15 мин
8 февраля 2018 г.

Detailed analysis of Open Lab Work 2019

All you need to know about the science behind the test
Автор: Laba.Media

Part 1.Renyxa

Science is constantly evolving. Its theories, which just yesterday seemed unconditionally true, change radically, and various hypotheses, once fantastical, are ultimately proven right. Common sense often lags behind science and clings onto outdated notions. We have put together a list of reliable facts and sciencey-looking nonsense, which we call 'renyxa'. See if you can easily tell them apart.


1. Dmitry Mendeleev invented the recipe for Russian vodka.
Answer: False.

Mendeleev's thesis was called, "Considerations on mixing alcohol with water", and this may be why the great chemist is often credited with an invention he never made. Indeed, his work was used in the production of vodka, but Mendeleev himself never did anything of the sort. Perhaps the 40% vol. vodka was 'invented' by a Russian Empire minister of finance, Mikhail Reutern, who suggested rounding up the alcohol content to 40% to make counting the volume of the product and collecting excises more convenient.

2. Wires can conduct electricity without any losses.
Answer: True.

This is called superconductivity. Superconductivity is a property of some materials that have exactly zero electrical resistance at the temperature below a certain level (or critical temperature). There are several hundred materials — pure elements, alloys and ceramics — which can become superconducting. Normally the transition to a superconductive state happens at very low temperatures of several Kelvin (around -270C). But we now have high-temperature superconductors with a critical temperature of -135C.

3. Humans can live with one brain hemisphere.
Answer: True.

Certain conditions of either brain hemisphere (for instance, severe epilepsy) require the patient to undergo anatomical hemispherectomy — the removal of an entire brain hemisphere. Sometimes it is done at an early age when extensive damage to one hemisphere threatens the normal functioning of the other. It would seem that if the left hemisphere were removed, the patient would never be able to speak or understand speech because language centers are located there. But that is not true. When the operation is done early enough, at the age of five years or younger, speech functions recover. Patients can speak and understand speech with some mistakes.

4. When you follow the red needle of a compass, you will get to the northernmost point on Earth.
Answer: True.

The red needle of a compass shows the direction to the Earth's North magnetic pole, which is located somewhere around the Geographical North Pole. At the beginning of the 17th century, the North magnetic pole was in the Canadian Arctic. Since the second half of the 20th century, it has been quickly drifting across the Arctic Ocean towards the Taymyr peninsula. In 2009, the speed of the North magnetic pole was 64 kilometers per year. Now it's relatively close (some 3.5 degrees) to the Geographical North Pole.

5. No animal can feed through photosynthesis.
Answer: False.

Photosynthesis happens virtually in every kingdom of life, including animals (ciliates, flatworms, corals, molluscs and salamanders). Photosynthesis is a process where an organism converts light into chemical energy. It happens in peculiar cellular organelles — plastids, which are semi-autonomous systems with their own small sets of genes in rings of DNA. In animals, however, it is always the result of symbiosis or acquisition of either entire photosynthetic cells or single photosynthesis genes. Take, for example, Elysia chlorotica, a sea slug, of marine nudibranch molluscs. At its larval stage, this slug eats algae, but it doesn't digest them all, leaving chloroplasts intact. These chloroplasts still work, and the slug puts them into its outer layer cells. They keep working under the light, as they would in the plant, producing glucose that the slug uses as food. Unlike normal symbiosis of animals and photosynthetic algae, Elysia chlorotica added certain 'plastid' genes to its genome that it needs to keep the chloroplasts functioning. Elysia chlorotica is an example of an extraordinarily close symbiosis of an animal and a plant that even involves the genome. So, in a sense, Elysia chlorotica is a photosynthesizing animal.

6. Destroying information always releases heat.
Answer: True.

Information is always stored as a special physical condition, for instance, as a magnetized domain on a hard drive (although that is not necessary, as information can be written down on a piece of paper with a pencil). Physical processes always underlie any computational processes. Whenever information is irretrievably lost, entropy decreases in the system where it was kept. But according to the second law of thermodynamics, this cannot be the only result of a physical process in a closed system. That is why the temperature of memory increases just enough to overcompensate for the reduction of information entropy in that memory.

In 1961, Rolf Landauer, a German-American physicist, showed that, at room temperature, irretrievable deletion of one bit of information releases no less than 2.7×10^−21 joules of thermal energy. That is a very small number. In 1961, and for a long time after that, computers were slow and energy-consuming: they emitted a lot of heat from heating contacts and nodes of the machine, many trillion times more than the heat produced by deleting information. Landauer's paper resurfaced in the 21st century when computers became very fast and very efficient, and developers started chasing down every small part of a joule in heat generation. When a chip has billions of gates, and they are all working at a pace of several billions of operations per second, the amount of heat released by deleting information becomes significant. This heat is very difficult to reduce. These days CPUs are so efficient that every deleted bit produces just a thousand times more heat than the Landauer minimum.

7. At the equator, days are always as long as nights.
Answer: True.

The sun always rises vertically at the equator, perpendicular to the horizon, and it sets in the same way. So the day always lasts 12 hours. It's easy to imagine this if you consider the visible movement of the sun at various latitudes.

The diurnal motion of the celestial bodies at the North pole (left).
The diurnal motion of the celestial bodies at mid-latitudes (centre).
The diurnal motion of the celestial bodies at the equator (right).
To be precise, the day at the equator is slightly longer than the night. This is because the sun has a nonzero angular size, and the day starts when its upper rim is just above the horizon. Due to this and to the refraction of the light in the atmosphere, the day at the equator lasts around 12 hours and 10 minutes.

8. Water is denser than ice.
Answer: True.

Most substances on Earth get denser when they freeze, but not water. The maximum density of freshwater at normal atmospheric pressure is 1000 kilograms per cubic meter, at 4 degrees Celsius. Continued cooling makes water less dense: at zero degrees its density is 999.87 kilos per cubic meter, so, when cooled to 0C, a liter of water becomes several tenths of a gram lighter. The density of ice at 0C is 0.9167 grams per cubic centimeter — this means that ice is one-tenth of a gram lighter than water. Even though water at 4C is just a bit heavier than at 0C, it goes down to the lower layers and stays liquid. Because there's liquid water at the bottom of rivers and other water bodies even in the winter, they can sustain life.

9. Neurons can't be restored.
Answer: False.

Unlike other cells in our body, neurons, the cells of our nervous system, do not divide. So new cells cannot replace the ones that died. This led, for a while, to a common and quite scientific idea that neurons can't be restored. But in the 1960s, neurogenesis was discovered in rats, and later in other animals and birds. In the 1990s, neurogenesis was found in the human brain. The 2000s brought conclusive evidence of neurogenesis in adult humans. New neurons are born from the wall cells of the ventricles and in the gyrus dentatus of the hippocampus. After their birth, the neurons migrate to a new location and join existing neural networks. If we learn to direct the process of neurogenesis and neural migration, this can help treat many brain diseases, including Parkinson's.

10. Levitation is a fantastical technology.
Answer: False.

There are actually quite a few levitation techniques, that is, objects hovering in the presence of gravity. The simplest one is thermal soaring. Superconductors can also levitate in a magnetic field; there's levitation in interfering acoustic waves, and levitating a live frog in a strong magnetic field earned Andre Geim an Ig Nobel prize in 2000. Magnetic levitation technology is now used in passenger trains.

11. Calico cats are always female.
Answer: True.

Calico cats are always female because the X chromosome determines hair color, and females have two X chromosomes. Healthy male cats only have one X chromosome and one Y chromosome, so it is almost impossible for a male cat to have two pigments at the same time — the red one, pheomelanin, and the black one, eumelanin. The only exceptions are the extremely rare XXY male cats that can have tortoiseshell or calico coats. Most of these males are sterile due to a genetic mutation.

12. Protium, deuterium and tritium all occupy one spot in the Periodic table.
Answer: True.

These are all isotopes of one element, hydrogen. The nuclei of isotopes of an element contain the same number of protons but a different number of neutrons. Protium, the main hydrogen isotope, contains one proton; deuterium has a proton and a neutron, and tritium has a proton and two neutrons. There are seven hydrogen isotopes in total, but the other four are very unstable and decay very quickly. Every element has isotopes. So the Periodic table is not flat but, rather, 3D: every cell is a 'tower' with every isotope occupying its 'floor'.

Part 2. Your version

Common sense is often wrong, but it has an advantage: it represents the world as a whole. Sometimes it's enough to imagine something in broadest strokes to get a plausible hypothesis. Try using your life experience, which includes both common sense and scientific knowledge, to come up with your own version.


13. The Wings of Dedalus
2019 marks the 500th anniversary of the death of the great artist and thinker, Leonardo da Vinci (1452-1519). All his life Leonardo was drawn to the idea of humans flying. His diaries have many drawings of flying machines that look like bird wings. According to legends, Dedalus, an ancient Greek master, invented such a machine. Leonardo da Vinci never managed to build a machine like that, but his drawings inspired a great many followers. Machines that fly due to the lift of a moving wing are called ornithopters. Unmanned aircraft like that are already flying. But what can an ornithopter working on sheer muscular force of a pilot do on a horizontal takeoff strip?

A. For now, it can neither take off nor fly.
B. It can take off but not fly.
C. It can't take off on its own, but it can fly.
D. It can both take off and fly.

Answer: C.

Human-driven ornithopters have achieved their biggest success just recently. In 2010, researchers at the University of Toronto developed Snowbird, a human-powered ornithopter. The pilot, who is also the 'engine', Todd Reichert, flew 145 meters for 19.3 seconds, at an average speed of 25.6 km/h. Snowbird is a combination of the most modern technologies and Leonardo da Vinci's drawings. At a 32 m wingspan, just like a Boeing 737, it weighs only 42 kilograms. One of the stories about Snowbird: 
And here is a video of Reichert's flight.
Yet Snowbird couldn't take off on its own — it was sped up a bit by a car. Leonardo himself understood that taking off is harder than flying, so he even proposed an acceleration mechanism to help his machine take off. So we can think of Leonardo's dream of a man flying like a bird as fulfilled.

14. Counting Your Descendants
In 2018, there were 7.6 billion people on Earth. Every year the UN demographic Committee publishes its long-term population projections for up to 2100. Which of these projections do the UN experts consider most likely?

A. The population will grow, and the growth will keep accelerating.
B. The population will grow and then stop growing.
C. The population will remain approximately at the same level.
D. The population will decrease after a peak.

Answer: B.

Let's have a look at the UN projections for 2018.

We see three scenarios here. First is the high one, in the red. This scenario assumes that the number of children per one fertile woman (fertility rate) will stay at today's level (option A). The low scenario (in the green) assumes that the fertility rate will drop quickly (option D). The blue, or moderate, scenario (option C) is the most likely one: this means the fertility rate will slowly decrease, but not as sharply as in the green scenario. The blue scenario has the Earth's population at the end of the 21st century at the peak of 11.5 billion, with growth having almost stopped (option B). Option C is impossible. The world's population cannot stabilize at today's level because it depends on the fertility rate, so these days the population is determined by the number of girls born 25 years ago. (This is why demographic waves happen). The fertility rate is decreasing, so population growth will also slow down, although it will still be positive.
Let's have a look at the main parameter affecting population growth — the fertility rate.

The blue line is the rate; up to 2015 it is based on measurements, and from 2020 to 2100 it is the projected rate. The fertility rate reached its peak in 1960–1965. Then it started to drop dramatically. This decline has slowed down, but a reversal of the trend is highly unlikely.
There are several reasons for the decline in fertility rate that inevitably causes a slowdown in population growth and its subsequent halt:
- an increase in income that leads people to choose quality of life over quantity of children;
- women's education and employment and preference for a career over childbirth;
- later age of first birth;
- state-sanctioned control of fertility in the biggest countries: in China, the fertility rate dropped from 2.8 in 1978 to 1.5 in 2015, and India saw a decrease from 5.7 in 1966 to 2.8 in 2016;
- preference of civil partnerships over marriage;
- the spread of contraceptives.
Not only do all of these factors keep working, but they are also quickly spreading to other countries in Africa and Asia, where fertility rates are traditionally high.


15. The Accuracy of Measurements
The most precise modern equipment allows us to measure the movement of bodies at the scale lower than…

A. bacteria.
B. a molecule.
C. an atom.
D. an atomic nucleus.

Answer: D.

We can observe the movement of an object at the scale of a bacterium (that is, for around a micron) through a simple microscope, and we can measure this movement with a common mechanical micrometer. The movement at the scale of molecules (nanometers) and atoms (fractions of a nanometer) can be seen through probe microscopes. 30 years ago IBM engineers managed to assemble the company name out of single atoms, using a scanning tunneling microscope as a nanomanipulator. The nucleus of an atom is four orders of magnitude smaller than the atom: its size is measured in femtometers (1015 meters). Yet the accuracy achieved at the Laser Interferometer Gravitational-Wave Observatory, LIGO, is even four orders of magnitude higher: it can spot a change in the distance between the mirrors 4 kilometers apart at the scale of an attometer (10—18 meters). It's reasonable to ask: how can things made of atoms even have measurements of such accuracy, with a margin of error several orders of magnitude smaller than the atom? It's all because of the many atoms that comprise the mirrors. Although individual atoms can be displaced from their positions by a distance slightly smaller than their size, the displacements of different atoms cancel each other out, and the entire mass of atoms of the mirror has a much more precisely defined position.

16. The Steepest Subway in the World
The steepness of the climb is measured by the change in height per kilometre travelled. What is the highest slope that an ordinary subway train can climb?

A. 60 meters per kilometer.
В. 120 meters per kilometer.
C. 240 meters per kilometer.
В. 480 meters per kilometer.

Answer: A.

The right answer is A, 60 meters per kilometer, or 3.4 degrees. This is the slope of the tracks between Nevsky Prospect and Gor’kovskaya subway stations in Saint Petersburg.
The slope limit is determined by the coefficient of steel-on-steel friction, which is about 0.14. And you have to have a margin to allow acceleration and braking, as well as for bad weather. It is also very important that the angle limit is lower if not all wheels are traction wheels. That is why trains that only have traction wheels on the locomotive and that can endure bad weather normally handle a slope no bigger than 20 meters per kilometer on high-speed lines and 40 meters per kilometer on slower regional lines. There are no weather issues in the subway so the slope can be bigger.
Some trams can handle a bigger slope due to all wheels being traction wheels and a special alloy that is apparently selected to increase the friction. All other examples illustrate what lengths we have to go to so as to increase the slope.
120 meters per kilometer, or 6.8 degrees, is close to the limit of a tram, but subway trains have to use tyred cars at this slope.
240 meters per kilometer is the angle normally used in funicular railways such as the Carmelit in Haifa, with an average slope of 140 meters per kilometer (8 degrees) and the maximum slope of 315 meters per kilometer, or 17.5 degrees.
480 meters per kilometer is the current record for a train on a rack railway: that is the Pilatusbahn in Switzerland. However, cable rail funiculars can have an even bigger slope, such as the Gelmer funicular in Bern: its maximum slope is over 1000 meters per kilometer (49.4 degrees). Ultimately, this system turns into an elevator.

17. Endless Stars in the Sky
Humans have been looking at the sky and analyzing the relative position of stars for millennia. How many stars can current optical telescopes observe?

A. Thousands.
B. Millions.
C. Billions.
D. Trillions.

Answer: D.

You can see thousands of stars with the naked eye. You can see millions with an amateur telescope. The largest star catalogue, published in 2015 by the United States Naval Observatory, has 228 million stars of the northern sky with a magnitude of up to 18.5. Large ground-based telescopes can see stars with a magnitude of up to 25. There are many billions of these stars, although we don't know the exact number. These are mostly stars in our galaxy, and there are about 200 billion of them. However, the Hubble Space Telescope can see bright stars not just in our galaxy but in neighboring ones too. So the total amount of stars it can see is measured in trillions.

18. Sweet Stocks
Honey bees and other similar insects make honey from flower nectar or sugary secretions of other insects. It doesn't rot, and you can accumulate it and store. We know that honey bees can make honey, but there are other honey-making insects. Which of these cannot make honey?

A. Bumblebees.
В. Aphids.
C. Wasps.
D. Ants.

Answer: B.

Honey bees and all species of bumblebees can make honey. Some wasps, for instance, of the Brachygastra genus, can also make honey. There are several genera of ants, such as Myrmecocystus, which can also make honey. Some individuals accumulate and store honey in their bodies. They become 'honey barrels' of sorts and inflate to the size of a small grape. They give their honey to other ants when times are tough. Only aphids cannot make honey: instead, they secrete honeydew that ants, including honey ants, can eat.

Part 3. The Periodic Table of Elements. Chemistry

2019 marks the 150th anniversary of the Periodic Table of Elements, or Mendeleev's table. This table is a graphic representation of the periodic law formulated by the Russian scientist Dmitri Mendeleev in 1869. The same chemical elements occur in the entire observable universe. Both humans and distant galaxies consist of these elements. This section has questions on the unexpected properties of chemical elements and their roles in the history of our civilization.


19. The Composition of a Human
The human body has 81 elements of the periodic table. Over half (62%) of its mass is just one element. Which one is it?

A. Oxygen.
В. Hydrogen.
C. Nitrogen.
D. Carbon.

Answer: A.

The answer to this question is predictable: we know that water comprises more than half (around 65%) of the body's mass, and oxygen is the heavier part of water. Oxygen is essential to every life form: not only is it a part of water, but it is also contained in proteins (17.9%), fats (22.4%), carbohydrates (49.38%), nucleic acids and many other things. It is also involved in tissue and cellular respiration: it oxidizes fats, proteins and carbohydrates from food. All other elements are found in much smaller quantities: carbon, for instance, is just 18% of the total mass, hydrogen is 10%, nitrogen is approximately 2%, and the remaining elements have even smaller fractions.


20. Tin Pest
The chemists who wrote the book "Napoleon's Buttons" hypothesized that Napoleon lost his war against Russia because the tin buttons on his soldiers' uniforms could break in the cold winter due to 'tin pest', which rendered the army incapable of fighting. It is true that pure tin loses its stability and crumbles in the cold. Yet the chemists were wrong. Why?

A. Napoleon's army had an abundant supply of buttons.
B. Buttons were made of brass instead of tin.
C. Buttons were purely decorative.
D. Buttons were made of tin with an admixture of lead.

Answer: D.

When they came to their conclusion, the authors of "Napoleon's Buttons" likely considered this fact: in 1868, academician Julius Fritzsche reported to the Saint Petersburg Academy of Sciences that all tin buttons and blocks at the military and customs warehouses broke down. The causes of 'tin pest'
were unknown at the time. But nothing of the sort happened to Napoleon's army. The buttons were not just decorative (although this was their purpose on the aufschlags of the uniforms) but also functional. There was no stock of buttons as it was not necessary. The reason the buttons never crumbled is that they were made of 'dirty' tin with added lead. This is the kind of tin buttons and dishes and cutlery were made of for hundreds of years. This alloy is not vulnerable to tin pest and does not decay in the cold.
When cooled, pure white tin (the β-modification) transforms into grey tin (the α-modification). Phase transition of white tin into grey tin is accompanied by an increase in unit volume by 25.6%. This process begins at temperatures below 13C and happens most actively at –30C. Grey tin crumbles into powder. And even a small amount of grey tin can serve as a catalyst for this process (this is what's called 'tin pest').
The buttons Fritzsche dealt with were made of pure tin, and that's why they crumbled in the cold.
There was, however, one occasion where tin pest indeed caused a tragedy.
In March 1912, a team of British explorers led by Robert Scott competed against Roald Amundsen's expedition to be the first to conquer the South Pole. They lost. On the way back the explorers discovered that their fuel barrels had holes in them, and the kerosene had leaked out. The barrels were sealed with pure tin that was destroyed with tin pest.

21. The Blood Element
The color of the Martian surface and the color of human blood are determined by the presence of the same chemical element. Which one is it?

A. Manganese.
В. Copper.
C. Oxygen.
D. Iron.

Answer: D.

The bloody red color of Mars is the color of iron oxide. The color of red blood cells, erythrocytes, is determined by haemoglobin, a protein containing an atom of iron, that can bind oxygen. The name 'haemoglobin' contains the ancient Greek word 'haema' (αἷμα), which means 'blood'.

22. A Rare Color
Today we have many artificially created dyes. Yet relatively recently they were made from plants and minerals. Which mineral dye was the rarest and most expensive?

A. Red.
В. Yellow.
C. Blue.
D. Green.

Answer: C.

The main natural 'colorants' are found in the middle of the periodic table (these are titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper), and, to a lesser extent, tungsten, molybdenum, uranium and rare earth elements. The most common gems are green, yellow and red. Multiple elements can bring out these colors, and they are among the most common in the Earth's crust (iron, chromium, manganese, and copper). Blue is the rarest color. Sometimes it appears due to copper, and the most famous blue mineral, lazurite, is blue because of sulfur. "The enormous value of blue lazurite dye can be seen from the fact that the most important parts of Renaissance paintings were done in the natural ultramarine color, which did not change over time, and the wonderful decorations of the Spanish Alhambra were painted with natural lapis lazuli pigment" (Fersman, "Gem Stories")

Part 4. The Map of the World. Geography

When we try to imagine the Earth as a whole, we usually think of a flat map. But its real shape determines much in the life of Earth. See if you can imagine the shape of the Earth by looking at a flat map of the world.


23. Captain Flint's 'Discovery'
In the TV show, "Black Sails" (season 3, episode 26), Captain Flint decides to hide his ship in the open sea near Nassau (Bahamas). How did he do this?

A. Disguise the ship as an iceberg.
B. Wait for an unusually foggy day.
C. Direct the ship over the horizon.
D. There is no way to hide a ship in the open seas.

Answer: C.

Nassau (the Bahamas) is located at 25 degrees north latitude. Broken pieces of icebergs in the Atlantic occasionally reach the 30th parallel and occur around the Bermudas. Even if an exceptionally large iceberg could get to Nassau (which has never happened before), this would be a rare phenomenon that would attract more attention than hide anything. Flint did not do that, and neither did he wait for the fog. Flint hid the ship beyond the horizon. To do that, you have to take it just 9-10 kilometers from the port into the sea. Then the curvature of the Earth will hide the hull (its height with the deck is around 7 meters). The crew took down the sails and turned the ship broadside to the shore to make it even harder to notice the yards. The ship could travel at 5-6 knots (about 10 kilometers per hour), and Flint could reach the shore from his hideout in about an hour.
By watching the ship disappear beyond the horizon and knowing its height and the height above sea level, an observer can estimate the Earth's radius.

Since the Earth is curved, an observer at sea sees herself at the center of a circle with the sky seemingly joined with the sea surface at the edges. This circle is called the visible horizon of the observer. The visible horizon is marked by a dotted line in the picture. So to the observer at the point A and at the height of h above ground (for instance, in the crow's nest), the visible horizon is formed by the lines of sight touching the Earth's surface (the BCO angle is 90 degrees). Note that the island shore around Nassau is almost at the sea level. The visible horizon is usually defined as the (d) portion of the BC line. (d) is easily deduced from the Pythagorean theorem.

d = sqrt ((R + h)² - R²) = sqrt (h (2R+h)), where R is the Earth's radius, usually defined as 6378 kilometers
Due to the refraction of sunlight in the atmosphere 
Thus the formula changes to the following: d = 1.06 sqrt (h (2R+h))

Let r be the refraction coefficient, then
d² =  r²((R+h)²-R²)=r²(R²+2Rh+h²-R²)=r²(2Rh+h²)
Note that if the observer is at a relatively small height (the brig's mast is about 25-30 meters and the hull is about 7 meters), then 2Rh>>h², so h² can be dismissed.
We get
d²/2r²h = R
So then if the range is about 10 kilometers (d), the height of the hull is about 7 meters (h), the refraction coefficient is 1.06 (r), we get the value of R around 6300 kilometers. That is slightly less than the true radius of the Earth.


24. The Shortest Route from Moscow to New York
One can travel from point A to point B in a variety of ways, but one of them is always the shortest. In the real world, we travel not on a flat map but on a 'globe'. The green lines in the map are routes. Which route from Moscow to New York is the shortest?

A. The southern arc.
В. The straight line on the map.
C. The northern arc.
D. The route across the Arctic Ocean.

Answer: C.

The shortest route C (the northern arc) is through Iceland and around 7800 kilometers. This is because the Earth is close to a sphere, and the shortest route on a sphere is the minor arc of a great circle, i.e. a circle that is formed by a plane that passes through the center of the sphere. The straight line on the map (B) is nowhere near the shortest at 8900 kilometers. If we were looking for the shortest route from, say, Cape Town (in the south of Africa) to Rio de Janeiro, the southern arc would be the shortest. The shortest route from Moscow to Vancouver, located on the western seaboard of Canada, passes right across the Arctic Ocean.

25. The True Mountain
The globe does not describe the shape of the Earth with absolute precision. Our planet is more like an ellipsoid, flattened at the poles and wider at the equator. These red dots on the map are mountain peaks. Which one is the farthest point from the center of the Earth (indicated in the parentheses is the height above sea level)?

A. Mauna Kea (4207 m).
В. Kilimanjaro (5895 m).
C. Chimborazo (6267 m).
D. Everest (8848 m).

Answer: C.

The peaks of mountains located closer to the equator are farther from the center of the Earth than the more northern or southern peaks of the same height. Mauna Kea, a dormant volcano in Hawaii, is the tallest mountain on the Earth when measured from its oceanic base (over 10 kilometers), but it's relatively small above sea level (4207 meters). Kilimanjaro is located very close to the equator, but its height (5895 meters) is smaller than that of Chimborazo (6267 m), so the latter's peak is the farthest point from the center of the Earth. Its exact height was measured in 2016 using a satellite

navigation system. The peak was several kilometers farther from the center of the Earth than Everest's peak (6384.4 kilometers against 6381 kilometers).