The universe consists of trillions of galaxies. A galaxy contains stars, dust and rocks. These are the things that you can see. These are made up of matter, everything you can see is made up of matter. These things only make up only 5% of all matter in the galaxy. So, you, the trees, the planets, stars, nebulas are pretty rare. Then what do the galaxies contain?
There is something called the Dark Universe that makes up 95% of matter in the galaxy. The Dark universe contains Dark matter and Dark Energy, we’ll look at Dark energy in a future video. Dark matter is invisible to us and is spread everywhere around the galaxy. Now this gets confusing even more, no one has a clue about what dark matter is and how it works. But it’s pretty sure that they are present.
You might wonder if it is invisible, then how it has been found. Dark matter is about 27% of the known Universe and Dark energy makes up 68%. The galaxy as you see is made up of many stars and giant rocks which revolve around each other. If there was no dark matter, then there is no reason why these should just fly away instead of staying inside the galaxy. The gravitational force of these bodies isn’t strong enough to hold them in orbit.
Primary evidence for dark matter comes from calculations showing that many galaxies would fly apart, or that they would not have formed or would not move as they do, if they did not contain a large amount of unseen matter. Other lines of evidence include observations in gravitational lensing and in the cosmic microwave background. And that’s why dark matter is needed. It holds these stars, dust and the rocks in the galaxy, preventing it from flying away.
The universe is constantly expanding and it is expanding at a constant rate. There needs to be some energy that is causing the acceleration just like your car needs some energy to accelerate. That’s where Dark Energy comes to play. It plays a major role in the expansion of the universe.
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