My daughter wants to know....

[I_am_not_mafia]

Ultimately, we don't know where the energy of the big bang came from or if it even had to come from anywhere. But - it wasn't an explosion, it was more like akin to a vessel of hot water expanding and cooling, and in the course of that, the water condenses and complexice crystals and snow flakes form.  The cooling atoms fused together to form more and more complex matter.

I read this to her. Her question is:

How do we have any proof that this happened?

I think the snowflake analogy is an excellent one, because it's something that we can see for ourselves and can even create on demand if we want. Snowflakes can have some really complex structures (google pictures of them) yet no one seriously thinks that they were all designed. They formed merely because of water and a dust nuclei dropping out of the sky at the right temperatures.

But because they're static structures people don't think of snowflakes as anything particularly interesting. But they do change shape as the temperature changes. If you change the temperature slowly over time, the ice will re-crystalise and change shape as long as the temperature does not rise above freezing. A similar process happens within the Earth and gives us metamorphic rock. These things happen at the edge of chaos. Not too much energy so that everything blows apart, melts or becomes chaotic, but not too little so that everything is static.

When someone asks for proof, they also need to be ready to understand the evidence otherwise they're making an impossible demand. Not everything in life is simple. Making a snow flake is a relatively simple process, but something like life is far more complex. But that doesn't mean to say that we can't understand it, it just requires more time and knowledge.

This then leads on to the scientific method, how it works by collecting data, creating falsifiable hypotheses, testing them, seeing whether it is consistent with what else we know and if necessary re-evaluating what we think we know. And over time, we come up with theories that not only have explanatory power but are also useful. The theory of evolution doesn't just explain how we evolved, we can also use it for practical purposes, like using genetic algorithms for producing aerofoils for example, or gene therapy etc. If the theory was wrong, we wouldn't be able to use it.