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What helps us to fall asleep when it is getting dark?
When it is getting dark, human’s body starts to produce a hormone called melatonin.
It is a hormone created by the pineal gland in the brain that is released into the bloodstream.
Darkness prompts the pineal gland to start producing melatonin, while light causes it to stop.
That’s why melatonin is known as the sleep hormone helping to synchronize the sleep-wake cycle with night and day, facilitating a transition to sleep and promoting consistent, quality rest.
Melatonin created within the body is endogenous melatonin, but it can also be produced externally. Exogenous melatonin is normally made synthetically, and as a dietary supplement.
❗️ There is however very little data about the long-term effects of melatonin supplements in children or adults.
‼️ There is also debate about whether melatonin is beneficial in otherwise healthy adults who have insomnia.
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What is insomnia and its symptons?
Insomnia is defined as difficulty either falling or staying asleep that is accompanied by daytime impairments.
🌚 Nighttime insomnia symptoms can include trouble sleeping and early waking.
🌞 Daytime insomnia symptoms may include fatigue, impaired memory, and irritability.
The 2️⃣ main types of insomnia are:
▪️acute insomnia that lasts not longer than three months and can often be traced to an external cause or life stressors
▪️chronic insomnia when a person experiences sleeping difficulties at least three days per week for longer than three months.
It is estimated that about 10% to 15% of people have chronic insomnia.
Common sleep issues that can be symptoms of insomnia are:
• Trouble falling asleep
• Trouble staying asleep throughout the night
• Unwanted early morning waking
• Resisting sleeping at bedtime in children and teens
• Difficulty sleeping without a caregiver’s help in children and teens
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What is NREM sleep?
A sleep is divided into 4️⃣ stages repeating cyclically throughout the night. The duration of each cycle is 90-120 min.
The first 3️⃣ stages are known as non-rapid eye movement (NREM) sleep:
Stage 1️⃣ NREM typically lasts several minutes, marks the transition between wakefulness and sleep. Muscles relax and heart rate, breathing, eye movements and brain waves begin to slow down.
Stage 2️⃣ NREM is the longest and is characterized by deeper sleep as processes in our organism continue slowing down. Body temperature decreases. Apart from some brief moments of higher frequency electrical activity, brain waves also remain slow.
Stage 3️⃣ NREM plays an important role in making you feel refreshed the next day. All vital processes reach their lowest levels, and the muscles are as relaxed as they will be. This stage will be longer at first and decrease in duration throughout the night.
ℹ️ NREM sleep constitutes 75-80% of each cycle.
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Does zero gravity exist?
🔹Contrary to popular belief, there’s no such thing as zero gravity.
🔹Weightlessness and zero gravity are two different things.
🔹While we’re on Earth 🌏, we feel our weight because, as the Earth’s gravity pulls us into its center, the ground pushes back against our feet.
🔹When spacemen orbit the earth, they’re still subject to gravity, but they’re moving sideways so quickly that even though they’re being pulled toward the earth, they’re not getting any closer to the planet’s center. In other words, they’re basically in a state of constant free fall, and that’s why they’re weightless.
🔹Gravity never disappears entirely, it just gets weaker. And every object with mass has gravitational attraction, but when one of the objects is much larger than the other, its mass predominates.
🔹So, moving away won’t free you of the Earth’s gravity. All that would happen is that the Earth’s pull would be masked by the pull of some other object.
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Which force acts at subatomic levels?
🔄 It is the weak nuclear force that is responsible for interactions between subatomic particles – the building blocks for matter, like protons, neutrons, and electrons.
🔺🔻Protons and neutrons are made of two quark varieties, up and down. This force can turn a down quark in a neutron into an up quark, which would change the neutron into a proton and switch its electric charge from neutral to positive. If that neutron were in the nucleus of an atom, the change to a proton would turn that atom into a different type of element. Such reactions are happening all the time in our Sun, giving it the energy to shine. This type of action also occurs in radioactive decay (atoms spontaneously shed energy and subatomic particles).
✔️This force works on the smallest distance scales, another 1,000 times smaller than the strong force. It is about a million times weaker than the strong force, too, though it is still considerably stronger than gravity.
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Which force illuminates our houses?
The answer to this question is electromagnetic force or electromagnetism.
It includes both electricity and magnetism, which are intertwined — a moving electric field produces a magnetic field, and vice versa.
Light carries this force, which illuminates our houses at night, keeps electrons in orbit around atomic nuclei, and allows chemical compounds to form.
Like gravity, the strength of electromagnetism drops off with the square of the distance between objects and works at infinite range. However, it only comes into play for charged objects, and whether it attracts or repels depends on the charges of each.
While stronger than gravity, this force is often balanced out in large objects by the equal numbers of positive and negative charges that form neutral atoms. For example Earth has a magnetic field due to electric currents in its liquid core, but Earth itself is electrically neutral.
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What are the four fundamental forces of nature that govern everything that happens in the universe?
For centuries, scientists have been trying to describe the forces that describe interactions in the universe on the largest and smallest scales, from planets to particles.
Modern science believes that that there are four fundamental forces:
1️⃣ Gravitational Force – the weakest force; but has infinite range.
2️⃣ Weak Nuclear Force – the next weakest; but short range.
3️⃣ Electromagnetic Force – stronger, with infinite range.
4️⃣ Strong Nuclear Force – strongest; but short range.
ℹ️ There is speculation that in the very early Universe when temperatures were very high (the Planck Scale) all four forces were unified into a single force. Then, as the temperature dropped, gravitational force separated first and then the other three forces followed. The process of the forces separating from each other is called spontaneous symmetry breaking.
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What types of photosynthesis do plants use ?
There are 3️⃣ main types of photosynthetic pathways: C3, C4 and CAM. They all produce sugars from CO2 using the Calvin cycle, but each pathway is slightly different.
🟩 Most plants use C3 photosynthesis, named for the three-carbon compound 3-PGA that it uses during the Calvin cycle. C3 plants include cereals (wheat and rice), cotton, potatoes and soybeans.
🟩 Plants such as maize and sugarcane use C4 photosynthesis. This process uses a four-carbon compound intermediate (called oxaloacetate) which is converted to malate. Malate is then transported into the bundle sheath where it breaks down and releases CO2, which is then fixed by rubisco and made into sugars in the Calvin cycle (just like C3 photosynthesis). C4 plants are better adapted to hot, dry environments and can continue to fix carbon even when their stomata are closed (as they have a clever storage solution).
🟩 Crassulacean acid metabolism (CAM) is found in plants adapted to very hot and dry environments, such as cacti and pineapples. When stomata open to take in CO2, they risk losing water to the external environment. Because of this, plants in very arid and hot environments have adapted. One adaptation is CAM, whereby plants open stomata at night (when temperatures are lower and water loss is less of a risk).CO2 enters the plants via the stomata and is fixed into oxaloacetate and converted into malate or another organic acid (like in the C4 pathway). The CO2 is then available for light-dependent reactions in the daytime, and stomata close, reducing the risk of water loss.
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Why are most plants green?
🌿 Plants are perceived as green because of their pigments.
ℹ️ In essence, a pigment means a coloring material; it is a dye, a paint. But in biology, a pigment, by definition, refers to a colored substance naturally produced by an organism.
🌿 Inside the plant cell are small organelles called chloroplasts, which store the energy of sunlight. Within the thylakoid membranes of the chloroplast is a light-absorbing pigment called chlorophyll.
🇫🇷 🔬🧪 French pharmacists, Joseph Bienaimé Caventou and Pierre Joseph Pelletier, coined the term “chlorophyll” in 1817 (Greek “chloros”, meaning “green” and “phyllon”, meaning “leaf”).
🌿 It’s chlorophyll which is responsible for giving the plant its green color. The chlorophyll pigments do not absorb well the green wavelength of the visible light, but do absorb well blue and red light. During photosynthesis, chlorophyll reflects green-light waves, which reach our eyes and so we perceive plants as green.
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Which countries have the most and the least paid public holidays?
According to the study, Asian countries are at the top of the table for paid public holidays (PPH).
🏆🇮🇷 Workers in Iran get to enjoy more paid public holidays than those working in any other country. Their many public holidays are in honor of both national and religious events with a grand total of 2️⃣7️⃣ days which are recognized as PPH.
🥈🇧🇩Bangladesh workers receive a similarly generous amount of 2️⃣4️⃣ PPH that also include Islamic religious holidays.
At the top 1️⃣0️⃣ countries with most paid public holidays one also finds:
🇦🇿Azerbaijan (21 PPH)
🇰🇭Cambodia (21 PPH)
🇸🇲San Marino (whose 20 public holidays make it the most generous in Europe)
🇲🇲Myanmar (20 PPH)
🇬🇾 (19 PPH)
🇰🇿Kazakhstan (19 PPH)
🇮🇶Iraq (18 PPH)
🇨🇴Colombia (18 PPH)
👎🇱🇾🇱🇧At the bottom of the table for paid public holidays are Libya with 0 PPH and Lebanon with 2 PPH.
The average number of PPH is 11.8.
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Which countries are the “best” and the “worst” for paid vacation days?
A team of analysts reviewed data on the annual statutory paid leave and paid public holidays laws in 197 countries, referring to government websites and UN structures. The countries were then ranked based on all collected information.
Vacation days refers in this study to the combined total of paid leave days and paid public holidays.
🏆🇮🇷 Iran has the most statutory annual paid vacation days (PVD) in the world – 53. As well as a reasonable 26 days of paid leave, Iran has nearly a month of public holidays (27 days), which is more than any other country. Religious holidays and days to mark events concerning the Islamic Revolution contribute to this total.
🥈🇸🇲 San Marino placed the second (46 PVD), African and Middle Eastern countries dominate the top of the table.
👎🇫🇲🇺🇸With 9 PVD Micronesia is the “worst” and with 10 PVD the U.S. is the second “worst” country for paid vacation days.
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What is the difference between holiday and vacation?
Both holidays and vacations are enjoyable ways to spend time with family and friends, and many people use the terms interchangeably, but there is a difference between the two.
📌 A holiday is a day set aside for a special celebration or commemoration. The word holiday has its roots in the Old English word 'hāligdæg', which means “holy day.” In many cultures, holidays are associated with religious or spiritual traditions. However, there are also secular holidays that are celebrated by people of all beliefs. Holidays often involve special food, decorations, and activities.
📌 Vacation is a travel planning application that helps you organize your trip itinerary. Itineraries can include flights, hotels, car rentals, and activities. Vacation also includes a packing list to help you remember what to bring on your trip.
So, holidays are typically tied to specific dates, whereas vacations can be taken at any time.
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What buildings are also in the world’s top-3 of the tallest constructs?
🏙🥈🇲🇾 The almost-completed Merdeka 118 ⬆️ is the second tallest building in the world, and the tallest building in South East Asia.
It towers 679 meters (2,220 feet) into the sky, overlooking the city of Kuala Lumpur in Malaysia.
The name Merdeka means Independence Day in Malaysian, while it will have 118 floors in total and is set to officially open in 2023.
🌆🥉🇨🇳 Set in Shanghai, China, Shanghai Tower ⬆️ is now the third tallest building in the world, measuring 632 meters (2,073 feet).
Completed in 2015, the impressive structure took nearly 20 years to complete after several funding issues arose during its construction.
The tower has one of the world’s fastest elevators, which travels at 20.5 meters per second, whizzing visitors up to the top of the building’s incredible 128 floors.
While Burj Khalifa is the tallest construct in the world, Shanghai Tower has the biggest number of usable floors.
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Who is known as the inventor of skyscrapers?
While “the Bessemer process” kept Bessemer’s name well-known, lesser-known today is the man who employed that process to create the first skyscraper and is often considered as the inventor of modern skyscrapers and construction.
It’s George A. Fuller (1851-1900)⬆️, an American architect.
Throughout the 19th century, construction techniques had called for outside walls to carry the load of a building’s weight.
Fuller, however, had a different idea. He realized that buildings could bear more weight—and therefore soar higher—if he used Bessemer steel beams to give buildings a load-bearing skeleton on the inside of the building.
In 1889, Fuller erected the Tacoma Building⬆️, a successor to the Home Insurance Building that became the first structure ever built where the outside walls did not carry the weight of the building.
Fuller developed a technique for creating steel cages that would be used in subsequent skyscrapers.
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What is a skyscraper?
🏙 Currently, a skyscraper refers to a tall habitable building with iron or steel frameworks over 100 m.
🌇 The first modern skyscraper was created in 1885—the 10-story Home Insurance Building in Chicago ⬆️.
📌 Before the word skyscraper described enormous buildings, it was used to describe anything that “stood out”, was tall - a tall man, a high-standing horse, a sky-sail, etc.
📌 Pointed out by skyscraper researchers, the Italian word ‘grattacielo’ means scraping the sky. It was in use since the early 13th century, and described a tall man.
📌 The word scraper dates back to the Old Norse word ‘skrapa’, which means to erase. Today, it means to use a tool to apply pressure to something. A skyscraper essentially erases the sky by sticking out and blocking it.
📌 Sources for the first usage of the word skyscraper are unclear. One of the oldest confirmed references in print was in American newspapers in the late 19th.
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What causes insomnia?
Researchers suggest that in many people insomnia likely results from certain types of physiological arousal at unwanted times, disrupting normal patterns of sleep, e.g. a heightened heart rate, a higher body temperature, increased levels of hormones, like cortisol.
A person’s family history, age, and gender may also play a role in their susceptibility to insomnia.
Insomnia often occurs alongside mental health disorders, including depression and anxiety. It is believed that the cause of insomnia may be distinct in people who have both insomnia and mental health conditions.
Risk factors for insomnia are:
✔️older age
✔️pregnancy
✔️medical conditions (diabetes, chronic pain)
✔️neurological problems
✔️other sleep disorders
✔️mood disorders
✔️socioeconomic status
✔️stress and lifestyle
❗️ It is important to note that not everyone who has one or more of these risk factors ⬆️ will have insomnia, and not everyone with insomnia will have one of these risk factors.
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At which stage of sleep are we dreaming?
Dreaming typically occurs during Rapid eye movement (REM) sleep.
REM is the final stage of sleep that occurs about 90 minutes after you fall asleep.
As the name suggests, your eyes will move back and forth rather quickly under your eyelids. Breathing rate, heart rate, and blood pressure will begin to increase. Arms and legs will become paralyzed – it’s believed this is intended to prevent you from physically acting out on your dreams.
The duration of each REM sleep cycle increases as the night progresses.
Numerous studies have also linked REM sleep to memory consolidation the process of converting recently learned experiences into long-term memories.
The duration of the REM stage will decrease as you age, causing you to spend more time in the NREM stages.
ℹ️ You may also wake up briefly during the night but not remember the next day. These episodes are known as “W” stages.
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Why do we need to sleep?
😴 Sleep is an essential function that allows human’s body and mind to recharge. Healthy sleep also helps the body remain healthy and stave off diseases.
😴 Without enough sleep, the brain cannot function properly. This can impair your abilities to concentrate, think clearly, and process memories. Recent findings suggest that sleep plays a housekeeping role by removing toxins in our brain that build up while we are awake.
😴 Most adults require at least seven hours of nightly sleep. Children and teenagers need substantially more sleep, particularly if they are younger than five years of age.
😴 Work schedules, day-to-day stressors, a disruptive bedroom environment, and medical conditions can all prevent us from receiving enough sleep. A healthy diet and positive lifestyle habits can help ensure an adequate amount of sleep each night.
😴 The average person spends about 26 years sleeping which represents approximately one-third of our life.
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How to measure gravity on different planets?
🌎On Earth, falling objects experience an acceleration of 9.8 m/s2 due to Earth's gravitational force (GF), and that is defined as 1 g.
The easiest way to measure the GF on other planets in the Solar System is to express it as a fraction of Earth's g-force.
Jupiter is the largest planet, and it has the largest GF.
The reasoning doesn't extend the other way, though.
Mercury is the smallest planet, but its surface gravity is about the same as that of the much larger Mars because Mercury is more dense.
Similarly, Saturn is much larger but less dense than Earth, so the GF on 🪐 is about the same as it is on 🌍.
The gravity you would experience on different planets is:
• Mercury: 0.38 g
• Venus: 0.9 g
• Moon: 0.17 g
• Mars: 0.38 g
• Jupiter: 2.53 g
• Saturn: 1.07 g
• Uranus: 0.89 g
• Neptune: 1.14 g
• Pluto: 0.063 g
🤩Enjoy this visualization of gravity on different planets and the Sun using cars falling to the divider.
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Which force is the strongest of the fundamental forces?
☢️💪 As suggested by its name, the strong nuclear force, or strong force for short, is the strongest of the fundamental forces.
❗️It is about 100 times stronger than electromagnetism and 100 trillion trillion trillion times stronger than gravity.
☢️⚛️ The strong force holds together the building blocks of atoms. It always attracts and works at two different size scales in atoms. At the level of an atomic nucleus, the strong force holds together the protons and neutrons that form the essence of the elements. On an even smaller scale, the strong force holds together the oppositely charged quarks that make up the neutrons and protons themselves.
ℹ️ However, the strong force only has influence over very small distances. For anything larger than the nucleus of a medium-sized atom (about 100 million times smaller than the width of a human hair), its influence quickly drops and other forces will be stronger.
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What is gravity?
According to the general theory of relativity, gravity can be understood as bends and curves in the fabric of space-time that affect the motions of galaxies, stars, planets, and even light.
Anything with mass makes a dent in space-time, causing objects to be attracted to each other.
It is the force of attraction that draws two objects together. Its strength increases along with the masses of the two objects, but decreases at a rate of the square of the distance between them.
That means that if the Moon were twice its current distance from the Earth, the gravitational tug between the two would be just one fourth of what it is now.
Gravity turns out to be the weakest of the fundamental forces of nature, especially at the molecular and atomic scales.
Gravity works across infinite distances, making it responsible for the formation of the universe.
The legend has it that Isaac Newton’s idea of gravity came about as a result of observing an apple fall from a tree.
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How many types of chlorophyll have scientists discovered for the moment?
ℹ️ The chlorophyll molecule is a chlorin pigment with magnesium at the center of the chlorin ring.
For the moment researchers have identified 5️⃣ closely related chlorophylls:
🟢 chlorophyll a is the main light-harvesting pigment present in all photosynthetic organisms (higher plants, red algae, green algae). Its molecular formula is: C55H72O5N4Mg. It is best at absorbing photons at 400-450 nm and 650-700 nm.
🟢 chlorophyll b is present in higher plants and green algae and functions as a light-harvesting pigment that passes on the light excitation to chlorophyll a. Its molecular formula is C55H70O6N4Mg. It is best at absorbing photons at 450-500 nm and 600-650 nm.
🟢 chlorophyll c is an accessory pigment found in certain marine algae (diatoms, dinoflagellates, brown algae). Its molecular formula is C35H28O5N4Mg. It is best at absorbing photons at 447-452 nm.
🟢 chlorophyll d is the form found in photosynthetic organisms thriving in moderately deep water (red algae, cyanobacteria - blue-green algae). Its molecular formula is C54H70O6N4Mg. It is best at absorbing infrared light.
🟢 chlorophyll e is an accessory pigment and a rare type, isolated from very few algal species, such as in some golden algae. No sufficient information is available about this type of chlorophyll, including the chemical structure and molecular formula.
🟢 chlorophyll f is present in aquatic organisms (cyanobacteria) that enable the absorption of near-infrared light. Its molecular formula is C55H70O6N4Mg.
All of them reflect the green light. However, there are slight differences. For instance, they differ slightly in their structure causing them to appear in different shades of green. Chlorophyll a, in particular, is a blue-green pigment whereas chlorophyll b is a yellow-green pigment.
For land plants, the main chlorophyll pigments are chlorophyll a and b. Chlorophyll a, however, is the type of chlorophyll that can convert light energy and thus participates directly in the light reaction of photosynthesis. Chlorophyll b, in contrast, can absorb light energy but eventually relays the energy to chlorophyll a. Because of this, chlorophyll a is the most predominant form of chlorophyll pigment and explains why it is depicted as universal, meaning it is present in all photosynthetic organisms. Nevertheless, chlorophyll b is essential in boosting the efficacy of photosynthesis.
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What are two major stages of photosynthesis?
Photosynthesis can be broken down into 2️⃣ major stages: light-dependent reactions and light-independent reactions.
1️⃣ The light-dependent reaction takes place within the thylakoid membrane and requires a steady stream of sunlight, hence its name. The chlorophyll absorbs energy from the light waves, which is converted into chemical energy in the form of the molecules ATP and NADPH.
2️⃣ The light-independent stage takes place in the stroma, the space between the thylakoid membranes and the chloroplast membranes, and does not require light, hence its the name. During this three-step stage, energy from the ATP and NADPH molecules is used to assemble carbohydrate molecules, like glucose, from carbon dioxide. So, this stage is the process that generates sugars for the plant. It is also known as the Calvin Cycle ⬆️, named after Melvin Calvin (1911-1997), the Nobel Prize-winning scientist who discovered it.
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What does most life on Earth depend on?
Most life on our planet depends on the process called photosynthesis.
This process is carried out by plants, algae, and some types of bacteria, which capture energy from sunlight to produce oxygen (O2) and chemical energy stored in glucose (a sugar). Herbivores then obtain this energy by eating plants, and carnivores obtain it by eating herbivores.
During photosynthesis, plants take in carbon dioxide (CO2) and water (H2O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air, and stores energy within the glucose molecules.
Look at this video ⬆️ how the oxygen is released by a leaf during photosynthesis.
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Which countries get the most and the least paid leave days?
In the same study, paid leave refers to the statutory minimum annual time off bookable by the individual.
The study makes a conclusion that four weeks' leave has become something of a norm around much of the world. The average by country is 18.2 days of paid leave per year.
🏆2️⃣2️⃣ countries have a 3️⃣0️⃣-day leave plan, of which 1️⃣0️⃣ are in Africa 🌍.
These are:
🇲🇨Monaco
🇲🇭Marshall Islands
🇦🇩Andorra
🇲🇻Maldives
🇧🇹Bhutan
🇰🇲Comoros
🇩🇯Djibouti
🇬🇶Equatorial Guinea
🇧🇭Bahrain
🇰🇼Kuwait
🇩🇿Algeria
🇬🇳Guinea
🇱🇾Libya
🇲🇱Mali
🇲🇬Madagascar
🇳🇪Niger
🇹🇬Togo
🇴🇲Oman
🇵🇪Peru
🇵🇦 Panama
🇹🇲Turkmenistan
🇾🇪Yemen
🥈🥈🇲🇩🏴🇷🇺 Moldova, Scotland and Russia have 2️⃣8️⃣ paid leave days.
👎🇰🇮🇫🇲🇳🇷🇺🇸 The Pacific island countries of Kiribati, Micronesia and Nauru, and The U.S. are at the bottom of the table for paid leave, with the figure of 0️⃣ days.
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What are some interesting facts about the history of vacations?
🏖🏺 The Greeks were the first who saw the need to have rest periods to perform more work and intellectually.
🏖🏛But it is the Romans who invented the vacations as a social phenomenon. Many Roman families went on vacation through well-kept roads of the Roman Empire, the preferred destination being the Mediterranean coast.
❌🏖 In the European Middle Ages, leisure was considered sinful, so the vacations were not practiced even on Sunday.
🏖💰 It wasn’t until the 19th century that vacations ceased to be a privilege of the upper classes. The industrial revolution gave the middle class access to travel at reasonable prices thanks to the railroad.
🏖💯The Communist Government of the Soviet Union in 1917 was the first that spoke of vacations as a right of workers.
🏖✅🇫🇷🇧🇷 In 1930s France legalized paid vacations, and in the 1960s, along with Brazil, it became the country with the most paid vacations in the world.
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How do different heights of waves and tsunamis look like in comparison?
🌊 Some time ago, a group of computer graphic designers asked themselves this question and made this video.
🌊 It shows waves and tsunamis of different sizes in comparison to a small boat and some of the tallest buildings like the Eiffel Tower and the Burj Khalifa.
🌊 A multitude of waves from the smallest wave of 1 meter high to one of the tallest wave ever surfed and the biggest tsunami that was recorded in July 1958 in Lituya Bay, on Alaska's southern coast, is shown in the video.
ℹ️🌊 In the comments to this video a user rightly remarks that the form of normal waves and tsunami waves is different. Tsunami waves are usually not particularly high (unless in situations like Lituya Bay), it's the wavelength that is much more dangerous. Tsunami waves might only be 5m high but they continuously push inland, totally inundating the area. A normal wave, even if it’s very high, crashes and is dispersed in seconds.
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What is the tallest building in the world?
🌇🇦🇪❗️At an incredible height of 828 meters (2,717 feet), Burj Khalifa in Dubai, the United Arab Emirates, is the tallest recorded building in the world.
🔝It’s three times as tall as the Eiffel Tower.
🔝It has hotels, residential apartments and shopping malls that cover 2km2. Upon its completion in 2010, it broke several records, including the world's highest restaurant and nightclub. It also has the most number of floors (163) of any building ever constructed and the tallest elevator shaft in the world.
🔝It also has over 24,000 windows.
🔝The structure is built using reinforced concrete, aluminium and steel. It took more than 110,000 tons of concrete, 55,000 tons of steel rebar, and 22 million man-hours to complete the building. The total weight of aluminum used on the Burj Khalifa is equivalent to that of five A380 aircraft.
🔝The tip of the spire of the Burj Khalifa can be seen from up to 95 kilometers away.
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What is Bessemer Process and how it enabled the construction of skyscrapers?
☑️Bessemer process is a process of making steel from pig iron by burning out impurities (as carbon) by means of a blast of air forced through the hot liquid metal.
☑️It was the first inexpensive industrial process that allowed for the mass production of steel.
☑️This term bears its name from Henry Bessemer (1813-1898), an English inventor and engineer, devoted to metallurgy ⬆️.
☑️Though named after Bessemer, before it was commercialized, this process evolved from the contributions of many investigators, eg an American, William Kelly, who had also been working on a similar process for making steel.
🔘In any case, this breakthrough opened the door for builders to start making taller and taller structures.
ℹ️Modern steel is still made using technology based on Bessemer process.
ℹ️Taller buildings were also made possible through the invention of the electric elevator and lighting.
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How do we use lenses?
Concave Lens is used:
✔️ to correct myopia eye defects
✔️ to make spectacles
✔️ in peepholes in hotel room doors.
✔️ in the construction of certain types of telescopes.
Convex Lens is used:
✔️ to correct hypermetropia eye defects
✔️ in cameras and digital cameras as optical devices for producing a reduced, true, and inverted image on film.
✔️ in microscopes and telescopes
✔️ to produce a magnified image of an object.
Subtypes of convex lens are:
📌 A bi-convex lens is a basic lens that consists of two convex surfaces in a spherical form with the same radius of curvature.
📌 Plano-convex lenses are positive focal length elements that have one spherical surface and one flat surface
📌 ConConvex lenses are also known as converging lenses since the rays converge after falling on the convex lens.
Subtypes of concave lenses are:
📌 A bi-concave lens have two inward curved surfaces. These lenses have a negative focal length.
📌 A plano-concave lens is an optical lens with one concave surface and one flat surface. It has a negative focal length and can be used for light projection, beam expansion, or to increase the focal length of an optical system.
📌 A concavo-convex lens is a converging lens. This is because it is thicker in the middle and thinner at the edges allowing it to converge all the light that is incident on it.
ℹ️‼️👀 The lens of our eyes is also convex. The inverted image of the item on the retina is formed by the eye lens.
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