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A map of the UniverseA map of the Universe The Universe consists of everything that we know to exist: stars, planets, rocks, people, and so on. It even includes empty space. Nearly all the visible matter in the Universe is contained in galaxies. About 100 billion galaxies are grouped into giant clouds, called superclusters, spread out like a net. The “holes” between them are vast empty spaces, known as voids. The Universe probably began life in a hot, dense explosion called the Big Bang, which took place about 13.7 billion years ago.

Proxima CentauriProxima Centauri

Light years

The Universe is unimaginably vast: billions upon billions of kilometres wide. Distances in it are so great that a special measure is needed to record them. This is a light year, or the distance that light, which moves at a speed of 299,792,458 metres per second (186,282 mph), travels in one year: about 9,460,528,405,000 kilometres or about 6 trillion miles (6 followed by 12 noughts). The nearest star to Earth after the Sun, Proxima Centauri, is 4.2 light years away. The most distant objects we know in the Universe are more than 13 billion light years away.


The Universe is estimated to be 13.7 billion years old.

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