The Universe

The Universe

The Universe consists of everything that exists, everywhere. It includes objects such as stars, planets, moon, vast dust clouds and almost endless stretches of empty space.

It is difficult to imagine the idea of the Universe as ‘everything’. ‘Everything’ includes all objects made of matter - from the largest stars and planets to the smallest particles, atoms, and molecules. But ‘everything’ also includes all forms of energy - from heat and light to microwaves and X-rays. However, most of the Universe is empty. This emptiness is called ‘deep space’.

The Big Bang
The Universe is probably 13.7 billion (13700 million) years old. Scientists think it began as a gigantic explosion called the Big Bang. Time began with the Big Bang and matter started to form. Space expanded and became bigger. Today, scientists believe the Universe is trillion and trillions of kilometers (93 billion light years) from one side to the other, and is still getting bigger.

The Dark side
Because of the way the Universe is expanding, we know approximately how much matter and energy it should contain. However, we can only detect less than one-tenth of this. The rest is known as ‘dark matter’ and ‘dark energy’.

Fascinating Facts
• What is outside the Universe?
It is believed that the Universe contains all time and space. If the Universe is everything, it cannot have an outside. As the Universe expands, objects in it move further and further apart. However, this does not mean that they are ‘outside’ the Universe.

• What was there before the Universe?
It’s thought that time itself began at the Big Bang, when the Universe started. So there was no ‘before’.