What is the most rare and expensive metal on earth?

 The most rare and expensive metal on earth is rhodium. This precious metal is extremely rare and can be best described as a silver-white, hard, corrosion-resistant inert transition metal. It belongs to the platinum group metals (PGMs) and has the chemical symbol Rh and the atomic number 45.

Rhodium is mainly used in catalytic converters, which are devices that reduce harmful emissions from vehicle exhausts. It is also used in some jewelry, electrical contacts, and industrial equipment. Rhodium is highly valued for its high melting point, durability, and resistance to oxidation and corrosion.

Rhodium is very scarce and difficult to extract. It is usually obtained as a by-product of mining and refining platinum or palladium. The price of rhodium fluctuates depending on the supply and demand factors. In 2020, rhodium reached a record high of over $13,000 per troy ounce, making it more than 10 times more expensive than gold. But rhodium prices can also drop sharply due to economic downturns or technological changes.

Rhodium is mostly mined in South Africa, which accounts for about 80% of the global supply. Other major producers are Russia, Canada, and Zimbabwe. Rhodium is traded on the London Platinum and Palladium Market (LPPM) and the New York Mercantile Exchange (NYMEX).

What is the most boring country on earth?

 Nauru.

(It's pronounced as Na-u-ru, btw)

Nauru is an Island in Oceania and the third smallest country in the world, with an area of 21 square kilometres. There are 12.000 people living there, 94% of them are overweight, 70% obese, so if you're one of the 200 annual tourists, you're probably the healthiest. The entire country has exactly one club, if you're banned from entering it, you have to swim 700km to the next one, have fun.
Nauru has one actual street that goes around the entire country. It takes 25 minutes to drive the entire length. If you want to go on a holiday there, you can live in the only hotel this place has. Technically, there are like 6, but you can only book a room in one, lol.

Nauru has a lot of beaches, but because of the ocean current, you can't swim there.

The main attraction of this country is a Phosphate loading facility, very pretty. Alternative, the country also has like 5 churches.
In general, 80% of this island is a Phosphate mining plant. There are like 3 Trees on there. And 3 random stones in the ocean.

And maybe you're now thinking "perfect for being alone" i mean yeah, but the internet is quite terrible there too, so have fun doing literally nothing.

Are any stars or galaxies similar in size to Earth?

 Sirus B is a White Dwarf star orbiting the bright star Sirius A in the constellation Canis Major, located about 8.6 light-years from Earth. Practically our neighbour. It is almost as big as earth, with a 12,000 km Diameter.

Galaxies, even the small ones, are an order of magnitude bigger than Earth (which is 12,742 km in diameter). Seque 2, one of the smallest known galaxies and a satellite of the Milky Way located approximately 114,000 light-years away, is about 220 light-years in diameter.

Around 160 trillion Earths could fit side-by-side along the diameter of Seque 2.

Space is fun, scary and big.

Why are there only seven continents?

 It's humans who make the lines, not the earth.

Thick plates drifting over deep fire.

Europe. Asia. They share one crust - it is unbroken.

If we call it Eurasia, there are six left over. If we go further south, we find a huge ocean shelf that has sunk long ago. If we call that one Zealandia, that makes eight.

Our maps lie to us. We split land by culture, but it makes hard borders with no water.

Hard rocks do not care that we name them. Large pieces slowly move away from each other. Ancient oceans dry up. New lands completely covered up.

The mapmakers. They find comfort in the numbers. Underneath the surface, the earth constantly moves, shifting under the heavy foot. Soon, the ice will melt, raising the black water to swallow the shores we know.

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It breaks through the boundaries we created long ago - Our beautiful drawing breaks apart yet again.

What is the most dangerous place on Earth?

 North Korea Jail

Disturbing images ahead!!!!!!

I don’t own any of the images below. They are downloaded from google.

Most of the answers included Natural places which are dangerous to live. However, here I would like to show share a place which is driven by a naughty fat boy who himself consider as God. The place is so dangerous that if you steal a Propaganda from A HOTEL, THERE IS 15 YEARS OF JAIL!!!!!

The place is none other than - North Korean Jail.

Prisoners are forced to starve-

Pregnancy is biggest crime in jail!

for small mistakes, there are harsh punishments-

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and if somehow they escaped or freed from the hell, they will not survive long enough..

Inside North Korea's barbaric jails where prisoners dig their own graves

Revealed: Life inside North Korea's torturous prison camps

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Read more about North Korea-

Mohammad Ahmed's answer to Why is North Korea so fascinating?

What is the most dangerous place on Earth?

 Verkhoyansk, Russia

Located deep in the heart of Siberia and 3000 miles east of Moscow, Verkhoyansk is one of the coldest cities in the world. Referred to as the Cold Pole, the city is well-known for its endless winters, with the Yana River frozen solid nine months of the year.

Winter temperatures fall between minus 60 and minus 40 degrees Fahrenheit, and from September to March, the city averages fewer than 5 hours of sunlight every day. For most of its history Verkhoyansk was used as an exile city by czars and Soviets.

Lake Kivu, Democratic Republic of Congo/Rwanda

Renowned as one of the great lakes of Africa, Lake Kivu is located along the border between Congo and Rwanda. But deep below its surface, the lake houses over 2.3 trillion cubic feet of methane gas and 60 cubic miles of carbon dioxide, which, if released, can spark a methane explosion, incite lake tsunamis and kill the two million residents that call the basin home. Trying to think positive? The gas will likely be released only if volcanic activity occurs below the lake.

Dallol, Ethiopia

If Verkhoyansk is the coldest city in the world, then Dallol, Ethiopia is the antithesis. Located five hours outside of Ethiopia’s center in the Danakil Desert, Dallol is known by locals as “the Gateway to Hell”. It’s an apt title for the hottest inhabited place on Earth, where temperatures in summer reach up to 148 degrees Fahrenheit.

Average temperatures hover around 94 degrees Fahrenheit, but that’s of little relief to the locals. To add fuel to fire, the rugged region is a revelation of salt flats, active volcanoes and regular earthquakes. Unsurprisingly, given the settlement’s inhospitable climate and lack of infrastructure.

Somalia

Since the civil war began in 1990, Somalia has been divided into over two dozen warring groups. Disease, famine, and ineffective governance have contributed to the rise of terrorist factions, which have further cracked Somalia’s already fumbling foundations, embroiling it in crime and violence.

Famine is a perennially devastating issue in in Somalia, and from 2010 to 2012 it claimed the lives of over 260,000 people. According to an annual ranking by Foreign Policy and the Global Fund for Peace, Somalia is the most failed state in the world. Tourists, suffice to say, are non-existent.

Why don’t we find any living dinosaur species on Earth now?

 But we do! We see them all the time, flying above our heads and making nests where they can.

And if they’re not flying, they’re chasing you and you should be running for your life (unless it’s a kiwi), and it might have a raptor claw. Meet the cassowary.

(If you mean the big guys though, like triceratops and t-rex, it was an asteroid the size of mt. everest. The crater can be found on chicxulub peninsula in Mexico.)

What was the largest river that has ever existed on Earth?

The largest river to have existed in the last half a billion years might have been the Mega Congo-Amazon.

In the contemporary world, the largest river by discharge is the Amazon, but the Nile, by some measures, might be the longest, and over its length, there are some disputes. However, both of these rivers pale in comparison to the mega Congo-Amazon, which existed when South America was still connected to Africa in the Gondwana and Pangea supercontinents and might have been around 10,000 km in length, almost twice the length of the Amazon alone. It was home to huge dinosaurs and other fascinating Mesozoic creatures.

The drainage area of the Amazon today is about 7 million sq km, the Congo about 4 million, and the Nile about 3.4 million. The Mega Congo Amazon had a drainage area of around 12 million square kilometers.

The flow rate of the Amazon is about 210,000 m3/sec, and that of the Congo is about 40,000 m3/sec. However, for millions of years, the climate was much wetter during the existence of the Mega Amazon-Congo, and its discharge was likely much higher than the combined flow rate of the Amazon and Congo rivers in Africa and South America.

When these two continents split, both the Amazon and the Congo continued to flow from east to west—Congo towards the Atlantic and Amazon towards the Pacific Ocean, but 23 to 50 million years ago Andes started to grow rapidly, and 10 to 15 million years ago, they became large and tall enough to block the flow of the Amazon towards the west.

For millions of years, the water accumulated into a vast inland sea and swamp, the Pebas, in what is now Colombia, Ecuador, parts of Peru, and western Brazil. It discharged into the Caribbean in the north of modern-day Colombia. It existed for so long that indigenous and fascinating animals and plants evolved to live in it, only for their habitat to be destroyed when the Amazon found a way, via sandstone, to flow east towards the Atlantic 7 to 10 million years ago.

Some of the most fascinating animals of the Pebas were Purussaurus, a 10-ton, 10 to 12 meters-long crocodile with the strongest bite force of any known animal, stronger than that of T. rex. There were also filter-feeding crocodilians with duck-like bills. Stupendemys was a 3-meter-long, up to 1-ton turtle. Freshwater snails of the Pebas had thick shells of up to 40cm in diameter.

The mega Congo-Amazon River might have been the largest in the last half-billion years. Earth experienced many supercontinental cycles over its 4.5-billion-year history, and if larger rivers existed on older supercontinents like Columbia/Nuna, 1.8–1.4 billion years ago, or Rodinia, 1.2 to 0.75 billion years ago, we have no evidence of their drainage basins due to erosion. Older supercontinents were still too small to harbor such large drainage basins. Therefore, the Mega Congo-Amazon is the largest we have evidence of ever having existed in the history of our planet.

What are some mind-blowing facts about the planet Earth?

 Earth looked like this 700 million years ago:

That’s right, the entire planet was covered in ice sheets that reached to the equator, the globe was on an ice age on massive steroids. This event is known as Snowball Earth, the most recent of which happened in the Cryogenian period (720–635 million years ago) during the Neoproterozoic era. Earlier global freezing did happen in the Paleoproterozoic (Huronian glaciation), but I’ll be focusing on the Sturtian and Marinoan glaciations in specific.

There are 2 main things that determine Earth’s temperature-

• The sun’s luminosity
• Atmospheric gases

Back in the Cryogenian, the sun was 6–7% dimmer than it is today (the sun gets brighter over time), meaning baseline temperatures were a lot lower on average, which made Earth much more vulnerable to an albedo runaway, which I’ll get to in a bit.

In the preceding Tonian period, continents were lined in the equator, this is huge as chemical weathering is strongest at the equator due to intense rainfalls. Chemical weathering locks CO2 gases into carbonate rocks, this happens when CO2 rains down upon silicate rocks, which are common in volcanic regions and continental merging. Carbon dioxide is a greenhouse gas, which means it traps the sun’s heat in the atmosphere, unlike how oxygen is. So when CO2 gets locked away in carbonate rocks, the amount of greenhouse gases in the atmosphere decreases.

This process happened over in the millions of years leading up to the Cryogenian, CO2 would keep plummeting as more and more carbonate rocks were formed due to chemical weathering, which continuously cooled the planet. Eventually, ice around the poles started to form, ice is one of the best deflectors of sunlight on Earth, otherwise known as albedo. As the amount of greenhouse gases lowered, more and more ice started to form, which reflected more sunlight, which made the Earth even colder, which meant more ice.

Once the ice reached around 40° degrees latitude, the albedo runaway effect became unstoppable, causing ice to eventually reach the equator, thus beginning Snowball Earth.

Cryogenian Earth 🧊

It’s estimated that at least 80–90% of the planet during this time would’ve been frozen rock solid, with possible small patches of equatorial ocean remaining intact, if any. Otherwise, the continents were covered in ice sheets kilometers thick, with oceans being covered in ice at least a couple hundred meters thick.

Temperatures around this time are estimated to have averaged around -50°C globally, with the equator being around -30°C on average, and the poles being a whopping -80°C on average! To put that into perspective, Antarctica's record low of -89°C is barely colder than the average South Pole day of Snowball Earth.

The absolute coldest days of Cryogenian period would’ve likely happened in the South Pole at winter, it’s been estimated that the record low could've reached a monumental -110°C to -130°C, that’s as freezing as the average day on Mars’s poles at night. These were very likely the coldest days in Earth’s history.

However, below the ice sheets covering the sea, life was still enduring, the earliest and most primitive of animals still hanged on in these hellish conditions, such as Otavia antiqua, possibly by being near hydrothermal vents and small patches of water where sunlight hit.

And as for how Snowball Earth ended? Volcanos. 🌋

Even during this global freezing, volcanos remained active and contributors of CO2 gases, and now that Earth was frozen, chemical weathering became pretty much nonexistent, so nothing was able to prevent CO2 gases from accumulating over millions of years.

Eventually, enough CO2 accumulated that ice began to melt at the equator before eventually, Earth was ice free.

Since then, Snowball Earth has never happened again, the last time this phenomena could’ve been possible under the perfect conditions was around 540–520 million years ago in the early Cambrian, afterwards, the sun became too bright to allow ice to reach the equator before melting. Even today, we are nearing the threshold for ice ages in the geological time scale. Snowball Earth will forever be exclusive to the Proterozoic eon.

-Cesar Alcaraz

Who proved that the Earth isn't flat?

 Anyone can, so it is hard to know who first concluded the Earth wasn’t flat.

For one thing, it depends on scale. Locally, of course, we all know it isn’t flat. There are hills and valleys, mountains and seas. So that means one needs to consider distances larger than tens of miles or kilometers - distances such that the variation from being flat due to the terrain is insignificant. But at distances of tens of miles or kilometers, is sufficient to recognize that it isn’t flat on that scale either if one recognizes what a horizon is.

There are places on Earth where it seems to be flat for large distances. Here are some of those:

But in each of those places, there is a well-defined horizon line - meaning, you cannot see beyond it. Why? Because the Earth’s surface is everywhere curved (or convex). In that last image, for example, there are hills or mountains in the background, but you cannot see their bases (especially those much farther away near the right side of the photo). In the middle picture, about fifty or a hundred miles beyond that horizon line, there are mountains which you cannot see. In the photo of the Pacific Ocean - taken from only a few feet above the level of the sea, one can only see a few miles out into the ocean, even though we know it goes for thousands.

So who first noticed that? We have no idea. But as far as we know, Eratosthenes with the first to actually take measurements that allowed calculating the radius of curvature. But that means people long before him already knew it was curved, they just hadn’t measured the curvature.

What are some unique unknown facts about our living Earth

 Here I presenting some images that contain some unique and unknown facts about our planet earth, I guess maybe they deserve millions of views.

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How would earth be affected if the super massive black hole at the center of the galaxy turned into a quasar?

Without a warning, Earth was enveloped by a beam of intense light from the center of the galaxy. The pole of the supermassive black hole Sagittarius A* was pointing at our planet. It was the end of human civilization.

People who were outdoors were evaporated immediately, and only a faint shadow of their existence was imprinted on the ground where they stood. Much more horrifying fates awaited people inside the buildings. The hot air evaporated the glass in the windows and entered their rooms. Their skin, exposed to extremely high temperatures, melted to flesh as they experienced enormous pain for a fraction of a second. Fortunately, it didn’t last long; they died quickly. Or maybe not….

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We have recently discovered that the axis of rotation of Sagittarius A*, the supermassive black hole at the center of the Milky Way, is oriented in such a way that we are facing its pole. This is surprising because the planes of the spiral disks of galaxies would tend to align with the equatorial regions of the event horizons of supermassive black holes at their centers.

When these monsters become active by feeding on vast amounts of matter, they can evolve into active galactic nuclei or quasars. A beam of intense radiation can then emerge from their poles that can seriously damage everything in its way. We recently observed one causing nova explosions in the giant elliptical galaxy M87.

Nevertheless, the supermassive black hole at the center of our galaxy is 4.3 million times the mass of the Sun and is relatively modest in size compared to the mass of our galaxy and other supermassive black holes elsewhere. We are located 26,000 light-years away from the center, and a significant amount of gas and dust along the way would block some of the radiation. The above scenario could happen in other galaxies, which contain supermassive black holes hundreds of times or more massive than the one we have in the Milky Way.

At most, the Earth’s atmosphere would get seriously damaged, and dark clouds would appear that would block the energy of the sun for years, causing nuclear war-like conditions and famine that could dent the human population to a large extent.

We think that our supermassive black hole has been in its active galactic nucleus phase or quasar many times in the past. In other galaxies, they last millions to even up to a billion years, but their length depends on the sources of matter the supermassive black hole can feed on. It can be from a recent galactic merger. Our galaxy has not collided with a huge one for 8 to 11 billion years since the Gaia-Encaladus-Sausage galaxy increased the number of stars in the Milky Way by about 50 billion.

Perhaps the next quasar phase will occur after the merger with the Andromeda Galaxy and its supermassive black hole, which is 20 to 30 times more massive than our own. This might be in 4.5 billion years or more. This behemoth of a unison between two supermassive black holes could do far more damage, and its galaxy would supply theirs, stir up and move our nebulae that can feed this voracious source of destruction for hundreds of millions or even a billion years.

The question was: How would earth be affected if the super massive black hole at the center of the galaxy turned into a quasar?