Why was Earth's rotation faster hundreds of millions of years ago, and what evidence supports this?

 This is how close the Moon was to the Earth about four billion years ago. Today’s view of the Moon today is to the left for comparison.

The Moon affects the Earth with tides, in the water and in the crust. This gravitational energy slows the Earth’s rotation. Being 81 times more massive, the Earth slowed the Moon’ s rotation to once every 27.8 days, called tidal lock. This lost energy had to go somewhere, so, being less massive, the Moon’s distance from the Earth had to take up the slack; energy is conserved. A higher orbit takes more energy, so the Moon moves away about one inch/2 cm with every 27.8 day orbit.

This has been measured very precisely. There is a laser reflector on the Moon set there by the Apollo astronauts used to measure this.

What is the oldest object on earth?

 The oldest physical objects currently sitting on Earth share a bizarre paradox: they are 2.5 billion years older than the planet itself.

In 1969, a 220-pound meteorite broke apart and fell over the town of Murchison in Victoria, Australia. When scientists analyzed the fragments, they found them peppered with microscopic grains of silicon carbide. These "presolar grains" are literal stardust—particles forged in the cooling gas of dying stars before the solar system even existed. In 2020, researchers dated the grains found in the Murchison meteorite to roughly 7 billion years old, making them older than the Sun.

However, if you restrict the definition to terrestrial objects—things that actually formed here on Earth—the title belongs to a collection of microscopic crystals in Western Australia known as the Jack Hills zircons. Earth formed about 4.54 billion years ago, initially as a hellish sphere of molten magma. Just 160 million years later, the Jack Hills zircons crystallized. Dated to 4.4 billion years old, these tiny, incredibly durable fragments survived billions of years of tectonic recycling, proving that solid crust and possibly liquid water existed much earlier in the planet's history than previously believed.

For something you can actually hold in your hand—an intact rock rather than a microscopic crystal—the prize goes to the Acasta Gneiss. Located along a remote river in the Northwest Territories of Canada, this body of metamorphosed granite dates back 4.03 billion years, making it the oldest known surviving piece of the Earth's original crust.

The Murchison meteorite, which fell in Australia in 1969, contains microscopic grains of stardust that formed 7 billion years ago. Photo by Marie-Lan Taÿ Pamart is licensed under CC BY 4.0.

Why do asteroids often fail to enter the Earth’s atmosphere?

 Asteroids don't hit a physical wall. They "fail" to enter either by completely missing our 67,000-mph planet, or by striking at an angle under ten degrees and skipping off like a stone.

The vast majority of space rocks simply miss us entirely. Earth is an 8,000-mile-wide target moving rapidly around the Sun, while asteroids follow their own distinct solar orbits. For an asteroid to enter the atmosphere, its orbital path and Earth's orbit must intersect at the exact same fraction of a second. Even near-Earth objects that astronomers classify as "close approaches" typically fly past millions of miles away, completely untouched by Earth's gravity or atmospheric drag.

When an asteroid's trajectory does perfectly align with Earth, the angle of approach dictates whether it penetrates. If a rock strikes the outermost layers of air too shallowly, it rebounds. These "Earth-grazing" meteoroids dip into the thin thermosphere, compress enough air to briefly glow as fireballs, and then exit back into deep space with their momentum largely intact.

People often confuse "entering the atmosphere" with "hitting the ground." Asteroids enter the Earth's atmosphere every day, but almost all of them are destroyed before reaching the surface. Because space rocks hit the atmospheric friction layer at speeds between 25,000 and 160,000 mph, the air in front of them compresses violently. This compression generates thousands of degrees of heat, causing the object to vaporize or explode miles above the surface. The 2013 Chelyabinsk meteor entered the atmosphere flawlessly but detonated 18 miles high with the energy of 500 kilotons of TNT, proving the atmosphere does not stop asteroids from entering—it simply destroys them after they do.

A long-exposure photograph captures an Earth-grazing meteoroid skimming the upper atmosphere above central Europe before bouncing back into space in 1990. Photo by Pavel Spurný is licensed under CC BY-SA 3.0.

What is the largest plant on Earth?

 In the past, things like this were expressed in terms of individual size. For example, when I was a child, the blue whale was often said to be the largest creature in the world. However, nowadays, there are more and more cases where we recognize them as the same individual based on their DNA.

According to the Guinness Book of World Records I read a long time ago, this was the world's largest plant.

That's a redwood tree . You can see its size when you compare it to the woman. There are still theories that it is the world's largest plant. Well, I suppose that's one correct answer. However, from the perspective of DNA, as mentioned earlier, this is the correct answer.

This is a mushroom called Armillaria mellea . When DNA analysis was conducted on this mushroom in Oregon, USA, it was found that all the individuals growing in a cluster over an area of ​​just under 9 square kilometers were identical.

It might seem like a bit of a stretch, but some argue that this is the world's largest.

Is it true that lava temperature inside Earth is near to Sun's matéria?

 Lava tops out around 2,200°F—nowhere near as hot as the Sun. But 4,000 miles beneath our feet, the Earth's solid iron core is hotter than the Sun's surface.

When a volcano erupts, the magma (which becomes lava once it reaches the surface) typically originates in the Earth's upper mantle or lower crust, just a few dozen miles down. While it is hot enough to melt steel, it is relatively cool compared to the deeper interior of our planet.

To find temperatures that rival a star, you have to travel straight down to the inner core. This solid ball of iron and nickel sits under crushing pressure, trapping primordial heat from the planet's formation 4.5 billion years ago, supplemented by the slow decay of radioactive isotopes. At this depth, the temperature reaches an estimated 10,800°F (6,000°C).

If you look up at the Sun, the part you see is the photosphere—its glowing outer surface. The temperature of the photosphere is roughly 10,000°F (5,500°C). So, the solid metal at the very center of our planet is actually slightly hotter than the fiery surface of the star we orbit.

But this comparison only works if you stick to the Sun's surface. If you compare the centers of both bodies, the Earth falls far behind. At the core of the Sun, nuclear fusion is constantly crushing hydrogen atoms together into helium. The temperature there reaches an astonishing 27 million °F (15 million °C).

Pāhoehoe lava flows across the coastal plain of Kīlauea on the Big Island of Hawaii. While hot enough to ignite wildfires, lava rarely exceeds 2,200°F, making it far cooler than the Earth's core. Photo by Brocken Inaglory is licensed under CC BY-SA 3.0.

Is it possible to reach Earth from Alpha Centauri within a human's lifetime, considering the distance of 4.3 light years?

 If a crew left Alpha Centauri at Voyager 1's speed, the trip to Earth would take 70,000 years. But by surfing the shockwaves of nuclear bombs, they could arrive in just 45 years.

At 4.3 light-years away, the journey spans roughly 25 trillion miles. Chemical rockets are hopelessly inadequate for interstellar transit, but physics does not forbid crossing that gulf in a human lifetime. It simply requires a complete reimagining of propulsion.

One theoretical method to achieve this is nuclear pulse propulsion, famously studied during the Cold War under Project Orion. Instead of burning liquid fuel, an Orion-style ship would eject thousands of small nuclear explosives behind it, riding the shockwaves of continuous detonations against a massive pusher plate. Calculations suggest this brutal but effective method could propel a massive ship to 10% of the speed of light, making a 45-year transit possible.

An illustration of LightSail 2, a spacecraft that demonstrated the viability of using solar radiation pressure for propulsion in Earth orbit. Photo by Josh Spradling and The Planetary Society is licensed under CC BY-SA 3.0.

An even faster alternative eliminates the need for the spacecraft to carry its own heavy fuel. Concepts like Breakthrough Starshot propose aiming an array of immensely powerful ground-based lasers at an ultra-thin, highly reflective sail. The continuous photon pressure could theoretically accelerate a craft to 20% of the speed of light. At that velocity, a probe or ship from Alpha Centauri would reach Earth in just over 20 years.

If an advanced civilization could build engines capable of pushing a ship to 99% of the speed of light—perhaps utilizing antimatter annihilation—the journey takes on an entirely different character due to special relativity. While an observer on Earth would watch the ship travel for about 4.3 years, time dilation means the crew onboard would experience the entire transit in just a few months. The true barrier is not time, but energy: accelerating even a small shuttle to relativistic speeds would require more energy than the entire modern world consumes in a year.

Alpha Centauri A and B, the two brightest stars in the closest star system to Earth. Photo by ESA/Hubble is licensed under CC BY 4.0.

What's the closest known black to Earth as of 2025?

 If the Milky Way were a football field, the closest known black hole to Earth sits on our one-yard line. Meet Gaia BH1, a completely silent, invisible ghost just 1,560 light-years away.

Discovered in late 2022 by the European Space Agency's Gaia mission, it is located in the constellation Ophiuchus. For years, astronomers believed other objects held this title. In 2020, a system called HR 6819 was declared the closest black hole at just 1,000 light-years away, but follow-up observations proved it was a "vampire" star system with no black hole at all. As of 2025, Gaia BH1 remains the undisputed record-holder.

The reason it remained hidden for so long is its dormancy. Most black holes are discovered because they are "active"—meaning they tear apart companion stars and gorge on the resulting gas. This violent feeding process heats the gas to millions of degrees, emitting intense X-rays that space telescopes can easily spot. Gaia BH1, however, is not feeding. It emits absolutely no light or radiation.

Astronomers found it by looking at its dance partner. Gaia BH1 is locked in a binary system with a normal, Sun-like star. By analyzing data from the Gaia spacecraft, researchers noticed this star was wobbling in space, orbiting an invisible object every 185.6 days. The unseen object has a mass nearly 10 times that of the Sun—far too heavy to be a neutron star or a white dwarf. It could only be a black hole.

The Milky Way is likely teeming with these dormant black holes. In the years since finding BH1, the Gaia mission has also discovered Gaia BH2 (3,800 light-years away) and Gaia BH3 (a massive 33-solar-mass black hole about 1,926 light-years away).

While 1,560 light-years sounds far, it is practically right next door in cosmic terms. Astronomers estimate there are upwards of 100 million stellar-mass black holes wandering through the Milky Way. Given those numbers, it is a statistical certainty that an even closer, dormant black hole is out there right now, waiting to be discovered by its gravitational tug on the stars around it.

An illustration of the Gaia BH1 system, showing the dormant black hole distorting the background starlight near its Sun-like companion. Photo by International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani is licensed under CC BY 4.0.

Why was Sita born from the Earth and not a womb?

It's backstory is in Uttar Kand where it's written that a daughter of Sage Kushadhwaja was very beautiful and many men wanted her hand but he refused them all saying that he wanted Lord Vishnu to be her husband. A demon named Shambhu due to this killed Kushadhwaja and his wife due to grief entered fire. Unprotected Vedvati left for the woods and wore matted locks and black antelope’s skin and did penance to get Lord Vishnu as her husband.

Ravana once saw her and praised her beauty. She introduced herself and called her Vedas personified. He proposed her and called her penance unworthy as she was very beautiful and young. When she rejected his offer, he grabbed her hair which angered her. She cut her hair through her hand which magically became as sharp as blade due to her penance. She entered fire vowing to return and destroy Ravana.

She later was reborn on a lotus with fragrance of lotus. Ravana saw her and brought her in his palace but his ministers seeing her told him that she would be the reason of his destruction. Ravana got angry and threw the baby in the Sea which was taken to Mithila by the waves and when Janaka was doing ritual ploughing ,he found the baby (reborn Vedvati) in the line of ploughed field and therefore named her as Sita and adopted her as his child. He gave her to his Queen and reborn Vedvati became Sita, Princess of Mithila.

Ironically, if Ravana had not thrown the baby despite his ministers warning him, Sita would not be brought up by Janaka but Ravana. But, he was unworthy to become father of Mahalakshmi and therefore she chose Rajrishi Sheerdhwaj Janaka as her father and fate played it's course.

Source- Uttar Kand, Valmiki Ramayana

What is the deadliest place on Earth?

 The deadliest place in the world can be measured in different ways:

1. Most gruesome death
2. Fastest death
3. Fundamentally hostile to life

For a gruesome death, I would recommend a final cannonball into Lake Irazú in Costa Rica. This lake is an acidic crater lake where a gruesome death is guaranteed!

In my opinion, the candidate for the fastest death is the Kilauea volcano in Hawaii. This volcano can reach temperatures well over 1000°C, which guarantees an exceptionally quick death.

Finally, I would like to mention the coldest places in the world, since cold makes life impossible. The cold brings chemical processes to a standstill, thus halting all forms of life. One such place is the Pole of Cold, a high plateau in eastern Antarctica where temperatures can plummet to -90°C.

Are there concrete plans to remove old satellites and debris from Earth's orbit?

 Plans were circulated, but it turns out to be a devilishly difficult problem to solve, incredibly expensive, and not as big as most people think.

Most satellites are properly disposed of these days. Satellites in low Earth orbit either re-enter the atmosphere on their own due to air resistance or are intentionally removed from their orbit towards the end of their lifespan. Satellites in geosynchronous orbits are moved to a graveyard orbit where they cannot interfere with active satellites.

However, this doesn't mean that debris isn't a problem. Everything from loose cameras to paint splatters is floating around in Earth's orbit, and all of these things can be deadly if they hit an astronaut or satellite at orbital speeds.

The problem with collecting debris in space is that the large objects are easy to detect and avoid, while the really small objects - which can still be deadly - are extremely difficult to detect and therefore difficult to capture with a debris-collecting satellite.

The low-hanging fruit—which we'll probably do first—is moving satellites that die prematurely. When a satellite is placed into a geosynchronous orbit, the plan is always to move it to a graveyard orbit at the end of its life, but if the satellite dies prematurely, it's stuck where it is. If we could launch a cheap shuttle that would attach itself to the dead satellite and move it to the graveyard orbit where it was meant to end up, that might be worth considering.

It's worth noting that every single graphic that attempts to show the "crowded" space around the Earth is misleading. Consider images like this one:

...and this...

These images give the impression that we can barely squeeze in another satellite. The problem is that each of these graphics massively overestimates the size of the satellites.

A typical satellite is about the size of an SUV, but in the second image above, it's depicted as if all the satellites were the size of the greater Atlanta area. In the first image, the satellites are the size of several countries. I understand why they do this—if they showed the satellites to scale, you wouldn't be able to see them—but most people take these graphics at face value.

Space debris is not yet a crisis, but it is something we need to think about, and thankfully some people are.

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

 Earth hides oceans locked in solid rock and a metal core burning as hot as the Sun. Yet if you shrank the planet to the size of an apple, the atmosphere would be thinner than its skin.

This fragile envelope of life-supporting gas is incredibly shallow. Looking at photographs taken from the International Space Station, you can see this boundary as a razor-thin, glowing blue line separating the planet's surface from the deep black vacuum of space. The troposphere, which contains about 75% of the atmosphere's mass and almost all of its water vapor, extends only about 5 to 12 miles (8 to 20 kilometers) above the surface—a mere fraction of the planet’s 7,917-mile (12,742 km) diameter.

The thin blue line of Earth's atmosphere separates the planet from the darkness of space, as photographed from the International Space Station with the Moon in the background. Source: Wikimedia Commons.

Beneath this thin shell lies a planet of extremes and hidden reservoirs:

• An "ocean" locked in stone: Deep within the Earth’s transition zone, between 250 and 410 miles (410 to 660 kilometers) below the crust, lies a vast reservoir of water. It is not a liquid sea, but rather water molecules chemically bound inside the crystal structure of a rare, high-pressure mineral called ringwoodite. If this transition zone is fully saturated, it could hold as much water as all of Earth's surface oceans combined.
• A lumpy gravity field: Earth’s gravity is not uniform. Because the planet’s mass is distributed unevenly due to deep mantle convection currents and the uneven thickness of the crust, gravity varies by location. For instance, parts of Canada's Hudson Bay region have lower gravity than surrounding areas, a remnant of the last ice age when thick glaciers compressed the crust, which is still slowly rebounding.
• The driest place is frozen: While the Sahara and Atacama deserts are famous for their dryness, the driest place on Earth is Antarctica's McMurdo Dry Valleys. These ice-free valleys have extremely low humidity, and powerful katabatic winds sweeping down from the mountains at speeds up to 200 mph (320 km/h) evaporate any snow. Some sections of these valleys have not seen rain or snowfall in nearly two million years.
• A solid furnace: Earth's inner core is a solid sphere of iron and nickel with temperatures reaching up to 6,000 °C (10,800 °F)—matching the surface temperature of the Sun. Despite being hot enough to melt any known metal, the pressure at Earth's center—about 3.6 million times atmospheric pressure—squeezes the atoms so tightly that they cannot transition into a liquid state.
• A planetary thermostat: Earth is the only known planet in the solar system with active plate tectonics. Beyond shifting continents, this process acts as a global thermostat through the carbonate-silicate cycle. Subducting plates carry carbon dioxide locked in rocks deep into the mantle, while volcanoes release it back into the atmosphere, stabilizing Earth's climate over millions of years.

What is the strangest place on Earth?

 Not many people can claim hell as their birthplace.

But Todd Domboski and the few thousand former residents of Centralia, Pennsylvania, come closest to that distinction.

Signs warn visitors of the dangers of death by suffocation or being swallowed by the ground, but the old mining town of Centralia, Pennsylvania, was once home to more than 1,000 people.

Now it is nothing more than a smoldering ghost town that has been burning for half a century.

It started with a fire that was intentionally set to burn out a landfill for Labor Day in 1962.

The problem was that the dump was also an old mine connected to a maze of abandoned underground mine tunnels full of coal.

Although the city managed to extinguish the fire above ground, a much larger inferno burned beneath it, eventually making its way under the city center of Centralia.

The fire was so widespread, destructive, and endless—it is said that there is enough coal underground to stoke the fire for another 250 years.

- that in 1980 a $42 million plan prompted most residents to move (most houses were demolished), leaving only about a dozen survivors behind.

What place on Earth would be more inhospitable to human life?

 Unexpectedly, it's neither the Sahara Desert, nor the icy plains of Antarctica, nor the dangerously deadly Amazon rainforest…

Ladies and gentlemen, I present to you Rannoch Moor , in the heart of Scotland.

Rannoch Moor is only six kilometers in diameter and doesn't seem so bad. But a few years ago, one of those crazy people who want to conduct survival experiments decided to challenge Rannoch Moor.

See that beautiful hut? Well, that's where they found 29-year-old David Austin, dead from hypothermia after trying to survive on Rannoch Moor.

The problem with this place is that it's very flat and open. And worse: the ground isn't solid. It's an area full of moss, where you'll walk through muddy swamps and soggy marshes.

There's nowhere to rest. There are no trees. There's no dry land. And if you try to cross Rannoch Moor even a little bit faster than normal, you're quite likely to badly twist your ankle.

What are some unusual natural phenomena that can be observed on Earth?

 Everyone dies, but it's such a rare event that it only happens once in a lifetime to anyone or anything. I think death is the rarest phenomenon that can ever occur to any being.

In the case of humans, death is extremely rare, and once it occurs, we are wiped off the face of the Earth, but I think we are simply transforming into some other kind of energy.

In nature, there are phenomena that restore what has been destroyed.

The same thing happens to us. We don't die; we simply change to adapt. Nature wastes nothing, not even waste.

I believe death is one of the greatest phenomena that occur in nature.

Edward Bohren, Shipwreck, Namibia

What are the places on Earth that are inaccessible to humans?

 This is Gangkhar Puensum, the highest unclimbed mountain in the world at 7,570 meters. No one in history has ever reached the summit, and likely no one will for a long time.

The mountain is located in Bhutan, which has banned climbing for religious reasons, so reaching the summit is not only physically difficult, but also legally impossible.

The highest peak in this category is Muchu Chhish in Pakistan, at 7,453 meters, an incredibly challenging mountain that has only been climbed twice in history.

As a species, we have been both to the Moon and to the deepest part of the ocean, but there are still several dozen mountains around the world whose peaks have never been reached by anyone, making them perhaps the most difficult places to reach on the entire planet.

What is the deadliest place on Earth?

 The deadliest place in the world can be measured in different ways:

1. Most gruesome death
2. Fastest death
3. Fundamentally hostile to life

For a gruesome death, I would recommend a final cannonball into Lake Irazú in Costa Rica. This lake is an acidic crater lake where a gruesome death is guaranteed!

In my opinion, the candidate for the fastest death is the Kilauea volcano in Hawaii. This volcano can reach temperatures well over 1000°C, which guarantees an exceptionally quick death.

Finally, I would like to mention the coldest places in the world, since cold makes life impossible. The cold brings chemical processes to a standstill, thus halting all forms of life. One such place is the Pole of Cold, a high plateau in eastern Antarctica where temperatures can plummet to -90°C.