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?

What is actually meant by Hindu texts when they said Earth was on top of elephants which were on top of a giant turtle?

 

Is planet Earth on top of four elephants which in turn are on the top of a giant turtle?

What does this mean?

Scriptures are based on seven stage muscle tone based thinking. The fourth stage is symbolized by water and represents Vishnu.

Vishnu is the Preserver and keeps life between a lower limit called Positive attitude and an upper limit called Negative attitude.

The Positive attitude is symbolized by turtle and the Negative attitude by Earth.

In Kurma or Turtle incarnation Vishnu prevents the ocean floor from sinking. The ocean floor symbolizes the Positive attitude.

In Varaha incarnation Vishnu restores the Earth from the bottom of the ocean floor, hidden there by the demon Hiranyaksha. Earth here symbolizes our Negative attitude.

If our Negative attitude below our Positive attitude we will feel that we have achieved more than enough and therefore, we won’t feel like doing anything. Vishnu restores the Negative attitude to its default level.

Purusha / Vishnu are three dimensional at the level of the navel. The four elephants symbolize this fact.

Thus, the Earth on top of four elephants, which in turn are on a giant turble symbolize the default state of human mind.

If Earth was shrunk down to the size of a grape, how big would the Galaxy be?

 Let's round the diameter of a grape up to about one inch (2.5 cm), just for simplicity's sake.

The diameter of the Earth is about 7917.5 miles (12,742 kilometers), which translates to 501,652,800 one-inch grapes. Give or take. That is to say that the Earth is currently 501,652,800 times bigger than a grape, so in order to make them the same size, we would need to scale down the Earth by 501,652,800 times.

We now assume that the same proportional shrinkage takes place in all of space, or at least our galaxy.

Doing this makes the solar system at least navigable. The Sun, which is now about the size of a Smart Car, is a little less than 1,000 feet (about 300 meters) away from our little grape. That’s a short little jog, or about the height of the Eiffel Tower. Be sure to stop to smell Venus on the way — it smells like rotten eggs!

Pluto is still over seven miles (over eleven km) away from the Sun, so we’ll need a vehicle if we aren’t in the mood to hike. Just to arrive at an icy pebble about 1/5 of an inch (1/2 of a centimeter) in diameter. You may (or may not) have noticed Jupiter looking like an overinflated basketball along the way. More likely you noticed Saturn and its spectacular rings, now just under two feet across.

But we’re not thinking big enough. Granted, the Milky Way is a relatively small galaxy, with a distance of "only" about 100,000 light-years across. Scaling that down by the same ratio, the galaxy would now be 0.0002 (1/5,000) light-years across.

To turn that into miles, we must consider that one light-year in reality is almost 5.9 trillion miles (9.5 trillion km). In our scale model, that same light-year is now a little more than 11,718 miles (18,859 km) -- a little greater than the distance from the United Kingdom to New Zealand.

So already we’ve outgrown our car. We’ll need a commercial plane and most of a day to travel a single light year. But if we want to get anywhere, the nearest star will require that we make that trip four times and then some, so we’ll need a high-speed jet with enough fuel to travel completely around the Earth (the real Earth) twice without refueling. (One commenter suggested a rocket, which is probably a better time-saver).

We’ve now made it to the Alpha Centauri system. Congratulations. That flight was probably miserable.

But we’re not even getting started. We’re trying to traverse the galaxy, after all, and we’ve only jumped from one star system to its nearest neighbor.

This scaled-down galaxy is now 1,171,826,372 miles (1,885,871,741 km) across. Essentially we’ve shrunk the Milky Way to fit inside our Solar System; the edges of the galaxy would be found somewhere between the orbits of Saturn and Uranus — still twenty-five thousand times further than humans have traveled thus far. If you want to get a feel for how long that trip would take, I recommend this map (which shows that even light itself would take more than an hour and a half to cover the distance):

If the Moon Were Only 1 Pixel

Even at over 500 million times smaller than actual size, our galaxy is still unfathomably massive.

Moral of the story: I hope you like your little grape. It’s almost definitely the only grape you’ll ever get. Do take care of it.

Note: the above calculations are completely linear. I only used diameter. If accounting for volume, the numbers would be different. For example, I had said that Earth is about 502 million times larger than a grape, but if measured by volume, Earth becomes more than one septillion times larger than the grape… (that’s a 1 with 24 zeroes). To make that useful we’d have to compare it to the volume of the galaxy, but I don’t know how to measure that (and I don’t think anyone else does either). Because I wanted to talk about travel times anyway I felt a linear measure was sufficient.

Why doesn't the ISS crash into the Earth?

 There is a very small air resistance at the altitude of the ISS. This drag causes the ISS to lose up to 5 cm/s (0.1 mph) of velocity and 100 meters (330 ft) of altitude each day.

To compensate for this, about once a month the ISS fires its thrusters to increase its altitude. This maneuver is called a reboost, it is done by modules at the rear of the International Space Station (ISS), such as the Progress, ATV (pictured below), or if necessary the Service Module, itself.

There are two types of reboost - single burn and two-burn. A single burn reboost involves one firing of the thrusters. The impact of the firing is an increase in altitude on the opposite side of the planet. This type of reboost is done for small reboosts because it does change the eccentricity of the orbit.

The general idea is that if we create a delta-v at a point, that delta-v will affect the vehicle throughout its orbit. So in the above picture we can see that for the first half of the orbit (moving counterclockwise) it lifts the ISS away from its nominal orbit. But once we pass the 180 degree point, we can see that the delta-v now lowers the ISS back to its original point.

A two burn reboost essentially starts like a single burn reboost, but at the 180 degree point it fires the thrusters again to cancel out the original delta-v. This results in the ISS being in a new circular orbit at the altitude of the second burn.

The design envelope of the ISS is to keep it between 280 km and 460 km. But we don't usually reboost up to 460 km and then drift down to 280 km. The reason for that is that we don't want to make the visiting vehicles work so hard and burn so much fuel to get up to 460 km.

So, that means we do smaller, more frequent reboosts. They occur about once a month and involve a delta-v of about 2m/s and involves firing thrusters for about 900 seconds, although that is variable depending on which module does the burn.

Most often, reboosts are done by an attached Progress module. We usually use the smaller thrusters on the vehicle, because we do not want the acceleration on the vehicle to greatly affect ongoing payload science. Typically we use four thrusters that each have a force of 13.3 kg-f (29.3 lbf).

Is the Earth floating, flying, or falling?

 When I was in school, I saw the solar system in a 2-dimensional plane like this:

When we look at the solar system in static 3D, we will definitely think about the existence of a hypothetical invisible field that holds the planets and the sun from falling, called ether, like the animation below:

The view of the existence of ether is actually just an illusion and will change when we include the fourth dimension, namely motion, in the solar system simulation, so it will look like this.

Of course, the solar system's helical motion isn't entirely accurate, as the planets' actual tilt around the sun is 60 degrees. So, the most realistic depiction of the solar system's motion is something like this.

It's very complicated, isn't it?

So, is the Earth floating, flying, or falling? I prefer to use the words "thrown" and "bound" by the sun's gravity, which also moves with the galaxies thrown around in this vast universe.

Perhaps someday this explosion will turn into a Big Crunch, and everything will return to its original state, only to explode again, forming a new universe. And so on, endlessly.

What is the hardest substance on Earth?

 Human technology progresses more and more every day. Modern industrial processes require materials capable of withstanding immense pressures while retaining their shape and integrity. For this, engineers generally turn to metals due to their wide availability and malleability.

But what is the strongest metal, and just how strong is it?

The answer to this question depends on how the question itself is framed. Does the practicality of using a metal in any significant amount count? Does it have to be a natural metal, or are alloys considered? What's the difference between strength and hardness? This article attempts to examine the multiple answers to this question, covering each metal with a claim to the title, and arguing its case.

Note: For the sake of clarity, the 'strength' considered is tensile strength, which is how much force an object can withstand before warping, unless otherwise stated.

The Strongest Natural Metal: Tungsten

As far as pure metals go, tungsten has the highest tensile strength, with an ultimate strength of 1510 megapascals. Tungsten also has the honor of having the highest melting point of any unalloyed metal and the second highest melting point in the whole periodic table—only carbon can withstand hotter temperatures. Tungsten is very dense and brittle, making it difficult to work with in all but its purest forms. Tungsten is commonly used in electrical and military applications, and you may find tungsten filaments in light bulbs and tungsten coating that adds a real punch to projectiles. It is also a common component in steel and other alloys, where even a small amount can significantly increase the strength of the alloy.

A megapascal (MPa) is a metric pressure unit, mostly used in hydraulic systems that gauge high pressure ratings, that equals 1,000,000 newtons per square meter (which is a pascal). 1 MPa is equal to 10 Bar.

The Strongest Alloy: Steel

Alloys are a constantly changing field, as researchers attempt to create ever-stronger combinations of elements. Generally, the strongest alloy is steel mixed with a few other elements. Vanadium steel alloys seem to be particularly promising, with several companies releasing variants with ultimate strengths of up to 5205 MPa. The steel that holds this distinction is called Micro-Melt® 10 Tough Treated Tool Steel.

Steel itself is an alloy of iron and carbon, although other elements can also be used. Steel is a highly versatile alloy, meaning a form of it can be made to meet almost any specifications. Steel has been in use for millenniums but became a more exact science during the Renaissance (1300-1700).

The Hardest Metal: Chromium

The 'hardness' of a mineral is generally determined by the Mohs scale and is defined as the scratch resistance of a mineral. Diamonds are the hardest minerals known to man, but what is the hardest metal? That honor goes to chromium, a metal perhaps best known as the key ingredient in stainless steel. Chromium is also commonly used in chrome plating, which acts as a form of protection against corrosion and physical damage.

Chromium has been recognized for its unique traits since the Qin Dynasty in China, when weapons and armor were coated with the metal and survive to this day, uncorroded and in perfect shape.

The Most Useful Strong Metal: Titanium

With an ultimate strength of about 434 MPa, titanium is the perfect blend of strength and practicality. Its low density makes it perfect for industrial uses requiring a strong metal with a high melting point. Indeed, titanium has the highest strength-to-weight ratio of any natural metal known to man. Pure titanium is stronger than standard steel, while being less than half the weight, and can be made into even stronger alloys. Because it is also fairly common, it's no wonder that titanium is used for a multitude of purposes. When it comes to manufacturing, the only strong natural metal worth caring about is titanium.

These metals are the backbone of modern industry, providing the support that keeps our daily lives running smoothly. Whether in the tip of a pen, on the fuselage of an airplane, or in the beams of a tall building, we rely on metals to protect us as we seek to progress ever further. We should consider ourselves lucky that, no matter what our needs, there is something in nature to cover them.