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The Expanding Universe How big is the universe?. So, imagine the Sun is the size of this classroom. That makes the Earth about the size of a grapefruit! Got that? And just for comparison a grain of salt on the same scale would cover the whole of the UK!. Earth. U.K. Salt.
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The Expanding Universe How big is the universe?
So, imagine the Sun is the size of this classroom. That makes the Earth about the size of a grapefruit! Got that? And just for comparison a grain of salt on the same scale would cover the whole of the UK! Earth U.K. Salt
Now, imagine that the complete Solar System is the size of this classroom. The Sun is now the size of a grain of salt! The Earth’s orbit around it would be the same size as a CD. Good - something you can actually see! But the Earth itself? As big as a microscopic bacterium!! Sun Salt Earth’s orbit
Now, imagine that our galaxy is the size of this classroom. It is called the Milky Way and contains about 100 billion stars (that’s 100,000,000,000 stars). The Solar System is now the size of a grain of salt! (A very small grain!) For light (the fastest thing there is) to travel across the Milky Way, it takes 160,000 years... Solar System Salt …This is what human beings looked like 160,000 years ago!
Our galaxy Now, imagine that our galaxy is size of one penny. How big is our local supercluster of galaxies (there are only about a dozen galaxies in that)? That’s right - about the size of this classroom. Light takes about 130 million years to get across it... …And guess who was around about 130 million years ago!
And finally the universe … make it the size of the classroom and our local supercluster (with its dozen galaxies) would be the size of a shirt button.
Mark some galaxies on the surface with a felt tip pen. On our balloon our pen galaxies are about 3 cm apart. Click here to play video Scientists think of space as the surface of a sphere. You can think of it as a balloon!
But the universe is getting bigger every day. Everything is spreading further and further apart. Blow into our balloon universe… it gets bigger and our galaxies are now 4 cm apart. Click here to play video Scientists can estimate how fast the real universe is expanding by looking at light reaching us from distant galaxies. The speed the furthest galaxies are moving away from us? It’s about 1.7 million million kilometres per second!