• Question: how big is the galaxy compared to the earth?

    Asked by abbynliz to Iain, Jo, Leo on 24 Jun 2010 in Categories: .
    • Photo: Leo Garcia

      Leo Garcia answered on 24 Jun 2010:

      The galaxy in which we live, called the ‘Milky Way’, is around 100,000 light years in diameter. Remember that a light year is a unit of distance, not time – it is the distance light travels in a year. So 100,000 light years is about 9×10^17 km – which is 9 with 17 zeroes after it kilometres. Huge.

      The earth is about 13,000 km in diameter – so you could fit around 6×10^13 earths side by side from one end of the Milky Way to the other. It’s a bit of a back of the envelope kind of calculation, but the real answer will be on that kind of scale – which is truly massive…