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Our Universe: Understanding bit by bit

Our Universe

The universe is where everything exists. From us to stars to particles hanging just around you. So we are in the universe.
The Earth is pretty small when we compare it to Jupiter. Jupiter is pretty small compared to the Sun. As we go on, there are millions of suns in our galaxy and thousands of galaxies in the universe. No one really knows how many. There are some scientists and mathematicians with theories, but nobody really knows. We have discovered a few things and you can check them out in the related links.

How the universe came to existence?

Exactly, nobody knows how the universe came to existence. However, scientists believe that it all started with a BIG BANG.

What is Big Bang?

Scientists believe on idea that the universe started with all of the mass in one big ball, billions of years ago. One day we suppose, that ball exploded. From that moment, time as we measure it began. The moment when this big ball exploded is called the big bang. The idea discussing the explosion is called the Big Bang Theory.

What is Big Bang Theory?

It’s hard to know exactly why this event happened, but what we do know is that this explosive event started with a ‘Big Bang’ and burst of energy that was extremely hot. 1,800 trillion trillion degrees to be more precise. That is an extremely hot explosion. Within less than 1 second, the universe was born, and has been expending and getting colder and colder by the minute. So the Big Bang is in fact. Well! Because of the Big Bang, the universe was made, and it’s continuing to expend ever since.

After the explosion, all of the dust and pieces began to spread out. As time passed, small pieces attracted other pieces and objects began to form. Eventually there were stars, systems, and galaxies. The important thing to remember is that this is an idea. We weren't there, we don't have pictures. The evidence we do have is indirect evidence. We look at the universe around us and our measurements have led us to this current conclusion.

What led to the formation of objects in the universe?

Force of Gravity

Gravity or Gravitational Force exists when one object attracts another. Every object in the universe that has mass has a gravitational force. So basically molecules of one object attract the molecules of another object.

On earth, we don’t fly on earth is because of earth’s gravitational force. Earth’s connection to moon through this force makes the tides rise and fall in the ocean. Similarly, the Sun attracts earth and that’s why, it keeps orbiting. When the earth spins and gravity pulls on the clouds, weather can be affected.

The Earth always has the same pull on every object. It doesn’t matter if we throw an iron ball weighing 50 kg or a piece of paper from a building, it will fall at the same speed. But how come piece of paper falls slowly? It is because the air is in the way. If we drop a piece of paper in a container with no air (a vacuum), it would drop as fast as an iron ball.

How Solar System was formed?

About 4.6 billion years ago, as the theory goes, the location of today's Solar System was nothing more than a loose collection of gas and dust—what we call a nebula. (Orion's Nebula is one of the most famous examples you can see in the night sky.)

Then something happened that triggered a pressure change in the center of the cloud, scientists say. Perhaps it was a supernova exploding nearby, or a passing star changing the gravity. Whatever the change, however, the cloud collapsed and created a disc of material, according to NASA.

The center of this disc saw a great increase in pressure that eventually was so powerful that hydrogen atoms loosely floating in the cloud began to come into contact. Eventually, they fused and produced helium, kickstarting the formation of the Sun.

The Sun was a hungry youngster—it ate up 99% of what was swirling around, NASA says—but this still left 1% of the disc available for other things. And this is where planet formation began.


Galaxies are huge collections of matter, possibly dark matter, dust, gases and of course stars, that are all bound together by gravity. All of these things are required to create planets, planets that also make up all galaxies. All of these things are vital in making up galaxies. There are many different types of galaxies, and many different shapes and sizes of these galaxies.

The sizes of galaxies range from a few thousand light years across, which would be a small dwarf galaxy, to the biggest of about 300 thousand light years across.

The smallest galaxies would have about 10 or 20 million stars in them, with the biggest about 5 hundred to 1 thousand billion.

  • Elliptical Galaxies: Are ball or oval shape galaxies that are not very bright or colorful.
  • Spiral Galaxies: Are disc shaped galaxies with spiral arms.
  • Irregular Galaxies: Are galaxies that have no regular shape or form. These are small galaxies that contain newly formed stars.

Galaxies continue to be formed and grow. This happens through collisions and mergers. 

Most clusters contain thousands of galaxies. One of the smaller type clusters contains our galaxy. The Milky Way. This small cluster is called the ‘Local Group’ that contains around 40 galaxies only.

So while these galaxies have millions of stars, that’s a pretty small spec of an area in our universe.

Milky Way

The Milky Way galaxy is a disc shaped spiral galaxy with a huge collection of stars, about 100-400 billion. We don’t know exactly, but we know it’s over 200 billion. But compared to other galaxies and star clusters The Milky Way is small.

Solar System

About 4.6 billion years ago, way after The Big Bang happened and started to create gases and stars, the solar system began to form. So 9 billion years after the beginning of time our solar system was created. Several planets and a number of objects that orbit around our sun make up the solar system.

There are 8 planets in the solar system that orbit the sun. 160 moons orbit the 8 planets and 5 dwarf planets.

The 5 dwarf planets are called

  1. Ceres
  2. Haumea
  3. Makemake
  4. Eris
  5. Pluto

Pluto was once classed as a planet, but is now classed as a dwarf planet.

The 8 planets that orbit the sun in our solar system in order starting from the sun are:

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Jupiter
  6. Saturn
  7. Uranus
  8. Neptune

First 4 planets that are closest to the sun are Terrestrial Planets, meaning that they are rocky in formation. This includes Earth. It also means that the planets have or may have had some form of water on their surface.

Second 4 planets that are furthest from the sun are Jovian Planets, meaning that they are large gas planets with little to no real surface. These planets are made up of huge balls of different types of gases.

Sizes of Planets:

  1. Jupiter (43,441 miles) – 1,120% the size of Earth
  2. Saturn (36,184 miles) – 945% the size of Earth
  3. Uranus (15,759 miles) – 400% the size of Earth
  4. Neptune (15,299 miles) – 388% the size of Earth
  5. Earth (3,959 miles)
  6. Venus (3,761 miles) – 95% the size of Earth
  7. Mars (2,460 miles) – 53% the size of Earth
  8. Mercury (1,516 miles) – 38% the size of Earth

Asteroid Belts

Asteroids are made up of rock and metal for the most part, and in different areas of our solar system made up of ice and other materials. In our solar system there are two belts of asteroids that orbit our sun. The belts are made up of materials left over from when the planets were formed.

Asteroid Belt

This is the remains of a planet between Mars and Jupiter that failed to fully form.

Kuiper Belt

‘The Kuiper Belt’ is about 4 billion miles away from the sun!

Billions of asteroids make up both of these belts that are in our solar system.


The asteroids that move out of their orbit and end up crashed on Earth are called ‘Meteorites’

These meteorites are mostly made up of rock and iron.

There is a theory that life started on Earth due to a meteorite crash. A meteorite was discovered crashed on Earth from somewhere in the solar system. Traces of Amino Acids were found that are the building blocks for forming proteins. In turn proteins make up life.  


In a way, both Meteorites and Comets seem similar. As they both orbit sun and made up of leftover materials when the solar system was created but they are different in one aspect.

Asteroids are mostly made up of rock’s and metals, and while comets can be made up of different rocks, they also have different materials in them like ice and dust.

The Rosetta – Philae was the first successful mission to land a space craft onto a comet.


Exoplanets are planets that are found outside of the solar system. There are over 1,000 planets that have been discovered outside of our solar system; these planets are all different types and sizes. Some of these planets are in our galaxy and some of them are further afield in different galaxies.

Why we are interested in Mars?

Mars’s orbit around the sun is the 4th fastest orbit of all the solar system planets. Mars is red in color and is very cold. Not the coldest of planets in the solar system but very cold all the same. The temperature on Mars is on average -80 degrees, and can get a lot colder at times.

At times in the summer near the Mars can reach 70 degrees. However the atmosphere is very thin with carbon dioxide over 95%. Mars orbits the sun in 687 days, which means 1 Earth year on Mars is 687 days.


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