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Experiment

Experiment

In the scientific method, an experiment is a set of actions and observations, performed to support or falsify a hypothesis or research concerning phenomena. The experiment is a cornerstone in the empirical approach to knowledge. See the list of famous experiments for historically important scientific experiments. The word is derived from the Latin ex- + -periri, "from trying".

An experiment in baking

As a simple example, consider that many bakers have noticed that the amount of "fluffiness" in a loaf of bread seems to be related to how much humidity there is in the air when the dough is being made. This can be formalized as the hypothesis: "all other things being considered equal, the greater the humidity, the fluffier the bread". Whilst this hypothesis might arise naturally from baking many loaves over time, an experiment to determine whether this is really true would be to carefully prepare bread dough, as identically as possible, on two types of days: days when the humidity is high, and days when the humidity is low. If the hypothesis is true, then the bread prepared on the high humidity days should be fluffier. Several features of this experiment hold in general for all experiments:
- We must try to make all other conditions of the process as similar as possible between the trials. For example, the amounts of flour and water added, the temperature of the butter, and the amount of kneading all may have an effect on the fluffiness; so the experiment should explicitly attempt to control the other variables which could have an effect on the outcome. This gives us some confidence in the statement "all other things being equal,...".
- Although "fluffiness" may seem to be an easily understood idea, one baker's idea of "fluffy bread" may be different than another baker's. The experiment must be based on objective quantities - for example "fluffiness is measured as the total volume of the loaf of bread from one pound of flour". This idea, coupled with the exactness of the description of how the experiment is to be performed, is sometimes called the operational aspect of the experiment; the idea that all actions, quantities, and observations can be agreed upon by reasonable people.
- Noting that once, on a humid day, one baked a fluffy loaf is not enough. The experiment should be repeatable; given that one performs the experiment exactly as described, one should expect to see the same results, no matter who performs the experiment or how many times it is performed. :Repeatability of an experiment helps to eliminate various types of experimental errors - one may think that one has accurately described all of the relevant techniques and measurements in an experiment, but certain other effects (such as the brand of the flour, trace impurities in the water used in the dough, etc.) may actually be contributing to the observed effects. In the scientific method, someone may claim that they have performed an experiment with a particular result, and thereby supported a particular hypothesis. However, until other scientists have performed the same experiment in the same way and gotten the same results, the experiment is usually not considered as a "proven" result (see cold fusion for a recent example).
- Finally, even though one has baked bread a hundred times, occasionally a loaf will completely fail "because the kitchen gods are unhappy". It is important to realize that some hypotheses cannot be tested experimentally - since we cannot make a measurement which will tell us whether or not the "kitchen gods" are "happy", we cannot perform an experiment which either proves or disproves the hypothesis "the best bread happens when the kitchen gods are happy".

Design of experiments

Design of experiments attempts to balance the requirements and limitations of the field of science in which one works so that the experiment can provide the best conclusion about the hypothesis being tested. In some sciences, such as physics and chemistry, it is relatively easy to meet the requirements that all measurements be made objectively, and that all conditions can be kept controlled across experimental trials. On the other hand, in other cases such as biology, and medicine, it is often hard to ensure that the conditions of an experiment are performed consistently; and in the social sciences, it may even be difficult to determine a method for measuring the outcomes of an experiment in an objective manner. For this reason, sciences such as physics are often referred to as "hard sciences", while others such as sociology are referred to as "soft sciences"; in an attempt to capture the idea that objective measurements are often far easier in the former, and far more difficult in the latter. In addition, in the soft sciences, the requirement for a "controlled situation" may actually work against the utility of the hypothesis in a more general situation. When the desire is to test a hypothesis that works "in general", an experiment may have a great deal of internal validity, in the sense that it is valid in a highly controlled situation, while at the same time lack external validity when the results of the experiment are applied to a real world situation. One of the reasons why this may happen is because of the Hawthorne effect. As a result of these considerations, experimental design in the "hard" sciences tends to focus on the elimination of extraneous effects (type of flour, impurities in the water); while experimental design in the "soft" sciences focuses more on the problems of external validity, often through the use of statistical methods. Occasionally events occur naturally from which scientific evidence can be drawn, which is the basis for natural experiments. In such cases the problem of the scientist is to evaluate the natural "design".

Controlled experiments

:Main article: Control experiment Many hypotheses in sciences such as physics can establish causality by noting that, until some phenomenon occurs, nothing happens; then when the phenomenon occurs, a second phenomenon is observed. But often in science, this situation is difficult to obtain. For example, in the old joke, someone claims that they are snapping their fingers "to keep the tigers away"; and justifies this behavior by saying "see - its working!" While this "experiment" does not falsify the hypothesis "snapping fingers keeps the tigers away", it does not really support the hypothesis - not snapping your fingers keeps the tigers away as well. To demonstrate a cause and effect hypothesis, an experiment must often show that, for example, a phenomenon occurs after a certain treatment is given to a subject, and that the phenomenon does not occur in the absence of the treatment. (See Baconian method.) Baconian method A controlled experiment generally compares the results obtained from an experimental sample against a control sample, which is practically identical to the experimental sample except for the one aspect whose effect is being tested. In many laboratory experiments it is good practice to have several replicate samples for the test being performed and have both a positive control and a negative control. The results from replicate samples can often be averaged, or if one of the replicates is obviously inconsistent with the results from the other samples, it can be discarded as being the result of an experimental error (some step of the test procedure may have been mistakenly omitted for that sample). Most often, tests are done in duplicate or triplicate. A positive control is a procedure that is very similar to the actual experimental test but which is known from previous experience to give a positive result. A negative control is known to give a negative result. The positive control confirms that the basic conditions of the experiment were able to produce a positive result, even if none of the actual experimental samples produce a positive result. The negative control demonstrates the base-line result obtained when a test does not produce a measurable positive result; often the value of the negative control is treated as a "background" value to be subtracted from the test sample results. Sometimes the positive control takes the form of a standard curve. An example that is often used in teaching laboratories is a controlled protein assay. Students might be given a fluid sample containing an unknown (to the student) amount of protein. It is their job to correctly perform a controlled experiment in which they determine the concentration of protein in fluid sample (usually called the "unknown sample"). The teaching lab would be equipped with a protein standard solution with a known protein concentration. Students could make several positive control samples containing various dilutions of the protein standard. Negative control samples would contain all of the reagents for the protein assay but no protein. In this example, all samples are performed in duplicate. The assay is a colorimetric assay in which a spectrophotometer can measure the amount of protein in samples by detecting a colored complex formed by the interaction of protein molecules and molecules of an added dye. In the illustration, the results for the diluted test samples can be compared to the results of the standard curve (the blue line in the illustration) in order to determine an estimate of the amount of protein in the unknown sample. Controlled experiments can be performed when it is difficult to exactly control all the conditions in an experiment. In this case, the experiment begins by creating two or more sample groups that are probabilistically equivalent, which means that measurements of traits should be similar among the groups and that the groups should respond in the same manner if given the same treatment. This equivalency is determined by statistical methods that take into account the amount of variation between individuals and the number of individuals in each group. In fields such as microbiology and chemistry, where there is very little variation between individuals and the group size is easily in the millions, these statistical methods are often bypassed and simply splitting a solution into equal parts is assumed to produce identical sample groups. Once equivalent groups have been formed, the experimenter tries to treat them identically except for the one variable that he or she wishes to isolate. Human experimentation requires special safeguards against outside variables such as the placebo effect. Such experiments are generally double blind, meaning that neither the volunteer nor the researcher knows which individuals are in the control group or the experimental group until after all of the data has been collected. This ensures that any effects on the volunteer are due to the treatment itself and are not a response to the knowledge that he is being treated. In human experiments, a subject (person) may be given a stimulus to which he or she should respond. The goal of the experiment is to measure the response to a given stimulus. (Example???)

Natural experiments

Sometimes controlled experiments are prohibitively difficult, so researchers resort to natural experiments. Natural experiments take advantage of predictable natural changes in simple systems to measure the effect of that change on some phenomenon. Much of astronomy relies on experiments of this type. It is clearly impractical, when trying to prove the hypothesis "suns are collapsed clouds of hydrogen", to start out with a giant cloud of hydrogen, and then perform the experiment of waiting a few billion years for it to form a sun. However, by observing various clouds of hydrogen in various states of collapse, and other implications of the hypothesis (for example, the presence of various spectral emissions from the light of stars), we can collect the experimental data we require to support the hypothesis. An early example of this type of experiment was the first verification in the 1600s that light does not travel from place to place instantaneously, but instead has a measurable speed. Observation of the appearance of the moons of Jupiter were slightly delayed when Jupiter was farther from Earth, as opposed to when Jupiter was closer to Earth; and this phenomenon was used to demonstrate that the difference in the time of appearance of the moons was consistent with a measurable speed of light.

Quasi-experiments

Quasi-experiments are very much like controlled experiments except that they lack probabilistic equivalency between groups. These types of experiments often arise in the area of medicine where, for ethical reasons, it is not possible to create a truly controlled group. For example, one would not want to deny all forms of treatment for a life-threatening disease from one group of patients to evaluate the effectiveness of another treatment on a different group of patients. Researchers compensate for this with complicated statistical methods. See also quasi-empirical methods.

Examples

- MTT assay
- Colony Formation Assay
- Ames Test
- western blot

Quotes

: "We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." — Hannes Alfven : "Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality." — Nikola Tesla

External links

- [http://trochim.human.cornell.edu/kb/index.htm] Trochim, William M. The Research Methods Knowledge Base, 2nd Edition. (version current as of January 15, 2005).
- [http://www.verrueckte-experimente.de/index_e.html Description of weird experiments (with film clips)]

Literature

The Character of Physical Law, by Richard P. Feynman Category:Research
- ja:実験 simple:Experiment

Observation

:For the railroad use of the term observation, see observation car. ---- Observation in its most basic version means watching something and taking note of anything it does - although vision is the most often used, all the senses can be used to observe. For instance, you might observe a bird flying by watching it closely with binoculars. Direct observations form the foundations of all natural sciences. Some disciplines, such as biology and astronomy, have their historical basis in observations by amateurs - the participation of hobbyists is explained by the fact that there is pleasure in observation.

The role of Observation in the Scientific Method

The scientific method includes the following steps: # 'observe' a phenomenon, #'Hypothesize' an explanation for the phenomenon, #'predict' a logical consequence of the guess, #'test' the prediction, and #'review' for any mistakes. Observation plays a role in the first and fourth steps in the above list. Reliance is placed upon the five physical senses: visual perception, hearing (sense), taste, feeling, and olfaction, and upon measurement techniques. It is therefore understood that there are always certain limitations in making observations.

Example - The Big Bang

In cosmology, the original observation was that we seem to live in a firmament. The sun seemed to rise and set, travelling on a huge transparent bowl which was set around our world. Various paradigms which explained our world, came and went, but the universe seemed static. Even Einstein believed this.

Observation: Hubble's redshift

In the 1920s Edwin Hubble of Mount Wilson observatory [http://www.mtwilson.edu/his/art/g1a4.htm], observed that the galaxies, on the whole, were moving away from each other. Thus we live in an 'expanding universe'. The speed of expansion was apparently constant (Hubble's 'constant'), as evidenced by light from the galaxies, which was doppler-shifted in color toward the red side of the spectrum. Einstein correspondingly modified his field equation. See Cosmological constant

Hypothesis about the abundance of the elements

If the universe is expanding, then it must have been much smaller and therefore hotter and denser in the past. George Gamow hypothesized that the abundance of the elements in the Periodic Table of the Elements, might be accounted for by nuclear reactions in a hot dense universe. He was disputed by Fred Hoyle, who invented the term 'Big Bang' to disparage it. Fermi and others noted that this process would have stopped after only the light elements were created, and thus did not account for the abundance of heavier elements. Gamow's prediction: One consequence of this hypothesis was a 5–10 kelvin black body radiation temperature for the universe, after it cooled during the expansion.

Observation: the microwave background

In 1965, Arno A. Penzias and Robert W. Wilson announced that microwave radiation was surrounding us in all directions, at a level which was of the order of magnitude predicted by Gamow. Penzias and Wilson got the Nobel Prize for this discovery.

Big Bang Hypothesis now corroborated

After this piece of evidence, Gamow's hypothesis was now more likely. The age of the universe is currently estimated to be 13.7 billion years after the Big Bang.

Current observations

More refined measurements, such as those from the COBE satellite, are best fit by radiation from a pure 2.7 kelvin black body.

Future observations

It is, of course, entirely possible that observations made in the future may enable a different understanding. People of the future, looking back on the Big Bang theory may, perhaps, regard it with as much derision as the people of today regard the apparent geocentric universe of previous observations. All that is possible is to keep looking at the evidence as it comes in. Reference: J.A. Peacock, A.F. Heavens, A.T. Davies (eds.), 1989. Physics of the Early Universe. Proceedings of the 36th Scottish Universities Summer School in Physics (SUSSP). ISBN 0905945190.

The role of Observation in Philosophy

"Observe always that everything is the result of a change, and get used to thinking that there is nothing Nature loves so well as to change existing forms and to make new ones like them." Meditations. iv. 36. -Marcus Aurelius Observation in philosophical terms is the process of filtering sensory information through the thought process. Input is received via hearing, sight, smell, taste, or touch and then analyzed through either rational or irrational thought. You see a man beat his wife; you observe that such an action is either good or bad. Deductions about what behaviors are good or bad may be based on preferences about building relationships, or study of the consequences resulting from the observed behavior. With the passage of time, impressions stored in the consciousness about many related observations, together with the resulting relationships and consequences, permit the individual to build a construct about the moral implications of behavior. The defining characteristic of observation is that it involves drawing conclusions, as well as building personal views about how to handle similar situations in the future, rather than simply registering that something has happened. Observing is part of the process of developing a morality.

Hobbies that involve observation

Hobbies that involve observation depend for their interest on items being observed. A knowledge of these items and their habitats will develop over time in the observer, who may draw upon the experiences of others as conveyed in books or websites or by word of mouth. Most such hobbies involve classification of the items seen, with the precision and reliability of such classifications generally increasing over time. Depending on the geographic dispersal of the creatures or things being observed, pursuit of the hobby might well require or entice travel. When spotting natural creatures, an understanding of their migration patterns may be essential. Specific creatures may only be visible in particular places at certain times of the year. The creatures that can be observed include humans, e.g. from a sidewalk café. This may be especially interesting in an exotic country, or at a place where exotic people pass. Also one may like to look at sexually attractive people. There are parallels in those hobbies relating to man-made items. International political events may sometimes generate a gathering of VIP aircraft, and an international football match may cause a sudden influx of charter airliners to the region where the match is played. There is likely to be a social aspect to such hobbies, since fellow enthusiasts will normally alert a hobbyist to forthcoming (or even current) opportunities to witness unusual items within the scope of the shared pastime. New technologies such as mobile telephones and the Internet have clearly increased the opportunities for passing such information between fellow enthusiasts when it is timely.

Hypothesis

A hypothesis (foundation from ancient Greek hupothesis where hupo = under and thesis = placing) is a proposed explanation for a phenomenon. A scientific hypothesis must be testable and based on previous observations or extensions of scientific theories.

Usage

In early usage, a hypothesis was usually a clever idea or convenient mathematical approach that simplified cumbersome calculations; it did not necessarily have any real meaning. A famous example of the older sense is the warning which Cardinal Bellarmine issued to Galileo, that he must not treat the motion of the Earth as a reality, but merely as a hypothesis. In common usage at present, a hypothesis is a provisional idea whose merit is to be evaluated. A hypothesis requires more work by the researcher in order to either confirm or disprove it. In the hypothetico-deductive method, a hypothesis should be falsifiable, meaning that it is possible that it be shown false, usually by observation. Note that, if confirmed, the hypothesis is not necessarily proven, but remains provisional. The term hypothesis was misused in the Riemann hypothesis, which should be properly called a conjecture. As an example, someone who enters a new country and observes only white sheep, might form the hypothesis that all sheep in that country are white. It can be considered a hypothesis, as it is falsifiable. It can be falsified by observing a single black sheep. Provided that the experimental uncertainties are small (for example that it is a sheep, instead of a goat) and that the experimenter has correctly interpreted the statement of the hypothesis (for example, does the meaning of "sheep" include rams?), the hypothesis is falsified.

Types of hypotheses

Propositions

Propositions follow a causal order ("A causes B")

Empirical generalizations

Empirical generalizations are based on observed regularities, but they don't stipulate what is the cause and effect themselves, only stating that 'A is related to B'.

Quotes

- "Hypotheses non fingo" : "I feign no hypotheses" -- Isaac Newton
- "... a hypothesis is a statement whose truth is temporarily assumed, whose meaning is beyond all doubt. ..." -- Albert Einstein

Notes

Isaac Newton, Principia Mathematica. A New Translation by I. Bernard Cohen and Anne Whitman, translators. University of California Press 1999 ISBN 0-520-08817-4 Letter to Eduard Study from Albert Einstein, September 25,1918 Collected Papers of Albert Einstein, J.J. Stachel and Robert Schulmann, eds. Princeton University Press 1987

External links

- [http://www.nuevoweb.com/tutorial/glossary.html Research and Evaluation Glossary] Category:Scientific method th:สมมุติฐาน

Research

: For the suburb of Melbourne, Australia, see Research, Victoria. Research is an active, diligent, and systematic process of inquiry in order to discover, interpret and/or revise facts. This intellectual investigation should produce a greater understanding of events, behaviors, or theories, or to make practical applications with the help of such facts, laws, or theories. The term research is also used to describe a collection of information about a particular subject. The word research derives from the Middle French (see French language) and the literal meaning is "to investigate thoroughly".

Basic and applied research

Research is best described as a "sack-sandwiching" process; it is the foundation of the scientific method. Generally, one can distinguish between basic research and applied research.

Basic research

Basic research (also called fundamental or pure research) has as its primary objective the advancement of knowledge and the theoretical understanding of the relations among variables (see statistics). It is exploratory and often driven by the researcher’s curiosity, interest or hunch. It is conducted without a practical end in mind although it can have unexpected results that point to practical applications. The terms “basic” or “fundamental” research indicate that, through theory generation, basic research provides the foundation for further, often applied research. Because there is no guarantee of short-term practical gain, researchers often find it difficult to obtain funding for basic research. Basic research asks questions such as:
- Does string theory provide physics with a grand unification theory?
- Which aspects of genomes explain organismal complexity?
- How can computational methods be efficiently applied to larger and larger molecular systems?

Applied research

Applied research is done to solve specific, practical questions; its primary aim is not to gain knowledge for its own sake. It can be exploratory but often it is descriptive. It is almost always done on the basis of basic research. Often the research is carried out by academic or industrial institutions. More often an academic instituion such as a university will have a specific applied research programme funded by an industrial partner. Common areas of applied research include electronics, informatics, computer science, process engineering and applied science. Applied research asks questions such as:
- How can Canada's wheat crops be protected from grasshoppers?
- What is the most efficient and effective vaccine against influenza?
- How can communication among workers in large companies be improved?
- How can the Great Lakes be protected against the effects of greenhouse gas? There are many instances when the distinction between basic and applied research is not clear. It is not unusual for researchers to present their project in such a light as to "slot" it into either applied or basic research, depending on the requirements of the funding sources. The question of genetic codes is a good example. Unraveling it for the sake of knowledge alone would be basic research – but what, for example, if knowledge of it also has the benefit of making it possible to alter the code so as to make a plant commercially viable? Some say that the difference between basic and applied research lies in the time span between research and reasonably foreseeable practical applications. Thomas Kuhn, in his book The Structure of Scientific Revolutions, traces an interesting history and analysis of the enterprise of research.

Research methods

The scope of the research process is to produce some new knowledge. This, in principle, can take three main forms:
- Exploratory research: a new problem can be structured and identified.
- Constructive research: a (new) solution to a problem can be developed.
- Empirical research: empirical evidence on the feasibility of an existing solution to a problem can be provided. Research methods used by scholars:
- action research
- experiments
- case study
- participant observation
- experience and intuition
- interviews
- surveys
- statistical data analysis
- mathematical models and simulations
- textual analysis
- classification
- map making
- semiotics
- physical traces analysis

Research process

Generally, research is understood to follow a certain structural process. Though step order may vary depending on the subject matter and researcher, the following steps are usually part of most formal research, both basic and applied:
- Formation of the topic
- hypothesis
- conceptual definitions
- operational definitions
- Gathering of data
- Analysis of data
- Conclusion, revising of hypothesis A common misunderstanding is that by this method a hypothesis can be proven. Instead, by these methods no hypothesis can be proven, rather a hypothesis may only be disproven. A hypothesis can survive several rounds of scientific testing and be widely thought of as true (or better, predictive), but this is not the same as it having been proven. It would be better to say that the hypothesis has yet to be disproven. A useful hypothesis allows prediction and within the accuracy of observation of the time, the prediction will be verified. As the accuracy of observation improves with time, the hypothesis may no longer provide an accurate prediction. In this case a new hypothesis will arise to challenge the old and to the extent that the new hypothesis makes more accurate predictions than the old, will supplant it.

Maxim

It is sometimes said that "Copying from one source is plagiarism, copying from several sources is research".

Research funding

Main article: Research funding Most funding for scientific research comes from two major sources, corporations (through research and development departments) and government (primarily through universities and in some cases through military contractors). Many senior researchers (such as group leaders) spend more than a trivial amount of their time applying for grants for research funds. These grants are necessary not only for researchers to carry out their research but as a source of merit. Some faculty positions require that the holder has received grants from certain institutions, such as the US National Institutes of Health (NIH). Government-sponsored grants (e.g. from the NIH, the National Health Service in Britain or any of the European research councils) generally have a high status.

External links

- [http://education.guardian.co.uk/higher/research/story/0,9865,1485743,00.html "Britain a leader in making research available on web"] (Richard Wray, The Guardian, May 17, 2005)
- [http://www.phdcentral.com PhD Central - Open Source Network to Suggest or Find a Thesis Topic] ja:研究

Phenomena

phenomenon.

List of famous experiments

The following is a list of historically important scientific experiments and observations. See also: timeline of scientific experiments, list of famous discoveries, thought experiment.

Astronomy

- Eratosthenes measures the earth's circumference (240 BC)
- Galileo Galilei uses a telescope to observe that the moons of Jupiter appear to circle Jupiter. This evidence supports the heliocentric model, and weakens the geocentric model of the cosmos (1609)
- Arno Penzias and Robert Wilson detect the cosmic microwave background radiation, giving support to the theory of the Big Bang (1964)

Biology

- Anton van Leeuwenhoek discovers microorganisms
- Robert Hooke, using a microscope, observes cells (1665)
- Edward Jenner tests the first vaccine (1796)
- Gregor Mendel's experiments with the garden pea lead him to surmise many of the fundamental laws of genetics (dominant vs recessive genes, the 1-2-1 ratio, see Mendelian inheritance) (1856-1863)
- Louis Pasteur uses S-shaped flasks to prevent spores from contaminating broth. Disproves the theory of Spontaneous generation (also known as abiogenesis). (1861) A continuation of the rancid meat experiment done by Francesco Redi
- Frederick Griffith demonstrates (Griffith's experiment) that living cells can be transformed via a transforming principle, later discovered to be DNA (1928)
- Karl von Frisch decodes the "dance" honeybees use to communicate the location of flowers (1940)
- George Wells Beadle and Edward Lawrie Tatum prove the "one gene, one enzyme" hypothesis using induced mutations in bread mold, Neurospora crassa (1941)
- Luria-Delbruck experiment demonstrates that in bacteria, beneficial mutations arise in the absence of selection, rather than being a response to selection. (1943)
- Barbara McClintock breeds maize plants for color, which leads to the discovery of transposable elements or jumping genes. (1944)
- Hershey-Chase experiment uses bacteriophage to prove that DNA is the hereditary material (1952)
- Miller-Urey experiment demonstrates that organic compounds can arise spontaneously from inorganic ones (1953)
- Meselson-Stahl experiment proves that DNA replication is semiconservative (1958)
- Crick, Brenner et al. experiment (1961)
- Nirenberg and Matthaei experiment (1961)
- Nirenberg and Leder experiment (1964)

Chemistry

- Blaise Pascal caries a barometer up a church tower and a mountain to determine that atmospheric pressure is due to a column of air (1648).
- Robert Boyle uses an air pump to determine the inverse relationship between the pressure and volume of a gas. This relationship came to be known as Boyle's law (1660-1662).
- Joseph Priestley suspends a bowl of water above a beer vat at a brewery and synthesizes carbonated water (1767).
- Antoine Lavoisier determines that oxygen combines with materials upon combustion, thus disproving phlogiston theory (1783).
- Antoine Lavoisier determines that chemical reactions in a closed container do not alter total mass. From these observations he establishes the law of conservation of mass (1789).
- Benjamin Thompson, Count Rumford demonstrates that the heat developed by the friction of boring cannon is nearly inexhaustible. This result was presented in opposition to caloric theory (1798).
- Humphry Davy uses electrolysis to isolate elemental potassium, sodium, calcium, strontium, barium, magnesium, and chlorine (1807-1810).
- Joseph Louis Gay-Lussac studies reactions among gases and determines that their volumes combine chemically in simple integer ratios (1809).
- Robert Brown studies very small partices in water under the microscope and observes Brownian motion which was later named in his honor (1827).
- Friedrich Wöhler synthesizes the organic compound urea using inorganic reactants, disproving the application of vitalism to chemical processes (1828).
- Thomas Graham measures the rates of effusion for different gases and establishes Graham's law of effusion and diffusion (1833).
- Julius Robert von Mayer and James Prescott Joule measure the heat generated by mechanical work. This establishes the principle of conservation of energy and the kinetic theory of heat (1842-1843).
- Louis Pasteur separates a racemic mixture of two enantiomers by sorting individual crystals, and demonstrates their impact on the polarization of light (1849).
- Anders Jonas Ångström observes the presence of hydrogen and other elements in the spectrum of the sun (1862).
- Dmitri Mendeleev observes the periodic nature of physical and chemical properties of the elements and formulates the periodic table (1869).
- François-Marie Raoult demonstrates that the decrease in the vapor pressure and freezing point of liquids caused by the addition of solutes is proportional to the number of solute molecules present. This establishes the concept of colligative properties (1878).
- Henri Louis Le Chatelier performs several experiments to disturb a chemical equilibrium before formulating Le Chatelier's Principle (1884).
- Svante Arrhenius studies the conductivity of salt solutions and determines that salts dissociate into ions in water. (1884)
- Svante Arrhenius determines the impact of temperature on reaction rates and formulates the concept of activation energy. (1889)
- William Ramsay and Lord Rayleigh (John Strutt) isolate the noble gases (1894-1898).
- Frederick Soddy and William Ramsay observe the production of helium (from alpha particles during radioactive decay (1903).
- Otto Hahn and Fritz Strassmann observe nuclear fission (1938).
- Glenn Theodore Seaborg creates and isolates five transuranium elements. He reorganizes the periodic table to its current form. (1941-1950).
- Neil Bartlett mixes xenon and fluorine leading to the first synthesis of a noble gas compound, xenon tetrafluoride (1962).
- Harold Kroto, James Heath, Sean O'Brien, Robert Curl and Richard Smalley isolate buckyballs and other fullerenes (1985).

Physics

- Archimedes, while sitting in a bathtub, notices that his body becomes lighter as it pushes the water aside. This leads to the first true theory of buoyancy. (c. 250 BC)
- Eratosthenes evaluates the diameter of the Earth by comparing the length of the longest shadow of the day with the distance between that location and a place where the sun shines to the bottom of the well at midday (240 BC)
- Galileo Galilei uses rolling balls to disprove the Aristotelian theory of motion (1602 - 1607)
- Isaac Newton decomposes sunlight with a prism.
- Ole Rømer uses the timing of the eclipses of the moons of Jupiter with respect their distance from earth to estimate the speed of light for the first time. He yields a value of 225,000 km/s (actual value of 299,792 km/s) (1672)
- Henry Cavendish's torsion bar experiment (1798)
- Thomas Young's double-slit experiment (c1805)
- Hans Christian Ørsted discovers the connection of electricity and magnetism by experiments involving a compass and electric circuits (1820)
- Christian Doppler arranges to have trumpets played from a passing train. The ground-observed pitch was higher than that played when the train was approaching then lower than that played as the train passed and moved away, demonstrating the Doppler effect (1845)
- Léon Foucault's namesake Foucault pendulum is first exhibited. It demonstrates the Coriolis force and the rotation of the earth (1851)
- Michelson-Morley experiment exposes weaknesses of the prevailing variant of the theory of luminiferous aether. (1887)
- Guglielmo Marconi demonstrates that radio signals can travel between two points separated by an obstacle. Marconi's servant is behind a hill 3 kilometers away and fires his rifle upon receiving the signals (1895).
- Henri Becquerel, Marie Curie, and Pierre Curie discover radioactivity and describe its properties. (1896)
- Joseph John Thomson's cathode ray tube experiments (discovers the electron and its negative charge) (1897)
- Robert Millikan's oil-drop experiment, which suggests that electric charge occurs as quanta (whole units), (1909)
- Heike Kamerlingh Onnes demonstrates superconductivity (1911)
- Ernest Rutherford's gold foil experiment demonstrated that the positive charge and mass of an atom is concentrated in a small, central atomic nucleus, disproving the then-popular plum pudding model of the atom. (1911) 1911.]]
- Arthur Eddington [http://www.firstscience.com/site/articles/coles.asp leads an expedition] to the island of Principe to observe a total solar eclipse (gravitational lensing). This allows for an observation of the bending of starlight under gravity, a prediction of Albert Einstein's theory of relativity. It was confirmed (although it was later shown that the margin of error was as great as the observed bending)/ (1919)
- Otto Stern and Walter Gerlach conduct the Stern-Gerlach experiment, which demonstrates particle spin (1920)
- Enrico Fermi splits the atom (1934)
- John Bardeen and Walter Brittain fabricate the first working transistor (1947)
- Clyde L. Cowan and Frederick Reines confirm the existence of the neutrino in the neutrino experiment (1955)
- The Scout rocket experiment confirms the time dilation effect of gravity. (1976)
- Stanley Pons and Martin Fleischmann report the production of excess heat from a table-top cold fusion experiment (1989)
- Eric A. Cornell and Carl E. Wieman synthesize Bose-Einstein condensate (1995)

Psychology

- Ivan Pavlov's experiments with dogs and classical conditioning (1900s)
- John B. Watson and Rosalie Rayner conduct the Little Albert experiment showing evidence of classical conditioning (1920)
- Solomon Asch's conformity experiments shows how group pressure can persuade an individual to conform to an obviously wrong opinion (1951)
- B.F. Skinner's demonstrations of operant conditioning (1930s - 1960s)
- Harry Harlow's experiments with baby monkeys and wire and cloth surrogate mothers (1957-1974)
- Stanley Milgram's experiments on human obedience (1963)
- Philip Zimbardo's Stanford prison experiment (1971)
- Allan and Beatrice Gardner' attempts to teach American Sign Language to the chimpanzee Washoe (1970s)
- Martin Seligman studies learned helplessness in dogs (1970s)
- Rosenhan experiment (1972)
- Kansas City preventive patrol experiment (1972-1973)
- Elizabeth Loftus' and John C. Palmer's car crash experiment shows that leading questions can produce false memories (1974)

Economics and Political Science

- Negative Income Tax experiments
- Axelrod's Prisoner's Dilemma Tournament
- Tennessee STAR Class Size Experiment Experiments, famous Experiments, famous

Operationalization

Operationalization is the process of describing an operation that will measure concepts (variables) through specific observations. Operationalization is often used in the social sciences as part of the scientific method. For example, a researcher may wish to measure "anger." Its presence, and the depth of the emotion, cannot be directly measured by an outside observer because anger is intangible. Rather, other measures are used by outside observers, such as facial expression, choice of vocabulary, loudness and tone of voice. If a researcher wants to measure the depth of "anger" in various persons, the most direct operation would be to ask them a question, such as "are you angry", or "how angry are you?". This operation is problematic, however, because it depends upon the definition of the individual. One person might be subjected to a mild annoyance, and become slightly angry, but describe themselves as "extremely angry," whereas another might be subjected to a severe provocation, and become very angry, but describe themselves as "slightly angry." In addition, in many circumstances it is impractical to ask subjects whether they are angry. Since one of the measures of anger is loudness, the researcher can operationalize the concept of anger by measuring how loudly the subject speaks compared to their normal tone.

Experimental error

The word error has different meanings in different domains. Current meanings in some of those domains are described below. The Latin word error meant "wandering" or "straying". Latin, France, 1895 ]]

Statistics

An error is a difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value. See also errors and residuals in statistics.

Experimental science

An error is a bound on the precision and accuracy of the result of a measurement. These can be classified into two types: statistical error (see above) and systematic error. Statistical error is caused by random (and therefore inherently unpredictable) fluctuations in the measurement apparatus, whereas systematic error is caused by an unknown but nonrandom fluctuation. If the cause of the systematic error can be identified, then it can usually be eliminated. Such errors can also be referred to as uncertainties.

Engineering

An error is a difference between desired and actual performance. Engineers often seek to design systems in such a way as to mitigate or preferably avoid the effects of error, whether unintentional or not. One type of error is human error which includes cognitive bias. Human factors engineering is often applied to designs in an attempt to minimize this type of error by making systems more forgiving or error-tolerant. Errors in a system can also be latent design errors that may go unnoticed for years, until the right set of circumstances arises that cause them to become active. See also Observational error.bobok

Medicine

See medical error for a description of error in medicine.

Aviation

See aviation safety for a description of how flying has been made safer by making the aviation system more error-tolerant.

Telecommunication

An error is a deviation from a correct value caused by a malfunction in a system or a functional unit. An example would be the occurrence of a wrong bit caused by an equipment malfunction. (Sources: Federal Standard 1037C and MIL-STD-188). See also error-correcting code and error-detecting code . A soft error is a deviation from a correct value which does not necessarily imply a malfunction.

Computer programming

An error may be a piece of incorrectly written program code. A syntax error is an ungrammatical or nonsensical statement in a program; one that cannot be parsed by the language implementation. A logic error is a mistake in the algorithm used, which causes erroneous results or undesired operation. Anti-patterns, or undesirable program design elements, may make it harder to detect or correct errors. An error may also be an exception, a condition which arises during program execution due to an unexpected event. For instance, it is an error to attempt to write more files onto a disk that is full. Careful programmers write code that can handle errors that may occur; strategies for doing so include using error codes and using exception handling. Continuing past an unhandled error can cause error avalanche, a condition in which errors pile up and behavior becomes more erratic.

Linguistics

An individual language user's deviations from standard language paradigms are sometimes referred to as errors. At present, this usage is out of favor outside of language classes. Those who recognize the role of language usage in everyday social class distinctions feel that linguistics should be descriptive rather than prescriptive to avoid reinforcing dominant class value judgments about what linguistic forms should and should not be used.

Biology

An error is said to occur when perfect fidelity is lost in the copying of information. For example, in an asexually reproducing species, an error (or mutation) has occurred for each DNA nucleotide that differs between the child and the parent. Errors in this sense are not judged as "good" or "bad", although an error may make an organism either more or less adapted to its environment.

Baseball

An error is judged by the official scorer when a runner advances a base because of a fielding mistake, and perfect play would have prevented the advancement, and the mistake was physical. Mental misjudgments are not errors. Failing to get more than one out on given play is not an error. Application of this rule is necessarily subjective. See error (baseball).

External links

- [http://books.nap.edu/html/to_err_is_human/Ch3.PDF Why do errors happen? (pdf)]
- [http://books.nap.edu/html/to_err_is_human Advance Copy of To Err is Human - Building a Safer Health System]
- [http://phys.columbia.edu/~tutorial Error Analysis Tutorial] Category:Error category:Metrology ja:エラー

Cold fusion

: This article is about the nuclear reaction. For the computer programming language, see ColdFusion. ColdFusion Cold fusion is a term for any nuclear fusion reaction that occurs well below the temperature required for thermonuclear reactions (which occur at millions of degrees Celsius).

Introduction

There are a number of suggested processes by which cold fusion may occur, although currently none of these has been shown to release more energy than is required to sustain the reaction (see breakeven): a requirement for the process to be useful for producing power. This does not rule out other uses, such as for compact, desktop neutron generation. The term is often used in a more narrow sense: that is, a phenomenon observed in electrolytic cells in which a small (table-top) apparatus near room temperature and standard atmospheric pressure in which it has been suggested that the the fusion of hydrogen (specifically deuterium) atoms into helium occurs. Additional claims have been made in the cold fusion field in addition to the fusion reaction. For this reason, the terms "Low Energy Nuclear Reactions" and "Condensed Matter Nuclear Science" are also used to describe work in this area. Nuclear fusion using deuterium (an isotope of hydrogen) yields large amounts of energy, uses an abundant fuel source, and produces only small amounts of radioactive waste. Therefore, a cheap and simple process of nuclear fusion would have great economic impact. As of 2005, however, hot fusion cannot be achieved in a controlled and sustained way, and proven cold fusion methods do not seem to yield more energy than is put into them. If cold fusion in electrolytic cells were shown to work, it might become a cheap and simple means of power generation.

History

Early work

Palladium and titanium have a proven ability to absorb large quantities of hydrogen. Although the distance between hydrogen nuclei suspended in such metals is no less than it is in other situations (such as a molecule of water), it has been suggested that these metals might, by bringing the deuterium atoms close together, catalyze the fusion of deuterium at ordinary temperatures. The special ability of palladium to absorb hydrogen was recognized in the 19th century. In the late 1920s, two German scientists, Fritz Paneth and Kurt Peters, reported the transformation of hydrogen into helium by spontaneous nuclear catalysis when hydrogen is absorbed by finely divided palladium at room temperature. These authors later acknowledged that the helium they measured was due to background from the air or the glassware they used. In 1927, Swedish scientist John Tandberg said that he had fused hydrogen into helium in an electrolytic cell with palladium electrodes. On the basis of his work he applied for a Swedish patent for "a method to produce helium and useful reaction energy". After deuterium was discovered in 1932, Tandberg continued his experiments with heavy water. Due to Paneth and Peters' retraction, Tandberg's patent application was eventually denied.

Pons and Fleischmann's experiment

On March 23, 1989, the chemists Stanley Pons of the University of Utah and Martin Fleischmann of the University of Southampton ("P and F") held a press conference and reported the production of excess heat that could only be explained by a nuclear process. The report was particularly astonishing given the simplicity of the equipment, which was just a water electrolysis experiment consisting of a pair of electrodes connected to a battery and immersed in a jar of heavy water (dideuterium oxide). The press reported on the experiments widely, and it was one of the front-page items on most newspapers around the world. The immense beneficial implications of the Utah experiments, if they were correct, and the ready availability of the required equipment, led scientists around the world to attempt to repeat the experiments within hours of the announcement. The press conference followed about a year of work of increasing tempo by Pons and Fleischmann, who had been working on their basic experiments since 1984. Their collaboration goes back even further than this, however. Pons had been a graduate student of Fleischmann's at the University of Southampton. In 1988 they applied to the U.S. Department of Energy for funding for a larger series of experiments: up to this point they had been running their experiments "out of their pocket". The term "cold fusion" was coined by Dr Paul Palmer of Brigham Young University in 1986 in an investigation of "geo-fusion", or the possible existence of fusion in a planetary core. The term was then applied to the Fleischmann-Pons experiment in 1989. The grant proposal was turned over to several people for peer review, including Steven Jones of Brigham Young University. Jones had worked on muon-catalyzed fusion for some time, and had written an article on the topic entitled "Cold Nuclear Fusion" that had been published in Scientific American, July 1987. He had since turned his attention to the problem of fusion in high-pressure environments, believing that fusion in the metallic hydrogen core of Jupiter might be responsible for the higher-than-normal temperatures of that planet. Paul Palmer noted that the same mechanism might explain the high interior temperature of the Earth (hotter than could be explained without nuclear reactions), and the unusually high concentrations of helium-3 around volcanoes, which implied some sort of nuclear reaction within. Jones started studying high-pressure fusion, which he referred to as piezonuclear fusion, by working with diamond anvils; but he had since moved to electrolytic cells similar to those being worked on by Pons and Fleischmann. In order to characterize the reactions, Jones had spent considerable time designing and building a neutron counter, one able to accurately measure the tiny numbers of neutrons being produced in his experiments. Both teams were in Utah, but did not know of each other's work until the peer review. After that, they met on several occasions to discuss sharing work and techniques. During this time Pons and Fleischmann described their experiments as generating considerable "excess energy", excess in that it could not be explained by chemical reactions alone. If this were true, their device would have considerable commercial value. Jones was measuring neutron flux instead and seems to have considered it primarily of scientific interest, not commercial. In order to avoid problems in the future, the teams apparently agreed to simultaneously publish their results, although their accounts of their March 6 meeting differ. In mid-March both teams were ready to publish, and Fleischmann and Jones were to meet at the airport on March 24 to both hand in their papers at the exact same time. However Pons and Fleischmann then "jumped the gun," and held their press conference the day before. Jones, apparently furious at being "scooped," faxed in his paper to Nature as soon as he saw the press announcements. The rush to publish perhaps did as much to muddy the field as any scientific aspects. Within days scientists around the world had started work on duplications of the experiments. On April 10 a team at Texas A&M University published results of excess heat, and later that day a team at the Georgia Institute of Technology announced neutron production. Both results were widely reported on in the press. Not so well reported was the fact that both teams soon withdrew their results for lack of evidence. For the next six weeks competing claims, counterclaims, and suggested explanations kept the topic on the front pages, and led to what writers have referred to as "fusion confusion." On April 12 Pons received a huge standing ovation during his presentation at the semi-annual meeting of the American Chemical Society. In May, the president of the University of Utah, who had already secured a $5 million commitment from his state legislature, asked for $25 million from the federal government to set up a "National Cold Fusion Institute". On May 1st a meeting of the American Physical Society held a session[http://www.ibiblio.org/pub/academic/physics/Cold-fusion/vince-cate/aps.ascii] on cold fusion that ran past midnight; a string of failed experiments were reported. A second session started the next evening and continued in much the same manner. To some degree this reflected a split between the "chemists" and the "physicists", though it also reflected a more general change in opinion during the weeks which passed between the meetings. Skepticism of the cold fusion claims was rising among both chemists and physicists as more experimentalists attempted and were unable to replicate the experiment. At the end of May the Energy Research Advisory Board (a standing advisory committee in the U.S. Department of Energy) formed a special panel to investigate cold fusion. The report of the panel after five months' study was that there was no convincing evidence for cold fusion, and that such an effect "would be contrary to all understanding gained of nuclear reactions in the last half century." It specifically recommended against any special funding for cold fusion research, but was "sympathetic toward modest support for carefully focused and cooperative experiments within the present funding system". [http://www.ncas.org/erab/sec5.htm] Both critics and those attempting replications were frustrated by what they said was incomplete information released by the University of Utah. With the initial reports suggesting successful duplication of their experiments there was not much public criticism, but a growing body of failed experiments started a "buzz" of its own. Pons and Fleischmann later apparently claimed that there was a "secret" to the experiment; on the other hand, Fleischmann said at a meeting in April that all the necessary details had been given in the published paper. The facts here are not clear; but if such data had been withheld, the report would have been outside the field of modern science, and scientists would have been justified in dismissing the matter out of hand. By the end of May much of the media attention had faded among the competing results and counterclaims. More significantly, the research effort decreased greatly as most attempts at replication failed and none produced definitive results. Nonetheless, projects continued around the world.

Experimental set-up and observations

media In their original set-up, Fleischmann and Pons used a Dewar flask (a double-walled vacuum flask) for the electrolysis, so that heat conduction would be minimal on the side and the bottom of the cell (only 5% of the heat loss in this experiment). The cell flask was then submerged in a bath maintained at constant temperature to eliminate the effect of external heat sources. They used an open cell, thus allowing the gaseous deuterium and oxygen resulting from the electrolysis reaction to leave the cell (with some heat too). It was necessary to replenish the cell with heavy water at regular intervals. For the temperature observations to be meaningful the cell must be kept at a uniform temperature. Rather than using a mechanical method of stirring, sparging with the generated D₂ gas was done to equalize the temperature "when necessary"; however, the efficacy of this method of maintaining the cell at a uniform temperature would later be disputed. Special attention was paid to the purity of the palladium cathode and electrolyte to prevent the build-up of material on its surface, especially after long periods of operation. The cell was also instrumented with a thermistor to measure the temperature of the electrolyte, and an electrical heater to generate pulses of heat and calibrate the heat loss due to the gas outlet. After calibration, it was possible to compute the heat generated by the reaction. A constant current was applied to the cell continuously for many weeks, and heavy water was added as necessary. For most of the time, the power input to the cell was equal to the power that went out of the cell within measuring accuracy, and the cell temperature was stable at around 30 °C. But then, at some point (and in some of the experiments), the temperature reportedly rose suddenly to about 50 °C without changes in the input power, for durations of two days or more. The generated power was calculated to be about 20 times the input power during the power bursts. Eventually the power bursts in any one cell would no longer occur, and the cell was turned off. Pons and Fleischmann also initially reported that a cell was generating 2.45 MeV neutrons at a rate three times the natural background rate. There was, however, no equipment directly measuring neutron energies, and this report was based on a mistaken inference from a gamma-ray spectrum. The most spectacular result they reported was that in one cell most of the electrode melted and part of it vaporized, destroying the cell and the fume hood enclosing it. In the months after the initial report went public, a physicist colleague of Pons at the University of Utah, Michael Salomon, was invited into Pons' laboratory. In the five week period he and his research group observed the cells, no fusion products were detected. Pons stated that none of the cells were actively producing the excess heat at the time those observations were taking place, except during one two-hour period during which the detection equipment was unable to function because of a power failure. As neutron irradiation would produce small amounts of ²⁴Na in the detector, Salomon quickly performed an analysis for that product, and found no amount consistent with power production of more than one microwatt. When Salomon and his co-workers had published their results in the journal Nature, each of them received a letter from attorney C. Gary Triggs, declaring that the "paper as published was untenable" and that it should be "voluntarily retracted." Triggs had, he said, been instructed by his clients "to take whatever action is deemed appropriate to protect their legal interests and reputations." Salomon and other scientists, perceiving this as an unprecedented threat against open scientific controversy, rejected the claims categorically and angrily; later, the threats were largely withdrawn.

Continuing efforts

There are currently a number of people researching the possibilities of generating power with cold fusion. Scientists in several countries continue the research, and meet at the International Conference on Cold Fusion (see Proceedings at [http://www.lenr-canr.org/index.html]). The generation of excess heat has been reported by
- Michael McKubre, director of the Energy Research Center at SRI International,
- Richard A. Oriani (University of Minnesota, in December 1990),
- Robert A. Huggins (at Stanford University in March 1990),
- Y. Arata (Osaka University, Japan),
- S. Szpak, Mosier-Boss (SPAWAR Naval Research Laboratory in 2004), among others. In the best experimental set-up, excess heat was reported in 50% of the experiment reproductions. Various fusion ashes and transmutations were reported by some scientists. Dr. Michael McKubre thinks a working cold fusion reactor is possible. Dr. Edmund Storms, a former scientist with The Los Alamos National Laboratory in New Mexico, maintains an international database of research into cold fusion. In March, 2004, the U.S. Department of Energy (DOE) decided to review all previous research of cold fusion in order to see whether further research was warranted by any new results. The review document[http://www.newenergytimes.com/reports/DOE/2004-DOE-Summary-Paper.pdf] submitted to the DOE by the group of scientists who had requested a new review process states that "The experimental evidence for anomalies in metal deuterides, including excess heat and nuclear emissions, suggests the existence of new physical effects". It recognizes indirect evidence in support of the D + D → ⁴He + 23.8 MeV (heat) reaction, although the measurement of ⁴He quantity is imprecise. This review document was submitted to peer review, to a mixed but predominantly negative response. Of the 18 reviewers, "Two-thirds of the reviewers commenting on Charge Element 1 did not feel the evidence was conclusive for low energy nuclear reactions, one found the evidence convincing, and the remainder indicated they were somewhat convinced. Many reviewers noted that poor experiment design, documentation, background control and other similar issues hampered the understanding and interpretation of the results presented." [http://www.science.doe.gov/Sub/Newsroom/News_Releases/DOE-SC/2004/low_energy/CF_Final_120104.pdf] In 2004, Mike McKubre of SRI International reported that the effect is highly dependent on the packing of deuterium in the electrode. He reports that with a deuterium/palladium ratio of 1:1 (i.e., one deuterium atom for each palladium atom) excess heat is consistently produced, whereas at a ratio of 9:1 only 2 experimental runs in 12 show excess heat. Should the effect turn out to be reproducible (which is not yet established in 2004), it should be possible to make experiments that will show definitely whether the heat is due to chemical effects, cold fusion, or some form of energy storage. As of 2004 the excess heat phenomenon remains unexplained, and the reported energy output has never been associated with an equivalent amount of fusion products of any kind. Although there may be a genuine physical phenomenon at work, the theory that it involves nuclear fusion is unproven and widely seen as unlikely. Less exotic theories have been proposed, but also remain unproven. After sixteen years of investigation, study continues, and investigators are hopeful that the phenomenon will be understood in a matter of years.

Arguments in the controversy

Here are the main arguments in the controversy:

Experimental design

One of the main criticisms of the cold fusion claims is that the experimental design made it very difficult to get reliable and repeatable results. In particular, there are many different ways by which the experiment can exchange energy with its environment, and the book-keeping necessary to establish whether or not there is any net energy gain has been criticized for being difficult to do correctly and prone to error. This objection could be overruled either by creating an experiment which is less subject to errors, or by looking for signs of fusion which have nothing to do with excess heat. Neither of these strategies has produced conclusive evidence that this cold fusion process exists.

Reproducibility of excess heat

While some researchers claimed to have reproduced the excess heat with similar, or different, experiments, they could not do it with predictable results, and many others failed to measure excess heat. However, it is not uncommon for a new phenomenon to be difficult to control, and to bring erratic results. For example, attempts to repeat electrostatic experiments (similar to those performed by Benjamin Franklin) often fail due to excessive air humidity. That does not mean that electrostatic phenomena are fictitious, or that experimental data are fraudulent. On the contrary, occasional observations of new events, by qualified experimenters, can in some cases be the essential steps leading to recognized discoveries. At the same time, it is also the case that experiments are hard to do, and it is easy to come up with results which look anomalous but which are in fact the result of experimental design deficiencies. The reproducibility of the result will remain the main issue in cold fusion research until an experiment is designed which is fully reproducible by following a clear recipe, and which preferably generates power continuously rather than sporadically and does so in a way that cannot be attributed to experimental defects.

Lack of expected decay products

Even in the face of inconsistent evidence regarding the production of heat, cold fusion could be established by observation of decay products which are specific only to fusion. According to conventional fusion theory, if the excess heat were generated by the fusion of 2 deuterium atoms, the most probable outcome would be the generation of either a tritium atom and a proton, or a ³He and a neutron. The level of neutrons, tritium and ³He reported from the Fleischmann-Pons experiment was well below the level expected in view of the heat reported—such a neutron flux would in fact have been lethal—implying that these fusion reactions cannot explain it. Researchers in the cold fusion field claim that ⁴He is the dominant by-product of cold fusion. In conventional fusion, less than 1% of the nuclear products are seen as ⁴He.[http://newenergytimes.com/Library/2003MilesM-ICCF-10-Correlation-Of-Excess.pdf] [http://newenergytimes.com/Library/1991BushB-HeliumProductionDuringTheElectrolysis.pdf][http://newenergytimes.com/Library/2002DeNinnoA-ExperimentalEvidenceOf4HeProduction.pdf][http://www.newenergytimes.com/library/1998GozziD-HeGozziDxrayheatex.pdf] A larger collection of related papers on helium evolution is [http://newenergytimes.com/Reports/Heat&NuclearProductCorrelation.htm here]. It should also be noted that none of the other processes termed cold fusion have these theoretical issues. In particular, the Farnsworth-Hirsch Fusor is sold commercially as a source of neutrons, and evidence for some of the other forms of fusion comes not from excess heat but from the decay products. This experimental result could be and has been explained by arguing that the current understanding of physics is incorrect, but this leads to other problems.

Current understanding of physics

In addition to the lack of decay products, current understanding of nuclear fusion shows that the following explanations are not adequate:
- Nuclear reaction in general: The average density of deuterium in the palladium rod seems vastly insufficient to force pairs of nuclei close enough for fusion to occur according to mechanisms known to mainstream theories. The average distance is approximately 0.17 nanometers, a distance at which the attractive strong nuclear force cannot overcome the Coulomb repulsion. Actually, deuterium atoms are closer together in D₂ gas molecules, which do not exhibit fusion.
- Fusion of deuterium into helium 4: if the excess heat were generated by the fusion of two deuterium atoms into ⁴He, a reaction which is normally extremely rare, gamma rays and helium would be generated. Again, insufficient levels of helium and gamma rays have been observed to explain the excess heat, and there is no known mechanism to explain how gamma rays could be converted into heat. Disagreement with existing theory does not in itself prove that the experiment is wrong. For example, both superconductivity and Brownian motion were observed (and could be reproduced by anyone with suitable equipment) long before they were explained; high-temperature superconductivity has yet to be explained, despite the industrial availability of such superconductors. On the other hand, one can also cite observations of polywater and N-rays. Only four or five researchers claimed they reproduced these effects, and they claimed the signal to noise ratio was very low. [1] [2]. In contrast, hundreds of researchers worldwide claim they have reproduced cold fusion, often at very high signal to noise ratios. Excess heat has been measured at sigma 50 to 100, and tritium between 60 and 1 million times background. Roughly 500 papers were published about polywater at the peak, but most were theory and only a handful claimed positive results, whereas over 3,000 papers on cold fusion have been published. Although requiring exotic or unknown physics does not rule out the existence of a process, it does drastically increase the level of evidence needed to establish a process, while at the same time making it much harder to perform experiments to verify that the process exists. Requiring exotic or unknown physics increases the suspicion that the underlying cause of the experimental results lies in errors of experimental design or misinterpretation of results, and causes the scientific community to be skeptical of marginal results and demand unambiguous demonstrations of a process. At the same time, lack of an adequate theory makes it much harder to design experiments to create those results. Without such theory, it is much more difficult to predict what could happen in a given situation and design experiments to test those predictions. For example, based on standard nuclear theory, one would expect that the amount of heat generated would depend on the concentration of heavy water or the ratio between deuterium and tritium. These relationships do not appear to hold consistently, and the inability to establish any definite relationships between the energy output of the experiments and experimental inputs leads to skepticism that what is being observed has anything to do with fusion. Most people still define "cold fusion" as a phenomenon in which "heat is produced from fusion of isolated deuterium nuclei at ordinary temperatures." It is not difficult to be convinced that such phenomenon is impossible. This has nothing to do with chemically assisted nuclear anomalies in condensed matter reported in recent years. This refers, for example, to emission of neutrons, at rates too small to release measurable amounts of heat. It also refers to generation of helium and tritium, to unusual isotopic ratios, and to nuclear transmutations in deuterized metals. The second DOE review (December, 2004) recognizes "a number of basic science research areas that could be helpful in resolving some of the controversies in the field, two of which were: 1) material science aspects of deuterated metals using modern characterization techniques, and 2) the study of particles reportedly emitted from deuterated foils using state-of-the-art apparatus and methods." 1. Klotz, I., The N-Ray Affair. Scientific American, 1980. 242(5): p. 168-175. 2. Franks, F., Polywater. 1981, Cambridge, MA: MIT Press.

Energy source vs. power store

Some skeptics claim that while the output power is higher than the input power during the power burst, the power balance over the whole experiment does not show significant imbalances. Since the mechanism under the power burst is not known, one cannot say whether energy is really produced, or simply stored during the early stages of the experiment (loading of deuterium in the Palladium cathode) for later release during the power burst. A "power store" discovery would yield only a new, and very expensive, kind of storage battery, not a source of abundant cheap fusion power. Cold fusion researchers disagree. They point out that in all experiments in which excess heat has been recorded, the overall balance has been positive; there are no instances in which a heat deficit was recorded first, that would balance out the excess. In most bulk palladium electrochemical experiments, an incubation period of 10 to 20 days is followed by continuous excess heat production, which often continues longer than the incubation period. "Isothermal Flow Calorimetric Investigations of the D/Pd System" shows typical examples. Since the excess heat is easily detected, at a high signal to noise ratio, and the initial deficit would have to be even larger than the excess that follows, it would easily be detected. Researchers also point out that most cells produce far more energy than any known chemical storage mechanism would permit. Chemical processes store (or produce) at most 12 eV per atom of reactant, whereas many cold fusion experiments have produced hundreds of eV per atom of cathode material, and some have produced ~100,000 eV per atom. Furthermore, many researchers, notably Kainthla et al. and McKubre et al. have conducted careful inventories of chemical fuel and potential storage mechanisms in cold fusion cells, and they have found neither fuel nor spent ash that could account for more than a tiny fraction of the excess heat. Since many cells have released large amounts of energy, a megajoule or more, this chemical fuel would have to be present in macroscopic amounts. In fact, in many cases the volume of ash would greatly exceed the entire cell volume. These issues of energy storage and chemical fuel hypotheses have been discussed in the literature exhaustively. See, for example, "A Response to the Review of Cold Fusion by the DoE", section II.1.2.

Other kinds of fusion

This article focuses on the Fleischmann-Pons effect produced in electrolytic cells. This effect has also been observed with other methods of forming hydrides such as gas loading, electromigration and ion implantion. Other forms of fusion have been studied by scientists. Some are "cold" in the sense that no part of the reaction is actually hot (except for the reaction products), some are "cold" in the sense that the energies required are low and the bulk of the material is at a relatively low temperature, and some are "hot", involving reactions which create macroscopic regions of very high temperature and pressure.
- Fusion with low-energy reactants.
- Muon-catalyzed fusion is a well-established and reproducible fusion process which occurs at ordinary temperatures. It has been studied in detail by Steven Jones in the early 1980s. Because of the energy required to create muons and the fact that muons have limited lifetimes, it is not currently able to produce net energy, and analyses indicate at present that energy production from the reaction is not possible.
- Fusion with high-energy reactants in relatively cold condensed matter. (Energy losses from the small hot spots to the surrounding cold matter will generally preclude any possibility of net energy production.)
- Pyroelectric fusion was reported in April 2005 by a team at UCLA. The scientists used a pyroelectric crystal heated from −30 to 45 degrees Fahrenheit (from −34 to 7 °C) combined with a tungsten needle to produce an electric field of about 25 gigavolts per meter to ionize and accelerate deuterium nuclei into an erbium deuteride target. Though the energy of the deuterium ions generated by the crystal has not been directly measured, the authors used 100 keV (a temperature of about 10⁹ K) as an estimate in their modeling.[http://www.nature.com/nature/journal/v434/n7037/extref/nature03575-s1.pdf] At these energy levels, two deuterium nuclei can fuse together to produce a helium-3 nucleus, a 2.45 MeV neutron and bremsstrahlung. This experiment has been repeated successfully, and other scientists have confirmed the results. Although it makes a useful neutron generator, the apparatus is not intended for power generation since it requires far more energy than it produces. [http://rodan.physics.ucla.edu/pyrofusion/] [http://www.aip.org/pnu/2005/split/729-1.html] [http://www.christiansciencemonitor.com/2005/0606/p25s01-stss.html] [http://msnbc.msn.com/id/7654627]
- Antimatter-initialized fusion uses small amounts of antimatter to trigger a tiny fusion explosion. This has been studied primarily in the context of making nuclear pulse propulsion feasible. This is not near becoming a practical power source, due to the cost of manufacturing antimatter alone.
- In sonoluminescence, acoustic shock waves create temporary bubbles that collapse shortly after creation, producing very high temperatures and pressures. In 2002, Rusi P. Taleyarkhan reported the possibility that bubble fusion occurs in those collapsing bubbles. As of 2005, experiments to determine whether fusion is occurring give conflicting results. If fusion is occurring, it is because the temperature and pressure are sufficiently high to produce hot fusion.
- Fusion with macroscopic regions of high energy plasma:
- "Standard" "hot" fusion, in which the fuel reaches tremendous temperature and pressure inside a fusion reactor, nuclear weapon, or star.
- The Farnsworth-Hirsch Fusor is a tabletop device in which fusion occurs. This fusion comes from high effective temperatures produced by electrostatic acceleration of ions. The device can be built inexpensively, but it too is unable to produce a net power output. These devices have a valid use however, and are commercially sold as a source of neutrons. The ion energy distribution is generally supposed to be nearly mono-energetic, but Todd Rider showed in his doctoral thesis for Massachusetts Institute of