Scientific method

 

The element of observation includes the elements of hypothesis development, prediction, and experimental test because all of these elements are typically necessary for observation. Werner Heisenberg in a quote that he attributed to Albert Einstein many years after the fact stated :

Related Topics:
Observation - Werner Heisenberg - Albert Einstein

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:It is quite wrong to try founding a theory on observable magnitudes alone. In reality the very opposite happens. It is the theory which decides what we can observe. You must appreciate that observation is a very complicated process. The phenomenon under observation produces certain events in our measuring apparatus. As a result, further processes take place in the apparatus, which eventually and by complicated paths produce sense impressions and help us to fix the effects in our consciousness. Along this whole path?from the phenomenon to its fixation in our consciousness?we must be able to tell how nature functions, must know the natural laws at least in practical terms, before we can claim to have observed anything at all. Only theory, that is, knowledge of natural laws, enables us to deduce the underlying phenomena from our sense impressions. When we claim that we can observe something new, we ought really to be saying that, although we are about to formulate new natural laws that do not agree with the old ones, we nevertheless assume that the existing laws?covering the whole path from the phenomenon to our consciousness?function in such a way that we can rely upon them and hence speak of ?observation.?

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Also Imre Lakatos and Tom Kuhn had done extensive work on the '"theory laden" character of observation.

Related Topics:
Imre Lakatos - Tom Kuhn

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Each element of scientific method is subject to peer review for possible mistakes. These activities do not describe all that scientists do (see below) but apply mostly to experimental sciences (e.g., physics, chemistry). The elements above are often taught in education1.

Related Topics:
Peer review - See below - Education - 1

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The scientific method is not a recipe. It requires intelligence, imagination, and creativity.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The Keystones of Science project, sponsored by the journal Science, has selected a number of scientific articles from that journal and annotated them, illustrating how different parts of each article embody the science method. Here is one example, showing how a group of scientists disproved a claim about lateral gene transfer in the human genome.

Related Topics:
Science - Lateral gene transfer - Human genome

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

DNA/example

:Each element of scientific method is illustrated by an example from the discovery of the structure of DNA:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:*DNA/characterizations

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:*DNA/hypotheses

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:*DNA/predictions

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:*DNA/experiments

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:The examples are continued in "Evaluations and iterations" with DNA/iterations.

Related Topics:
"Evaluations and iterations" - DNA/iterations

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Characterizations

The scientific method depends upon increasingly more sophisticated characterizations of subjects of the investigation. (The subjects can also be called lists of unsolved problems or the unknowns.) For example, Benjamin Franklin correctly characterized St. Elmo's fire as electrical in nature, but it has taken a long series of experiments and theory to establish this. While seeking the pertinent properties of the subjects, this careful thought may also entail some definitions and observations; the observations often demand careful measurements and/or counting.

Related Topics:
Lists of unsolved problems - Benjamin Franklin - St. Elmo's fire - Electrical - Nature - Observations - Measurements

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The systematic, careful collection of measurements or counts of relevant quantities is often the critical difference between pseudo-sciences, such as alchemy, and a science, such as chemistry. Scientific measurements taken are usually tabulated, graphed, or mapped, and statistical manipulations, such as correlation and regression, performed on them. The measurements might be made in a controlled setting, such as a laboratory, or made on more or less inaccessible or unmanipulatable objects such as stars or human populations. The measurements often require specialized scientific instruments such as thermometers, spectroscopes, or voltmeters, and the progress of a scientific field is usually intimately tied to their invention and development.

Related Topics:
Correlation - Regression

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Measurements demand the use of operational definitions of relevant quantities. That is, a scientific quantity is described or defined by how it is measured, as opposed to some more vague, inexact or "idealized" definition. For example, electrical current, measured in Amperes, may be operationally defined in terms of the mass of silver deposited in a certain time on an electrode in an electrochemical device that is described in some detail. The operational definition of a thing often relies on comparisons with standards: the operational definition of "mass" ultimately relies on the use of an artifact, such as a certain kilogram of platinum kept in a laboratory in France.

Related Topics:
Operational definition - Electrical current

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The scientific definition of a term sometimes differs substantially from their natural language usage. For example, mass and weight are often used interchangeably in common discourse, but have distinct meanings in physics. Scientific quantities are often characterized by their units of measure which can later be described in terms of conventional physical units when communicating the work.

Related Topics:
Natural language - Mass - Weight - Units of measure - Physical unit

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Measurements in scientific work are also usually accompanied by estimates of their uncertainty. The uncertainty is often estimated by making repeated measurements of the desired quantity. Uncertainties may also be calculated by consideration of the uncertainties of the individual underlying quantities that are used. Counts of things, such as the number of people in a nation at a particular time, may also have an uncertainty due to limitations of the method used. Counts may only represent a sample of desired quantities, with an uncertainty that depends upon the sampling method used and the number of samples taken.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

New theories sometimes arise upon realizing that certain terms had not previously been sufficiently clearly defined. For example, Albert Einstein's first paper on relativity begins by defining simultaneity and the means for determining length. These ideas were skipped over by Isaac Newton with, "I do not define time, space, place and motion, as being well known to all." Einstein's paper then demonstrates that they (viz., absolute time and length independent of motion) were approximations. Francis Crick cautions us that when characterizing a subject, however, it can be premature to define something when it remains ill-understood{{fn|Cri94}}. In Crick's study of consciousness, he actually found it easier to study awareness in the visual system, rather than to study Free Will, for example. His cautionary example was the gene; the gene was much more poorly understood before Watson and Crick's pioneering discovery of the structure of DNA; it would have been counterproductive to spend much time on the definition of the gene, before them.

Related Topics:
Albert Einstein's - Relativity - Simultaneity - Length - Isaac Newton - Time - Motion - Francis Crick - Visual system

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• {{anb|Cri94}} Francis Crick (1994), The Astonishing Hypothesis ISBN 0-684-19431-7 p.20

The precession of Mercury

The characterization element can require extended and extensive study, even centuries. It took thousands of years of measurements, from the Chaldean, Indian, Persian, Greek, Arabic and European astronomers, to record the motion of planet Earth. Newton was able to condense these measurements into consequences of his laws of motion. But the perihelion of the planet Mercury's orbit exhibits a precession which is not fully explained by Newton's laws of motion. The observed difference for Mercury's precession, between Newtonian theory and relativistic theory (approximately 42 arc-seconds per century), was one of the things that occurred to Einstein as a possible early test of his theory of General Relativity.

Related Topics:
Chaldea - India - Persia - Greek - Arab - European - Earth - Laws of motion - Perihelion - Mercury - Orbit - General Relativity

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

DNA/characterizations

:The history of the discovery of the structure of DNA is a classic example of the elements of scientific method: in 1950 it was known that genetic inheritance had a mathematical description, starting with the studies of Gregor Mendel. But the mechanism of the gene was unclear. Researchers in Bragg's laboratory at Cambridge University made X-ray diffraction pictures of various molecules, starting with crystals of salt, and proceeding to more complicated substances. Using clues which were painstakingly assembled over the course of decades, beginning with its chemical composition, it was determined that it should be possible to characterize the physical structure of DNA, and the X-ray images would be the vehicle.

Related Topics:
The history of the discovery - DNA - The elements of scientific method - 1950 - Genetic inheritance - Gregor Mendel - Bragg's - Cambridge University - X-ray - Diffraction - Molecule - Crystal - Salt

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Hypotheses development

A hypothesis is a suggested description of the subject.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Normally hypotheses have the form of a mathematical model. Sometimes, but not always, they can also be formulated as existential statements, stating that some particular instance of the phenomenon being studied has some characteristic and causal explanations, which have the general form of universal statements, stating that every instance of the phenomenon has a particular characteristic.

Related Topics:
Mathematical model - Existential statements - Universal statements

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Scientists are free to use whatever they can — their own creativity, ideas from other fields, induction, systematic guessing, Bayesian inference, etc. — to imagine possible explanations for a phenomenon under study. The history of science is filled with stories of scientists claiming a "flash of inspiration", or a hunch, which then motivated them to look for evidence to support or refute their idea. Michael Polanyi made such creativity the centrepiece of his discussion of methodology.

Related Topics:
Induction - Systematic guessing - Bayesian inference - Michael Polanyi

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In general scientists tend to look for theories that are "elegant" or "beautiful". In contrast to the usual English use of these terms, they here refer to a theory in accordance with the known facts, which is nevertheless relatively simple and easy to handle. If a model is mathematically too complicated, it is hard to deduce any prediction Note that 'simplicity' may perceived differently by different individuals and cultures.

Related Topics:
Elegant - Beautiful - Prediction

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

DNA/hypotheses

:Linus Pauling proposed that DNA was a triple helix. Francis Crick and James Watson learned of Pauling's hypothesis, figured out that Pauling was wrong and realized that Pauling would soon realize his mistake. So the race was on to figure out the correct structure. Except that Pauling did not realize at the time that he was in a race!

Related Topics:
Linus Pauling - Francis Crick - James Watson

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Predictions from the hypotheses

Any useful hypothesis will enable predictions, by reasoning including deductive reasoning.

Related Topics:
Prediction - Reasoning - Deductive reasoning

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

It might predict the outcome of an experiment in a laboratory setting or the observation of a phenomenon in nature. The prediction can also be statistical and only talk about probabilities.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

It is essential that the outcome be currently unknown. Only in this case does the eventuation increase the probability that the hypothesis be true. If the outcome is already known, it's called a consequence and should have already been considered while formulating the hypothesis.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

If the predictions are not accessible by observation or experience, the hypothesis is not yet useful for the method, and must wait for others who might come afterward, and perhaps rekindle its line of reasoning. For example, a new technology or theory might make the necessary experiments feasible.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Halley's comet

The classic example was Edmund Halley's prediction of the year of return of Halley's comet which returned after his death.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

General Relativity

Einstein's theory of General Relativity makes several specific predictions about the observable structure of space-time, such as a prediction that light bends in a gravitational field and that the amount of bending depends in a precise way on the strength of that gravitational field. Arthur Eddington's observations made during a 1919 solar eclipse supported General Relativity rather than Newtonian gravitation.

Related Topics:
General Relativity - Space-time - Light - Gravitational field - Arthur Eddington - 1919 - Solar eclipse - Gravitation

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

DNA/predictions

:When Watson and Crick hypothesized that DNA was a double helix, Francis Crick predicted that a X-ray diffraction image of DNA would show an X-shape. Also in their first paper they predicted that the double helix structure that they discovered would prove important in biology writing "It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material."

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Experiments

Once predictions are made, they can be tested by experiments. If test results contradict predictions, then the hypotheses are called into question and explanations may be sought. Sometimes experiments are conducted incorrectly and are at fault. If the results confirm the predictions, then the hypotheses are considered likely to be correct but might still be wrong and are subject to further testing.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Depending on the predictions, the experiments can have different shapes. It could be a classical experiment in a laboratory setting, a double-blind study or an archeological excavation. Even taking a plane from New York to Paris is an experiment which tests the aerodynamical hypotheses used for constructing the plane.

Related Topics:
Double-blind - Excavation - New York - Paris - Aerodynamical

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Scientists assume an attitude of openness and accountability on the part of those conducting an experiment. Detailed recordkeeping is essential, to aid in recording and reporting on the experimental results, and providing evidence of the effectiveness and integrity of the procedure. They will also assist in reproducing the experimental results. This tradition can be seen in the work of Hipparchus (190 BCE - 120 BCE), when determining a value for the precession of the Earth over 2100 years ago, and 1000 years before Al-Batani.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

DNA/experiments

: Before proposing their model Watson and Crick had previously seen x-ray diffraction images by Rosalind Franklin, Maurice Wilkins, and Raymond Gosling. However, they later reported that Franklin initially rebuffed their suggestion that DNA might be a double helix. Franklin had immediately spotted flaws in the initial hypotheses about the structure of DNA by Watson and Crick. The X-shape in X-ray images helped confirm the helical structure of DNA.

Related Topics:
Rosalind Franklin - Maurice Wilkins - Raymond Gosling

~ ~ ~ ~ ~ ~ ~ ~ ~ ~