Experiment at home. Launching paper rockets

Incredible facts

Darwin flowers

Most people are familiar with the work of Charles Darwin and his famous journey to South America. He made his most important discoveries in the Galapagos Islands, where each of the 20 islands had its own unique set of species perfectly adapted to its environment. But few people know about Darwin's experiments after he returned to England. Some of them focused on orchids.

In the process of growing and studying several types of orchids, he realized that complex flowers orchids are an adaptation that allows flowers to attract insects, which then transfer pollen to neighboring plants. Each insect is specifically designed to pollinate one type of orchid. Take, for example, an orchid Star of Bethlehem(Angraecum sesquipedale), in which nectar is stored at a depth of 30 centimeters. Darwin foresaw that there must be an insect that pollinates this type of orchid. Of course, in 1903, scientists discovered a species called the twilight butterfly, which has a long proboscis that can reach the nectar of this type of orchid.

Darwin used the data he collected about orchids and their insect pollinators to strengthen his theory of natural selection. He argued that cross-pollinated orchids are more viable than self-pollinated ones because selfing reduces genetic diversity, which ultimately has a direct impact on the survival of the species. Thus, three years after he first described natural selection In On the Origin of Species, Darwin carried out several more experiments on flowers and strengthened his claims about the framework of evolution.

DNA decoding

James Watson and Francis Crick came very close to deciphering DNA, but their discoveries depend largely on the work of Alfred Hershey and Martha Chase, who carried out the famous 1952 this day an experiment that helped them determine how DNA molecules are related to heredity. Hershey and Chase were working with a type of virus known as a bacteriophage. This virus, consisting of a protein coat that surrounds a strand of DNA, infects a bacterial cell, which programs it to produce new infected cells. The virus then kills the cell and new viruses are born. Hershey and Chase knew about this, but they did not know which component—protein or DNA—was responsible. They didn't know this until they conducted their ingenious "blender" experiment, which led them to DNA ribonucleic acids.

After the Hershey and Chase experiment, many scientists such as Rosalind Franklin focused on studying DNA and its molecular structure. Franklin used a technique called X-ray diffraction to study DNA. It involves the "invasion" of X-rays into the fibers of purified DNA. When rays interact with a molecule, they “stray” from their original course and become diffracted. The diffracted beams then form an image of a unique molecule, ready for analysis. Franklin's famous photograph shows the X-shaped curve that Watson and Crick termed the "signature of the DNA molecule." They were also able to determine the width of the spiral by looking at Franklin's image.

First vaccination

Until the complete global eradication of smallpox at the end of the 20th century, this disease was serious problem. In the 18th century, a disease caused by the smallpox virus killed one in ten children born in Sweden and France. “Catching” the virus was the only possibility of “treatment.” This led to people themselves trying to catch the virus from purulent ulcers. Unfortunately, many of them died during the dangerous attempt of self-vaccination.

Edward Jenner, a British doctor, began studying the virus and developing effective methods treatment. The genesis of his experiments was the observation that milkmaids living in his hometown were often infected with the cowpox virus, a non-fatal disease similar to smallpox. Milkmaids who contracted cowpox seemed to be protected from smallpox infection, so in 1796 Jenner decided to test whether a person could develop immunity to smallpox if infected with the cowpox virus. The boy on whom Jenner decided to conduct his experiment was named James Phipps. Jenner cut Phipps' arm and infected him with cowpox. After some time the boy recovered. 48 days later, the doctor introduced the smallpox virus into his body and found that the boy was immune.

Scientists now know that the vaccinia and smallpox viruses are so similar that the human immune system is unable to distinguish them.

Proof of the existence of the atomic nucleus

Physicist Ernest Rutherford has already won Nobel Prize in 1908 for his radioactive work, during which time he also began conducting experiments to reveal the structure of the atom. The experiments were based on his previous research, which showed that radioactivity consists of two types of rays - alpha and beta. Rutherford and Hans Geiger discovered that alpha rays are streams of positively charged particles. When he released alpha particles onto the screen, they created a clear and sharp image. But if a thin sheet of mica was placed between the alpha radiation source and the screen, the resulting image was blurry. It was clear that the mica scattered some alpha particles, but how and why this happened was not understood at the time.

In 1911, a physicist placed a thin sheet of gold foil between an alpha radiation source and a screen, 1-2 atoms thick. He also placed another screen in front of the alpha radiation source in order to understand which particles were deflected back. On the screen behind the foil, Rutherford observed a diffuse pattern similar to what he saw when using a mica sheet. What he saw on the screen in front of the foil surprised Rutherford, as several alpha particles bounced straight back. Rutherford concluded that the strong positive charge at the heart of the gold atoms sent the alpha particles back to the source. He called this strong positive charge the "nucleus", and stated that, compared to the overall size of the atom, its nucleus must be very small, otherwise many more particles would return back. Today, scientists, like Rutherford, visualize atoms: small, positively charged nuclei surrounded by large, mostly empty space inhabited by a few electrons.

X-ray

We've already talked about Franklin's X-ray diffraction research, but his work owes a lot to Dorothy Crowfoot Hodgkin, one of three women to win the Nobel Prize in Chemistry. In 1945, Hodgkin was considered one of the world's leading practitioners of X-ray diffraction techniques, so it is not surprising that she was the one who eventually showed the structure of one of the most important chemicals in medicine today - penicillin. Alexander Fleming discovered a bacteria-killing substance back in 1928, but it took scientists some more time to purify the substance in order to develop effective treatment. Thus, with the help of penicillin atoms, Hodgkin was able to create semi-synthetic derivatives of penicillin, which turned out to be a revolution in the fight against infections.

Hodgkin's research became known as X-ray crystallography. For the first time, chemists crystallized the compounds they wanted to analyze. It was a challenge. After testing penicillin crystals by two different companies, Hodgkin fired X-ray waves through the crystals and allowed radiation to "penetrate the object being tested." When X-rays interacted with the electrons of the object under study, the rays became slightly diffracted. This resulted in a clear pattern of dots appearing on the film. By analyzing the position and brightness of these dots and performing many calculations, Hodgkin determined exactly how the atoms in the penicillin molecule were arranged.

A few years later, she used the same technology to reveal the structure of vitamin B12. She received the Nobel Prize in Chemistry in 1964, an honor that no other woman has received.

The emergence of life

In 1929, biochemists John Haldane and Alexander Oparin independently proposed that there was no free oxygen in the Earth's early atmosphere. In those harsh conditions, they assumed organic compounds could be formed from simple molecules, receiving a serious charge of energy, be it ultraviolet radiation or bright light. Haldane also added that the oceans were likely the first sources of these organic compounds.

American chemists Harold Urey and Stanley Miller decided to test the hypotheses of Oparin and Haldane in 1953. They were able to recreate Earth's early atmosphere by carefully working on controlled, closed system. The role of the ocean was played by a flask with heated water. After the water vapor rose and collected in another container, Urey and Miller added hydrogen, methane and ammonia to simulate an oxygen-free atmosphere. Sparks were then formed in the flask, representing light in the mixture of gases. Finally, a condenser cooled the gases into a liquid, which they then took for analysis.

A week later, Yuri and Miller received surprising results: organic compounds were present in abundance in the cooled liquid. In particular, Miller discovered several amino acids, including glycine, alanine and glutamic acid. Amino acids are the building blocks of proteins, which themselves are key components of both cellular structures and cellular enzymes responsible for the functioning of important chemical reactions. Urey and Miller came to the conclusion that organic molecules could well survive in an oxygen-free environment, which, in turn, did not keep the simplest organisms from appearing.

Creation of light

When light appeared in the 19th century, it remained a mystery that inspired many fascinating experiments. For example, the “double-slit experiment” by Thomas Young, which showed how light waves behave, but not particles. But back then they didn’t know how fast light travels.

In 1878, physicist A.A. Michelson conducted an experiment to calculate the speed of light and prove that it was a finite, measurable quantity. Here's what he did:

1. Firstly, he placed two mirrors far apart on different sides dams near the university campus, positioning them so that the incident light was reflected from one mirror and returned back. He measured the distance between the mirrors and found that it was 605.4029 meters.

3. Using lenses, he focused a beam of light onto a stationary mirror. When a beam of light touched a stationary mirror, it bounced off and was reflected in a rotating mirror, near which Michelson placed a special screen. Due to the fact that the second mirror rotated, the trajectory of the return of the light beam changed slightly. When Michelson measured these deviations, he came up with a figure of 133 mm.

4. Using the data obtained, he was able to measure the speed of light to be 186,380 miles per second (299,949,530 kilometers). The acceptable value for the speed of light today is 299,792,458 km per second. Michelson's measurements showed surprisingly accurate results. Moreover, scientists now have at their disposal more accurate ideas about light and the foundations on which the theories of quantum mechanics and the theory of relativity are built.

Discovery of radiation

1897 was a very important year for Marie Curie. Her first child was born, and just a few weeks after his birth, she went looking for a topic for her doctoral dissertation. Eventually, she decided to study the "uranium rays" first described by Henri Becquerel. Becquerel discovered these rays by accident when he left uranium salts wrapped in an opaque material along with photographic plates in a dark room, and returned to find that the photographic plates were completely exposed. Marie Curie chose to study these mysterious rays in order to identify other elements that acted in a similar way.

Already at an early stage of study, Curie realized that thorium produces the same rays as uranium. She started labeling these unique elements, as "radioactive" and quickly realized that the strength of radiation produced by uranium and thorium depended on the amount of thorium and uranium. In the end, she will be able to prove that the rays are properties of the atoms of a radioactive element. This in itself was a revolutionary discovery, but Curie was stopped by it.

She discovered that pitchblende (uraninite) was more radioactive than uranium, which led her to the idea that there must be an element unknown to her in natural minerals. Her husband Pierre joined the research, and they systematically reduced the amounts of pitchblende until they discovered a new isolated element. They named it polonium, after Mary's homeland of Poland. Soon after, they discovered another radioactive element, which they called radium, from the Latin for "ray." Curie won two Nobel Prizes for her work.

Dog days

Did you know that Ivan Pavlov, the Russian physiologist and chemist and author of the salivation and conditioning experiment in dogs, was not at all interested in psychology or behavior? He was interested in the topics of digestion and blood circulation. In fact, he was studying the digestive system of dogs when he discovered what we know today as “conditioned reflexes.”

In particular, he tried to understand the relationship between salivation and stomach function. Shortly before this, Pavlov had already noted that the stomach does not begin to digest food without salivation, which occurs first. In other words, reflexes in the autonomic nervous system closely connect these two processes with each other. Next, Pavlov decided to find out whether external stimuli could affect digestion in a similar way. To test this, he started turning the lights on and off while the dog was eating, ticking a metronome, and making a buzzer sound audible. In the absence of these stimuli, the dogs salivated only when they saw and ate food. But after a while, they began to salivate when stimulated by sound and light, even if they were not given food at the time. Pavlov also discovered that this type of conditioning dies if the stimulus is used "incorrectly" too often. For example, if a dog hears a sound signal often, but does not receive food, then after some time, it stops responding to the sound by salivating.

Pavlov published his results in 1903. A year later he received the Nobel Prize in Medicine, not for his work on conditioned reflexes, but "in recognition of his work on the physiology of digestion, by which knowledge of vital aspects has been transformed and expanded."

Stanley Milgram's experiments, which he conducted in the 1960s, still qualify as one of the most famous and controversial scientific experiments. Milgram wanted to find out how far the average person would go to inflict pain on another person under pressure from authority. Here's what he did:

1. Milgram recruited volunteers, ordinary people, who were ordered to inflict some pain on other volunteer actors. The experimenter played the role of an authority figure who was constantly present in the room during the study.

2. Before the start of each test, the authority demonstrated to unsuspecting volunteers how to use a shock device that could shock a person with a discharge of 15-450 volts (increased level of danger).

3. The scientist further noted that they should test how shock can improve word memory through associations. During the experiment, he instructed volunteers to “reward” volunteer actors with shock blows for incorrect answers. The more incorrect answers there were, the higher the voltage level on the device. Moreover, it is worth noting that the device was made on top level: above each switch the voltage corresponding to it was written, from “weak shock” to “hard shock”, the device was equipped with many panels with pointer voltmeters. That is, the subjects did not have the opportunity to doubt the authenticity of the experiment, and the study was structured in such a way that for every correct answer there were three incorrect ones and the authority told the volunteer what “blow” to punish the “incapable student.”

4. The "students" screamed when they received shock blows. After the impact exceeded 150 volts, they demanded release. At the same time, the authority urged volunteers to continue the experiment, not paying attention to the demands of the “students”.

5. Some participants in the experiment wanted to leave after reaching the punishment of 150 volts, but most continued until they reached the maximum shock level of 450 volts.

At the end of the experiments, many spoke out about the unethical nature of this study, but the results obtained were impressive. Milgram proved that ordinary people can hurt an innocent person simply because they received such a command from a powerful authority.

Conducting an experiment is the very method used by scientists who are going to study this or that phenomenon in the hope of learning something new about the world around us. Good experiments follow a clear and logically ordered design aimed at isolating and testing clear, specifically defined variables. Once you learn the fundamental principles that underlie scientific experiments, you can apply them to your own experiments. Regardless of the purpose of the research, all good experiments are conducted according to the principles of logic and deduction that underlie scientific method knowledge, and it doesn’t matter what exactly you study - something at the school level or the Higgs boson.

Steps

Part 1

Preparing a scientific experiment

Choose a research topic. Experiments whose results lead to a full-scale revision of the scientific community's views on a particular problem are extremely rare. Most experiments set themselves a more modest task - to answer a specific question. Scientific knowledge is based on the accumulation of knowledge obtained through countless experiments. Choose a topic or unanswered question that you can explore with a small experiment.

• For example, if you want to conduct an experiment with agricultural fertilizer, then phrase the question differently - “Which fertilizer is the best?” Why? The world is full of different fertilizers; in one experiment you will not be able to study them all at once. A better question would be to be more specific: “What concentration of nitrogen in fertilizer results in the highest corn yields?”
• Modern scientific knowledge- the thing is very, very extensive. If you intend to conduct serious scientific research, then before starting the experiment, carefully study, as they say, the hardware. Perhaps experiments have already been conducted in the past that answer your question? If so, then adjust your research topic to explore some topic that has remained unexplored.

1. Select the variable or variables. A good science experiment tests specific, measurable parameters called “variables.” In general terms, a scientist conducts an experiment with a certain number of tested variables. When conducting an experiment, it is extremely important to change only the specific variables you are studying (and only them)!

   • Let's go back to the fertilizer example. Our scientist will grow corn in several beds in a bud fertilized with fertilizers containing different content nitrogen. The same amount of fertilizer will be applied to each bed. Moreover, the scientist will even be sure that the nitrogen content is the only difference between fertilizers. In addition, the scientist will grow the same number of corn plants in each bed, and will grow them at the same time and in the same type of soil.

2. Come up with a hypothesis. A hypothesis is an opinion about what the results of an experiment will be. The hypothesis, by the way, is not a blind guess at all, no! Good hypotheses are drawn up on the basis of preliminary research on the topic of the experiment (this is carried out at the time of choosing the research topic). Build a hypothesis based on data obtained from similar experiments conducted by your colleagues or, if the problem you are studying is not yet very well documented, on the scientific literature and studies that you can find. And remember that the hypothesis may turn out to be wrong - but even in this case it will be considered a result, an achievement! Why? But because you have proven that the hypothesis you proposed is not true.

   • As a rule, a hypothesis takes the form of a quantifying declarative sentence. The hypothesis also takes into account how the experimental parameters will change. For our fertilizer experiment, a good hypothesis would be: “Fertilizing corn with fertilizers containing 400 grams of nitrogen per 36.3 liters will result in a larger crop than if using fertilizers with a different nitrogen content.”

3. Consider how you will collect data. It is important to know two things in advance: 1) when you will collect data; 2) what data you will collect. This data must be measured at a conventional time or, if necessary, at regular intervals. In our case, the weight of corn crops is measured in kilograms after a certain period of growth. This is then compared to the nitrogen content of the fertilizer applied to the bud. However, in other experiments it would be quite appropriate to collect data at intervals.

   • If you organize the data into a table, your work will be much easier.
   • Know the difference between dependent and independent variables. Independent variables are what you change. Dependent variables are things that change when the independent variable changes. In our example, accordingly, the independent variable will be “nitrogen content”, and the dependent variable will be the mass of the crop. All this data will fit well into the table in the appropriate columns.

4. Conduct the experiment methodically. Start your experiment and test the variable. In almost all cases where you need to measure multiple variables, you will have to run the experiment multiple times. So, we will grow identical corn plants and fertilize them with fertilizers with different nitrogen contents. And the wider the range of incoming data, the better. Record as much data as possible.

   • An integral part of any good experiment is the so-called “control sample”. So, one of your corn beds should have no variable of interest. Simply put, one bed needs to be fertilized with fertilizer that does not contain nitrogen. This will be a control sample - a kind of baseline, in comparison with which other beds will be studied.
   • When working with hazardous materials or performing hazardous activities, follow all safety requirements.

5. Collect data. Enter the data obtained during the experiment into the table as it becomes available - this will make it easier to work. Don't forget to indicate outlier values.

   • It will be very useful to visually represent the data, especially if such an opportunity exists. Place key points on the chart and indicate trends with a straight or italic line. This will help you and everyone else visualize patterns from the data. In the simplest experiments, the x-axis is data on the independent variables, and the y-axis is data on the dependent variables.

6. Analyze the data and draw a conclusion. Was the hypothesis correct? What trends can be identified based on the observed data? Did you encounter anything unexpected during the experiment? Do you have any unanswered questions that could form the basis for your next experiment? When evaluating the results, try to answer all of these questions. If your data does not allow you to give a clear answer regarding the truth of the hypothesis, then conduct additional experiments and collect even more data.

   Part 2

   Conducting an experiment

   1. Choose a topic and identify the variables. Let's take a small and simple experiment as an example. Let's say we are exploring how the use of different aerosols affects the flight distance of a projectile in potato shooters!

      • So, the type of aerosol used is an independent variable, but the length of the projectile's flight is a dependent variable.
      • There are still some things to think about. So, you need to make sure that the rounds are the same weight, and you also need to make sure that each shot consumes the same amount of aerosol. Why? Both of these parameters can affect the projectile's flight distance. Therefore, weigh all the projectiles and try to ensure that the shots consume the same amount of aerosol.

   2. Make a hypothesis. So, we took several types of aerosols (hair spray, cooking spray and spray paint). Let's say there is more butane in hair spray than in other sprays. Since we know that butane is a flammable gas, we can hypothesize that the hair spray will push the projectile the farthest. So, the hypothesis: “A higher concentration of butane in an aerosol (hair spray) will lead to the fact that the average static distance covered by a projectile weighing 250-300 g after a shot will exceed similar distances when shooting using other aerosols.”

   3. Organize your data collection process in advance. In our experiment, we will test all aerosols 10 times, after which we will display the average result. An aerosol that does not contain butane will be used as a control sample. In preparation for the experiment, you will assemble the potato shooter, make sure it works, purchase sprays and weigh the potatoes... that is, the projectiles.

      • And this is what a table for recording data will look like, which will have 5 columns:
        • The first column is the test number. The cells in this column will contain the serial number of the test, from 1 to 10.
        • The next four columns will be labeled with the names of the aerosols used. In the cells of each column the distance that the projectile will fly after being fired will be recorded.
        • Under each of these four columns, you should leave some space to write the average.

      • Draw conclusions. Once the results are analyzed, you can safely say that the hypothesis you put forward was correct. Plus, you'll also be able to say that you've discovered something unexpected - that cooking spray produces the most consistent results. You can also report problems you encountered during the experiment - for example, that their spray paint coated the barrel of the potato gun, making each subsequent shot difficult. And finally, you can make recommendations on what issues deserve further study - it is possible that more fuel used will give a better result.

        • Share your discoveries with the world! Find a publication or format in which it will be most appropriate to present the results of your research to an admiring world - and go ahead!
   • Have fun, but don't forget about safety.
   • Science is a game of “ask the hard question.” Don't be afraid to ask difficult questions regarding unexplored topics.

Hundreds of thousands of physical experiments have been carried out over the thousand-year history of science. It is difficult to select a few of the “best.” Among physicists in the USA and Western Europe a survey was conducted. Researchers Robert Kreese and Stoney Book asked them to name the most beautiful in history. physical experiments. He spoke about the experiments included in the top ten according to the results of a sample survey by Kriz and Book scientist Laboratory of High Energy Neutrino Astrophysics, Candidate of Physical and Mathematical Sciences Igor Sokalsky.

1. Experiment of Eratosthenes of Cyrene

One of the oldest known physical experiments, as a result of which the radius of the Earth was measured, was carried out in the 3rd century BC by the librarian of the famous Library of Alexandria, Erastothenes of Cyrene. The experimental design is simple. At noon, on the day of the summer solstice, in the city of Siena (now Aswan), the Sun was at its zenith and objects did not cast shadows. On the same day and at the same time, in the city of Alexandria, located 800 kilometers from Siena, the Sun deviated from the zenith by approximately 7°. This is about 1/50 of a full circle (360°), which means that the circumference of the Earth is 40,000 kilometers and the radius is 6,300 kilometers. It seems almost incredible that the radius of the Earth measured by such a simple method turned out to be only 5% less than the value obtained by the most accurate modern methods, reports the website “Chemistry and Life”.

2. Galileo Galilei's experiment

In the 17th century, the dominant point of view was Aristotle, who taught that the speed at which a body falls depends on its mass. The heavier the body, the faster it falls. Observations that each of us can make in Everyday life, would seem to confirm this. Try to release it at the same time light hands a toothpick and a heavy stone. The stone will touch the ground faster. Such observations led Aristotle to the conclusion about the fundamental property of the force with which the Earth attracts other bodies. In fact, the speed of falling is affected not only by the force of gravity, but also by the force of air resistance. The ratio of these forces for light objects and for heavy ones is different, which leads to the observed effect.

The Italian Galileo Galilei doubted the correctness of Aristotle's conclusions and found a way to test them. To do this, he dropped a cannonball and a much lighter musket bullet from the Leaning Tower of Pisa at the same moment. Both bodies had approximately the same streamlined shape, therefore, for both the core and the bullet, the air resistance forces were negligible compared to the forces of gravity. Galileo found that both objects reach the ground at the same moment, that is, the speed of their fall is the same.

The results obtained by Galileo are a consequence of the law of universal gravitation and the law according to which the acceleration experienced by a body is directly proportional to the force acting on it and inversely proportional to its mass.

3. Another Galileo Galilei experiment

Galileo measured the distance that balls rolling on an inclined board covered in equal intervals of time, measured by the author of the experiment using a water clock. The scientist found that if the time was doubled, the balls would roll four times further. This quadratic relationship meant that the balls moved at an accelerated rate under the influence of gravity, which contradicted Aristotle's assertion, which had been accepted for 2000 years, that bodies on which a force acts move at a constant speed, whereas if no force is applied to the body, then it is at rest. The results of this experiment by Galileo, like the results of his experiment with the Leaning Tower of Pisa, later served as the basis for the formulation of the laws of classical mechanics.

4. Henry Cavendish's experiment

After Isaac Newton formulated the law of universal gravitation: the force of attraction between two bodies with masses Mit, separated from each other by a distance r, is equal to F=γ (mM/r2), it remained to determine the value of the gravitational constant γ - To do this, it was necessary to measure the force attraction between two bodies with known masses. This is not so easy to do, because the force of attraction is very small. We feel the force of gravity of the Earth. But it is impossible to feel the attraction of even a very large mountain nearby, since it is very weak.

A very subtle and sensitive method was needed. It was invented and used in 1798 by Newton's compatriot Henry Cavendish. He used a torsion scale - a rocker with two balls suspended on a very thin cord. Cavendish measured the displacement of the rocker arm (rotation) as other balls of greater mass approached the scales. To increase sensitivity, the displacement was determined by light spots reflected from mirrors mounted on the rocker balls. As a result of this experiment, Cavendish was able to quite accurately determine the value of the gravitational constant and calculate the mass of the Earth for the first time.

5. Jean Bernard Foucault's experiment

French physicist Jean Bernard Leon Foucault experimentally proved the rotation of the Earth around its axis in 1851 using a 67-meter pendulum suspended from the top of the dome of the Parisian Pantheon. The swing plane of the pendulum remains unchanged in relation to the stars. An observer located on the Earth and rotating with it sees that the plane of rotation is slowly turning in the direction opposite to the direction of rotation of the Earth.

6. Isaac Newton's experiment

In 1672, Isaac Newton performed a simple experiment that is described in all school textbooks. Having closed the shutters, he made a small hole in them through which a ray of sunlight passed. A prism was placed in the path of the beam, and a screen was placed behind the prism. On the screen, Newton observed a “rainbow”: a white ray of sunlight, passing through a prism, turned into several colored rays - from violet to red. This phenomenon is called light dispersion.

Sir Isaac was not the first to observe this phenomenon. Already at the beginning of our era, it was known that large single crystals of natural origin have the property of decomposing light into colors. The first studies of light dispersion in experiments with a glass triangular prism, even before Newton, were carried out by the Englishman Hariot and the Czech naturalist Marzi.

However, before Newton, such observations were not subjected to serious analysis, and the conclusions drawn on their basis were not cross-checked by additional experiments. Both Hariot and Marzi remained followers of Aristotle, who argued that differences in color were determined by differences in the amount of darkness “mixed” with white light. Violet color, according to Aristotle, occurs when darkness is added to the greatest amount of light, and red - when darkness is added to the least amount. Newton carried out additional experiments with crossed prisms, when light passed through one prism then passes through another. Based on the totality of his experiments, he concluded that “no color arises from white and black mixed together, except the dark ones in between.”

the amount of light does not change the appearance of the color.” He showed that white light should be considered as a compound. The main colors are from purple to red.

This Newton experiment serves wonderful example how different people, observing the same phenomenon, interpret it differently and only those who question their interpretation and carry out additional experiments come to the correct conclusions.

7. Thomas Young's experiment

Until the beginning of the 19th century, ideas about the corpuscular nature of light prevailed. Light was considered to consist of individual particles - corpuscles. Although the phenomena of diffraction and interference of light were observed by Newton (“Newton’s rings”), the generally accepted point of view remained corpuscular.

Looking at the waves on the surface of the water from two thrown stones, you can see how, overlapping each other, the waves can interfere, that is, cancel out or mutually reinforce each other. Based on this, the English physicist and physician Thomas Young conducted experiments in 1801 with a beam of light that passed through two holes in an opaque screen, thus forming two independent light sources, similar to two stones thrown into water. As a result, he observed an interference pattern consisting of alternating dark and white fringes, which could not be formed if light consisted of corpuscles. The dark stripes corresponded to areas where light waves from the two slits cancel each other out. Light stripes appeared where light waves were mutually reinforcing. Thus, the wave nature of light was proven.

8. Klaus Jonsson's experiment

German physicist Klaus Jonsson conducted an experiment in 1961 similar to Thomas Young's experiment on the interference of light. The difference was that instead of rays of light, Jonsson used beams of electrons. He obtained an interference pattern similar to what Young observed for light waves. This confirmed the correctness of the provisions of quantum mechanics about the mixed corpuscular-wave nature of elementary particles.

9. Robert Millikan's experiment

The idea that the electric charge of any body is discrete (that is, consists of a larger or smaller set of elementary charges that are no longer subject to fragmentation) arose at the beginning of the 19th century and was supported by such famous physicists as M. Faraday and G. Helmholtz. The term “electron” was introduced into the theory, denoting a certain particle - the carrier of an elementary electric charge. This term, however, was purely formal at that time, since neither the particle itself nor the elementary electric charge associated with it had been discovered experimentally. In 1895, K. Roentgen, during experiments with a discharge tube, discovered that its anode, under the influence of rays flying from the cathode, was capable of emitting its own X-rays, or Roentgen rays. In the same year, French physicist J. Perrin experimentally proved that cathode rays are a stream of negatively charged particles. But, despite the colossal experimental material, the electron remained a hypothetical particle, since there was not a single experiment in which individual electrons would participate.

American physicist Robert Millikan developed a method that has become a classic example of an elegant physics experiment. Millikan managed to isolate several charged droplets of water in space between the plates of a capacitor. Illuminating x-rays, it was possible to slightly ionize the air between the plates and change the charge of the droplets. When the field between the plates was turned on, the droplet slowly moved upward under the influence of electrical attraction. When the field was turned off, it lowered under the influence of gravity. By turning the field on and off, it was possible to study each of the droplets suspended between the plates for 45 seconds, after which they evaporated. By 1909, it was possible to determine that the charge of any droplet was always an integer multiple of the fundamental value e (electron charge). This was convincing evidence that electrons were particles with the same charge and mass. By replacing droplets of water with droplets of oil, Millikan was able to increase the duration of observations to 4.5 hours and in 1913, eliminating one by one possible sources of error, he published the first measured value of the electron charge: e = (4.774 ± 0.009)x 10-10 electrostatic units .

10. Ernst Rutherford's experiment

By the beginning of the 20th century, it became clear that atoms consist of negatively charged electrons and some kind of positive charge, due to which the atom remains generally neutral. However, there were too many assumptions about what this “positive-negative” system looks like, while there was clearly a lack of experimental data that would make it possible to make a choice in favor of one or another model. Most physicists accepted J. J. Thomson's model: the atom as a uniformly charged positive ball with a diameter of approximately 108 cm with negative electrons floating inside.

In 1909, Ernst Rutherford (assisted by Hans Geiger and Ernst Marsden) conducted an experiment to understand the actual structure of the atom. In this experiment, heavy positively charged alpha particles moving at a speed of 20 km/s passed through thin gold foil and were scattered on gold atoms, deviating from the original direction of motion. To determine the degree of deviation, Geiger and Marsden had to use a microscope to observe the flashes on the scintillator plate that occurred where the alpha particle hit the plate. Over the course of two years, about a million flares were counted and it was proven that approximately one particle in 8000, as a result of scattering, changes its direction of motion by more than 90° (that is, turns back). This could not possibly happen in Thomson’s “loose” atom. The results clearly supported the so-called planetary model of the atom - a massive tiny nucleus measuring about 10-13 cm and electrons rotating around this nucleus at a distance of about 10-8 cm.

Modern physical experiments are much more complex than experiments of the past. In some, devices are placed over areas of tens of thousands of square kilometers, in others they fill a volume of the order of a cubic kilometer. And still others will soon be carried out on other planets.

Experiment as a process scientific knowledge

1. Experiment as a method of scientific research.

2. Types of experiments and their characteristics.

Experiment as a research method.

An experiment is an action aimed at creating conditions in order to reproduce a particular phenomenon.

When conducting research, the term “experiment” includes: setting up experiments and observing the phenomenon under study under certain conditions, which make it possible to monitor the progress of its development and recreate it each time these conditions are repeated. That is, the experiment must be characterized by a certain constancy (const).

The purpose of the experiment is to identify the properties of the studied objects and phenomena; testing the validity of hypotheses and in-depth study of the topic of scientific research.

The purpose of the experiment determines its setting and organization. The differences between the experiments are based on:

1) ways to create conditions(natural and artificial);

2) research objectives(forming, transforming, ascertaining, controlling, searching, deciding);

3) organization of(laboratory, field, natural, industrial...).

4) way of setting tasks(closed and open);

5) structure of the studied objects and phenomena(simple, complex);

6) character external influences to the research object(material, energy, information);

7) the nature of the interaction of the means experimental research (regular, model);

8) models that are studied in the experiment(material, mental);

9) controlled quantities(active, passive);

10) number of variable factors(unifactorial, multifactorial);

11) characterized objects or phenomena(technological, sociometric, etc.).

Types of experiments and their characteristics

(on the left is the group number, which includes different types of experiments; see above).

1. Natural experiment. Involves conducting research in natural conditions existence of the object of research (in mental, pedagogical, social and biological sciences).

Artificial experiment provides for the creation artificial conditions to conduct research (used in natural and technical sciences).

2. Transformative experiment assumes that the researcher deliberately creates conditions that, in his opinion, should contribute to the formation of new properties and qualities of the object.

Ascertaining experiment is used to test certain assumptions (the presence of a certain connection between the influence on the object of the researcher and its results is stated) and the presence of certain facts is revealed.

Control experiment involves monitoring the results of external influences on the object of study, taking into account its condition, the nature of the influence and the expected effect.

Search experiment used when it is difficult to classify factors influencing the study of phenomena if there is no sufficient preliminary data. Its result is the identification of significant factors and the elimination of insignificant ones.

The decisive experiment– is carried out to check the validity of the main provisions of fundamental theories, if two or more hypotheses are equally consistent with many phenomena. It leads to the establishment of the correctness of one of the hypotheses put forward and points to facts that contradict the other (others). The experiment being solved is based on a series of experiments.

3.Laboratory experiment held in laboratory conditions using standard instruments, special modeling installations, equipment, etc. As a rule, in a laboratory experiment it is not the object itself that is studied, but its model (sample).

Its disadvantage is that it does not always completely reproduce (model) the real course of the studied process and, therefore, requires a natural experiment.

Natural experiment comes down to conducting scientific research in natural conditions and on real objects. Depending on the location of the tests, a natural experiment can be carried out in production (industrial), in the field (field), at a testing ground (test site), semi-natural, etc.

The purpose of a natural experiment is to ensure the necessary correspondence (adequacy) of the experimental conditions to the real situation in which the created object will work in the future.

4. Open experiment involves an open explanation to the subject of the tasks of this experiment. This activates the behavior of the subjects and contributes to “support” of the planned work.

A closed experiment involves hiding the objectives of the experiment from the subjects in order to obtain objective data. It is carefully masked, which eliminates excessive self-control on the part of the subjects and allows them to exhibit behavioral reactions naturally.

5. Simple experiment used to study objects that do not have an entertaining structure, with a small number of interconnected and interacting elements that perform simple functions.

Complex experiment objects and phenomena with a complex branched structure are studied (a large number of interconnected and interdependent elements that perform complex functions). This results in concomitant changes in the state of the element(s) or the connection(s) between them.

6. Substance experiment involves the study of various material factors on the state of the object of study, i.e. the influence of something on something.

Energy experiment used to study the effects of various types of energy on the object of study (for natural sciences).

Information experiment involves the study of the impact of certain information on the object of research (in biology, psychology, cybernetics, sociology), i.e., a change in the state of the object of research under the influence of the information that is communicated to it.

7. Ordinary experiment (classical) offers direct interaction of experimental means with the object of research, which is an intermediary between the experimenter and the object of research.

Model experiment deals with a model, which, as a rule, is part of the expert installation, replacing the object of study and often the conditions for studying this object.

Flaw– difference between model and real object may become a source of errors; studying the behavior of a model on a modeling object requires additional costs and theoretical justification.

8. Material experiment(material research objects are used). represents a form of objective material connection of consciousness with the outside world.

Thought experiment(idealized, imaginary) represents one of the forms of mental activity of the cognitive subject, during which the structure of a real experiment is produced in the imagination.

The means of a thought experiment are mental models of the objects or phenomena being studied. For example, iconic models, figurative models, figurative-sign models.

It is used in pedagogy, artistic creativity, medicine, etc.

9. Active experiment is associated with the selection of special input signals (factors) and is designed to control the input and output of the research system.

Passive experiment provides for a change only in selected indicators (parameters) as a result of monitoring the object without artificial interference in its functioning and is accompanied by instrumental measurement of selected indicators of the state of the object of study. For example, monitoring changes in a person’s age, the number of diseases, birth rates, etc.

10. One-factor experiment involves identifying the necessary factors, stabilizing the factors that interfere with the research and alternately varying the factors that are of interest for the study.

Multivariate experiment– all factors (variables) are varied all at once and each effect is assessed based on the results of all experiments in a given series of experiments.

Home experiments for 4-year-old children require imagination and knowledge of the simple laws of chemistry and physics. “If these sciences were not taught very well at school, you will have to make up for lost time,” many parents will think. This is not so, experiments can be very simple, not requiring special knowledge, skills and reagents, but at the same time explaining the fundamental laws of nature.

Experiments for children at home will help to practical example explain the properties of substances and the laws of their interaction, will awaken interest in independent exploration of the world around us. Interesting physical experiments They will teach children to be observant, help them think logically, establishing patterns between ongoing events and their consequences. Perhaps the kids will not become great chemists, physicists or mathematicians, but they will forever retain warm memories of parental attention in their souls.

From this article you will learn

Unfamiliar paper

Kids like to make appliqués out of paper and draw pictures. Some 4-year-old children learn the art of origami with their parents. Everyone knows that paper is soft or thick, white or colored. What can an ordinary person do? White list paper, if you experiment with it?

An animated paper flower

Cut out a star from a sheet of paper. Its rays bend inward in the form of a flower. Fill a cup with water and lower the star onto the surface of the water. After some time, the paper flower, as if alive, will begin to open. The water will wet the cellulose fibers that make up the paper and spread them out.

Strong bridge

This paper experiment will be interesting for children 3 years old. Ask the kids how to place an apple in the middle of a thin sheet of paper between two glasses so that it does not fall. How can you make a paper bridge strong enough to support the weight of an apple? We fold a sheet of paper into an accordion shape and place it on the supports. Now it can support the weight of the apple. This can be explained by the fact that the shape of the structure has changed, which made the paper strong enough. The properties of materials that become stronger depending on their shape are the basis for the designs of many architectural creations, for example, the Eiffel Tower.

An animated snake

Scientific evidence of movement warm air upward can be brought with the help of simple experience. A snake is cut out of paper by cutting a circle in a spiral. You can revive a paper snake very simply. A small hole is made in her head and suspended by a thread above a heat source (battery, heater, burning candle). The snake will begin to rotate quickly. The reason for this phenomenon is the upward warm flow of air, which unwinds the paper snake. This is exactly how you can make paper birds or butterflies, beautiful and colorful, by hanging them under the ceiling in your apartment. They will rotate from the movement of air, as if flying.

Who is stronger

This fun experiment will help you determine which paper shape is stronger. For the experiment you will need three sheets of office paper, glue and several thin books. A cylindrical column is glued from one sheet of paper, a triangular column from another, and a rectangular column from the third. They place the “columns” vertically and test them for strength, carefully placing books on top. As a result of the experiment, it turns out that the triangular column is the weakest, and the cylindrical column is the strongest - it will withstand the greatest weight. It is not for nothing that columns in churches and buildings are made in a cylindrical shape; the load on them is distributed evenly over the entire area.

Amazing salt

Regular salt is found in every home today; no meal can be prepared without it. You can try making beautiful children's crafts from this affordable product. All you need is salt, water, wire and a little patience.

Salt has interesting properties. It can attract water to itself, dissolving in it, thereby increasing the density of the solution. But in a supersaturated solution, the salt again turns into crystals.

To conduct an experiment with salt, bend a beautiful symmetrical snowflake or other figure from a wire. Dissolve salt in a jar of warm water until it stops dissolving. Dip a bent wire into a jar and place it in the shade for several days. As a result, the wire will become overgrown with salt crystals, and will look like a beautiful ice snowflake that will not melt.

Water and ice

Water exists in three states of aggregation: steam, liquid and ice. The purpose of this experiment is to introduce children to the properties of water and ice and compare them.

Pour water into 4 ice trays and place them in the freezer. To make it more interesting, you can tint the water with different dyes before freezing. Poured into a cup cold water, and throw two ice cubes there. Simple ice boats or icebergs will float on the surface of the water. This experiment will prove that ice is lighter than water.

While the boats are floating, the remaining ice cubes are sprinkled with salt. They'll see what happens. Through a short time, before the indoor float in the cup has time to sink (if the water is quite cold), the cubes sprinkled with salt will begin to crumble. This is explained by the fact that the freezing point of salt water is lower than normal water.

Fire that doesn't burn

In ancient times, when Egypt was powerful country, Moses fled from the wrath of Pharaoh and tended his flocks in the desert. One day he saw a strange bush that was burning and did not burn. It was a special fire. Can objects that are engulfed in ordinary flame remain safe and sound? Yes, this is possible, this can be proven through experience.

For the experiment you will need a sheet of paper or a banknote. A tablespoon of alcohol and two tablespoons of water. The paper is moistened with water so that the water is absorbed into it, alcohol is poured on top and set on fire. Fire appears. This is burning alcohol. When the fire goes out, the paper will remain intact. The experimental result can be explained very simply - the combustion temperature of alcohol, as a rule, is not enough to evaporate the moisture with which the paper is impregnated.

Natural indicators

If your child wants to feel like a real chemist, you can make special paper for him that will change color depending on the acidity of the environment.

The natural indicator is prepared from the juice of red cabbage, which contains anthocyanin. This substance changes color depending on what liquid it comes into contact with. In an acidic solution, paper soaked in anthocyanin will turn yellow, in a neutral solution it will turn green, and in an alkaline solution it will turn blue.

To prepare a natural indicator, take filter paper, a head of red cabbage, cheesecloth and scissors. Chop the cabbage thinly and squeeze the juice through cheesecloth, squeezing it with your hands. Soak a sheet of paper in juice and dry. Then cut the made indicator into strips. The child can dip the paper into four different liquids: milk, juice, tea or soap solution, and watch how the color of the indicator changes.

Electrification by friction

In ancient times, people noticed the special ability of amber to attract light objects if rubbed woolen fabric. They did not yet have knowledge about electricity, so they explained this property by the spirit living in the stone. Exactly from Greek name amber - electron and the word electricity originated.

Such amazing properties not only amber has. You can conduct a simple experiment to see how a glass rod or plastic comb attracts small pieces of paper. To do this, rub the glass with silk and the plastic with wool. They will begin to attract small pieces of paper that will stick to them. Over time, this ability of items will disappear.

You can discuss with children that this phenomenon occurs due to electrification by friction. If fabric rubs quickly against an object, sparks may appear. Lightning in the sky and thunder are also a consequence of friction of air currents and the occurrence of electrical discharges in the atmosphere.

Solutions of different densities - interesting details

Get a colorful rainbow in a glass of liquids different colors You can prepare the jelly and pour it layer by layer. But there is a simpler way, although not as tasty.

To carry out the experiment you will need sugar, vegetable oil plain water and dyes. Concentrated sweet syrup is prepared from sugar, and clean water is colored with dye. Poured into a glass sugar syrup, then carefully along the wall of the glass so that the liquids do not mix, pour clean water, and at the end add vegetable oil. The sugar syrup should be cold and the colored water should be warm. All liquids will remain in the glass like a small rainbow, without mixing with each other. The thickest sugar syrup will be at the bottom, the water will be at the top, and the lightest oil will be on top of the water.

Color explosion

Another interesting experiment can be done using different densities of vegetable oil and water, creating a color explosion in the jar. For the experiment you will need a jar of water, a few tablespoons of vegetable oil, and food coloring. In a small container, mix several dry food colors with two tablespoons of vegetable oil. Dry grains of dyes do not dissolve in oil. Now the oil is poured into a jar of water. Heavy grains of dye will settle to the bottom, gradually freeing themselves from the oil, which will remain on the surface of the water, forming colored swirls, as if from an explosion.

Home volcano

Useful geographic knowledge may not be so boring for a four-year-old if you provide a visual demonstration of a volcano erupting on an island. To carry out the experiment you will need baking soda, vinegar, 50 ml of water and the same amount of detergent.

Small a plastic cup or the bottle is placed in the mouth of a volcano, sculpted from colored plasticine. But first, baking soda is poured into a glass, water tinted red and detergent are poured. When the improvised volcano is ready, a little vinegar is poured into its mouth. A rapid foaming process begins due to the fact that soda and vinegar react. “Lava” formed by red foam begins to pour out of the volcano’s mouth.

Experiments for 4-year-old children, as you have seen, do not require complex reagents. But they are no less fascinating, especially with interesting story about the reason for what is happening.