universe

The Universe contains everything that exists, including you, the stars, the galaxies and even time itself. It is mostly empty space, with clumps of stars and gas separated by huge amounts of nothingness. In between the galaxies and clusters of galaxies, you would have to travel a very long way to find even a tiny bit of dust. The distances between these galaxies and clusters are getting bigger all the time because the Universe is getting bigger. Astronomers think that the Universe is about 15 billion years old.
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The Size of the Universe
We don’t know how big the Universe really is because we can’t see all the way to the edge of it. This is because light takes a long time to travel from very far off galaxies. The Universe is only 15,000,000,000 years old, which sounds like a long time but isn’t long enough for the light from some very far off galaxies to have reached us yet. Looking at the light from distant stars is like looking back in time. If you look up at a star, the light that you see left that star millions of years ago. You are seeing the star as it looked then, not as it looks now. You would have to wait another few million years for the light that is leaving the star today to travel all the way through space to Earth before you could see how the star looks now.