To make things simple -- The universe can be defined as a container having a set of laws which govern the way things behave and react with each other inside it. It can be of any form, from a round bubble to a flat surface or maybe just a computer simulation. The universe may contain multiple dimensions that may interact with each other. Each dimension, irrespective of its visibility would play a vital role in the universe. Whatever stuff happens inside the universe will be controlled by its laws and corresponding dimensions. One good example of this is the dimension of time and its coordination with space, in order for cause and effect to happen. Our universe is a container which holds everything around us. Here are a few ideas of what our universe is all about.
The Big Bang
The Big Bang is the explosion of our universe from nothing to something. What started it, remains unknown. The universe started to expand at an immense speed in a short period of time. During the initial stages, it was a super hot place. There was matter and antimatter which annihilated each other upon contact and released extreme amounts of energy. Luckily for us, after all this, there happened to be some matter left behind. As the universe began to cool down, gravity would bring this matter together to form planets, stars and galaxies. The big bang was discovered when a high powered radio receiver began to pull in some disturbance which was like a hissing sound. Many attempts were made to correct this, but they failed. Upon further research, it was concluded that this disturbance is the afterglow of the big bang which is known as the "cosmic microwave background". Thus came the Big Bang theory.
A Round Bubble
One idea, defines the universe as a 'Round Bubble' that exploded into existence in hyperspace. It is also known as 'The Bulk'. This explosion is known as 'The Big Bang'. This happened in less than a second. It was an explosion of something from nothing. In the beginning the universe was a hot place and then it cooled down. As it cooled, the force of gravity started to bind things together and the laws of physics and chemistry got things to react with each other, thus resulting in stars, planets, galaxies etc. It is now known to be rapidly expanding; as galaxies are observed to be moving away from each other.
According to this idea, our universe is a mere computer simulation. Its simply a bunch of codes written into the computer by some advanced being.
Scientists believe in the possibility of more than one universes residing in hyperspace. Each of these universes could hold exactly the same content, but with slight differences. These differences could be anything -- maybe in time, in the laws of physics etc. Multiverses are like bubbles that keep popping here and there in some greater system called as hyperspace. Each universe will hold its own characteristics. Based on their characteristics and laws of physics, universes may or may not support life. The outcome of each universe could be different. Eg. a universe with no gravity, could not form planets, stars, galaxies and life, for that matter. Even a minor difference in these laws can result in a totally different outcome over a given period of time.
The concept of multiverse comes to the rescue when the paradox of time is pondered upon. When scientists try to figure out the concept of time travel, it might be so, that if you travel into a different time, you actually travel into or create another universe where whatever changes you make there will have no effect in the original universe that you came from, but rather affect the universe you branched into resulting in a different outcome.
According to this theory, our universe a flat sheet, like fabric. It's like a page among many other pages in a book. The space between the pages is known as 'Hyperspace'. All the laws of physics and all the dimensions including the matter inside of it are stored upon it.
Hyperspace (The Bulk)
The concept of Hyperspace arises when we talk about multiverse. If there is more than one universe, there has to be a container for all of them to reside in. So scientists call this space as 'Hyperspace', also known as 'The Bulk'.
Space Time Continuum
According to physics, space and time are combined together to form a single continuum. Space consists of 3 dimensions and time consists of 1, which makes it the 4th dimension. The two go hand in hand with each other. In our universe, there exists matter which reacts with one another in 3 dimensional space and this all happens within a specific time period. Time plays a great role in the universe. Without time, there cannot be changes and reactions between the existing things in space. Because of time, everything is dynamic -- everything changes.
So far, we have an understanding of time as a unidirectional arrow known as 'The Arrow of Time'. This means time moves forward and only forward. The content in the universe is set to inevitably transform from an orderly state to a chaotic state which cannot be reversed. Eg. Once milk is added to your coffee, it cannot be reversed. The past holds the cause and the future holds the effect and that's it.
However scientists theorize the concept of time travel but face many paradoxes. It has been observed that time is not the same everywhere. Time is affected by factors like speed and the presence of massive objects. The faster you move, the slower times gets. If you travel at the speed of light, time stops and if you travel even faster, you start to go backward in time. Time also gets slower near massive objects. This is known as 'Gravitational Time Dilation' where the gravitational field of the massive object will have an effect on time by slowing it down.
Dark matter is invisible matter. It cannot be seen as it does not interact with light. You cannot touch it. It could be passing right through you, right now. Dark matter is thought to be a product of galaxies that relates only to gravity. Galaxies have been observed to rotate evenly, both, at the central and the extremities, like as if the entire galaxy is one solid piece. Such a thing would not be possible, if the central region of the galaxy, singlehandedly governed its spin, as the matter orbiting the central region would rotate faster than that at the extremities. The rotation and shape of galaxies estimates the presence of some extra mass out there that's unseen. So scientists decided to call it 'Dark Matter'. It's said that our universe consists of 23% dark matter which originated from the Big Bang.
It has been observed that space has been expanding rapidly, based on the observation of galaxies moving away from each other. We know that the galaxies are moving away as they appear red. The color red, indicates that a luminous source is moving away due to the red shift in the wavelength. It is estimated that this is caused by expansion of the universe. This is similar to the perceived change in pitch of sound from a car that moves past you at a high speed while constantly blowing the horn.
Scientists wonder as to what exactly causes this expansion. So they estimate the presence of some form of energy that opposes gravity and is responsible for this expansion. They call this energy 'Dark Energy'. Dark Energy is a property of space. It cannot be detected nor measured. It could also be some kind of energy fluid that surrounds everything. Observations have shown that energy particles emerge from nothing and disappear. So scientists believe that these particles could be dark energy. Dark energy comprises 73% of the universe.
Gravity is a force that was discovered by Sir Isaac Newton who questioned the entire phenomenon when he observed an apple falling towards the ground. Gravity pulls things together. Gravity and magnetism are not the same things. Gravity is responsible for the formation of planets, stars, galaxies etc. Matter that's suspended in space will tend to clump together because of gravity. Without gravity, we wouldn't exist as the matter required to create us, wouldn't be brought together. Everything in the universe would be spread out like dust and gas, with nothing really happening. The strength of gravity depends on the mass of an object. The more mass, the stronger is the gravity. The mass of large celestial bodies like the Sun, possess a strong gravitational force, that holds all the planets in their orbits. Scientists define gravity as a dent in the fabric of space, which is caused by a mass and it is this rule that explains, as to why planets revolve around the Sun. Gravity is a warp in the fabric of spacetime, that's caused by a massive body. The presence of a massive body, bends the fabric, which allows things to fall in.
The concept of Cosmological Constant was determined by Einstein. If the force of Gravity was all there is, it would have pulled everything in the universe together. All the planets would fall into the Sun and burn. There had to be a force that's opposite to that of gravity, in order to keep the planets in orbit. There had to be a balance in forces. So was founded the concept of Cosmological Constant. It is estimated that this force could be dark energy that's pulling things apart.
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