Why do some theories suggest the universe originated from other dimensions, and what do they imply about our understanding of reality?

 The Big Bang might not have been an explosion from nothingness, but a violent collision between two parallel dimensions.

This idea emerges from a mathematical necessity to solve some of the most stubborn paradoxes of our origins. In the standard cosmological model, the universe expands from a singularity—a point of infinite density and temperature where all known laws of physics completely break down. Because singularities are mathematically impossible to describe with current physics, theoretical physicists have sought alternative models to explain how everything began.

One of the most prominent alternatives comes from string theory and its extension, M-theory. These frameworks require the existence of extra spatial dimensions—up to 11 in total—for their mathematics to function. In this view, familiar three-dimensional space is just a single membrane, or "brane," floating within a much larger, higher-dimensional space known as the "bulk."

This leads to the Ekpyrotic model of the universe. This theory suggests that the universe was born from a collision between two parallel branes across a fourth spatial dimension. When these branes smashed together, the immense kinetic energy of the impact was converted into the heat, light, and matter that filled the early universe. This model neatly explains the uniform temperature of the cosmic microwave background without relying on the rapid, unexplained expansion known as cosmic inflation.

If these dimensional theories hold true, they imply a radical shift in how reality is understood:

• A cyclical cosmos: Instead of a universe with a definitive beginning and a cold, expanding end, the brane collision model allows for a cyclic universe. Branes could pull apart, empty out over trillions of years, and eventually crash together again, creating an endless loop of cosmic death and rebirth.
• Leaking gravity: This framework offers an elegant explanation for why gravity is drastically weaker than the other fundamental forces, like electromagnetism. While light and matter are stuck to the three-dimensional brane, gravity might be free to propagate across the extra dimensions, diluting its strength in the observable universe.
• Hidden worlds: Reality would be vastly larger than what telescopes can see. Entire other universes could be hovering mere fractions of a millimeter away in a higher dimension, completely invisible and inaccessible except perhaps through the subtle pull of gravity.

Ultimately, these theories suggest that the observable universe is just a small cross-section of a much deeper, vastly more complex structure.

Why does the universe create objects as extreme as black holes?

 Here main player is gravity. When a massive star(>3 solar masses) collapse due to end of it’s fuel,then outward pressure is lower than the inward gravitational force and it creates a black hole.

According to GR, space time curvature bends heavily in case of a black hole. Thus we see that when gravity wins over expansion force,that creates high density region of mass so that nothing can escape from it nor even light. It is called black hole.

Now,unlike gravity creates star, galaxy, cluster ,it ,creates also black holes. In center of every galaxy there is a supermassive black hole.

The relationship is better described as mutual sculpting — the galaxy feeds the black hole, and the black hole regulates the galaxy. It's a deeply coupled system, not a one-way preservation mechanism(by Cormendy and Ho’s research paper).

Image credit: vox

How does the spin and geometry of the universe tie into the Big Bang and everything we see around us now?

 In 1949, mathematician Kurt Gödel proved that a spinning universe could theoretically allow time travel into the past, but observational data has since revealed a much more structured, non-rotating reality. The spin and geometry of the cosmos are intricately tied to the Big Bang, and they perfectly dictate why the modern universe is organized the exact way it is.

Starting with geometry, the observable universe is astonishingly "flat." In cosmology, a flat universe does not mean space is a two-dimensional plane. Instead, it means that standard Euclidean geometry applies on the largest cosmic scales: parallel lines will never intersect, and the angles of a massive triangle drawn between three distant galaxies will add up to exactly 180 degrees. This flatness is a direct consequence of a brief moment immediately following the Big Bang known as cosmic inflation. During inflation, space expanded exponentially. Just as blowing up a massive balloon makes its curved surface appear flatter to an ant walking across it, this immense expansion stretched the fabric of the universe so intensely that any initial curvature was completely ironed out.

When it comes to spin, modern astrophysics points to a universe that does not rotate at all. Detailed maps of the Cosmic Microwave Background—the lingering thermal radiation from the Big Bang—show no evidence of cosmic rotation. If the universe were spinning, it would inherently possess an axis of rotation, meaning space would have a "preferred" direction. This would violate the cosmological principle, the foundational rule that the universe is isotropic, meaning it looks fundamentally the same in every direction.

These two traits—a flat geometry and a lack of spin—are the reasons the sky looks the way it does today. Because space is flat, light from distant galaxies travels in straight, predictable lines over billions of light-years, allowing for the stable formation of cosmic structures. Because it does not spin, there is no physical center to the universe and no cosmic edge. Galaxies and galaxy clusters are distributed evenly throughout the cosmos, existing in a delicate, unspooled balance rather than swirling around a giant central vortex.

Why does the universe allow black holes to exist at all?

 There exist black holes in the universe because any star which is greater than 3 times solar masses can go into three types objects in their final phases.They may be white dwarf,neutron star or black hole. So forming a black hole is an inevitable phenomenon In our cosmos.

Now turn to the main question, why?

Because black hole regulates star formation in it's host galaxy. There is a huge correlation between black hole and galaxy co-evolurion. So without black hole, galaxy might not be fully structured.

In center of each galaxy ,there is a supermassive black hole. It preserves angular momentum of that system. When there exist too many masses in a small region,they don't let go anything outside nor even light. So these masses creates curve in space-time curvature and gravity is too high.This high density region is known as black hole.It is also a consequence of theory of general relativity by Einstein.

So existence of black hole in space proved by theoretically and experimentally both.

Why do supervoids exist in the universe?

No one knows everything for sure about the dark spaces. We have theories. But you're right, Supervoids exist. They are the cold, empty deserts of the universe.

To understand them, you must look back to the beginning. When the universe was young, matter was never perfectly smooth. Tiny ripples. Existed. Gravity began its long, slow work. It pulled things - the heavy parts close together.

These parts became bright stars, they became galaxies. They formed thick webs. Gravity built these structures, but it stole from the other places. The blank parts grew even emptier - A thing called dark energy joined the long fight.

We don't know exactly when. But it pushes everything apart - stretches the void out wide.

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Gargantuan. Quiet. Deep spaces.

Gravity won the battle in the bright clusters. The dark voids were left behind.

What is the most disturbing fact about the universe?

 The creepiest part of the Universe is that it's mostly patch black empty space.

If the milky way and andromeda galaxies merge it's unlikely any stars will collide because of staggeringly empty space.

If you still can't comprehend how empty space is, here is an example.

Imagine you are traveling in space and a huge cloud of sand is approaching at high speed. Even if your ship gets hit by one grain of sand, it can severely damage your spaceship.

Except that wouldn't happen because each grain of sand on average is TEN KILOMETERS apart from every other grain of sand.

That much empty the space.

What are some mind-blowing facts about the universe?

 

• Our solar system’s biggest mountain is on Mars.

• Space has no atmosphere.
• Sound cannot travel in space as there is no medium

• The nearest star to earth is 4.2 light-years away.

• A spoonful of a neutron star weighs about a billion-ton.

• You can't cry on space, because your tears won't ever fall.

• In 1977 we received a signal from deep space that lasted 72 seconds. We still don't know how or where it came from.

• Saturn's rings are not solid. They are made up of bits of Ice. Dust and Rock.

• A single day in planet Venus is longer than its year.
• Venus takes 243 Earth days to rotate once on its axis. The planet's orbit around the Sun takes 225 Earth days.)

• The Milky Way is a huge city of stars, so big that even at the speed of light, it would take 100,000 years to travel across it.

• Black holes are so dense that even the light cannot escape.

What is the largest object in the universe?

 A question of how big something can be.

When speaking about the biggest object in the universe, you must always remember galaxy IC-1101.

Why don’t we see how big it actually is?

Milky Way:

Our galaxy, the Milky Way, is 100,000 light-years across, with an estimated 400 billion stars in it. 100,000 light-years would be 1,000,000,000,000,000,000 kilometers across. Now, let’s see how long it would take you, to cross it, with humanity’s fastest spacecraft. Let’s start with the math. As stated earlier, the Milky Way galaxy is 100,000 light-years across, each light-year is approximately 6 trillion miles, and for us to cross just one light-year, it would take us nearly 20,000 years with humanity’s fastest spacecraft New Horizons. Unrealistically, It would take you a wopping 2 billion years to cross our own galaxy with the fastest thing we have.

Andromeda:

The Andromeda galaxy has more than twice the amount of stars than our galaxy has (one trillion to be exact), and is 2.5 million light-years away from Earth. Now, this galaxy is about 140,000 light-years across, compared to 100,000 light-years the Milky Way. Doing the same math, it would take you 2.8 billion years to cross it with the exact same spacecraft, without adding the time it would take you to get there.

Now here ‘s where things get big:

IC 1101:

This galaxy is approximately 1.2 billion light-years away from Earth. It has 100 trillion stars, making literally a dot of the Milky Way, and the Andromeda Galaxy. This galaxy is 50 times the size of the Milky Way, and 2,000 times as massive. Doing the math, it would take us a mind-boggling 100 billion years to cross that galaxy. I must confess I was getting pretty excited while making this answer.

We are as tiny as we can get.

Is it possible to go outside the universe or is there an end?

 Well, our universe has got a very peculiar spacetime geometry (please have a look at my post (The shape of our Universe…… is flat, a sphere, a doughnut? What is outside, more space? Does it have an edge, a centre? A beginning, an end? It pop up from a singularity (what was it?) It’s expanding into what? (Part 1 of 3).). Our universe has got neither a centre nor an end since the main corpus (body) of it has got an Euclidean geometry, and near the borders you find Riemannian geometries full of curved trajectories which always take you back when traveling along straight trajectories according to your navigation instruments. The only way to go outside our universe is by means of a gigantic quantum wormhole which can take you to “another” universe. If you want to travel to any star within our own galaxy using a gigantic quantum wormhole, you’d need the energy of several thousands of stars to build it. But to build a gigantic wormhole to travel to another universe, you’d need the energy of an entire galaxy or the energy of a huge quasar. Now you know, you should start building a quantum wormhole now, but please be careful when selecting the universe you wish to travel to, it must have the same physical laws (and its constants) as ours. Otherwise (with different physical laws), as soon as you pop up in the other universe, you would be immediately disintegrated (in a tremendous cosmic explosion).

What are some mind-blowing facts about the universe?

 

• Sunsets on Mars are blue.

• Pluto is smaller than the United States.

• We know more about Mars and our Moon than we do about our oceans.

• Lemons can cost $2,000 each to ship into space.

• Space is full of space junk, which is small micrometeorites or man-made space debris. They are a huge hazard to spacecrafts.

• A year on Venus is shorter than a day there.

• You would last about 15 seconds in space without a spacesuit.

• There's a reason why space appears black. We don't see stars in every direction because some stars haven't been around long enough for their light to reach us.

• The sun makes up 99.8% of the solar system's mass.

• Venus is the hottest planet in the Solar System, even more so than Mercury, despite the latter being closer to the Sun. This is because of Venus’ thick atmosphere, which essentially traps heat in.

• It rains diamonds in Saturn and Jupiter.

• Our moon is moving away from Earth at a rate of 1.6 inch (4 cm) per year.

• Some spacesuit helmets have a Velcro patch, to help astronauts itch.

• Saturn is the only planet that could float in water. (if we had a sea large enough and Saturn wasn’t made mostly out of gas.)

• Asteroids are the byproducts of formations in the solar system, more than 4 billion years ago.

• The first living mammal to go into space was a dog named “Laika” from Russia.

• The word “astronaut” means “star sailor” in its origins.

• “NASA” stands for National Aeronautics and Space Administration.

• Gennady Padalka has spent more time in space than anyone else. He is an RKA cosmonaut and has spent 879 days in space.

• Mercury has no atmosphere, which means there is no wind or weather.

• Neutron stars are city-size stellar objects with a mass about 1.4 times that of the sun.

• Red Dwarf stars that are low in mass can burn continually for up to 10 trillion years.

• There are more trees on Earth than stars in the Milky Way. There are about three trillion trees on our fair planet, and only a measly 100-400 billion stars in the galaxy.

• It would take a modern spacecraft 450,000,000 years to travel to the centre of our galaxy.

• Earth is the only planet not named after a God.

• There are probably more than 1,000,000,000,000,000,000,000,000 (1 septillion) stars in the universe.

• There is probably a supermassive black hole at the centre of our galaxy.

Source: 15 facts about space that will blow your mind

100 Interesting Space Facts That'll Blow Your Mind | The Fact Site