• Question: What evidence supports the Big Bang theory and why is it that earth is habitable but other planets don't have the same climate, even though the Big Bang theory made the whole universe at once?

    Asked by to Edward, Ian, Mathew, Naomi on 25 Jun 2014. This question was also asked by .
    • Photo: Ian Stephenson

      Ian Stephenson answered on 25 Jun 2014:

      To answer the second part, how do you know that no other planets are habitable?

      The ones in our solar system are either too hot or too cold, simply because of their distance from the sun, but in the last few years we’ve found loads of exo-planets: planets around other stars.

      One of the unknowns in the Drake equation (which calculates the probability of aliens) is how common are planets, and we once thought they might be pretty rare, but now its looking like they’re pretty much everywhere.

      We’ve not yet identified one that is definitely in the “goldilocks” zone (not too hot and not too cold), but we’ve found lots of potential candidates, and I’m pretty sure we’ll find suitable planets in the next 10 years or so.

    • Photo: Naomi Osborne

      Naomi Osborne answered on 25 Jun 2014:

      The only evidence we have for the big bang theory is cosmic microwave radiation – thermal radiation that was detected in the 1960s that can only be explained by a massive explosion. You can read about it on the BBC’s website http://www.bbc.co.uk/science/space/universe/sights/cosmic_microwave_background_radiation

      The reason Earth has a climate is because after the big bang, it ended up a nice distance from the sun in the habitable zone – not too hot, or not too cold. It’s this constant temperature which keeps gases in our atmosphere from escaping (like it does on Mercury because it’s too hot) or condensing into rocks because it’s too cold (like on Mars). Our atmosphere was formed from gas given off from volcanoes, but has been changed by bacteria and then plants into what it is today. It’s our atmosphere that keeps our climate how it is by trapping heat from the sun.

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