulting in the whole geometry to be considered to be true and self evident. This changed in the early 19th century, Gauss, Johann Bolyai, and Lobatchewsky, each independently, took a different approach. Beginning to suspect that it was impossible to prove the Parallel Postulate, they set out to develop a self-consistent geometry in which that postulate was false. In this they were successful, thus creating the first non-Euclidean geometry. By 1854, Bernhard Riemann, a student of Gauss, had applied methods of calculus in a ground-breaking study of the intrinsic (self-contained) geometry of all smooth surfaces, and thereby found a different non-Euclidean geometry.

It remained to be proved mathematically that the non-Euclidean geometry was just as self-consistent as Euclidean geometry, and this was first accomplished by Beltrami in 1868. With this, non-Euclidean geometry (both Lobatchewsky and Lobatchewsky) was established on an equal mathematical footing with Euclidean geometry. But this raised issues, "what geometry is true?". Even more, "does the latest question make sense?". All three geometries are based on different system of axioms, all are consistent.

Physics has helped answer these questions. While Euclid's geometry is used on Newtons' mechanics (normal distance), Riemann's geometry became fundamental for Einstein's theory of relativity. Moreover, Lobatchewsky's geometry was used later in quantum mechanics. So, question "Which one of these theories is correct for our physical space?" was answered in the surprising way: "All geometries represents physical space, but on a different scale".

All this influences what to think about axioms. From end of 19th century - beginning 20th century, math didn't appeal to the "self-evidence" of the axioms. It takes the freedom to freely choice axioms. What does, math say, that if the axioms are true, then the theory is followed from the axioms. Correspondence to the real world should be established separately. Axioms doesn't provide any guarantee.

Theory

Consists in a set of statements or principles devised to provide an explanation to a group of facts or phenomena. For instance a mathematical theorem; in the mathematical field we have to be careful on how we apply the definition since a theorem may be considered an axiom in itself, they can be accepted as valid until proved false (due to the infinite nature of numbers, it is common to propose limits to sets to provide validation), and other mathematical theorems my depend or be created over each others assumption of validity.

Hypothesis

The hypothesis, or the model is a way for us to make sense of the data. We try to fit the data into some kind of model, and that model is our hypothesis.

Predictions

A key component to the scientific method is the ability to predict. We can make predictions about something, and then test those predictions to see if they are correct. If the predictions are true, it's likely that the hypothesis is correct.

Theorems

Are not part of the scientific method but may be a cause of some confusion. Most theorems have two components, called the hypotheses and the conclusions. The proof of the theorem is a logical argument demonstrating that the conclusions are a necessary consequence of the hypotheses, in the sense that if the hypotheses are true then the conclusions must also be true, without any further assumptions. The concept of a theorem is therefore fundamentally deductive, in contrast to the notion of a scientific theory, which is empirical.

Verification

The fundamental step of turning an hypothetical relation into a principle, by validating it with real world data. Any verified hypothesis becomes a principle.

Observations

an act or instance of viewing or noting a fact or occurrence for some scientific or other special purpose.

Experiments

Experiments are key to the scientific method. Without experiments, any conclusions are just conjecture. We need to test our observations (to ensure the observations are unbiased and reproducible), we need to test our hypothesis, and then we need to test the predictions we make with our hypothesis.

Setting up of a proper experiment is important, and we will discuss it at length in section 2.

Reasoning

Induction

Deduction

Abduction

History of Scientific Thought

The Scientific Method

had nothing to do with the HISTORY of the scientific method

Empiricism and Inductivism

The Scientific Method

Empiricism

Aristotle

Syllogisms

Inductivism

Islamic Philosophy

Roger Bacon

Galileo

Francis Bacon

Isaac Newton

Rene Descartes' Method

The Scientific Method

Rene Descartes (March 31, 1596 – February 11, 1650) was a highly influential mathematician, scientist and philosopher. Descartes is widely considered to be the 'Father of modern Philosophy'. His most influential work is Meditations on First Philosophy ('First Philosophy being metaphysics). Descartes advocates a method of radical doubt, now labeled Cartesian doubt, whereby the reader, or meditator, begins to doubt all external objects of sense perception and focus only on what the mind 'clearly and distinctly' perceives to be true. Descartes discovers the now well known proposition 'I am, I exist' (Know an the Cogito). Descartes unique idea was to start from axiomatic principles that could not be doubted, and proceed to discover truths and certainty from these axioms. He argued that the mind and rational thought, not experience, is the source of all knowledge. This is why Descartes is know seen as a 'Rationalist'. His method is opposed to a more Newtonian or Aristotelean principle of deriving the axioms from the objects of sense experience.

Hypothetico-Deductivism

The Scientific Method

David Hume

Immanuel Kant

Hans Christian Oersted

William Whewell

Critical Rationalism

The Scientific Method

Criticisms

The Scientific Method

The scientific method is not without it's criticisms,

Determining What to Measure

The Scientific Method

Independent and Dependent Variables

The Scientific Method

Relationships between variables

In any experiment, the object is to garner information about some phenomenon, in order to increase one's knowledge about how it works. In order to design an experiment, it is necessary to know or make an educated guess about cause and effect relationships between what you change in the experiment and what you're measuring. In order to do this, scientists use established theories to come up with a hypothesis before experimenting.

Hypothesis

A hypothesis is a prediction of the effects of changing one variable on another. The variable(s) that you change in the experiment are called independent variables, while those that change because of changes you have made are called dependent variables. A hypothesis says something to the effect of:

Changing independent variable X should do something to dependent variable Y.

For example, suppose you wanted to measure the effects of temperature on the solubility of table sugar (sucrose). Knowing that dissolving sugar doesn't release or absorb much heat, it may seem intuitive to guess that the solubility does not depend on the temperature. Therefore our hypothesis may be:

Increasing or decreasing the temperature of a solution of water does not effect the solubility of sugar.

Isolation of Effects

When determining what independent variables to change in an experiment, it is very important that you isolate the effects of each independent variable. You do not want to change more than one variable at once, for if you do it becomes more difficult to analyze the effects of each change on the dependent variable.

This is why experiments have to be designed very carefully. For example, performing the above tests on tap water may have different results from performing them on spring water, due to differences in salt content. Also, performing them on different days may cause variation due to pressure differences, or performing them with different brands of sugar may yield different results if different companies use different additives.

It is valid to test the effects of each of these things, if one desires, but if one does not have an infinite amount of money to experiment with all of the things that could go wrong (to see what happens if they do), a better alternative is to design the experiment to avoid potential pitfalls such as these.

Corollary to Isolation of Effects

A corollary to this warning is that when designing the experiment, you should choose a set of conditions that maximizes your power to analyze the effects of changes in variables. For example, if you wanted to measure the effects of temperature and of water volume, you should start with a basis (say, 20oC and 4 fluid ounces of water) which is easy to replicate, and then, keeping one of the variables constant, changing the other one. Then, do the opposite. You may end up with an experimental scheme like this one:

Test number      Volume Water (fl. oz.)    Temperature (oC)
   1                  4                       20
   2                  2                       20
   3                  8                       20
   4                  4                       5
   5                  4                       50

Once the data is gathered, you would analyze tests number 1, 4, and 5 to get an idea of the effect of temperature, and tests number 1, 2, and 3 to get an idea of volume effects. You would not analyze all 5 data points at once.

Control of Experimental Conditions

The Scientific Method

Control of Measurement Errors

The Scientific Method

Experimental Design

Perhaps the most important step in controlling experimental error is to design your experiments to produce as little systematic error as possible. In order to do this, it is important to know something about what you are measuring. As an example, suppose that you desired to measure the weight of the oxygen produced in the decomposition of hydrogen peroxide:

You would need to ask yourself: How would you separate the oxygen from the water and unreacted hydrogen peroxide? How will you prevent the oxygen from leaking? Do you want to measure the weight directly, or by calculating it from other values (such as pressure)?

Get into the habit of asking yourself, "what could go wrong with this experiment?" before you start the experiment. Then if you can, design it so that the things that could go wrong are as minor as possible, and then when performing it be as careful as possible to avoid what is left.

Calibration and Accuracy

All measurement instruments need to be calibrated in some way in order to ensure that the values that are read are near the true value of the property being measured. Rulers all are compared to a standard when they are made so that when an inch is marked on the ruler, it is truly an inch.

Many instruments lose their calibration, and hence their accuracy, over time. Therefore it is necessary to recalibrate them. Instruments are generally re-calibrated by measurement of a standard or several, which have well-defined properties. For example, a scale might be calibrated by weighing a 5g weight and adjusting a dial until the reading is 5.000 g. Follow the instrument manual closely for calibration procedures, so that any bias in measurement due to measurement inaccuracy can be mitigated.

Repeatability and Precision

Measurement instruments never will give you an exact answer. For example, if you are measuring the volume of a liquid in a graduated cylinder, it is necessary for you to estimate which of the hash marks on the instrument is the closest to the true volume (or to interpolate between them based on your eyesight). Most computerized measurement devices, such as many modern scales, take multiple measurements and average them to obtain accurate results, but these also have sensitivity limitations.

Manufacturers often report the precision of their instruments. The repeatability of an instrument is a measure of the precision, which is the similarity of successive measurements of an identical quantity to each other. Reproducibility is essentially the ability to, with all other conditions the same (or as close to the same as possible), achieve the same measurement value in an experiment. For example, you may measure the weight of an object with the same scale multiple times. If the reading is significantly different every time, it is possible that the instrument needs to be recalibrated or re-stabilized (for example, by cleaning out dust from the receiver, or making sure the setup is right). If it has been properly calibrated and set up and measurements still vary more than the precision claimed by the manufacturer, the instrument may be broken.

Reproducibility

Another way to control errors in measurement from experiment to experiment is to constantly assess the reproducibility of the measurements. Reproducibility is measured essentially by performing the same measurement multiple times while varying one part of the experiment. For example, if you are measuring the pH of a buffer as part of a process, you may assess the reproducibility of the buffer preparation by preparing the same sample several times, independently of each other, and measuring the pH of each sample. If the variance in the pH measurements is larger than the measurement accuracy (or repeatability) of the instrument, then it is likely that the preparation of the buffer is to blame for this error. Such tests can be performed on many parts of a larger process in order to pinpoint and remedy the largest control difficulties.

Another possible reproducibility test would be measuring the same sample with different pH meters. It is very important to test the compatibility of different measurement instruments before claiming that the results are comparable, and such reproducibility measurements are critical for determining the relationship between two instruments.

Tests for Experimental Validity

The Scientific Method

Data Analysis

The Scientific Method

Experiments in Biology

The Scientific Method

Leeuwenhoek and the Discovery of The Cells

Prior to Leeuwenhoek, there had been little or notion of the idea that microscopic living things could exist. Part of this was due to the fact that most microscopes of the time were not strong enough to see them, though they did exist ^[1]. However, Leeuwenhoek was skillful enough to make such a powerful microscope, and observed protazoans in pond water ^[2].

Not only did he observe them, but he also was able to deduce that they were living because they were motile, and only living things have the ablility to move by their own power. Leeuwenhoek's deductions, and his creative use of technology to explore new avenues, led to the recognition of cells as the building blocks of life, which would have profound influence on biological study and knowledge.

Pasteur and the Death of Spontaneous Generation

Before Louis Pasteur and other scientists proved them wrong, the mainstream belief in science was that living things arose spontaneously from non-living things. This was particularly true of the "cells" which Leuvenhok discovered, because the cells were comparatively simple and therefore it appeared logical that they arose naturally from their environments ^[3]. Another scientist named Lazzaro Spallanzani had previously proven that many bacteria (though not all) are killed by boiling and, if sealed from the air, they will not regrow in the container ^[4]. However, contemporaries refused to deny spontaneous generation, saying that since the organisms spontaneously arose from air, sealing off the container made Lazzaro's hypothesis invalid.

Pasteur put this to rest by designing an experiment. He designed an apparatus, called a swan-neck flask, in which a sterile liquid was exposed to the air but no bacteria could reach it. Bacteria and the dust they lived on were trapped in the swan neck, and sterile air reached the liquid. Since the liquid did not become contaminated with bacteria, Pasteur proved that they did not spontaneously arise from the air. This led to the death of the theory of spontaneous generation and to further studies about how bacteria do reproduce. These studies are important because they have lead to an understanding of how many antibiotics, including Penicillin, work.

Robert Koch and his Four Postulates

Before scientists like Pasteur and Koch arrived on the scientific scene to prove them wrong, many scientists had false beliefs concerning the nature of disease. One of these beliefs was that infectious bacteria spontaneously generated in a human body as a result of diseases ^[5] . While Pasteur proved that spontaneous generation was impossible in the air, Koch devised a scheme by which the cause of diseases in people (and animals) could be experimentally tested.

His scheme revolved around the notion that, if a person is able to prove that one organism is common to all cases of a disease, and if it can be shown that no outside factor causes the disease, then the organism must, indeed, cause the disease. To make it experimentally rigorous, Koch needed a control scheme, so he devised a set of "postulates" to prove that the organism in question actually caused the disease ^[6]:

1. The organism had to be present in any case of the illness in question.
2. It had to be possible to take the organism out of the patient and purify it so that only one species was present. This prevents the possibility that an organism other than the one being observed actually causes the disease.
3. The now-purified organism had to cause the disease when injected into a healthy animal. This prevents the possibility of something before the bacteria causing the disease, and debunks the possibility that the toxins came first and caused formation of the bacteria.
4. As a final check, one must be able to re-isolate the organism from the newly-sick animal.

Koch used this to prove that Bacillus anthracis causes anthrax ^[7], and it has been used to establish the causes of a large number of other bacterial diseases as well.

Fleming and the advent of antibiotics

Franklin, Watson, and Crick: DNA structure

Mendel and his theory of inheritance

Darwin and his theory of evolution and natural selection

1. ↑ Microscopes in Leeuwenhoek's time
2. ↑ Leeuwenhoek's observations
3. ↑ spontaneous generation
4. ↑ Boiling kills microbes
5. ↑ Historical beliefs about diseases
6. ↑ Koch's Postulates
7. ↑ Madigan M; Martinko J (editors). (2005). Brock Biology of Microorganisms, 11th ed., Prentice Hall. ISBN 0-13-144329-1.

Experiments in Chemistry

The Scientific Method

Mendeleev and the Periodic Table

The Periodic Table is an example of bringing order to a large amount of information that may seem chaotic. Before it was developed, trends between similar compounds were more difficult or impossible to visualize. There are a large number of properties which can be roughly predicted from trends in the periodic table including:

1. How the elements react
2. What the elements will react with
3. How big the atoms are
4. How the electrons are organized around the atoms.

There are several others properties that are also predicted well from the table. Mendeleev was not the first to notice the patterns but he was the first to bring an organizational scheme to the scientific community in a way that people would accept his work. In particular, he did several things differently from his predecessors:

1. He chose different patterns on which to base his ordering scheme. Previous attempts at organizing the elements met with some failure because they were based on increasing atomic weight, and when two dissimilar compounds fell in the same column of the table, they went with the order based on weights, not based on properties ^[1].
2. Mendeleev not only switched around molecular weights so that the properties of elements in the same column were similar, he also left spaces for undiscovered compounds when there was no in a reasonable weight range. In this way he was forward-thinking, which left room for later discoveries.^[2]
3. He was able to convince people of the value of his scheme after several of the elements for which he had left "holes" were discovered.

This example shows that science benefits a great deal from the ability to organize information. Organizing information is necessary in order to generalize what is known and to generate new theories from the observed trends, and is a key step in hypothesis generation and testing.

Boyle and his Law

Boyle, back in the 17th century, helped to prove that gasses have weight and that their density depends on how much pressure is applied to them. In particular he discovered Boyle's Law, which roughly says that if you double the amount of pressure applied to a gas (at constant temperature), its volume will be halved ^[3].

He did this by making use of a manometer, which is a U-shaped instrument that measures pressure by the height of a liquid that is displaced. He capped one end and poured some mercury into the other end, thus trapping air in the middle. Then he measured the pressure, and added enough mercury to halve the volume of air present in the tube ^[4]. He then measured the pressure at that instant, and through many measurements, showed that volume and pressure are inversely related.

This example shows that sometimes a scientist must be quite clever to achieve a new discovery. Many groundbreaking experiments, including this one, involved the use of fairly new inventions or apparatuses which cleverly could be used to measure quantities. It is only through measurement that hypotheses can be proved.

Avogadro and the nature of atoms and molecules

Before Avagadro made a keen, unifying observation to the theory of gasses, scientists weren't sure how to usefully define atoms and molecules, and therefore had difficulties measuring the molecular weight of compounds. However, Avagadro was able to remedy this by hypothesizing that any gas occupying the same volume at the same temperature and pressure has the same number of molecules, not the same number of atoms, and that these molecules were made of combined elements ^[5]. Scientists were later able to prove that this is true by using the theory to measure atomic weights more accurately than had been possible before, and then combining them to yield the weights of known molecular compounds.

Avagadro's theory was important because it reconciled a couple of other theories: Dalton's theory that everything is made of atoms, and Gay-Lussac's observation that the volume of gasses in a gas-phase reaction changes in proportion to the molecules of gas consumed or generated ^{[6] [7]}. This type of unification is central to the advancement of science.

Pasteur and Enantiomers of Tartaric Acid

Among his many accomplishments, Pasteur was one of the first people to discover that certain molecules have a property called chirality. A molecule is considered chiral if its mirror image or enantiomer is different from the original molecule. A typical physical analogue to this is a glove: you cannot put the right glove on your left hand because the thumb is the "wrong way" (unless they're specifically designed to fit both, in which case the glove is achiral).

Pasteur's experiment involved separating the enantiomers of tartaric acid from a mixture containing both. Now, enantiomers are not in general easy to separate from each other because they usually have identical physical and chemical properties, but tartaric acid is unusual because it forms crystals which are visibly different from one another in their direction ^[8]. Therefore, Pasteur was able to visually separate the two enantiomers.

Once he separated, he drew upon the work of Jean Biot and shined light through each enantiomer. Biot had previously shown that, due to some unknown physical pheonomenon, some substances rotated light in one direction, some on another direction, and some did not at all. Pasteur hypothesized that this was due to the presence of the asymmetric enantiomers, and when he tested his theory he turned out to be right.

It is now known that many compounds are achiral due to the nature of carbon-carbon bonds. In particular, if a carbon has four different substituents attached to it, that carbon is chiral ^[9] Pasteur's experiment helped in both deducing structures of chiral compounds and in spurring experiments regarding their biological significance.

References

1. ↑ Asimov, Isaac. Asimov's Guide to Science. New York: Basic Books, 1972, 230.
2. ↑ [History of the Periodic Table]
3. ↑ Boyle's Law demo
4. ↑ Description of Boyle's measurement methods
5. ↑ Avagadro's theory
6. ↑ Guy-Lussac's Law
7. ↑ Avagadro's Hypothesis
8. ↑ Pasteur's Experiment
9. ↑ http://www.chemguide.co.uk/basicorg/isomerism/optical.html#top Chiral molecules]

Experiments in Physics

The Scientific Method

Experiments in Psychology

The Scientific Method

Timeline

The Scientific Method

This Timeline of the history of scientific method shows an overview of the cultural inventions that have contributed to the development of the scientific method. For a more detailed account see History of Scientific Thought.

• 2000 BC — First text indexes (various cultures).
• 320 BC — Aristotle, comprehensive documents categorising and subdividing knowledge, dividing knowledge into different areas (physics, poetry, zoology, logic, rhetoric, politics, and biology).
• 200 BC — First cataloged library] (at Alexandria)
• 800 AD — Arguably the scientific method in many of its modern forms is developed in some aspects of early Islamic philosophy, theology and law. In particular the methods of citation, peer review and open inquiry leading to development of consensus.
• 1015 - Alhazen used experimental methods to obtain the results in his book Optics. In particular, he combined observations and rational arguments to show that his intromission theory of vision was scientifically correct, and that the emission theory of vision supported by Ptolemy and Euclid was wrong.
• 1327 — Ockham's razor clearly formulated (by William of Ockham)
• 1403 — Yongle Encyclopedia, the first collaborative encyclopedia
• 1590 — First controlled experiment, (Francis Bacon)
• 1600 — First dedicated laboratory
• 1620 — Novum Organum published, (Francis Bacon)
• 1637 — First Scientific method (René Descartes)
• 1650 — Society of experts (the Royal Society)
• 1650 — Experimental evidence established as the arbiter of truth (the Royal Society)
• 1665 — Repeatability established (Robert Boyle)
• 1665 — Scholarly journals established
• 1675 — Peer review begun
• 1687 — Hypothesis/prediction (Isaac Newton)
• 1710 — The problem of induction identified by David Hume
• 1753 — Description of a controlled experiment using two identical populations with only one variable. (James Lind's A Treatise of the Scurvy)
• 1926 — Randomized design (Ronald Fisher)
• 1934 — Falsifiability as a criterion for evaluating new hypotheses (Karl Popper's The Logic of Scientific Discovery)
• 1937 — Controlled placebo trial
• 1946 — First computer simulation
• 1950 — Double blind experiment
• 1962 — Meta study of scientific method (Thomas Kuhn's The Structure of Scientific Revolutions)

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The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not "Transparent" is called "Opaque".

Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

A section "Entitled XYZ" means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as "Acknowledgements", "Dedications", "Endorsements", or "History".) To "Preserve the Title" of such a section when you modify the Document means that it remains a section "Entitled XYZ" according to this definition.

The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

A. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.

B. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.

C. State on the Title page the name of the publisher of the Modified Version, as the publisher.

D. Preserve all the copyright notices of the Document.

E. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

F. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

G. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.

H. Include an unaltered copy of this License.

I. Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

J. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.

K. For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.

L. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.

M. Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version.

N. Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section.

O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements."

6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

8. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.