Very interesting facts about physics. Interesting facts about physics

If you connect regular headphones to the microphone input, they can be used as a microphone. In a simplified way, the design of the headphones and microphone is the same: the membrane is connected to a coil of wire located in the magnetic field of a permanent magnet. In headphones, during normal use, the current supplied to the coil is converted into vibrations of the membrane, and in a microphone, vice versa.

If you find yourself in a falling elevator, the best strategy to increase your chances of survival is to lie on your back and try to take up as much floor space as possible. In this case, the impact force will be distributed as much as possible over the surface of the body. A common belief is that you just need to jump during the impact, but this is a misconception and it is unlikely that anyone will be able to accurately guess the time of the collision and jump at the same speed as the elevator falls.

To look through glass with a matte surface, just stick a piece of transparent tape on it. Due to the unevenness of the frosted glass, the light is scattered, but the adhesive side of the tape smoothes out these unevenness, and as a result, the light passes through as if through ordinary glass. It should be added that if the surface is matte on both sides, this trick will no longer work.

There is an optical phenomenon that can be called an inverted rainbow, although it happens very rarely. Such a rainbow appears only when several conditions are met. In the sky at an altitude of 78 km there must be a thin curtain of cirrus clouds consisting of ice crystals, and sunlight must fall on them at a certain angle in order to be decomposed into a spectrum and reflected into the atmosphere. The colors in an upside down rainbow are also arranged in reverse: purple is at the top and red is at the bottom.

A bird sitting on a high-voltage power line does not suffer from the current because its body is a poor conductor of current. Where the bird's paws touch the wire, a parallel connection is created, and since the wire conducts electricity much better, a very small current flows through the bird itself, which cannot cause harm. However, as soon as the bird on the wire touches another grounded object, for example, a metal part of a support, it immediately dies, because then the air resistance is too great compared to the resistance of the body, and all the current flows through the bird.

If a boiled egg is spun on a smooth surface, it will quickly spin in a given direction and will spin for quite a long time, while a raw egg will stop much earlier. This happens because a hard-boiled egg rotates as a single whole, while a raw egg has liquid contents, loosely bound to the shell.

Many people during their school years considered physics a boring subject. But this is not at all true, because in real life everything happens precisely thanks to this science. This natural science can be looked at not only from the perspective of solving problems and creating formulas. Physics also studies the Universe in which man lives, and therefore living without knowing the rules of this Universe becomes uninteresting.

1. As you know from textbooks, water has no shape, but water still has its own shape. This is a ball.

2.Depending on weather conditions, the height of the Eiffel Tower can fluctuate by 12 centimeters. In hot weather, the beams heat up to 40 degrees and expand under the influence of high temperatures, which changes the height of the structure.

3.To feel weak currents, physicist Vasily Petrov had to remove the top layer of epithelium on the tip of his finger.

4.To understand the nature of vision, Isaac Newton inserted a probe into his eye.

5. An ordinary shepherd's whip is considered the first device to break the sound barrier.

6. You can see x-rays and visible glow if you unfold the tape in a vacuum space.

7.Einstein, known to everyone, was a poor student.

8.The body is not a good conductor of current.

9.The most serious branch of physics is considered nuclear.

10. A real nuclear reactor operated 2 billion years ago on the territory of Oklo. The reaction of the reactor continued for approximately 100,000 years and only when the uranium vein was depleted did it end.

11. The temperature on the surface of the Sun is 5 times lower than the temperature of lightning.

12. A drop of rain weighs more than a mosquito.

13. Insects that fly are oriented during the flight only towards the light of the Moon or the Sun.

14.The spectrum is formed when the sun's rays pass through droplets in the air.

15. Fluidity formed due to stress is characteristic of glaciers of large ice.

16. Light propagates more slowly in a transparent medium than in a vacuum.

17. There are no two snowflakes with the same pattern.

18.When ice forms, the crystal lattice begins to lose salt content, which causes ice and salt water to appear at some points in the downdrafts.

19.For his experiments, physicist Jean-Antoine Nollet used people as a material.

20. Without using a corkscrew, you can open a bottle by leaning a newspaper against the wall.

21.To escape from a falling elevator, you need to take a “lying down” position, while occupying the maximum floor area. This will distribute the impact force evenly throughout the body.

22.Air is not directly heated by the Sun.

23. Due to the fact that the Sun emits light in all ranges, it has a white color, although it appears yellow.

24. Sound travels faster where the medium is denser.

25. The noise of Niagara Falls is equivalent to the noise of a factory floor.

26.Water is capable of conducting electricity only with the help of ions that dissolve in it.

27.The maximum density of water is achieved at a temperature of 4 degrees.

28. Almost all oxygen in the atmosphere is of biological origin, but before the emergence of photosynthetic bacteria, the atmosphere was considered oxygen-free.

29.The first engine was a machine called aeolopile, which was created by the Greek scientist Heron of Alexandria.

30. 100 years after Nikola Tesla created the first radio-controlled ship, similar toys appeared on sale.

31.The Nobel Prize was prohibited from being received in Nazi Germany.

32. Short-wave components of the solar spectrum propagate in the air more strongly than long-wave components.

33. At a temperature of 20 degrees, water in the pipeline, which contains methane, can freeze.

34.The only freely occurring substance in the natural environment is water.

35.The Sun has the most water. The water there is in the form of steam.

36. It is not the water molecule itself that conducts the current, but the ions contained in it.

37.Only distilled water is a dielectric.

38.Each bowling ball has the same volume, but their mass is different.

39. In the water space you can observe the process of “sonoluminescence” - the transformation of sound into light.

40.The electron was discovered as a particle by English physicist Joseph John Thompson in 1897.

41.The speed of electric current is equal to the speed of light.

42.By connecting ordinary headphones to the microphone input, they can be used as a microphone.

43. Even with a very strong wind in the mountains, clouds can hang motionless. This occurs due to the fact that the wind moves air masses in a certain flow or wave, but at the same time various obstacles are flown around.

44. There are no blue or green pigments in the shell of the human eye.

45.To be able to look through glass that has a matte surface, you should stick a piece of transparent tape on it.

46.At a temperature of 0 degrees, water in its normal state begins to turn into ice.

47.In the Guinness beer drink, you can notice how the bubbles go down the walls of the glass instead of going up. This occurs because the bubbles in the center of the glass rise faster and push the liquid down at the rim with stronger viscous friction.

48.The phenomenon of an electric arc was first described by the Russian scientist Vasily Petrov in 1802.

49.The Newtonian viscosity of a liquid depends on the nature and temperature. But if the viscosity also depends on the velocity gradient, then it is called non-Newtonian.

50. In a freezer, hot water will freeze faster than cold water.

51. In 8.3 minutes, photons in outer space can reach the Earth.

52. About 3,500 terrestrial planets have been discovered to date.

53.All objects have the same falling speed.

54.If a mosquito is on the ground, then a drop of rain can kill it.

55. All objects that surround a person are made of atoms.

56.Glass is not considered a solid because it is a liquid.

57. Liquid, gaseous and solid bodies always expand when heated.

58. Lightning strikes approximately 6,000 times per minute.

59.If hydrogen burns in the air, water is formed.

60. Light has weight, but has no mass.

61. The moment a person strikes a match against a box, the temperature of the match head rises to 200 degrees.

62. During the process of boiling water, its molecules move at a speed of 650 meters per second.

63. At the tip of the needle in a sewing machine, pressure develops up to 5000 atmospheres.

64. There is a physicist in outer space who received an award for the most ridiculous discovery in science. This is Andrey Geim from Holland, who in 2000 was awarded for studying the levitation of frogs.

65. Gasoline does not have a specific freezing point.

66.Granite conducts sound 10 times faster than air.

67.White color reflects light, and black attracts it.

68. By adding sugar to water, the egg will not drown in it.

69.Clean snow will melt more slowly than dirty snow.

70. The magnet will not act on stainless steel because it does not have different proportions of nickel that interfere with the iron atoms.

Why doesn't a bird sitting on a wire die from electric shock?

A bird sitting on a high-voltage power line does not suffer from current, because its body is a poor conductor of current. Where the bird's paws touch the wire, a parallel connection is created, and since the wire conducts electricity much better, a very small current flows through the bird itself, which cannot cause harm. However, as soon as the bird on the wire touches another grounded object, for example, a metal part of a support, it immediately dies, because then the air resistance is too great compared to the resistance of the body, and all the current flows through the bird.

What kind of memory can metal alloys have?

Some metal alloys, such as nitinol (55% nickel and 45% titanium), have a shape memory effect. It lies in the fact that a deformed product made of such material, when heated to a certain temperature, returns to its original shape. This is due to the fact that these alloys have a special internal structure called martensite, which has the property of thermoelasticity. In the deformed parts of the structure, internal stresses arise, which tend to return the structure to its original state. Shape memory materials have found wide application in manufacturing - for example, for connecting bushings, which compress at very low temperatures and straighten at room temperature, forming a connection much more reliable than welding.

How did the Pauli effect prevent Pauli's hoax?

Scientists call the Pauli effect the failure of instruments and the unplanned course of experiments when famous theoretical physicists appear - for example, Nobel laureate Wolfgang Pauli. One day they decided to play a prank on him by connecting the wall clock in the hall where he was to give a lecture with the front door using a relay so that when the door was opened, the clock would stop. However, this did not happen - when Pauli entered, the relay suddenly failed.

What colored noises exist, besides white noise?

The concept of “white noise” is widely known - this is what they say about a signal with uniform spectral density at all frequencies and dispersion equal to infinity. An example of white noise is the sound of a waterfall. However, in addition to white, there are a large number of other colored noises. Pink noise is a signal whose density is inversely proportional to the frequency, and red noise has a density inversely proportional to the square of the frequency - they are perceived by ear as “warmer” than white noise. There are also concepts of blue, violet, gray noise and many others.

Which elementary particles are named after the sounds of ducks?

Murray Gell-Mann, who hypothesized that hadrons were made of even smaller particles, decided to call these particles the sound that ducks make. James Joyce’s novel “Finnegans Wake” helped him formulate this sound into a suitable word, namely the line: “Three quarks for Muster Mark!” Hence the particles received the name quarks, although it is not at all clear what meaning this previously non-existent word had for Joyce.

Why is the sky blue during the day and red during sunset?

Short-wave components of the solar spectrum are scattered in the air more strongly than long-wave components. This is why we see the sky as blue - because blue is at the short wavelength end of the visible spectrum. For a similar reason, during sunset or dawn, the sky on the horizon turns red. At this time, the light travels tangentially to the earth's surface, and its path through the atmosphere is much longer, as a result of which a significant part of the blue and green color leaves direct sunlight due to scattering.

What is the difference between the mechanism of lapping water in cats and dogs?

In the process of lapping, cats do not plunge their tongue into the water, but, lightly touching the surface with the curved tip, immediately pull it back up. In this case, a column of liquid is formed due to the subtle balance of gravity, which pulls the water down, and the force of inertia, which forces the water to continue moving upward. Dogs use a similar lapping mechanism - although it may seem to an observer that the dog is scooping up liquid with its tongue folded into a paddle, x-ray analysis has shown that this “spatula” unfolds inside the mouth, and the column of water created by the dog is similar to that of a cat.

Who holds both the Nobel and Ig Nobel Prizes?

Dutch physicist of Russian origin Andre Geim received the Nobel Prize in 2010 for experiments that helped study the properties of graphene. And 10 years earlier, he received an ironic Ig Nobel Prize for an experiment on diamagnetic levitation of frogs. Thus, Game became the first person in the world to hold both the Nobel and Ig Nobel Prizes.

Why are ordinary city streets dangerous for racing cars?

When a racing car is driven on a track, very low pressure can build up between its underbody and the road, enough to lift a manhole cover. This happened, for example, in Montreal in 1990 at a sports prototype race - a lid lifted by one of the cars hit the car behind it, which started a fire and the race was stopped. Therefore, now in all races of cars on city streets, the covers are welded to the rim of the hatch.

Why did Newton throw a foreign object into his eye?

Isaac Newton was interested in many aspects of physics and other sciences, and was not afraid to conduct some experiments on himself. He tested his guess that we see the world around us due to the pressure of light on the retina of the eye in the following way: he cut out a thin curved probe from ivory, launched it into his eye and pressed it on the back side of the eyeball. The resulting colored flashes and circles confirmed his hypothesis.

Why is the unit of measurement for both temperature and strength of alcoholic drinks called the same - degree?

In the 17th and 18th centuries, there was a physical theory about caloric - weightless matter found in bodies and causing thermal phenomena. According to this theory, more heated bodies contain more caloric than less heated ones, therefore temperature was defined as the strength of the mixture of body matter and caloric. That is why the unit of measurement for both temperature and strength of alcoholic drinks is called the same - degree.

Why were two German-American satellites named Tom and Jerry?

In 2002, Germany, together with the United States, launched a system of two space satellites to measure Earth's gravity called GRACE. They fly in the same orbit at an altitude of about 450 kilometers, one after another, with an interval of 220 kilometers. When the first satellite approaches an area of ​​high gravity, such as a large mountain range, it accelerates and moves away from the second satellite. And after some time, the second device flies here, also accelerates and thereby restores the original distance. For such a game of “catch-up,” the companions were given the names Tom and Jerry.

Why can't the American SR-71 Blackbird spy plane be fully refueled on the ground?

The American reconnaissance aircraft SR-71 Blackbird at normal temperatures has gaps in its skin. During flight, the skin heats up due to friction with the air, and the gaps disappear, and the fuel cools the skin. Because of this method, the plane cannot be refueled on the ground, because the fuel will leak out through those very cracks. Therefore, at first only a small amount of fuel is filled into the plane, and refueling takes place in the air.

Where can water freeze at +20 °C?

Water can freeze in a pipeline at a temperature of +20 °C if methane is present in this water (to be more precise, gas hydrate is formed from water and methane). Methane molecules “push apart” water molecules, as they occupy more volume. This leads to a decrease in internal water pressure and an increase in freezing temperature.

Whose Nobel medals were hidden from the Nazis in dissolved form?

In Nazi Germany, the Nobel Prize was banned after the Peace Prize was awarded to the opponent of National Socialism, Karl von Ossietzky, in 1935. German physicists Max von Laue and James Frank entrusted the custody of their gold medals to Niels Bohr. When the Germans occupied Copenhagen in 1940, the chemist de Hevesy dissolved these medals in aqua regia. After the end of the war, de Hevesy extracted the gold hidden in the aqua regia and donated it to the Royal Swedish Academy of Sciences. New medals were made there and re-presented to von Laue and Frank.

Which famous physicist was awarded the Nobel Prize in Chemistry?

Ernest Rutherford's research was primarily in the field of physics and once stated that "all sciences can be divided into two groups - physics and stamp collecting." However, he was awarded the Nobel Prize in chemistry, which came as a surprise to both him and other scientists. Subsequently, he noticed that of all the transformations that he was able to observe, “the most unexpected was his own transformation from a physicist to a chemist.”

Why do insects hit lamps?

Insects orient themselves in flight according to the light. They fix the source - the Sun or the Moon - and maintain a constant angle between it and their course, taking a position in which the rays always illuminate the same side. However, if the rays from celestial bodies are almost parallel, then from an artificial light source the rays diverge radially. And when an insect chooses a lamp for its course, it moves in a spiral, gradually approaching it.

How to distinguish a boiled egg from a raw one?

If you spin a boiled egg on a smooth surface, it will quickly spin in a given direction and will spin for quite a long time, while a raw egg will stop much earlier. This happens because a hard-boiled egg rotates as a single whole, while a raw egg has liquid contents, loosely bound to the shell. Therefore, when rotation begins, the liquid contents, due to the inertia of rest, lag behind the rotation of the shell and slow down the movement. Also, during rotation, you can briefly stop the rotation with your finger. For the same reasons, a boiled egg will stop immediately, but a raw egg will continue to spin after you remove your finger.

Why does a rainbow have an arc shape?

Sun rays passing through raindrops in the air are decomposed into a spectrum, since different colors of the spectrum are refracted in the drops at different angles. As a result, a circle is formed - a rainbow, part of which we see from the ground in the form of an arc, and the center of the circle lies on the straight line “The Sun is the eye of the observer.” If the light in the drop is reflected twice, you can see a secondary rainbow.

How is ice able to flow?

Ice is subject to fluidity - the ability to deform under stress determines the movement of ice in huge glaciers. Some Himalayan glaciers move at a speed of 2-3 meters per day.

Why can Asians and Africans carry weights on their heads?

Residents of Africa and Asia easily carry heavy loads on their heads. This is explained by the laws of physics. When walking, the human body rises and falls, thus expending energy on lifting the load. At the same time, the head rises and falls with a smaller vertical amplitude than the whole body, and this feature was developed through evolution: the brain was protected from concussion, while the springy spine with a double bend served as a spring.

Why can you increase the rate of freezing of water by pre-heating it?

In 1963, Tanzanian schoolboy Erasto Mpemba discovered that hot water freezes faster in the freezer than cold water. In honor of him, this phenomenon was called the Mpemba effect. Until now, scientists have not been able to accurately explain the cause of the phenomenon, and the experiment is not always successful: it requires certain conditions.

Why doesn't ice sink in water?

Water is the only freely occurring substance on Earth whose density in the liquid state is greater than in the solid state. Therefore, ice does not sink in water. It is thanks to this that reservoirs usually do not freeze to the bottom, although this is possible at extreme air temperatures.

What influences the direction in which the water swirls?

The Coriolis force, caused by the rotation of the Earth around its own axis, does not in any way affect the torsion of the water funnel in the bathtub. Its effect can be seen in the example of the twisting of air masses (clockwise in the southern hemisphere and counterclockwise in the northern), but this force is too small to spin a small and fast funnel. The direction in which the water rotates depends on other factors, such as the direction of the threads in the drain hole or the configuration of the pipes.

Who is considered the world's first programmer?

The world's first programmer was an Englishwoman, Ada Lovelace. In the mid-19th century, she drew up a plan of operations for the prototype of a modern computer - Charles Babbage's Analytical Engine, with the help of which it was possible to solve Bernoulli's equation, which expresses the law of conservation of energy of a moving fluid.

What particles can take a million years to rise from the Sun's core to its surface?

Light travels slower in a transparent medium than in a vacuum. For example, photons undergoing many collisions on their way from the solar core, which emits energy, can take about a million years to reach the surface of the Sun. However, moving in outer space, the same photons reach the Earth in just 8.3 minutes.

When was the Earth's gravitational field weakened?

On April 1, 1976, English astronomer Patrick Moore pranked listeners on BBC radio by announcing that at 9:47 a rare astronomical effect would occur: Pluto would pass behind Jupiter, enter into gravitational interaction with it and slightly weaken the Earth's gravitational field. If listeners jump at this moment, they should experience a strange feeling. Since 9.47am the BBC has received hundreds of calls reporting strange feelings, with one woman even saying she and her friends left their chairs and flew around the room.

Why are there 7 colors in the rainbow?

Although the multicolor spectrum of the rainbow is continuous, according to tradition, 7 colors are distinguished in it. It is believed that Isaac Newton was the first to choose this number. Moreover, initially he distinguished only five colors - red, yellow, green, blue and violet, which he wrote about in his “Optics”. But later, trying to create a correspondence between the number of colors in the spectrum and the number of fundamental tones of the musical scale, Newton added two more colors.

Why did Dirac want to refuse the Nobel Prize?

When the English physicist Paul Dirac was awarded the Nobel Prize in 1933, he wanted to refuse it because he hated advertising. However, Rutherford nevertheless persuaded his colleague to receive the award, since refusal would have become even more advertising.

What did the inventor of radar say when he was speeding?

Scottish physicist Robert Watson-Watt was once stopped by a policeman for speeding, after which he said: “If I had known what you would do with it, I would never have invented radar!”

What makes snowflakes unique?

Due to the enormous variety of snowflake shapes, it is believed that no two snowflakes have the same crystal structure. According to some physicists, there are more variants of such forms than there are atoms in the observable Universe.

How did maritime smugglers hide alcohol from American customs officers during Prohibition?

During Prohibition in the United States, most smuggled alcohol came by sea. Smugglers prepared in advance for sudden customs inspections at sea. They tied a bag of salt or sugar to each box, and when danger approached, they threw it into the water. After a certain time, the contents of the bags dissolved with water, and the loads floated to the surface.

What did the Celsius scale originally look like?

In the original Celsius scale, the freezing point of water was taken as 100 degrees, and the boiling point of water as 0. This scale was inverted by Carl Linnaeus, and in this form it is used to this day.

What discovery of Einstein was awarded the Nobel Prize?

The archives of the Nobel Committee preserved about 60 nominations for Einstein in connection with the formulation of the theory of relativity, but the prize was awarded only for his explanation of the photoelectric effect.

If you think physics is boring, then this article is for you. We will tell you fun facts that will help you take a fresh look at your least favorite subject.

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No. 1: why is the Sun red in the evenings?

Actually, the sun's light is white. White light, in its spectral decomposition, is the sum of all the colors of the rainbow. In the evening and morning, the rays pass through the low surface and dense layers of the atmosphere. Dust particles and air molecules thus act as a red filter, best transmitting the red component of the spectrum.

#2: Where do atoms come from?

When the Universe formed, there were no atoms. There were only elementary particles, and even then not all of them. The atoms of the elements of almost the entire periodic table were formed during nuclear reactions in the interior of stars, when lighter nuclei turn into heavier ones. We ourselves are made up of atoms formed in deep space.

No. 3: How much “dark” matter is there in the world?

We live in a material world and everything that is around is matter. You can touch it, sell it, buy it, you can build something. But in the world there is not only matter, but also dark matter. It does not emit electromagnetic radiation and does not interact with it.

Dark matter, for obvious reasons, has not been touched or seen by anyone. Scientists decided that it exists by observing some indirect signs. It is believed that dark matter makes up about 22% of the Universe. For comparison: the good old matter we are used to takes up only 5%.

No. 4: what is the temperature of lightning?

And it’s clear that it’s very high. According to science, it can reach 25,000 degrees Celsius. This is many times more than on the surface of the Sun (there are only about 5000). We strongly do not recommend trying to check what the temperature of the lightning is. There are specially trained people in the world for this.

Eat! Considering the scale of the Universe, the probability of this had previously been assessed quite high. But it was only relatively recently that people began to discover exoplanets.

Exoplanets orbit their stars in what is called the “life zone.” More than 3,500 exoplanets are now known, and they are being discovered more and more often.

#6: How old is the Earth?

The earth is about four billion years old. In the context of this, one fact is interesting: the largest unit of time is the kalpa. Kalpa (otherwise the day of Brahma) is a concept from Hinduism. According to him, day gives way to night, equal in duration. At the same time, the length of Brahma’s day coincides with the age of the Earth to within 5%.

By the way! If you are sorely short of time to study, pay attention. For our readers there is now a 10% discount on any type of work

#7: Where do the aurora come from?

The polar or northern lights are the result of the interaction of the solar wind (cosmic radiation) with the upper layers of the Earth's atmosphere.

Charged particles coming from space collide with atoms in the atmosphere, causing them to become excited and emit light. This phenomenon is observed at the poles, as the Earth's magnetic field "captures" particles, protecting the planet from "bombardment" by cosmic rays.

#8: Is it true that the water in the sink swirls in different directions in the northern and southern hemispheres?

Actually this is not true. Indeed, there is a Coriolis force acting on the flow of fluid in a rotating reference frame. On the scale of the Earth, the effect of this force is so small that it is possible to observe the swirling of water as it flows in different directions only under very carefully selected conditions.

No. 9: how is water different from other substances?

One of the fundamental properties of water is its density in solid and liquid states. Thus, ice is always lighter than liquid water, so it is always on the surface and does not sink. Also, hot water freezes faster than cold water. This paradox, called the Mpemba effect, has not yet been fully explained.

#10: How does speed affect time?

The faster an object moves, the slower time will pass for it. Here we can recall the paradox of twins, one of whom traveled on an ultra-fast spaceship, and the second remained on earth. When the space traveler returned home, he found his brother an old man. The answer to the question of why this happens is given by the theory of relativity and relativistic mechanics.

We hope our 10 facts about physics helped convince us that these are not just boring formulas, but the whole world around us.

However, formulas and problems can be a hassle. To save time, we have collected the most popular formulas and prepared a guide to solving physical problems.

And if you are tired of strict teachers and endless tests, contact the student service, which will help you quickly solve even tasks of increased complexity.

Physics is often associated with a boring and difficult topic. But often we don't even realize how many physical phenomena we see and use in our daily lives.

Physics can be quite interesting. Instead of talking about complicated equations, we will tell you about fun and interesting useful facts from physics.

Atom

All objects around us are made of atoms. Atoms are so small that by the time we write this sentence, 100,000 atoms could have already formed.

In fact, the Greeks were the first to talk about the existence of atoms 2400 years ago. But the idea of ​​atoms came and went and was not revisited until 1808, when John Dalton experimentally demonstrated that atoms do exist.

Atoms are part of the molecules of objects that we use every day, that we touch and see. There are so many atoms in one grain of sand that their number can be compared to the number of grains of sand themselves on the beach.

Solids and liquids

Solids are rigid because their molecules hold each other tightly together: here the molecules are arranged in a straight row. The molecules of solids cannot move around each other, so they remain motionless (although their atoms constantly vibrate).

In a liquid, on the other hand, the molecules also stick together tightly, but not as tightly as in solids, so they can move around and change shape. However, liquid cannot be compressed because its molecules are already packed very tightly together.

Gas molecules are loosely bound to each other, so they can spread out and fill space. In addition, gas molecules can be compressed to smaller sizes.

There are thin and thick liquids, such as water and honey. The density of a liquid determines its viscosity.

Curiously, glass is not a solid. In reality, glass is a liquid, but it is so viscous that we cannot notice how it flows. At the bottom of the old windows you will notice that the glass is much thicker: this is due to the fact that over time the glass has flowed down.

Heating and cooling

When objects heat up, they become larger: this phenomenon is called thermal expansion. Gases, liquids and solids always expand when heated.

A fun experiment you can try is to put an open plastic bottle in the refrigerator. When the bottle has cooled, place a ball on its neck, and then place the bottle in a bowl of hot water. The balloon will fill with air on its own. After this, place the bottle with the balloon back in the refrigerator: after the bottle freezes again, the balloon will deflate. When heated, the air in the bottle expands and enters the ball, since there is not enough space in the container. When cooled, objects return to their original size.

Also, in case the metal lid gets stuck in the jar, you can run it under hot water and it will open. Metal expands more than glass, so the lid will loosen. Different materials expand differently, depending on how close the material's molecules are to each other.

Other facts from physics

• When driving at 80 kilometers per hour, cars use about half of their fuel simply to overcome wind resistance.
• Water can go against gravity, moving up narrow pipes in a process called capillary action.
• Lightning is 3 times hotter than the Sun.
• It is possible to transform graphite into diamond by applying a temperature of 3000 degrees Celsius and a pressure of 100,000 atm.
• On average, our bodies constantly resist atmospheric pressure of about 1 kilogram per square inch.
• Lightning strikes about 6,000 times per minute on our planet.
• Due to gravitational effects, you weigh slightly less than normal when the Moon is directly overhead.
• When hydrogen burns in air, water is formed.
• "Light year" is a measure of distance, not time. It is defined as the distance that light travels in one year. Light moves at a speed of about 300 thousand kilometers every second, so in one year, it travels about 9,500,000,000,000 kilometers.
• Light has no mass, but it has weight. Weight is a measurement of the force exerted on something, and light can be bent by gravity.