Understanding Universe

Understanding Universe

When it darkens, we see the beauty of the universe from our earth! Before going deep into the universe, we should have a basic knowledge of it. The universe is simply built with empty space and time, lots and lots of matter, and a constant amount of energy found in different forms (EM waves, light, heat, and dark energy). How did we reach the present status of the universe? Among many theories, the Big Bang theory is the most popular one explaining how the universe came into its current state of existence.

Credits: ESA/Hubble

The Big Bang Theory explains how the universe evolved from the initial point of singularity, i.e., a point of high density and temperature. According to the theory, this singularity point bursts into a big bang, creating the universe. As time passes, it starts expanding and cooling, creating the possible matter that we see today. Still, this is just a theory, and nothing has yet been confirmed to be exactly the correct origin of the universe. On an elementary level, one should be aware of these ideas about the Big Bang theory. Accurate derivations require a general theory of relativity, which is beyond the scope of this post. But still, there are some misconceptions about this big bang theory. The Big Bang Theory just predicts how the universe came to its current status from its initial state of singularity. It does not tell anything about how energy, matter, and time came into existence. This theory just helps in describing the size of the universe, not the universe as a whole.

Space & Time

What is space? What is Time ? What is space-time?

 

Space is a quantity representing the three dimensions in the universe; it is usually the x, y, and z axes. The position of any object in the universe can be represented using these three coordinates by fixing a frame of reference. In the given image below, any point in space can be represented using a 3D coordinate system by using a frame of reference. We usually use the vector notation to represent any point in space. We will deal with the Vectors in detail in upcoming posts. So in the below diagram, the position of the given point with respect to the given frame is 5i + 3j + 4k, all distances measured in cm. 

Time is a one-dimensional unit defined as the progression of events from the past to the present, then to the future. It is measured in units called seconds. According to physics, one second is defined as the time taken during the 9,192,631,770 periods of radiation produced by the transition between two levels of the cesium-133 atom. Both Space and Time came into existence after the big bang occurred. There was no space or time before that.

 

Space-time is a mathematical model that combines the space, a 3-dimensional quantity, and the time, a 1-dimensional quantity, into a single four-dimensional manifold. The space-time model is mainly used to find relativistic effects and explain why different observers perceive events in different spatial and temporal coordinates. We will talk more about the General Theory of Relativity in upcoming posts.

Matter & Energy

By definition, matter is anything that has mass and occupies some volume in space. For example, the pen, chair, and air are all examples of matters. Mass is usually measured in g and kg. Energy, by definition, is regarded as the capacity to do work. E.g., kinetic, potential, heat, and light are some forms of energy in the universe. Energy is usually measured in Joules (Newton meter). Mass and energy are interrelated by Einstein's famous mass-energy equivalence formula.

 

E = m(c^2), where c is a constant equal to the speed of light.

 

Whenever an object of mass M disintegrates into two different masses, m1 and m2, By General relativity in combination with conservation of momentum, we can prove that M > m1 + m2 (proof will be dealt with in later posts). Where did the rest of the mass go? The rest of the mass is converted into energy E =  { M - (m1+m2) c^2.

 

So, this post gives you a very basic and strong understanding of what space, time, mass, and energy are. You would also have gotten the basic idea behind the Big Bang Theory. I hope you have gotten a basic understanding of the basic entities in the universe. This is just a start; we will deal more with stars, galaxies, and other stuff about the universe in the upcoming posts.