The 10 most beautiful experiments in history

Scientific experiments are now often complicated, can only be done by a research team, at a cost of up to millions of dollars. However, when asked about the "most beautiful " experiment in the history of science, people worshiped simple ideas.

Listed 10 most beautiful experiments in history

Recently, Dr. Robert Crease, of the Department of Philosophy of New York University (USA), made a survey of scientists about "the most beautiful experiment in history ". As a result, not the modern and complex experiments (in terms of gene analysis, subatomic particles or light measurements of distant stars .) were chosen as "the most beautiful ", but the experiments themselves. It is as simple as measuring the circumference of the earth, scattering light, falling objects . most loved by people. This beauty has a very classical meaning: simple, simple logic model, but great results.

Below is the order of 10 experiments that are considered "most beautiful " (in chronological order).

1. Experiment to measure the earth's diameter of Eratosthenes

On a summer solstice about 2,300 years ago, in the city of Awan in Egypt , Eratosthenes determined the time when sunlight shone directly on the earth's surface. That means the shadow of a vertical stake coincides with the pile.

At the same time the following year, he measured the shadow of a stake set in Alexandria (Greece), and discovered that the sun was inclined at 7 degrees from the vertical.

Assuming that the earth is a sphere, its circumference corresponds to a 360 degree angle. If two cities (Awan and Alexandria) are separated by 7 degrees, that angle must correspond to the distance between the two cities (assuming that both cities are on the equator). Based on this connection, Eratosthenes calculated the earth's circumference of 250,000 stadia.

Until now, it was not known exactly how many meters of 1 stadia in Greek standards (probably the length of a stadium?), So there was no conclusion about the accuracy of Eratosthenes' experiment. However, his method is logically logical. It shows that Eratosthenes not only knew the spherical earth , but also understood its movement around the sun.

The experiment was ranked seventh in the " Best Experimental Ranking " table by Robert Crease.

2. Experiment on Galilei's free fall

In the late 16th century, it was believed that heavy objects fell faster than light objects. The reason is that Aristotle said so, and that view is recognized by the Church.

However Galileo Galilei , a mathematics teacher at the University of Pisa (Italy), believes in something different. His free-fall experiment has become a classic story in science: He climbed up the leaning tower in Pisa to drop objects of varying mass on the ground, and concluded that they fell with speed. The same degree! (of course the resistance of the air must be ignored). Because of this conclusion, he was fired. He became a shining example for later researchers, for pointing out that: One can only draw scientific knowledge from the objective laws of nature, not from faith.

The experiment stood at No. 2 in Robert Crease's " chart. "

3. Experiments on marbles rolling on the slope of Galilei

Once again, Galileo Galilei had an experiment that was included in the " Top 10 Best Experiments ". To verify a quantity called acceleration , Galilei designed a board measuring 5.5 meters long and 0.22 meters wide. After that, he cut a groove in the middle of the board .

Galilei set up the sloping board, then released the bronze balls into the groove. After that, he used a water meter to measure the time the marble moved over a certain distance (Galilei measured the marbles' path and weighed the number of water due to the small clock to deduce the ratio of the road). go and time of moving objects).

Galilei discovered that, the lower the slope, the faster the marbles run: The distance is proportional to the square of the travel time. The reason is that pellets are always affected by an acceleration (caused by the gravitational pull of the earth). This is the free acceleration (g = 9.8 m / s ² ).

The experiment was ranked 8th in Robert Crease's " rankings ".

4. Experiment on Newton's " light scattering "

Before Newton, it was assumed that light was a pure, indivisible body (Aristotle!). However, Newton pointed out this mistake, when he used a prism to separate sunlight into different colors and then projected it on the wall.

Newton's experiment showed that white light is not " pure ", but that it is a synthesis of a spectrum of 7 primary colors: red, orange, yellow, green, blue, indigo, violet .

Newton's experiment of " light scattering " was ranked 4th in Robert Crease's " rankings ".

5. Experiment on Cavendish's " twisted rope "

We all know that Newton is the one who finds gravity. He showed that two objects always attract each other by a force proportional to mass and inversely proportional to the square of the distance between them. However, how to show others the gravity by experiment (because it is too weak)?

At the end of the 18th century, British scientist Henry Canvadish did such a sophisticated experiment: He attached two metal marbles to the ends of a wooden stick, then used a thin string to hang the whole system, so that the wooden bar is horizontal. After that, Cavendish used two fuses, each weighing 170 kg, approached almost two balls at the ends. Hypothetically, the gravitational force of two fuses that apply to two marbles will cause the stick to rotate in a small angle, and the rope will be twisted a few times.

Cavendish experiment: Gravity will cause the stick to rotate in one corner and the rope twists.

As a result, Canvadish's experiments are built so sophisticatedly that they reflect almost exactly the value of gravity. He also calculated a gravitational constant approximating the constant we know today. Even Canvadish uses this experimental principle to calculate the earth's mass of 60x1020kg.

The experiment was ranked 6th in " Top 10 Beautiful Experiments ".

6. Young's experiment on light interference

For years, Newton led scientists into a wrong path when he thought that light was made of particles and not waves. However, in 1803, British physicist Thomas Young countered Newton's point of view with the following experiment:

Young cut a hole in the glass door, then covered it with a thick piece of paper, with a small hole like a needle. After that, Young used a mirror to deflect the direction of the thin ray of light shining through the small hole of the piece of paper. Next, he used a very thin piece of cardboard (0.1 millimeter in size) placed in the middle of the light ray to separate it into two. When these two rays of light shine on the wall, Young realizes that there are light and dark spots intertwined. This is clearly the interference phenomenon of light (the bright spot is where the two peaks intersect, and the dark spot is where a wave peak interferes with a wave of waves to cancel each other). Thus, the light must be waves .

(Photo: magnet.fsu.edu)

The experiment was ranked 5th in " Top 10 Beautiful Experiments ".

7. Experiment on "the Pathéon church pendulum"

In the nineteenth-century scientific achievements, there was probably no more shocking event than the " Pathéon church pendulum " experiment, conducted by French scientist Jean-Bernard-Léon Foucault. With this experiment, Foucault showed that the earth rotates around its axis.

In 1851, Foucault used a 68-meter-long steel wire to hang a 31-kilogram iron bridge on the roof of Pathéon church in Paris. After that, he used an initial force to push the ball to shake it again and again.

At the bottom of the sphere, Foucault attaches a small needle. Every time the pendulum moves, the needle streaks up on the wet sand that people have spread on the previous church.

Before the eyes of the viewers, the streak of metal that the ball left on the sand constantly changed after each time the ball shook and shook. Although the speed of change was very slow, but after about 30 hours, the pendulum changed direction in a clockwise direction. With this result, Foucault was the first to point out by experimenting that the earth rotates around its axis.

(Photo: physik.uni-konstanz.de)

Paris is in the north, so the pendulum has moved clockwise. If the experiment is done in the south, the pendulum will move counterclockwise. The time for the pendulum's rotation to go all the way around also depends on the geographical area, like in Paris it is 30 hours, and in Antarctica it is 24 hours. Particularly in the equator, the rotating axis of the pendulum will not move.

The experiment was ranked 10th in Robert Crease's " chart ".

8. Millikan oil droplet experiment

Before the 17th century, people had known electrical phenomena, such as the discharge of clouds, or the charge generated by friction between two objects. However, it was not until 1897 that British physicist JJ Thomson discovered a charged particle, called an electron. However, even Thomson did not determine the charge value of the electron.

In 1909, American physicist Robert Millikan did a famous experiment called "oil-drop experiment." In this experiment, Millikan placed a very large voltage (about 10,000 V) between two metal electrodes. Later, he used a sprayer, dropping free drops of oil between the two electrodes.

(Photo: juliantrubin)

Initially, the oil droplet was not charged, so it fell under the influence of gravity. However, Millikan used a beam to ionize the oil drop, giving it a charge. Therefore, this drop of oil has fallen faster, because in addition to gravity, it also has the effect of electric fields. Based on the difference in time when two drops of oil fall along the same line, Millikan calculated that the charge of a charged particle is at least 1 electron: e = 1.63 · 10-19 As.

In 1917 Millikan repeated the experiment, and corrected the charge of an electron, e = 1.59 · 10-19 As. Current measurements based on Millikan's principle result in e = 1,602 · 10-19 As.

Oil-drop experiment was ranked 3rd in Robert Grease's " chart ".

9. Experiments on the radiation of alpha particles

Before Ernest Rutherford conducted an experiment on alpha particle radiation at the University of Manchester in 1911, it was mistakenly assumed that atoms had a " soft " structure: consisting of positively charged particles interwoven with electron, forming a " plum pudding " mixture.

But when Rutherford and his assistants conducted experiments to shoot alpha particles into thin gold leaves, they were surprised that one percent of alpha particles had responded. Obviously, if the atomic structure has a soft form such as " plum pudding " it would not be possible to have this feedback, but the alpha particles would be stuck to gold atoms, similar to when people throw a piece of powder Soft into a pot of jam cake. That shows that in an atomic structure, in addition to electrons, there must be a very hard nucleus. Rutherford concluded that most of the atomic mass must be concentrated in a tiny core called the nucleus, with other electrons moving around it on different orbits, in the middle of the spaces.

With changes from quantitative theories, Rutherford's atomic model is still valid.

(Photo: dss.go.th)

10. Interference phenomenon of two electron beams

In 1924, French physicist Louis de Broglie proposed that electrons and other matter particles also have wave properties such as wavelength and frequency. Later, there was an experiment on the wave properties of electrons made by Clinton Joseph Davisson and Lester Halbert Germer at Bells Laboratory.

To explain the idea to myself and others, physicists have repeated Young's experiment of light interference but changed the beam of light with an electron beam . By law, these lines of particles, after being split into two, interfere with each other, leaving bright and dark parts as seen in Young's light interference experiment.

Until now, it is still not known where the experiment was performed for the first time, and who was the author. According to Peter Rodger, scientific editor of Physics Today , the first time he read an article about this experiment was in 1961, and the author was physicist Claus Joensson at Tueblingen University (West Germany). ). However, perhaps the experiment was done before, but it was a time when people focused heavily on big science programs, and no one paid attention to it. Until people turned over the history of scientific experiments and felt the " beauty " of electron beams, they did not know who was the first to prove their wave count.