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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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 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 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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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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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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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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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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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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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 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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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 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 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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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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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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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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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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