• Question: How was water formed on earth in the big bang?

    Asked by 934xmasen24 to Thomas, Saiful, Piers, Meggi, Laurence, Karl, Javier, Chris on 9 Jan 2017.
    • Photo: Chris Eames

      Chris Eames answered on 9 Jan 2017:

      Hi, thanks for the interesting question!

      So first of all the earth was not formed in the big bang. The big bang was 13 billion years ago. After that it took around 400’000 years for the first hydrogen atoms to form. These then formed stars and underwent nuclear fusion to form helium. Some of the bigger stars used their fuel up quickly and collapsed to go supernova. In the supernova light atoms were stuck together to form the heavier atoms like oxygen and iron that make rocks. These heavy atoms were fired across the universe and some were caught up in the cloud of gas that was in the process of forming our sun.

      Not all of the atoms in this gas cloud made the sun. Some also lumped together to make the planets. The earth is just over 4 billion years old. In that 4 billion years the earth cooled and formed a hard surface.

      So where did the water on the surface of the earth come from – if it was a hot ball of rock to start with the water would just boil off right? For a long time this theory was the most widely accepted. The water would then have come from icy comets and meteorites which would hit the earth and deposit all the water on the surface. However, recently it was discovered that the water had been there right from the start and didn’t boil off http://news.nationalgeographic.com/news/2014/10/141030-starstruck-earth-water-origin-vesta-science/

      Anyway, the best thing to take away is that you and all of us are literally made out of star dust.

    • Photo: Karl Byrne

      Karl Byrne answered on 24 Jan 2017:

      Really good question! The Big Bang happened about 13,500,000,000 years ago. The earth didn’t form until 4,500,000,000 years ago. The universe was over 9 Billion years old before the sun and earth formed! Scientists use to think that the water on earths surface came mostly from comets (in the early days of the solar system there were a lot of comets and asteroids banging into each other and hitting the young planets). , although now they aren’t so sure- Results from the Rosetta comet mission last year show that comet water isn’t quite the same as water here on earth. This is what science is all about. Having an idea, testing it and, if it’s wrong, coming up with a new, better idea that fits the facts.


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