CULTURAL QA 10-2023-19A Q3 How long does it take for Earth to go around our sun once? What is that called?
KR: This is another kind of repeat; I wrote a lot on these matters long back’ Innocent copying. Q5 What are some interesting facts about the Sahara desert? KR Another repeat KR IRS 19 10 23 ---------- Forwarded message --------- From: 'gopala krishnan' via iyer123 <[email protected]> Date: Thu, 19 Oct 2023 at 19:49 Subject: [iyer123] CULTURAL QA 10-2023-19A To: Patty Thatha <[email protected]>, Iyer < [email protected]>, Kerala Iyer <[email protected]> *CULTURAL QA 10-2023-19A* *All the BELOW QA are from Quora digest to me on 19-10- 2023.* *Quora answers need not be 100% correct answers * *.Compiled* *and posted by R. Gopala krishnan, on 19-10-2023* *Q1 Does light travel forever or does it eventually fade?* *A1 Tafer, PHD in Power scaling & Debunking, Hogwarts School of Witchcraft and Wizardry (fictional school) (Graduated 2020)9mo* *Light is a type of electromagnetic radiation that travels through space at a constant speed** of about 299,792,458 meters per second (186,282 miles per second). Light is able to travel through a vacuum, which means that it does not need a medium (such as air or water) to propagate.* *Light does not fade over time**, but it can be absorbed, scattered, or otherwise absorbed by matter, which can reduce its intensity or change its direction of travel. * *For example, light from a star that is billions of light-years away from Earth can be weakened by the dust and gas in interstellar space, and it can also be affected by the gravitational fields of celestial objects such as planets and galaxies.* *However, even if light is absorbed or scattered, it does not disappear. Instead, it is transformed into other forms of energy, such as heat or kinetic energy. In this sense, light can be said to be "eternal" in the sense that it can never be completely destroyed, but it can change form and be transformed into other types of energy.* *Q2 Why did France want to ban domestic flights in favor of a high speed train service?* *A2 Nicholas Stone,Life long interest in trains.13h* *The French government banned some domestic flight travel, for climate change and rail policy reasons.* *The EU’s European Commission approved the ban and French government then signed this into the country's Climate Law on 23 May 2023.* *The ban only applies to three routes. Specifically Paris' Orly airport to Bordeaux, Lyon and Nantes. Paris Charles de Gaulle still offer services to these routes for connecting passengers. * *The ban also reflect France’s excellent domestic electric high speed train service. Most French cities are less than 3 hours from Paris by train**. While Lille, Le Mans and Rheims are less than 90 minutes by train from Paris.* *In September 2023, I travelled domestically in France - between Bordeaux and Paris. This is a distance of 550 km by rail. The journey time on the famous TGV passenger train was just 2 hrs 05 mins. This domestic journey was neither possible by plane, nor even recommended.* *Q3 How long does it take for Earth to go around our sun once? What is that called?* *A3 Jeff Lewis, Studied at University of Maryland, College Park Tue* *Okay Quora Prompt Generator, you've drawn me in with another question that's more interesting than most people realize.* *The time it takes for the Earth to go around the Sun once is known as a sidereal year, which is different from a calendar year (or more accurately, a tropical year). And it's not just because calendar years have to use whole days – even with leap years, sidereal years and calendar years drift away from each other.* *The issue comes down to what we want a year to represent. It seems that society has settled on wanting a year to represent the cycle of the seasons.* *We should all remember from grade school that the seasons are caused by the tilt of the Earth's axis**, but this tilt wobbles, or 'precesses'. While the Earth's axis is currently aimed more or less at the North Star, because of this wobble, in about 13,000 years, it will be aimed closer to Vega. So, if we measured years as the time it takes the Earth to go around the Sun, then 13,000 years from now, the seasons would be switched. January in the northern hemisphere would be warm, while July would be cold, and solstices and equinoxes would all be 6 months out of phase compared to where they are now.* *So, to keep a year representing the cycle of the seasons, we use a slightly different definition of a year* *– the time for the Sun to return to the same relative position in the sky (i.e. vernal equinox to vernal equinox, or summer solstice to summer solstice). This is technically known as a tropical year, and is around 20 minutes shorter than a sidereal year. * *Using tropical years means that 13,000 year from now, the summer solstice will still take place in June, but the Earth will be on the opposite side of the Sun when it happens.* *ABOVE SOURCE: As Earth wobbles due to** precession, do the seasons change in regard to the months (i.e., 13,000 years from now, will June be winter for the Northern Hemisphere and December summer)? | Astronomy.com* *This is also the reason why the signs of the Zodiac are drifting**. While 13,000 years is a pretty long time, it's still short enough to be noticed in the time frame of civilization. Since the signs of the Zodiac were based on the constellations the Sun was passing through at the time, and that it's been around 4,000 years ago since those signs were first developed, that means that the difference between sidereal and tropical years means the constellations have drifted roughly 31% of the way (4/13) to their opposite relative locations. Or another way to look at it, 4/13 is really close to 4/12, which means the signs have shifted just about 4 places by now.* *So, to answer the question with actual values, the time it takes the Earth to go around the Sun, a sidereal year, is 365 days 6 hours 9 minutes 10 seconds, while the cycle of the seasons, a tropical year, is 365 days 5 hours 48 minutes 46 seconds**. * *A calendar year, pretty obviously, is nearly always either 365 days or 366 days depending on whether or not it's a leap year** (with the occasional leap second), with the timing of leap years designed to keep the calendar years in sync with the seasons.* *Q4 What are some cool facts about the Universe?* *A4 Ariel, Studies Psychology (Expected 2025)3y* *When you look into the night sky, you are looking back in time* *Many of the atoms you're made of, from the calcium in your bones to the iron in your blood, were brewed up in the heart of an exploding star billions of years ago.* *And back in the days before digital television, if you tuned your TV between stations, a small percentage of the static you would see would actually be the afterglow of the Big Bang.* *Outer space is silent. Eerily silent. That's because sound waves need some sort of medium to travel through. And space is a vacuum. A dark, silent vacuum.* *The sun makes up 99.86% of the mass of the solar system**. It's so big that you could squeeze 1.3 million Earths inside of it.* *There might be as many as three sextillion stars in the universe. That's 3 followed by 23 zeros, or 300,000,000,000,000,000,000,000. That's more than all of the grains of sand on Earth.* *Ordinary, observable matter (like stars and planets) makes up a measly 5% of the universe**. The other 95% universe is made up of invisible dark energy (68%) and dark matter (27%). That means there's 95% of the universe that we don't know about yet.* *It takes 225 million years for our Sun to travel round the galaxy* *Our solar system’s biggest mountain is on Mars* *The human brain is the most complex object in the known universe* *We are all made of stardust* *Q5 What are some interesting facts about the Sahara desert?* *A5 Gary Meaney, passionate fan of all things animal2y* *My note- Lengthy answer. Very informative and interesting answer. **8 page answer. Please read at spare time.* *The Sahara is unimaginably vast; spanning some 9 million square kilometres, it’s the world’s largest desert outside those of the polar regions. Thus, as you would expect, there’s an awful lot of interesting stuff going on inside it. For this answer I’ve picked only the most fascinating tidbits I could find on this region.* *Despite its (deserved) reputation as a scorching wasteland, it does occasionally snow in the Sahara.** Three instances of significant snowfall have been recorded here, all in Algeria, and in all cases the snow melted within hours of it falling. The last time it happened was January of 2018.* *In some parts of the Sahara Desert, especially Tunisia, desert roses form**. These are beautiful crystals of gypsum, encrusted in sand, which are created by the evaporation of shallow water bodies. It’s easy to see how they get their name.* *In Mauritania you can find an immense circular rock formation known as the Richat Structure, or the Eye of the Sahara**. It measures forty kilometres in diameter, and was originally thought to be an impact crater, but is now understood to be an eroded dome of volcanic rock.* *About 14,500 years ago, an era called the African Humid Period began**, lasting up until ~6,000 years ago. During this time, the monsoon of West Africa became stronger, and the Saharan region saw a marked increase in rainfall. The desert gave way to lush savannah, leading to a Green Sahara.* *Lake Chad is currently the largest body of water in the Sahara,** but it is a shadow of its former self. While the region was green, Lake Chad was Lake MegaChad, over 700 times its modern size! In fact, it was the world’s largest lake, by far, at more than a million square kilometres in area.* *The Sahara Desert contains more prehistoric rock art than perhaps any other part of the world**. These ancient paintings date back as far as 12,000 years ago, and depict everything from warfare and farming to people swimming and now-extinct local wildlife. They are an invaluable window into the lush, rainy past of this now-bleak desert.* *In Eastern Morocco, there is an incredibly rich fossil site - the Kem Kem Beds* *- from around 95 million years ago. It shows that this part of the Sahara was once a marshy place which was the abode of some of the largest carnivorous dinosaurs of all time, 30-ton sauropods, giant crocodiles, sawfish bigger than minivans, and much more.* *The desert’s Saharan silver ants are spectacularly well-adapted to the extreme heat**. Their beautiful silvery hair reflects sunlight, and they have special proteins which allow them to withstand up to 53 degrees Celsius! Even still, they can only spend 10 minutes per day in the sun, so they have to be speedy - in fact, for their size they are the third-fastest organisms on Earth.* * (That paragraph was criminally short for an overview of these amazing ants, I’ll have to do them justice in a full answer some day…)* *The Sahara is home to a fascinating plant called Anastatica hierochuntica**, also known as the rose of Jericho. When the dry season begins, it shrivels up and becomes fully desiccated, detaching from the ground and blowing away in the wind. Yet, upon contact with moisture in the following wet season, it “resurrects” itself, regaining its former vitality.* *In Chad, you can find Guelta d’Archei, a beautiful secluded oasis in a deep sandstone gorge**. Every day, it is used by local herders to quench the thirst of thousands of camels, which have stained the waters black with their dung. The oasis is the only known remaining colony of West African crocodiles in the Sahara Desert, too.* *In 1993, electrician Emile Leray was travelling in the desert of Morocco when his car allegedly hit a rock and had its front axle destroyed. He dismantled the wreck, and used the parts to build a fully functioning motorcycle, which he dubbed his “Steel Camel” and rode to civilization.* *(It’s worth mentioning that, while this is nevertheless really cool, it’s unlikely that it was a daring tale of survival as is often claimed. What’s much more probable is that Leray went to the Sahara with the explicit intention of building a motorbike out of his Citroen there.)* *The hottest known part of the Sahara Desert is Bou Bernous, a very small and isolated town in western** Algeria. Its average temperature over the course of a day was once recorded at a blistering 47 degrees Celsius, the highest such measurement anywhere on Earth!* *My note- The lowest temperature recorded in Chennai is 15.8 °C (60.4 °F) and **highest 45 °C **(113 °F)(30 May 2003). The average annual rainfall is about 1,400 mm (55 in). The city gets most of its seasonal rainfall from the north-east monsoon winds, from mid-September to mid-December. (Google search result)* *If you look at a satellite map of Libya, you might** notice an abrupt little black dot. That is Waw an Namus, a verdant oasis inside a volcano, famous for its black tephra (volcanic gravel, basically). It is rich in bird-life, unlike the surrounding wasteland.* *The Ancient Romans made several military explorations deep into the Sahara**, even venturing into sub-Saharan Africa. One expedition party, for example, arrived at Lake Chad, which they called the “lake of hippopotamuses”. They stationed a small garrison here.* *In Mali’s Dogon region**, in the southern extreme of the Sahara, there is a steep cliff known as the Bandiagara Escarpment. Here, the local people build spectacular villages of mud huts which hug the sandstone cliffside.* *The Mauritanian Railway is a rail route on which** some of the world’s longest trains traverse. These trains can be up to three goddamn kilometres long, and weigh tens of thousands of tonnes! They carry iron ore and occasionally passengers.* *My note- **Google search result**-Since the closure of the Choum Tunnel, a 5 km (3.1 mi) section of the railway cuts through the Polisario Front-controlled part of the **Western Sahara **(21.354867°N 13.012644°W).* *In Tunisia, there is a unique desert village called Matmata. Here, some local Berbers dwell in underground houses**, formed around one or more large pits, perfect for shielding oneself from the scorching Saharan sun. The town was the main filming location of Tatooine in the original Star Wars film.* *One of Egypt’s UNESCO World Heritage Sites is Wadi El Hitan, or the Valley of the Whales**. It is in fact a paleontological dig site, where exceptional fossils of the ancient whale Basilosaurus have been uncovered. Remains of sharks, sea cows, turtles and even the first ever pelican have also been found there, showing the sands were once a shallow sea.* *Morocco boasts the title of having the world’s largest concentrated solar power plant**, the Ouarzazate Solar Power Station. Its construction began in 2013, and when it is finished it will produce an estimated 582 megawatts of energy. The project has cost around 2.5 billion dollars.* *Though not nearly as famous for the structures as Egypt is, Sudan is home to over 350 pyramids -** more than twice as many as the former nation has. These were built by the Nubian people, who were then known as the Kingdom of Kush, starting at around 800 BC.* *When you think about Saharan scenery, you probably imagine featureless dune fields and rocky plains, but the Hoggar Mountains of Algeria feature many dramatic landscapes**. These highlands are volcanic in origin, and some of their peaks are nearly 3 kilometres high.* *In the desert of Niger, you can find the world’s tallest mud-brick building, the Mosque of Agadez**. It was built way back in 1515, and has gone practically unchanged since then.* *In Morocco every year, the Marathon des Sables is held - arguably the world’s most gruelling and challenging footrace**. At 251 km in length, the course is six times longer than a standard marathon, and takes nearly a week to complete. Due to COVID-19, the race hasn’t been held since 2019.* *There is a 7,000 square kilometre lake in the Tunisian Sahara called Chott el Djerid which - in summer - becomes the desert’s largest salt pan.* *Due to evaporation, a crust of salt builds up over the water, thick enough to drive a car over. When winter comes, it returns to its watery state.* *On average, 182 million tonnes of Saharan dust are blown west over the Atlantic Ocean each year. Of** that, 28.8 million tonnes settle in the Amazon Rainforest of South America. This seemingly plays a crucial role in the jungle’s biodiversity, as the dust carries vital minerals for fertility such as phosphorus.* *Some of that dust also ends up in Cape Verde, an archipelago off the west coast of the Sahara, and acculumates in the Viana Desert. This small field of sand dunes could be considered an extension of the Sahara Desert found way out in the Atlantic Ocean.* *Egypt is home to both a Black Desert and a White Desert**. The former is a volcanic area full of mounds of basalt, in which dinosaur remains have been excavated. The latter is famous for its chalk rocks, which have been eroded into exquisite shapes.* *So, I’ll leave it that for today**. At first glance, the Sahara seems pretty empty, but upon taking a much closer look I’ve realized that I couldn’t possibly fit all of its interesting features in a digestible answer. I hope you enjoyed the ones that I selected.* *As an aside, I know the phrase “Sahara Desert” is tautological, as the word Sahara itself derives from the Arabic word for desert**. However, I have used the phrase in this answer, mainly to mix up the word choice a bit. A bit ironic that I ended up using a repetitive name to avoid being repetitive, but anyway…* -- You received this message because you are subscribed to the Google Groups "iyer123" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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